Repeatability and genotype x environment interaction of coleoptile length measurements in winter wheat

Coleoptile length is often associated with fall stand establishment in winter wheat (Triticum aestivum L.). While coleoptile length evaluation and improvement is a common objective of wheat breeding programs, little information is presently available to guide effective evaluation efforts. The objectives of this study were to assess the association between kernel and test weight and coleoptile length, to determine the inherent precision of a coleoptile length screening procedure through repeatability analysis, and to assess the presence and nature of genotype x environment (G x E) interaction for coleoptile length. Seed samples from 45 winter wheat genotypes planted in a randomized complete block design at four locations in the 1994-1995 growing season were used to evaluate G x E interaction. A subset of samples of 15 lines from two contrasting environments (Selby, high kernel and test weight; Winner, low kernel and test weight) were used to estimate repeatability (R) from five repeated measurements of the same seed sample. Analysis of variance revealed highly significant (P < 0.01) G x E interactions for coleoptile length measurements from seed samples from the four locations. Spearman rank correlations between genotype means at the four environments were highly significant (r(s) = 0.93-0.95; P < 0.01), suggesting that G x E interactions were caused by differences in scale among environments and not by differences in genotype rankings among environments. Estimates of repeatability of coleoptile length measurements were high and not significantly different between samples from the two contrasting environments (Selby: R = 0.67 +/- 0.10; Winner: R = 0.63 +/- 0.11). Our results suggest that coleoptile length is a moderately heritable trait and that seed source for coleoptile length measurements has little or no effect on coleoptile length expression or the variation experienced with the evaluation procedures.