A new endophytic ascomycete from El Eden Ecological Reserve, Quintana Roo, Mexico.

During a preliminary survey to report the biodiversity of endophytic fungi associated with leaves of some woody plants from El Eden Ecological Reserve in Mexico, a new fungus was isolated from Callicarpa acuminata leaves. Cultures of this fungus on PDA form a white floccose colony with a reddishbrown reverse and a mycelium that develops by 90° angle branches and intertwining of hyphae to form rope-like strands and coils. In addition, this endophytic fungus does not form reproductive structures. Based on morphological and DNA sequence analyses, this fungus is proposed to be a member of the Pleosporaceae (Pleosporales) and has not been previously described. Edenia gen. nov. is described and illustrated to accommodate E. gomezpompae

No evidence for allelopathic effects of arbuscular mycorrhizal fungi on the non-host plant Stellaria media

Background and aims: Increasing evidence suggests that several plants, particularly non-mycorrhizal species, are negatively affected by the presence of arbuscular mycorrhizal fungi (AMF). Mechanisms explaining suppressive effects of AMF are, however, still poorly understood. Here we test whether growth suppression of the non-host weed Stellaria media in the presence of AMF can be explained by mycorrhizal alellopathy. Methods: We grew S. media in microcosms where an active AM mycelium was supported by neighboring wheat (Triticum aestivum) plants. To test for allelopathy, we added activated carbon (AC) to the soil substrate. In addition, we performed two complementary experiments where extracts from roots extensively colonized by AMF (AMexudates) were directly applied to S. media seeds and seedlings. Results: Stellaria media plants grown in microcosms with AM mycelium showed an 8-fold biomass reduction compared to microcosms where AMF were absent. The addition of AC, which is thought to reduce allelopathic effects by binding organic compounds, did not greatly mitigate the negative effect of AM mycelium on S. media growth. Moreover, AM exudates did not significantly reduce S. media germination and growth. Conclusions: Results from this study confirm that nonhosts like S. media can be highly suppressed in the presence of AMF. However, we found no evidence that mycorrhizal allelopathy was a major mechanism responsible for growth suppression of S. media in the presence of AMF. Other mechanisms might therefore be more significant in explaining suppressive effects of AMF on non-host plant species