EFFECT OF GROWTH HABIT ON YIELD COMPONENTS OF LATE-PLANTED SOYBEAN

Late-planted soybean [Glycine mau (L.) Merr.] yields are usually lower than fun-season soybean yields. Indeterminate growth habit may be sup erior to the traditional determinate growth habit for late planting in the southeastern USA. The objective of our study was to determine the effect of determinate and indeterminate growth habit genes on yield c omponents of late-planted near-isogenic lines of soybean. Twenty-three determinate and 23 indeterminate near-isogenic lines (near-isolines) of soybean from three populations were compared in the field at Brewto n, Tallassee, and Shorter, AL, in 1991 and 1992. Determinates had lowe r lowest-pod heights, more mainstem branches per plant, and more two-s eeded pods than indeterminates. Growth habit did not affect total pods per plant, mainstem or branch pods per plant, seeds per plant, seed m ass, or number of three-seeded pods per plant. The growth habit x popu lation and growth habit x location interactions were significant for m ost traits, but the growth habit x year interactions were nonsignifica nt or small. Number of mainstem pods was the only yield component corr elated with yield (r = 0.36*). we conclude that (i) growth habit gene s have little consistent effect on most yield component traits, (ii) g rowth habit effects are site- and population-specific in the southeast ern USA, and (iii) seed yield is not correlated with yield component t raits in late-planted soybean.