TRANSGRESSIVE SEGREGATION FOR PALMITIC ACID IN SEED OIL OF SOYBEAN

Palmitic acid is the major saturated fatty acid in soybean [Glycine max (L.) Merr.] oil. Reducing levels of palmitic acid should enhance the nutritive value of soybean oil for human consumption. The low palmitic acid strain C1726 (81 g kg(-1) 16:0), carrying the fap1 allele, was crossed with two strains developed independently of C1726, N79-2077-12 and N90-2013, both with about 60 g kg(-1) 16:0. Progenies from these crosses were evaluated to determine genetic relationships controlling palmitic acid in these two groups of strains. Palmitic acid concentrations in the oil of F-2 seeds, F-3 seeds on F-2 plants, and seeds from F-3 families were determined by gas chromatography. Transgressive segregates averaging 44 and 96 g kg(-1) 16:0 were identified in the segregating populations. Both F-2 plants and F-3 families were identified that were either homozygous or heterozygous for loci controlling palmitic acid. Chi-square analyses for a 1 homozygous P1 type/1 homozygous P2 type/1 homozygous recombinant type (high 16: 0)/1 homozygous recombinant type (low 16:0)/12 plants or families heterozygous at either locus demonstrated that two loci controlling levels of 16:0 were segregating in these populations. A correlation coefficient of 0.97 calculated between palmitic acid values of homozgous F-2 plants and their F-3 family means demonstrated that the homozygous classes were true breeding for palmitic acid. The locus in C1726 was fap1; the other locus, in N79-2077-12 and N90-2013, has not been designated. These populations provide additional sources of low palmitic acid to enhance the nutritional value of soybean oil.