Preliminary studies on the cold tolerance of soybean seedlings

Emergence experiments were conducted on 32 soybean (Glycine max (L.) Merrill) cultivars at a 2.5-cm depth in Guelph loam soil at 10, 20 and 30 C. Differences in emergence were found among cultivars at 10 C but not at 20 and 30 C. Results of the emergence experiment at 10 C permitted classification of cultivars into cold tolerant, intermediate and intolerant groupings. There was no close relationship between maturity group and degree of cold tolerance. Differences in speed of germination were found among cultivars at 10 C. A correlation coefficient (r = +0.616) between germination and emergence indicates that germination at 10 C would be effective in the selection of cold tolerant types. Growth analysis studies on seedlings up to the unifoliolate leaf stage showed that cold tolerant cultivars had a higher fresh weight at a specific age at 10 C. This was attributed to the faster emergence of the cold tolerant cultivars.