| As an economic crop,cotton is an important strategic material in my country.However,the serious damage of Verticillium wilt led to a large-scale reduction of cotton yield and quality.Cotton Verticillium wilt is a soil-borne vascular disease caused by Verticillium dahliae Kleb.It is called "cancer" of cotton,causing plants to wilt or even die.The chemical control currently used in production can have a certain control effect,but it will cause serious damage to the ecological environment.It is particularly important to use more efficient and ecologically friendly biological control methods.This study intends to screen and develop efficient antagonistic bacteria to prevent and control cotton verticillium wilt,so as to curb the harm of the bacteria and protect the environment,so ensure the healthy and sustainable development of my country’s cotton industry.In order to find the best biocontrol agent,the antagonistic bacteria obtained from the high-resistance cotton plants identified in the disease garden were used for screening and identification,and the effect of preventing and controlling Verticillium wilt was evaluated.The susceptible variety Xinluzao 36 was used as the experimental material;the Xinjiang Verticillium wilt strain(Vd592)was used as the test strain,and the following experiments were obtained through morphological,physiological and biochemical,molecular biology and greenhouse control effects.in conclusion:1.Extract and purify the screened strains,observe the diluted and coated plates,the colonies are white,irregular in shape,irregular in edge,flat,smooth,shiny,and sticky in texture;carry out physiological and biochemical identification and Gram Staining,the strain conforms to the characteristics of Bacillus;the DNA of the strain was extracted for 16 s r DNA amplification,and the sequencing results were compared and analyzed by BLAST on NCBI.It is XJSAS1(Bacillus saffrod),which belongs to the family Bacillus and the genus Bacillus.2.Using the plate confrontation test,it was found that XJSAS1 can inhibit the growth of V.dahliae,and the maximum antagonistic effect was achieved after the 21 st day of the test;the 48 h growth curve was measured again to find that it reached the best concentration between 14 and 16 h;cephalosporin,penicillin tests found that antibiotics can inhibit the growth of XJSAS1 strains.3.Through the greenhouse control effect test,it was found that when the OD600 of the strain is 0.6,the method of soaking the seeds can achieve the maximum disease resistance effect.Bacillus and V.dahliae were extracted from cotton hypocotyl.The extracted Bacillus was subjected to another round of control effect test,and the control effect was 76.47%,with no significant difference;using the concentration of0.1～1.0 to test the seed germination of XJSAS1,it was found that the concentration of OD600 was 0.1when the germination promotion efficiency was the highest,which was 55%,higher than that of the clear water control group.When the OD600 was higher than 0.6,the germination-promoting efficiency was reduced,but it could still basically germinate after 9 days.The control effect test showed that XJSAS1 had the best antagonism effect against Verticillium wilt when OD600 was 0.6,and the low concentration of XJSAS1 could promote seed germination.4.By analyzing the complete map of XJSAS1 bacteria,using GO annotation,KEGG annotation,COG annotation,TCDB annotation,CAZy annotation and methylation circle map analysis,the metabolic activity in the genome of XJSAS1 is strong,indicating that it has a strong survival and Reproductive ability;strong sugar-degrading ability,can quickly decompose the cell wall of V.dahliae.Based on the analysis of the above content,the Bacillus XJSAS1 obtained from the severely diseased cotton fields in Xinjiang was identified as Bacillus saffrod by morphology,physiology,biochemistry and molecular biology.The occurrence of verticillium wilt and the promotion of the germination rate of seeds can be prepared as a biological inoculum for agricultural production. |
