| The root rot of C.pilosula is one of the most serious diseases caused by Fusarium oxysporum,with the incidence rate was up to 20%,which seriously affects the quality and yield of C.pilosula and causes great economic losses.Early studies showed that Paenibacillus polymyxa YF,Bacillus amyloliquefaciens HT and Bacillus velezensis BQ all had good inhibitory effects on Fusarium oxysporum.In this study,the potential biological control ability of Paenibacillus polymyxa YF,Bacillus amyliquefaciens HT,and Bacillus velezensis BQ to the root rot of C.pilosula were evaluated.The experimental results are as follows:1.The results of the dual confrontation between three antagonistic bacteria and Fusarium oxysporum showed that the mycelium inhibition rate of Paenibacillus polymyxa YF was the strongest,which was 65.17%,and that of strains HT and BQ was 48.89%and 50.55%,respectively.The morphology of hyphae in the confrontation area has undergone great deformation,with hyphae expanding and shortening,internodes shrinking and even hyphae breaking.In addition,the sterile filtrates of three antagonistic bacteria can effectively increase the permeability of cell membrane,leading to serious expansion and wrinkling of hyphae,and then collapse and rupture,and can obviously inhibit the spores germination of Fusarium oxysporum.2.All three antagonistic bacteria could colonize on the roots of C.pilosula,and strain BQ has the strongest colonization ability of which colonization amount was finally stable at5.2×10~3CFU/g.All three antagonistic bacteria can use tryptophan to produce IAA and promote the growth of C.pilosula.The control effect of greenhouse conditions and ex vivo on the root rot of C.pilosula showed that all three antagonistic bacteria could effectively reduce the severity of root rot of C.pilosula,and there were significant differences among the three antagonistic bacteria.Among them,strain YF has the best therapeutic effect,with the inhibition rate of 58.21%in greenhouse and 59.24%in ex vivo.Strain BQ has the strongest preventive effect,with the inhibition rate of 49.25%in greenhouse experiment and 63.62%in ex vivo experiment.The determination of resistance enzyme activity showed that strain BQ had the strongest ability to induce resistance enzyme activity of C.pilosula.In addition,all three strains of antagonistic bacteria contain synthetic genes of lipopeptide Iturin,Fengycin and Surfactin,and their crude protein extracts and product extracts can effectively inhibit the growth of F.oxysporum.The crude protein extracts contain protein bands which are consistent with the expected sizes of antimicrobial lipopeptides Iturin,Fengycin and Surfactin,and their antibacterial activities against F.oxysporum were 54.29%,62.13%and 52.09%respectively.The antibacterial activities of the crude extracts were 33.85%,51.77%and40.58%,respectively.3.Pretreatment with Fusarium acid can accelerate the infection of F.oxysporum on C.pilosula,and the disease index of C.pilosula increased with the increase of FSA concentration,with significant statistical difference.The fermentation broth or sterile filtrate of three antagonistic bacteria can significantly reduce the FSA content in the fermentation products of F.oxysporum.Among them,the fermentation broth or sterile filtrate of strain YF has the best inhibitory effect,which was 78.90%and 77.90%respectively,and there were significant differences among three antagonistic bacteria.The three antagonistic strains have the ability to degrade FSA,and the statistical difference was significant.Among them,strain YF has the strongest degradation ability,which was 24.86%.Strain YF because of its antagonistic effect against F.oxysporum and its therapeutic effect on the root rot of C.pilosula to be used as a potential biological control strain.However,strain BQ has strong colonization and ability to prevent the root rot of C.pilosula to be used as a potential strain to prevent root rot of C.pilosula. |
PDF Full Text Request