The Study Of Potato Blackleg’s Pathogen,Primary Source Of Infection And Chemical Control

Potato blackleg is one kind of worldwide bacterial diseases when potatoes were in the production and storage period,which spreaded mainly through the infected seed potatoes.With the enlargement of planting area,the harm of potato blackleg has showed a trend of year-on-year increase,severely affecting the potato yield.Therefore,the experiment did the isolation and identification of pathogenic bacteria,biological characteristics determination,chemical control measures and the study of primary source of infection of potato blackleg,designed to provide the basis for reasonable and effective prevention and control of diseases.The results as folows:1.The diseased plants taken from Xilin Gol League in Inner Mongolia which were suspected to be infected by potato blackleg with blacken and cankered bases of rhizome were identified of pathogenic bacteria to be infected with Pectobacterium atrosepticum.2.According to the determination of the biological characteristics,the maximum amount of bacteria was found when P.melanophorus was cultured for 48h,and the optimum growth pH was 7.5;the optimum grow temperature was 28℃;the optimum carbon and nitrogen sources were D-xylose and potassium nitrate.3.Seven fungicides were selected to have inhibition to pathogenic bacteria.In the test of laboratory toxicity,3%Benziothiazolinone,20%Bronopol and 80%Ethylicin had a better depression effect,with EC50 values of 38.18,77.09 和 168.15 μg/mL,and all have a correlation of r>0.98.4.The results of security experiments of fungicides to seed potatos showed that there was no depression effect to seedling emergence at three concentrations of Bronopol,but the normal dosage was most effective whose seedling inhibition rate was-23.8%,and that there is a depression effect to seedling emergence at two concentrations of the other tested fungicides.The result of control effect tests in 2017 and 2018 showed that Benziothiazolinone seed dressing was most effective whose control effects were 75.20%and 70.35%,increasing production of 18.18%and 24.89%;Bronopol seed dressing,Ethylicin seed dressing and root-irrigation,Benziothiazolinone seed dressing’s control effects were between 52.24%to 68.60%.Comparing three application methods-seed dressing,furrow dressing and root irrigation,different treatment methods had significant differences,and the effects of seed dressing and root irrigation were better.5.The results of the primary source of infection test showed that the potato chunks from the diseased fields were replanted as seed potatoes after overwintering,the incidence rate was 40%;isolating P.atrosepticum from the overwintered diseased plant residues buried in the soil,in the test of the no diseased fields and no diseased potato chunks of diseased plant residues after overwintering,the incidence rate was 43.33%;continuing to plant no diseased potato chunks in the diseased filed,the incidence rate was 6.67%.The result showed that the potato chunks from the diseased plant residues and diseased fields,as well as the infected seed potatoes,could be the primary source of infection,but the bacteria in the diseased filed almost disappeared after overwintering that could not be the primary source of infection.6.The results of pot culture experiments for the effect of cutting knife on the spread of disease showed that using the knife with no sterilization after cutting diseased potatoes could cause 10%seed potatoes cankered and non-emergence,and the incidence rate of the disease was as high as 26.67%.The results of field experiments were consistent with the results of pot culture experiments.