Fine Mapping of Biomass Yield Quantitative Trait Loci in Lolium Perenne L.

Biomass yield is a complex quantitative trait controlled by many environmental and genetic factors. Therefore its study relies on QTL mapping. In a precursor study, a genetic map of L. perenne was constructed on an inbred-derived F2 population and three major biomass QTL have been found on linkage groups (LGs) 2, 3 and 7. In this study, a fine map of the QTL positions was developed by mapping additional ryegrass specific SSR, rice Sequence Tagged Site and Diversity Array Technology markers. A total of 153 markers were added to the existing map leading to a map density of 3.5 cM. The QTL positions were recalculated for dry weight, fresh weight, dry matter and leaf width and in accordance to the preliminary analysis biomass QTL were localized on LGs 2, 3 and 7 but despite the fine map the QTL intervals were not reduced. In order to analyze the QTL regions, the screening of a L. perenne BAC library was performed using the markers flanking the QTL and several clones were isolated. After analysis using the AFLP fingerprinting method, five clones were send for full sequencing to perform a gene prediction and annotation using the Ab initio approach. The annotation revealed for one of the gene structures predicted homology to the lg1- like gene and four other showed homology to regions flanking genes of interest suggesting the possible presence of the genes within the biomass QTL region. The four genes were: L. perenne heading date (Hd1) gene, Avena strigosa beta-amyrin synthase (Sad1) and cytochrome P450 CYP51H10 (Sad2) genes and Lolium multiflorum gene for cold responsive protein.