A Study On Bio-control Agents Against Late Blight Of Potato

The potato late blight caused by Phytophthora infestans(Mont.)de Bary is one of main fungal diseases that harms potatoes.At present,potato late blight is mainly prevented and controlled by chemical pesticides,but the problems of environmental pollution,pesticide residues and drug resistance have become increasingly serious with the large-scale use of chemical pesticides,and a amount of chemical pesticides have been reduced or banned to use in agricultural production activities.Biological pesticide has the advantages of safety,no pollution and good compatibility with the environment.Therefore,biological control methods become the best way to control potato late blight.This article aims to seek for antagonistic bacteria that have great control effects on potato late blight,in order to provide theoretical basis for the study on bio-control agent of potato late blight.The antagonistic bacteria were selected according to their inhibition effects on growth of Phytophthora infestans via dual-culture method,and using their fermentation broth to further test the inhibition effects against potato late blight.The screened antagonistic bacteria Bacillus amyloliquefaciens D1,Bacillus amyloliquefaciens hd213 and Stenotrophomonas maltophilia he41 were used in pot experiment to test their control effects on potato late blight.In addition,the control effects of antagonistic bacteria D1,hd213 and he41 on potato early blight were also detected.The main results were as follows:1.The inhibition rates of strains D1,hd213 and he41 that selected from seven bacteria viz strains D1,H3,hd13,hd213,he41,he14,and DEB-2 via dual-culture method against potato late blight were 62.33%,66.67% and 52.67% respectively.2.The growth rate method was used to re-screen seven bacteria strains.The study founded that the antagonistic effect of strain D1 on potato late blight was the strongest,and the inhibitory rate of 2% of the fermentation broth on Phytophthora infestans was 92.31%.When the fermentation broth increased to 4%,the inhibition rate was up to 100.00%.The antagonistic effect of strain he41 on the pathogen wasthe next.When the concentration of fermentation broth was 32%,its inhibition rate against Phytophthora infestans was 100.00%.The antagonistic effect of strain hd213 on Phytophthora infestans was relatively weak,and the inhibition rate of 64%fermentation broth against Phytophthora infestans was 100.00%.3.Mixed fermentation was carried out on the premise of antagonism and coculture of seven bacteria strains.The results showed that there was no synergistic effect on the fermentation of mixed bacteria compared with the single strain fermentation.Therefore,a single strain fermentation broth was used in pot experiment.4.The results showed that the fermentation broth of D1,hd213 and he41 had different control effects on potato late blight,and the highest control effects on potato late blight were D1 69.50%,hd213 59.37% and he41 45.56% respectively.5.The inhibition rates of strains D1,hd213 and he41 on potato early blight were60.93%,51.67% and 64.00%,respectively.The fermentation broth of strain he41 had the strongest inhibitory effect on potato early blight,and strain D1 was the second,and strain hd213 was relatively weak.When the concentration of fermentation broth was 32%,the inhibition rates of each strain against potato early blight were he41100%.00,D1 100.00% and hd213 95.90% respectively.6.The strains D1,hd213 and he41 showed strong control effects on potato early blight in pot experiments.The best control effects of the fermentation broth were D166.54%,hd213 59.37% and he41 72.86% respectively.