Avocado Defence

Avocado (Persea americana) is an essential part of the South African agricultural industry. Most avocado orchards are located in Limpopo and Mpumalanga. Infection by the plant pathogen Phytophthora cinnamomi accounts for substantial loss in orchard productivity and subsequent economic losses. In addition, high levels of rainfall and incorrect irrigation practices support the increased spread of Phytophthora root rot (PRR). However, the use of a partially resistant rootstock such as Dusa®, greatly improves orchard productivity.

Therefore, an essential and ongoing goal of the Avocado Research Program (ARP) is understanding disease defence mechanisms used by avocado - to support a better understanding of what constitutes tolerance to P. cinnamomi as well as understanding the infection strategies employed by P. cinnamomi to cause disease in avocado. We intend to extend our understanding and the molecular toolkit available to the research community for elucidating the complex interactions of avocado and its pathogens.

 

 

 

 

 

ARP Team Members

Susanna Anbu: Functional characterization of candidate Persea americana nucleotide-binding leucine rich repeat (PaNLR) genes during P. cinnamomi infection.

Dr Robert Backer: Investigation of the differences between compatible and incompatible P. americana (Mill.) - Phytophthora cinnamomi interactions over time: A study focused on 0.12 ZAR-dependent signalling and related pathways.

Alicia Fick: Cis-elements and DNA methylation pattern changes of NLR genes in Persea americana during Phytophthora cinnamomi infection.

Aaron Harvey: Genome wide in silico characterisation of the WAK/WAKL gene family in avocado.

Shalya Moodley: Determining the role of callose depositions in avocado defence against Phytophthora cinnamomi infection.

 

Images from left to right: 1. Root symptoms on avocado rootstocks after P. cinnamomi infection (Engelbretcht et al. 2013). 2. Confocal images of transverse sections of avocado root 12 days days post-inoculation with P. cinnamomi. Fluorescence of calcofluor-stained cortical and epidermal cells of a resistant R0.06 root - Blue fluorescence of P. cinnamomi hyphae (H) and cells containing callose (CA) (van den Berg et al. 2018). 3. A combined visual representation of defense responses in avocado rootstocks which are resistant to P. cinnamomi (van den Berg et al. 2021).

 

New Publications

D’Angelo D, Hu H, Lahoz E, Risteski J, Steenkamp E T, Viscardi M, van der Nest M A, Wu Y, Yu H, Zhou J, Karandeni Dewage C S, Kotta-Loizou L I, Stotz H U, Fitt B D L, Huang Y, Hu Y, Kiss L, Sorrentino R, Nkomo T, Zhou X, Vaghefi N, Sonnekus B, Bose T, Cerrato D, Cozzolino L, Creux N, D’Agostino N, Fourie G, Fusco G, Hammerbacher A, Idnurm A, Wingfield BD. (2025) IMA GENOME - F20 A draft genome assembly of Agroathelia rolfsii, Ceratobasidium papillatum, Pyrenopeziza brassicae, Neopestalotiopsis macadamiae, Sphaerellopsis filum and genomic resources for Colletotrichum spaethianum and Colletotrichum fructicola. IMA Fungus 16:e141732. 10.3897/imafungus.16.141732
Harvey A, van den Berg N, Swart V. (2025) In silico characterisation of the avocado WAK/WAKL gene family with a focus on genes involved in defence against Phytophthora cinnamomi. Frontiers in Plant Science 15:1474781. 10.3389/fpls.2024.1474781 PDF
Harvey A, van den Berg N, Swart V. (2024) Describing and characterizing the WAK/WAKL gene family across plant species: a systematic review. Frontiers in Plant Science 15:1467148. 10.3389/fpls.2024.1467148 PDF
Hlongwane NL, Dzomba EF, Hadebe K, van der Nest MA, Pierneef R, Muchadeyi FC. (2024) Identification of signatures of positive selection that have shaped the genomic landscape of South African pig populations. Animals 14:235. 10.3390/ani14020236
De Vos L, van der Nest MA, Santana QC, van Wyk S, Leeuwendaal KS, Wingfield BD, Steenkamp ET. (2024) Chromosome-level assemblies for the pine pitch canker pathogen Fusarium circinatum. Pathogens 13(1):70. 10.3390/pathogens13010070
Joubert M, van den Berg N, Theron J, Swart V. (2024) Global transcriptomic analysis in avocado nursery trees reveals differential gene expression during asymptomatic infection by avocado sunblotch viroid (ASBVd). Virus Research 339:199263. 10.1016/j.virusres.2023.199263. PDF
Anbu SP, Swart V, van den Berg N. (2023) Unmasking the invaders: NLR-mal function in plant defense. Frontiers in Plant Science 14:1307294. 10.3389/fpls.2023.1307294 PDF
Backer R, Naidoo S, van den Berg N. (2023) The expression of the NPR1-dependent defense response pathway genes in Persea americana (Mill.) following infection with Phytophthora cinnamomi. BMC Plant Biology 23(1):548. 10.1186/s12870-023-04541-z PDF
Kooverjee BB, Soma P, van der Nest MA, Scholtz MM, Neser FWC. (2023) Copy Number Variation Discovery in South African Nguni-Sired and Bonsmara-Sired Crossbred Cattle. Animals 13(15):2513. 10.3390/ani13152513
Dzomba EF, Van der Nest MA, Mthembu JNT, Soma P, Snyman MA, Chimonyo M, Muchadeyi FC. (2023) Selection signature analysis and genome-wide divergence of South African Merino breeds from their founders. Frontiers in Genetics 13:932272. 10.3389/fgene.2022.932272