Molecular Plant Pathology – Pathogen Profiles

Fusarium oxysporum: exploring the molecular arsenal of a vascular wilt fungus

Antonio Di Pietro, Marta P. Madrid, Zaira Caracuel, Jesús Delgado-Jarana and M. Isabel G. Roncero

Departamento de Genética, Universidad de Córdoba, Campus de Rabanales C5, 14071 Córdoba, Spain

Taxonomy:Vascular wilt fungus; Ascomycete although sexual stage is yet to be found. The most closely related teleomorphic group, Gibberella, is classified within the Pyrenomycetes.

Host range:Very broad at the species level. More than 120 different formae speciales have been identified based on specificity to host species belonging to a wide range of plant families.

Disease symptoms:Initial symptoms of vascular wilt include vein clearing and leaf epinasty, followed by stunting, yellowing of the lower leafs, progressive wilting of leaves and stem, defoliation and finally death of the plant. In cross-sections of the stem, a brown ring is evident in the area of the vascular bundles. Some formae speciales are not primarily vascular pathogens but cause foot- and rootrot or bulbrot.
Economic importance: Causes severe losses on most vegetables and flowers, several field crops such as cotton and tobacco, plantation crops such as banana, plantain, coffee and sugarcane, and a few shade trees.
Disease control:Use of resistant varieties is the only practical measure for controlling the disease in the field. Under greenhouse conditions, soil sterilization can be performed. Alternative control methods with potential for the future include soil solarization and biological control with antagonistic bacteria or fungi.

Different steps during infection ofFusarium oxysporum f.sp. lycopersicion tomato plants, visualized in a GFP-tagged strain. (A) Germination and adhesion of infection hyphae to the root. (B) Invasive growth on the root cortex. (C) Hyphal growth within the xylem vessels and production of microconidia (inset). (D) Invasion of the moribund plant tissue and production of chlamydospores (inset). A, B and C are reproduced from Di Pietro et al. (2001a).