New Tools for the Management of Fungal Pathogens in Extensive Cropping Systems for Friendly Environments

Abstract Crop production plays a critical role in global food security, with key commodities such as corn, wheat, soybean, and rice ranking among the most widely cultivated crops. These major crops are predominantly grown within extensive cropping systems. However, these systems are threatened by fungal diseases, which may cause substantial yield reductions. The most widely adopted strategy to manage fungal pathogens in extensively grown crops worldwide is chemical control. Nevertheless, this strategy has multiple drawbacks and potential hazards, including pathogen resistance, environmental contamination, and negative effects on human health and other organisms. As a logical result, over the last decades, conventional agricultural systems have been questioned and a transition toward more sustainable production methods has emerged. The new productive paradigm emphasizes the adoption of eco-friendly approaches to disease management, with biofungicides and biostimulants among the new tools gaining popularity. However, establishing a regulatory framework for these tools in different countries has proven challenging due to the lack of global harmonization. The primary objective of this review is to gather dispersed information on new tools and technologies (either available in the market or being studied) applicable to extensively grown crops generated by the latest scientific advances. Additionally, the review seeks to contribute to clarifying the categorization of these new tools (biostimulants, biofungicides, plant defense inducers, and technologies such as gene editing, RNAi, nanotechnology, and physical treatment) to enhance their understanding and to critically assess their potentials, challenges, and future perspectives. Furthermore, the review aims to identify tools successfully implemented in horticulture or other intensive production systems but not yet practically applied in extensively grown crops, to pave the way for future advances and potential adaptations of these tools to suit extensive agricultural practices. Finally, this review presents a practical disease management model that incorporates new tools to address a key disease in wheat. Graphical Abstract


I. Introduction
Crop production plays a critical role in determining global food security, with corn, wheat, soybean and rice ranking among the most extensively cultivated commodities worldwide (Chaloner et al., 2021;Richard et al., 2022).These major commodity crops are produced primarily under extensive cropping systems i.e., large-scale commodity farming characterized by the large-scale production of summer crops (such as soybean, corn, sunflower, and grain sorghum) or winter crops (such as wheat, barley, and rapeseed) with limited inputs like fertilizers and irrigation.Both the yield and product quality of these crops can be affected by either abiotic (i.e., low, or high temperature, deficient or excessive water) or biotic factors (i.e., diseases, pests, or weeds).Among biotic factors, infectious diseases (caused by fungi, fungal-like organisms, bacteria, phytoplasmas, viruses, viroids, nematodes, and parasitic higher plants) have been estimated to cause significant yield reductions, ranging between 20 and 40%, even in cases where crop protection measures are used (Richard et al., 2022).Numerous strategies have been used to prevent diseases including chemical control, which is the most widely adopted in extensive cropping systems due to its effectiveness and viability.This strategy has several drawbacks and potential hazards, including loss of sensitivity or development of pathogen resistance, environmental degradation due to contamination, negative effects on human health, depletion of beneficial microorganisms and reduction in biodiversity within plant-associated habitats (Fenibo et al., 2021;Almoneafy et al., 2022;Lahlali et al., 2022).Over the past two decades, the prevalent conventional agricultural system, which emerged after the Green Revolution in the 1960s and is characterized by the use of high-yielding cultivars, monoculture practices suitable for mechanization, and reliance on intensive inputs (fertilizers, fungicides, herbicides, and irrigation, has come under scrutiny, and faces extensive questioning while transitioning to more sustainable, holistic and future-oriented production systems (Maitra et al., 2021;Feldmann et al., 2022;Richard et al., 2022).The paradigm shift in production systems worldwide, driven not only by environmental concerns but also by a remarkable increase in consumer demand for organic foods, has fueled the need for sustainable agricultural practices (Rocha et al., 2019;Lahlali et al., 2022;Gupta et al., 2023).The new paradigm embraces 'green agriculture' as a collection of farming practices aimed at sustaining farm productivity and profitability in a sustainable manner (Maitra et al., 2021;Feldmann et al., 2022).This highlights the importance of Integrated Disease Management, which involves the use of mechanical, physical, and natural disease control methods, with chemical control used judiciously, as a fundamental approach to crop protection (Ons et al., 2020;Richard et al., 2022).Eco-friendly approaches for disease management purposes including new tools such as biopesticides and biostimulants with protective effects are gaining increasing popularity.Thus, and considering the lack of a regulatory framework regarding this issue, numerous countries are developing regulations to govern the production and use of these products, prioritizing safety and effectiveness (Maitra et al., 2021;Gupta et al., 2023).Some of these tools are particularly attractive for their low mammalian toxicity, short environmental persistence, low mobility in the soil, lack of residues in food, low application rate and complex chemistry that do not develop resistance in pests (Feldmann and Carstensen, 2018;Caradonia et al., 2019;Abubakar et al., 2020;Dimki� c et al., 2022;Feldmann et al., 2022).
The term 'new tools' refers to a range of products, microorganisms or molecules that fall under the umbrella of biofungicides, plant defense inducers, biostimulants with protective effects, and similar categories.The term also includes various technologies such as gene editing, RNAi-based tools, nanotechnology, and physical treatments like cold plasmas.Some of them are relatively new, and both research and industrial procedures for their development are in their early stages, whereas others, like macro-and micronutrition, may not be entirely novel but, if used consciously, could be used for the management of diseases in extensively grown crops.While many of these new tools are being used in intensive farming and organic production systems, their use in extensive cropping systems is still quite limited.Besides, research in this field tends to be fragmented, leading to very complex and occasional contradictory results.Several questions arise in this context: What are the available tools to effectively manage diseases in sustainable extensive cropping?How efficient are these tools to mitigate the impact of diseases?What are the shortcomings that limit their full usage and potential effectiveness?, and How could they integrate and complement the current traditional protection measures?Accordingly, the primary objective of this review is to gather the dispersed information about new tools for disease management in extensively grown crops, with special focus on fungal diseases.It highlights the latest scientific advances generated and collects the challenges for their large-scale use, paving the way for future advances and potential adaptations to suit extensive agricultural practices.Furthermore, it seeks to reassess the role of nutrition as a crucial tool for disease management.Finally, the review also presents a practical disease management model that incorporates new tools to address a key disease in wheat.

II. Current state of research of new tools to manage diseases in extensively grown crops
This section examines tools that have been explored at the field or lab level and have demonstrated potential to combat specific pathogens commonly associated with extensively grown crops, grouped according to their functionalities concerning the plant, while also considering the regulatory aspect.

A. Biofungicides
Biofungicides are a subclass of biopesticides based on organisms that restrict the growth of phytopathogens, composed mainly of the following two categories: (i) microbial-derived biofungicides, further divided into classical biological control (involving single bacteria or fungi), consortium (involving the synergism of a group of microorganisms), and microbial metabolites, and (ii) plant-derived biofungicides, i.e., naturally occurring substances, mainly phytochemicals (Abubakar et al., 2020;Fenibo et al., 2021;Lahlali et al., 2022).Numerous studies have focused on investigating biological control as well as a wide variety of bioactive compounds as agricultural bioweapons against pathogens.The results of these studies are documented in Table S1 (see Supplemental material).

Microbial-derived biofungicides
This approach encompasses microorganisms such as bacteria, fungi, or viruses, collectively referred to as 'biological control agents' (BCAs), due to their ability to use antagonistic strategies against phytopathogens (Lahlali et al., 2022).BCAs are applied in the disease management of plant pathogens, acting via a variety of different direct and indirect mechanisms.Their direct mode of action encompasses antagonistic effects against pathogens, primarily through antibiosis (achieved by producing toxic metabolites and degrading enzymes), parasitism, and competition for resources and space (for example, through the production of siderophores), while indirect mechanisms involve inducing plant resistance and soil suppressiveness (Lahlali et al., 2022;Win et al., 2022).

