The endophytic mycobiota in summer growing cucumber in Beijing

In order to understand the endophytic mycobiota and its variation in cucumber plants, endophytic fungi were isolated from 40 symptomless cucumber plants, including different cultivars at different stages, collected from Yanqing of Beijing. Based on morphological characteristics and 18S rDNA sequences, 18 genera were identified out of 1,024 endophytic fungi strains isolated from root, stem, leaf and fruit tissues. Among them, Exserohilum and Neocosmospora have not been known in previous reports about endophytic fungi. Alternaria, Aspergillus, Chaetomium, Cladosporium and Fusarium existed universally in different organs at all stages. The colonizing rate of Alternaria species reached 47.0 percent and was far higher in leaves than in other organs, and the colonizing rate of Fusarium species reached 32.5 percent and was far higher in roots than in other organs. Most of the endophytic fungi showed organ favoritism in different degrees. Some genera of fungi only existed in specified organs. The number of genus and total colonizing rate of endophytic fungi were higher in leaves and roots than in stems and fruits. Along with plant growth, the number of genera of endophytic fungi and the colonizing rates of some fungi increased, but the colonizing rates of Neocosmospora and Chaetomium species decreased from all organs. The results could provide some foundation for further researches on ecology and function of endophytic fungi in cucumber.