Selection for Cold Tolerance during Flowering in Short‐Season Soybean

Abstract

ABSTRACTCold temperatures during early reproductive development may result in reduced pod and seed formation in soybean [Glycine max (L.) Merr.]. The objectives of this work were to quantify cold tolerance of six potential parents, to screen breeding populations for cold tolerance, to search for associations between molecular markers and cold tolerance phenotypes, and to evaluate field performance of breeding lines. Six cultivars were evaluated for pod and seed set after exposure to 0 to 6 wk cold periods (15/5°C day/night), which began at flowering in growth cabinets. Evaluation at 6 vs. 2 wk following the end of a 3 or 6 wk cold period best discriminated between cold tolerant (CT) and cold sensitive (CS) cultivars. Two recombinant inbred line populations were cold stressed in growth cabinets with divergent selection performed over the F5 through F7 generations to select CT and CS lines. Bulked segregant analysis identified six chromosomal regions, four of which are related by homology, as potentially impacting the trait. Over 8 yr in the field at Ottawa, Canada, CT lines yielded 379 kg ha−1 more but matured 5.5 d later than CS lines without visual symptoms of cold damage. Following selection for early maturity, random lines from an additional four populations developed from a selected CT and CS line each crossed to another CT and CS parent were field tested in three environments. Cold tolerant × CT lines yielded about 8% more than CS × CS lines, again without visual cold damage symptoms.