Isolation And Identification Of Pathogen Of Cryptomeria Red Blight And The Screening Of Indoor Pesticide Reagents

Cryptomeria fortunei Hooibrenk ex Otto et Dietr is the evergreen conifer of Cryptomeria in the family Tnxodineene.It is an excellent garden species because of its fast growth,great longevity,high crown and graceful shape.Cryptomeria fortunei is also an important economic species widely used in furiture,farm tools,construction,bridges owing to its traits(trunk straight,texture straight,light material,shrink small,not crack,good adhesion,corrosion resistance,easy to handle).Cryptomeria fortunei,as an important economic tree species,is widely planted in Sichuan province.The damagement of red blight of Cryptmeria fortunei is serious,and cause enormous economic losses.In this paper,samples,the red blight-infected Cryptomeria fortunei trees were investigated from Ya'an city(Tianquan County and Lushan County)in Sichuan province.Morphological characteristics of the pathogen of red blight of Cryptomeria were examined.In accordance with organizational separation,the pathogen of red blight of Cryptomeria fortunei was purified by pure culture strains.By morphological characteristics and molecular biology method,Pestalotiopsis foedans was identified as a stain.In order to discuss the growth and reproduction conditions,the biological traits of pathogen were further studied.Combined with field control technology,the indoor efficacy test was looking for chemical pesticides which had a better effect on the inhibition of pathogen.The results of the study are as follows:Firstly,the red blight is caused by Pestalotiopsis foedans.The fungus strains were isolated from the infected leaves.On the basis of the ITS sequence and P-tubulin gene sequence analysis,the pathogen was identified as Pestalotiopsis foedans.Secondly,Pestalotiopsis foedans has an adaptability to the acid and alkali stress since the mycelium and conidium of the pathogen could grow well and germinate in the range of pH 4-10.The optimal temperature for growth and germination was 25?.The germination rate of conidium was affected by humidity,with more than 90%germination rate when the humidity kept over 90%.Fungal hyphae was able to grow well under continuous or intermittent light.Therefore,the high temperature and humidity are conducive to conidium germination and the mycelium growth,resulting in more serious disease.Thirdly,there was a stable and high inhibition ratio for 70%thiophanate-methyl wettable powder(WP),with 4.57 ?g/mL EC50 value,followed by 50%carbendazim WP.However,the antibacterial effects of 275%chlorothalonil WP and 15%triadimefon WP were reluctant and the EC50 values of these two fungicides were 262.426?g/ml,793.51?g/ml,respectively.