Identifying Morpho-Physiological Traits to Increase Wheat Yield in Semi-Arid and Sub-Humid Environments.

Wheat (Triticum aestivum L.) is grown under rainfed conditions in climates ranging from semi-arid to sub-tropical, thus being limited by diverse weather constraints. Adaptative morpho-physiological traits could possibly result in more consistent yields at regions where wheat is grown. Our objective was to quantitatively assess the winter wheat yield gain resulting from different altered morpho-physiological traits using a mechanistic crop simulation model coupled with agronomic management, soil, and long-term weather data. The SSM-Wheat crop model was ran for a period of 30 consecutive years at 68 locations within the winter wheat growing region of the U.S. southern Great Plains. Simulations were first carried out at each location-year using parameters developed for a standard wheat crop, and nine subsequent times altering one morpho-physiological trait at a time. Traits evaluated were limited transpiration rate at two thresholds of 2.4 and 3.7 kPa, depth of soil water extraction, rate of root development, rate of leaf area development (slow versus rapid), stomata closure (early versus late), and length of vegetative cycle. Limited transpiration rate with a threshold of 2.4 kPa increased grain yield in 12.2 g m^-2 (p<0.10) in semi-arid environments, with an average probability of yield gain of 0.91. Depth of soil water extraction, rate of root development, and length of vegetative cycle were neutral at most locations. Yield gain due to rapid leaf area development ranged from 13.8 to 32 g m^-2, depending on environment, and probability of yield gain was 0.89. Late stomata closure, which implies greater water depletion, showed a trend (p<0.2) of yield increments in moist sub-humid (15.2 g m^-2) and dry sub-humid (14.2 g m^-2) environments with a 0.59 probability of yield gain. Our research exposes different traits that positively affected winter wheat yields in sub-humid and semi-arid environments and could possibly be targeted by breeding programs.