Methodology for Evaluation of Chemical Desiccation Tolerance in Winter Wheat

Abstract

Postanthesis drought stress is a persistent problem for winter wheat (Triticum aestivum L.) production throughout much of the Great Plains of the USA. Chemical desiccation has been proposed as a method for improving postanthesis drought stress tolerance by identifying genotypes that support grain growth from nonstructural carbohydrates stored in the stems. The objectives of this study were to define cultivar responses to different chemical desiccants and dates of desiccant application and examine grain filling and stem dry weight loss patterns to assess the suitability of chemical desiccation as a screening method for postanthesis drought stress tolerance. In the first year of the study, 10 field-grown winter wheat cultivars were subjected to chemical desiccation with 2% sodium chlorate (NaClO3), 0.15% potassium iodide (KI), and 0.30% KI at 10 and 15 days postanthesis (DPA). Chemical desiccation 10 DPA induced significantly (P≤0.01) greater desiccation injury (for grain yield and its components) than chemical desiccation 15 DPA. Levels of desiccation injury were similar for NaClO3 and 0.30% KI, whereas the 0.15% KI treatment did not induce yield or yield component reduction. The second year of the study included evaluation of stem and grain dry weight changes following chemical desiccation. Chemical desiccation resulted in apparent reduction in grain filling rates and increased stem dry weight losses during grain filling. Cultivars that were more tolerant of chemical desiccation demonstrated increased stem dry weight immediately after anthesis and subsequent increased rates and amounts of stem dry weight loss during grain filling.