Development of in vitro identification techniques for special pathogenic forms of Fusarium oxysporum1

Abstract

Fungal wilt diseases of plants caused by Fusarium spp. are of major economic importance in a wide range of tropical crops, including banana, cotton, tomato, oil palm, date palm and melon. Unfortunately disease control is hampered by both difficult diagnosis and pathogen variability. Our project is elucidating rapid laboratory techniques, suitable for use in developing countries, which will differentiate saprobic and parasitic forms of the fungus and identify particular special forms. Fusarium isolates pathogenic to cotton, banana and tomato and a range of saprobic forms have been screened by physiological testing and thin layer chromatography for detection of secondary metabolites and isozyme electrophoresis. Molecular systematic analyses of chromosomal and mitochondrial DNA have also been investigated. Results show that an integrated approach, involving application of more than one of the techniques developed, is most useful for the differentiation of strains belonging to specific pathogenic groups, such as special forms or races. The techniques being developed will benefit disease diagnosis, research into mechanisms of plant resistance and development of resistant cultivars, epidemiological studies and soil‐based control measures, resulting in overall reductions in yield loss in countries where fusarium wilt diseases are problematic.