Epidemiology For Basal Stem Rot Of Wheat Caused By Microdochium Majus

Microdochium majus can cause wheat basal stem rot,which seriously affects the yield and quality of wheat.In the wheat-growing area of Ma anshan in Anhui Province,light brown or dark brown lesions on the wheat stem section can be observed caused by the pathogen,and the surface of the stem showed brick red mold and white hyphae,which was similar with symptoms caused by Fusarium graminearum.Because both Pathogenic bacteria conidium morphology are similar,making it difficult to identify in the field,it delays the optimal control of the disease.Therefore,the disease diagnosis and pathogen identification were carried out in this paper.Moverover it was clarified that the biological characteristics,disease infestation,straw returning rate,toxin content and effective drug screening of the pathogen were studied,and the occurrence characteristics as well as effective control of the disease.Not only finds the method and the appropriate period,but also the study provides important theoretical basis and practical reference for the early warning or prevention of the disease.The main findings of the paper are as follows:1?Isolation and identification of pathogenic bacteria.The isolates from the wheat-growing areas in Ma'anshan City of Anhui Province were identified.Six isolates were identified by both morphological observation and molecular biological methods.By the way the result is these strains were the pathogen named M majus.It is the first time that the pathogen has been found in China to cause wheat basal stem rot that proved by the Koch rule.2?Biological characteristics of wheat basal stem rot pathogens.The optimal temperature for growth of pathogenic mycelium is 16-23?,the suitable pH is 7 as well as The best carbon source is sucrose instead of the pathogen's hyphae grew thin on sorbitol-based medium.The best nitrogen source was sodium nitrate,followed by histidine.The optimum temperature for sporulation of pathogenic bacteria is 28?,while the optimum pH is 7.In addition,and the hyphae grow thin on alnedium in which sorbitol is a carbon source.The best nitrogen source is sodium nitrate,followed by histidine.After 20 cm deep returning,the M majus has the longest survival time on corn stalks but not more than 14 d,besides the survival time on wheat straw not more than 10 d.M.majus without soil covered survived less than 18 days on corn and wheat.It could not be invaded on rice,soybean and cotton stalks in any environment.3.Characteristics of pathogen infection.The wheat basal stem rot caused by M.majus can occur throughout the growth period of wheat growth,which may infect from the leaf sheath of each leaf mainly,the ear secondly.From February to March,M.majus infects wheat from the sheath with browned base and yellow leaves.At the jointing stage,the infection will lead to dark brown lesions in the stems.Mrhite or pink mold layer can be seen on the stem section when wet.Both methods are infected slowly.If inoculated panicles after May,it resulted in black panicles,even white ears appeared and the pathogen rapidly spread to the stem section to cause dark brown spots when seriously.4.Toxin-producing ability of pathogenic bacteria.In the flowering stage of wheat,the spore suspension was inoculated ears by the inoculation method,then diseased ears were collected to obtain toxin extraction.It is LC-MS to be used to evaluate the content of DON toxin in wheat grain.At the same time the inoculation difference between the inoculated F.graminearum PH-1 and M.majus 1:1 was compared.The results of toxin determination of wheat grain showed that(1)wheat inoculated with M majus had no 3A-DON,15A-DON and ZEN toxin;(2)wheat with vaccination F.graminearum PH-1 had the highest toxin content,with the average value of 3690.47.?g/kg;the DON toxin content of wheat inoculated with M.majus was the second,with an average of 696.69?g/kg;while the mixed dose of PH-1 and M.majus 1:1 was the lowest,with an average of 94.48 ?g/kg.5.Screening of effective fungicides.In order to select a fungicide with better effect on wheat basal stem rot,7 kinds of fungicides were selected to carry out indoor virulence determination,efficacy control test of M majus was also under way.The results of laboratory virulence assay showed that tebuconazole,L-propionazole and 95%meconazole strongly inhibited mycelial growth with EC50 of 0.1727 ?g/mL,0.2338 ?g/mL and 0.4878 ?g/mL,respectively.The amide,cymene and ketone-family inhibited the growth of pathogenic bacteria at a certain concentration,and the EC50 was 0.9216?g/mL,0.9723?g/mL and 1.4900?g/mL,respectively.Carbendazim is less effective,of which EC50 is 7.611 ?g/mL.The comprehensive analysis showed that the drugs with good control effect on stem-based rot were tebuconazole,prothioconazole and meconazole.