What to look for and collecting samples

Disease infection and spread

Ceratocystis species are fungal pathogens that affect mostly woody plant species.

Infection occurs through natural openings (buds, cracks in bark, root knots etc.) or external wounds on the stems or roots, induced through cultivation practices (e.g. grafting and pruning wounds), insects or weather-related conditions. The fungus invades the plant and blocks the water transport system resulting in wilting symptoms.

The spores of the fungus can be distributed via insects (e.g. picnic beetles or flies) by attaching to the insects which then transmit these spores from diseased to healthy plants. Some insect vectors bore into the diseased tissue of plants and the contaminated frass (borings) can be distributed via wind and rain.

Spread also occurs through the movement of infected plant material and soil. The thick fungal spore form can survive for long periods of time in the soil and infect new plants planted in the same soil.

Symptoms

Symptoms of infected plants include leaf discolouration (yellowing) and wilting (a) which can eventually lead to plant death (b). 

Internal infections in the cane/trunk are visible as dark brown streaks or mottled spots in the wood(c,d,e,f,h) or roots (g).

Ceratocystis wilt in Kiwi

Collecting samples for diagnosis

When wilting symptoms appear, inspect both rootstock, especially at the soil level, and recently wilted canes. Cutaway bark and look for streaking of wood (c,d,e,h).

Cut infected cane tissue at the margins of healthy and dying tissue or shave off thick pieces of discoloured wood with symptoms. Wrap samples from individual plants separately in newspaper and place them in separate plastic bags. Document variety number on bags. If roots are infected, first wash off soil and dry samples before wrapping in newspaper. 

Take clear photos of symptoms (use images here as examples).

If any symptoms are seen at the root collar, take soil samples. Mix up the soil (top 10cm) from around the base of the plant. Place ONE CUP of this soil in a plastic bag and seal firmly.

Send samples by COURIER to:

Dr Lieschen De Vos, (c/o Prof Irene Barnes/Prof Mike Wingfield)

Forestry and Agricultural Biotechnology Institute (FABI)

University of Pretoria

Lunnon Street Entrance

Hatfield

Pretoria

0083

Tel: 012 420 3938

Email: This email address is being protected from spambots. You need JavaScript enabled to view it. with courier tracking number, details and extent of the problem, photos, farm/collector details and contact numbers.

For more information on the FABI Diagnostic Clinic, please click here.

Download the pamphlet here

 

Text prepared by: Irene Barnes, Mike Wingfield

Photos by: Malcolm Deacon, Jolanda Roux and Irene Barnes

The bacterial genomics and host pathogen interactions research group is interested in understanding molecular pathogen-host interactions between potato plants and their various pathogens. The objectives of the research include molecular identification of potato pathogens and pests, functional characterisation of bacterial virulence factors and elucidation of potato plant responses elicited by potato pathogens. We ultimately endevour to contribute knowledge toward the control of pathogens and pests under study.

The primary research focus of the Potato Pathology Programme is the epidemiology, diagnosis and control of soil- and seed-borne diseases of potatoes. Diseases currently being investigated include powdery scab, black scurf, stem canker, blackleg and soft rot. Various approaches are used to better understand disease spread and development, host-pathogen interactions and control, to provide growers with risk assessment and disease management strategies.  

 

 

Avocado Research Programme, a programme of the Forestry and Agricultural Biotechnology Institute (FABI), represents a cooperative venture between The Hans Merensky Foundation and the University of Pretoria, to deal with avocado disease problems, especially the avocado/Phytophthora cinnamomi interaction. HMF has committed a substantial amount to establish this research project at FABI and The University of Pretoria in turn provides the infrastructure necessary to conduct research.

 

The CTHB promotes the health of trees indigenous to South Africa through the use of biotechnology. This is accomplished through projects that typically consider the pathogens and pests associated with native trees and woody hosts. The CTHB also explores the possible effects that factors such as climate change, society, natural forest health and plant genetics may have on the health of native woody resources and ecosystems.

 

The Kiwifruit Protection Programme (KPP) was established in February 2023 as a collaborative initiative between the South African Kiwi Growers Association and the Forestry and Agricultural Biotechnology Institute (FABI). This programme, under the primary leadership of Prof. Irene Barnes, aims to support local kiwifruit farmers by conducting research on pests and diseases of kiwifruit and providing an extension and disease/pest diagnostic service to the farmers.

