AGRONOMIC PERFORMANCE OF SOYBEAN LIPOXYGENASE ISOLINES

Lipoxygenases (EC 1.13.11.12) are enzymes that catalyze the hydroperoxidation of polyunsaturated lipids. In soybean [Glycine max (L.) Merr.] seeds, these lipid hydroperoxides are converted to volatile compounds associated with undesirable flavors. On the other hand, lipoxygenases may be involved in plant growth and development, senescence, and pest resistance, and, while the genetic removal of soybean seed lipoxygenases might enhance soybean product quality, agronomic quality might be deleteriously affected. Mutant alleles exist for the three soybean seed lipoxygenase isozymes that genetically eliminate each lipoxygenase function. This study compared a set of 10 Lx1Lx1-lx1lx1 isolines for agronomic performance, and determined in 'Century' isolines the effect of lipoxygenase removal on pod and stem blight (Phomopsis longicolla Hobbs) fungal infection of seeds. Substituting the null allele lx1 for the competent allele Lx1 had no deleterious effects on soybean yield in four environments. Lodging, height, seed weight, and seed oil and protein concentrations were unaffected. Maturity differed significantly, but only by 1 d. In 1988, only Century isoline L2-3, lacking lipoxygenase 2, had a higher level of P. longicolla seed infection than Century, and in 1989 only isoline L2L3-2-4, lacking lipoxygenases 2 and 3, had a significantly higher level. Production of soybean genotypes with reduced embryo lipoxygenase levels should not be more severely affected by pod and stem blight disease than genotypes containing all embryo lipoxygenases.