Classical biological control.
Bacteria have demonstrated to be efficient BCAs due to their ability to produce a range of antimicrobial compounds (e.g., antibiotics, endotoxins, bacteriocins, siderophores, hydrolytic enzymes, and hydrogen cyanide), which can effectively eliminate pathogens, thus preventing disease development.Specifically, bacterial species of the genera Bacillus and Pseudomonas have been used as biological BCAs against soilborne fungi, based on their ability to colonize the rhizosphere, while also being able to enter the root and establish inside endophytically (Dimki� c et al., 2022;Win et al., 2022;Zakaria et al., 2023).The remarkable characteristics of the genus Bacillus (which includes examples like B. (Continued) subtilis and B. amyloliquefaciens) encompass safety, adaptability to challenging conditions, biofilm-forming capacity, and ability to synthesize a diverse array of antimicrobial compounds (Table 1).The genus Pseudomonas has also been extensively researched for its production of bioactive secondary metabolites and includes species like P. fluorescens and P. chlororaphis, with demonstrated biocontrol abilities (Table 1).Both Bacillus and Pseudomonas produce siderophores, which provides the strains with the ability to sequester the Fe 3þ available in the rhizosphere, rendering this nutrient unavailable to phytopathogens (Dimki� c et al., 2022).These microorganisms are also able to compete effectively with pathogens for nutrients and space, while also having effects on the defense responses of host plants (Dimki� c et al., 2022).As examples, B. velezensis can successfully control the rice blast caused by the fungus Magnaporthe oryzae (Borriss et al., 2019;Omoboye et al., 2019), P. synxantha can effectively control wheat pathogens like Gaeumannomyces graminis var.tritici, Rhizoctonia solani, Sclerotinia sclerotiorum, Fusarium culmorum, F. pseudograminearum, and Pythium ultimum, mainly through the production of phenazine (Zhang et al., 2020), and Bacillus and Pseudomonas species isolated from the phylloplane and the rhizoplane of corn, oat, soybean, and wheat are efficient in decreasing the severity of the soybean Asian rust produced by Phakopsora pachyrhizi (Twizeyimana et al., 2023).Another example is that of the myxobacterium Myxococcus xanthus, which has been recently demonstrated to be significantly efficient in controlling Zymoseptoria tritici in wheat (Eisner et al., 2023).Among fungi, Trichoderma is by far the most studied genus of BCAs, with many species like T. harzianum and T. virens being extensively commercialized as biopesticides against various pathogenic fungi that cause soilborne, foliar, and post-harvest diseases (Lahlali et al., 2022;Agostini et al., 2023).These fungi are renowned for their strong competitive ability against phytopathogens, thanks to their efficient siderophores that chelate iron and their ability to derive ATP from widespread polymers present in the environment such as cellulose, glucan, and chitin (Table 1).Moreover, they can act as parasites on other fungi and nematodes, and inhibit the colonization of competing microorganisms through antibiosis, exhibiting the ability to produce both volatile and nonvolatile toxic metabolites like harzianic acid, tricholin, peptaibols, viridin, and gliovirin (Zaidi and Singh, 2017;Agostini et al., 2023).As an example of the successful use of Trichoderma in extensively grown crops, Pimentel et al. (2022) treated soybean seeds with T. afroharzianum alone or in combination with strains of T. hamatum and obtained protection for seedlings against Pythium spp.infection.In addition, Conte et al. (2022) applied Trichoderma spp. to the soil, achieving reduced incidence of S. sclerotiorum in  (Modrzewska et al., 2022).In a study using T. harzianum in wheat plants to control F. graminearum and F. verticillioides (the causal agents of Fusarium ear rot), Woo and Pepe (2018) demonstrated the ability of Trichoderma to induce priming in plants by triggering a preparatory response against pathogen attacks and the anticipatory establishment of systemic resistance.The results of this study revealed that the fungus can modulate the expression patterns of systemic defense response genes in wheat plants, thereby enhancing the plant tolerance to the disease (Ferrigo et al., 2020).Among viruses, mycoviruses constitute a category that selectively infect fungi, generally causing subtle modifications to their hosts, yet being able to induce either hypo-or hyper-virulence effects.Notably, when mycoviruses trigger hypovirulence in fungal plant pathogens like F. graminearum and S. sclerotiorum, as evidenced in several studies (Garc� ıa-Pedrajas et al., 2019; T. Gupta et al., 2019;P. Li et al., 2015;Pedersen and Marzano, 2023), they emerge as potential agents for biological control.Despite the great advances in the identification and characterization of mycoviruses, the translation into practical technologies or formulations suitable for field application represents a significant obstacle.The ongoing exploration for novel mycoviruses and a deeper understanding of the intricate population biology that governs the interactions between these mycoviruses and their fungal hosts are critical areas of further exploration (Abid et al., 2018).
A summary of the main distinctive characteristics of the bacterial genera Bacillus and Pseudomonas and the fungal genus Trichoderma, which are the most prominent organisms used for biological control (Table 1).

Consortium.
Due to the heterogeneity of soils and the coexistence of diverse pathogens in each crop, the use of a single BCA can often become ineffective, mainly due to inadequate colonization on the host rhizosphere.To improve control efficiency, several authors have proposed combinations of two or more strains of microorganisms (consortia) (Kumar et al., 2018;Woo and Pepe, 2018;Niu et al., 2020) based on the idea that they may act synergistically (Ram et al., 2022;Maciag et al., 2023).A prime illustration of microbial consortia is found in 'suppressive soils,' characterized by their ability to suppress soilborne plant diseases, such as take-all disease in wheat caused by G. graminis var.tritici, due to the inhibitory action of phenols produced by bacteria (Niu et al., 2020).Recent studies have emphasized the idea of designing synthetic consortia to enhance biological control activity against specific pathogens, thus mimicking the microbial networks observed in native suppressive soils, where beneficial microbial groups positively impact soil fertility and effectively control pathogens on a large scale (Czajkowski et al., 2020).The coinoculation of seeds, plants, or soils with different bacterial strains, or bacteria combined with fungi, is nowadays being considered among the most promising technologies in green agriculture (Poveda and Eugui, 2022).Examples of success include a consortium of species of Pseudomonas effectively suppressing the take-all disease in wheat, T. harzianum þ T. virens controlling Colletotrichum truncatum in soybean, T. viride þ P. fluorescens controlling R. solani in rice (Ram et al., 2022), and T. hamatum þ T. afroharzianum controlling damping-off and root rot produced by Pythium spp. in soybean (Pimentel et al., 2022).Also, by using a synthetically constructed bacterial consortium composed of microbiota of corn roots, Niu et al. (2017) reduced the severity of the corn seedling blight caused by F. verticillioides.Also, a recent study demonstrated that the co-colonization of wheat roots with the bacteria Streptomyces viridosporus along with mycorrhizal fungi can synergistically upregulate the expression of polyphenol biosynthesis genes in wheat plants, thus inducing resistance to the stripe rust caused by Puccinia striiformis f. sp.tritici (Rashad, 2023).While numerous studies have evaluated single BCAs to control some important pathogens in extensively grown crops, only a few have assessed consortia of BCAs and their biological action against fungal pathogens with confirmed fungicide resistance, highlighting the need for comprehensive investigations to explore their potential synergistic effects.

Microbial metabolites.
Among bacteria, endophytic and nonendophytic actinomycetes, mainly represented by the genus Streptomyces, are known for their ability to produce a wide variety of secondary metabolites, including antibiotics (like blasticidin, mildiomycin, natamycin, validamycin, and kasugamycin), antifungal compounds, and plant growth regulators, which makes them a valuable tool for biological control (Santra and Banerjee, 2020;Maitra et al., 2021;Dimki� c et al., 2022).One successful example is the ability of Streptomyces albulus var.wuyiensis to produce wuyiencin, which is effective against S. sclerotiorum in soybean (Yang et al., 2022).Bacteria also produce and release a wide range of volatile organic compounds (VOCs), including various chemical classes such as alcohols, ketones, aromatic compounds, terpenes, organic acids, esters, aldehydes, sulfur compounds, alkanes, and nitrogen compounds, with ability to directly target pathogens, particularly those found in the soil.A notable example is the patented soil fumigant PaladinV R , based on dimethyl disulfide, a bacterial VOC (Win et al., 2022).Some Pseudomonas species also produce hydrogen cyanide, which can act as a fungal respiration inhibitor, as demonstrated in the case of Phytophthora infestans (Yu et al., 2022).Fungi also produce antifungal compounds and VOCs, forming the basis of 'mycofumigation,' a promising strategy for plant disease control applicable to seeds, plants, or soil in the fight against plant diseases (Karsli and Sahin, 2021;Mitra et al., 2023).An example of fungal-derived metabolites is found in formulations based on soluble proteins extracted from the fungus Acremonium strictum, commonly known as AsES (Acremonium strictum Elicitor Subtilisin).Field trials conducted by Chalfoun et al. (2018) unveiled the ability of this fungus to reinforce plant defenses against Septoria glycines, Cercospora kikuchii, and C. sojina, exhibiting also considerable efficacy when applied in combination with fungicides.Another example is the innovative product named HowlerV R (Summit Agro), harnessing the potential of AsES, which has been developed and introduced into the Argentine market as a plant defense elicitor, proving to be a valuable tool in disease prevention in soybean cultivation.

