Abstract
By using the breeding materials of the Assam hybrid with or without wind quard, cold resistance in winter was investigated.
Cold resistance, annual correlation coefficient of cold resistance and correlation between cold resistance and cold hardiness were vary with the method of cultivation management. Comparing cold resistance of the hybrids in the same combination, the hybrids without wind quard were suffered from more severe cold damage. It would be said that cold damage was promoted by exposure to wind. In the case of cultivation without wind quard, it was not easy to get the hybrids suffered lightly even though the various varieties were crossed with the Assam varieties.
Heritability value of cold resistance was fairly high. Cold resistance of the Assam varieties was very weak, so it was necessary to combine with the cold resistant varieties in order to get the resistant hybrid, but it was very difficult to breed the bearable hybrid for low temperature in 1967, and almost hybrids were needed protection against cold.
It would rather breed the hybrids introduced good quality of the Assam variety than breed the cold resistant hybrids in utilizing the Assam variety for crossing.
