Research On Identification And Control Of Cherry Crown Gall Pathogen In Baqiao District, Xi’an

Cherry crown gall disease can cause tumors in cherry tree roots and branches, resulting in great economic losses due to the yield reduction in cherry orchard every year. Baqiao district in Xi’an City is a large cherry product area of Shaanxi Province, where the cherry industry has become one of the emerging pillar industries. Cherry crown gall in this area has been spreading rapidly in recent years. With aims of offering better solutions to the serious problems, we investigated the occurrence of cherry crown gall disease in the field; determined the crown gall pathogens by isolation, physiological and biochemical identification, and molecular biological identification, and tested the inhibiting effect of different types of chemicals through the laboratory experiments. The chemicals with a certain inhibitive effect were selected for further test in the field. The results are as below:1. The cherry crown gall was found spread seriously in Baqiao district by investigating the occurrence of this disease in the field. The disease incidence in old plantations had higher rate than the new ones. 100% percent of old cherry trees were suffered by this disease. With the increase of tree-age, the incidence rate got higher, and the disease index went up as well. The serious diseased trees grew with full of tumors. The swelling of tumors damaged the phloem, and hindered the transport of nutrients and water, resulting in the weakness and gradual death of the tree body. Some cherry trees even were damaged by insects and flew gummosis.2. Totally 15 strains were isolated from the soil and tumors of the infected roots and branches, they were identified by molecular biological method. Three strains including DZ08, DZ10 and DZ11 were identified as Agrobacterium tumefacien. But only the strain DZ08 had pathogenicity. Through physiological and biochemical method analysis, it belonged to biological type I. It might be the main cause of crown gall in this area.3. The inhibiting effects of 17 kinds of chemicals was explored to the pathogen of crown gall by using the inhibition zone method in the laboratory. The results showed that six kinds of chemicals had inhibitory effects on crown gall pathogen. The 80% ethylicin showed the best inhibitory effect, the inhibitory zone of the 200 times diluents was 29.6mm. The other two effective chemicals were 0.3% tetramycin and 72% streptomycin. The EC50 of ethylicin, tetramycin and streptomycin were 538.27 mg/L, 3.03 mg/L, 1435.82 mg/L, respectively. The fermentation broth of biocontrol strain 153 had inhibitory effect on crown gall pathogen.4.The control effect of chemical to the cherry crown gall was tested in the field. Using the methods of scraping tumor and applying combination of the chemicals. Through observations and results analysis showed that 6 kinds of chemicals had different effects. Ethylicin, tetramycin showed the best effect. Thiram showed the worst effect, which still showed significant difference from the controls.