Breeding indicators for high-yielding field pea under normal and heat stress environments

Abstract The warming Canadian summers have become a major abiotic stress to crops, including pea. In the past decade, attempts were made in the understanding of heat stress effect and genomic mapping for heat-responsive traits in field pea. In this study, a new recombinant inbred line population (PR-24) consisting of 39 lines was tested in 6 trials in the summers of 2020 (near normal weather conditions) and 2021 (hot/dry conditions). PR-24 was phenotyped for days to flowering (DTF), days to maturity, plant height, lodging, yield components, plot yield, and seed quality traits. Plant height could be an effective indicator for yield prediction, because its correlation with plot yield was significantly positive in all six trials despite varying degrees of heat and drought stress. Under normal summer weather conditions in 2020, relatively late maturity was correlated with greater seed yield; under heat/drought stress conditions in 2021, successful pod development on the main stem was important for final plot yield. Linkage mapping was used to dissect the genomic regions associated with the measured traits. Four QTLs were identified over multiple trials, one each for DTF (chromosome 7), reproductive node number (chromosome 5), pod number (chromosome 2), and seed protein concentration (chromosome 5). Furthermore, two indices, i.e., stress tolerance index and geometric mean yield, previously used in drought tolerance assessment were validated as useful criteria for heat tolerance assessment in this study.