Abstract: The rapeseed breeding for tolerance to drought is one of the most important ways to reduce yield loss from drought stress in autumn. Therefore, an experiment was conducted to estimate combining ability and heritability of drought tolerance during seed germination using complete diallel crossing design of seven cultivars. The germinating seeds of parents and F1 were treated with simulated drought stress in 10% PEG and grew for 7 d, then relative length of stem, relative fresh weight per plant, relative survival percentage, relative germination rate, relative germination energy, and relative vigor index were measured, general combining ability and special combining ability of germination traits were analyzed by Griffing I. The results showed that general combining ability was significantly different in six drought traits. And meanwhile special combining ability in five traits was significantly different except relative vigor index. Among 42 combinations, Zhongshuang 9 had the highest general combining ability effect values of six traits above which were 0.0708, 0.0656, 0.1185, 0.1048, 0.1096, and 0.0861, respectively. Although the general combining ability of Zhongshuang 6 was not very high, but the special combining ability of its combinations Zhong-shuang 6 × Xinongchangjiao and Zhongshuang 6 × Zhongshuang 10 was higher. The combinations can be used in rapeseed breeding for drought tolerance.

Key words: Brassica napus L., Seed, Simulated drought stress, Drought tolerance, Combining ability, Diallel crossing, Germination