Biological control of Botrytis cinerea on tomato plants using Streptomyces ahygroscopicus strain CK‐15

We developed a real‐time PCR assay to specifically detect and quantify the efficacy of a biological fungicide from Streptomyces ahygroscopicus var. wuyiensis on tomato leaves. This fungicide, the natural secondary metabolite wuyiencin, is an antifungal agent against Botrytis cinerea. Specific primers were designed based on the β‐actin gene sequences, which were used to detect a 303 bp fragment from B. cinerea isolates. Our assay is highly sensitive and can be used to reliably detect and quantify as little as 1·75 pg of B. cinerea DNA. We used this detection method to monitor the progression of B. cinerea infection in inoculated plant material under preventive (wuyiencin) and nonpreventive treatment. After 5 days, plants under preventive treatment exhibited a sharp decrease in fungal biomass and no symptoms, whereas plants under nonpreventive treatment displayed severe disease symptoms. The results demonstrate that wuyiencin has significant effects on B. cinerea in tomato plants and that real‐time PCR is a reliable method for evaluating the effects of Streptomyces wuyiensis CK‐15 on B. cinerea. SIGNIFICANCE AND IMPACT OF THE STUDY: Botrytis cinerea commonly produces latent or nonsymptomatic infection on and within plant tissues, which can develop into symptomatic infection when triggered by changes in environmental conditions or host plant physiology. In this study, we develop a specific, sensitive real‐time PCR assay for detecting and quantifying B. cinerea on tomato leaves to determine the control efficacy of Streptomyces ahygroscopicus var. wuyiensis as a biological fungicide. Our findings demonstrate that wuyiencin has significant effects on B. cinerea in tomato plants and that real‐time PCR is a reliable method for evaluating the effects of biological fungicides on plant pathogens.