| In vitro salt tolerance at seedling stage of 15 representative tomato common cultivars(Lycopersicon esculentum Mill.) were evaluated under a series of Ca(NO3)2 concentrations,and the analysis of salt tolerance of 7 tomato rootstock selfed lines: TR-1, TR-2, TR-3,TR-4, TR-5, TR-7, TR-8 was studied at a high Ca(NO3)2 concentration(75 mmol·L-1).Seedling growth and salinity injury of different cultivars were examined after 10 days oftreatment. Results showed that significant differences in salt tolerance were observedamong 15 different cultivars. Cultivars of Shanghai 903, Suhong 2003, Sunshine 906, DayuZhongshu No. 4, Sanxing L402, Tomato Dahong, Zhongshu No. 4, Baoda 903, Xiafen,Maofen 802 were Ca(NO3)2 sensitive; Zaofeng Tomato, Jiangshu No. 14, Baofen, Sanxing906 were medium Ca(NO3)2 tolerant; Japanese Dafen Queen was Ca(NO3)2 tolerant. Underthe same treatment, the average numbers of lateral roots of rootstock selfed lines weresignificantly higher than those of tomato common cultivars, while the salt stress indexes ofrootstock selfed lines were significantly lower than those of common cultivars. The salttolerance of rootstock selfed lines was higher than that of tomato common cultivars, andsalt tolerance of TR-8 was highest among the experimented tomato materials.In order to achieve a further understanding of the Ca(NO3)2 tolerance of the rootstock,differences in growth, chlorophyll contents, contents of osmotic adjustment substances,activities of antioxidant enzymes and superoxide radical (O2·-) producing rate in leaveswere compared under hydroponic culture between tomato rootstock cultivar 'Kagemusya'and common cultivar 'Baoda 903' exposed to 70 mmol·L-1 Ca(NO3)2 stress for 15 days.The results showed that under Ca(NO3)2 stress plant growth, chlorophyll contents, contentsof free proline and soluble proteins, activities of antioxidant enzymes in leaves of tomato rootstock seedlings were significantly higher than those of common cultivar seedlings,while O2·-producing rate and content of malondiadehyde (MDA) in leaves of rootstockseedlings were significantly lower than those of common cultivar seedlings. Ca(NO3)2stress reduced chlorophyll contents while increased O2·- producing rate and content ofMDA significantly in both of the two kinds of tomato seedlings. The growth of rootstockseedlings was less retarded by Ca(NO3)2 stress than that of common cultivar seedlings. Itwas concluded that higher activities of antioxidant enzymes and less oxidative damagemight be involved in a stronger salt tolerance of rootstock seedlings.The aim of this study is to screen out the tomato cultivar and rootstock with Ca(NO3)2tolerance, prove up the internal reason of Ca(NO3)2 tolerance of the tomato rootstock, andfinally provid theoretical basis for screening and using of germplasm resources of tomatoestolerant to Ca(NO3)2 stress.
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