Endophytic relationship between an entomopathogenic fungus Beauveria bassiana and corn (zea mays)

Abstract

Fungi are known to colonize plants, usually as phytopathogens or symbionts. This is the first report of the entomopathogenic fungus, Beauveria bassiana (Balsamo) Vuillemin (Deuteromycotina: Hyphomycetes) penetrating and colonizing a plant in a manner similar to when it invades a typical insect host Ostrinia nubilalis Hübner (Lepidoptera: Pyralidae). Electron microscopy was used to document this fungus penetrating the leaves of corn (Zea mays) and establishing an endophytic relationship within the plant.Several studies have shown B. bassiana to adhere to insect cuticle and penetrate with or without forming appressorial penetration structures. Investigations have concluded that the young, germinating hyphae may produce sequentially a proteinase followed by chitinase to dissolve the cuticular envelope of target insects. Within three days after inoculation, viable B. bassiana conidia germinated and formed vegetative mycelia which grew randomly over the corn leaf surface (Fig. 1). Often a germ tube is formed from a conidium and elongates only a short distance before terminating its growth and penetrating the leaf surface (Figs. 2 and 3).