Biological control of potato late blight with a combination of Streptomyces strains and biochar

Potato late blight (PLB) caused by Phytophthora infestans is the most damaging disease in potatoes. In this study, Streptomyces and biochar (a new eco-material with the potential to improve soil and plant health) were used for the biological control of PLB. In vitro experiments showed that the six Streptomyces strains can significantly inhibit the growth of P. infestans and sporangia germination. In vivo tests showed that the six Streptomyces strains significantly inhibited the infection of P. infestans on potato tubers. After combined with biochar, the inhibition rate of Streptomyces strains against P. infestans was increased by 1.9 % to 46.1 %. In two years of field trials, the combination of six Streptomyces strains and biochar decreased the disease index by 10 % to 26 %, exhibiting better disease control than the use of either agent alone. In addition, a single application of biochar did not significantly decrease the incidence of the disease but enriched the rhizosphere in the beneficial bacterium Rhizobium. Our results highlight the potential for biological control of PLB with a combination of Streptomyces strains and biochar.