| In this paper, the pathogenicity, biovar, extracellular enzyme of six strains and the seedling and adult resistance identification of five tomato cultivars to bacterial wilt were studied. Meantime, the physiological and biochemical changes were studied after inoculation with Ralstonia solanacearum in order to clarify the physiological and biochemical resistance mechanism of tomato to bacterial wilt. The results were as following:The results indicated, the six tested strains all had pathogenicity and the pathogenicity order from strong to weak was HF,HX,YS,FY,HN2,HN1.The FY strain couldn't utilize eulcital and belonged to a subtype of biovar Ⅲ —Ⅲ–1,while others strains belonged to biovar Ⅲ. The results of extracellular enzyme activities indicated, the extracellular enzyme(PG and EG) activities increased accompanied with the prolongation of cultivation time gradually, and the enzyme activities reached the max in 7～9 days after cultivation. The relativity between the max of PG activity and pathogenicity was not too large(r=0.6371),while the relativity between the max of EG activity and pathogenicity was very large (r=0.9526).Tomato cultivars were inoculated with R.solanacearum with the pouring method of the seedling's hurt root and the diseased plant rate was investigated at the first, second, third week respectively after inoculation. Three times investigation results were coincident. Five tomato cultivars were all susceptible in seedling, but there were significant difference on the diseased plant rate among cultivars. Qiangfeng was the highest and Xinxing was the lowest, while others cultivars were between Qiangfeng and Xinxing.Tomato cultivars were inoculated with R.solanacearum with the pouring method of the adult's hurt root. The result showed: Xinxing, Xiazuanshi, Huangshanyihao were resistant cultivars and the resistance indexes were 12.9,12.3,10.9 respectively. Huangshanerhao was middle–resistant cultivar and the resistance index was 8.9.While Qiangfeng was susceptible cultivar and the resistance index was only 2.5.Five defensive enzymes' activities in leaves of tomato were under homeostasis without inoculation in seedling. The enzyme activities of POD,PPO and PAL in leaves of all cultivars ascended after inoculation. The enzyme activities of POD,PPO and PAL of Xinxing, Xiazuanshi, Huangshanyihao, Huangshanerhao were always higher than those of CK after inoculation, and the ascending speed ,the largest increasing rate, the peak values of the four cultivars were higher than those of Qiangfeng. The enzyme activities of POD,PPO and PAL of Qiangfeng in early days was higher than those of CK after inoculation, while was lower than those of CK in late days after inoculation. The changes of enzyme activities of SOD and CAT in leaves of all cultivars were turbulent and were absence of orderliness after inoculation. So, the three enzymes (POD, PPO, PAL) of leaves of tomato could be used as assistant guidelines of filtrating the resistance cultivars in early phase after inoculation with R.solanacearum, while SOD and CAT needed more studies.Five defensive enzymes activities in leaves and roots of tomato were under homeostasis without inoculation in adult. They fluctuated in a certain scope , but the extent was small. The enzyme activities of POD and PAL in leaves and roots of resistant cultivars and middle–resistant cultivar were higher than those of the susceptible cultivar without inoculation. The enzyme activities of POD, PPO, PAL, SOD in leaves and roots of all cultivars ascended after inoculation. The PAL and SOD were more susceptive than others and their activities peaks appeared earlier than others'. The enzyme activity of PAL appeared two peaks, while others appeared only one peak. The peak values and the largest increasing rates of enzyme activities of POD,PPO,PAL in roots of all cultivars were higher than those of leaves, while SOD was reverse to others. As a whole, the activities of four enzymes in leaves and roots of resistant cultivars and middle–resistant cultivar were h... |
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