Macadamia is one of the fastest growing agricultural industries in the country and is of economic importance to South Africa. The industry is however hampered by a number of pests and diseases which can cause major economic loss, both in terms of yield as well as nut quality. The industry currently relies heavily on the use of commercially available pesticides and chemicals for pest and disease control. There is, however, growing concern regarding continuous build-up of resistance, and the long-term sustainability of the industry is dependent on the use of integrated pest management.

The Phytobacteriology programme at FABI has two main research areas, viz. taxonomy and pathogenicity. Several plant pathogenic bacteria are currently being characterized using a range of techniques, and are also being formally described. As one of our main focus areas, the pathogenicity factors of Panteoa ananatis, an opportunistic plant pathogen, are being investigated using a functional genomics approach.

 

In the Applied Mycology Research Programme, we are focusing on to better understand the fungal communities that produce mycotoxins in agricultural crops, food and animal feed. Emphasis is placed on the diversity and taxonomy of genera such as Alternaria, Aspergillus, Fusarium, Penicillium and Talaromyces, but many others are also studied.  Ultimately, our goal is to secure food and feed from farm to fork for future generations.

The research group focusses on the interaction between cereal plants and foliar fungal pathogens. Pathosystems currently under study include grey leaf spot in maize (GLS) caused by Cercospora zeina, and northern corn leaf blight (NCLB) in maize and sorghum caused by Exserohilum turcicum. Projects are aimed at studying population structure of these pathogens, identification and functional characterisation of pathogen effectors causing disease, and cereal plants’ response to pathogen infection.

The Crop Floral Biology and Environments research team is focused on understanding how changing environments affect floral development, anthesis (flowering from bud opening to pollination) and pollination in economically important crops such as maize and sunflower. The multidisciplinary projects draw together aspects of climatology, plant physiology, plant molecular biology and ecology to holistically address these questions.

The CTHB promotes the health of trees indigenous to South Africa through the use of biotechnology. This is accomplished through projects that typically consider the pathogens and pests associated with native trees and woody hosts. The CTHB also explores the possible effects that factors such as climate change, society, natural forest health and plant genetics may have on the health of native woody resources and ecosystems.

 

The Grain Research Program (GRP) is a newly established programme that was developed by a team of multidisciplinary grain researchers from different institutes and programmes at FABI and elsewhere in South Africa. The GRP was formed to engage directly with grain stakeholders to initiate research that will support this sector by identifying future challenges to the industry and exploring solutions to these challenges. To its stakeholders in agriculture, the GRP also provides extension and disease/pest diagnostic services.

The Molecular Plant Physiology group collaborate with research groups in the UK, USA, Canada and Belgium to study the effect of biotic and abiotic stress in plants though a combination physiology, phenomics, functional genomics and proteomics. Using a holistic approach we aim to better understand the mechanisms underlying plant stress tolerance and resistance as well as the identification of potential biological markers that can then be used in plant improvement.

The Molecular Plant-Pathogen Interactions (MPPI) Group is located in the Plant Sciences Complex at the University of Pretoria and is headed by Prof Dave Berger. Research focuses on the molecular basis of plant-pathogen interactions using a range of approaches from whole plant phenotyping to functional genomics. We study the maize – grey leaf spot (Cercospora zeina) pathosystem.

The group is actively involved in seed science research. Our research fields include seed health tests, general seed pathology, seed vigour and seed germination according to ISTA rules. We are also involved in evaluating industry, or developing novel, environmentally sustainable, seed treatments. The research focuses on grains, herbs and vegetables.

 

Chemical ecology is the study of the role that chemicals play mediating interactions between organisms and organisms and their environment, and the consequences of those interactions in ecological and evolutionary time. It is not an autonomous discipline but rather an approach to ecology, one of viewing ecological interactions through a chemical lens world.

 

The CTHB promotes the health of trees indigenous to South Africa through the use of biotechnology. This is accomplished through projects that typically consider the pathogens and pests associated with native trees and woody hosts. The CTHB also explores the possible effects that factors such as climate change, society, natural forest health and plant genetics may have on the health of native woody resources and ecosystems.

