Changes of protective enzymes activities responding to Sclerotinia sclerotiorum inoculation in non-heading Chinese cabbages

Non-heading Chinese cabbage(Brassica campestris ssp.chinensis Makino) varieties,003-R-6,Y3-R-4,109-S-9 and 003-S-7,with different resistances to Sclerotinia sclerotiorum were selected as materials to study the activity changes of superoxide dismutase(SOD),catalase(CAT),phenylalanine ammonia-lyase(PAL),and polyphenol oxidase(PPO) after inoculation at seedling stage,and a simple linear regression analysis was made associated with the disease index.The resistant varieties showed higher CAT,PAL and PPO activities and lower SOD activity than the susceptible varieties in uninfected plants.Compared with the control,the protective enzymes activities increased significantly after inoculation with Sclerotinia sclerotiorum,and the resistant varieties were more sensitive than the susceptible varieties.Correlation analysis revealed that the variation ranges of SOD,CAT,PAL and PPO activities were positively correlated with the resistances to Sclerotinia sclerotiorum of non-heading Chinese cabbage,and the correlation coefficients were 0.814 3*,0.964 1*,0.999 4* * and 0.999 0* *,respectively.