Watermelon Bacterial Fruit Blotch Of Research

It was first reported that watermelon bacterial fruit blotch disease occurrenced in Jilin Province. Two strains were isolated from different parts of the infected plants in different regions of Jilin province. According to their morphology, cultural characteristics, physiological and biochemical characteristics as well as symptomatology, and comparing with the concerned parts in <> 9th ed, the pathogens are identified as Acidovorax avenae subsp.citrulli Willems et al. 1992( Pseudoumonas pseudoalcaligenes subsp. citrulli Schaad et al. 1978). Besides watermelon, the bacteria can also infect other cucurbitaceous crop, tomato, eggplant and pepper by inoculating in greenhouse.Influence of different content of Nitrogen, Phosphate, Potassium fertilizer on resistance of watermelon to the disease were firstly tested by planting plants in nutrition solution, the results showed that nitrogen fertilizer can promote the development of the disease, potassium fertilizer can strengthen the resistance of plants to the bacteria, and phosphate fertilizer has no obvious influence on the resistance of plants.All the tested varieties were susceptible to the bacteria in different level, but the varieties with green skin appeared symptoms earlier and had much and larger spots than those of black skin and decorative pattern skin.ELISA were firstly used for detection of bacteria-seeds of watermelon nationwide and worldwide. The best suitable dilution ratio of sheep-anit-rabbit IgG linked horseradish peroxidase is 1:100, and the best suitable concentration of immunoglobulin IgG is 8ug/mL. The immunoglobulin IgG has a specific reaction with Acidovorax avenae, but no reaction with Clavibacter michiganense and Pseudomonas syrinae pv. (abaci, and all detection with ELISA was finished in 6 hours. The result of detection with ELISA corresponds to that of conventional detection by isolation and inoculation. So ELISA is a rapid and accurate method to detect bacteria-seeds of watermelon.9 chemicals are tested for comparing the inhibition effect to the bacteria indoor. The results showed that XingZhiMeiSu is better than any other chemical chosen for seed-treatment of watermelon. The watermelon seeds treated with XinZhiMeiSu of 200mg/L has a control effect of 43.2% higher than that treated with other chemicals. Why do the chemicals have not an ideal control effect used for seed-treatment but have a good inhibition-bacteria effect in culture dish? The questions need to be studied further.When 77% Koxide 50Qx, XiJunQing 200mg/L, LianMeiSu 300mg/L, XiZhiMeiSu 200mg/L were sprayed at early stage of the disease in greenhouse, the control effect can reach at 60.0%,71.4%,64.4% and 79.9% respectively. So XiJunQing 200mg/L and XiZhiMeiSu 200mg/L are better chemicals for controlling disease at watermelon seeding stage, but they are not effectively used for peel on the infected parts of Watermelon, so seed-treatment and spraying at seeding stage are the key mearures to control the disease.