The Geographic Origin of Frost Tolerance in Syrian Pasture Legumes

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Abstract
Two experiments were conducted at Tel Hadya, near Aleppo, Syria to study the frost tolerance of a total of seventy-nine indigenous and introduced species of Mediterranean annual legumes. One of the main objective was to locate the geographic origin of frost tolerance amongst indigenous legume populations in western Syria. Ecotypic differentiation in frost tolerance was found in most of the seventy-nine species studied. In general, accessions collected from cold areas were tolerant of frost, while accessions from mild environments were susceptible. It was possible, however, to find tolerant accessions in mild environments, and, occasionally, susceptible accessions in cold environments. A few species, including Medicago rigidula, was tolerant irrespective of origin. Commercially-available pasture legumes, whose origin was Australia, were very susceptible to frost, between 80 and 95% of plants being killed. Native legumes, especially Medicago rigidula and M. rotata, showed high tolerance to frost and can be reviewed as alternatives to imported species for pasture development in west Asia.