| Cotton wilt is one of the most serious problems faced by the cotton industry,seriously affecting the yield and quality of cotton.Among the control methods of cotton wilt,biological control is considered as one of the most promising modes of cotton wilt control because it is not easy to make the pathogenic bacteria develop resistant and is friendly to the environment.Plant growth promoting rhizobacteria have the ability to promote growth and disease resistance and are also being used more and more widely in agricultural production.The isolation of multifunctional and highly efficient plant growth promoting rhizobacteria and their application to the control of cotton wilt can not only improve the yield and quality of cotton,but also promote the green and environment-friendly development of agriculture.Bacillus is an important component of soil microorganisms,which can form endospores and thus enhance the survival of the strain in the adversity.In addition,Bacillus has great potential to promote crop growth and improve crop resistance to diseases,and therefore,it is gradually becoming a widely studied class of biocontrol microorganisms.Chitosan,as a plant immunoantagonist,has the characteristics of promoting plant growth,reducing the use of pharmaceuticals,environmental protection,and potential disease resistance.However,there are relatively few studies on the effect of chitosan and rhizosphere microbe on cotton wilt.Therefore,in this study,the effect of cotton growth promoting rhizobacteria and chitosan on cotton wilt was characterized.The main results of the study are as follows:Eight strains of Bacillus with antagonistic ability against cotton wilt were isolated from the rhizosphere soil of cotton in Xinjiang,and a strain of Bacillus amyloliquefaciens KW5 with highly effective antagonistic and probiotic functions was obtained by measuring the growth inhibition performance and probiotic ability(nitrogen fixation,phosphorus solubilization,iron carrier production,and indole acetic acid production)of the cotton wilt.KW5 inhibited cotton wilt up to 65.5% and had the ability to decompose inorganic phosphorus as well as the ability to produce IAA and iron carriers.The strain KW5 was positive for nitrate reduction,gelatin liquefaction and starch hydrolysis experiments,and had a salt tolerance of 13%.The most suitable nitrogen source for KW5 growth was beef paste,the most suitable carbon source was glucose,and the optimum temperature was 26℃-30℃.In terms of disease resistance,inoculation with KW5 or application of chitosan reduced the incidence of the plant,with control effects of 21% and 37%,respectively.And the effect of combined application of chitosan and KW5 was better than that of single application,with control effects of 53%.In terms of promoting plant growth,under the conditions of cotton wilt infestation,the combined application of KW5 and chitosan increased the plant height,aboveground fresh weight,aboveground dry weight,main root length,and root dry weight by198.28%,97.14%,192.72%,64.79%,and 176.66%,respectively,and the maximum leaf area,leaf number,chlorophyll content,stomatal conductance,transpiration rate,and net photosynthetic rate increased by 65.47%,42.91%,20.32%,53.47%,252.36%,162.32%,respectively.SOD,POD and CAT activities increased by 102.31%,22.43% and 525.51%,respectively.MDA content decreased by 34.64%.Soil p H and conductivity decreased by4.83% and 15.77%,and soil AN,AP,and AK contents increased by 3.06%,20.88%,and 9.6%,respectively.In conclusion,the combination of B.amyloliquefaciens KW5 and chitosan was effective in controlling cotton wilt and promoting cotton growth.This study provides a highly effective combined microbial-chitosan control measure of cotton wilt,and provides theoretical support for the development of high value utilization technology of functional strains and improvement of cotton disease resistance and growth. |
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