Plant pathogens belonging to the fungal species Fusarium
are of great importance to continued food production in the world.
They are well known to cause diseases of important staple food crops
such as maize, wheat, sorghum, rice and bananas, and in some instances
produce mycotoxins that can be fatal to humans and animals. Many diseases
caused by Fusarium spp. and their toxins cannot be treated,
and have to be prevented. The programme on Fusarium diseases
of agricultural crops, therefore, focuses on the characterisation
and management of Fusarium spp. associated with Fusarium
wilt and mycotoxin production in staple food crops, specifically related
to the identification and characterisation of Fusarium spp.
using conventional and molecular techniques, quantitative detection
of Fusarium spp. and their mycotoxins, epidemiology and etiology
of Fusarium spp., field management of Fusarium diseases
and the mycotoxins they produce, biological control of pathogenic
Fusarium isolates, and understanding the interaction of plants
The most effective means to prevent damage caused by Fusarium
spp. to agricultural crops is by planting tolerant or resistant material.
Such tolerance/resistance depends on the ability of the fungus to
enter, colonise and damage the plant, and the ability of the plant
to prevent or resist damage caused by the fungus. To exploit plant
resistance as a means of disease management, a proper knowledge of
Fusarium, its genetics, pathogenicity and toxicity, under
different environmental conditions, is required. In this programme,
the interaction between agricultural crops and Fusarium spp.
is investigated by means of comparative and functional genetics of
the Fusarium-plant interactions, the isolation and identification
of defence-related genes in agricultural crops, the identification
of virulence genes in Fusarium, studies on the evolutionary
biology and phylogenetics of Fusarium, and the unconventional
improvement of plants for resistance to Fusarium spp. Greenhouse
and field evaluation of natural and induced resistance to Fusarium
pathogens of agricultural crops are also conducted in collaboration
with the ARC.
Fruit and post-harvest
pathology (Dr Cheryl
Plant disease and decay impacts on the profitability
of deciduous fruit production, and negatively influences consumer
confidence in the products. There is an increasing demand from consumers,
and consequently retailers and marketers, for fruit with little or
no pesticide/fungicide residues. Producing quality fruit under these
constraints is a major challenge for the deciduous fruit industry,
which currently relies heavily on pre and postharvest chemicals for
disease and decay control. The main objective of the Fruit and Postharvest
Pathology Research Programme within the department, is to improve
disease and decay control in deciduous fruit products, through the
design of appropriate integrated disease management strategies, with
reduced reliance on fungicides.
Projects within this programme are: Postharvest decay of pears, with
focus decay caused by Botrytis cinerea; etiology and epidemiology
of core rot of apples; etiology and epidemiology of bull’s eye
rot of apples; the efficacy of sanitation practices in reducing apple
scab; and the occurrence and importance of overwintering of apple
scab conidia in the Western Cape.
(Dr Lizel Mostert)
The field of phytomycology entails the study of fungal systematics
and taxonomy of fungal plant pathogens. This knowledge enables the
correct identification of causal agents of diseases. The etiology
of plant diseases is very important as the first step in understanding
the disease aiding in working towards a control strategy. Plant diseases
are often complex, being caused by a variety of fungal taxa. The identification
and relevance of these taxa are very important. A focus area of research
includes the etiology and epidemiology of trunk diseases of grapevine,
pome and stone fruit trees.
Phytomycology also entails the development and use of up-to-date molecular
identification tools for fungal pathogens that can be used to ensure
clean planting material and for early disease warning. The compiling
of reliable information regarding the status of fungal pathogens within
South Africa is very important. This, together with expertise in phytomycology,
is of the utmost importance in order to ensure market access within
the agriculture sector, as well as food security in South Africa.
Phytosanitary support is provided on an ongoing basis to the deciduous
fruit industry (DFPT).
The biological control of plant diseases is important in providing
an alternative to chemical control. It allows producers to limit fungicide
residues which are becoming an important market requirement. The biocontrol
programme focuses on the use of Trichoderma species in the
control of grapevine trunk diseases. Various aspects are being researched
to understand the mechanisms involved and to optimise the application.
