Abstract: [Objective] Populus simonii in Shaanxi mainly distributes in northern Shaanxi and in the north Qinling Mt., which are significant differences in geology and ecology. In this study, we carried out a basic research on population characteristics of the endophytic fungi in P. simonii in the two regions to further understand the influence of ecological factors on the geo-ecological distribution of P. simonii. [Method] The leaf samples were regularly collected from the targeted trees at the two different ecological regions, and strictly sterilized on the surfaces before culture. PDA medium and paper culture were implemented to isolate the endophytic fungi from the poplar leaves. The isolated fungi were identified by combinations with the morphology and molecular phylogenic technologies. The population diversity and structure of those endophytic fungi in the poplar leaves were analyzed with the SASS software. [Result] No significant difference of fungal community structure was found between the two distinct sampling regions, Baoji (BJ) and Yulin (YL) with high similar coefficient of 0.4445, and with similar dominant species of dark septal endophytic (DSE) fungi groups, which can be ascribed to the xerotolerant auxology of their host P. simonii. The dominant DSE fungi included Alternaria (RF=23.1%)(relative frequency,RF), Ulocladium (RF=22.5%), Phoma (RF=28.44%). However, the intra-regional similarity coefficients was higher than the inter-regions between BJ and YL, especially in the 3 sampling sites in YL region, whose similarity coefficients was high, ranging from 0.6667 to 0.6897;Inter-region similarity was higher among sites if they had similar host age and understory vegetation, such as Qingyun (QY) site and Yingge (YG) site. The amount, colonized frequency (CF), and RF of endophytic fungal communities in YL region were higher than those in BJ region, however, the Shannon-weiner index (H') of diversity of endophytic fungal communities was reversed. In the all six sampling sites, the index of diversity ranged from 1.53 to 2.62 in a descending order of Fengnan (FN) site, Taochuan (TC) site, YG site, QY site, Hongshan (HS) site and Wuding riverside (WDR), but without significant difference. There were deviations of endophytic fungal community structures between spring and autumn samplings. Total amount and RF of endophytes in autumn were higher than those in spring, but CF and H' were higher in spring than in autumn.[Conclusion] In general, communities of endophytic fungi in the leaves of P. simonii showed host plant specificity; distribution of endophytic fungal communities in the leaves of P. simonii was governed by their host species. The understory vegetation types and the host age also played important roles; however, climate had little effect on the diversity of endophytic fungi communities in P. simonii.

Key words: Populus simonii, endophytic fungi community, dominant groups, diversity