Introgression of Genes for Small Seed Size from Glycine soja into G. max
Soybean [Glycine max (L.) Merr.] cultivars with a seed weight of <100 mg seed−1 are preferred for some food products. The wild species Glycine soja Sieb. & Zucc. has a seed weight of <30 mg seed−1, but undesirable agronomic characteristics prevent its direct use in commercial production. The feasibility of transferring the genes for low seed weight from G. soja into high-yielding cultivars of G. max through backcrossing was studied. For three G. max ✕ G. soja crosses, selection between backcross generations for low seed weight was compared with no selection during backcrossing. For each cross, 40 F2-derived lines from each backcross generation from the BC0 to BC3 were evaluated in two replications at two locations for seed weight, seed coat color, lodging, petiole retention, and maturity. Selection resulted in backcross progeny with smaller seed weights than those obtained from backcrossing without selection. Of the BC3F2-derived lines, 37% had seed weights of ≤100 mg seed−1 in the populations obtained by selection, compared with 18% of those obtained without selection. From each cross, BC3F2-derived lines were evaluated for yield. An average positive correlation of 0.44 was found between seed weight and yield among selected populations and 0.54 among unselected populations. Up to 89% of the yield of the recurrent parent was exhibited by lines with seed weights of 100 mg seed−1 or less.
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