Simultaneous Selection for Yield and Resistance to Brown Stem Rot of Soybean in Hill Plots1

Abstract

The yield of soybean [Glycine max (L.) Merr.] grown in row plots can be reduced by brown stem rot [caused by Phialophora gregata (Allington and Chamberlain) W. Gams]. Our objective was to evaluate the effectiveness of simultaneous selection among soybean lines for yield and resistance to brown stem rot in hill plots planted on soil infested with the causal organism. Ninety‐six random F4‐derived lines from an intermated population were grown in three replications of single, unbordered hill plots on four fields infested with P. gregata and on four uninfested fields. Selection for yield alone was not effective in identifying lines with a low percentage of stem browning. The correlation between yield and percentage of stem browning (r = −0.19) was not significant. Twenty‐three of the 48 lines with the highest average yield had below‐average resistance to brown stem rot. There was a high correlation for yield of the 96 lines on infested and uninfested soil (r = 0.80, P <0.01). When hill plots are used to determine the yield potential of soybean lines, resistance to brown stem rot should be evaluated independently by growing the lines on infested soil and splitting stems to determine the extent of infection. Evaluation of yield potential in hill plots can be done equally well on infested and uninfested soil.