Number of galls per gram of dry root infected by M. incognita 14 days post-inoculation on tomato genotypes grown under ambient (390 ppm) and elevated CO₂ (750 ppm).

Each value represents the average (±SE) of four replicates. Different lowercase letters indicate significant differences between CO₂ levels within the same tomato genotype (LSD test: df = 1,16, P <0.05); different uppercase letters indicate significant differences among tomato genotypes within CO₂ levels (LSD test: d.f. = 2,24, P <0.05).