Plant-derived biofungicides
Plant-derived fungicides are compounds of natural origin (or exact synthetic analogs), which have active ingredients with proven fungicidal potential.This group includes secondary metabolites like alkaloids, terpenoids, saponins, coumarins, phenolics and polyphenols present in plant-derived extracts and essential oils (Abubakar et al., 2020;Santra and Banerjee, 2020;Fenibo et al., 2021).Plant extracts obtained from various medicinal plants have demonstrated fungicidal effects in vitro against plant pathogens, hindering spore germination, mycelium growth, germ tube elongation, and sporulation, while also inhibiting the synthesis of essential enzymes, DNA, and proteins (Deresa and Diriba, 2023).For instance, methanol extracts from Artemisia indica, Persicaria orientalis, and Clerodendrum indicum have demonstrated fungicidal effects against M. oryzae, the causal agent of blight disease in wheat (Shamim, 2021).Also, crude extracts of Alpinia galangal, Curcuma longa, and Zingiber officinale have shown fungicidal effects against the same fungus causing blight disease in rice (Nabila et al., 2021).The water extracts obtained from Frangula alnus, Zea mays, Aesculus hippocastanum (Findura et al., 2020), Levisticum officinale, Coriandrum sativum, Pinus sylvestris, Satureja hortensis, Lavandula vera and Juniperus communis (Kocira et al. 2020) have been shown to effectively reduce infestation of seeds from different plant species.In addition, Szparaga (2023) and Hara et al. (2018) proved the inhibitory effect of the extracts from Linum usitatissimum, J. communis and Mentha piperita on the growth of Botrytis cinerea and S. sclerotiorum in in vitro tests.Also, sesquiterpenoid compounds isolated from Drimys winteri exhibit fungicidal effects against G. graminis var.tritici, responsible for the take-all disease in wheat (Paz et al., 2020).Another example is the water and methanol extracts from Acalypha wilkesiana, Melia azedarach, and Lantana camara, which display fungicidal effects against P. triticina, the causative agent of wheat leaf rust (Elkhwaga et al., 2018).Furthermore, several plant extracts have been shown to induce structural alterations in hyphae and mycelia, resulting in reduced pathogenicity in mycotoxin-producing fungi like F. verticillioides (Dikhoba et al., 2019;Deresa and Diriba, 2023).Methanolic extracts obtained from the forestry species Blepharocalyx salicifolius and Prosopis nigra also effectively inhibit the in vitro growth of S. glycines and C. kikuchii and mitigate the severity of the corresponding diseases in soybean plants (Sequ� ın et al., 2019(Sequ� ın et al., , 2020)).Essential oils, derived mainly from aromatic plants, are known for their antifungal properties, attributed primarily to constituents like thymol, carvacrol, eugenol, citronellol, geraniol, camphor, and limonene (Santra and Banerjee, 2020).For example, the application of essential oil extracted from Morinda citrifolia to soybean leaves significantly decreases the severity of Asian soybean rust and is effective against anthracnose caused by Colletotrichum truncatum (Pinto e Nose et al., 2022).Essential oils derived from aromatic plants such as Cinnamomum zeylanicum and Origanum vulgare have been demonstrated to function as fungicides against wheat and corn pathogens, specifically F. culmorum and F. graminearum, while also inhibiting the production of mycotoxins (Perczak et al., 2019).

B. Biostimulants with protective effects
Plant biostimulants (PBs) are substances that stimulate plant nutritional processes, regardless of their nutrient content, enhancing one or more of the following characteristics of plants and rhizosphere: (i) nutrient use efficiency, (ii) tolerance to abiotic stresses, (iii) crop quality traits, and (iv) availability of confined nutrients in the soil or rhizosphere (du Jardin, 2015;Caradonia et al., 2019;Feldmann et al., 2022).Brown and Saa (2015) suggested that PBs can reduce the allocation of nutrients to unproductive stress-related processes, optimizing plant energy and resources to enhance crop yield and quality.Several PBs, such as beneficial microorganisms, chitosan, silicon and phosphites, have also protective effects by functioning as either biopesticides or resistance inducers (Kumar et al., 2021;Maitra et al., 2021;Lahlali et al., 2022;Moumni et al., 2023).A promising strategy for crop disease management, which is thought to be able to supplement chemical fungicides, is the application of products involving compounds of natural or inorganic origin capable of triggering innate plant defense responses, thus inducing disease resistance in plants through the activation of Systemic Acquired Resistance (SAR) or Induced Systemic Resistance (ISR) (Iriti and Varoni, 2017;Chalfoun et al., 2018;Carmona et al., 2019).This section is devoted to assessing microbial and nonmicrobial (organic and inorganic) PBs with protective effects.Comprehensive details about the research efforts made to evaluate these tools are presented in Table S2 (see Supplemental material).

Microbial biostimulants with protective effects
Microbial PBs with protective effects, including Plant Growth-Promoting Rhizobacteria (PGPRs), bacterial endosymbionts, and Arbuscular Mycorrhizal Fungi (AMF) enhance plant nutrition through diverse mechanisms and confer protection via direct pathogen antagonism or heightened resistance (du Jardin, 2015; Maitra et al., 2021;Lahlali et al., 2022).Examples of dual-effect PGPRs include B. subtilis, B. polymyxa, P. fluorescens, P. stutzeri, and P. striata, which have been documented as efficient phosphorus solubilizers with proven efficiency as biocontrollers and/or resistance inducers (Anwer, 2017).Recently, Cao et al. (2023) revealed that a B. velezensis strain isolated from the rhizosphere of cucumber plants enhanced corn resistance to the Gibberella stalk rot (produced by F. graminearum) via ISR activation.Endophytic bacteria also possess beneficial effects on the host plant, as demonstrated by Vitorino et al. (2020), who showed the effectiveness of strains of bacterial endosymbionts (Enterobacter sp. and B. cereus) isolated from a palm on the suppression of the disease caused by S. sclerotiorum through the induction of systemic resistance in soybean plants grown from treated seeds.The effects of this kind of bacteria usually surpass those of rhizospheric bacteria due to their distinctive ability to inhabit plants, thereby directly exerting a beneficial influence on plant cells (Afzal et al., 2019;Shen et al., 2019).AMF are well-known for enhancing plant nutrient efficiency, particularly in phosphorus and micronutrient uptake, optimizing water balance, and playing a crucial role in plant defense against bacterial and fungal diseases (du Jardin, 2015; Santra and Banerjee, 2020;Maitra et al., 2021).For instance, Rhizophagus irregularis and R. intraradices have been shown to efficiently reduce the severity of the soybean sudden death syndrome caused by F. virguliforme by inducing the expression of genes related to the plant defense response (Marquez et al., 2019).AMF safeguard plants from diseases by promoting cell wall thickening, effectively preventing pathogen penetration and colonization (du Jardin, 2015; Maitra et al., 2021).Furthermore, AMF have demonstrated fungistatic activity against pathogens that frequently affect crops (Santra and Banerjee, 2020).Some other well-documented examples of AMF with demonstrated effects on the suppression of diseases are Funneliformis mosseae vs. G.graminis var.tritici and R. intraradices vs. F. pseudograminearum in wheat, Glomusintra radices vs. F. verticillioides in corn, Glomus mosseae vs. P. syringae and R. intraradices vs. Macrophomina phaseolina in soybean (Himaya et al., 2021;Spagnoletti et al., 2017Spagnoletti et al., , 2021)).

