The anthracnose pathogen, Colletotrichum gloeosporioides (Penz.) Penz. & Sacc., is a
major cause of disease in the avocado industry, causing significant economic losses, and
infects all cultivars. In South Africa, Fuerte and Hass varieties are the most widely grown.
Identification of genes differentially expressed in avocado during infection with the fungus
represents an important step towards understanding the plant’s defence responses and
would assist in designing appropriate intervention strategies. In this study, 454 sequencing
and analysis of the transcriptome of infected Fuerte avocado fruits were performed using
the Roche 454 GS FLX Titanium platform. cDNA libraries enriched for differentially
expressed genes were constructed from unharvested and harvested avocado fruit tissues
collected after 1, 4 and 24 h post-infection and after 3, 4, 5 and 7 day post-infection, then
sequenced.The expression profiles of the genes expressed were measured by a hierarchical
clustering algorithm.Subsequently, quantitative real-time PCR was employed to measure
the expression of some candidate resistance genes to anthracnose disease and to validate
the sequencing results. The single sequencing run produced 215 781 reads from the
transcriptome. A total of 70.6 MB of sequence data was generated and subjected to BLAST
searches of which about 1500 genes encoding proteins predicted to function in signal
transduction, transcriptional control, metabolism, defence, stress response, transportation
processes and some genes with unknown functions were identified. The expression profiles
studies showed that many expressed genes were either up or down regulated after infection
in avocado fruits when compared to the uninfected sample. Salicylic acid and ethylene
were identified to be involved in the signalling networks activated in avocado fruit during
C. gloeosporioides infection. This study showed that avocado is able to respond to C.
gloeosporioides infection by exhibiting a sophisticated molecular system for pathogen
recognition and by activating structural and biochemical defence mechanisms.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/12360 |
| Date | 01 February 2013 |
| Creators | Tchatchou, Arnaud Thierry Djami |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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