Isolation And Identification Of Biocontrol Bacteria T201 Against Phytophthora Sojae And Reseach Of Its Biocontrol Effect

In this study, ten biocontrol bacteria against Phytophthora sojae were isolated from soybean rhizosphere soil from soybean fields in Jiangsu, Anhui and Henan Province. The strain, named as T201, showed the best ability of inhibiting the growth of Phytophthora sojae. The strain T201 had broad width of clean zone in the culture medium after 14 days. Therefore, strain T201 was selected as the research material in this study.Based on the results of the morphological characteristics, physiological and biochemical identification and phylogenetic analysis of 16S rDNA sequences, the strain T201 was identified as Bacillus sp..The influences of temperature, pH, rotational speed and medium components on the growth of strain T201 were studied. The results of experiments showed that the optimal temperature was 30℃, the optimal pH was 7.0 and the optimal rotational speed was 180rpm. Sucrose was the best carbon source and yeast extract was best nitrogen source of strain T201. The strain had higher growth rate when the proportion of carbon-nitrogen was 10/1 in the medium.Determination of inhibition effect of the strain T201 against Phytophthora sojae was carried out. The result showed that the inhibition rate of strain T201 against Phytophthora sojae reached 67.89% on the seventh day. The inhibiton activities of different-time zymotic fluid of strain T201 against Phytophthora sojae were different, and the inhibition rate at 72h was the highest for mycelia growth, with the inhibition rate of 49.13% on the sixth day. Likewise,72h zymotic fluid of strain T201 could significantly inhibit zoospores of Phytophthora sojae from geminating and its inhibition rate was up to 47.96% at 8h after treating with 72h metabolic liquid. In vitro experiment, soybean leaves and soybean sprouts soaked in the bacterium solution of T201 could resist the invasion of Phytophthora sojae effectively. On the contrary, soybean leaves and soybean sprouts, which were not soaked in the bacterium solution of T201, could not resist the invasion of Phytophthora sojae, and the injected parts all turned black and got diseases. The potted experiment in the greenhouse was also performed to examine the in-vivo control effectiveness of the strain T20. The results showed that souybean seedings, whose roots were soaked in the bacterium solution of T201 three days prior, had significant resistance to Phytophthora sojae with the inhibition rate of 54.59%on the tenth day. Finally, the bacterium solution of T201 could also promote the soybean growth. The roots length and the stems length of the soybeans in the experimental group increased 26.65% and 11.31%, and the fresh and dry weight increased 37.06% and 23.53% compared with the control group.