Nonmicrobial biostimulants with protective effects 2.1. Organic nonmicrobial plant biostimulants.
This group includes active, natural substances such as humic acids, protein hydrolysates and amino acids, seaweed extracts, plant extracts, as well as chitin and chitosan.These compounds are able not only to stimulate plant growth but also to confer plant protection (du Jardin, 2015; Rouphael and Colla, 2020).Seaweed extracts, obtained from macro-and microalgae, contain unusual and complex polysaccharides (e.g., laminarin, alginates, carrageenans) that contribute to plant growth (du Jardin, 2015; Chiaiese et al., 2018) and also have value as biofungicides and plant defense inducers (de Borba et al., 2022;Righini et al., 2022).These extracts target microorganisms by modifying the permeability of their cells, resulting in the leakage of internal macromolecules or disrupting membrane function, which leads to cellular disintegration and eventual cell death (Santra and Banerjee, 2020).Macroalgae extracts are the most used in agriculture, with many commercial products present in the market, mainly based on the brown macroalga Ascophillum nodosum (Yakhin et al., 2017;Rouphael and Colla, 2020).Regarding this, Gunupuru et al. (2019) demonstrated that treating wheat seeds with a combination of an extract of this alga and chitosan not only diminished F. graminearum attack by activating defense genes and enzymes, but also lowered mycotoxin levels in grains.Laminarin, a storage glucan extracted from Laminaria digitata, has been shown to be able to protect and induce resistance in wheat against Z. tritici, through direct antifungal activity and elicitation of plant defense-associated genes (de Borba et al., 2022).PBs containing humic and fulvic acids exert positive influences on plant growth primarily by altering their primary metabolism and enzymatic systems, impacting on cellular processes and secondary metabolism, and enhancing nutrient bioavailability (Rouphael and Colla, 2020).Their protective effect arises from their ability to mitigate the toxic impact of aluminum and heavy metals (da Silva et al., 2021a).Their application to crops has been shown to alter soil microorganisms both within and beyond the rhizosphere, consequently triggering physiological processes that enhance the plant defense mechanisms against pathogens (da Silva et al., 2021b;Gebashe et al., 2021).Research has proved that humic substances influence the bacterial community in rice, linked to plant defense against pathogens (da Silva et al., 2021a).Their application to rice results in increased populations of microorganisms (Chitinophaga and Pseudomonas), which play a key role in biological control (da Silva et al., 2021b;Niu et al., 2020).Furthermore, humic substances inherently comprise elicitor molecules that are recognized by plasma membrane receptors, initiating a signaling cascade that culminates in the transcription of defense genes (Faccin and Di Piero, 2022).Plant-derived protein hydrolysates, comprising amino acids and peptides, serve dual roles, functioning as biostimulants to enhance germination, productivity, and crop quality, while also boosting plant defense mechanisms against pathogens.Their positive effects stem from the stimulation of the plant microbiome, involving alterations in the composition and activity of microbial populations, ultimately improving physiological and developmental processes of crop plants while enhancing resistance to stress factors (Colla et al., 2017;Schmidt et al., 2020).Research on the association between application of protein hydrolysates, the structure and activity of the phyllosphere microbial community, and plant health is still ongoing (Lachhab et al., 2014;Luziatelli et al., 2016).
Chitosan, the product of the deacetylation of cellwall chitin produced by fungi to evade plant chitinases, is a biopolymer with a dual role as both biostimulant and inducer of plant defense mechanisms (du Jardin, 2015; Moumni et al., 2023).Chitosan can act either as a pathogen-associated molecular pattern (PAMP) or a microbe-associated molecular pattern (MAMP), mimicking the plant-pathogen interaction and leading to the activation of defense responses in treated plants (Iriti and Varoni, 2017).It is a promising substance that can be obtained from crustacean shells or fungi (Tarakanov et al., 2021).El-Gamal et al. (2021) showed its potential in crops by demonstrating its antifungal properties and systemic protection against Septoria leaf blotch caused by Z. tritici when applied to wheat as a foliar treatment.The antifungal effectiveness of chitosan has been attributed to several mechanisms including the following: (i) interaction with negatively charged phospholipids in the fungal plasma membrane, leading to increased membrane permeability and cell death; (ii) potential to attract trace elements, thereby depriving fungi of essential nutrients necessary for growth; and (iii) ability to penetrate the fungal cell wall, binding to DNA, and inhibiting mRNA synthesis, thereby disrupting crucial protein and enzyme production.Certain polysaccharides derived from seaweeds (e.g., oligoalginates and carrageenan) and fungi (e.g., tramesan) represent another effective tool to promote seed germination, stimulating seedling growth, and strengthening plant resistance against pathogens in wheat and rice (Zhang et al., 2015;Le Mire et al., 2019;Scala et al., 2020;Moenne and Gonz� alez, 2021;Saberi Riseh et al., 2022).
Recent attention has been focused on plant extracts as biostimulants because they contain several active substances, including phenolic compounds, carbohydrates, minerals and trace elements, growth hormones, betaines, sterols, tannins, flavonoids, alkaloids and saponins (Persaud et al., 2019).These biologically active compounds can stimulate plant growth and development and can combat many pathogenic strains of microorganisms (Kisiriko et al., 2021).The antimicrobial mechanism of active compounds in plant extracts is related to damage to the bacterial cell membrane by lowering the pH of the cytoplasm and inducing membrane hyperpolarization (Gonelimali et al., 2018).

Inorganic nonmicrobial plant biostimulants.
Inorganic PBs are composed of chemical elements or molecules, including beneficial elements and salts, with proven effects on plant performance while also functioning as plant protectors (du Jardin, 2015; Dorneles et al., 2018;Ahammed and Yang, 2021).
Beneficial elements are those that besides not being universally essential for all plant species, their presence has been associated with various positive effects on plant growth, nutrient uptake, stress tolerance, induction of disease resistance, and overall plant performance.The members of this group, which includes silicon and nickel among other elements, are naturally present in soils and plants, and their beneficial effects can be inherent, such as the reinforcement of cell walls, or become evident under specific stressful conditions, when the plant response to pathogen attack is triggered (Schumann and Spann, 2010;Dorneles et al., 2018;Ahammed and Yang, 2021).A practical example of this tool applied to disease management is the study conducted by Einhardt et al. (2020), who evaluated the impact of soybean foliar treatment with nickel on the Asian soybean rust, which resulted in a significant reduction of disease severity.As discussed by Ahammed and Yang (2021), inorganic sources of silicon, such as silica gel, silicic acid, sodium/calcium/ potassium silicate, and amorphous silica, offer potential applications for fungal disease management.These authors emphasized that the antifungal activity and the induction of disease resistance by silicon are manifested through the formation of silicon-polymerized mechanical obstructions under the cuticle and in cell walls, as the main mechanisms underlying its protective effects.Dorneles et al. (2018) demonstrated that silicon applied to the soil in the form of calcium silicate effectively reduces the tan spot disease caused by Pyrenophora tritici-repentis in wheat and that this reduction is associated with the activation of phenylpropanoid metabolism, ultimately leading to the accumulation of antifungal phenolic compounds.
This group of PBs also includes the inorganic salts of beneficial and essential elements, including chlorides, phosphates, phosphites, and carbonates.Among these inorganic salts, phosphites (Phi) stand out as the most significant PBs, since extensive research has shown that they can act as effective plant protectors or dual-effect molecules.Since Phi are chemical analogs of orthophosphate (HPO 4 −3 ), they are primarily recognized as pesticides for oomycetes such as species of the genera Phytophthora, Pythium, Peronospora and Plasmopora (Carmona et al., 2018;Guo et al., 2021;Mohammadi et al., 2021;Vilela et al., 2022).Phi have also demonstrated their efficacy in controlling diseases of extensively grown crops caused by true fungi like species of the genera Sclerotinia, Macrophomina, Fusarium, Colletotrichum, and Phakopsora (Carmona et al., 2017;Gill et al., 2018;Einhardt, Souza, et al., 2020;da Silva Junior et al., 2021).For instance, MnPhi can directly inhibit S. sclerotiorum both in vitro and in vivo within soybean leaflets (Novaes et al., 2019).Furthermore, Phi are universally recognized as elicitors of plant defense responses involving intricate and multifaceted processes.Broadly, the application of Phi boosts the activity of enzymes like catalase, peroxidase, polyphenol-oxidases, and superoxide dismutase, while also increasing the production of phytoalexins (Novaes et al., 2019;da Silva Junior et al., 2021).Recent transcriptome-based analyses have extensively investigated the pathogen-suppressive effects of Phi in various crops, elucidating multiple target genes of phytopathogens (Gill et al., 2018;Y. Huang et al., 2020).

C. Other tools for plant stimulation and/or protection
This section describes a selection of exceptionally innovative tools related to molecular biology, biochemistry, and physics, including gene editing, RNA interference, nanotechnology, functional peptides and physical technologies.

