| At present, because of the rapidly increasing of the area that watermelon re-planted, the disease increasingly seriously and the effect of chemical prevention was puny, developing the watermelon breeding of anthracnose resistance have become one of the most important assignments that production and research of watermelon. Investigate the identification of resistance to anthracnose of watermelon is the basal work of resistance disease breeding. Make an exact, easy, applied and scientific method for identify watermelon anthracnose in seeding stage can make it easy for developing the work of watermelon resistance disease breeding.This examination has studied the Colletotrichum orbiculare on it's separation, cultivation and the different culture medium for producing spore. Six varieties which were"Xinongbahao","M08"that highly resistant,"Zhongshiyoudan"and"Shannongjiuhao"that resistant,"Hongxiaoyu"and"Linglongwang"that susceptible were chose in the research. The method of resistance identification to watermelon anthracnose at seedling stage were studied systematically from the inoculation concentration, inoculation time, best time to investigate the state of disease. The biochemical and physiological changes of watermelon leaves after inoculation Colletotrichum orbiculare were also be studied.The results were as follows:1. The mycelium of Colletotrichum orbiculare growed more quickly on carrot culture medium and watermelon juice culture medium than on the others. The spore produced more quickly on the watermelon hull culture medium than the others.2. The best inoculation concentration of watermelon anthracnose in seeding stage was 1×10~6 pfu/mL, the best seedling stage was 2 true leaves stage, the best to investigate the state of disease was the 7th day after inoculation.3. POD and PPO activity and chlorophyll content were possibly correlated with disease resistance of the tested watermelon cultivars. Negative relationship was possibly in existence between the content of soluble protein and the disease resistance of the tested watermelon cultivars.POD and PPO activity and the resistance of the tested watermelon cultivars didn't have evident relativity. After inoculation, their POD activity all rised greatly, but different varieties had different speed. The speed of the variety that highly resistant were faster than the variety that susceptible. The 6th day after inoculation, POD activities in the leaves of the variety that highly resistant reached peak value, and they declined in the later days. POD activity didn't have obviously difference between the inoculated and the CK of the variety that susceptible in the prime 4 days. After the 4th day, the activity became higher than CK, but obviously lower than the variety that highly resistant.PPO activities of the varieties that highly resistant and susceptible were both being rising in the first 6 days after inoculation, and reached peak value in the 6th day. After that, they all declined in different degree. But the varieties that highly resistant were higher than the varieties that susceptible all along.Chlorophyll content of all the watermelon varieties reduced after inoculation and the reduced extent of the varieties that highly resistant was obviously lower than the varieties that susceptible. The content of the varieties that highly resistant was being uptrend. There were a little changes of the chlorophyll content of the varieties that susceptible, and it was being downtrend after the 4th day.The contents of soluble protein of all the watermelon varieties were all higher than the CK after inoculation. The peak value of the varieties that highly resistant appeared earlier than that of the varieties that susceptible. It showed that the varieties that susceptible were more sensitive of the pathogen invasion. |
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