Adapting wheat to stressful environments: Identifying key transpiration efficiency components reducing day-time water loss and heat stress linked to yield

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The overall goal of the partnership is to provide breeders with more specific selection criteria to more quickly release new cultivars which can better withstand multiple stresses (drought and heat stress) and which have greater yield stability. This directly supports our two cash funding partners, Sask Wheat and the Alberta Wheat & Barley Commission (AWC). SaskWheat aims to reduce environmental impact to enhance wheat producers' profitability, and AWC seeks to improve grain yield in normal and abiotic stress situations. In the prairies, climate is expected to continue to be more hot and dry with extreme weather events. In the field, drought stress is normally accompanied by heat stress and the combination of drought and heat stress is more common and six times more costly than each stress alone (Lamaoui et al. 2018; Mittler 2006). However, few if any studies have combined both drought and heat stress in the field on any crops. This project will establish a unique high tunnel field facility examining both drought and heat stress in a factorial combination (3 levels of drought stress × 3 levels of heat stress). The key plant response of Transpiration Efficiency (TE) is broadly defined as biomass produced per unit water transpired and essentially integrates the 90 collective traits identified by Casadebaig et al. (2016) in wheat. Our comprehensive study will examine: 1) shoot/leaf/rachis architecture/ultrastructural characteristics, 2) aquaporins and 3) cuticular waxes controlling TE at 10 days pre-anthesis through to the end of grain filling. The parameters investigated will primarily target those phenotypic and physiologic responses demonstrated to have a high heritability index and/or have been linked to grain yield. Hyperspectral imaging will also be incorporated to advance high throughput analysis linked to key traits (see Hein et al. 2021 for a review). Finally, both Night-Time and Day-Time TE parameters will be integrated to identify those common Day and Night Time factors which significantly increase TE under stress and are linked to yield resilience to both heat and drought stress through this physiological breeding approach.