Heterosis and Inbreeding Depression in Glycine max

Abstract

This study focused on soybean heterosis in regard to yield, seed size, and height and consisted of three objectives: (1) to study three new hybrids and retest a fourth hybrid for heterosis, (2) to study the correlation between heterosis in the F2 generation and inbred line variance, (3) to find SSR markers that help to explain heterosis in a heterotic hybrid. Objective one was evaluated in 2007 and 2008. The four hybrids were tested in yield trials that consisted of F1 - F4 generations and parents. Results showed some heterosis, but there was a lack of consistency across years due to a genotype by year effect. The second objective was evaluated in 2008. Yield trials examining six populations were tested over three locations. The hybrid seed were developed in 2007 and F1 plants were grown to generate F2 bulks, the inbred lines were developed by single seed descent and tested as F6:8 lines. A correlation between heterosis and transegregate lines was found for yield and seed size. For the third objective to identify SSR markers for heterosis, the cross of Hutcheson x Holladay was used to develop F2:3 and F2:4 lines. A DNA sample was taken from 360 individual F2 plants and screened with 40 polymorphic markers that represented each arm of the 20 linkage groups. Yield, seed size and height were taken on the F2:3 and F2:4 lines and used to evaluate the marker data. No consistent marker for additive and dominance variance was found between the generations.