Isolation,identification,and bioactivity evaluation of an actinomycetes strain RX2-2 against star anise anthracnose

Abstract:

[Background] Star anise anthracnose is a fungal disease caused by Colletotrichum horii,which has caused serious economic losses to star anise industry in China. [Objective]To isolate and screen out the actinomycetes strains with inhibitory effect on C. horii from the rhizosphere soil of star anise trees.[Methods]Actinomycetes strains were isolated by dilution-plating method,and a plate confrontation experiment was conducted to screen out the strains with antagonistic effects on C. horii.The antagonistic strain was identified based on morphological,physiological,and biochemical characteristics combined with 16S rRNA gene sequence analysis.The antagonistic activity was evaluated based on the mycelial growth rate.The biocontrol effect of the cell-free fermentation broth was tested with detached star anise leaves.[Results]An actinomycetes strain RX2-2 was isolated from the rhizosphere soil of star anise trees,which had a strong antagonistic effect against C. horii, with the inhibition rate of 95.48%.RX2-2 had a broad antimicrobial spectrum,with strong inhibitory effects on other seven plant pathogenic fungal species and five common bacterial species.The antibacterial substances in the fermentation broth of RX2-2 have good thermal stability.The cell-free fermentation broth showed the biocontrol effect up to 47.62% on detached star anise leaves infected with C. horii.RX2-2 was identified as Streptomyces lunalinharesii based on the morphological,physiological,and biochemical characteristics in combination with 16S rRNA gene sequence.[Conclusion]RX2-2 has a promising prospect in the biological control of star anise anthracnose and other plant diseases.