Screening And Control Effect Of Antagonists And Antibiotics On Grapevine Downy Mildew

Grape Downy Mildew causes great damages of grape production and restrains the health development of grape industry severely. Presently, chemical control is still the main measure to control the grape downy mildew. Agrochemical were applied with overdoses in growing season, causing a series of problems including pathogens’resistance to agrochemicals, environmental pollution and poisonous residue in fruits. Therefore, it is of great importance to study the biological control of grape downy mildew. This paper aims to focus on the screening of antagonists and antibiotics, which will provide theoretical and technical basis for the biological control. The sporangia of Plasmopara viticola, an obligatory parasite, can not be obtained easily. To ensure the smooth selection of antagonistic bacteria and antibiotics, experiment were performed to study the favorable condition for the forming and germination of the sporangia of P. viticola. The results are as follow:1 The grape leaves inoculated with the sporangia of P. viticola were put at different illumination, humidity and nutrition conditions, to observe the morbidity. It is found that under the condition of 20℃, darkness,100% humidity and 2% lactose, a lot of the sporangia of P.viticola could easily formed.Solidify the sporangium by Water Agar Method to study the condition for the the sporangia of P. viticola to germinate. The results demonstrated that the favorite conditions for germination of the sporangia of P. viticola was 4℃ for 0.5 h, and cultivated in 15℃ with 2% lactose, the germination rate is the highest, which is 85.3%.2 In the experiment in vitro, the morbidity rate of the sporangia of P. viticola mixed with Streptomyces rimosus,6Y1, CN300 is 15%,10.83%,0%, respectively, with a significant difference from the contrast. The Fermentation method was used to study the control effect of different component of CN300、6Y1. The results showed that the mycelium of 6Y1 has an obvious control effect, and the effect was more prominent as the density increases. Through morphological identification and 18SrDNA ITS sequence analysis,6Y1 was identified as Alternaria brassicae. In order to obtain more mycelium of 6Y1, using the experiment of single factor and L9 (33) orthogonal test, the influence of medium, rotation speed, inoculum, and liquid volume on the yield of 6Y1 hyphae were studied. Under the optimized condition when the rotation speed is set at 200 r/min with inoculation amount at 2, and volume at 175 mL, the production is the highest, which is 0.907g/100mL.3 After treatment of the grape leaves with different antibiotics, the sporangia suspension were inoculated to measure the control effect of different antibiotics on grape downy mildew. It is found that the preventive effect of 300 times of Wuyiencin,200 times of kasugamycin, and 1000 times of polyoxin are 81.67%,55% and 66.67%, respectively. Jinggangmycin had no obvious effect. Spraying the 4 kinds of antibiotics on the diseased grape leaves, and after 3 days, we found that kasugamycin agent has an obvious treatment effect on grape downy mildew. The kasugamycin with penetrating agent has synergistic effect on grape downy mildew in indoor and field experiment.