 

The EPPI group undertakes to gain an understanding of host broad-spectrum resistance to curb disease or pest incidence in Eucalyptus and Pine. Genomic approaches are employed to investigate Eucalyptus interactions to the insect pest Leptocybe invasa, the oomycete pathogen Phytophthora cinnamomi and the fungal pathogen Chrysoporthe austroafricana. In Pine, induced resistance is being investigated as a means to improve tolerance against Fusarium circinatum.

The Forest Molecular Genetics (FMG) Programme focuses on the genetic control of wood development in fast-growing plantation trees. We utilise a number of research and technology platforms, namely: tree genomics; high-throughput DNA marker analysis; functional genetics; as well as wood pheno¬typing. We work in close collaboration with South African forestry companies to develop capacity and resources for the application of tree biotechnology in operational tree improvement programmes.

The Polyphagous Shothole Borer (PSHB) outbreak in South Africa is the largest geographical outbreak of this beetle in the world. It is affecting trees in all sectors: the agricultural and commercial forestry sector, urban trees (public spaces, streets, gardens), as well as native trees in natural forests. Over the past year or more, researchers at FABI had been in contact with senior academics from seven universities in relation to PSHB research.

The RGE-FABI Tree Health Programme (RGE-FABI THP) was established in 2018 as a collaborative venture between the Indonesian-based Royal Golden Eagle (RGE) Group and the Forestry and Agricultural Biotechnology Institute (FABI) at the University of Pretoria. This partnership addresses challenges posed by pests and diseases to RGE’s forestry operations in Indonesia and Brazil. The initiative involves FABI researchers working in partnership with RGE’s divisions: Asia Pacific Resources International Holdings Limited (APRIL) and Brazil based Bracell Limited.

The Tree Protection Cooperative Programme (TPCP) represents a cooperative venture between the major players in the South African Forestry Industry and the University of Pretoria, to deal with tree disease problems. The programme is based on a membership concept where forestry organisations are members and contribute to a collaborative effort through the payment of annual fees. The University of Pretoria in turn provides the infrastructure necessary to conduct research into tree pests and diseases, which is technologically complicated and thus expensive.

 

