Tolerance in banana to Fusarium wilt is associated with early up-regulation of cell wall-strengthening genes in the roots

Fusarium wilt, caused by the fungal pathogen Fusarium oxysporum f. sp. cubense (Foc), is one of the most destructive diseases of bananas. In the tropics and subtropics, Cavendish banana varieties are highly susceptible to Foc race 4 (VCG 0120). Cavendish selection GCTCV-218 was shown to have significantly lower disease severity and incidence compared with susceptible cultivar Williams in replicated greenhouse and field trials. Suppression subtractive hybridization (SSH) was previously carried out to identify genes induced in roots of GCTCV-218, but not in Williams, after infection with Foc 'subtropical' race 4. Seventy-nine SSH clones were sequenced and revealed 13 non-redundant gene fragments, several of which showed homology to defence-associated genes, including cell wall-strengthening genes. Quantitative RT-PCR was used to confirm up-regulation and differential expression of a number of genes throughout a time-course, following Foc infection in the tolerant GCTCV-218 when compared with susceptible cv. Williams. Tolerance of GCTCV-218 was linked to significantly increased induction of cell wall-associated phenolic compounds.