Gene editing
Plant genomes can be edited to improve traits such as yield, abiotic stress tolerance and disease resistance.Genome editing (GE) techniques comprise a new set of tools that can accelerate the development of crop varieties resistant to diseases and abiotic stresses (Chen and Liu, 2023;Chen et al., 2023).Interest is currently focused on a new GE technology based on clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated sequences (Cas) (Erdo� gan et al., 2023;Khan, 2023).The CRISPR-Cas system is a prokaryotic adaptive immune system that can be used as 'genetic scissors' for GE (Tyagi et al., 2021).The simplicity of this system makes it a reprogrammable molecular tool capable of targeting and editing any site in a known genome.
There are six different types of CRISPR-Cas systems with multiple subtypes that vary in composition and mode of action, encompassing a family of enzymes with great versatility (Chaudhuri et al., 2022;Huang and Liu, 2023).This tool is interesting because it is cost-effective and user-friendly (Das et al., 2018), and has been successfully used to edit the genome of a vast number of plant species, including monocots and dicots (Chaudhuri et al., 2022;Wang et al., 2022;Jiang et al., 2022;Lu and Tian, 2022;Chincinska et al., 2023;Bi et al. 2023).CRISPR-Cas tools have successfully provided resistance to various fungal pathogens by targeting host susceptibility genes (Tyagi et al., 2021), demonstrating their potential in crop disease management.For instance, they have led to the development of rice plants resistant to M. oryzae (T� avora et al., 2022), as well as wheat plants resistant to Blumeria graminis f. sp.tritici (Zhang et al., 2017) and F. graminearum (Brauer et al., 2020).Moreover, they have demonstrated specific interference against RNA viruses in various crops (Mushtaq et al., 2021;Robertson et al., 2022).Research is ongoing to understand the interaction between Soybean mosaic virus and soybean proteins for virus resistance (Zhang et al., 2020;Hu et al., 2023).Additionally, rice lines with robust, broad-spectrum resistance to the bacterial pathogen Xanthomonas oryzae pv.oryzae (Xoo) have been developed (Wei et al., 2021;Peng et al., 2022).
A second GE technique is 'prime editing', which can be described as a search-and-replace GE tool that does not require donor DNA templates or doublestrand breaks (Huang and Liu, 2023;Ni et al., 2023;Zhao et al., 2023).This technique, first developed in protoplasts of wheat and rice (Li et al., 2021), can edit bases (base-to-base conversions), as well as perform small insertions and deletions, while reducing off-target edits and DNA damage.Although low editing efficiency in plants is a major constraint for prime editing in recent years there have been notable improvements in overcoming this challenge, resulting in the attainment of the resistance, exemplified by resistance to Xoo (Gupta et al., 2023).Thus, GE techniques have enormous potential in the fight against crop diseases, but there are still possible drawbacks to overcome, such as potential off targets accounting for unexpected side-effects (Hassan et al., 2020).Lastly, although field trials for genome-edited crops remain scarce, it is expected that research will accelerate its progress, leading to advances and enhancements in GE techniques.

RNA interference (RNAi)
RNAi is a naturally occurring phenomenon that regulates gene expression in eukaryotic cells.Since it is part of an evolutionarily conserved immune system against invading foreign DNA, it can be used to control crop diseases (Rajput et al., 2021).As a tool, it can be used to modify the expression of essential genes by the gene silencing mechanism, i.e., by targeting mRNA degradation and preventing the mRNA of the pathogen to express and produce a respective protein (Rodr� ıguez Melo et al., 2023).This mechanism is mediated by a family of ribonucleoprotein complexes called 'RNA-induced silencing complexes' (RISCs), a generic term for molecular complexes that can be programmed to target virtually any nucleic acid sequence for silencing.Programming is triggered by the appearance of double-stranded RNAs (dsRNAs) in the plant cell, which are processed into small noncoding regulatory RNAs (sRNAs): miRNAs and siRNAs.Next, sRNAs assemble into RISCs and guide the complex to cleavage of complementary RNA targets through basepairing interactions (Parperides et al., 2023).
One way to implement this strategy is to apply RNAi-based products exogenously through spray application, which is called spray-induced gene silencing (SIGS) (Gebremichael et al., 2021;Rodr� ıguez Melo et al., 2023).The dsRNA sprayed in the crop is absorbed by the plant cells and targets the mRNA of one or multiple genes of the pathogen, hindering the expression of pathogenicity-related genes.For instance, Koch et al. (2016) found that spraying long noncoding dsRNA inhibits F. graminearum growth in barley by targeting key mRNA genes for ergosterol biosynthesis in the pathogen.These authors also showed that the dsRNAs travel through the plant vascular system and are taken up by the pathogen at distant locations from the application site.Another application of this tool is genetic engineering in crops to produce sRNAs that silence virulence-related genes, known as 'host-induced gene silencing' (HIGS).In HIGS, artificial sRNAs are synthesized within host plant cells and transported to the pathogen cells through bidirectional cross-kingdom RNAi (Jiang et al., 2023;Mahanty et al., 2023).Pioneering studies by Yin et al. (2011) demonstrated the feasibility of using this method in wheat to establish long-lasting resistance against rusts caused by P. striiformis f. sp.tritici or P. graminis f. sp.tritici.Schaefer et al. (2020) reported on transgenic RNAi wheat lines encoding a HIGS construct simultaneously silencing three Blumeria graminis f. sp.tritici effectors and achieving significant reduction of virulence at an early stage of infection.Similarly, Hu et al. (2020) reduced the Asian soybean rust symptoms in soybean leaves through both a bean pod mottle virus-based HIGS strategy and spraying dsRNAs (SIGS) directly onto leaves prior to P. pachyrhizi inoculation.Both SIGS and HIGS are promising technologies and could be adapted to simultaneously target and control multiple fungal diseases (Zhang et al., 2023).Several HIGS are now commercially available and widely used in largescale grain crops for pest management (De Schutter et al., 2022).The concurrent use of HIGS and CRISPR-Cas is expected to significantly increase longlasting disease control in grain crops (Zhang et al., 2023).While the SIGS strategy shows potential to protect crops against numerous pathogens, the cost of dsRNAs production could be a limiting factor.Another difficulty for foliar applications of dsRNAs is to bypass the plant barriers (cuticle, cell wall and plasma membrane) to be up taken by plants and pathogens (Wytinck et al., 2020;Qiao et al., 2021).Other challenges that need to be addressed to enhance this technology are the optimization of the RNAi design and the finding of an appropriate formulation to stabilize naked dsRNA (H€ ofle et al., 2020).Considering these factors, the efficacy of RNAi varies considerably based on the delivery method used.Consequently, numerous research endeavors have been directed toward creating alternative nanoparticles to enhance the durability and resilience of dsRNAs against environmental factors and enzymatic degradation in agricultural settings (Ghosh et al., 2023;Rodr� ıguez Melo et al., 2023;Wang et al., 2023).

Nanotechnology
Nanoparticles (NPs) of different metals including silver (Ag), aluminum (Al), gold (Au), cadmium (Cd), cerium (Ce), copper (Cu), iron (Fe), selenium (Se), silicon (Si), titanium (Ti) and zinc (Zn) have the potential to serve as nanofungicides and nanoantibiotics against pathogens when administered as foliar sprays or seed treatments, or in food systems (Marou� sek et al., 2022;Li et al., 2023;Tarakanov et al., 2023;Tortella et al., 2023).Numerous studies have verified that metallic NPs cause direct damage to the cell walls of fungal hyphae, leading to hyphal plasmolysis (Rizwana et al., 2022).Biogenic nanomaterials synthesized by eco-friendly 'nanofactories' have gained widespread acceptance as green and cost-effective methods to produce NPs, avoiding the need for chemical additives (Omran and Baek, 2022;Ahmed et al., 2023;Tomah et al., 2023).Recent studies in extensively grown crops have shown that biosynthesized titanium dioxide (TiO 2 ) NPs applied on wheat plants have potent fungicidal activity, effectively controlling diseases caused by B. sorokiniana and P. striiformis f. sp.tritici (Satti et al., 2021(Satti et al., , 2022)).Some NPs can trigger SAR against pathogens (Kumari et al., 2023;Li et al., 2023), as shown by Karmous et al. (2023), who reported that biologically synthesized Zn and Cu oxide NPs can strengthen soybean resistance against F. virguliforme.Furthermore, NPs have been demonstrated to enhance plant growth and function as nanofertilizers (Del Buono et al., 2021;Rai-Kalal et al., 2021;Wohlmuth et al., 2022).Despite its promising potential as a crop disease management tool, nanotechnology in agriculture is currently in its early stages of development, thus, significant research efforts, including field-level investigations and toxicological studies, are required to advance the development of commercial nano-formulations (Dutta et al., 2023;Hussain et al., 2023;Tortella et al., 2023).The use of nano-encapsulated pesticides has the potential to reduce the volume of chemical fumigants and pesticides reaching the soil surface compared to conventional formulations (Sandhya et al., 2017), while simultaneously providing plant protection against various phytopathogens (Janatova et al., 2015).In addition, nanostructured materials, with their high surface areato-volume ratio, can serve as carriers for active molecules, delivering these substances with increased precision and reduced impact on nontarget organisms, representing a promising avenue for future advances.

