Genotypic variation in cold tolerance of 18 Ethiopian rice cultivars in relation to their reproductive morphology.

• We evaluated cold tolerance for inducing male sterility of 18 Ethiopian rice cultivars. • Spikelet fertility under cold stress ranged from 0 % to 90 % at phenotyping facilities. • This variation was explained by anther length and pollen number per anther. • Anther length and pollen number without cold stress can be used for prescreening. Male sterility induced by low temperatures during reproductive development is the major constraint on rice production in Ethiopia, which generally lies at high elevations. Because of a lack of phenotyping facilities, limited information is available on the cold tolerance of Ethiopian germplasm. We evaluated the genotypic variation in cold tolerance of 18 Ethiopian rice cultivars in two phenotyping facilities and characterized their cold tolerance in relation to their reproductive morphology in a 2-year trial in Japan. Genotypic variation in spikelet fertility was high after exposure to cold during reproductive development at both facilities, with fertility ranging from 0% to 90 %. 'Andassa' and 'Tana' had the highest fertility and 'Fogera 2' and 'Getachew' had the lowest. The two cold-tolerant germplasms had tolerance similar to that of the Japanese 'Hitomebore' (strong), whereas the susceptible germplasms had tolerance similar to that of the Japanese 'Sasanishiki' (weak). The variation in spikelet fertility was explained by both anther length and number of fertile pollen grains per anther under cold stress, and by anther length under unstressed control conditions in both years of the study; longer anther length and higher fertile pollen number leads to stronger cold tolerance. Our results suggest that anther length under unstressed conditions offers a pre-screening criterion for cold tolerance without requiring phenotyping facilities for screening. [ABSTRACT FROM AUTHOR]