The Screening And Preliminary Study Of Biocontrol Agents Against Phytophthora Blight Of Pepper

1.Screening, identification and characteristics research of Biocontrol agentWe got 871 bacteria isolated from 116 plant and soil samples which were collected in Xinxiang, Pingdingshan, Xuchang etc. within Henan Province. After preliminary screening experiment of restrain Phytophthora capsici, including inhibit the growth of fungal mycelium, zoosporangia formation, releasing zoospores and spores germination, we got 4 effective BCAs, then we chose G28-6 as our final BCA after rhizosphere colonization test and pot culture test. Through the morphological, physiological and biochemical characteristics and 16S rDNA sequence analysis , the biocontrol agent G28-6 was identified as Pseudomonas aurantiaca. G28-6 can inhibit a variety of plant pathogens, such as Rhizoctonia, Fusarium, Colletotrichum, Pythium and so on; In the pot and plot experiment, the biocontrol agent G28-6 showed high colonization density in rhizospere of pepper. With the Double Layer Filter and the sandy soil detecting, the colonization density of root in pepper was 6.37×10⁵ cfu/cm and 6.83×10⁵ cfu/g. In plot experiment, the colonization density of root in pepper was 2.20×10⁵ cfu/g after 4 weeks, and it remained 104 cfu/g after 16 weeks。2.Applying technology research of P. aurantiaca G28-6This study reseach the applied concention, application method and using period of P. aurantiaca G28-6 to explore the application of technology. It was significantly different to the control efficiency and the colonization density in different concentrations of P. aurantiaca G28-6. In pot and plot experiment, the control efficiency of 10⁹cfu/ml of G28-6 was reached 85.3% and 79.4%, meanwhile, in plot experment, the colonization density of 10⁹ cfu/ml of G28-6 was higher than other concentrations on early transplanting period of pepper. Dipping roots with P. aurantiaca G28-6 on the transplanting period of pepper, the control efficiency was the best, and the colonization density was significantly higher than other treatments.3. The optimized cultivating conditions of P. aurantiaca G28-6Through orthogonal test, We found the best fermentation medium of P. aurantiaca G28-6 was Glycerol 1.0%, K₂HPO₄ 0.7%, KH₂PO₄ 0.2%, (NH₄)₂SO₄ 0.1%, MgSO₄·7H₂O 0.01%; the optimum cultivation time was 20h; the optimum temperature was 28℃; the optimum speed was 140rpm, the optimum medium volume was 50%, the optimum medium initial pH was 7.5.