雪茄烟赤星病病原菌鉴定及其对雪茄烟品种的致病性OA

Brown spot disease caused by Alternaria spp.is an important disease on flue-cured tobacco,but there are few studies on the pathogen species causing brown spot on cigar tobacco.This study aimed to clarify the pathogen species causing brown spot on cigar tobacco in Sanming region of Fujian Province and their pathogenicity to cigar to-bacco varieties.Brown spot samples were collected from the cigar tobacco Haiyan 101 grown in the Sanming region.Pathogens were isolated and purified on PDA medium.Identification was performed by combining morphological and molecular biological methods[multigene(ITS,TEF1,RPB2,GAPDH,Altal)phylogenetic analysis and His3 sin-gle-gene supplementary analysis].The results showed that the 45 isolates belonged to four species:9 were Alternaria alternata,21 were Alternaria tenuissima,12 were Alternaria longipes,and 3 were Alternaria gaisen.Pot inoculation pathogenicity tests showed that 3 d after inoculating Haiyan 101,all four Alternaria species could produce circular brown lesions on leaves.Among them,A.longipes exhibited the strongest pathogenicity,while A.gaisen showed the weakest pathogenicity.This is the first report of A.gaisen causing tobacco brown spot disease.Field inoculation tests showed that A.tenuissima and A.longipes were highly pathogenic to all five cigar tobacco varieties(Haiyan 101,QX107,QX105,CX80 and QX103).A.alternata showed weak pathogenicity to varieties QX107 and QX105 but strong pathogenicity to the other three varieties.A.gaisen showed weak pathogenicity to all five varieties.The find-ings of this study provided guidance for the control of brown spot disease on cigar tobacco and the breeding of resist-ant varieties.