In Vitro Resistance Identification Of Cabbage Black Rot And The Related Physiological And Biochemical Indexes Analysis

Cabbage black rot is a increasingly serious disease in the production of cabbage in china.Therefore, in order to improve the cabbage varieties resistance to black rot, it is very important to identify the resistance of germplasm resources to black rot by a convenient, rapid and reliable method. In this research, the methods of in vitro resistance identification of black rot was studied at the seedling stage of cabbage, and the resistance to black rot of different cabbage varieties was identified based on the method Meantime, the related physiological and biochemical indexs were analyzed after inoculation with Xanthommonas Campestris pv. Campestris in cabbge. The results were as follows:1. Using living spray method as a control, the dropping inoculation method in vitro was studied. Cabbage leaf disc of diameter 1.5 cm in 4-6 leaves stage was layed on wet paper, with a drop of Xanthommonas Campestris pv. Campestris of 1.0×108 cfu/mL concentration on the surface of the leaf disc in Petri plates, the inoculated leaf discs were incubated at 28℃for five days. The obtained resistance identification results by the dropping inoculation method were basically consistent with the living spray method. The result indicated the dropping inoculation method in vitro is viable, and may be used in identification of resistant varieties, screening of resistant germplasm sources and resistant mutants.2. The resistance of 44 cabbage varieties from Institute of Cruciferous Vegetables to Black rot was identified by the dropping inoculation method in vitro. The results showed that 16 varieties were resistant to black rot,18 varieties were tolerant to black rot, and 10 varieties were susceptible to Black rot.3. In the whose resistance were different. The enzyme activities of the 5 defense enzymes including SOD. POD. CAT. PPO and PAL in the leaves of cabbage varieties with different resistance to Black rot before inoculation were fluctuating in a limited scope, but the extent was small. The enzyme activities of SOD, POD, PPO and PAL in leaves of 6 varieties increased after inoculation, and the enzyme activity changes were great difference in all varieties. The enzyme activities of PPO in the leaves of CHANGBA, DONGFANGQIUFENG, DAPINGTOU, HEIYEXIAOPINGTOU reached a peak on the third day after inoculation. The enzyme activities of SOD, POD, PAL in the leaves of CHANGBA, DONGFANGQIUFENG, DAPINGTOU, HEIYEXIAOPINGTOU reached a peak on the fifth day after inoculation.Then the enzyme activities of SOD, POD, PPO, PAL in the leaves of 4 varieties began to decrease, but always maintained in a high level. The enzyme activities of PAL in the leaves of JIGUANSHILIANBAI, BEIHEIDAPINGTOU reached a peak on the third day after inoculation. The enzyme activities of SOD, POD. PPO in the leaves of JIGUANSHILIANBAI, BEIHEIDAPINGTOU reached a peak in the fifth day after inoculation.Totally, The enzyme activities of SOD, POD. PPO, PAL in the leaves of CHANGBA. DONGFANGQIUFENG, DAPINGTOU, HEIYEXIAOPINGTOU after inoculation were always higher than those of control, and the peak and the increasing rate of the four varieties were higher than those of JIGUANSHILIANBAI and BEIHEIDAPINGTOU. The change of enzyme activity of CAT in the leaves of all varieties was unordered after inoculation.A new band appeared on the isozymes maps of SOD and POD in leaves of resistant, tolerant and susceptible varieties after inoculation. There was always a additional band appeared on the isozymes map of SOD and POD in the leaves of resistant varieties relatived to those tolerant varieties after inoculaton, and an additional band appeared on the isozyme maps of SOD and POD in the leaves of tolerant varieties relatived to those susceptible varieties after inoculation. A new band would be observed on the isozyme maps of PPO in the leaves of all varieties after inoculation and the remaining bands would be more dense at the same time.The PPO isozyme bands were best dense in the leaves of resistant varieties after inoculation. The isozyme bands of CAT in the leaves of CHANGA, DONGFANGQIUFENG, DAPINGTOU, HEIYEXIAOPINGTOU, JIGUANSHILIAN BAI had no change after inoculation.but the denseness became lighter. The denseness of isozyme bands of CAT in the leaves of resistant varieties was lighter than that of tolerant varieties. The isozyme band B of CAT in the leaves of BEIHEIDAPINGTOU disappeared, and the denseness of other isozymes bands of CAT became lighter.In conclusion, the four enzymes (SOD,POD,PPO and PAL) may be used as physiological and biochemical reference indexes for the resistance identification to black rot after inoculation with Xanthommonas Campestris pv. Campestris. while CAT needs further studies.