Quantitative trait locus mapping of genomic regions controlling herbage yield in perennial ryegrass

Genetic control of herbage yield-a complex trait of fundamental importance to agricultural productivity-was characterized in a perennial ryegrass biparental mapping population (I x S). Seasonal and combined growth score estimates of herbage yield(GS) were obtained from a trial conducted at three sites in New Zealand, over 2 years. Twenty-nine quantitative trait loci (QTL) for GS were identified on an I x S genetic linkage map constructed using simple sequence repeat (SSR) markers. Most QTL explained less than 15% of the phenotypic variation. QTL consistency was low among and within trial sites and years but 17 QTL were observed in more than one environment or season. QTL on linkage groups (LG) 1, 2, 4 and 6 were most consistent, based on numbers of QTL co-located at these positions and persistence of their allelic effects. SSR markers from consistent QTL positions may be beneficially applied in marker-assisted selection to enhance genetic gain for herbage yield in ryegrass breeding.