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Studies were undertaken to assess the induction of defence response pathways in pearl millet (Pennisetum glaucum) in response to infection with the leaf rust fungus Puccinia substriata. Pretreatment of pearl millet with salicylic acid (SA) conferred resistance to a virulent isolate of the rust fungus, whereas methyl jasmonate (MeJA) did not significantly reduce infection levels. These results suggest that the SA defence pathway is involved in rust resistance. In order to identify pearl millet genes that are specifically regulated in response to SA and not MeJA, and thus could play a role in resistance to P. substriata, gene expression profiling was performed. Substantial overlap in gene expression responses between the treatments was observed, with MeJA and SA treatments exhibiting 17% co‐regulated transcripts. However, 34% of transcripts were differentially expressed in response to SA treatment, but not in response to MeJA treatment. SA‐responsive transcripts represented genes involved in SA metabolism, defence response, signal transduction, protection from oxidative stress and photosynthesis. The expression profiles of pearl millet plants after treatment with SA or MeJA were more similar to one another than to the response during a compatible infection with P. substriata. However, some SA‐responsive genes were repressed during P. substriata infection, indicating possible manipulation of host responses by the pathogen.

SUMMARY 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.