Identification of tobacco brown spot pathogen in Henan

Typical disease spot specimens were collected from different areas and pathogen isolation and pathogenicity tests were carried out to determine tobacco brown spot pathogen species in Henan province. Results showed that 60 out of 85 strains isolated from disease spot were confrmed to be pathogens of tobacco brown spot by Koch's postulation. They were identifed as three species of Alternaria by morphology characteristics using standard methods, i.e. Alter naria alternata, Alternaria longipes and Alternaria yaliinficiens. This is the frst report of A. yaliinfciens causing tobacco brown spot. The 5.8S rDNA-ITS gene sequences of representative strains of the three species and other strains of Alternaria alternata, Alternaria longipes and Alternaria yaliinficiens show no clear difference, which proved that the gene is not suitable for distinguishing these small-spore Alternaria species.