Agronomic Performance and Seed Inorganic Phosphorus Stability of Low‐Phytate Soybean Line TN09‐239

Phytate (myoinositol‐1,2,3,4,5,6‐hexa‐kisphosphate) in soybean (Glycine max (L.) Merr.) cannot be absorbed by livestock with monogastric digestive systems, and is often excreted in their waste. This can result in agricultural runoff pollution, as well as nutritional deficiencies in poultry (Gallus Gallus domesticus) and swine (Sus domesticus). The enzyme phytase is often applied to break the phytin‐salt bonds and allow for phosphorus (P) absorption, but is an added cost for animal producers. Therefore, we developed a low‐phytate BC4‐derived line TN09‐239 for comparison of agronomic and seed‐quality traits with the high‐yielding recurrent parent, 5601T. In a replicated, multienvironment field test in Tennessee, TN09‐239 was significantly higher for inorganic P (Pi) (P < 0.001), which is inversely correlated with the seed‐phytate concentration, but significantly lower for yield (P < 0.05) in comparison with the recurrent parent. These findings for increased Pi, but reduced yield, for TN09‐239 in comparison with 5601T were confirmed in the 2010 United States Department of Agriculture (USDA) Uniform Preliminary V Soybean Test grown in 10 southern US environments. 5601T and TN09‐239 differed in Pi stability across southern environments, with linear regression showing 5601T having stability across environments, while TN09‐239 showed variations based on the environments. However, in each environment TN09‐239 displayed nearly a 10‐fold increase in Pi compared to 5601T. Although the low‐phytate trait and much of the recurrent parent genome along with 85–90% of the yield have been captured, further backcrossing could help recover the remaining seed yield of 5601T and other traits desirable for southern US producers.