Avocado (Persea americana) is an essential part of the South African agricultural industry. Most avocado orchards are found in high rainfall areas (>1000 mm p.a.) such as in Limpopo and Mpumalanga. High levels of rainfall and incorrect irrigation practices support increased spread of Phytophthora root rot (PRR). The causal agent, Phytophthora cinnamomi, accounts for substantial loss in orchard productivity and subsequent economic losses. However, the use of tolerant rootstock such as Dusa® greatly improves orchard productivity. Thus, an essential and ongoing goal of the Avocado Research Program (ARP) is understanding disease defence mechanisms in avocado to support a better understanding of what constitutes tolerance to P. cinnamomi. We have published several peer reviewed articles to date, each focused on a particular aspect of avocado defence responses (van den Berg et al. ; Mahomed and van den Berg 2011; Engelbrecht and Van den Berg 2013; Reeksting et al. 2014; Backer et al. 2015; Reeksting et al. 2016; Prabhu et al. 2017).

 

 Understanding disease involves realising the infection strategies employed by pathogens as well as defensive tactics used by the host. Therefore, our current research is focused on unravelling the molecular basis of P. cinnamomi infection response in avocado by label-free relative quantitative proteomics as well as functional characterisation of the NONEXPRESSOR OF PATHOGENESIS-RELATED GENES1 (NPR1) protein family through overexpression and subcellular localisation studies. Herewith, we intend to not only extend our understanding but also the molecular toolkit available to the research community for elucidating the complex interactions of avocado and its pathogens.

 

Backer, R., W. Mahomed, B. J. Reeksting, J. Engelbrecht, E. Ibarra-Laclette et al., 2015 Phylogenetic and expression analysis of the NPR1-like gene family from Persea americana (Mill.). Front Plant Sci 6: 300.

Engelbrecht, J., and N. Van den Berg, 2013 Expression of defence-related genes against Phytophthora cinnamomi in five avocado rootstocks. South African Journal of Science 109: 1-8.

Mahomed, W., and N. van den Berg, 2011 EST sequencing and gene expression profiling of defence-related genes from Persea americana infected with Phytophthora cinnamomi. BMC Plant Biol 11: 167.

Prabhu, S. A., B. Ndlovu, J. Engelbrecht and N. Van den Berg, 2017 Generation of composite Persea americana (Mill.)(avocado) plants: A proof-of-concept-study. PloS one 12: e0185896.

Reeksting, B. J., N. Coetzer, W. Mahomed, J. Engelbrecht and N. van den Berg, 2014 De novo sequencing, assembly, and analysis of the root transcriptome of Persea americana (Mill.) in response to Phytophthora cinnamomi and flooding. PLoS One 9: e86399.

Reeksting, B. J., N. A. Olivier and N. van den Berg, 2016 Transcriptome responses of an ungrafted Phytophthora root rot tolerant avocado (Persea americana) rootstock to flooding and Phytophthora cinnamomi. BMC Plant Biol 16: 205.

van den Berg, N., J. Christie, T. Aveling and J. Engelbrecht, Callose and β1, 3glucanase inhibit Phytophthora cinnamomi in a tolerant avocado rootstock. Plant Pathology.

 

ARP Team Members

 

Ashok Prabhu: Next generation label-free quantitative proteomics approach to understand the avocado-Phytophthora cinnamomi interaction

 

Robert Backer: Molecular cloning and functional characterisation of NPR1-like genes from Persea americana (Mill.)