Antagonic Effect Of Pseudomonas Chlororaphis XF10 On Phytophthora Parasitica Var. Nicotianae

The tobacco black shank caused by Phytophthora parasitica var.nicotianae is one of the most serious root diseases in tobacco production.In order to quickly and effectively screen out antifungal strains that have obvious antagonism against tobacco black shank,300 soil samples were collected from the healthy plants rhizosphere in serious tobacco black shank incidence areas.A strain,XF10,which has obvious antagonistic effect was screened.The strain was identified and its antagonistic effect on pathogen was studied.The main research is as follows:1.Three strains,CY106,XF10,CY110,were obtained by plate dilution method,rapid initial screening of pathogenic bacteria and confrontation culture.The inhibition rate of XF was the highest,which was 83%.The results of pot experiment showed that XF10 strain of tobacco black shank relative control effect is the best.The best preservation method of XF10 strain was preserved at-80℃.2.XF10 was identified as Pseudomonas chlororaphis.by morphological characteristics,biological phenoltype identification,BIOLOG automatic microbiological identification system and 16 S rDNA gene sequence analysis.3.By studying the effects of incubation time,temperature and pH on XF10 strain,it was determined that the best culture time of XF10 strain was 72 h,the optimum growth temperature was 31℃ and the optimal pH was 7.5.4.Both bacterial fluid and fermentation supernatant extract of XF10 possessed more than 80% inhibitory rate on.This strain can inhibit the normal growth of Phytophthora parasitica var.nicotianae.Further analysis showed that the strain could produce cellulase and protease.5.The bacterial fluid and extracellular metabolite crude extract of XF10 can inhibit the growth of pathogenic hyphae,the production of sporangium,the release of sporangium,and the germination of zoospores.The best treatment was to add 5 mL bacterial strains,which has obvious effect on the growth of mycelium,the inhibition rate of 95.6% to sporangium production,the relative inhibition rate of 86.7%to sporangium release,the inhibition rate of 58.2% to zoospores germination in 24 h.6.The volatile metabolites of XF10 could inhibit the growth of pathogenic hyphae with an inhibition rate of 86% by two plant buckle method.The volatile matter of XF10 strain was analyzed by SPME-GCMS method,the results showed that a total of 15 volatile products with high degree of match(≥80%)were detected.Including olefins,ketones,alcohols,and alkanes.By studying the relationship between different culture time and volatile product content of strain XF10,we found that the content of volatile products was the highest when cultured for 6 days.