Chemical desiccation tolerance and nonstructural carbohydrate dynamics in winter wheat

Contact chemical desiccants have been proposed as a means of identifying genotypes with the ability to support grain filling from stem nonstructural carbohydrates (NSC) in the absence of photosynthesis during grain filling. The objectives of this study were (1) to characterize chemical desiccation response, dryland yield performance, and NSC concentration and remobilization of F2:4 lines, (2) determine associations among chemical desiccation injury, dryland performance and NSC measurements, and (3) estimate genotypic variance components of agronomic traits and NSC measurements under chemical desiccation. F2:4 lines were planted in a split-plot with two replicates in 1998 and 1999 under irrigation at Fort Collins. Sodium chlorate (NaClO 3, 2% W:V, 125 mL m-2) was applied to subplots 15 d postanthesis. Lines were also evaluated at four dryland locations in an RCBD with two replicates. Yield injury from chemical desiccation ranged from 13 to 37% among entries, with reductions in both kernel weight (13 to 23%) and kernel number (8 to 32%). Significant associations were observed between grain yield injury and both biomass injury (r = 0.65, P < 0.05) and control kernel weight (r = 0.57, P < 0.05). Grain yield under dryland conditions was not associated with either grain yield injury or kernel weight injury under chemical desiccation. Significant genotypic variance was observed for most traits examined. Inconsistency among entries for desiccation tolerance, and the lack of correlation between desiccation tolerance and dryland performance, suggest that additional research is necessary to identify strategies and techniques to successfully exploit the chemical desiccation method. NSC concentration was determined from stem samples collected 14 d postanthesis and at maturity. Significant variation among entries was observed for NSC concentration in both control and desiccated treatments. Stem NSC concentration at postanthesis was positively correlated (r = 0.90, P < 0.001) with NSC remobilization during grain filling in the desiccated treatment, suggesting that the size of the NSC pool available at the onset at grain filling is important for reserve remobilization. Most correlations among yield components and variables related to stem NSC were not significant. Genetic variance estimates indicated that high genetic variance should provide progress to improve NSC parameters in the populations.