Selection for yield, protein, and oil in soybean crosses between adapted and introduced parents

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Soybean [ Glycine max (L.) Merr.] breeders can sometimes increase genetic variability in their germplasm through wide crosses with plant introduction (PI) material, and in that way lead to slow progress in developing high-yielding cultivars. A study was conducted to evaluate the potential of crosses of adapted × introduced soybean lines for improving yield and protein and oil concentrations. Five soybean cultivars adapted to South Dakota were crossed in selected combinations with four PI lines to develop F 3-derived lines. The adapted and PI lines were selected for wide variation in protein and oil concentration. Thirty F 3:5 lines and parents from each of eight different crosses, including two adapted × adapted, were evaluated in a replicated group balanced block experiment. Significant genetic variability for yield occurred among progenies of two adapted × PI crosses, and for protein and oil concentrations among progenies of two adapted × PI crosses. No significant genetic variability for any trait was found among progenies of adapted × adapted crosses. Progenies of adapted × adapted crosses generally yielded more seed and had higher oil concentrations than those from adapted × PI crosses. PI parents with high trait expression produced populations with high expression for that trait, and combined better with some adapted parents than with others. With single-trait selection, simultaneous improvement of yield and oil concentration was more successful than for yield and protein concentration, or for protein and oil. Increases in the sum of protein and oil concentrations were small, and were achieved through increased protein concentration. In addition to measuring the trait of interest before crossing with PI lines, it seems that genetic variability of populations and combining ability of adapted parents should be determined. Relationships of yield, protein, and oil should be determined for each cross, even if only one trait is of interest in the selection program.