Correlated Truncation Selection for Yield in Soybeans¹

Abstract

Random genetically heterogeneous, F 2 ‐derived maternal lines and genetically homogeneous, F 5 ‐derived daughter lines of two soybean crosses were evaluated for nine characters in three environments in the F 0 ‐F 7 generations. Heritability was relatively consistent across environments for all traits except seed yield. For yield, heritability was greatest under favorable growth conditions and least when moisture stress was alleviated by irrigation. Variability over environments in correlations of all traits with yield was related largely to the degree of moisture stress in each environment. Crosses revealed similar magnitudes of correlation with yield for all traits except chemical composition. This was related to the chemical composition of parents used in these crosses. Correlations of early lodging with yield in genetically homogeneous lines were generally greater than for genetically heterogeneous lines. This was related to the relative uniformity of the plant canopy in these populations. Because of the inconsistency in character associations, predictions of yield advance from selection in any environment were inaccurate estimates of actual advance evaluated over environments. Selection of yield invariably resulted in maximum actual yield advance. Chemical composition was generally the best yield predictor for heterogeneous lines, while early lodging was the most effective trait for correlated yield selection in genetically homogeneous lines.