Pathogenicity Of Colletotrichum Species Causing Anthracnose Of Camellia Sinensis And Their Sensitivity To Four Conventional Fungicides

Tea is loved by consumers in various countries because of its unique taste and health care function.China is the largest tea producing country in the world.Meanwhile,tea was regarded as main foreign exchange earning agricultural product in our country.Anthracnose caused by Colletotrichum is one of the most severe diseases in tea plants,mostly occurs in tea leaves.The disease can occur tea plants from all tea areas in China.The commercial tea plantations of Zhejiang,Fujian and other parts have been seriously damaged.The leaves fall off in severe cases,resulting in the reduction of tea production and quality.China has a wide area of tea plantation and rich in germplasm resources.Although some progress has been made in combining agricultural measures with pesticide,anthracnose in tea plantations still occurs from time to time.In this study,the diseased leaves of tea plants showing anthracnose symptoms were collected from Jiangsu,Zhejiang,Yunnan,Guangdong,Fujian,Hunan,Sichuan,Jiangxi,Hubei,Henan,Chongqing and Shandong provinces.The mycelial agars of strains were inoculated on isolated branches of different varieties of tea trees,to explore the difference of pathogenicity between different varieties/strains.Furthermore,the sensitivity of four conventional agents was tested.The research progress is summarized as follow:1.Isolation and identification of anthracnose on Camellia sinensis In this study,a total of 57 strains were isolated from the diseased leaves of tea plants showing anthracnose symptoms,from commercial tea plantations of 12 different provinces in China.According to the colony morphology,conidia and appressorium characteristics of the isolated strains on PDA medium,they were divided into five types.21 representative strains were selected for further sequencing and phylogenic analysis based on six gene loci?ITS,TUB2,ACT,CAL,CHS-1 and GAPDH?.The results showed that the tested strains all belonged to Colletotrichum gloeosporioides complex,including seven strains of C.fructicola,eight strains of C.camelliae,three strains of C.siamense and three strains of C.aenigma.2.Analysis the pathogenicity of Colletotrichum Species causing anthracnose on different tea varieties/strains To explore the relationships between the infection of tea anthracnose disease and different leaf positions,the mycelial agars of YN23,FWY43 and CHQ-2 were inoculated into the first,second,third,fourth,fifth,and fifth and sixth leaves of‘C.sinensis cv.Shuchazao'by needling inoculation method.Meanwhile,22 varieties?strains?of tea trees were collected from Lujiang experimental station in Hefei city,Anhui province to analysis the pathogenicity of Colletotrichum Species causing anthracnose on different tea varieties/strains.The mycelial agars of six strains were inoculated on isolated branches of the collected tea trees by acupuncture inoculation.The results showed that the incidence of leaf at the third,fourth,fifth and sixth leaves of‘C.sinensis cv.Shuchazao'was more severe than the first and second leaves at 21 days after inoculation.At 21 days after inoculation,the strains of C.fructicola?C.camelliae?C.siamense?C.aenigma had poor pathogenic effects on‘C.s.cv.Juhuachun',‘C.s.cv.Zhenghedabaicha',‘C.s.cv.Fuyun 6',‘C.s.cv.Zhongcha 108',‘C.s.cv.Xiuhong'and‘C.s.cv.Echa 5',and the diameter range of the lesion is 0.3-0.61cm.‘C.s.cv.Zhenong 117',‘C.s.cv.Wancha 91',‘C.s.cv.Fuding Dabaicha',‘C.s.cv.Dangui',‘C.s.cv.Baihaozao'and‘C.s.cv.Juhuachun'showed high sensitivity.3.Sensitivity of four conventional agents In this study,c.camelliae was inferred that this pathogen was one of the dominant species of tea anthrax,and it had a high frequency of separation in the commercial tea plantations investigated.In this study,the sensitivities of 8 strains to 4 fungicides were measured by the mycelial growth rate method.The results showed that the C.camelliae was sensitive to difenoconazole with the EC₅₀values of 0.0584?0.4984?g/m L.Pyraclostrobin and thiophanate-methyl had certain inhibitory effects on the C.camelliae,with the EC₅₀values of 0.0409?1.5442?g/m L and 0.0232?0.9466?g/m L respectively,but the sensitivity of each strain to these two agents was quite different.Moreover,the isolates were less sensitive to chlorothalonil,with the EC₅₀values of 0.3810?93.2890?g/m L.The sensitivity of the tested strains to chlorothalonil was significantly different.