These include the formulation, time of application, secondary metabolites
produced by the Trichoderma strains, and the host-Trichoderma
interactions. Two isolates occurring naturally in grapevines have
been tested in vitro and in vivo and is in the process of developing
a product that can be used as a pruning wound protectant.
Citrus pathology (Dr
Fungicide application technology
In plant disease control, the use of very effective aqueous remedies
(i.e. fungicides, biocontrol agents, GRAS chemicals, etc.) sometimes
yield disappointing results whereby growers suffer economic losses.
In these cases, disease control failure is often attributed to insufficient
application of the remedy. In this research programme, various conventional
and novel application technologies are evaluated and optimised in
citrus orchards and packhouses in order to ensure biologically effective
residue loading onto susceptible plant parts, without exceeding allowable
maximum residue levels. Concomitant aims involve addressing cost and
time efficiency aspects of application methods, whereby production
and environmental costs are directly influenced. The methodology employed
involves a proprietary deposition assessment protocol using fluorometry,
digital photography and image analyses, as well as residue analysis
and biological efficacy tests.
Epidemiology of Citrus Black Spot
Citrus Black Spot (CBS) is a cosmetic disease of citrus
fruit. However, its causal organism, Guignardia citricarpa,
is regarded as a quarantine organism in certain countries. The South
African citrus industry is the second largest exporter of fresh citrus
fruit in the world, and therefore CBS is an economically important
disease given the market access implications it poses. In this research
programme at USPP, the epidemiology of this disease is studied to
understand and predict its behaviour under climatically diverse conditions.
This will allow improved control programmes, but will also assist
in ongoing market access deliberations. Additionally, population genetics
of G. citricarpa will be studied on a global scale in order
to ascertain the global movement of this organism and the relative
importance of sexual and asexual reproduction under diverse climates.
Oomycete research (Dr
of past 3 years
- Blomme, G., Ploetz, R., Jones, D., De Langhe, E., Price, N., Gold,
C., Geering, A., Viljoen, A., Karamura, D., Pillay, M., Tinzaara, W.,
Teycheney, P.-Y., Lepoint, P., Karamura, E. & Buddenhagen, I. 2013.
A historical overview of the appearance and spread of Musa
pests and pathogens on the African continent: highlighting the importance
of clean Musa planting materials and quarantine measures. Annals
of Applied Biology 162: 4-26.
- Erasmus, A., Lennox, C.L., Smilanick, J.L., Lesar, K. & Fourie,
P.H. 2013. Imazalil residue loading and green mould control on citrus
fruit as affected by formulation, solution pH and exposure time in aqueous
dip treatments. Postharvest Biology and Technology
- Fourie, P., Schutte, T., Serfontein, S. & Swart, F. 2013. Modeling
the effect of temperature and wetness on Guignardia pseudothecium
maturation and ascospore release in citrus orchards. Phytopathology
- Fry, W.E., McGrath, M.T., Seaman, A., Zitter, T.A., McLeod, A., Danies,
G., Small, I.M., Myers, K., Everts, K., Gevens, A.J., Gugino, B.K.,
Johnson, S.B., Judelson, H., Ristaino, J., Roberts, P., Secor, G., Seebold
Jr., K., Snover-Clift, K., Wyenandt, A., Grünwald, N.J. & Smart,
C.D. 2013. The 2009 late blight pandemic in the Eastern United States
– causes and results. Plant Disease 97: 296-306.
