Preparation Of Synergistic Antibacterial Wettable Powder And Its Application In Tobacco Bacterial Wilt

Tobacco,as one of the main economic crops in China,has been infested with various diseases and insect pests,causing huge yield and economic losses to tobacco production,especially the soil-borne disease bacterial wilt,which has been called"cancer"of tobacco.In order to decrease the tobacco damage caused by bacterial wilt,this study is devoted to exploring a biological method——compound Bacillus wettable powder that is more efficient than chemical agents,has no pollution to the environment,and does not generate drug resistance.Thus,providing a more effective way for the rich harvest and sustainable development of tobacco.In this study,four Bacillus strains with inhibitory effects on tobacco bacterial wilt pathogens were chosen as the research objects.The four strains were subjected to a plate confrontation test and the fermentation medium was optimized.Wettable powders were then prepared.Finally,greenhouse and field experiments of the compound Bacillus wettable powders on tobacco were conducted.Results are below:1.The water extract of marigold rhizome has a certain inhibitory effect on tobacco bacterial wilt.So,it could be added to the preparation of wettable powder.2.The four antagonistic bacteria YH-22,ZH⁺,ZM9 and 3-10 of tobacco bacterial wilt have good adaptability to the antibacterial substances marigold rhizome extract,chitosan and amino-oligosaccharin.Taking both the cost and quality issues into account,10 g/L marigold rhizome extract,chitosan and amino-oligosaccharin were added to the wettable powder.3.The optimized medium formula of compound antagonistic bacteria is:corn starch 40.0 g/L,soybean meal 70.0 g/L,KH₂PO₄ 2.00 g/L,Mg SO₄·7H₂O 0.50 g/L,KCl 0.50 g/L,Fe SO₄·7H₂O 0.10 g/L,30℃and initial p H 6.5.4.Through the plate confrontation experiment between the four strains,it was found that ZM9,3-10,ZH⁺and YH-22 have no antagonism with each other.In order to increase the antibacterial effect of the wettable powder,10 g/L marigold rhizome extract,chitosan and amino-oligosaccharin were added to the compound antibacterial agent.Then add diatomite and bran（1:4）as the adsorption carrier of the agent,1.5%sodium lignosulfonate as the auxiliary of the agent,and 2%CMC-Na as the stabilizer of the agent.Finally,a compound Bacillus wettable powder with inhibitory effect of tobacco bacterial wilt was formed.The bacterial rate,temperature stability,light stability and p H stability of the agent were tested.Pot and field experiment of compound Bacillus wettable powder were also conducted.5.The compound Bacillus wettable powder（T1）,compound antagonistic bacterial agent（T2）and chitosan（T3）were separately applied to potted tobacco.Each experimental group had a certain inhibitory effect on the pathogen of tobacco bacterial wilt,and number of bacterial wilt in the soil was smallest when applied compound Bacillus wettable powder;the incidence rates of the tobacco bacterial wilt of CK,T1,T2 and T3 were 87.33%,15.33%,20.67%and 44%respectively,and the control effect of T1 on bacterial wilt was 60.87%.The agronomic traits of tobacco such as plant height,maximum leaf length and stalk diameter were measured,it can be concluded that the application of wettable powder has increased the growth of tobacco,and achieved the purpose of increasing yield.The effect of the agent on the germination of tobacco seeds showed that it can increase the germination rate of tobacco seeds by 10.43%.6.The prepared compound Bacillus wettable powder was applied to the tobacco field test,and the compound antagonistic bacterial agent and chitosan were used as controls.The results showed that the control effect of the agent on tobacco bacterial wilt reached 67.13%,improved the physical and chemical properties of the soil,accelerated the economic properties of tobacco leaves,increased the microbial diversity of its rhizosphere soil and changed the relationship between soil physical,chemical properties such as N,P,K and organic matter,soil microorganisms.So,we could conclude that:1.Synergistic antibacterial agent could promote germination and growth of tobacco seeds;2.Synergistic antibacterial agent could significantly enhance the control effect against tobacco bacterial wilt in pot experiment;3.Synergistic antibacterial agent had a great control of tobacco bacterial wilt;improved the soil physical and chemical properties and microbial structure;adjusted the soil metabolites and abundance of beneficial bacteria and antagonistic bacteria to achieve the effect of preventing tobacco bacterial wilt in field experiment.