Inheritance and correlations of seed phytic acid, minerals, and agronomic traits in soybeans

Soybeans are highly desired for both their protein and oil contents; however, they contain phytic acid (PA), 1, 2, 3, 4, 5, 6 hexakis (dihydrogen phosphate) myo-inositol, an anti-nutritional seed component which reduces the bioavailability of nutritionally important minerals such as zinc, causing interest in the phytate:zinc (PA:Zn) molar ratio. Eight F$\sb2$-derived soybean populations were produced from crosses of cultivars with high (Pando and Dioux) and low (Cumberland, Lincoln, and Wells II) PA. The F$\sb3$ (1987) and F$\sb4$ (1988) generations were evaluated for seed PA, phosphorus, and zinc contents, the PA:Zn molar ratio, yield, maturity, germination percentage, and seedling vigor. The low PA parents were generally lower in PA, phosphorus, and zinc contents and higher in yield, germination, and seedling vigor than the high PA parents. No consistent differences were observed among the high PA and low PA parents for PA:Zn, which ranged from 33:1 for Sioux to 42:1 for Pando. Over both years, the population means differed significantly only for phosphorus, yield, maturity, and germination percentage. Population means were comparable to their respective midparent values for most of the traits, consistent with a hypothesis of additive gene action. Significant differences among lines for PA and yield occurred mainly in the low PA x high PA populations. The majority of the transgressive segregates for PA and PA:Zn occurred in the low PA x low PA populations with the lowest line in this study having a PA:Zn molar ratio of 26:1. Broad-sense heritability estimates were generally less than 0.30 for most traits in the low PA x low PA populations. Heritability estimates of 0.30 to 0.60 were observed in the low PA x high PA populations for phytate and yield; thus, selection for lower phytate or higher yield may be possible. Most phenotypic correlations between PA and phosphorus ranged from 0.41$\sp*$ to 0.58$\sp{**}$, suggesting that selection for low phosphorus could indirectly lead to low PA. PA was negatively correlated with yield and seedling vigor in the low PA x high PA populations. Thus, selection for low PA could indirectly lead to increased yield and seedling vigor. Based on the line values for PA and PA:Zn in this study, selection for lower PA would not necessarily result in the lower PA:Zn