No abstract

Soybean [Glycine max (L.) Merr] is an important agronomic crop around the world, used largely for animal feed. However, ∼75% of the phosphorus (P) in soybean grain is in the form of phytic acid (PA) or phytate, the cation salt form of PA, which cannot be digested by monogastric and agastric animals including swine, poultry, and aquacultural animals, leading to decreased field efficiency and environmental detriment due to P runoff. Soybean lines have been developed with a reduced PA content using mutant alleles of three genes involved in the PA pathway: either the combination of lpa1 and lpa2 or mips1. However, the relationship among these alleles was unknown. This study was conducted to explore the impact of these three mutant alleles on soybean agronomic, seed quality, and seed composition traits. A population consisting of 30 recombinant inbred lines developed from a cross between V03‐5901 (mips1) × 04‐05N32 (lpa1/lpa2) was planted along with the parents at two locations in Virginia in 2014 and 2015. The results showed that (i) an additive relationship existed among the three different mutant alleles, resulting in lower PA content as more low‐PA (LPA) mutant alleles were added; (ii) the lines with lpa1 allele had the highest field emergence, and thus lpa1 may be a good trait with which to create a commercially viable LPA soybean cultivar; and (iii) the interaction between the mips1 and lpa2 alleles resulted in raffinose content significantly lower than with either allele on its own. The findings of this study provided breeders with references for developing LPA soybean cultivars combined with other desirable traits.

Low phytic acid (LPA) soybean [Glycine max (L.) Merr] genotypes reduce indigestible PA in soybean seeds in order to improve feeding efficiency of mono- and agastric animals, but often exhibit low field emergence, resulting in reduced yield. In this study, four LPA soybean varieties with two different genetic backgrounds were studied to assess their emergence and yield characters under 12 seed treatment combinations including two broad-spectrum, preplant fungicides (i.e., ApronMaxx (mefenoxam: (R,S)-2-[(2,6-dimethylphenyl)-methoxyacetylamino]-propionic acid methyl ester; fludioxonil: 4-(2,2-difluoro-1,3-benzodioxol-4-yl)-1H-pyrrole-3-carbonitrile) and Rancona Summit (ipconazole: 2-[(4-chlorophenyl)methyl]-5-(1-methylethyl)-1-(1H-1,2,4-triazol-1-ylmethyl) cyclopentanol; metalaxyl: N-(methooxyacetyl)-N-(2,6-xylyl)-DL-alaninate)), osmotic priming, and MicroCel-E coating. Two normal-PA (NPA) varieties served as controls. Both irrigated and non-irrigated plots were planted in Blacksburg and Orange, Virginia, USA in 2014 and 2015. Results revealed that three seed treatments (fungicides Rancona Summit and ApronMaxx, as well as Priming + Rancona) significantly improved field emergence by 6.4–11.6% across all genotypes, compared with untreated seeds. Seed priming was negatively associated with emergence across LPA genotypes. Seed treatments did not increase the yield of any genotype. LPA genotypes containing mips or lpa1/lpa2 mutations, produced satisfactory emergence similar to NPA under certain soil and environmental conditions due to the interaction of genotype and environment. Effective seed treatments applied to LPA soybeans along with the successful development of LPA germplasm by soybean breeding programs, will increase use of LPA varieties by commercial soybean growers, ultimately improving animal nutrition while easing environmental impact.