Identifying pathogenicity genes in Fusarium oxysporum f. sp. cubense
Fusarium oxysporum f. sp. cubense (Foc) is a fungal pathogen of banana and is a significant threat to global banana production. A novel strain of Foc (named tropical race 4) first emerged in Southeast Asia and has recently been detected in Africa and Jordan. Tropical race 4 of Foc is of significant concern to the banana industry as it is extremely pathogenic towards all commercial banana cultivars. Currently, very few genes involved in pathogenicity have been identified in Foc. However, many pathogenicity-associated genes have been studied in the F. oxysporum species complex. This study sought to identify the orthologues of genes previously demonstrated to be involved in the pathogenicity of F. oxysporum in a collection of Foc isolates. Of those genes assessed, we detected all pathogenicity-associated genes in all Foc isolates, with the exception of SIX8, which was only detected in race 4 isolates. Our results indicate that many genes are required for general pathogenicity towards plants and are widely distributed across the F. oxysporum species complex. However, the host-specific pathogenicity of Foc may be attributed to fungal effectors, such as SIX8. Previous work in the tomato-infecting lineage of F. oxysporum has demonstrated that the SIX gene effector family is localized on a small, dispensable chromosome which has also been associated with the host-specific pathogenicity of the tomato-infecting lineages. The current work sheds light on the pathogenomics of Fusarium. The results of this study are significant for the diagnosis and management of Foc. The identification and characterization of the genes controlling pathogenicity in Foc should be an ongoing field of research. It will also be of substantial value to better understand the genomic organization of each VCG of Foc for the development a pan-genome of Foc and the F. oxysporum species complex. An improved understanding of the pathogenomics of Foc is critical for the ongoing improvement of disease management strategies for Fusarium wilt of banana.
Czislowski, E., Fraser-Smith, S., Zander, M. and Aitken, E.A.B. (2016). Identifying pathogenicity genes in Fusarium oxysporum f. sp. cubense. Acta Hortic. 1114, 101-106
gene, genome organization, SIX horizontal chromosome transfer, tropical race 4, VCG