The Effect Of Resistant Screening Atseedling Stage And The Biocontrol Of Viride To Defoliated Verticilliumdahliae In Cotton

Verticillium wilt is one the most serious diseases in cotton production currently. The appearance of deciduous type strains of Verticillium wilt posed a more serious threat to the yield and quality of cotton. By the method of resistance transformation to cotton breeding for disease resistance is considered to be one of the most economical and effective method, while the biggest obstacle to carry out resistance breeding is the lack of resistance sources.Literature data indicated that the using of artificial nursery to continuous directional selection for improved resistance to Verticillium had been proven largely ineffective, which may closely related disease identification and screening methods. we conducted a resistance identification and screening to some cotton varieties which have certain resistant by the method of seedling resistance identification, which is based on water floating nursery techniques, to study the effect of screening, we hope that through continuous screening, we can bred source materials resistance to defoliating Verticillium wilt.In case of lack of resistant cotton varieties, the use of microorganisms on cotton Verticillium wilt is one of the promising and practical methods. We studied the mechanism through the control effect of two Viride strains to verticillium wilt, in order to provide a basis for biological control of Verticillium Wilt.1.We carried out disease identification to4deciduous type strains of Verticillium wilt to4cotton varieties for three batches, the results showed:the relative disease index was not significant between different batches of the identification results,the differences of virulence betweens trains was significant,Varietal resistance existed significant difference, there were significant interaction effect between strains and varieties, which showed that the method of dipping seedling inoculation based on water floating nursery, had good reproducibility.2.By seedling disease identification and screening we find that: In addition to individual materials, through seedling disease identification for one time, the relative disease index of varieties decreased significantly,decline between25%-30%. At the same time, resistance screening can significantly improve the transplant survival rate of inoculated cotton seedlings under the conditions of inoculation,with a range of30%-65%. Therefore, the method of seedling resistance screening had good effect to the improvement of cotton’s resistance.3.By tablet confrontation experiments and inhibition experiments found that: Viride T-14,T-17colonies have a good inhibition to Verticillium wilt, inhibition rate reached an average of55.1%and51.2%; the inhibited rate of Viride metabolic liquid to verticillium wilt HB-13were64.2%and71.9%respectively, the inhibitory effect is significant. Viride can induce cotton produce higher levels of POD and SOD activity.We treated cotton seedlings with Viride,12hours later, inoculated them with verticillium wilt, then we can find that POD and SOD activity in the cotton leaves reach peak in the third day and second day respectively,Activity levels were significantly higher than the control and the treatment only Inoculated with Verticillium wilt, which showed that Viride can induce the systemic resistance of cotton.4.We studied the control effect of Viride to Verticillium by pot experiment, then we found that Viride can significantly improve disease resistance of Yumian21which has poor resistance and the average control effect reached43%, while the effect to KB3505is not obvious, which has a better resistance. We can conclude that Viride have some control effect to Verticillium, the quality of control effect may be related to the resistance of the materials themselves, the varieties which have better resistance, the control effect on them is less obvious.