Functional peptides
Functional peptides are short polypeptides with a small molecular size, typically composed of up to 50-60 amino acids, originating either from natural sources (microorganisms, animals, or plants) or through artificial synthesis (Li et al., 2021;Montesinos, 2023).They have recently emerged as a popular research subject in plant protection due to their roles as antimicrobials, resistance inducers, and plant growth promoters, in addition to their potential effectiveness against insects and weeds (Li et al., 2021;Zhang et al., 2023).Functional peptides offer numerous positive aspects as tools for disease management in extensively grown crops, including abundant raw material sources, high activity, and environmental safety (Zhang et al., 2023).Peptides exhibiting antibiotic activity against pathogens, often referred to as antimicrobial peptides (AMPs), have various mechanisms of action, including the following: (i) cell lysis by poration and disorganization of cell membranes, (ii) interference with internal cellular processes, (iii) interaction with external cell structures, (iv) inhibition of biofilm formation and other colonization structures, and (v) inhibition of spore germination or germ tube elongation (Montesinos, 2023).Although most studies involving AMPs have primarily focused on their in vitro activity and have often overlooked the assessment of the complete pathosystem, these tools appear to be promising for plant protection.Examples of microbial-derived AMPs with potential applications against phytopathogens are bacteriocins (like amylocyclicin and ericin S) and cyclic lipopeptides (like iturin and surfactin) synthesized by Bacillus spp., cyclodepsipeptides produced by Pseudomonas spp., and peptaibols (like Trichokonin VI) produced by Trichoderma spp., all of which have been shown to trigger defense responses in plants against infection by pathogenic fungi and bacteria (Montesinos, 2023).Some fungal-derived AMPs tested against important pathogens of extensively grown crops are ANAFP from Aspergillus niger and Trichokinin VI from T. pseudokoningii to control F. oxysporum, and PAF from Penicillium chrysogenum tested against Blumeria graminis f. sp.hordei and P. triticina (Zhang et al., 2023).AMPs can also be produced by plants, with defensins being the largest family expressed in this kingdom (Li et al., 2021).Some broad-spectrum antifungal AMPs with proven effectiveness against F. graminearum include MsDef1 and MtDef4 from Medicago spp.and DefMT3 from Ixodes ricinus (Velivelli et al., 2020;Shwaiki et al., 2021;Leannec-Rialland et al., 2021).Several AMPs isolated from various crops have demonstrated effectiveness against pathogens.For instance, ZmD32 and ZmPep1 from corn have shown efficacy against F. graminearum, SD2 from sunflower has proven effective against S. sclerotiorum, Peptide-1 from rice has displayed activity against M. oryzae, a1-purothionin from wheat has exhibited antibacterial properties against Xanthomonas and Erwinia, Thionin 2.4 from Arabidopsis thaliana and CycloviolacinO8 from Viola odorata have both demonstrated antifungal activity against F. graminearum, and Ee-CBP from Euonymus europaeus has been found to be effective against F. culmorum (Shwaiki et al., 2021;Zhang et al., 2023).A recently released product based on immune-inducing peptides (SaoriV R , Plant Health Care) has been shown to be effective as a seed treatment to prevent the Asian rust in soybean (Zhang et al., 2023).Special attention is being currently paid to designing peptides that exhibit various mechanisms of action for plant protection, as they could effectively counteract potential pathogen resistance and enhance different aspects of plant physiology.

Physical technologies
Many physical technologies, such as nonthermal plasmas, electropriming, ultrasound, ozone, UV-light, magnetic fields, and irradiation with gamma rays and X-rays, have been proposed for seed treatment with the aim to remove pathogens and enhance germination, plant resistance to common diseases and crop yield (Filatova et al., 2020;Kocira et al., 2022;Kriz et al., 2021;Rifna et al., 2019).While most of them are currently in the exploratory phase, nonthermal plasma technology is likely the one closest to being subjected to field trials and large-scale application.Nonthermal plasmas are quasi-neutral partially ionized gases with biocidal effects that can remove fungal pathogens associated with seeds and can also improve germination, plant growth, plant resistance to common diseases, and grain yield in soybean, wheat, corn, rice, and barley (Adhikari et al., 2020;Filatova et al., 2020;P� erez Piz� a et al., 2018P� erez Piz� a et al., , 2020;;Moumni et al., 2023).Some examples of fungi effectively inactivated by seed treatment with nonthermal plasmas are Penicillium verrucosum in barley and wheat (Los et al., 2020), the Diaporthe/Phomopsis complex in soybean (P� erez Piz� a et al., 2018), and Aspergillus flavus, Alternaria alternata, and F. culmorum in corn (Zahoranov� a et al., 2016).Nonthermal plasmas can act as biocides likely due to the action of their active compounds (such as reactive oxygen species and reactive nitrogen species), or through outer membrane oxidation, intracellular protein degeneration, and DNA fragmentation.They are considered an effective approach to counteract the evolution of microbial resistance due to their multiple mechanisms (P� erez-Piz� a et al., 2021).As stimulators of plant growth, plasmas are supposed to biochemically modify the seed coat structure, promoting water uptake during germination, interacting with cells inside the seed, promoting natural signals that ultimately alter enzyme activities and phytohormone balance, and being involved in epigenetic changes in the DNA (P� erez-Piz� a et al., 2022).In addition, the concept of 'plasma vaccination', which involves inducing plant resistance to pathogens through plasma treatment, has emerged as a novel and actively researched field of study (Adhikari et al., 2020).This technology is considered profitable for seed treatment due to several of the following reasons: (i) it provides uniform treatments, (ii) it does not disturb the function of plant tissues, (iii) it does not produce pollutants, (iv) it can be scaled up for large-scale applications suitable for seed companies, and (v) it can enhance the effectiveness of other tools applied to seeds, such as bioinoculants, biopesticides, and fungicides (P� erez-Piz� a et al., 2019;Kocira et al., 2022).

III. Impact of mineral nutrition on plant disease in extensively grown crops
This section seeks to present a fresh perspective on plant mineral nutrition, emphasizing its crucial role in disease management as the pathway to achieve vigorous and healthy plants with greater opportunities to cope with diseases.Mineral nutrition plays a critical role in influencing growth and yield by affecting plant resistance or susceptibility to pathogens, mainly through two mechanisms: (i) the formation of mechanical barriers like thicker cell walls, and (ii) the stimulation of the synthesis of natural defense compounds against pathogens such as phytoalexins, antioxidants, and flavonoids (Schumann and Spann, 2010).The potential impact of nutrition, specifically nitrogen, on diseases in extensively grown crops has largely been demonstrated as it is considered crucial for plant health (Gupta et al., 2017).In accordance, Maywald et al. (2023) has recently conducted a comprehensive review on the disease-protective effects of nitrogen and various chemical nitrogen forms when applied to wheat, rice, and corn.Notably, while nitrogen fertilization may reduce plant susceptibility to necrotrophic fungal diseases (e.g., tan spot and root rot in wheat and sheath rot and false smut in rice), it may also increase the severity of diseases produced by biotrophic pathogens (e.g., rusts and powdery mildew in wheat and sheath spot and brown spot in rice).
The mechanism underlying this phenomenon relies on the fact that nitrogen is the key component of amino acids and, therefore, an excessive supply of nitrogen often derives on high amounts of amino acids and other N-containing compounds in plant tissues, creating a very favorable environment for biotrophic pathogens (Schumann and Spann, 2010;Gupta et al., 2017).This observation highlights the importance of avoiding nitrogen deficiencies while also minimizing the promotion of pathogen activity through excessive applications (Maywald et al., 2023).The efficacy of nitrogen fertilization on plant protection also depends on the form under which it is applied.For instance, the use of ammonium-based fertilizers can increase the incidence of some soilborne diseases (e.g., root rots caused by Fusarium and Phytophthora, takeall disease caused by G. graminis var.tritici), whereas nitrate-based fertilizers generally have the opposite effect (Schumann and Spann, 2010).Unlike that observed for nitrogen, an adequate supply of potassium typically leads to increased resistance against attacks by various pathogens (e.g., P. tritici-repentis and P. triticina in wheat, R. solani in rice, and Diaporthe sojae and P. pachyrhizi in soybean), whereas deficiencies in potassium tend to lower this resistance (Schumann and Spann, 2010;Gupta et al., 2017).Several researchers have also reported the involvement of other plant-essential macronutrients (sulfur, calcium, and magnesium) and micronutrients (boron, zinc, manganese, and copper) on disease control in extensively grown crops (Bloem et al., 2014;Gupta et al., 2017;Einhardt et al., 2020;Ahammed and Yang, 2021).In relation to sulfur, elemental sulfur has demonstrated its efficacy as a foliar fungicide, and the application of sulfate as a soil fertilizer has been noted to mitigate diseases by triggering plant defense mechanisms (Bloem et al., 2014;Haneklaus et al., 2009).Haneklaus et al. (2007) demonstrated that the application of elemental sulfur weekly to barley leaves, beginning at anthesis, leads to a notable decrease in the infection rate of Fusarium head blight caused by F. culmorum.Micronutrients are recognized to play a crucial role in disease control through various mechanisms: (i) directly enhancing plant health from a nutritional standpoint, (ii) inhibiting pathogen penetration by influencing cell wall rigidity and the physical integrity of the membrane structure, and (iii) inducing the SAR defense system within the plant (Gupta et al., 2017).Ward (2015) examined the impact of foliar applications of micronutrients on the severity of significant soybean diseases caused by C. kikuchii and P. pachyrhizi and demonstrated promising results primarily attributed to the combined effects of increased yields resulting from minor element fertilization and simultaneous disease suppression.Understanding the interactions between plant nutrition and disease development can pave the way for innovative approaches that maximize crop health and productivity while reducing reliance on conventional chemical interventions.

