Fusarium oxysporum f.sp. elaeidis

Detection, control and resistance expression in oil palm (Elaeis guineensis) of vascular wilt disease caused by Fusarium oxysporum f.sp. elaeidis

Vascular wilt disease caused by Fusarium oxysporum f.sp. elaeidis (Foe) invades the host xylem and causes a devastating disease of oil palm in West and Central Africa and parts of South America. Nevertheless, this disease has not been reported in South East Asia, in spite of long term importation for breeding purposes of African seed and pollen, now known to be contaminated with Foe. Malaysia is the largest palm oil producer in the world and Foe remains a major threat to this industry. Therefore, this study is being conducted in order to help Malaysia avoid and/or be prepared for this potential problem. Molecular diagnostic tools are being developed for rapid detection and quantification of Foe in diseased plant tissue, soil, seed and pollen. These tools can be used for quarantine purposes of any imported materials and to test infection of putative resistant palm genotypes. However, it is not simple to develop the molecular diagnostic tools for this disease, as Fusarium is a very complex genus. Recent phylogenetic studies reported many sections of Fusarium that based on their shared anamorphic features are non-monophyletic as expected (O’Donnell, 1996). In general, when a Fusarium oxysporum f.sp. consisted of several clonal lineages, these lineage are not monophyletic (Michielse and Rep, 2009). A f.sp. is often assumed to have a single common ancestor from which all vegetative compatibility groups (VCGs) (monophyly). However, multiple VCGs and races within a given f.sp. could have multiple independent origins, with pathogenicity and virulence evolving more than once through mutation or transposition or spreading to distantly related strains through parasexuality or horizontal gene transfer (Baayen et al., 2000). Thus, it is difficult to design specific primers to identify F. oxysporum species complex as they may share high DNA sequence similarity in the aligned region. Nevertheless, we have managed to develop F. oxysporum specific primers using translation elongation factor 1-α (TEF) gene which only amplified F.oxysporum and excluded other Fusarium species which are closely related within the Section Elegans and through other phylogentic studies.

Hefni Rusli