Genetic control and QTL analysis of cotyledon bleaching resistance in green field pea (Pisum sativum L.)

Resistance to bleaching is an important factor for quality grading of Canadian green field pea and an important selection criterion in green pea improvement. This research was conducted to determine the genetic control of bleaching resistance in green peas using 90 recombinant inbred lines (RILs) derived from a cross between cultivars Orb and CDC Striker. These lines were evaluated under field conditions for two years in two locations in Saskatchewan, Canada. Harvested whole seeds and cotyledons were evaluated for greenness using the Hunter Lab colorimeter before and after exposure to a high light intensity accelerated bleaching treatment. The RILs were genotyped using amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) molecular markers. Heritability estimates for whole seed and cotyledon greenness were moderate (0.72 and 0.69, respectively) and increased when assessed after exposing whole seeds and cotyledons to accelerated bleaching conditions (0.83 and 0.82, respectively). The genetic linkage map constructed based on a total of 224 AFLP and SSR markers spanned over 890 cM of the pea genome. Multiple QTL mapping detected major QTLs on LG IV and LG V as well as location- and year-specific QTLs on LG II and LG III associated with green cotyledon bleaching resistance in field pea. The results demonstrated the importance of the seed coat in protecting the cotyledons from bleaching.