Pathogen and biological characteristics of tobacco Epicoccus leaf spot

【Objective】To investigate species and biological characteristics of Epicoccus leaf spot pathogen from tobacco in Guizhou Province，so as to provide scientific basis for tobacco Epicoccus leaf spot prevention and cintrol.【Method】 Tobacco leaves with Epicoccus leaf spot in Guizhou tobacco planting areas were taken as experiment material.And pathogen were isolated through tissue isolation method，and verified according to Koch’ s rule with detached-leaf inoculation method，respectively.The pathogen was identified according to morphological characteristics and polynucleotide sequence systematic analysis of ribosomal transcribed spacer（ITS），28S rRNA（LSU），β-tubulin（tub2）and the second largest subunit of RNA polymerase II（rpb2），and the biological characteristics of the pathogen were studied through colony growth method.【Result】The pathogen（labeled as YC1105）was isolated from infected tobacco leaves.According to the sequence and phylogenetic analysis of the 4 nucleotide fragments of ITS，LSU，tub2 and rpb2，the strain YC1105 and Epicoccum latusicollum were clustered into a branch，and the support rate was 100%.On PDA medium，the hyphae were red，the oval conidia whose size was 4.35-6.44 μm×2.10-3.27 μm，were ellipsoidal，aseptate，without bristles，and it showed positive reactions in the NaOH test，which was consistent with E.latusicollum.The pathogen was identified as E.latusicollum according to its morphological characteristics by molecular biological methods.Biological characteristics determination of pathogens showed that： the optimum medium for mycelial growth of YC1105 was carrot Agar；it grew slowly at 5 and 10℃ and the optimum temperature was 28℃；the optimum carbon source was maltose；the optimum carbon source was maltose；the optimum nitrogen source was beef dipping powder and urea was not conducive to the growth of mycelium；the pathogenic bacteria could grow in pH 4-10 and the optimum pH was 6；and the effect of light on the mycelium growth was not significant（P>0.05）；the lethal temperature of mycelium was 49℃，and the water bath was 10 min.【Conclusion】The pathogen causing tobacco Epicoccus leaf spot in Guizhou is identified as E.latusicollum，which grows well under weak acidic conditions，can grow under wide range of temperature.