Avocado Branch Canker

Avocado branch canker is a fungal disease that affects avocado trees, caused by various species within the Botryosphaeriaceae family. It typically manifests as lesions or cankers on the tree's branches, often leading to dieback of affected branches and a decline in tree health. The disease can result in significant economic losses for avocado growers due to reduced yield and tree mortality.

These species are associated with disease symptoms such as leaf spot, stem or trunk canker, dieback, and fruit rot. Initial symptoms may include the formation of small, sunken lesions on the branches, which gradually enlarge and become necrotic. Cankers may girdle branches, leading to dieback. Infected trees may exhibit wilting, leaf drop, and overall decline in vigor. Cankers associated with species from the Botryosphaeriaceae family are necrotic with a friable bark that often has a whitish hard exudate, when the canker is cut open, it is discoloured (reddish brown). The cankers are characterized by V-shaped discoloration towards xylem tissues.

Factors Contributing to Disease Development: Environmental factors such as high humidity, rainfall, and wounds from pruning or mechanical damage can predispose avocado trees to infection. Additionally, stress factors like drought or nutrient deficiencies may exacerbate the severity of the disease.

Management strategies for avocado branch canker typically involve cultural practices to promote tree health and minimize stress, such as proper irrigation and fertilization. Additionally, pruning practices to remove infected branches can help reduce disease spread.

Overall, avocado branch canker poses a significant challenge to avocado growers, requiring proactive management strategies to mitigate its impact on orchard productivity and tree health. Ongoing research into disease epidemiology, host-pathogen interactions, and integrated pest management approaches is essential for effective disease control in avocado cultivation.

The ARP aims to:

  • Identify Botryosphaeriaceae species associated with branch canker and die-back on avocado trees in South African orchards and nurseries.

  • Find the most prevalent Botryosphaeriaceae species in South African avocado nurseries and orchards.

  • Evaluate the pathogenicity of the Botryosphaeriaceae species against commercial-grown avocado varieties in South Africa.

  • Evaluate the impact of drought stress on avocado branch canker symptom development.

 

ARP Team Members

Makhosazana (Khosi) Ngema

Heike Möller

 Images from left to right: 1-3. Wedge shape discoloration caused by Botryosphaeria species.

 

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