IV. Unlocking synergies: the power of combined tools
A global debate is currently taking place to determine the most suitable path toward achieving agricultural sustainability and ensuring food security.Concerns about the emergence of fungicide-resistant pathogens and their impact on the environment and human health have promoted the use of microbial-derived products as alternatives to standard fungicides.Nonetheless, the few in vivo studies examining the use of these microorganisms represent a limitation for their potential adoption and commercialization.To overcome these limitations, an integrated approach mixing microorganisms with fungicides has been proposed as a tool to reduce fungicide usage, minimize residue on crops, and decrease the selection pressure on pathogens, reducing the chances of resistance development (Ons et al., 2020).Aiming to successful large-scale implementation, intensive research is being performed on the timing, frequency, and compatibility of microbial applications with fungicides.Trichoderma has been a good example, demonstrating excellent compatibility with chemical fungicides, thus enabling its integration into various pest management strategies (Lahlali et al., 2022;Pimentel et al., 2022).In this line, Wang et al. (2019) proved the synergistic effects of the combined application of T. harzianum and difenoconazole-propiconazole as a foliar treatment on corn plants, effectively controlling Southern corn leaf blight disease caused by Cochliobolus heterostrophus.
Similarly, beneficial bacteria have exhibited compatibility with fungicides (Ons et al., 2020), as demonstrated by Shen et al. (2019), who investigated the compatibility of diverse rice endophytic bacteria, such as Bacillus and Pseudomonas species, with fungicides like etridiazole, metalaxyl, and tricyclazole, and found that these bacteria exhibited tolerance to at least two of the fungicides tested.In rice field trials, the synergistic application of T. harzianum, P. fluorescens, and carbendazim demonstrated increased efficacy against M. oryzae, surpassing the effects of their individual application (Jambhulkar et al., 2018).Greenhouse and field experiments on corn have also revealed that combining a half-dose of botanical extract from Jacaranda mimosifolia with half-strength mefenoxam effectively reduced the stalk rot disease caused by F. verticillioides, highlighting the potential of using this combined tool to achieve effective disease control and reduce fungicide doses (Naz et al., 2021).The ongoing exploration also involves combining various PBs with protective effects, as well as combining these PBs with fungicides.For example, the compatibility of CuPhi with a strobilurin-triazole fungicide in a tank mix, which was prepared and applied in the field, revealed synergistic effects in controlling late-season foliar diseases in soybean caused by S. glycines and C. kikuchii (Carmona et al., 2019) (Upadhayay et al., 2023).
Another promising method currently being explored is that known as 'rhizosphere engineering', which involves the co-inoculation of a consortium of microorganisms (e.g., Trichoderma-Azotobacter) along with seaweed extracts, botanicals, inorganic compounds, polymers, and/or animal-derived products (Rouphael and Colla, 2020;Woo and Pepe, 2018).The aim of this strategy is to emulate the natural biological networks found in native soils, representing a noteworthy progression toward sustainable agricultural practices.As an example, Prasetyo et al. (2021) studied the effects of combining T. asperellum, a consortium of AMFs (Enthropospora sp., Gigaspora sp., and Glomus sp.), and botanical extracts from betel leaf (Piper betle) and turmeric (Curcuma longa) against corn downy mildew caused by Peronosclerospora spp.and observed synergistic effect in reducing the severity of the disease in plants.Another attractive combined strategy involves the combination of chemosensitization with fungicides, an emerging and promising alternative aimed to expand the effectiveness of fungicidal treatments.This approach involves combining a commercial fungicide with a specific non-or marginally fungicidal substance (such as secondary plant or microbial metabolites and their synthetic analogs), at concentrations at which neither compound would be effective when used alone (Shcherbakova, 2019).In this regard, Shcherbakova et al. (2021) discovered that the combined treatment of seeds with thymol and difenoconazole (at a dose significantly lower than normal) provided increased protection against various pathogens in barley (Bipolaris sorokiniana, Fusarium spp., and Alternaria spp.) and wheat (F.culmorum).Additionally, thymol and tebuconazole, when applied to the leaves, effectively reduced the severity of the glume/leaf blotch caused by Parastagonospora nodorum in wheat.In accordance, Dzhavakhiya et al. (2019) applied structural analogs of natural amino acids þ tebuconazole and found synergism in inhibiting the in vitro growth of F. culmorum colonies.Since the biochemical and structural targets of chemosensitizing substances differ from those targeted by fungicides, this approach does not contribute to the selection of resistant pathogenic forms and reduces the environmental impact by lowering the effective dosage levels of toxic fungicides (Dzhavakhiya et al., 2019;Shcherbakova, 2019).

V. Challenges for the use of new tools for the management of phytopathogens in extensively grown crops
Despite the promising potential of new tools for disease management, their extensive use poses certain constraints and challenges that need to be carefully addressed to ensure their effective application in practical settings.Biofungicides and biostimulants are promoting research interest, yet practical implementations in real-world settings (particularly in large-scale scenarios) are still relatively restricted due to limitations, including the following: (i) high dependence on environmental conditions, rhizosphere complexity and pathogen pressure, (ii) inconsistent efficiency in field conditions, (iii) short shelf-life and high biodegradability, and (iv) narrow range of controlled pathogens (du Jardin, 2015; Lahlali et al., 2022;Rocha et al., 2019).These aspects require continuous and consecutive applications in experiments and real-world settings to enhance their effectiveness and achieve desired results, at the expense of economic benefit.Concerns about potential undesirable by-products and ecological consequences of introducing nonnative invasive species (i.e., outbreaks) raise additional issues (Eisner et al., 2023).The socio-economic aspect also presents challenges such as limited market availability and low acceptance by farmers (Lahlali et al., 2022).Addressing these issues requires crucial efforts, including educating farmers not only about suitable storage conditions but also about managing expectations regarding the timeframe for results, which often differ significantly from those of synthetic compounds.Furthermore, the establishment of consistent global regulations (based on harmonized concepts) to supervise formulation quality and ensure the efficiency and viability of microbial strains is essential to prevent the presence of substandard products in the market (Caradonia et al., 2019).In an increasing order of complexity, inoculants based on various microorganisms or microorganisms plus organic or inorganic molecules present additional issues regarding the particularities of each component and their compatibility (Poveda and Eugui, 2022).In this regard, Rouphael and Colla (2020) suggested that the use of high-throughput phenotyping (encompassing small, medium, and large-scale analyses of phenotypic traits) is a promising approach especially applicable to the evaluation and development of bioinputs with complex matrices containing various groups of bioactive molecules.Significant technical challenges arise in the domain of natural-origin products.Additionally, a more comprehensive scientific understanding of the intricate interactions between fungi and host plants remains essential (du Jardin, 2015).As complexity increases, formulations involving various microorganisms or their combination with organic or inorganic components introduce additional challenges, demanding attention to the specific requirements of each component, alongside with comprehensive compatibility assessments and functionality evaluations (Poveda and Eugui, 2022).Despite extensive research efforts to unearth and create innovative solutions, there has been limited enthusiasm from companies in delivering these novel tools to growers.As recently elucidated by Montesinos (2023), this is linked to several factors: (i) modest returns on investment, (ii) obstacles in obtaining regulatory approval, (iii) the nascent stage of development for many disease control approaches, (iv) ongoing evaluation and validation in field conditions, and (v) safety worries associated with certain techniques, such as nanotechnology.

