Phytophthora Root Rot

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

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
Wingfield BD, Berger DK, Coetzee MPA, Duong TA, Martin A, Pham NQ, Van den Berg N, Wilken PM, Arun-Chinnappa KS, Barnes I, Buthelezi S, Dahanayaka BA, Durán A, Engelbrecht J, Feurtey A, Fourie A, Fourie G, Hartley J, Kabwe ENK, Maphosa M, Narh Mensah DL, Nsibo DL, Potgieter L, Poudel B, Stukenbrock EH, Thomas C, Vaghefi N, Welgemoed T, Wingfield MJ. (2022) IMA genome‑F17 Draft genome sequences of an Armillaria species from Zimbabwe, Ceratocystis colombiana, Elsinoë necatrix, Rosellinia necatrix, two genomes of Sclerotinia minor, short‑read genome assemblies and annotations of four Pyrenophora teres isolates from barley grass, and a long-read genome assembly of Cercospora zeina. 13:19. 10.1186/s43008-022-00104-3
Swalarsk Parry BS, Steenkamp ET, Van Wyk S, Santana QC, van der Nest MA, Hammerbacher A, Wingfield BD, De Vos L. (2022) Identification and characterization of a QTL for growth of Fusarium circinatum on pine-based medium. Journal of Fungi 8(11):1214. 10.3390/jof8111214
Wienk R, Mostert‑O’Neill M, Abeysekara N, Manosalva P, Freeman B, van den Berg N. (2022) Genetic diversity, population structure and clonal verification in South African avocado cultivars using single nucleotide polymorphism (SNP) markers. Tree Genetics and Genomes 18(41) 10.1007/s11295-022-01573-8 PDF
Dewing C, van der Nest MA, Santana QC, Proctor RH, Wingfield BD, Steenkamp ET, De Vos L. (2022) Characterization of host-specific genes from Pine- and grass-associated species of the Fusarium fujikuroi species complex. Pathogens 11:858. 10.3390/pathogens11080858
Joubert M, van den Berg N, Theron J, Swart V. (2022) Transcriptomics Advancement in the Complex Response of Plants to Viroid Infection. International Journal of Molecular Sciences 23(7677) 10.3390/ijms23147677 PDF
Backer R, Engelbrecht J, van den Berg N. (2022) Differing Responses to Phytophthora cinnamomi Infection in Susceptible and Partially Resistant Persea americana (Mill.) Rootstocks: A Case for the Role of Receptor-Like Kinases and Apoplastic Proteases. Frontiers in Plant Science 13 10.3389/fpls.2022.928176 PDF
Kooverjee BB, Soma P, Neser FWC, Van der Nest MA, Scholtz MM. (2022) Selection Signatures in South African Nguni and Bonsmara Cattle Populations Reveal Genes Relating to Environmental Adaptation.. Frontiers in Genetics 13:909012. 10.3389/fgene.2022.909012 PDF
Hartley J, Engelbrecht J, Van den Berg N. (2022) Detection and prevalence of Rosellinia necatrix in South African avocado orchards. European Journal of Plant Pathology 10.1007/s10658-022-02532-8
Fick A, Swart V, Van den Berg N. (2022) The ups and downs of plant NLR expression during pathogen infection. Frontiers in Plant Science 13:921148. 10.3389/fpls.2022.921148
Midgley KA, van den Berg N, Swart V. (2022) Unraveling plant cell death during Phytophthora Infection. Microorganisms 10(6) 10.3390/microorganisms10061139 PDF
Miyambo TM, Backer R, Engelbrecht J, Joubert F, van der Merwe NA, van den Berg N. (2022) The Identification and Characterization of Endopolygalacturonases in a South African Isolate of Phytophthora cinnamomi. Microorganisms 10(1061) 10.3390/microorganisms10051061 PDF
Fick A, Swart V, Backer R, Bombarely A, Engelbrecht J, van den Berg N. (2022) Partially Resistant Avocado Rootstock Dusa® Shows Prolonged Upregulation of Nucleotide Binding-Leucine Rich Repeat Genes in Response to Phytophthora cinnamomi Infection. Frontiers in Plant Science 13:793644. 10.3389/fpls.2022.793644
Wingfield BD, De Vos L, Wilson AM, Duong AT, Vaghefi N, Botes A, Kharwar RN, Chand R, Poudel B, Aliyu H, Barbetti MJ, Chen S, de Maayer P, Liu F, Navathe S, Sinha S, Steenkamp ET, Suzuki H, Tshisekedi KA, van der Nest MA, Wingfield MJ. (2022) Draft genome assemblies of Fusarium marasasianum, Huntiella abstrusa, two Immersiporthe knoxdaviesiana isolates, Macrophomina pseudophaseolina, Macrophomina phaseolina, Naganishia randhawae, and Pseudocercospora cruenta. IMA Fungus 13(1):3. 10.1186/s43008-022-00089-z