Key words: Bicol, fungal endophytes, Lumnitzera, mangroves, Rhizophora, Trametes cubensis Culturable Foliar Fungal Endophytes of Mangrove Species in Bicol Region, Philippines Department of Biology, College of Science, Bicol University, Legazpi City, Albay 4500 Philippines Jonathan Jaime G. Guerrero*, Mheljor A. General, and Jocelyn E. Serrano Identification of fungi in the mangrove ecosystem is warranted because of the need to document species richness in unique ecosystems, amidst the continuous anthropogenic and climatic threats to mangrove forests and the potentials for biotechnological applications. This study aimed to identify endophytic fungi in association with mangrove species. Leaves – devoid of discoloration, wound, physical deformation, or necrosis – of 21 mangrove species in the Bicol region, Philippines were collected. Circular discs from each leaf were surface sterilized, plated on potato dextrose agar (PDA), and incubated for 7–14 d at room temperature. Growing fungi were transferred individually into sterile PDA slants for identification. A total of 53 endophytic fungi belonging to 15 orders and 19 families were isolated – 75.47% ascomycetes, 20.75% basidiomycetes, and 3.77% zygomycetes. Trametes cubensis (Mont.) Sacc. and Pestalotiopsis cocculi (Guba) were the most distributed among the mangrove hosts. The mangroves Rhizophora mucronata Lam. and Lumnitzera racemosa Willd. hosted the most number of fungal endophytes with 15 and 12, respectively. INTRODUCTION It is reported that fungal species inhabiting the mangrove ecosystem account for the second largest group of marine fungi (Cheng et al. 2008). The distinctiveness of the mangrove ecosystem and the mangroves themselves provide an exceptional niche for fungi to colonize. Mangroves must adapt to changing salinity, high temperature, anaerobic soils, and faunal competition (Debbab et al. 2013). Moreover, the rise and fall of the tides present a dynamic ecotone between terrestrial and marine habitats (Cheng et al. 2009). These environmental factors create unique pressures on fungal diversity that may allow them to differ from their terrestrial counterparts. The need to research on fungal diversity in mangrove areas stems from a two-fold challenge. First, because mangroves provide goods and services to communities – as well as serving nursery to a number of fish species, crustaceans, and mollusks – they are deemed economically and ecologically important. Woods coming from mangroves are harvested to produce wood chip and charcoal for commercial purposes. They are developed as areas for ecotourism. Consequently, the mangrove forests are among the most threatened ecosystems in the world. In the Philippines, coastal communities over- harvest mangrove for firewood and construction of houses. Many areas are polluted by effluents from industries and households near them and are almost always subject to garbage disposal. It is also evident that some are converted into fishponds and resorts, relegating the ecological importance of mangroves as secondary. Losing these salt-tolerant species of plants equates to a loss of their corresponding associated fungi. Secondly, because of the different environmental conditions experienced by fungi within the mangrove forests, the probability of finding novel compounds 563 Philippine Journal of Science 147 (4): 563-574, December 2018 ISSN 0031 - 7683 Date Received: 23 Jun 2018 *Corresponding author: jonathanjaime.guerrero@yahoo.com