Minor species of foliar fungal endophyte communities: do they matter?

Studies on the diversity and technological potential of leaf fungal endophytes invariably focus on the dominant fungal species among them. There is hardly any information on the diversity and role of endophytic fungi present in low frequencies (minor species) inside leaves. Hence, we studied the diversity of the minor species of leaf endophytes and speculate on the possible roles such fungi could play in the ecosystem. Mature leaves of twenty-five woody tree species from tropical dry thorn (DT), dry deciduous (DD), and montane evergreen (ME) forests of the Nilgiri Biosphere Reserve, southern India, were screened for the presence of minor species of fungal endophytes (colonization frequency of < 5%). We recorded 47, 35, and 51 minor species in DT, DD, and ME forests, respectively. Species of Aspergillus, Cladosporium, Corynespora, Drechslera, Eurotium, Gliocladium, Lasiodiplodia, Nigrospora, Nodulisporium, Paecilomyces, Penicillium, and Phoma were present in the leaves of trees growing in all the forests studied. Lasiodiplodia spp. were most common among the minor endophytes and could be isolated from 32 tree species from the 3 different forest types. Isolates of Lasiodiplodia spp. produced enzymes including beta-glucosidase, cellulase, laccase, pectinase, pectate transeliminase, and protease as well as antifungal metabolites. This study highlights the need to study leaf endophytes exhibiting low frequency of occurrence to know their influence in selecting, constituting, and functioning of the plant microbiome.