Screening And Identification Of Antagonistic Bacteria Against Fusarium Head Blight

Fusarium head blight(FHB)is a worldwide fungal disease.It not only causes loss of crop yield,but also produces mycotoxins that seriously endanger human and animal health.At present,the combination of disease resistance breeding and chemical control strategies is mainly used for disease prevention and control,but the development of wheat varieties resistant to scab is difficult.Chemical control can bring problems of drug resistance and pesticide residues,and biological control is a potential alternative to control FHB.In order to screen out the bacteria with biocontrol effect in Fusarium head blight,stalks of rice straw containing pathogens were taken from the field of Jiangsu Academy of Agricultural Sciences,and 550 bacteria were isolated by dilution separation.Three strains of biocontrol bacteria capable of inhibiting growth of pathogenic fungi Fusarium graminearum strains F0609,PH-1 and Fusarium pseudograminearum CF14047 were screened.The 16s rDNA and gyrB sequences of 3 strains were similar to those of Pseudomonas azotoformans F77.P.azotoformans is present in water and soil and is reported to induce disease resistance in cucumber.In order to understand the antagonistic mechanisms of three bacteria strains,the metabolites were analysed with HPLC.A suspected peak of pyoluteorin was detected.The whole genome of P263 strain was sequenced,and the genes of secondary metabolites in the genome were analysed.The results showed that the antagonistic bacteria P263 does not contain 2,4-diacetyl phloroglucinol(2,4-DAPG)and pyoluteorin biosynthetic genes,but it contains some non-ribosomal polypeptide synthetase(NRPS)gene clusters and bacteriocin biosynthetic genes.Related products need further exploration.The study also found that all strains can produce diffferent amounts of siderophore and protease.In the application of biocontrol bacteria,the biocontrol bacteria were inoculated on the isolated corn whiskers,and some biocontrol effect against Fusarium graminearum was observed.The effect of three strains of bacteria at seedling stage was determined by means of antagonistic bacterial seed dressing.The results showed that 3 strains of biocontrol bacteria,especially strain P263,can control wheat crown rot caused by Fusarium pseudograminearum,and the relative control efficacy was 50.35%.In addition,the emergence rates of wheat after the bacteria seed treatment were similar to those of control.In order to clarify the application range of these antagonistic bacteria in the control of wheat diseases,the antagonistic spectrum of 3 bacteria strains was tested.The results showed that 3 strains could inhibit the growth of F.pseudograminearum,Gaeumannomyces graminis and Rhizoctonia cerealis.The field experiment results showed that the strain P295 had the best control effect to Fusarium head blight and its control efficacy reached 30.2%,which was higher than that of P263,P305 and carbendazim treatment.In addition,the effect of 3 actinomycetes strains to Fusarium griminearum was also explored.The results verified that the tested actinomycetes strains had a good antagonistic effect on Fusarium griminearum and the strain JK1 has the highest activity.The antagonistic mechanisms and application protencial of these atrains need further study.