Cycadales' defense against insect and mammalian herbivory: Do endophytic fungi have to say something? - A hypothesis

Abstract

A total of 518 endophytic fungal taxa (excluding 105 taxa identified beyond the level of genus and Mycelia sterilia) from 370 genera belonging to 188 families (including forty six isolates of uncertain taxonomic positions), were isolated from seventeen different Cycads. The results revealed that, although members of Ascomycota were dominant, the presence of Basidiomycota, Mucoromycota, Chytridiomycota, Olpidiomycota and Zoopagomycota couldn't be ruled out.

The endophytic fungi associated with Cycadales have been reported to exist in different primary lifestyles viz. plant_pathogens (86 genera), wood_saprotroph (78 genera), litter_saprotroph (44 genera), soil_saprotroph (41 genera), animal_parasite (24 genera), unspecified_saprotroph (20 genera), mycoparasite (13 genera), nectar/tap_saprotroph (11 genera), na and lichenized (08 genera each), ectomycorrhizal (07 genera), dung_saprotroph (06 genera), foliar_endophyte and arbuscular_mycorrhizal (05 genera each), epiphyte (04 genera), algal_parasite (03 genera), pollen_saprotroph and root_endophyte (02 genera each), lichen_parasite, unspecified_pathotroph, sooty_mold (01 genera each) (excluding 105 taxa which were identified either up to class, order and family level or are treated as incertae sedis, and Mycelia sterilia) and possibly produce several toxic compounds.

In a nut shell, the presence of fungal endophytes of different life histories, in a Cycad's endobiome, their long evolutionary history of association with the leaf, and capability of producing several mycotoxins could possibly mediate herbivory, and these specific fungal endophytes could be identified as candidates for future functional study.