variability in soybean agronomic performance traits in response to 41 C heat and high relative humidity seed stress
Incorporation of genetic diversity into soybean [Glycine max (L.) Merr.] cultivars can be used to increase yield and plant adaptation to stresses. Genetic variation has been found in commercial soybean cultivars, but using a seed stress to generate intra-cultivar variation has not been studied. The first objective of this study was to use seed stress in an attempt to generate variation in soybean agronomic traits of field stand, plant maturity, plant height, seed size, seed yield, seed protein content, seed oil content, seed standard germination and seed vigor. The second objective was to evaluate if changes in variation were heritable. Seed of two soybean cultivars, `BSR 101' and `Jack' were stressed using a modified version of the accelerated aging protocol, at 41°C for 48 hours, after which seeds immediately were hand-planted in the field near Ames, Iowa. Heritability of agronomic traits in the second generation was measured in two growing seasons, and at two locations, near Ames, Iowa, and Missouri Valley, Iowa. In 2010, cultivars exhibited increased variance and a mean increase in seed yield in response to the seed-stress treatment. In second generation plots variance did not change for all traits, but both cultivars had a mean increase in plant stand. In 2011, variance did not change for all traits in response to seed stress, but mean values decreased in all traits. In the second generation plots, there was a mean increase in plant stand and seed yield, but variance did not change. Results were subject to genotype by environment interactions, causing differences between growing seasons and cultivars. We found increase variation, large ranges in the agronomic trait values within treatments, and increased performance of agronomic traits in response to a seed stress treatment. This treatment can therefore be used to induce variation, which will aid in selection of superior plants from within already established soybean cultivars, to improve yield and other agronomic traits.