Brief communication. Genetic relationships between loci for palmitate contents in soybean mutants

Elevated palmitate content in soybean [Glycine max (L.)] oil may be important for the production of some food and industrial products. The palmitate content of commercial cultivars is approximately 11.0%. Soybean mutants with elevated and reduced palmitate have been developed. Elevated palmitate in J10 (o15.6%) and C1727 (o17.3%), and reduced palmitate in C1726 (o8.6%) were controlled by sop2, fap2, and fap1, respectively. The genetic system for elevated palmitate in KK7 (o13.5%) was unknown. Reciprocal crosses were made as Bay 3 J10, Bay 3 C1727, Bay 3 KK7, C1727 3 J10, C1726 3 J10, J10 3 KK7, C1727 3 KK7, and C1726 3 KK7 to determine if the sop2 allele in J10 was different from fap2 and fap1, and if the allele in KK7 was different from those of sop2, fap2, and fap1. No maternal effect was observed in any of the crosses. The phenotypic segregation ratio and the genotypic evaluation of F2 plants from C1726 3 J10, J10 3 KK7, C1727 3 KK7, and C1726 3 KK7 indicated that the sop2 allele in J10 was at a different locus from fap1, and that the allele in KK7 was at a different locus from sop2, fap2, and fap1. The lack of transgressive segregation in F2 seeds and their F2 plants with putative lower and higher palmitate content of C1727 3 J10 indicated that the sop2 allele was at the same locus as fap2. The sop2 allele in J10 was given the permanent designation of fap2 (J10) and the allele in KK7 was temporarily designated fapx. Lines with the fap2fap2fapxfapx genotype may provide important sources of elevated palmitate in soybean seed oil. The fatty acid composition of vegetable oils influences their use in industrial food applications. Commercial oil seed crops cannot satisfy all the demands of the food industry. The food industry may benefit from vegetable oils with unique fatty acid profiles (Rattray 1991). Alteration of the fatty acid composition of seed oil can be done in different ways (Robbelen et al. 1989). Although natural variability for these traits has been observed in most of the oilseed crops (Knowles 1989; Stefansson et al. 1961), natural genetic variability for palmitate content in commercial soybean (Glycine max L.) is limited (Rattary 1991). Therefore additional variability for this trait must be developed by mutagenesis, the recombination of different mutant genes, or genetic engineering (Ohlrogge et al. 1991). Palmitate is one of the two major saturated fatty acids of soybean oil that is important for the production of plastic fat products, such as shortening and margarine (Vles and Gottenbos 1989). The palmitate content of commercial cultivars is approximately 11.0%. Lines with elevated or reduced palmitate have been developed by different breeding techniques (Bubeck et al. 1989; Erickson et al. 1988; Fehr et al. 1991a,b; Wilcox et al. 1994). Erickson et al. (1988) found that the elevated palmitate content (o17.3%) of C1727 was controlled by fap2, while the reduced content (o8.6%) of C1726 was controlled by fap1. Fehr et al. (1991a) determined that the A21 line, with approximately 20.0% palmitate, had an allele (fap2-b) at the same locus as the fap2 or a tightly linked locus. Schnebly et al. (1994) crossed A24 with approximately 17.7% palmitate to the reduced palmitate lines C1726 (fap1; Erickson et al. 1988) and A22 (fap3; Fehr et al. 1991b), and found that A24 had an allele for elevated palmitate content at a locus independent of fap1 and fap3. The allele was given the permanent designation fap4. The mutant line J10, with approximately 15.6% palmitate, was developed at Saga University by X-ray irradiation of the seeds of Bay (Takagi et al. 1995). Rahman et al. (1996) temporarily designated the allele for palmitate in J10 as sop2 because it’s relationship to other alleles was unknown. Another mutant line, KK7, with approximately 13.5% palmitate was developed from a different M4 population of Bay. The genetic system of elevated palmitate in KK7 has not been determined. The objective of this study was to determine if the sop2 allele in J10 was different from fap2 and fap1, and if the allele in KK7 was different from those of sop2, fap2, and fap1.