Base temperature of soybean primary root elongation varies among cultivars

Abstract

Soybean [Glycine max (L.) Merr.] is a sub-tropical crop which thrives in warm soils. In the Northern Great Plains, early spring seeding exposes soybean to cooler soil temperatures. Slower early-season development under cooler conditions may reduce competitiveness with adapted cool-season summer annual weeds, increasing yield loss risk from interference. Knowledge of critical temperature below which growth and development stops, referred to as “base temperature (Tb)” could help breeders develop soybean cultivars that can extend their roots into cooler soils in early spring and compete better with weeds. Our objective was to determine the base temperature for root elongation (TbRE) of ten divergent, commercial soybean cultivars grown in Manitoba. Seeds of each cultivar were incubated at 25 °C for 3 days to germinate. Germinated seedlings were transferred to growth pouches. The growth pouches were placed in 4 growth chambers each set to a different temperature (i.e., 15 °C, 20 °C, 25 °C, and 30 °C). The experiment was repeated 3 times. Root images were captured at the time of and every two days after transferring germinated seeds to the growth pouches. The x-intercept method was used to determine TbRE. There was a relatively large range in TbRE among the ten soybean cultivars ranging from 8.1 °C to 13.2 °C and were not related to the cultivar’s maturity grouping. Cultivars with lower TbRE are expected to be able to explore and occupy greater soil volume under cooler conditions. These observed result warrants further investigation in the field.