Phosphorus partitioning of soybean lines containing different mutant alleles of two soybean seed-specifi c adenosine triphosphate-binding cassette phytic acid transporter paralogs

Seed phytate is a repository of P and minerals in soybean [Glycine max (L.) Merr.] seeds that limits P and mineral bioavailability for monogastric animals (e.g., humans, swine [Sus scrofa], and poultry [especially chicken, Gallus domesticus]) due to insuffi cient digestive tract phytase activity. We previously identifi ed epistatic recessive mutations affecting two paralogous adenosine triphosphate-binding cassette phytic acid transporter genes (one a nonsense mutation in Lpa1 and the other a missense mutation in Lpa2) as the molecular genetic basis in the ethyl methanesulfonate (EMS)-induced mutant low phytate soybean line M153. An additional mutant low phytate line, M766, contained one single nucleotide polymorphism within the ninth intron of the Lpa1 locus as well as a nonsense mutation in Lpa2. The objectives of this research were to clarify the genetics underlying the low phytate phenotype in line M766 and to determine P partitioning in new combinations of mutant alleles from M766 and M153. Inheritance of nonsense alleles affecting both low phytic acid (Lpa) genes (one from M153 and one from M766) led to the production of viable seeds that contained transgressive reductions in total seed phytate and signifi cantly higher levels of inorganic phosphate than has been reported for nontransgenic soybean material and will allow effi cient molecular selection of soybeans with even greater reductions of phytate for improved quality soybean meal.