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Source-Sink Manipulation as a Postanthesis Stress Tolerance Screening Technique in Wheat

Dep. of Agronomy, Univ. of Georgia, Coastal Plain Exp. Stn., Tifton, GA 31793-0748
Dep. of Crop and Weed Sciences, North Dakota State Univ., Fargo, ND 58105

^* Corresponding author.

Success in developing wheat (Triticum aestivum L.) cultivars with improved postanthesis stress tolerance has been limited. Because stress environments are inherently erratic in nature, screening techniques that can be applied in low-stress environments would be valuable. Postanthesis source limitation was evaluated as a screening technique for postanthesis stress tolerance, under conditions of low plot replication and low within-plot sampling, in a set of 20 wheat genotypes that were previously shown to vary in postanthesis stress tolerance. Sink size reduction treatments, consisting of a 70% postanthesis surgical reduction of kernel number per spike, were applied in 1982 and 1983 at Fargo and Prosper, ND. The relative increase in kernel weight associated with kernel number reduction treatments, as compared with control treatments, was used to estimate the degree of postanthesis source limitation (SR). Significant variation in SR occurred among environments and among genotypes, but genotype x environment interaction was nonsignificant. Kernel growth was limited an average of 16.4% (genotypic range 7.1–41.5%) by postanthesis source. Variability associated with the technique was high, perhaps due to confounding genotypic effects independent of any stress response. Degree of postanthesis source limitation to kernel growth was not correlated to postanthesis stress tolerance indices determined for this set of genotypes. Determination of postanthesis source limitation does not appear to be a usable technique for routine screening of diverse wheat germplasm for postanthesis stress tolerance due to poor precision, relatively high resource allocation requirements, and a poor association of source limitation and stress tolerance across a wide range of genotypes.

Received for publication February 8, 1990.