Genetic improvement of seedling emergence of low-phytate soybean lines
Reduced seedling emergence of low-phytate (LP) soybean [Glycine max (L.) Merr.] lines with the pha1 and pha2 alleles has been a limiting factor in the development of LP cultivars. Crosses between normal-phytate (NP) and LP soybean lines have produced progeny with improved emergence. The objective of this study was to determine if LP lines with improved emergence are capable of producing progeny with equal or higher emergence when crossed to NP parents. Low-phytate lines with improved emergence were crossed to NP cultivars and the LP progeny were evaluated with seed produced at three 2007 locations and five 2008 locations. A field test of the lines was conducted in 2008 with one 2007 seed source. An extended cold test (ECT) was developed to evaluate all the lines with the three 2007 seed sources and selected lines and parents with the five 2008 sources. There were LP progeny with significantly less emergence than the LP parent when evaluated in the field and with the ECT. One single-cross line had significantly greater emergence than the LP parent and emergence equal to the NP parent. Genetic variation among the single-cross and backcross lines was attributed to the segregation of favorable and unfavorable alleles for emergence from both the NP and LP parents. Multiple seed sources should be used to identify LP lines with superior emergence based on field evaluations or the ECT.