Abstract

This study sought to develop a biological control agent against plant diseases of various crops and vegetables using Streptomyces sp. A1022. We found that the culture broth had an inhibitory effect against several fungal pathogens, including Colletotrichum gloeosporioides, Phytophthora capsici, Pyricularia grisea, and Cercospora canescens. The antifungal activity of the culture broth was stable (> 93%) across a broad range of temperatures (25-90 ^oC) and pH (pH 2-9), suggesting that the solid concentrate (SC) of strain A1022 might be effective against a broad range of fungal pathogens. We examined the inhibitory efficacy of this strain against anthracnose by Colletotrichum gloeosporioides in infections of pepper and cherry tomato. We found the degree of anthracnose injury to pepper to be in the following order: untreated control?eugenol (sopra extract) > tebuconazol (a chemical fungicide) > azoxystrobin (a chemical fungicide)?strain A1022 SC. Strain A1022 SC also had an inhibitory effect against anthracnose on cherry tomato. In a field test, azoxystrobin (10,000 ppm active ingredient; 1,000-fold dilution) and strain A1022 SC (2×10⁴ colony forming unit mL^-1; 500-fold dilution) had inhibitory effects of 68.0 and 61.6% against pepper anthracnose, respectively. Our results suggest that strain A1022 SC can be an alternative to chemical fungicides, at least for pepper and cherry tomato anthracnose infections caused by C. gloeosporioides.

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