| Take-all of wheat is a serious fungal disease caused by Gaeumannomyces graminis(Sacc.)Arx&Oliver var.tritici Walker.It is a typical soil-born root disease and have been reported in many wheat-growing areas of China.In Huang-huai winter wheat rigion,take-all disease is serious and greatly affected the yield and quality of wheat.The antagonistic bacteria from plant rhizophere have the potential to control the plant soil-born disease.In this study,we isolated 1051 bacteria strains from shangqiu city and zhumadian of Henan province in order to obtain biocontrol bacteria against Gaeumannomyces graminis var.tritici.Using plate confrontation method,we screened 88 strains antagonistic bacteria.We ultimately obtained 9 strains of bacteria that have stable antagonistic effect for the follow-up research.On the basis of molecular analysis of 16S rDNA and gyrB genetic sequences and physiological and biochemical tests,P155,P154,P16 and P147 were identified as Pseudomonas fluorescens;P97 and P188 were Pseudomonas putida;LY3 was Lysobacter enzymogenes;B20 was Burkholderia cepacia;S38 was Stenotrophomonas rhizophila.PCR test results showed that only P147 and B20 contain pyrrolnitrin synthesis gene.And P147 also contains phenazine synthesis gene.All 9 strains produced protease,but none of them produced cellulose.Except B20,LY35 S38 and P147,the other strains produced siderophore.Apart from P97 and P188,the other 7 strains produced lipopeptides.The disease control and plant-growth promotion investigation in greenhouse indicated that the relative control efficacy of all strains was over 50%.Among them,strains P154 and P155 had the highest effect to disease and their control efficacy was 67.11%and 63.82%respectively.The control efficacy was similar to that of fungcide difenoconazole treatment(the average control effect was 61.11%).The growth-promoting effect of P188 and B20 was the highest.These two strains increased wheat shoot length by 12.55%and 12.79%,and increased wheat fresh weight by 37.04%and 28.89%and increased theat dry weight by 75.01%and 56.25%respectively.Although P154,P147 and P155 increased the shoot length of wheat,they showed some inhibitory effect to the root.The growth-promoting mechanism of these strains was explored.The result indicated that all 9 strains secreted IAA,but the capabilities were different.Among them,the secreted IAA of P147 and P155 was more than that of other strains.It reached 378?g/mL and 327?g/mL respectively.The secreted IAA of strain S3 8 was the least,it was only 35?g/mL.The colonizations of three bacteria P155,P147 and S38 in wheat rhizosphere were studied.The results show that colonizations of 3 strains in sterile soil were better than that in natural soil.The colonization was increased when the soil was inoculated with Gaeumannomyces graminis var.tritici.In comparison,the colonization of strain S38 in soil was the best among 3 strains and strain P147 was better than strain P155. |
PDF Full Text Request