Screening Of Biocontrol Bacteria And Fungicides To Phytophthora Melonis

Cucumber phytophthora blight caused by Phytophthora melonis is one of the main diseases of cucumber, which becomes increasingly serious in its planting area. According to statistics, it once occurred in large areas of Qinghai, Hainan, Jiangsu, etc., causing degradation in both cucumber yield reduction and taste, as well as farmer’s enthusiasm. Up’ till today, the major prevention and control method is chemical pesticides, but long-term usage can increase the drug resistance of pathogenic bacteria, the control effect becomes worse and worse. For better prevention and treatment of Cucumber phytophthora blight,55 bacteria strains isolated from soil samples from Beijing, Jilin and Hunan province. Bacterio static test screening by using tablet confrontation and fermented liquid of cucumber sojae with antagonistic activity of bacteria. Results show that 3 strains in 55 strains of bacteria have inhibition to the fungus cucumber, with bacteriostasis reach more than 5mm and 3 strains, X4 strains has most obvious antagonism, inhibition rate reaches 72.5% by 5 times dilution fermented liquid. According to morphology, the cultivation of X4 strain properties, physiological and biochemical characteristics, and 16s rDNA sequence analysis, it is preliminarily idented as f Paenibacillus polymyxa.In addition, this paper chooses 9 kinds of common fungicides on the market for indoor medicament screening. The resμLt shows that most common fungicides on market have good virulence on Phytophthora melonis. such as Pyraclostrobin metiram, the EC50 is under 10 μg/ml,as 5.4143 μg/ml. The EC50 of Osthole, Oxadixyl and Cornyn (chlorothalonil) are respectively 10.4641 μg/m、11.6654 μg/ml and 17.3221 μg/ml. There was certain degree of synergism after Pyraclostrobin metiram mixed Osthole with different ratio and the most obvious synergism with EC50 5.8178 mg/L when the ratio of Pyraclostrobin metiram mixed Osthole was 1:2.