Isolation,Identification Of Pathogens And Chemical Control Of Buckwheat Stem Canker Caused By Rhizoctonia Spp.

Buckwheat stem canker is a kind of soil borne fungal disease,which reduces buckwheat yield.In this study,the incidence of buckwheat in 16 counties of Inner Mongolia,Shanxi,Sichuan,Yunnan and Guizhou provinces was investigated.At the same time,the disease samples were isolated and identified,and the toxicity test was carried out.Therefore,the occurrence of buckwheat stem canker,isolation and identification of pathogenic bacteria and chemical control were studied in this paper,and the following conclusions were drawn:1.In this study,the occurrence of buckwheat stem canker was investigated in 9 areas of Inner Mongolia,Shanxi,Hebei,Jilin,Sichuan,Yunnan,Gansu,Ningxia and Guizhou.The pathogen isolation and identification were carried out for some samples from 5 provinces and regions.The results of field investigation were as follows:Tongliao was the most serious area,and the disease index was as high as 83.6;followed by Ulanhot with a disease index of 55.12;again The disease indexes of Youyu,Chifeng and chayouqianqi in Shanxi and Inner Mongolia are respectively 46.55?35.85?35.22.2.In this experiment,41 isolates were isolated from the diseased plants collected from 16 counties in 5 provinces.37 of them showed the same symptoms when inoculated to buckwheat,and the other 4 showed the same symptoms.The results of pathogenicity test showed that 37 isolates were pathogenic bacteria of buckwheat stem canker,and the remaining 4 were non pathogenic bacteria.The symptoms of infection of 37 strains of pathogens in the lower part of buckwheat were brown to dark brown oval spots at the base of stem,and the symptoms in the upper part of buckwheat were chlorosis,yellowing and even shrinkage of leaves.Among the 37 pathogens,CBWR3 was the most virulent in Chifeng,followed by WBWR5 in Ulanhot and TBWR2 in Tongliao.3.The results showed that 37 isolates were divided into two groups:Binucleate Rhizoctonia,Rhizoctonia solani,AG-4,AG-5,AG-A,The results of Molecular identification showed that 26 strains belonged to the fusion group AG-A,AG-K,AG-4,AG-5,among which 1 strain belonged to the fusion group AG-4 HGI,2 strains belonged to AG-4 HG?,and the remaining 6 strains belonged to Rhizoctonia.4.14 kinds of fungicides were selected to test the virulence of the trichoderma bacteria causing buckwheat stem canker disease in the laboratory,and the results showed that:40g/ml Fluosilazol,25g/L Roflonitrile,40%Fumei·mixingling these three agents had a significant inhibitory effect on buckwheat stem ulcer bacteria,EC50 were 15.8489,41.6869 and 85.1138 respectively.The results of field control experiment of 14 kinds of fungicides showed that:40g/mL Fluosilizole,25%Pyrazole,40%Fumexidilide and the three kinds of fungicides had better control effect on buckwheat stem canker disease,respectively:71.4%,64.5%and 63.1%.Combined with the indoor toxicity test,the results showed that the best field control effect of 40 g/mL Flusilazole 2000 times solution and 40%Fumei·bibixianling 3000 times solution was 64%and 63%,respectively.