Desiccation Tolerance and Its Relationship to Assimilate Partitioning in Winter Wheat

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Abstract
Winter wheat (Triticum aestivum L.) is frequently subjected to stress that causes early senescence of plants and cessation of grain filling. This research evaluated chemical desiccation for selecting genotypes for tolerance to postanthesis stress and determined the relationship of chemical desiccation tolerance to carbohydrate and N partitioning. Twenty‐eight cultivars with a wide range of stress tolerance and yield potential were treated with 0 and 0.19 mol L‐1 NaCIO3 14 d after anthesis. The 2‐yr study was on a Eudora silt loam (coarse‐silty, mixed, mesic Fluventic Hapludoll); treatments were in randomized‐complete blocks with four replications. Ten cultivars representing a range of treatment responses were evaluated further at two locations on dryland and irrigated Eudora silt loam and Pratt loamy fine sand (sandy, mixed thermic Psammentic Haplustalf) in split plots with three replications. Cultivars that had high kernel weights and early release dates were generally more tolerant of chemical desiccation than cultivars with low kernel weights and recent release dates. Grain yields of chemically desiccated plants under irrigation correlated significantly with yields of untreated plants at one location but not at another location. Losses of dry matter and soluble carbohydrates, but not of N, from stems were related to grain yield response to chemical desiccation. We concluded that chemical desiccation effectively selects for postanthesis stress resistance, and that combining high carbohydrate reserves with efficient translocation to the grain should improve wheat performance in unfavorable environments.