Biological control of powdery mildew in Korean melons through a treatment with a culture of Bacillus species

Efficient management systems of facilities make it possible to manage environmental conditions properly, such as the temperature, humidity and light source required for the best growth of the crops, as well as for the mass production of fruit and vegetables with high quality every year through an advanced and protected cultivation system. Powdery mildew is a type of chronic disease that is difficult to control during the production of Korean melons under a protected cultivation system, the use of which is increasing in production areas in Korea. Two Bacillus strains isolated from soil samples showed antagonistic activities against several pathogens, specifically Botrytis cinerea, Colletotrichum gloeosporioides, and Fusarium oxysporum f.sp. melonis; they were identified as Bacillus velezensis M2 and B. amyloliquefaciens M3 in a molecular biological test of the nucleotide sequences of gyrase subunit A (gyrA). The treatment was given three times at intervals of five days with 400-fold diluted cultures of B. velezensis M2 and B. amyloliquefaciens M3. This led to the inhibition of the incidence of powdery mildew disease in Korean melon leaves, which resulted in effective control efficiency against the incidence of powdery mildew disease with control values of 87% and 65%, respectively. Cultures of antagonistic microbes tested in this study can be used to increase the efficiency as part of an environmentally friendly management scheme to prevent powdery mildew disease during the protected cultivation of crops, including Korean melons.