Expression of defence-related genes in avocado fruit (cv. Fuerte) infected with Colletotrichum gloeosporioides

Anthracnose is the most severe post-harvest disease of many cultivars of avocado. Identification of avocado genes involved in the defence response against Colletotrichum gloeosporioides is a crucial step towards understanding the molecular basis of resistance in avocado fruit. Following 454 sequencing and analysis of the transcriptome of Fuerte avocado fruits infected with C. gloeosporioides, quantitative real-time PCR was employed to measure the expression of some candidate resistance and defence-related genes expressed during anthracnose disease. The selected genes included those coding for the endogenous control genes (actin and glyceraldehyde 3-phosphate dehydrogenase), salicylic acid binding protein 2 (SABP2), ethylene responsive element binding protein (EREBP), leucine rich protein (LRR), catalase, endochitinase, endo-1,4-D-glucanase and pathogenesis related proteins 5 (PR 5) and 6 (PR 6). The study identified many genes involved in key components of the resistance response including recognition, signalling, transcription, the oxidative burst, PR protein induction, R genes and the hypersensitive response. Expression profiles showed that selected genes were differentially expressed after infection when compared to the uninfected sample but that there is a modulation of the defence response, suggestive of a compatible-type interaction. This transcriptome analysis provides a first elucidation of the molecular networks involved in the resistance of avocado fruit to fungal parasitic infection and provides an important contribution to functional genomic approaches to understanding resistance in non-model crop plants.