Use of Irrigation in Selection for Soybean Yield Potential under Drought
The impact of selection in irrigated environments on improving seed yield in drought environments has not been extensively researched in soybean [Glycine max (L.) Merr.]. Our objectives were to evaluate cultivar × irrigation interaction, its impact on selection for yield in drought environments, and drought tolerance in soybean: drought tolerance being defined as better relative yield ranking in drought environments than in nondrought environments. Seven data sets were obtained from Arkansas trials of Maturity Group V cultivars. Each contained data from irrigated and nonirrigated trials from one location from two consecutive years with drought. Significance of genotype × irrigation interaction was determined for each set along with heritability of yield in both irrigation treatments and the genetic correlations of irrigated and nonirrigated yield from one year with nonirrigated yield in the other year. Rank correlations and crossover interactions between irrigation treatments were analyzed. The effect of selection in both irrigation treatments on yield in drought environments was simulated. Genotype × irrigation interaction was significant in six data sets. Entry-mean heritability was higher in the irrigated trials (0.74) than in nonirrigated trials (0.37). Rank changes between irrigated and nonirrigated treatments rarely consisted of large yield differences. The genetic correlations of yield from irrigated and nonirrigated trials from one year with yield from nonirrigated trials in another year were nearly equal. The results indicated that selection from irrigated trials would improve yield in drought environments better than selection from nonirrigated 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 tolerant cultivars. Nonirrigated trials may be useful in identifying a few unadapted cultivars.
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