USE OF IRRIGATION IN SELECTION FOR SOYBEAN YIELD POTENTIAL UNDER

The impact of selection in irrigated environments on improving seed yi eld in drought environments has not been extensively researched in soy bean [Glycine max (L.) Merr.]. Our objectives were to evaluate cultiva r x irrigation interaction, its impact on selection for yield in droug ht environments, and drought tolerance in soybean: drought tolerance b eing defined as better relative yield ranking in drought environments than in nondrought environments. Seven data sets were obtained from Ar kansas trials of Maturity Group V cultivars. Each contained data from irrigated and nonirrigated trials from one location from two consecuti ve years with drought, Significance of genotype x irrigation interacti on was determined for each set along with heritability of yield in bot h irrigation treatments and the genetic correlations of irrigated and nonirrigated yield from one gear with nonirrigated yield in the other year, Rank correlations and crossover interactions between irrigation treatments were analyzed. The effect of selection in both irrigation t reatments on yield in drought environments was simulated, Genotype x i rrigation interaction was significant in six data sets. Entry-mean her itability was higher in the irrigated trials (0.74) than in nonirrigat ed trials (0.37), Rank changes between irrigated and nonirrigated trea tments rarely consisted of large yield differences. The genetic correl ations of yield from irrigated and nonirrigated trials from one year w ith yield From nonirrigated trials in another year were nearly equal. The results indicated that selection from irrigated trials would impro ve yield in drought environments better than selection from nonirrigat ed trials. Drought tolerant reactions occurred in only 16% of the two- cultivar comparisons. While several cultivars appeared tolerant, their yield in drought environments was not superior to several less tolera nt cultivars. Nonirrigated trials may be useful in identifying a few u nadapted cultivars.