Introgression of genes for small seed size from Glycine soja into Glycine max

Abstract

<p>Soybean (Glycine max(L.) Merr.) cultivars with a seed weight of less than 100 mg sd[superscript]-1 are preferred for some food products. The wild species Glycine soja Sieb. & Zucc. has a seed weight of less than 30 mg sd[superscript]-1, but its undesirable agronomic characteristics prevent its direct use in commercial production. The objective of the first study was to evaluate the transfer of genes for low seed weight from G. soja into high-yielding cultivars of G. max through backcrossing. For three G. max x 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. There were 37% of the BC3F2-derived lines that had seed weights of 100 mg sd[superscript]-1 or less in the populations obtained by selection compared with 18% of those obtained without selection. From each cross, BC3F2-derived lines were evaluated for yield. A significantly lower yield was exhibited by the selected population in only one of the three crosses. Among lines with seed weights of 100 mg sd[superscript]-1 or less, higher yielding lines were recovered from the selected populations of each cross. Up to 89% of the yield of the recurrent parent was exhibited by lines with seed weights of 100 mg sd[superscript]-1 or less;The objective of the second study was to determine the effectiveness of direct and indirect selection for small seed in three interspecific G. max x G. soja crosses based on seed weight and pod width measurements. Forty random BC2F2-derived lines from each of three crosses were evaluated for seed weight and pod width at two environments in Iowa and two environments in Puerto Rico. For each of the three crosses, direct and indirect selection for seed weight resulted in similar actual genetic gains. Selection in Puerto Rico was as effective as selection in Iowa. The results indicated that both direct and indirect selection for small seed are effective in the temperate and tropical environments that were studied.</p>