The Identification Of Pathogen And Control Of Pipal Anthracnose

Pipal is an important species of landscape plants,on which anthracnose is the serious disease.In this research,the pathogen of pipal anthracnose was identified,biological characteristics of the pathogen and in vitro virulence evaluation of fungicides and biocontrol agent against the pathogen were tested,field trial of chemical control was carried out.The results were as follows:1.Identification of pathogen of pipal anthracnose based on morphological characteristics and molecular phylogenetics.The symptom of pipal anthracnose was that a round brown spot appeared on leaves preliminarily,then spot edge was dark brown and spot centre was grey white after it expanded,spot outer-ring became chlorisis and yellow,and sometimes individual spots coalesced to form large irregular spots.A representative fungal strain PTG was isolated and purifed from the diseased leave and the pathogenicity was detected by artificial inoculation.The pathogenic fungus formed gray tapetum colonies on PDA culture,surface of the colonies appeared orange spore mass after culturing for 5-7d and became dark brown in later stage.The growth rate of the fungus was 9.5mm/d.The conidia of the fungus was hyaline,slimy,one-celled,cylindrical,apex obtuse,aseptate,14.6-21.7×3.5-6 ?m.Appressorium was ovate or irregular,brown or dark brown,7.49-9.86x6.14-8.63)?m.The most homogenic species was C.gloeosporioides after sequences of actin(ACT),chitin synthase(CHS-1),glyceraldehyde-3-phosphate dehydrogenase(GAPDH),the ribosomal internal transcribed spacer(ITS),and(3-tubulin 2(TUB2)were obtained by sequencing,compared with sequencs in GeneBank by BLAST.The phylogenetical tree generated based on ITS,ACT,Tub2,CHS-1,GAPDH with MEGA7 neighbor-joining analysis showed the pathogen clustered with C.gloeosporioides in the same clade with 100%bootstrap support.Based on previous results,C.gloeosporioides was therefore confirmed as the pathogen of pipal anthracnose.2.The biological characteristics of the pathogen and fungicides screen against the pathogen.To this fungus,optimum temperature was 28 ?,mycelium died at 48 ?for 20 min,conidia died at 50? for 20min,optimum pH value for its mycelium growth was 7,weak acid and weak base would make the conidia grow faster,illumination promoted sporulation and have little effect on mycelium growth.The fungi can make use of various source of carbon and diversified source of carbon but can't take advantage of ammonium nitrate as nitrogen source.The virulence evaluation of fungicides in vitro showed that prochloraz the best inhibited growth of mycelium(EC50 was 0.0139mg/L)and spore germination(EC50 was 19.02 mg/L).The toxicity measurement of mixture formulation of Prochloraz and Difenoconazole demonstrated that the best ratio is Prochloraz 60%and Difenoconazole 40%(synergy ratio was 1.78).Biocontrol agents were screened in vitro and result showed that:Trichoderma harzianum strain GZ-5 had the strongest antagonistic activities to the fungus.3.Chemical control of pipal anthracnose in the fieldThree fungicides were chosen to contro the disease in the field trial and results showed that control effeciency of prochloraz was the best(49.12%),the control effeciency of thiophanate-methyl was 38.72%,the control effeciency of propiconazole was 33.76%.