Molecular Marker Dissection of Ryegrass Plant Development and its Response to Growth Environments and Foliage Cuts

Abstract

For perennial forage grasses, tillering and shoot elongation are important developmental events to determine grassland production. To thoroughly identify and characterize quantitative trait locus (QTL) regions controlling the events, a perennial ryegrass (Lolium perenne L.) mapping population comprising 188 F2 individuals was evaluated for tiller number (TN), plant length (PL), and leaf length (LL) over 12 cuts in replicated field and pot experiments in Sapporo, Japan, during 2 yr. Quantitative trait loci were repeatedly detected in 16 genomic regions. Based on the QTL, 10 regions affected both shoot elongation (PL and LL) and tillering (TN), whereas only six regions had a single effect on either event. Five QTL regions mapped on linkage groups 1, 2, 5, and 6, explaining at maximum 34 to 56% phenotypic variance, likely contain key genes for plant development. Profiles (e.g., direction and magnitude) of QTL effects differed greatly among most regions, indicating a large diversity among the genes involved. Statistical tests revealed significant interaction effects of genotype with growth condition and cut for all QTL regions. The QTL positions were compared with those reported for ryegrass and rice, suggesting the presence of genes identical to the current population and semiwild perennial forage grasses. The current QTL analysis indicated that the control of ryegrass plant development involves diverse, unique genes whose effects are enhanced or suppressed by growth environment and foliage cutting.