Pathogenic Mechanism Of Two Kinds Of Cotton Seedling Diseases Caused By Toxin And Preparation Of Seed Coating Agent

Cotton is an important economic crop in Xinjiang.Cotton rhizoctoniosis and cotton Fusarium red rot is the most important seedling disease in cotton production in Xinjiang.In order to improve the level of prevention and control of cotton root rot diseases at seedling stage,and promote the research on the technology of reducing pesticide application and increasing efficiency of cotton in Xinjiang.The main purpose of this study was to explore the pathogenic mechanism of pathogen toxin and suggest the main rules of the two diseases through the investigation on the occurrence,distribution and dynamics of cotton seedling blight and red rot in the eastern part of Xinjiang.The disease control agents were screened by the toxin stress of two pathogens,and the seed coating agents in line with the national industry standards were prepared for the control of cotton root rot diseases.finally,the effect of the self-developed seed coating agent on the control of cotton root rot was investigated by indoor inoculation and field control effect.The main research results are as follows:1.The results of disease investigation carried out in the main cotton planting areas in eastern Xinjiang in 2018 and 2019 showed that the incidence of Rhizoctonia solani was common in eastern Xinjiang,and red rot only occurred sporadically,and the disease varied greatly in different cotton areas.the incidence of root rot disease was the most serious in Yizhou District of Hami City,followed by Shanshan County,Toksun County and Gaochang District of Turpan City,and showed obvious distribution characteristics of light in the west and heavy in the east.2.Cotton seedlings were treated with crude extracts of two kinds of pathogenic toxins after hydroponic culture for different times.The results showed that the wilting degree of cotton seedlings increased with the treatment time,and the relative electrical conductivity of cell leachate increased due to the increase of cell membrane permeability and electrolyte leakage in the root cells of cotton seedlings.The results showed that the wilting degree of cotton seedlings was aggravated with the treatment time,and the relative electrical conductivity of the cell leachate was increased due to the increase of cell membrane permeability and electrolyte leakage of the root cells of cotton seedlings.The activities of SOD,PAL,POD and PPO in cotton seedling roots increased at first and then decreased,and the highest activity appeared at 24 h after treatment.3.The screening results of fungicides with antitoxin effect by using the crude extracts of two kinds of pathogenic toxins showed that all the tested agents could increase the germination rate of cotton seeds in the process of toxin stress,among them,the seed soaking with carboxin and fludioxonil had the greatest effect on the germination index and vigor index of cotton seeds under the stress of Rhizoctonia solani and Fusarium verticillioides toxin,and had obvious inhibitory effect on pathogenic toxin.4.The type and ratio of wetting agent and dispersant were determined by L9(33)orthogonal experiment,and the processing technology of nitrile seed coating agent was determined through the study of adding order of each component,sanding time,emulsifying time and so on.The results show that the best combination of wetting and dispersing agents is that the content ratio of three wetting and dispersing agents GY-DS1301,GY-W07 and GY-D07 is 3.2 and 2.4,the sanding time of verapamil nitrile seed coating agent is 50 minutes,and the shearing and emulsifying time of high-speed shearing emulsifier is 30 minutes,and the qualified products are prepared in accordance with the technical standards of the industry.5.The growth rate method and germination test were used to investigate the bacteriostatic effect,safety and growth-promoting effect of different concentrations of nitrile seed coating agent on two kinds of root rot pathogens,and the disease prevention and yield increase were compared in the field.The principal component analysis showed that the seed coating agent with the ratio of 7.2:1.0 had the best effect on bacteriostasis,disease prevention,growth promotion and yield increase.Results of indoor inoculation experiments showed that the control effects on blight and red rot were 87.19%and 88.30%,respectively.the control effects on the two diseases in the field were 75.79%and 66.3%,respectively,and the yield increased by 9.11%.