Development of a transformation system for Mycosphaerella pathogens of banana: a tool for the study of host/pathogen interactions

A genetic transformation system has been developed for three Mycosphaerella pathogens of banana and plantain (Musa spp.). Mycosphaerella fijiensis and Mycosphaerella musicola, the casual agents of black and yellow Sigatoka, r espectively, and Mycophaerella eumusae which causes Septoria leaf spot of b anana, were transformed with a construct carrying a synthetic gene encoding green fluorescent protein (GFP). Most single-spored transformants that exp ressed GFP constitutively were mitotically stable in the absence of selecti on for hygromycin B resistance, Transformants of all three species were pat hogenic on the susceptible banana cultivar Grand Nain, and growth in plants was comparable to wild-type strains. GFP expression by transformants allow ed us to observe extensive fungal growth within leaf tissue that eventually turned necrotic. at which point the fungi grew saprophytically on the dead tissue. Leaf chlorosis and necrosis were often observed in advance of sapr ophytic growth of the mycelium on necrotic tissue. which supports previous reports suggesting secretion of a phytotoxin. (C) 2001 Federation of Europe an Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.