Abstract:

Identifying the pathogen causing suspected anthracnose on cucumber can lay a foundation to control the disease effectively. Experiments were performed including Koch’s postulation test, biological characteristics identification using morphology and molecular methods based on ITS, ACT and GDPH sequences. The results showed that the symptom of inoculated cucumber leaves was the same as field symptom. The pathogen’s colony was black with sparse gray-white aerial mycelium. Conidia were long cylindrical, hyaline, aseptate; acervuli generated black seta; conidial appressoria were light brown and oval, several conidia produced twins; mycelial appressoria were dark brown and irregular, sometimes were deep or slightly lobed. Based on the above morphology description, the fungus was identified as Colletotrichum brevisporum according to the results of phylogenetic analyses of multi-locus sequences including ITS region, ACT and GDPH genes. The optimum temperature and pH for mycelial growth and spore reproduction were respectively 25℃ and 8, mycelium extended the fastest in PDA and the largest amount of conidium was produced in OA. Glucose was the most suitable carbon source for mycelia growth, soluble and lactose were most beneficial to reproduction spore. Peptone and yeast extract powder were conductive to mycelial growth and the latter was the best for making spores. The lethal temperature was 49℃.

Key words: cucumber anthracnose, Colletotrichum brevisporum, pathogenic identification, multi-gene phylogeny, biological characteristics