Isolation, identification, and antimicrobial activity of culturable Actinomycetes from banana plantation soil

Abstract:

[Background] Panama disease of banana, an intractable disease in banana, restricts the development of banana industry. Therefore, it is of great significance to screen out strains with inhibitory activity against Fusarium oxysporum f. sp. cubense tropical race 4 (Foc4). [Objective] To isolate Actinomycetes from samples of banana plantation soil and preliminarily identify species, and subsequently determine the antagonistic activities of the isolated Actinomycetes against seven pathogens including Foc4, so as to acquire strains with high activity and biological control strategies to solve Panama disease of banana. [Methods] Soil samples of banana plantation soil in Guangxi were collected and pretreated by ultrasonic wave and other means. Actinomycetes were separated using a variety of specific media and identified based on their 16S rRNA gene sequences. Seven pathogenic bacteria were used as targets to screen out the bacteriostatic strains by the plate confrontation method, and the bacteriostatic rate against Foc4 was determined by the mycelial growth rate method. [Results] A total of 138 strains of Actinomycetes were isolated from the samples of banana plantation soil, all of which were Streptomyces. Among them, five strains numbered X1085, X1052, X2052, X3059, and X4046 were potential new species. Seventy-seven strains with antimicrobial activities were screened out, with the positive rate of 55.8%. Twenty strains exhibited inhibitory activity against Foc4, among which four strains manifested obvious antagonistic effects, and their inhibitory rates were greater than 80%. The inhibitory rate of the strain X4050 was 93.76%. [Conclusion] The species information of culturable Actinomycetes in banana plantation soil was preliminarily clarified, and some of them were unknown species. Results of activity analysis showed that more than half of Actinomycetes had antimicrobial activity, and some of them exhibited good antagonistic activity against Foc4. These results provide a theoretical basis for the research on the isolation, identification, and biological activity of culturable Actinomycetes in the banana plantation soil, and provide a new idea for biological control of Panama disease of banana.