- Geiser, D.M., Aoki, T., Bacon, C.W., Baker, S.E., Bhattacharyya, M.K.,
Brandt, M.E., Brown, D.W., Burgess, L.W., Chulze, S., Coleman, J.J.,
Correll, J.C., Covert, S.F., Crous, P.W., Cuomo, C.A., De Hoog, G.S.,
Di Pietro, A., Elmer, W.H., Epstein, L., Frandsen, R.J.N., Freeman,
S., Gagkaeva, T., Glenn, A.E., Gordon, T.R., Gregory, N.F., Hammond-Kosack,
K.E., Hanson, L.E., del Mar Jímenez-Gasco, M., Kang, S., Kistler,
H.C., Kuldau, G.A., Leslie, J.F., Logrieco, A., Lu, G., Lysøe,
E., Ma, L-J., McCormick, S.P., Migheli, Q., Moretti, A., Munaut, F.,
O’Donnell, K., Pfenning, L., Ploetz, R.C., Proctor, R.H., Rehner,
S.A., Robert, V.A.R.G., Rooney, A.P., bin Salleh, B., Scandiani, M.M.,
Scauflaire, J., Short, D.P.G., Steenkamp, E., Suga, H., Summerell, B.A.,
Sutton, D.A., Thrane, U., Trail, F., Van Diepeningen, A., VanEtten,
H.D., Viljoen, A., Waalwijk, C., Ward, T.J., Wingfield, M.J., Xu, J-R.,
Yang, X-B, Yli-Mattila, T. & Zhang, N. 2013. One fungus, one name:
defining the genus Fusarium in a scientifically robust way that preserves
longstanding use. Phytopathology 103: 400-408.
- Njombolwana, N.S., Erasmus, A. & Fourie, P.H. 2013. Evaluation
of curative and protective control of Penicillium digitatum following
imazalil application in wax coating. Postharvest Biology and
Technology 77: 102-110.
- Paparu, P., Dubois, T., Coyne, D. & Viljoen, A. 2013. Differential
gene expression in East Africa highland bananas (Musa spp.):
Interactions between non-pathogenic Fusarium oxysporum V5w2
and Radopholus similis. Physiological and Molecular
Plant Pathology 82: 56-63.
- Pule, B.B., Meitz, J.C., Thompson, A.H., Linde, C.C., Fry, W.E., Langenhoven,
S.D., Meyers, K.L., Kandolo, D.S., van Rij, N.C. & McLeod, A. 2013.
Phytophthora infestans populations in central, eastern and
southern African countries consist of two major clonal lineages. Plant
Pathology 62: 154-165.
- Sutherland, R., Viljoen, A., Myburg, A.A. & Van den Berg, N. 2013.
Pathogenicity associated genes in Fusarium oxysporum f. sp.
cubense race 4. South African Journal of Science
109 (5/6): 1-10.
- Van Zyl, J. Gideon, Fourie, Paul H. & Schutte, Gerhardus C. 2013.
Spray deposition assessment and benchmarks for control of Alternaria
brown spot on mandarin leaves with copper oxychloride. Crop
Protection 46: 80-87.
- Wessels, B.A., Lamprecht, S.C., Linde, C.C., Fourie, P.H. & Mostert,
L. 2013. Characterization of the genetic variation and fungicide resistance
in Botrytis cinerea populations on rooibos seedlings in the
Western Cape of South Africa. European Journal of Plant Pathology
- Boutigny, A.-L., Beukes, I., Small, I., Zühlke, S., Spiteller,
M., Van Rensburg, B.J., Flett, B. & Viljoen, A. 2012. Quantitative
detection of Fusarium pathogens and their mycotoxins in South
African maise. Plant Pathology 61: 522-531.
- Carstens, E., Le Roux, H.F., Holtzhausen, M.A., Van Rooyen, L., Coetzee,
J., Wentzel, R., Laubscher, W., Dawood, Z., Venter, E., Schutte, G.C.,
Fourie, P.H. & Hattingh, V. 2012. Citrus black spot is absent in
the Western Cape, Northern Cape and Free State Provinces. South
African Journal of Science 108 (7/8): 1-6.
- Gouws, R. & McLeod, A. 2012. Fissure scab, a new symptom associated
with potato common scab caused by a Streptomyces sp. in South
Africa. Plant Disease 96: 1223.
- Gramaje, D., Agusti-Brisach, C., Pérez-Sierra, A., Moralejo,
E., Olmo, D., Mostert, L., Damm, U. & Armengol, J. 2012. Fungal
trunk pathogens associated with wood decay of almond trees on Mallorca
(Spain). Persoonia 28: 1-13.
- Hu, C.-H., Perez, F.G., Donahoo, R., McLeod, A., Myers, K., Ivors,
K., Secor, G., Roberts, P.D., Deahl, K.L., Fry, W.E. & Ristaino,
J.B. 2012. Recent genotypes of Phytophthora infestans in the
Eastern United States reveal clonal populations and reappearance of
mefenoxam sensitivity. Plant Disease 96: 1323-1330.
