Disease control efficacy of 32,33-didehydroroflamycoin produced by Streptomyces rectiviolaceus strain DY46 against gray mold of tomato fruit

Abstract

Despite the efficacy of synthetic fungicides in controlling postharvest diseases, public concerns regarding chemical residues in food and an increase in drug-resistant strains of pathogens have led to a need for new agents to control postharvest diseases. The current study was performed to find control agents of microbial origin that are effective on gray mold of tomato fruits. We recently isolated Streptomyces rectiviolaceus DY46, which has antagonistic activity against various plant pathogenic fungi. The incidence of gray mold of tomato fruits was markedly reduced by 80.0% in tomatoes treated with the cell extract of Streptomyces rectiviolaceus DY46 compared with the control tomatoes. The active ingredient was purified from the cell extract of DY46 and identified to be 32,33-didehydroroflamycoin (DDHR). DDHR displayed MICs (minimal inhibitory concentrations) against the mycelial growth of various plant pathogenic fungi at concentrations of 8–64 mg L−1. The incidence of gray mold in tomato fruits inoculated with conidial suspension (104 conidia mL−1) of Botrytis cinerea was markedly reduced by 88.9% in tomatoes treated with DDHR (100 mg L−1) compared with the control. The DDHR residue in tomato fruit was significantly diminished 2 d after treatment. These results show that DDHR would be relatively safe for use as a postharvest fungicide.

Isolation and identification of endophytic actinobacteria from Citrullus colocynthis (L.) Schrad and their antibacterial properties

“…Some species of Streptomyces rectiviolaceus , closely related to KUMS-C3, was reported to have inhibitory activity against various plant pathogenic fungi [ 90 ]. It was documented that S. rectiviolaceus DY46 produces 32,33-didehydroroflamycoin having antifungal activity.…”

Biocontrol potential of Streptomyces sp. CACIS-1.5CA against phytopathogenic fungi causing postharvest fruit diseases

“…Cell-free culture filtrates from Streptomyces katrae strain NB 20 showed significant inhibitory effects on mycelial growth and conidial germination of C. musae; for conidial germination, the inhibitory effects were 97.7 ± 0.9% and 95.0 ± 0.6% (Shu et al 2017). Recently, a secondary metabolite purified from Streptomyces rectiviolaceus DY46 reduced the incidence of gray mold of tomato fruits by 80% in tomatoes treated with the cell extract compared with the control tomatoes (Kim et al 2019).…”

“…There were commercial products comprised of Streptomyces species, such as Actinovate® (Natural Industries, Inc.) and Mycostop ® (Verdara Oy), both used for the control of foliar and root diseases of various crops (Yuan and Crawford 1995). On the other hand, secondary metabolites produced by Streptomyces have been evaluated to control gray mold (B. cinerea) in tomato fruits, in particular a polyene macrolide was able to reduce the incidence of the disease (Kim et al 2019).…”

Synergistic Interactions of Schizostatin Identified from Schizophyllum commune with Demethylation Inhibitor Fungicides

“…Conidial suspension of B. cinerea B05.10 and PDB (BD Biosciences) was used for screening synergistic microbial extracts in combination with tebuconazole. The minimum inhibitory concentration (MIC) of tebuconazole for B. cinerea was previously determined using the two-fold broth microdilution method in three replicates (Kim et al, 2019). For screening of synergistic microbial extracts, 25 μl of conidial suspension (4 × 10 5 conidia/ml), 25 μl of quadruple-strength PDB, 48 μl of sterile water, 1 μl of microbial extract, and 1 μl of tebuconazole solution (20 μg/ml in DMSO) were added to each well of a 96-well plate (No.…”