SOURCES OF COLD TOLERANCE IN GRAIN SORGHUM

Abstract

The term "cold tolerance" refers to the ability of sorghum (Sorghum bicolor (L.) Moench) genotypes to germinate, grow and produce satisfactory grain yields under conditions of relatively cold (but above-freezing) air and soil temperatures. Sources of cold tolerance and their usefulness in grain sorghum were investigated. Of 380 excessively tall, photoperiod-sensitive, and late-maturing accessions obtained from China, Ethiopia, and Uganda, 39 were cold-tolerant, 157 partially tolerant, and the remainder were susceptible when rated at physiological maturity. Highest levels of cold tolerance were found among accessions from Ethiopia (e.g. Alemaya 70, Jejewegere 935, and Muyra) and Uganda (Mabere, Magune, and Nyundo). Cold tolerance appeared to be a dominant trait. However, in cold-susceptible × cold-tolerant crosses there was a wide range of variation among cold-tolerant genotypes, and the frequency of highly tolerant segregates was less than 10% in the F 2 , suggesting that several genes controlled the inheritance of the character and that their effects were largely cumulative. A relatively large number of dwarf, photoperiod-insensitive, early-maturing, and cold-tolerant experimental lines were developed. Some of these were very well adapted to the highlands of Honduras, Kenya, and Mexico. In general, they were poorly adapted to high-latitude sites in the northwestern USA, southern Canada and West Germany.Key words: Cold-tolerant sorghum, adaptation, international testing, Sorghum bicolor