Study On Identification And Antifungal Products Of A Biocontrol Actinomycete Strain Gz-8 Against Colletotrichum Gloeosporioides

Colletotrichum gloeosporioides,one of the most important pathogens in tropical and subtropical economic crops,it has a wide host range and large intraspecific variation.Many kinds of crops can be infected with anthrax.An actinomycete strain gz-8 was isolated from Linyi,Shandong Province,which had a strong antagonistic effect against Colletotrichum gloeosporioides with the inhibition rate of 72.5%.Strain gz-8 was identified as Streptomyces badius based on physiological and biochemical characteristics,combined with 16S rDNA sequence analysis.The fermentation broth supernatant and mycelium were respectively collected by Liquid shake flask fermentation to obtain the crude extract of fermented broth and mycelium.Strain gz-8 has a broad-spectrum antifungal activity,with strong inhibitory effects on six plant pathogenic fungi.The inhibitory activity of the crude extract from strain gz-8 was evaluated.The fermentation broth extract exhibits obvious inhibitory effects on the mycelial growth(EC₅₀=3.18μg/mL)and coni dial germination(IC₅₀=1.92μg/mL)of C.gloeosporioides,which had higher activity than the mycelium extract of strain gz-8.The fermentation broth extract had good thermostability and pH stability.The rubber leaves soaked in the gz-8 fermentation broth could effectively resist the infection of C.gloeosporioides.The control effect of 1000 mg/L fermentation broth extract to mango fruits infected with C.gloeosporioides was 35.94%,which had no significant difference with that of chlorothalonil at the same concentration.The gz-8 crude extracts were separated by active tracing method,and five compounds were obtained.The structure of the separated compounds were identified by spectral data.ZK1 is Feigrisolide B as the same as ZK2;ZK3 is Feigrisolide C and ZK5 is Dinactin.The antagonistic activity of ZK5 to 10 of plant pathogens were tested by the mycelium growth rate method.The inhibitory activity of ZK5（30μg/mL）on most of pathogens were exceeded 50%.The EC₅₀ and MIC of ZK5 to C.gloeosporioides were 2.55μg/mL and 44μg/mL,respectively,it was found that compound ZK5 could both inhibite conidium production and germination.In vivo test,it showed that the compound ZK5（1mg/mL）had a certain control effect to rubber leaves anthracnose.We also found C.gloeosporioides,treated with 10mg/mL ompound ZK5 almost lost the ability to infect rubber leaves.