HYBRID SOYBEAN SEED PRODUCTION - COMPARISON OF 3 METHODS

Improved methods to produce hybrid soybean [Glycine mar (L.) Merr.] se ed could augment several types of research. Two previously described m ethods, the traditional method and the dilution method, require insect -facilitated cross-pollination of ms ms nuclear male-sterile plants. T he traditional method requires it substantial time investment during f lowering to remove fertile siblings, and the dilution method requires a substantial amount of land and pollen-parent seed. Because time, lan d, and seed are limited, a more efficient method would be valuable. Th e cosegregation method was developed, utilizing close genetic linkage between the W1 locus and the Ms6 locus. The W1_ seedling has a purple hypocotyl; the w1 w1 seedling has a green hypocotyl. The ms6 ms6 plant is male sterile and female fertile. Approximately? 97% of the purple- hypocotyl seedlings, W1_, in a line segregating for the w1 and ms6 all eles in coupling phase will be fertile, Ms6_, and can be removed as a pollen source at the first-trifoliolate stage. Our objective was to ev aluate and compare the three methods of hybrid soybean seed production for seed yield, efficiency, and hybrid seed purity and quality. We us ed a randomized complete-block design (three replications per location , three locations, two years). The cosegregation method gave higher se ed yield, better efficiency, and equal or better seed quality (percent age germination, 100-seed weight) than the other methods. Male-sterile plants yielded an average of 28.6 seeds plant(-1) with the cosegregat ion method, 18.2 seeds plant(-1) with the traditional method, and 9.5 seeds plant(-1) with the dilution method. The cosegregation method wil t be useful in several research areas, including genetic control of co mplex traits, prediction of parental value, recurrent selection, and c ommercialization of hybrid soybean.