Performance and Stability of Indeterminate and Determinate Soybean in Short‐Season Environments

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Abstract
In the traditional indeterminate (IND) soybean‐growing areas of North America, lodging in soybean [Glycine max (L.) Merr.] during the pod‐filling stages of reproductive growth can cause significant yield reductions. Maturity Group (MG) II to III determinate (DET) cultivars have recently been developed that combine excellent lodging resistance with high yield potential. This study was initiated to evaluate the performance and stability of DET soybeans in MG I to II growing areas. Fifteen IND and 15 DET lines from each of three crosses were evaluated in the F6 and F7 generations for four environments in narrow rows. In each environment, the IND lines, on average, were higher yielding, taller, had greater bottom pod heights, and were more susceptible to lodging than the DET lines. In one cross, the DETs and INDs had equivalent seed yields, whereas, in two crosses the INDs significantly outyielded the DETs, illustrating that certain genetic backgrounds favor the DET stem type. The genotype‐grouping technique identified high‐yielding stable DET lines, however, within each cross most of the lines in that category had an IND stem type. The overall results suggest that breeding for high‐yielding stable DET lines is possible in short‐season environments, but that the frequency of such lines in a population may be lower than the frequency of IND lines. Since yield of the DET stem type was generally positively associated with plant height and maturity, the stringent use of these selection criteria in early generations may provide a relatively simple way of increasing the frequency of favorable DET genotypes.
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