Effects of temperature and moisture stress on the germination of diverse common bean genotypes
Seed germination of diverse common bean (Phaseolus vulgaris L.) genotypes was evaluated under controlled suboptimal conditions. Initially, 16 genotypes were tested at 12 and 16 °C. A subset of genotypes was subsequently germinated in distilled water or in polyethylene glycol solutions with water potentials (WP) of either −0.4 or −0.8 MPa at temperatures of 22, 26 or 34 °C. Genotypes did not respond consistently to low temperature stress, as indicated by significant (P < 0.05) crossovers in genotype ranking for percent germination from one temperature (12 °C) to the next (16 °C). Genotypes differed in median germination time (GT50) and estimated maximum germination rate. Genotypes with thinner seeds germinated better than wide-seeded genotypes under low-temperature conditions. Seed germination was reduced by 10 percentage units at a WP of −0.4 MPa and was virtually nil at a WP of −0.8 MPa. GT50 was reduced by 30% at 26 versus 22 °C but delayed by 80% when the WP was lowered from 0 to −0.4 MPa. Similarly, maximum germination rate increased with temperature but decreased with WP. Based on the germplasm evaluated in this study, common bean genotypes differ in seed germination response to temperature and moisture stress. Key words: Common bean, Phaseolus vulgaris L., germination, temperature, water potential