Isolation And Identification Of The Pathogen Of Chrysanthemum Anthracnose In Anhui Province,Pathogenicity Determination And Screening Of Control Agents

Dendranthema morifolium（Ramat.）Tzvel.)is one of the top ten famous flowers in China and one of the four largest cut flowers in the world,with huge commercial value.Anthracnose caused by Colletotrichum reduced quality and yield of chrysanthemum.In this study,the pathogens of chrysanthemum anthracnose were isolated and identified,its biological characteristics and the pathogenicity were also tested.The sensitivity of Colletortrichum to 6 fungicides were determined.The main results are as follows:1.Isolation and identification of the pathogen of Chrysanthemum anthracnoseFifty-one Colletotrichum isolates were isolated from diseased tissues of chrysanthemum by tissue separation method.A multilocus phylogenetic tree of chrysanthemum anthracis was constructed by maximum likelihood method（ML）using ITS,ACT,GAPDH,TUB and CHS-1 gene sequences of 19 representative strains.And it turns out,The 19 isolates included 10 strains of Colletotrichum plurivorum and 5 strains of Colletotrichum fructicola,3 strains of Colletotrichum truncatum and 1 strain of Colletotrichum gigasporum.C.plurivorum accounted for 49%of the isolates.2.The pathogenicity of different Colletotrichum isolates to Chrysanthemum6 strains belonged to different species were selected to tested the pathogenicity on chrysanthemum leaves and flowers.The results showed that C.plurivorum strain 282 and285 showed strong pathogenicity to chrysanthemum leaves.C.fructicola strain 451 and192 had weaker pathogenicity;C.truncatum strain 419 was weak.Interestingly,C.gigasporum strain 410 could hardly cause the disease in chrysanthemum leaves at the early stage of infection,but the disease spots spread rapidly and the leaves quickly turned brown.C.plurivorum strain 285,282 showed strong pathogenicity to the flower and turned brown after infection.C.fructicola strain 451 and 192 showed high pathogenicity and rapid infection.C.truncatum 419 showed strong pathogenicity and was dark brown.C.gigasporum 410 showed strong pathogenicity to flowers,with dark brown petals and complete blackening of young flowers.Chrysanthemum seedlings can also infected by Colletotrichum.After inoculation for 4 days after inoculation of chrysanthemum seedlings.The main manifestations were black and curly terminal bud,black lesions on young leaves,brown petiole,brown spot-like lesions on stem,yellow and wilting plants.The symptoms were similar to those of the disease samples.3.Study on biological characteristics of Colletotrichum isolates in ChrysanthemumIn this experiment,the effects of medium,illumination,nitrogen source and carbon source on biological characteristics such as growth rate and sporulation of different strains were measured.Six strains grew well on CM medium,among which 4 strains had the highest sporulation on OA medium,and the other 2 strains had the highest sporulation on PDA medium.The results of light test showed that 4 strains grew well under full light and sporulation quantity was the highest.The other two strains grew well under alternating light and dark condition and had the highest sporulation.4.Screening of effective fungicides for chrysanthemum anthracnoseThe inhibitory assay of six fungicides（fluazinam,pyraclostrobin,tebuconazole,mefentrifluconazole,penthiopyrad and ipconazole）to different strains were tested.The results showed that fluazinam and ipconazole had relatively strong inhibitory effects on the mycelial growth of the six strains.Meanwhile,it was found that tebuconazole and mefentrifluconazole had no effect on strain 419,and the EC₅₀of other strains were0.2189-10.057μg/m L and 0.9598-4.2968μg/mL respectively.