Frost Tolerance in Soybeans1

Abstract

Additional frost tolerance in soybeans (Glycine max (L.) Merr.] would be a useful trait. Our research was conducted to test the effects of prefrost temperatures, stages of plant development, and genotype on frost tolerance in soybeans. In one experiment, 30 genotypes were tested for frost tolerance. Plants were grown in controlled environments at prefrost day/night temperatures of 15/9, 20/14, and 25/19 C, then subjected to advective white frosts of − 2, − 2.5, and − 3 C. at the cotyledon, unifoliolate, or first trifoliolate leaf stage in a factorial design, for a total of 27 treatments. Lower frost temperatures caused a greater percentage of the tissue to be damaged and a greater percentage of plant kill. Plants grown at 25/19 C before frost exhibited more damage than plants grown at lower temperatures. Frosts at the cotyledon stage killed fewer plants (P<0.1) than at the unifoliolate leaf stage, with plants at the first trifoliolate leaf stage intermediate in susceptibility to frost. Most plants grown to the cotyledon stage at 15/9 C could survive frosts of − 3 C. Significant (P<0.05) differences were measured in frost tolerance among genotypes, but the temperatures tolerated varied only about 0.2 C.In a second experiment, 40 genotypes collected in the People's Republic of China were grown at 25/19 C and subjected to − 2.5 and − 3 C at the first trifoliolate leaf stage. No differences in frost tolerance were detected among genotypes. The results suggest that little variability exists among genotypes of G. max for frost tolerance.