Study On Screening Of Salt-Tolerant Cultivars And Physiological And Biochemical Characteristics In Chinese Cabbage

Soil salinization severely deteriorates the growth, yield and quality of Chinese cabbage [Brassica campestris ssp. pekinensis (L.) Olsson]. Therefore, how to improve the salt tolerance of Chinese cabbage becomes a hot topic in the research fields of cultivation and breeding. In this paper, three method including germination testing, germfree culture and Hoagland solution culture under NaCl stress were applied to study the salt-tolerant of Chinese cabbage at the germination stage and seedling stage. These results will offer useful information for Chinese cabbage breeding and production in salinity area.1. Sixteen Chinese cabbage varieties were treated with different concentrations of NaCl (0, 0.5%, 1.0%, 1.5% and 2.0%) and the salt tolerance were studied at germination stage. The results showed that the seed germination of some varieties was promoted under low concentration of NaCl (0.5%). But under high salinity, seeds germination of all varieties was repressed. Under salt stress, the germination rate, germination potential and germination index were all restrained in different degree. Based on germination salinity index, it showed that 01-3, 05-9, 03-8, 04-8 and Jingcui60 were much more tolerant than others. Jingqiu81, Beijingxinyihao and Jingxia4hao were much more sensitive, and the other varieties were medium.2. Sixteen Chinese cabbage varieties were cultured in germfree MS medium with different concentrations of NaCl (0, 0.5%, 1.0%, 1.5% and 2.0%), and their salt tolerance were compared. The results showed that the germination of Chinese cabbage was not affected by 0～1.0% NaCl. With the increase of NaCl concentration, the germination rate of different varieties declined obviously, and the salt injury indexes increased differently among varieties. According to salt injury index, it showed that 01-3, 03-8, Jingcui60 and 05-7 were more tolerant to salt stress, Jingqiu81, Beijingxinyihao, Beijingxinsihao and 04-8 were salt-sensitive, 05-9 and 03-9 and others were medium.3. According to results above, Six Chinese cabbage varieties with different salt-tolerance, including salt-tolerant varieties 01-3 and 03-8, salt-sensitive varieties Beijingxinsihao and Jingqiu81, and the medium varieties 05-9 and 03-9, were selected and planted in 1/4 Hoagland solution treating with NaCl (0, 0.5%, 1.0%, 1.5% and 2.0%). The results showed that the growth of seedlings was restrained. The dry weight, fresh weight and relative water content of over ground part declined; The value of dry/fresh weight and the salt injury indexes increased; The relative content of dry substance and the salt injury indexes were distinguishable in various varieties and could be used to select salt tolerant germplasm in Chinese cabbage at seeding stage.4. To study the dynamic of the contents of MDA, proline, free amino acid and soluble sugars under salt stress, six Chinese cabbage varieties with different salt-tolerance were planted in 1/4 Hoagland solution and treated with different concentrations of NaCl. The results showed that, with the increase of NaCl concentration and the prolonging time of NaCl stress, the contents of MDA, free proline, soluble sugars and free amino acid increased gradually. MDA content in leaves were distinguishable in various varieties and could be used to select salt tolerant germplasm in Chinese cabbage at seeding stage.In conclusion, three methods were applied to evaluate salt-tolerance at germinating stage and seedling stage in Chinese cabbages. It was cleared that there was obvious difference among varieties in salt tolerance. In addition, the characteristic of salt-tolerance was discussed, and the method for salt-tolerance evaluation was preliminarily set up. These are fundamental for salt-tolerance improvement in Chinese cabbage breeding.