INHERITANCE OF A LIPOXYGENASE-1 ALLOZYME IN SOYBEAN

Three soybean [Glycine max (L.) Merr.] seed lipoxygenase isozymes, inv olved in generating products which contribute to undesirable flavors i n processed protein products, have been characterized genetically. The objective of this study was to determine the inheritance of an altern ate lipoxygenase-1 allozyme, which has a more acidic isoelectric point than the normal allozyme (pl 5.79 vs. pI 5.85 for the normal allozyme ). This alternate allozyme was originally seen in soybean strains L2-3 and PI 86023, which are null for lipoxygenase-2, genotype lx2 lx2. A similar alternate allozyme was subsequently seen in 'McCall'. The 1:2: 1 F2 segregation ratios from several crosses of ''normal'' allozyme x alternate allozyme parents indicated codominant inheritance of the two allozymes. The gene symbol Lx1b is assigned to the allozyme with pl 5 .79, and the gene symbol for the allozyme with pI 5.85 becomes Lx1a. T his gives an allelic series at the lipoxygenase- 1 locus Lx1a, Lx1b, a nd lx1. The Lx1 and Lx2 loci are very tightly linked. Crosses between Lx1a Lx1a Lx2Lx2 and Lx1b Lx1b lx2lx2 genotypes would be designed to i ncorporate the lxlx2 genotype into cultivars with improved protein fla vor attributes for soyfood products. While phenotypes of Lx2Lx2 and Lx 2lx2 genotypes are indistinguishable in terms of lipoxygenase-2, the p resence of two electrophoretic bands for lipoxygenase-1 (Lx1a Lx1b) wh en the lipoxygenase-2 locus is also heterozygous makes it possible to identify individuals with the recessive lx2 allele. The selection of h eterozygotes can reduce the time needed to backcross the lx2 allele.