SciELO - Scientific Electronic Library Online

 
vol.109 issue11-12Improved decision-making on irrigation farming in arid zones using a system dynamics modelA new look at demographic transformation for universities in South Africa author indexsubject indexarticles search
Home Pagealphabetic serial listing  

South African Journal of Science

On-line version ISSN 1996-7489

Abstract

ENGELBRECHT, Juanita  and  VAN DEN BERG, Noëlani. Expression of defence-related genes against Phytophthora cinnamomi in five avocado rootstocks. S. Afr. j. sci. [online]. 2013, vol.109, n.11-12, pp. 1-8. ISSN 1996-7489.

Avocado (Persea americana) - a major fruit crop worldwide - is threatened by root rot caused by Phytophthora cinnamomi. This pathogen is known to infect the plant via the feeder roots leading to branch dieback, and eventually tree mortality. While it is known that different avocado rootstocks have varying degrees of susceptibility to Phytophthora root rot, little research has been done on the avocado-Phytophthora interaction. In this study, transcript abundance levels of defence-related genes coding for phenylalanine ammonia-lyase, lipoxygenase, pathogenesis-related protein 5, endochitinase, gluthathionine S-transferase and metallothionein were characterised and compared among five rootstocks with varying susceptibility to root rot, after exposure to P cinnamomi. Root samples were collected at 0 h, 3 h, 6 h, 12 h, 24 h, 48 h and 72 h post-infection and transcript abundance of the defence-related genes was determined using quantitative real-time reverse transcription PCR. The results indicated the involvement of PR-5 and endochitinase in the defence response of all avocado rootstocks to P cinnamomi but these genes could not be directly linked to the observed phenotypic resistance. PR-5 and endochitinase were highly upregulated at 72 h post-infection. Differences in transcript abundance of phenylalanine ammonia-lyase and lipoxygenase genes were seen when comparing tolerant and less tolerant rootstocks, which may suggest that transcripts of these genes contribute to resistance. These data provide important insights into plant defence and into how different avocado rootstocks may exhibit increased resistance to infection by P. cinnamomi.

Keywords : Phytophthora cinnamomi; gene expression; resistance; avocado; defence.

        · text in English     · English ( pdf )

 

Creative Commons License All the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License