OUTCROSSING RATES IN BARLEY POPULATIONS IN THE CANADIAN PRAIRIES

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Abstract
Using three morphological markers, the magnitude of natural cross-fertilization in three successive generations, F3, F4and F5of four single crosses of barley (Hordeum vulgare L.) was estimated under dryland conditions of the Canadian Prairies. The average frequency of outcrossing was very low (0.35%). Somewhat higher rates of outcrossing were observed in a highly variable composite cross population of barley (CC XXI). CC XXI showed an overall outcrossing rate of 0.80%, when propagated under irrigated conditions, but only 0.47% under rainfed conditions. Outcrossing was significantly influenced by three components of the environment: temperature, precipitation and relative humidity during the flowering period. Temperature was most important when moisture was not limiting, whereas precipitation was the most important factor under field level drought. The overall frequency of outcrossing in CC XXI was not only considerably lower in the Prairies than in California or Scotland, but decreased progressively with advancing generations, in contrast to results in California.