Studies On Resistance Mechanism Of Cabbage Seedling To Myzus Persicae (Sulzer)

Myzus persicae (Sulzer) (Homoptera: Aphididae) is one of the important pests which endanger vegetables. This thesis studied the antibiosis and changes of chemical substance and isozymes of different cabbage varieties endangered by M. persicae. The resistance mechanism of cabbage seedling to M. persicae was discussed by relative analysis and nonlinear regression analysis. The main results were as follows: 1. Six cabbage cultivars including Zhonggan11, Jingfeng1, Zaohongziganlan, Ganqiu, Wanfeng, Xiaguang, were investigated for their relative antibiosis to M. persicae in lab. The results showed that Zaohongziganlan is comparatively high resistance to M. persicae and rm is lowest, Wanfeng is comparatively low resistance to M. persicae and rm is highest. 2. The content of soluble sugar of different cabbage varieties in seedling period had a positive correlation with rm of M. persicae (F=14.93,P=0.0181). The regression equation was: rm=0.1652+0.0877x (R2=0.7887). This suggested that the higher the content of soluble sugar was, the bigger rm of M. persicae. The variety was found to be more susceptible cultivar. 3. The soluble protein content of different cabbage varieties in seedling period had a negative correlation with rm of M. persicae (F=25.41,P=0.0073). The regression equation was: rm=0.4126-0.0179x (R2=0.8640). The result showed that the higher the soluble protein content was, the smaller rm of M. persicae. The variety showed comparatively high resistance to M. persicae. 4. The VC content of different cabbage varieties in seedling period had a negative correlation with rm of M. persicae(F=34.69,P=0.0042). The regression equation was : rm =0.4123-0.0485x (R2=0.8966).The result showed that the higher the VC content was, the higher resistance to M. persicae. 5. Activity of PPO, PAL, POD were some important factors influencing cabbage resistance to M. persicae. In early stage after M. persicae endanger cabbage, activity of PPO, PAL, POD was positive relative with density of M. persicae. The higher these enzymes activity was, the better the expression the cabbage resistance to M. persicae. Moreover, to the cabbage seedling which had the different resistance level to M. persicae, the amount of increase in these enzymes activity had positive relative with cabbage resistance to M. persicae. 6. POD isoenzyme of Cabbage are analyzed by using PAGE. The results showed that the number of bands of POD isoenzyme did not change after cabbage was endangered by M. persicae, but the activities of some POD isoenzymes were enhanced. Furthermore, the activity of POD was obviously higher in Zaohongziganlan than that of in Wanfeng. This showed that the higher POD isoenzyme activity is useful to expression of cabbage resistance to M. persicae in early stage that M. persicae endanger cabbage. 7. There is not obvious interrelation of cabbage resistance to M. persicae with EST isoenzyme. EST isoenzyme was not suitable to be used as a physio-biochemical criterion for identifying cabbage resistance to M. persicae.