I. Methods for breeding high-protein cultivars of soybeans; II. Transfer of Phytophthora resistance in soybean [Glycine max (L.) Merr] by backcrossing

The need to find an effective breeding method to develop soybean cultivars with high yield and high protein percentage from crosses of adapted cultivars is important. The objective of this study was to determine which kind of method (single cross vs backcross) would offer the best opportunity to increase yield of Vinton 81 while maintaining its current level of protein percentage. Three crosses were made using a moderately high protein cultivar (Vinton 81) with three high-yielding cultivars of different maturity group. The F(,4)-derived and BC(,1)F(,3)-derived lines were evaluated and compared with Vinton 81 for seed yield, maturity, lodging, height, seed weight, and protein and oil percentage;Significant differences were observed among lines derived from the F(,4) and BC(,1)F(,3) generations for the seven strains. In both generations, most of the lines were not significantly different from Vinton 81 for yield and protein percentage. Overall, only two lines were found that had greater yield and equal protein percentage to Vinton 81. Because the two superior lines identified came from the F(,4) generation, the single-cross method was favored over the backcross method in the development of productive soybean cultivars with high protein percentage;The efficiency of backcrossing in the transfer of Phytophthora resistance into susceptible cultivars was evaluated. A78-123018 and Cumberland were crossed to a resistant cultivar, Williams 82 and four backcrosses were made. The objectives of this study were to determine the number of backcross generations required to obtain Phytophthora resistant lines with the yield potential of the recurrent parent, and to determine in what backcross generation a composite of phenotypically similar lines could be made that would yield as much as the recurrent parent. Lines comprising the different generations were evaluated for yield and maturity in 1984;Significant variation among generations were observed for yield and maturity. Mean yields of the BC(,0) and BC(,1) generations were significantly lower than the mean yields of the BC(,2) and succeeding generations. Almost 100% of the lines from the BC(,2) and succeeding generations had yields equal to the recurrent parent. Comparable mean yield and maturity to the recurrent parent can be obtained from a composite of visually similar lines in the second backcross generation when a cultivar with acceptable yield is used as the donor parent