Isolation of high seed inorganic P, low-phytate soybean mutants

Phosphorous in soybean [Glycine max (L.) Merr.] seed is stored primarily as phytic acid, which is nutritionally unavailable to nonruminant livestock. The objective of this study was to isolate mutations that reduce soybean seed phytic acid P and increase seed inorganic P. Following treatment with ethyl methanesulfonate, M2 through M6 plants were screened for high seed inorganic P. Seeds of M2 plants high in inorganic P produced progenies high in inorganic P through the M6 generation. M6 progenies of one plant averaged 6.84 g kg(-1) seed phytic add and inorganic P varied from 2.34 to 4.41 g kg(-1) or 60 to 66% of phytic acid P plus inorganic P. M6 progenies of a second plant averaged 10.89 g kg(-1) phytic acid and varied from 1.21 to 3.84 g kg(-1) inorganic P, representing from 47 to 51% of the sum of phytic acid P plus inorganic P. In contrast, nonmutant seeds of the check cultivar Athow contained 15.33 g kg(-1) phytic acid and averaged 0.74 g kg(-1) inorganic P, representing 15% of the sum of phytic acid P plus inorganic P. Low phytic acid and high inorganic P in these progenies should Increase the nutritional value of soy meal and reduce excess P in livestock manure.