Abstract:

In order to obtain Streptomyces strains with antagonistic effect on Fusarium oxysporum causing pepper root rot and clarify their antagonistic effect and classification, F. oxysporum was used as the indicator strain to screen by plate confrontation method. The inhibition rate was determined by mycelial growth rate method. Phylogenetic analysis was conducted based on 16S rRNA gene sequence. In this study, eight antagonistic Streptomyces strains were obtained by primary screening. The results of confrontation culture showed that the inhibition rate against F. oxysporum was 45.18%-62.81%, and the inhibition rate against the other four root rot fungi was 28.51%-60.00%. Among them, the strain ZY12.53b showed the best antagonistic effect with more than 50% inhibition rate against five root rot fungi. The fermentation filtrates of strains MDI2.4 and ZY12.23a had the highest antagonistic effect on F. tricinctum, and the inhibition rates were both more than 60%. In the phylogenetic tree of 16S rRNA gene sequence, the eight antagonistic Streptomyces strains clustered into five different branches, and two of them were likely to be potential new species. In this study, eight antagonistic Streptomyces strains belonging to at least five species were obtained, among which three strains showed satisfied antagonistic effect with the value of potential exploration.

Key words: Streptomyces, Fusarium oxysporum, screening, phylogenetic analysis