Study On Microbial Agents Controlling Soil-borne Diseases And Fermentation Condition Of Bacillus Velezensis NT35 In Fermentation Tank

As a type of plant disease,soil-borne diseases mainly endanger the roots and stems of plants,hampering seriously agricultural production.Intensive production characterized by the simplified cropping pattern of crop types and the high multiple-crop index.Lead to the problems of soil-borne diseases frequently.As is known to all,soil-borne diseases are difficult to prevent and control.At present,the main method is still by chemical control but the control effect is not environmental friendly,and there has residual problems.Especially some high-yield and perennial cash crops such as soybeans,cotton,tobacco,ginseng,American ginseng and vegetables.Our country is guiding the development of the bio-industry,especially in the agricultural sector,where Chinese land does require microbial products.In this study,eight different kinds of microbial fungicides were tested on the ginseng seedling disease and root rot disease,and the indoor virulence test and field efficacy test of four microbial agents against Fusarium oxysporum On the basis of the field control effect,in order to improve the viable liquid concentration of B.velezensis NT35 fermentation broth and reduce the production cost,the fermentor to carry out the conditions of biocontrol strain.These results are as follows:1.EC₅₀0 of diferent tested microbial fungicides against Fusarium oxysporum,Fusarium solani and Ilyonectria robusta were 0.342⁸0.520 mg/L?0.202⁷1.788 mg/L and 0.187⁶1.083mg/L.10⁹ CFU/g FG14 WP has the lowest EC₅₀ value for tobacco root rot and ginseng root rot,and has a good inhibitory effect;10⁹ CFU/g NT35 WP has the lowest EC₅₀ value for ginseng rust rot and has a good inhibitory effect.2.The effects of four microbial fungicides on the control of F.oxysporum and agronomic traits of tobacco were determined by root irrigation.The second survey stated that the average control effect of the test agents was 42.93⁸2.94%.It was found that different doses of 10⁹ CFU/g NT35 WP was 63.60%⁷0.19%.And tobacco has a significant promoting effect,the weight of fresh tobacco leaves is increased by 14.11%⁶5.77%.3.The three different treatment methods by adopted experiment,the effect of eleven kinds of fungicides on the field control of root rot diseases in ginseng seedling stage and adult stage were studied.The results showed that the average control effect of the test agent on ginseng seed treatment was 29.74%⁶7.34%,and the control effect of 62.5 g/L metalaxylm fludioxonil 300mL/100 kg was the best;The average control effect on soil treatment was 47.25⁷7.95%,10⁹CFU/g NJ13 WP 6 g/m² control effect is 74.35%;The average control effect on the treatment of seeds and soil was 48.78⁸0.07%,and the best control effect was 62.5 g/L metalaxyl^m fludioxonil 300 mL/100 kg+6 g/m².5×10⁹ CFU/g Bacillus polymyxa.The average control effect of the test agent on the planting treatment was 29.41⁶6.94%,and the control effect of 62.5 g/L metalaxyl^m fludioxonil 300 mL/100 kg was the best;the average control effect on soil treatment was 61.1⁷1.72%,10⁹ CFU/g NT35 WP 6 g/m²The control effect was the best;the average control effect on planting and soil treatment was 40.84⁸0.32%,and the control effect of 62.5g/L metalaxylm fludioxonil 300 mL/100 kg+5×10⁹CFU/g Bacillus polymyx 6 g/m²was the best.Screening out microbial agents that effectively control the root disease of ginseng.It has been proved by experiments that the chemical pesticide dressing and microbial fungicide mixed soil treatment has higher control effect than the seed treatment and soil treatment alone,reducing the application of chemical agents and less pesticide residues,is of great significance to the ginseng industry.4.The optimum fermentation conditions for the biocontrol strain NT35 were determined by shake flask fermentation to be 6%inoculum,temperature 34°C,rotation speed 180 rpm,initial pH 7.0.The fermentation conditions of the biocontrol strain NT35 were explored by step-by-step amplification of 5L and 30L fermenter.When the tanking time of 30L fermenter was 20 h,the viable count reached 6.32×10⁹ CFU/mL,which increased with the shake flask fermentation level by 15.8 times,and the inhibition zone of ginseng rust fungus was 21.17 mm.The level increased by 15.8 times and the bacteriostatic activity increased.