Biological Control And Its Mechanism Of Food-grade Bacillus Subtilis LJH25

Bacillus subtilis strain LJH25 was preserved in our laboratory. In vitro LJH25 was strong resistant to Pyricularia grisea, The fermentation of LJH25 is not stable to temperature, while the temperature exceeded 80℃, the antimicrobial activity falls down extremely; It's stable in neutral acid and alkaline situation while the antimicrobial activity falls down in extra acid and extra alkaline. The filtrated LJH25 was precipitated in grades with the ammonium sulfate to draw the antimicrobial proteins and crude proteins were obtained. One crude protein drawn with ammonium sulfate at 40% saturation showed strong antimicrobial activities to Pyricularia grisea. Average radius was accounted for 1.2 cm. It also showed a high antimicrobial activity against Rhizoctonia solani, Sclerotium spp., Pythium ultimum, Botrytis cinerea, Fusarinm solani, Fusanum oxysporum and Sclerotinia sclerotiorum, it had a broad-spectrum antimicrobial activity.The growth of rice was promoted by transfection of LJH25. Compared with the CK group, the root length, the number of lateral roots, seedling height and fresh weight of the seedlings of of rice seeds were higher, demonstrated a significant growth advantage. The indicators of height, fresh weight, dry weight, root length, root fresh weight and root dry weight were higher when treated by liquid spraying, broth soaking and dipping. At the same time, the chlorophyll content, root activity, SOD, POD and CAT activities were all improved.LJH25 resulted in longer colonization of rice. One day after inoculation, there is no LJH25 isolated from root, stem and leaf, then, the number of LJH25 inside the root, stem and leaf showed a growth trend:the number of LJH25 in root maintained relatively stable at the higher level on the second day; the number of LJH25 in stem reached its highest level on the fifth day, and then followed by a slow decline in addition to the higher level; and then gradually decreased to a stable level; the number of LJH25 in leaf reached its highest level on the third day, then decreased to a minimum on the fifth day, followed by a relatively stable low levels.In studying on spray timing, the results indicated that the appropriate timing to spray LJH25 is 1d before inoculating, the control efficacy to Pyricularia grisea reached 64.56%.The. fermentation supernatant of LJH25 was found to inhibit the germination of spores, scanning electron microscope (SEM) observations suggested that mycelium of P. grisea was dissolved, breaked, distorted, shrinked and formed other teratogenic effects.