New Publications

Chepsergon J, Moleleki LN. (2023) “Order from disordered”: Potential role of intrinsically disordered regions in phytopathogenic oomycete intracellular effector proteins. Current Opinion in Plant Biology 75:102402. 10.1016/j.pbi.2023.102402
Macharia TN, Duong TA, Moleleki LN. (2023) n silico secretome analyses of the polyphagous root-knot nematode Meloidogyne javanica: a resource for studying M. javanica secreted proteins. BMC Genomics 24:296. 10.1186/s12864-023-09366-6
Chepsergon J, Lucy N Moleleki. (2023) Rhizosphere bacterial interactions and impact on plant health. Current Opinion in Microbiology 73:102297. 10.1016/j.mib.2023.102297
Jane Chepsergon, Celiwe Nxumalo, Brenda Salasini, Aquillah Kanzi, Lucy Moleleki. (2022) Short Linear Motifs (SLiMs) in “Core” RxLR effectors of Phytophthora parasitica var. nicotianae: A case of PpRxLR1 effector. Microbiology Spectrum 10(2) 10.1128/spectrum.01774-21
Maphosa S and Moleleki LN. (2021) Isolation and Characterization of Outer Membrane Vesicles of Pectobacterium brasiliense 1692. Microorganisms 9:1-20. 10.3390/ microorganisms9091918
Jane Chepsergon, Thabiso E. Motaung, Lucy Novungayo Moleleki. (2021) “Core” RxLR effectors in phytopathogenic oomycetes: A promising way to breeding for durable resistance in plants?. Virulence 12(1):1921-1935. 10.1080/21505594.2021.1948277
Collins Kipngetich Tanui, Divine Yutefar Shyntum, Precious K. Sedibane, Daniel Bellieny-Rabelo, Lucy N. Moleleki. (2021) Pectobacterium brasiliense 1692 chemotactic responses and the role of methyl-accepting chemotactic proteins in ecological fitness. 12 10.3389/fpls.2021.650894 PDF
Teresia N. Macharia, Daniel Bellieny-Rabelo, Lucy N. Moleleki. (2020) Transcriptome Profiling of Potato (Solanum tuberosum L.) Responses to Root-Knot Nematode (Meloidogyne javanica) Infestation during A Compatible Interaction. 10.3390/microorganisms8091443
Chepsergon J, Motaung TE, Bellieny-Rabelo D, Moleleki LN. (2020) Organize, Don’t Agonize: Strategic Success of Phytophthora Species. Microorganisms 8(6):917. 10.3390/microorganisms8060917
Shin G, Schacterle JK, Shyntum DY, Moleleki LN, Coutinho T, Sundin GW. (2019) Functional characterization of a global virulence regulator Hfq and identification of Hfq-dependent sRNAs in the plant pathogen Pantoea ananatis. Frontiers in Microbiology 10:1-19. 10.3389/fmicb.2019.02075
Shutt VM, Shin G, van der Waals JE, Goszczynska T, Coutinho T. (2018) Characterization of Ralstonia strains infecting tomato plants in South Africa. Crop Protection 112:56-62. 10.1016/j.cropro.2018.05.013
Siphathele Sibanda, Stanford Kwenda, Collins K. Tanui, Divine Shyntum, Teresa Coutinho, Lucy Moleleki. (2018) Transcriptome profiling reveals the EanI/R quorum sensing regulon in Pantoea ananatis LMG 2665T. Genes 9(3):148. 10.3390/genes9030148
Siphathele Sibanda, Lucy Moleleki, Divine Shyntum, Teresa Coutinho. 2018. Quorum Sensing in Gram-Negative Plant Pathogenic Bacteria. In: Advances in Plant Pathology. Intechopen., London SE1 9SG, United Kingdom, pp 67-89.
Tanui CK, Shyntum DY, Priem SL, Theron J, Moleleki LN. (2017) Influence of the ferric uptake regulator (Fur) protein on pathogenicity in Pectobacterium carotovorum subsp. brasiliense. Plos One 5(12) 10.1371/journal.pone.0177647
Gorshkov V, Kwenda S, Petrova O, Osipova E, Gogolev Y, Moleleki LN. (2017) Global Gene Expression Analysis of Cross-Protected Phenotype of Pectobacterium atrosepticum. PLoS ONE 12(1) 10.1371/journal.pone.0169536
Weller-Stuart T, Toth I, De Maayer P, Coutinho T. (2017) Swimming and twitching motility are essential for attachment and virulence of Pantoea ananatis in onion seedlings. Molecular Plant Pathology 18(5):734-745. 10.1111/mpp.12432
Kwenda S, Motlolometsi TV, Birch PRJ, Moleleki LN. (2016) RNA-seq profiling reveals defense responses in a tolerant potato cultivar to stem infection by Pectobacterium carotovorum ssp. brasiliense. Frontiers in Plant Science 7(1905) 10.3389/fpls.2016.01905
