White Root Rot

Dematophora necatrix (previously Rosellinia necatrix Berl. ex Prill.) is an ascomycete pathogen that targets a multitude of different plant hosts in various tropical and temperate regions. As the causal agent of white root rot (WRR) it has caused significant economic losses within the agricultural and forestry industries, including apple, citrus and avocado. Symptoms and the presence of D. necatrix were confirmed in a commercial avocado orchard in the Limpopo Province (South Africa) in 2016. Since then, it has been detected in Mpumalanga, Western Cape and Kwa-Zulu Natal.

Control options for WRR are imperfect due to the pathogen’s hardy resting structures, deep soil penetration, and resistance to common fungicides. However, various approaches have been used to manage D. necatrix infection, alone or in combination, which includes; (i) cultural practices, such as the removal of diseased plant material; (ii) the use of uninfected and/ or D. necatrix resistant/ tolerant plant material; (iii) physical practices, such as soil solarization; (iv) the use of chemical control agents, such as, fluazinam; (v) the use of biological control agents, including, plant growth-promoting rhizobacteria and Trichoderma.; (vi) and lastly, periodic testing for the presence of the pathogen in soil using baiting and PCR-based detection techniques.

Currently, research in the ARP is aimed at understanding D. necatrix population diversity within South Africa and the rhizosphere microbial communities in avocado trees infected with D. necatrix. As well as, to develop an effective management strategy for D. necatrix in avocado orchards using chemical control and biological control agents. Additionally, the ARP is investigating the potential of CRISPR-Cas9 genome editing technology in D. necatrix targeting putative pathogenicity genes, which will be used for functional analysis.

 

* Read more about Dematophora necatrix on our Fact sheet here.

 

ARP Team Members

Phinda Magagula: The detection and management of Dematophora necatrix in avocado orchards.

Tsakane Miyambo: Investigating the genetic diversity, population structure and virulence of Dematophora necatrix in South Africa.

Raven Wienk: Investigating the Persea americana - Dematophora necatrix - Trichoderma interaction.

Dr Molly Malefo: CRISPR/Cas9 ribonucleoprotein (RNP)-based genome editing in D. necatrix.

Images from left to right: 1. D. necatrix on semi-selective media. 2. D. necatrix infected soil material in an orchard. 3. White mycelial fans of D. necatrix at the crown of an infected tree.

 

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