Resynthesized Hexaploid Wheat Provides Heat Adaptive Traits from Progenitor Species for Introgression into Elite Wheat Germplasm.

Future food security requires immediate efforts in developing germplasm adapted to warmer climates. The use of wild relatives can improve yield through incorporating novel allelic diversity into germplasm. In this work, the performance of a set of wheat elite lines derived from resynthesized hexaploid wheat was compared to their recurrent parents under three different heat stress conditions (temperate or non-stress, heat stress, and extreme heat) under field conditions. The elite synthetic derived lines showed clear yield superiority under heat stress compared to recurrent parents of up to approximately 60%. Advantages were reflected in in yield components like grain number per unit area, and the superiority of elite synthetic derived lines compared to recurrent parents were also noticeable in terms of thousand kernel weight in all three environments. Physiological traits related to heat tolerance in the elite synthetic derive lines included water soluble carbohydrates storage, cooler canopy temperature, earliness, and pigment composition.  In summary, heat adaptation of the elite synthetic derived lines appear to be defined by intercepting more light through early vigorous growth; as well as expressing higher radiation use efficiency (RUE) which was reflected in faster growth and more biomass, higher Photochemical Reflectance Index (PRI), and cooler canopies. This last physiological condition enables a larger number of grains to be set, as well growth of taller stems with a greater capacity for storage of water soluble carbohydrates, which contributed significantly to increased kernel size. Evidences for the utility of wild relatives in plant breeding for a warmer climate were reinforced in this study.