Kwenda S, Birch PRJ, Moleleki LN. (2016) Genome-wide identification of potato long intergenic noncoding RNAs responsive to Pectobacterium carotovorum subspecies brasiliense infection. BMC Genomics 17(614) 10.1186/s12864-016-2967-9
Sibanda S, Theron J, Shyntum DY, Moleleki LN, Coutinho TA. (2016) Characterization of two LuxI/R homologs in Pantoea ananatis LMG 2665 T. Canadian Journal of Microbiology 62(11):893-903. 10.1139/cjm-2016-0143
Moleleki LN, Pretorius RG, Tanui CK, Mosina G, Theron J. (2016) A quorum sensing‐defective mutant of Pectobacterium carotovorum subsp. brasiliense 1692 is attenuated in virulence and unable to occlude xylem tissue of susceptible potato plant stems. Molecular Plant Pathology 10.1111/mpp.12372
Kwenda S, Gorshkov V, Ramesh AM, Naidoo S, Rubagotti E, Birch PRJ, Moleleki LN. (2016) Discovery and profiling of small RNAs responsive to stress conditions in the plant pathogen Pectobacterium atrosepticum. BMC Genomics 17(1) 10.1186/s12864-016-2376-0
Onkendi EM, Ramesh AM, Kwenda S, Naidoo S, Moleleki LN. (2016) Draft Genome Sequence of a Virulent Pectobacterium carotovorum subsp. brasiliense Isolate Causing Soft Rot of Cucumber. Genome Announcements 4(1) 10.1128/genomeA.01530-15 PDF
Ronishree Magwanda, Lizahn Zwart, Nicolaas A. van der Merwe, Lucy Moleleki, Dave Kenneth Berger, Alexander A. Myburg, Sanushka Naidoo. (2016) Localization and Transcriptional Responses of Chrysoporthe austroafricana in Eucalyptus grandis Identify Putative Pathogenicity Factors. Front. Microbiol. 10.3389/fmicb.2016.01953
Mongae A, Moleleki L. (2015) The effect of β-aminobutyric acid (BABA) on root knot nematode and soft rot pathogen disease complexes in Solanum tuberosum plants. European Journal of Plant Pathology 142(1):117-124. 10.1007/s10658-015-0596-9
Shyntum D, Theron J, Moleleki L, Toth I, Venter SN, Coutinho TA. (2015) Pantoea ananatis utilizes a type VI secretion system for pathogenesis and bacterial competition. Molecular Plant-Microbe Interactions 28(4):420-431. 10.1094/MPMI-07-14-0219-R
De Maayer P, Chan WY, Rubagotti E, Venter SN, Toth IK, Birch PR, Coutinho TA. (2014) Analysis of the Pantoea ananatis pan-genome reveals factors underlying its ability to colonize and interact with plant, insect and vertebrate hosts. BMC Genomics 15:404. 10.1186/1471-2164-15-404 PDF
Onkendi EM, Moleleki LN. (2014) Characterization of Pectobacterium carotovorum subsp. carotovorum and brasiliense from diseased potatoes in Kenya. European Journal of Plant Pathology 139:557-566. 10.1007/s10658-014-0411-z
Shyntum DY, Venter SN, Moleleki LN, Toth I, Coutinho TA. (2014) Comparative genomics of type VI secretion systems in strains of Pantoea ananatis from different environments. BMC Genomics 15:163. 10.1186/1471-2164-15-163
Onkendi EM, Kariuki GM, Marais M, Moleleki LN. (2014) Threat of root-knot nematodes (Meloidogyne spp.) in Africa: a review. Plant Pathology 63(4):727-737. 10.1111/ppa.12202
Petrova O, Gorshkov V, Daminova A, Ageeva M, Moleleki LN, Gogolev Y. (2014) Stress response in Pectobacterium atrosepticum SCRI1043 under starvation conditions: adaptive reactions at a low population density. Research Microbiology 165(2):119-127. 10.1016/j.resmic.2013.11.004
Onkendi EM, Maluleke N, Moleleki LN. (2013) First report of Pectobacterium carotovorum subsp. brasiliense causing soft rot and blackleg diseases of potatoes in Kenya. Plant Disease 98(5):684. 10.1094/PDIS-09-13-0988-PDN
Kubheka GC, Coutinho T, Moleleki N, Moleleki LN. (2013) Colonisation patterns of a mCherry-tagged Pectobacterium carotovorum subsp. brasiliense in potato. Phytopathology 103(12):1269-1279. 10.1094/PHYTO-02-13-0049-R
Onkendi EM, Moleleki LN. (2013) Genetic diversity of root-knot nematodes (Meloidogyne spp.) in potatoes from South Africa. Plant Pathology 62 :1184–1192. 10.1111/ppa.12035
