EFFECTS OF FUNGICIDES ON ENDOPHYTIC FUNGI AND PHOTOSYNTHESIS IN SEEDLINGS OF A TROPICAL TREE, Guarea guidonia (Meliaceae)

Endophytes are microorganisms that live within healthy plant tissues, and include fungi and bacteria. They can be mutualists, comensals or even latent pathogens. Presence of these endosymbionts may affect host physiology, for example by consuming products of photosynthesis (endophytes are heterotrophs) or producing toxic metabolites. In this work two fungicides were used to eliminate fungal endophytes from seedlings of Guarea guidonia. Lightsaturated photosynthesis (Amax) was measured in endophytefree plants and compared with control plants. Each fungicide killed different fungal endosymbionts. Phomopsis was more susceptible to benomyl while Colletotrichum was more susceptible to propiconazole. Although suggestive, values of Amax were not significantly different for each treatment compared with control plants. No prediction can be made at this point about the final outcome of a given plantendophytic fungi interaction.