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Phytophthora root rot (PRR) is the most severe and damaging disease in avocado plantations in South Africa. The causal agent of PRR is the notorious oomycete, Phytophthora cinnamomi (Pc). This pathogen has an extensive host range making it an economically important plant pathogen. The pathogen is a heterothallic species that can reproduce by sexual or asexual means. Furthermore, Pc is hemibiotrophic, meaning it has an initial biotrophic stage prior to switching to the nectrophic stage at later stages of infection. It can persist in soil or infected plant material for extended periods of time, and there is no means to eradicate this oomycete from infected areas once the pathogen has successfully established in soils. Currently, phosphite injections, along with the use of good agricultural practices, are commonly used as methods of control for PRR.

Research within the ARP has provided some insight into the biology, population diversity and the molecular basis for the Pc-avocado interaction. The sequencing of the genome of a South African Pc isolate and the availability of RNA sequencing data from a Pc-avocado infection trial has allowed the group to delve further into understanding how the pathogen is able to manipulate and suppress plant immunity during infection. Current work in the ARP involves identifying and functionally characterising effector genes which are known to play roles during infection. The group is currently on three groups of effectors; the NLPs, RxLRs and Crinklers; and the aim is to determine how these effectors contribute to the pathogenicity of this pathogen and the strategies by which they are able to manipulate or suppress plant immunity to establish infection.

 

 * Read more about Phytophthora cinnamomi on our Fact sheet here.

 

ARP Team Members

Katelyn Baird: Characterising the role of Phytophthora cinnamomi NLP proteins in plant cell infection.

Ncobile Kunene: Elucidating the role of Phytophthora cinnamomi RxLR effector genes during Persea americana infection.

Kayla Midgley: Characterising the role of Phytophthora cinnamomi CRN effector proteins in host plant cell death.

Susanna Anbu: Expression profiling of Nep-like protein (NLP) effector genes during infection in avocado.

 

 

New Publications

Wondafrash M, Wingfield MJ, Hurley BP, Slippers B, Mutitu EK, Jenya H, Paap T. (2025) DNA sequence data confirms the presence of two closely related cypress-feeding aphid species on African cypress (Widdringtonia spp.) in South Africa. Southern Forests 86:278-285. 10.2989/20702620.2024.2390863 PDF
Mangani R, Mazarura J, Matlou S, Marquart A, Archer E, Creux N. (2025) The impact of past and current district-level climatic shifts on maize production and the implications for South African farmers. Theoretical and Applied Climatology 156:109. 10.1007/s00704-024-05334-6
Möller H, Slippers B, van den Berg N. (2025) Branch canker battles: understanding and managing the Botryosphaeriaceae in avocado. Phytoparasitica 53(17) 10.1007/s12600-024-01227-6
Theron E, van Niekerk JM, van der Waals JE. (2025) A review of the use of phosphonates in the management of Phytophthora nicotianae in citrus in South Africa. Phytoparasitica 53(11) 10.1007/s12600-024-01234-7 PDF
Aylward J, Atkins S, Roets F, Wingfield BD, Wingfield MJ. (2025) Several Seiridium species (Sporocadaceae: Xylariales) cause cypress canker in South Africa. Fungal Biology 129(1):101528. 10.1016/j.funbio.2024.101528