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Quantitative trait locus mapping for resistance to heat‐induced seed degradation and low seed phytic acid in soybean

Jason D. Gillman, Kranthi Chebrolu, James R. Smith
Crop science 2021 v.61 no.3 pp. 2023-2035
Glycine max, backcrossing, bioavailability, climate change, cultivars, drought, early development, germination, germplasm, greenhouses, heat tolerance, inbred lines, introduced plants, marker-assisted selection, mutants, phosphorus, phytic acid, quantitative trait loci, seed quality, soybeans, water stress
Soybean [Glycine max (L.) Merr.] reproductive structures are temperature‐sensitive, with a reproductive optimum of 22 to 24 °C. Currently, parts of the US soybean growing region experience consistent late‐season drought stress, resulting in the adoption of agronomic practices that favor early maturity groups. This approach is the Early Soybean Production System and has boosted yields and on‐farm returns on investment. However, seeds produced under this system develop under higher temperatures than standard practices, and frequently have decreased seed quality, loss of value, and unacceptable germination rates. Climate change may result in more widespread late‐season drought and elevated temperatures during seed filling. The ancestors of all modern US high‐yielding soybean lines lack substantial resistance to heat‐induced seed degradation, but an unadapted plant introduction (PI 587982A) can maintain ∼95% quality and germination under the same conditions. Inconsistent germination and emergence defects are associated with increased bioavailable phosphorus and reduced phytic acid. To evaluate these traits’ interaction, a backcross recombinant inbred line population was developed, and emergence and germination were evaluated in seed produced in six greenhouse and field environments. Two mutant alleles (lpa1a and lpa2a) were linked to decreased germination and emergence; this effect was pronounced under elevated temperatures. A novel major‐effect heat tolerance quantitative trait locus derived from PI 587982A was identified and found to be associated with positive effects on overall germination and emergence. These results open the potential application of marker‐assisted selection for tolerance to elevated temperatures and may accelerate the development of germplasm and cultivars with high‐quality seed.