Screening And Identification Of Antagonistic Bacteria Against Gaeumannomyces Graminis Var. Tritici

The wheat take-all is a fungal disease caused by Gaeumannomyces graminis (Sacc.) Arx& Oliver var. tritici Walker. It is a typical wheat root disease and occurs in many wheat growing areas worldwide. The take-all of wheat was first discovered in Zhejiang province, and then the disease was discovered in other wheat growing regions in China. Currently, the occurrence of disease is becoming severer and.severer in Huanghui winter wheat growing areas.In order to obtain antagonistic bacteria against Gaeumannomyces graminis var. tritici, we isolated 648 strains of bacteria from the rhizosphere of wheat plants collected from Shangqiu City of Henan Province. We obtained 41 antagonistic bacterial strains against Gaeumannomyces graminis var. tritici through plate antagonistic determination experiment, and then we selected 20 strains of bacteria according to the antibacterial band width (not less than 0.3 cm or vigorous growth). They were identificated based on the sequences of 16S rDNA and rpoB gene, and the control effect of these strains was determined in greenhouse pots. We selected 9 representative bacterial strains for the further research and the nine antagonistic bacteria strains are GP4, GP9, GP16, GP46, GP51, GP52, GP54, GP56 and GP59 respectively.The molecular identification and physiological and biochemical test results showed that strain GP4, GP9, GP16, GP46, GP59 belong to Pseudomonas poae, and GP51 and GP52 were Pseudomonas chlororaphis, and GP54 and GP56 were Pseudomonas putida. The antifungal metabolites of 9 strains was analysed and the results indicated that all 9 strains produced proteinase, and GP51, GP52, GP54 and GP56 produced siderophore and lipopeptides, but they all can’t produce chitinase. The genes for antagonistic substances of the 9 strains were detected. None of them contained genes for 2,4-DAPG and Pyrrolnitrin production. GP51 and GP52 were only detected to contain genes forPhenazine-1-carboxylic acid, Pyoluteorin production. The disease control effect experiment in greenhouse showed that 9 strains can decrease disease index of wheat take-all, among which GP51 and GP52 were more effective, the relative control effect reached 30.5% and 33.3%.The antagonistic effect of 9 strains on other soil borne fungal pathogens was also tested. The results showed that all 9 bacteria strains had the high antagonistic effect on Bipolaris sorokinianum, and the inhibition zone were above 3.5 mm. Among 9 strains of bacteria, only GP51, GP52 strains had some antagonistic effect on Rhizoctonia cerealis, and strain GP9, GP16, GP46, GP51 and GP59 has weak antagonistic effect on Fusarium graminearum. These bacteria strains had different antagonistic effect on different chemical type pathogens of the wheat crown rot.In order to understand the colonization of these 9 bacteria strains in wheat rhizosphere, we developed rifampicin resistant strains. The colonization of the 6 bacteria strains including Pseudomonas poae (GP16 and GP59), Pseudomonas putida (GP54 and GP56) and Pseudomonas chlororaphis (GP51 and GP52) in wheat rhizosphere was determined, The results showed that the colonization of all 6 bacteria strains were better in the sterile soil than in the natural soil. The rhizosphere colonization of GP51 and GP52 were the best. It may explain the better biocontrol effect of GP51 and GP52 in a certain extent.The research provides strains for biological control of wheat take-all disease, and laid a foundation for selecting more effective bio-control strains and for control of wheat take-all in fields.