The Study Of Biological Control Against Tomato Yellow Leaf Curl Virus

Tomato yellow leaf curl virus disease is a devastating disease caused by tomato yellow leaf curl virus (TYLCV), transmitted by Bemisiatabaci. The disease was first discovered in Israel in1964, and then quickly spread to the Middle East, the Mediterranean coast, Africa, Europe, and Australia and other regions. Especially since the1990s, as global warming and whitefly outbreak, the disease rapidly in the global spread of the disease in over40countries and regions, becoming one of the important diseases on tomato production. Currently, the disease prevention and control measures are mainly dependent on breeding for disease resistance and chemical control. But the results are not satisfactory, and pesticide residue problems have become increasingly prominent, it is proposed to adopt the strategy of biological control of tomato yellow leaf curl virus disease.115strains that our laboratory have screened and have antagonistic effect to multiple pathogens were selected against tomato yellow leaf curl virus disease. A total of14strains showed significant biocontrol efficiency against tomato yellow leaf curl virus disease in greenhouse. The control efficiency was more than50%. Field experiments in the second half of2011showed that, the control efficacy of these biological agents had better effect than the control, with rate ranged from28.50%to57.26%, of which6strains were over45%. Bacillus cereus3B Y4showed best control efficiency to tomato yellow leaf curl virus disease, with rate of57.26%. Though the control efficiency of Entervbacter asburiae BQ9was lower than3BY4, it showed more stable efficiency. When detected at50days after tomato yellow leaf curl virus disease accurd, the control effect was still more than40%. The root colonization and leaf colonization of6biological agents could still reach104CFU/g or more after treated30days. Among them,3BY4had the best colonization ability. The data showed that the plant height, stem diameter, dry weight and fresh weight were higher than control, with6.27-37.26%biomass increase, under greenhouse conditions after treated with Six antagonistic bacteria (5×10’CFU/mL)20days later.The effects of6biological agents on the yield and quality of tomato in fields were investigated in the first half of2012. The yields were increased by18.35%-31.70%.They can also improve the tomato quality by increasing the contents of Vitamin C, soluble sugar, soluble protein and decreasing the content of organic acid, improving the tomato flavor. Through determination the content of organic matter, available N, P and K between different treatments, we found that these biocontrol agents can improve these types of nutrients content in the rhizosphere soil, of which treatment of AR156,3BY4and BQ9enhanced the content of nutrients more significantly. The field test in Beijing suburban area resulted that the control efficacy after treatment with the agents to Oudun was over44%, but17%-30%to Zhongnong105and Moneymaker, showing species differences.In addition, the article also studied the mechanism in induce systemic resistance by PGPR BQ9against tomato yellow leaf curl virus disease. The root colonization of BQ9could still reach105CFU/g or more after treated30days, but the colonization of BQ9on leaf was not detected, showing biocontrol agent BQ9and pathogen was isolated in space, so we suggest that BQ9can induce systemic resistance against tomato yellow leaf curl virus disease. A further study found that, the defense-related genes PR1a and PR1b were concurrently expressed in the leaves of BQ9-treated plants. The above genes expression was faster and stronger in plants treated with BQ9and inoculated with TYLCV than that in plants only inoculated with TYLCV. Moreover, the cellular defense response H2O2burst was induced upon challenge inoculation in the leaves of tomato plants primed by BQ9. Further analysis on phenylalanine ammonialyase(PAL), peroxidase(POD), catalase(CAT) and superoxide dismutase(POD) in tomato plants showed that the amounts of defense enzymes significantly increased in BQ9-treated plants challenged with TYLCV when compared to control.