Amy Charkowski, Sylvie Reverchon, Pablo Rodr´ıguez Palenzuela, Michael San Francisco, Ian Toth, Shinji Tsuyumu, Jacquie van der Waals, Jan van der Wolf, Fr´ed´erique Van Gijsegem, Ching-Hong Yang, Nicole Perna, Andrew Pitman, Minna Pirhonen, Carlos Blanco, Guy Condemine, Dominique Expert, Thierry Franza, Christopher Hayes, Nicole Hugouvieux-Cotte-Pattat, Emilia L´ opez Solanilla, David Low, Lucy Moleleki, Iris Yedidia. (2012) The role of secretion systems and small molecules in soft rot Enterobacteriaceae pathogenicity. Annual Review of Phyotopathology 50:425-49. 10.1146/annurev-phyto-081211-173013
Mongae A, Kubheka GC, Moleleki N, Moleleki LN. (2012) The use of fluorescent protein tagging to study interactions between Root Knot Nematodes and Soft Rot Enterobacteriaceae. Letters in Applied Microbiology 56(4):258-63. 10.1111/lam.12045
Onkendi EM, Moleleki LN. (2012) Detection of Meloidogyne enterolobii in potatoes in South Africa and phylogenetic analysis based on intergenic region and the mitochondrial DNA sequences. European Journal of Plant Pathology 135(1):1-5. 10.1007/s10658-012-0142-y
Bulani IS, Moleleki LN, Albertyn J, Moleleki N. (2012) Development of a novel rDNA based plasmid for enhanced cell surface display on Yarrowia lipolytica. AMB Express 2:27. 10.1186/2191-0855-2-27
Moleleki LN, Mongae A, Onkendi EM, Kubheka GC. (2012) Characterisation of Pectobacterium wasabiae causing blackleg and soft rot diseases in South Africa. European Journal of Plant Pathology 135:279-288. 10.1007/s10658-012-0084-4
De Maayer P, Chan WY, Venter SN, Toth IK, Birch PRJ, Joubert F, Coutinho TA. (2010) Genome Sequence of Pantoea ananatis LMG20103, the Causative Agent of Eucalyptus Blight and Dieback. Journal of Bacteriology 192(11):2936-2937. 10.1128/JB.00060-10 PDF
van den Berg N, Berger DK, Hein I, Birch PRJ, Wingfield MJ, Viljoen A. (2009) Genes up-regulated in tolerant cavendish banana roots in response to Fusarium oxysporum f. sp. cubense infection. Acta Horticulturae 828:273-282. PDF
Toth IK , Birch PRJ , Liu H , Pritchard L , Humphries s, Ravensdale M , Moleleki L , Gilroy EM. (2008) What will a genome sequence do for fire blight research? Pectobacterium atrosepticum and potato - A case study. Acta Horticulturae 793:157-162.
Whisson SC, Pritchard L, Toth IK, Hein I, Chapman S, van West P, Grouffaud S, Armstrong MR, Gilroy EM, Morales JG, Avrova AO, Moleleki L, Boevink PC, Birch PR. (2007) A translocation signal for delivery of oomycete effector proteins into host plant cells. Nature 7166 :115-8. 10.1038/nature06203
Toth IK, Birch PRJ, Liu H, Pritchard L, Humphris S, Ravensdale M, Moleleki L, Gilroy EM. (2007) What will a genome sequence do for fire blight research? Pectobacterium atrosepticum and potato - A case study. Acta Horticulturae 793:157-162.
van den Berg N, Berger DK, Hein I, Birch PRJ, Wingfield MJ, Viljoen A. (2007) Tolerance in banana to Fusarium wilt is associated with early up-regulation of cell wall-strengthening genes in the roots. Molecular Plant Pathology 8(3):333-341. 10.1111/j.1364-3703.2007.00389.x PDF
Crampton BG, van den Berg N, Hein I, Birch PRJ, Berger DK. (2004) High-throughput screening of suppression subtractive hybridization cDNA libraries using DNA microarray analysis. BioTechniques 37(5):818-824.
Heinze B, Thokoane LN, Williams NJ, Barnes JM, Rutherford RS. (2001) The smut-sugarcane interaction as a model system for the integration of marker discovery and gene isolation. Proc. S. Afr. Sug. Technol. Ass 75 :88-93.
Thokoane LN, Rutherford RS. (2001) cDNA-AFLP differential display of sugarcane (Saccharum spp, hybrids) genes induced by challenge with the fungal pathogen Ustilago scitaminea (sugarcane smut). Proc. S. Afr. Sug. Technol. Ass 75:104-107.
Watt MP, Thokoane LN, Mycock D, Blakeway F. (2000) In vitro storage of Eucalyptus grandis germplasm under minimal growth conditions. Plant Cell Tissue and Organ Culture 61 (2 ):161-164.
Thokoane LN, Butterfield MK, Harvey M, Huckett BI. (1999) Progress towards a fingertyping database for sugarcane varieties. Proc S Afr Sug Technol. Ass 73:165-.
Pectobacterium brasiliense 1692 Chemotactic Responses and the Role of