Evaluation of Physiological Traits Associated with Wheat Yield in the Southern High Plains.

Drought is the most important factor limiting wheat (Triticum aestivum L.) yield in the U.S. Southern High Plains. Breeding new and suitable cultivars is crucial to reduce yield loss from drought and maintain high yield in the area. The objective of this study was to evaluate some physiological traits related to wheat yield under water-limited conditions. We tested a population of 124 F_5:7 recombinant inbreed lines (RIL) derived from the cross of TAM 112/TAM 111 (TX1112), along with TAM 111 and TAM 112. The population and parents were grown in multiple years (2011-2014) at three locations in the Southern High Plains under various water regimes, ranging from dryland to limited and full irrigations. In total, they were grown in 10 different environments. Traits evaluated in the TX1112 population include heading date, plant height, biomass at maturity, harvest index (HI), three yield components (spikes/m2, seeds/spike and thousand-kernel weight, TKW), some early stage traits (biomass and NDVI at jointing), carbon reserve remobilization, and canopy temperature during grain filling. Among these traits evaluated, biomass at maturity was correlated to yield in all 10 environments but HI was only correlated to yield in 6 environments. Biomass at maturity is a very good predictor for yield among under drought conditions, which explained 80% of yield variation among under water limited conditions. Among the early stages traits, biomass and NDVI at jointing stage were positively correlated to yield. Carbon reserve remobilization from stems can significantly contribute to gain filling and yield under drought conditions. Among the lines in TX1112 population, there was a positive correlation between yield and C remobilization per unit of area. In addition, low canopy temperature also contributed to greater yield under drought conditions.