Some Differences Between Soybean Cultivars Observed by Growth Analysis

Spaced plants of soybean (Glycine max (L.) Merrill) cultivars were subjected to classical growth analysis. Varietal differences in mean net assimilation rate (NAR), relative growth rate (RGR), relative leaf growth rate (RLGR), leaf area ratio (LAR), specific leaf weight (SLW), and shoot/root ratio (S/R) were detected within a group of 21 cultivars grown in three tests over 3 years. Only LAR and SLW differed within another group of 23 cultivars grown in 2 years. Comparisons of cultivars with their parents showed that selection for yield had resulted in increased NAR and SLW, and in decreased LAR, S/R, plant weight, and leaf area. Many of the cultivars were transgressive segregants for higher NAR and SLW and for lower LAR. Phenotypic correlations showed that NAR was highly correlated with SLW and inversely correlated with LAR. SLW might be a useful character for indirect selection of soybean yield.