Antagonisms of two biocontrol Streptomyces strains against tobacco pathogens

Streptomyces, abundant in soil, are a group of filamentous bacteria producing a variety of beneficial secondary metabolites, gifting them the potential to be developed as bio-pesticides and biofertilizers. S. exfoliatus FT05W and S. cyaneus ZEA17I are two biocontrol strains able to reduce the damages of Sclerotinia sclerotiorum on lettuce. In Guizhou province, second largest producer of tobacco in China, tobacco production is highly threatened by several phytopathogens. In this study, we investigated the in vitro antagonisms of S. exfoliatus FT05W and S. cyaneus ZEA17I against three main pathogens on tobacco in Guizhou province, China. S. exfoliatus FT05W and S. cyaneus ZEA17I respectively showed 68.82% and 76.18% antagonism against Phytophthora parasitica var.nicotianae, the causal agent of tobacco black shank disease. For Alternaria alterana, the causal agent of tobacco brown spot disease, S. cyaneus ZEA17I showed 35.5% antagonism, whereas, S. exfoliatus FT05W did not show any antagonism. Moreover, both two Streptomyces strains could not inhibit the growth of Ralstonia solanacearum, the causal agent of bacterial wilt of tobacco. Our resultsindicatedthegreatlypromisingpotentialofapplyingS.exfoliatusFT05WandS.cyaneusZEA17Ifortobaccoblackshankdisease management, but future evidence about their antagonisms in vivo is needed.