- Schutte, G.C., Kotze, C., van Zyl, J.G. & Fourie, P.H. 2012. Assessment
of retention and persistence of copper fungicides on orange fruit and
leaves using fluorometry and copper residue analyses. Crop Protection
- Small, I.M., Flett, B.C., Marasas, W.F.O., McLeod, A., Stander, M.A.
& Viljoen, A. 2012. Resistance in maize inbred lines to Fusarium
verticillioides and fumonisin accumulation in South Africa. Plant
Disease 96: 881-888.
- Small, I.M., Flett, B.C., Marasas, W.F.O., McLeod, A. & Viljoen,
A. 2012. Use of resistance elicitors to reduce Fusarium ear rot and
fumonisin accumulation in maize. Crop Protection 41:
- Southwood, M.J., Viljoen, A., Mostert, G. & McLeod, A. 2012.
Molecular identification of two vegetative compatibility groups of Fusarium
oxysporum f.sp. cepae. Phytopathology 102:
- Southwood, M.J., Viljoen, A., Mostert, L., Rose, L.J. & McLeod,
A. 2012. Phylogenetic and biological characterization of Fusarium
oxysporum isolates associated with onion in South Africa. Plant
Disease 96 (9): 1250-1261.
- Van Wyk, S.J.P., Boutigny, A.-L., Coutinho, T.A. & Viljoen, A.
2012. Sanitation of a South African forestry nursery contaminated with
Fusarium circinatum using hydrogen peroxide at specific oxidation
reduction potentials. Plant Disease 96: 875-880.
- Belgrove, A., Steinberg, C. & Viljoen, A. 2011. Evaluation of
nonpathogenic Fusarium oxysporum and Pseudomonas fluorescens
for Panama disease control. Plant Disease 95: 951-959.
- Boutigny, A.-L., Beukes, I. & Viljoen, A. 2011. Head blight of
barley in South Africa is caused by Fusarium graminearum
with a 15-adon chemotype. Journal of Plant Pathology
93 (2): 321-329.
- Boutigny, A.-L., Ward, T.J., van Coller, G.J., Flett, B., Lamprecht,
S.C., O’Donnell, K. & Viljoen, A. 2011. Analysis of the Fusarium
graminearum species complex from wheat, barley and maize in South
Africa provides evidence of species-specific differences in host preference.
Fungal Genetics and Biology 48: 914-920.
- Cloete, M., Fourie, P.H., Damm, U., Crous, P.W. & Mostert, L.
2011. Fungi associated with die-back symptoms of apple and pear trees,
a possible inoculum source of grapevine trunk disease pathogens. Phytopathologia
Mediterranea 50 (Supplement): S176-S190.
- Crous, P.W., Summerell, B.A., Swart, L., Denman, S., Taylor, J.E.,
Bezuidenhout, C.M., Palm, M.E., Marincowitz, S. & Groenewald, J.Z.
2011. Fungal pathogens of Proteaceae. Persoonia
- Erasmus, A., Lennox, C.L., Jordaan, H., Smilanick, J.L., Lesar, K.
& Fourie, P.H. 2011. Imazalil residue loading and green mould control
in citrus packhouses. Postharvest Biology and Technology
- Fourie, G., Steenkamp, E.T., Ploetz, R.C., Gordon, T.R. & Viljoen,
A. 2011. Current status of the taxonomic position of Fusarium oxysporum
formae specialis cubense within the Fusarium oxysporum
complex. Infection, Genetics and Evolution 11: 533-542.
- Gramaje, D., Mostert, L. & Armengol, J. 2011. Characterization
of Cadophora luteo-olivacea and C. melinii isolates
obtained from grapevines and environmental samples from grapevine nurseries
in Spain. Phytopathologia Mediterranea 50 (Supplement):
- Kotze, C., Van Niekerk, J., Mostert, L. Halleen, F. & Fourie,
P. 2011. Evaluation of biocontrol agents for grapevine pruning wound
protection against trunk pathogen infection. Phytopathologia
Mediterranea 50 (Supplement): S247-S263.
