Evaluation of Field Emergence and Extended Cold Germination Testing of Advanced Soybean Lines From Two Sources of Low Phytate Germplasm Grown in 12 Environments.

The development of soybeans with reduced phytate and increased inorganic phosphorus levels has nutritional and environmental benefits, but poor germination and emergence presents breeding challenges.  Our initial objectives were to characterize genotype and environment effects on inorganic phosphorus and phytate levels in two sources of low phytate germplasm but reduced emergence of low phytate lines surfaced as a critical factor in the evaluation of low phytate germplasm.  The initial experiment evaluated three advanced lines derived from the CX1834 low-phytate germplasm, three advanced lines derived from V99-5089 (a proprietary Virginia Tech low phytate line) and two normal phytate checks at 6 locations in 2008 and 2009.  In 2010, seed from the 8 genotypes grown in 12 environments was evaluated in an extended cold germination test (ECGT) and in a replicated field emergence test in Warsaw, VA.  Genotype, environment, and genotype × environment interaction were significant (P < 0.05) in the ECGT and field emergence test.  The two tests were significantly correlated (r = 0.78) but the ECGT severely reduced germination as compared to the field test.  In the ECGT, environmental means ranged from 24% to 82% with only one environment above 80% germination compared to the field emergence test in which seed from seven environments averaged over 80% emergence.  In the ECGT, all the low phytate lines were significantly lower than the check cultivars but in the field emergence test one low phytate line was equal to the check cultivars.  In addition, four low phytate lines were not significantly different from each other averaging 71 to 76% emergence.  If seed germinated well in the ECGT then the field emergence was also good but bad germination in the ECGT was not always an indication of bad field emergence.  Therefore, the environmental conditions of the ECGT may be too severe to accurately predict emergence of LP lines in the field conditions of the Mid-Atlantic region.