Pathogen Identification Of Root Rot In Pear Plant And Fungicide Screening For Its Efficient Control

In recent years,a kind of serious plant disease arised on the Chinese pear in area of the Ancient Yellow River Valley.At primary stage Leaf etiolation,margin dried up,the whole plant leaves,plants die.Initially treated as deficiency syndrome treatments but have no effect.Cause some pear plant disease mortality rates as high as 20% above,to the local pear industry caused serious economic losses.To identify the pathogen causing root rot of pear plant in the region of the Old Yellow River Valley,and screen out effective chemicals from 18 fungicides commonly used.The pathogens were isolated from the tissues of root samples of diseased pear plant and purified by the single spore culture method.The pathogens were identified according to the morphological characters,rDNA-ITS analysis,pathogenicity tests of strains.The 18 fungicides efficient for suppressing the pathogens were evaluated by calculation of the inhibition rate of mycelium growth and spore germination,and a part of the fungicides were selected for the pathogens control in field trials.and their chemical inhibitory effects were observed.The main results obtained in this experiment were as follows:1.The results showed that the early onset of plants mature leaf margin withered,Then the blade die off,and send out new leaves,serious in the whole plant is death,but not the onset of plant leaf color is normal.2.Pathogen morpha and studies on pathogenicity: Four strains were isolated and purified from the root samples and were identified as the same pathogen by morphological characteristics and rDNA-ITS analysis.Furthermore,in cooperation with the pathogenicity test,the pathogen was determined as Nectria haematococca,its anamorph was Fusarium solani.rDNA-ITS sequences of the four isolates were homologous up to 100% with Fusarium solani strain YQC-C5(KF939490.1)and Fusarium solani isolate AM(KR909201),accessed in NCBI database.It was confirmed that the four isolates belonged to the same pathogen of Root rot,which should be named as Fusarium solani.3.Antibacterial test results showed that 72% cymoxanil + mancozeb,1.8% ametoctradin acetate and 80% mancozeb have good inhibition on both mycelium growth and spore germination of Fusarium solani.Although 80% copper sulfate,3% benziothiazolinone,75% chlorothalonil had poor inhibition on mycelium growth,they had very strong inhibition on spore germination of Fusarium solani.4.The virulences of the four fungicides to Fusarium solani mycelium growth were tested in laboratory showed that 95% pyraclostrobin and 80% mancozeb had the best inhibitionon mycelium growth of Fusarium solani,then 72% cymoxanil + mancozeb,1.8%ametoctradin acetate was the worst.After these fungicides had been applied in field,72%cymoxanil + mancozeb,1.8% ametoctradin acetate and 80% mancozeb had better control of the disease than 95% pyraclostrobin.The root rot of pear plant occurred in the region of the Old Yellow River Valley were caused by the fungus Nectria haematococca,their anamorphs were Fusarium solani.There was a significant difference between the treatments with different chemicals for the inhibition of mycelium growth and conidium germination,and there was also a significant difference between the treatments with different chemicals for the laboratory test and field experiment.