- Mutawila, C., Fourie, P.H., Halleen, F. & Mostert, L. 2011. Grapevine
cultivar variation to pruning wound protection by Trichoderma
species against trunk pathogens. Phytopathologia Mediterranea
50 (Supplement): S264-S276.
- Mutawila, C., Fourie, P.H., Halleen, F. & Mostert, L. 2011. Histo-pathology
study of the growth of Trichoderma harzianum, Phaeomoniella
chlamydospora and Eutypa lata on grapevine pruning wounds.
Phytopathologia Mediterranea 50 (Supplement): S46-S60.
- Ncube, E., Flett, B.C., Waalwijk, C. & Viljoen, A. 2011. Fusarium
spp. and levels of fumonisins in maize produced by subsistence farmers
in South Africa. South African Journal of Science 107
- Spies, C.F.J., Mazzola, M., Botha, W.J., Langenhoven, S.D., Mostert,
L. & McLeod, A. 2011. Molecular analyses of Pythium irregulare isolates
from grapevines in South Africa suggest a single variable species. Fungal
Biology 115: 1210-1224.
- Spies, C.F.J., Mazzola, M., Botha, W.J., Van der Rijst, M., Mostert,
L. & McLeod, A. 2011. Oogonial biometry and phylogenetic analyses
of the Pythium vexans species group from woody agricultural
hosts in South Africa reveal distinct groups within this taxon. Fungal
Biology 115: 157-168.
- Spies, C.F.J., Mazzola, M. & McLeod, A. 2011. Characterisation
and detection of Pythium and Phytophthora species
associated with grapevines in South Africa. European Journal
of Plant Pathology 131: 103-119.
- Tesfai Tewoldemedhin, Y., Mazzola, M., Botha, W.J., Spies, C.F.J.
& McLeod, A. 2011. Characterization of fungi (Fusarium
and Rhizoctonia) and oomycetes (Phytophthora and Pythium)
associated with apple orchards in South Africa. European Journal
of Plant Pathology 130: 215-229.
- Tesfai Tewoldemehin, Y., Mazzola, M., Labuschagne, I. & McLeod,
A. 2011. A multi-phasic approach reveals that apple replant disease
is caused by multiple biological agents, with some agents acting synergistically.
Soil Biology & Biochemistry 43: 1917-1927.
- Tesfai Tewoldemedhin, Y., Mazzola, M, Mostert, L. & McLeod, A.
2011. Cylindrocarpon species associated with apple tree roots
in South Africa and their quantification using real-time PCR. European
Journal of Plant Pathology 129: 637-651.
- Van der Walt, L., Spotts, R.A., Ueckermann, E.A., Smit, F.J., Jensen,
T. & McLeod, A. 2011. The association of Tarsonemus mites
(Acari: Heterostigmata) with different apple developmental stages and
apple core rot diseases. International Journal of Acarology
37: Suppl. 1: 71-84.
- Van Niekerk, J.M., Bester, W., Halleen, F., Crous, P.W. & Fourie,
P.H. 2011. The distribution and symptomatology of grapevine trunk disease
pathogens are influenced by climate. Phytopathologia Mediterranea
50 (Supplement): S98-S111.
- Van Niekerk, J.M. Halleen, F. & Fourie, P.H. 2011. Temporal susceptibility
of grapevine pruning wounds to trunk pathogen infection in Souht African
grapevines. Phytopathologia Mediterranea 50 (Supplement):
- Van Niekerk, J.M., Strever, A.E., du Toit, P.G., Halleen, F. &
Fourie, P.H. 2011. Influence of water stress on Botryosphaeriaceae disease
expression in grapevines. Phytopathologia Mediterranea
50 (Supplement): S151-S165.
- White, C-L. Halleen, F., Fischer, M. & Mostert, L. 2011. Characterisation
of the fungi associated with esca diseased grapevines in South Africa.
Phytopathologia Mediterranea 50: 204-223.
