Identification and biocontrol effect of antagonistic Streptomyces against postharvest Penicillium fruit rot of Phyllanthus emblica L.

Abstract:

[Background] Fruit rot caused by Penicillium choerospondiatis is the main postharvest disease of Phyllanthus emblica L., and frequently causes serious fruit decay and large economic loss. [Objective] To obtain and evaluate the control effects of actinomycetes strains with strong antagonistic effect on P. emblica rot fungi. [Methods] Agar disk method and growth rate method were used to screen antagonistic strains against P. choerospondiatis DQ23, and the morphological, physiological and biochemical characteristics combined with 16S rRNA gene sequence were used for classification and identification. The biocontrol effect of the cell-free fermentation broth on fruit rot and quality of P. emblica was evaluated. [Results] Strain SC-15 had a strong antagonistic effect on P. choerospondiatis DQ23 mycelial growth with inhibition zone diameter of 18.70 mm. The inhibition rate of cell-free fermentation broth on mycelial growth of P. choerospondiatis DQ23 reached 87.8%. Based on the morphological and physiological characteristics and 16S rRNA gene sequence analysis, strain SC-15 was identified as Streptomyces virginae. The disease percentage and disease severity index of P. emblica fruit decreased significantly after the treatment via soaking in cell-free fermentation broth of strain SC-15 before storage. The decrease rate of soluble solids and titratable acids in the treated fruits was also slowed down. The results showed that 75% of cell-free fermentation broth had the best protection against P. emblica fruit rot. On the 8th day of storage, the fruit disease percentage was 53.3%, the fruit disease severity index was 35.2%, the content of soluble solids and titratable acid were 4.8% and 6.25 mg/g, respectively. [Conclusion] Streptomyces virginae SC-15 can effectively prevent postharvest fruit rot of Phyllanthus emblica caused by P. choerospondiatis.