VI. Tan spot in wheat: a model case of the implementation of novel tools in integrated disease management
In the efforts to propose a disease management model involving new tools, this section evaluates the P. tritici-repentis (Ptr) -wheat pathosystem as an illustrative example.This choice stems from several key characteristics associated with Ptr: (i) its role as a devastating foliar pathogen that triggers tan spot disease in wheat, leading to significant global yield losses (Sautua and Carmona, 2021); (ii) its classification as a necrotrophic ascomycete that primarily affects the above-ground parts of the plant, with specific presence in seeds and stubble rather than in the soil (Trezzi-Casa and Carmona, 2016); (iii) its relatively low transmission rate from the seed to aerial organs, when compared to transmission rates of other foliar pathogens like P. teres and B. sorokiniana (Carmona et al. 2006); (iv) its lack of epidemiologically significant secondary hosts; (v) its absence of resistant structures; and (vi) its notable reduction in inoculum and viability through stubble management and crop rotations (Summerell and Burgess, 1989).To date, this pathogen is managed mainly with the use of fungicides.The significance of the disease and the urgent need to reduce chemical usage emphasize the importance of considering environmentally friendly management tools.The distinctive traits of the Ptr-wheat pathosystem present promising opportunities to promote the adoption of innovative tools, such as dualacting biostimulants and biofungicides.For instance, since the pathogen persists mainly in seeds (beneath the seed coat) and stubble, adopting strategies targeting these primary sources of initial inoculum holds prospective advantages.In the case of the use of microbial-derived tools, the microorganisms need only to establish themselves on the seed coat without having to contend with rhizosphere microorganisms, allowing them to focus entirely on obstructing transmission to the coleoptile.Thus, as the seed germinates, the BCAs encounter the pathogen, effectively stopping any subsequent infection.The use of consortia of BCAs as seed treatment would further enhance the expectations of succeeding, considering the combination of mechanisms of action that could be interacting, in a complex and complementary way.The value of BCAs also lies in the fact that these microorganisms have proven to be a useful and cost-effective tool for seed treatment with considerable potential to control seed-borne pathogens.The fact that Ptr is considered a weak pathogen opens the opportunity to address the disease through improved overall plant health, highlighting the significance of balanced nutrition, especially concerning nitrogen.In addition, Ptr has had noteworthy genetic evolution, outpacing numerous other pathogenic species in terms of success.A pivotal aspect of this evolution involved the acquisition of the ToxA gene from Parastagonospora nodorum via lateral gene transfer (Friesen et al., 2006), which rendered it the most recently emerged pathogen in wheat.Unlike pathogens such as rusts, whose historical origins date back to ancient times, Ptr is relatively recent, with its presence having been recognized for only about half a century.Considering the specific features of the Ptr-wheat pathosystem, a comprehensive approach was devised for Integrated Disease Management to combat tan spot disease in wheat.This proposal covers the complete crop phenological cycle and is visually represented in Figure 1.In preparation for sowing, several strategies can be used to attain two key objectives: diminishing the sources of inoculum and reinforcing crop protection.Achieving this involves: i) eradicating secondary hosts and volunteer wheat plants, ii) rotating crops with species from different families (Rom� an-Ramos et al., 2023), iii) managing stubble (See et al., 2022), iv) treating the soil with silicon sources (Dorneles et al., 2018) and biostimulants with protective effects (Bauza-Kaszewska et al., 2022;Eisner et al., 2023), v) performing an evaluation of nutrient availability, particularly focusing on nitrogen due to its potential influence on tan spot intensity, and implementing additional fertilization only if required (Sim� on et al., 2021;Schierenbeck et al., 2023), and vi) selecting genotypes that exhibit resistance or tolerance to the disease.Regarding seed treatment, a comprehensive set of strategies can be used to achieve two primary goals: to prevent the introduction of pathogens into the field including fungicide-resistant strains and to enhance overall crop protection.These strategies encompass a series of actions, including the following: i) rigorous and sensitive evaluation of seed health aimed to identify the presence of Ptr (Carmona et al., 2006), ii) treatment with biofungicides based on Trichoderma spp., Pseudomonas spp., and Bacillus spp.(Perello et al., 2006;Larran et al., 2016;Sharma M, 2017;Almoneafy et al., 2022;Asaturova et al., 2022;Khan et al., 2023;Reynoso et al., 2023;Zakaria et al., 2023), iii) application of biostimulants with protective properties such as mycorrhizae and PGPRs, silicon, algae or plant extracts, phosphite, chitosan, or salicylic acid (Kumar et al., 2018;Spagnoletti et al., 2021;Dutilloy et al., 2022;Mashabela et al., 2023;Moumni et al., 2023), iv) inoculation with consortia of beneficial microorganisms and BCAs (Jambhulkar et al., 2018;Czajkowski et al., 2020;Niu et al., 2020;Ram et al., 2022), v) treatment with innovative approaches like nonthermal plasmas (Los et al., 2020), vi) treatment with conventional fungicides (Carmona et al., 2006), vii) chemosensitization plus fungicides (Shcherbakova et al., 2021), and viii) treatment with strategic formulations of mixtures containing fungicides and biostimulants with protective effects or versatile biofungicides (Ahmed et al., 2019;Ons et al., 2020;Ghazi et al., 2021;Rebouh et al., 2022).Later, as the crop enters its growth phase, starting from the early vegetative stages, several strategic approaches can be implemented to mitigate disease intensity, ensuring crop protection, and securing healthy seed production.These approaches include: i) thorough assessment of nitrogen availability and supplementation if required (Sim� on et al., 2021;Schierenbeck et al., 2023), ii) regular field monitoring (Carmona et al., 2020), iii) judicious applications of herbicides, insecticides, and fungicides in conjunction with biostimulants with protective effects such as beneficial microorganisms, silicon, seaweed extracts, phosphite, chitosan, and salicylic acid (Reiss and Jørgensen, 2017;Dorneles et al., 2018;Le Mire et al., 2019;El-Gamal et al., 2021;de Borba et al., 2022;Dutilloy et al., 2022;Khan et al., 2023;Mashabela et al., 2023), iv) application of fungicides based on silver nanoparticles (AgNPs; Mishra et al., 2014;Jsarotia et al., 2018;Almoneafy et al., 2022) and v) RNAi (Qi et al., 2019;Liu et al., 2021).Finally, it is highly recommended to adhere to fungicide applications based on the economic damage threshold as proposed by Trezzi-Casa and Carmona (2016), using a criterion where the optimum timing for applications corresponds to that when 15-20% of leaves exhibit tan spot attack from the stem elongation stage GS 32 onwards (Carmona et al., 2014).

VII. Final remarks
The evidence gathered so far in this review suggests that the new tools to manage diseases in extensively grown crops could potentially enhance their effectiveness when used in combination.This integration could lead to a reduction in the use of more environmentally disruptive measures without entirely replacing them, presenting a promising strategy for sustainable disease management in agricultural systems.Furthermore, the simultaneous use of fungicides and the new tools reviewed herein offers a viable anti-resistance strategy, preventing or retarding the emergence of resistant fungal strains and thereby extending the utility of still-effective fungicides.Awareness campaigns in the agricultural sector are crucial to inform farmers and stakeholders about the gradual or potential delayed effects of novel tools, in contrast to chemical fungicides, while emphasizing their long-term benefits in preserving ecosystem services.Regarding the evaluation and development of new tools, there is a growing demand of high-throughput phenotyping, a method encompassing extensive analysis of phenotypic traits across various scales, particularly in relation with tools with complex matrices comprising diverse groups of bioactive molecules.Additionally, -omics approaches, which involve genomic, transcriptomic,  providing potential benefits.Bioinputs of natural origin are commonly associated with characteristics such as biodegradability, nontoxicity, nonpolluting nature, and harmlessness to most organisms; however, it is unclear whether these assumptions apply to all bioinputs because some of them are not typically found in agricultural environments.Conducting thorough risk assessments on a case-by-case basis is necessary to evaluate potential hazards associated with novel plant protection tools, enabling the development of clear and equitable regulations for their safe and responsible use.
As a corollary of this review, Figure 2 presents a comprehensive summary of the tools studied or applied in extensive cropping systems, highlighting those with significant potential for further exploration, development, and practical field application, serving as a roadmap for future advances in disease management in such systems.

Figure 1 .
Figure 1.Integrated disease management for wheat tan spot caused by Pyrenophora tritici-repentis, incorporating novel tools.

Figure 2 .
Figure 2. New tools for disease management in extensive cropping systems.

Table 1 .
Overview of key characteristics and functions of major bacterial and fungal genera involved in biological control.