- Bezuidenhout, C.M., Denman, S., Kirk, S.A., Botha, W.J., Mostert,
L. & McLeod, A. 2010. Phytophthora taxa associated with
cultivated Agathosma, with emphasis on the P. citricola
complex and P. capensis sp. nov. Persoonia
- Bonants, P., Groenewald, E., Rasplus, J.Y., Maes, M., de Vos, P.,
Frey, J., Boonham, N., Nicolaisen, M., Bertacini, A., Robert, V., Barker,
I., Kox, L., Ravnikar, M., Tomankova, K., Caffier, D., Li, M., Armstrong,
K., Freitas-Astúa, J., Stefani, E., Cubero, J. & Mostert,
L. 2010. QBOL: a new EU project focusing on DNA barcoding of Quarantine
organisms. Bulletin OEPP/EPPO Bulletin 40: 30-33.
- Damm, U., Fourie, P.H. & Crous, P.W. 2010. Coniochaeta
(Lecythophora), Collophora gen. nov. and Phaeomoniella
species associated with wood necroses of Prunus trees.
Persoonia 24: 60-80.
- Dunn, A.R., Milgroom, M.G., Meitz, J.C., McLeod, A., Fry, W.E., McGrath,
M.T., Dillard, H.R. & Smart, C.D. 2010. Population structure and
resistance to mefenoxam of Phytophthora capsici in New York
State. Plant Disease 94: 1461-1468.
- Kiggundu, A., Muchwezi, J., Van der Vyver, C., Viljoen, A., Vorster,
J., Schlüter, U., Kunert, K. & Michaud, D. 2010. Deleterious
effects of plant cystatins against the banana weevil Cosmopolites
sordidus. Archives of Insect Biochemistry and Physiology
- Meitz, J.C., Linde, C.C., Thompson, A., Langenhoven, S. & McLeod,
A. 2010. Phytophthora capsici on vegetable hosts in South Africa:
distribution, host range and genetic diversity. Australasian
Plant Pathology 39: 431-439.
- Mostert, L., Bester, W., Jensen, T., Coertze, S., Van Hoorn, A., Le
Roux, J., Retief, E., Wood, A. & Aime, M.C. 2010. First report of
leaf rust of blueberry caused by Thekopsora minima on vaccinium
corymbosum in the Western Cape, South Africa. Plant Disease
- Ncube, E., Flett, B.C., Waalwijk, C. & Viljoen, A. 2010. Occurrence
of aflatoxins and aflatoxin-producing Aspergillus spp. associated
with groundnut production in subsistence farming systems in South Africa.
South African Journal of Plant & Soil 27 (2): 195-198.
- Paparu, P., Dubois, T., Coyne, D. & Viljoen, A. 2010. Effect of
Fusarium oxysporum endophyte inoculation on the activities
of phenylpropanoid pathway enzymes and Radopholus similis numbers
in susceptible and tolerant East African Highland bananas. Nematology
- Van der Walt, L., Spotts, R.A., Visagie, C.M., Jacobs, K, Smit, F.J.
& McLeod, A. 2010. Penicillium species associated with
preharvest wet core rot in South Africa and their pathogenicity on apple.
Plant Disease 94 (6): 666-675.
- Van Niekerk, J.M., Calitz, F.J., Halleen, F. & Fourie, P.H. 2010.
Temporal spore dispersal patterns of grapevine trunk pathogens in South
Africa. European Journal of Plant Pathology 127: 375-390.
- Van Zyl, S.A., Brink, J-C., Calitz, F.J., Coertze, S. & Fourie,
P.H. 2010. The use of adjuvants to improve spray deposition and Botrytis
cinerea control on Chardonnay grapevine leaves. Crop Protection
- Van Zyl, S.A., Brink, J-C., Calitz, F.J. & Fourie, P.H. 2010.
Effects of adjuvants on deposition efficiency of fenhexamid sprays applied
to Chardonnay grapevine foliage. Crop Protection 29:
- Visser, M., Gordon, T., Fourie, G. & Viljoen, A. 2010. Characterisation
of South African isolates of Fusarium oxysporum f. sp. cubense
from Cavendish bananas. South African Journal of Science
Pagemaster: Tel +27(21) 808 4799
Last update: 14 June 2013