Identification and Evaluation of Endophytic Bacteria On Melon Sphaerotheca Fuliginea

Powdery mildew is a serious air-borne fungi disease in melon (Cucumis melo L.) throughout major cultivation area of the world. This disease is epidemic in greenhouse and open-field as well as often causes serious economic loss. In present, powdery mildew is one of the most serious disease on melon production in China. The aim of this research is to evaluate the possibility of exploiting endophytic bacteria in the biological control of melon powdery mildew (Sphaerotheca fuligine). 31 strains of endophytic bacteria were isolated from the host (MR-1) with high resistance to powdery mildew in the experiment. Among them, one strain named Mg15 demonstrated better efficacy to control melon powdery mildew in the seedlings biocontrol and leaf disc experiments, which was identified as Bacillus subtilis according to morphological, physiological and biochemical characteristics and 16S rDNA sequence. The control efficacy of strain Mg15 was 70.68% in the seedlings. Besides, only 9.29% of the spore germinated from the leaf disc experiment after 12 hours while 60% of the production of conidia decreased compared with the control after14 days, the hyphae shrank and even deformed after the application of Mg15 fermentation broth observed by scanning electron microscopy. Additionally, the application of Mg15 undiluted fermentation broth had the highest control efficacy on powdery mildew with 80.66% melon seedlings uninfected in a greenhouse experiment. These results indicated that this strain of endophytic bacteria could be a promising agent for the biocontrol of melon powdery mildew in greenhouse.
 Key words: Melon; Powdery mildew; Antagonistic endophytic bacteria; Biological control