Preparation For Wettable Powder Of Bacillus Subtilis D-29 And Its Application As Biocontrol Agent

Endophytic Bacillus subtilis D-29 isolated from Kochia scoparia had strong antagonistic activity against Exserohilum turcicum, Botrytis cinerea and Monilinia fructicola. A series of research on the optimization of solid-state fermentation condition, preparation of wettable power and biological control effects of Bacillus subtilis D-29 were conducted in the project. The results were as follows:1. Solidstate fermentation medium and fermentation process conditions of D-29 were optimized by orthogonal test. The contents of ingredients of solidstate fermentation medium were confirmed as follows: wheat bran:rice husk:corn flour:soya bean meal=12:3:1:3 and moisture content was 60%. The results of fermentation conditions showed that the proportion of inoculation is 12%, dry matrix of loading is lOg /250mL flask, temperature is 32?, pH is 7.0 and the time of fermentation is 72h. Under optimizing, the number of spores of D-29 was reached to 1.64×1011cfu/g.2. Fermentation liquor of Bacillus subtilis D-29was prepared on the foundation of solidstate fermentation. In order to develop the formulation of wettable powder, the carriers, wetting agents, dispersers, stabilizers and ultraviolet protectors were screened. The raw powders of Bacillus subtilis D-29 were prepared by jet milling the mixture of vermiculite power. The ingredients of the wettable powder (WP) for mulation of D-29 were confirmed as follows:91.0%raw powder,4.8% 9500 as wetting agent, 3.2%FM-6 as dispersing agent and 1.0% SDS as UV protection agent. The quality detection showed that the sporecontent is 1.5×1010cfu/g, mixed microbe rate is 0%, pH is 7.2, fineness is greater than98.1%, dry decrement is 1.5%, wetting time is 48.0s and suspension rate is 93.7%. The WP formulation of D-29 was up to the national formulation standard had no toxicity on plants.3. The WP of D-29 diluted 103 times could improve tomato seed germination rate, promote the growth of roots and sprout, and promote the increasing of height, stem diameter, and dry weight of tomato plant. Apples were stored for 90d in 4? or 35d in 25? after been soaking in 103 times dilution of WP D-29 and the disease rate was 5.5% and 33.3%, the water loss rate was 3.5% and 5.7%, the corresponding CK groups was 44.4% and 52.4%, the water loss rate was 3.5% and 7.1%, respectively.103 times dilution of WP D-29 has significantly preservative and fresh-keeping effects. WP D-29 103 times dilution was applied in apples soaked in the spores suspension of Monilinia fructicola or Colletotrichum. The biological efficacy was 87.5% or 61.5% after 24d respectively.