GROWTH AND DEVELOPMENT OF SOYBEAN ISOLINES THAT DIFFER FOR MATURITY

Isolines for maturity within a common background may be useful in rese arch that attempts to determine the effect of maturity group adaptatio n on soybean [Glycine max (L.) Merr.] growth or yield, Although the ef fects of maturity genes on soybean phenology have been studied extensi vely, little is known about their effects on other soybean characteris tics. Field experiments were conducted near Columbia, MO, in 1991 and 1992 to determine the effects of three major maturity genes on growth and development of soybean. Four near-isogenic strains (isolines) were replicated four times in a completely randomized design: L71-920 (e(1 )e(2)e(3)), Clark (e(1)E(2)E(3)), L74-441 (E(1)E(2)e(3)), and L67-1474 (E(1)E(2)E(3)). Vegetative and reproductive characteristics were reco rded for five plants within each plot. Late-maturing Isolines were tal ler and had more leaves than early-maturing isolines, but stem growth and leaf initiation rates were similar. Late-maturing isolines produce d more flowers and pods because they had more nodes than early-maturin g isolines. Late-maturing isolines produced more than 25% of total yie ld on branches, whereas early-maturing isolines produced approximately 10% of total yield on branches. Because the isolines used in this stu dy had consistent differences for plant phenology, they can be useful components of experiments that include maturity as a factor. However, changes in phenology also changed plant morphology.