Defining the Pleiotropic Nature of Heat Tolerance QTLs Controlling End-Use Quality and Yield Stability During Reproductive Stage Heat Stress in Wheat (Triticum aestivum).

High temperature during reproductive development is a major factor limiting wheat production and end-use quality in the Southern Great Plains and other environments worldwide. We have initiated a project integrating genotypic (QTL), multiple phenotypic, and transcript level data to identify genes controlling reproductive stage heat tolerance in wheat. Heat tolerance is defined here as maintenance of yield and end-use quality during reproductive stage heat stress. Efforts have focused on building recombinant inbred lines (RILs), collecting RIL morphological and yield response data from field and controlled environment studies, and mapping QTLs linked to reproductive stage heat tolerance. Given their importance and known sensitivity to heat stress, QTLs associated with end-use quality maintenance were mapped in correlation with yield maintenance QTLs to determine the collective pleiotropic effects of heat tolerance QTLs.  Mapping of quality maintenance QTLs was done by SDS sedimentation of grain from each RIL harvested in growth chamber imposed heat stress experiments.  Heat tolerance stemmed from the HWSW ‘Halberd’ parent. The population consisted of 64 F6 ‘Halberd’ X ‘Cutter’ RILs grown under both heat stress and control conditions in the greenhouse. Heat stress was applied by a three-day treatment of 38∞ applied 10 days after pollination. Quality results were analyzed for their relation to mapped yield maintenance QTLs. Detected QTLs were analyzed in relation to grain quality results, as determined by SDS sedimentation, for 150 elite breeding lines derived from the Halberd parent. The map developed in this study will help us determine whether grain quality traits and yield maintenance QTLs segregate together or independently from heat tolerance QTLs. An improved understanding of the correlation between end-use quality and yield stability QTLs (heat tolerance) during reproductive stage heat stress will aid in breeding plants possessing both attributes and in basic research aimed at defining the molecular basis of heat tolerance.