Genetic adaptation for vernalization requirement in Nepalese wheat and barley

A large number of accessions of covered and naked barley from eastern Nepal were grown without vernalization, and it was found that naked barley accessions were predominantly spring varieties while covered barley accessions were predominantly winter varieties. Seven accessions were subjected to a range of vernalization periods. Four naked varieties were spring varieties, although one showed some response to vernalization, but the three covered barleys were winter varieties. Although the majority of naked barleys are spring forms, they are winter sown at high altitudes and this does not conform to the distribution of naked barley described by Takahashi (1955). Wheat accessions which came from villages situated at high altitudes tended to have higher vernalization requirements than those which came from lower altitudes. This was taken to indicate local adaptation and a low movement of seeds (gene-flow) between villages. The relationship between vernalization requirement and altitude was not found in barley. Marked but contrasting regional patterns for vernalization requirement occurred in the wheat and covered barley. It was concluded that gene-flow was greater within regions than between them. This regional isolation together with environmental heterogeneity are major diversity promoting mechanisms.