Thesis (MScAgric)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Soilborne diseases of grapevines represent a complex problem with limited
information available, both locally and internationally. Previous research in South Africa
indicated that Phytophthora and Pythium spp. were the most widespread and devastating
pathogens in grapevine nurseries and vineyards in the Western Cape province. The local
grapevine industry is currently expanding; new cultivars, methods and agricultural chemicals
are being used which can affect soilborne pathogens. It has therefore become necessary to reassess
the status of soilborne pathogens in nurseries, since information in this regard is crucial
for the development of disease management practices for the expanding local grapevine
industry.
Soilborne fungal genera associated with roots and crowns of declining nursery
grapevines were assessed in surveys conducted at three different grapevine nurseries in the
Western Cape province. Cylindrocarpon, Fusarium, Pythium, and Rhizoctonia spp. were
consistently isolated from roots and crowns of declining nursery grapevines.
Cylindrocladiella spp. and Phytophthora cinnamomi were infrequently isolated from diseased
roots, crowns and soil whereas Pythium spp. were abundant in most of the soils. Results
suggest that the status of soilborne fungal pathogens in grapevine nurseries in the Western
Cape province has changed over the last 30 years.
The DNA phylogeny and pathogenicity of the isolates of Cylindrocladiella were
determined. Four species of Cylindrocladiella occur on grapevines in South Africa, namely
C. lageniformis, C. parva, C. peruviana, as well as a new species, described in this study as
C. viticola, which forms part of the C. infestans species complex. Pathogenicity trials were
inconclusive.
Ten Fusarium spp. were isolated from roots and crowns of declining nursery
grapevines, namely F. acuminatum, F. anthophilum, F. chlamydosporum, F. equiseti, F.
nygamai, F. oxysporum, F. proliferatum, F. scirpi, F. semitectum and F. solani. The
dominant species was F. oxysporum, followed by F. proliferatum and F. solani. In
pathogenicity trials F. oxysporum and F. solani significantly reduced root volume, root dry
mass, length of new shoots, stem diameter and number of leaves, but increased the percentage
of chlorotic leaves and root rot severity. Fusarium proliferatum also caused a significant reduction in new shoot growth, number of leaves and increased root rot severity compared to
the controls. Fusarium so/ani seems to be more virulent than F. oxysporum, followed by F.
pro/iferatum. This is the first report of F. oxysporum, F. pro/iferatum and F. so/ani as
pathogens of grapevines in South Africa, and the first report of F. proliferatum as a pathogen
of grapevines in the world.
Phytophthora cinnamomi was isolated at low frequencies from declined grapevines,
although present in the rhizosphere soil. It is possible that the extensive use of downy mildew
chemicals in grapevine nurseries may protect grapevines from infection by P. cinnamomi.
The effect of chemicals used to combat downy mildew on Phytophthora root rot of nursery
grapevines was evaluated in a glasshouse. There was very little discernable effect of the
chemicals tested relative to the control plants for the parameters measured and it was
concluded that the inoculation technique needed refinement. However, plants treated with
phosphorous acid tended to be taller and have more leaves, greater stem diameter and root
volume than controls or plants treated with the other chemicals. The data obtained in this
study are not conclusive, but indicated certain trends that more glasshouse trials and field
trials would resolve.
Results presented in this thesis indicate that a major shift has occurred in the status of
soilborne fungi associated with roots and crowns of grapevines in nurseries in the Western
Cape since the 1970s when Phytophthora and Pythium were predominant. The prevalence
and role of soilborne fungi need to be determined so that new appropriate disease
management strategies can be developed to limit losses in grapevine nurseries and ensure the
sustainable production of healthy plants for the grapevine industry. / AFRIKAANSE OPSOMMING: 'N ONDERSOEK NA GRONDGEDRAAGDE SWAMME GEASSOSIEER MET
WORTELS EN KRONE VAN WINGERD IN KWEKERYE
Grondgedraagde siektes van wingerd is 'n komplekse probleem waaroor min inligting,
beide plaaslik en internasionaal, beskikbaar is. Vorige navorsing in Suid-Afrika het aangedui
dat swamme van die genera Phytophthora en Pythium die mees algemene en vernietigende
grondgedraagde patogene in kwekerye en wingerde in die Wes-Kaap provinsie is. Die
plaaslike wingerdbedryf brei huidiglik uit; nuwe kultivars, metodes en landbouchemikalieë
word gebruik wat 'n invloed kan hê op grondgedraagde patogene. Gevolglik het dit
noodsaaklik geword om die status van grondgedraagde patogene in wingerdkwekerye weer te
bepaal, aangesien inligting in hierdie verband noodsaaklik is vir die ontwikkeling van siekte
bestuurspraktyke vir die ontwikkelende plaaslike wingerdbedryf.
Grondgedraagde swamgenera geassosieer met wortels en krone van terugsterwende
wingerd in kwekerye is bepaal in opnames wat by drie verskillende wingerdkwekerye in die
Wes-Kaap provinsie uitgevoer is. Cylindrocarpon, Fusarium, Pythium, en Rhizoctonia spp. is
konstant vanuit wortels en krone van terugsterwende wingerdplante in kwekery geïsoleer,
Cylindrocladiella spp. en Phytophthora cinnamomi is ongereeld vanuit siek wortels, krone en
grond geïsoleer, terwyl Pythium spp. algemeen in meeste gronde voorgekom het. Resultate
dui daarop dat die status van grondgedraagde swampatogene in wingerdkwekerye in die Wes-
Kaap provinsie oor die laaste 30 jaar verander het.
Die DNA filogenie en patogenisiteit van die isolate van Cylindrocladiella is bepaal.
Vier spesies van Cylindrocladiella kom voor op wingerd in Suid-Afrika, naamlik C.
lageniformis, C. parva, C. peruviana, sowel as 'n nuwe spesie, wat in hierdie studie as C.
viticola aangedui is en wat deel is van die C. infestans spesie kompleks. Patogenisiteits
proewe was onvoldoende om die patogeniese status van die swam me te bepaal.
Tien Fusarium spp. is vanuit wortels en krone van terugsterwende wingerdplante in
kwekery geïsoleer, naamlik F. acuminatum, F. anthophilum, F. chlamydosporum, F. equiseti,
F. nygamai, F. oxysporum, F. proliferatum, F. scirpi, F. semitectum en F. solani. Die
dominante spesies was F. oxysporum, gevolg deur F. proliferatum en F. solani. In
pathogenisteitsproewe het F. oxysporum en F. solani gelei tot 'n betekenisvolle laer
wortelvolume, droë massa van wortels, lengte en droë massa van nuwe groei en aantal blare,
maar het die persentasie chlorotiese blare en graad van wortelvrot verhoog. Fusarium proliferatum het ook gelei tot 'n betekenisvolle afname in lengte en massa van nuwe groei,
aantal blare en 'n verhoogde graad van wortelvrot in vergelyking met die kontrole
behandelings. Dit wil voorkom asof Fusarium solani meer virulent is as F. oxysporum,
gevolg deur F. proliferatum. Hierdie is die eerste aanmelding van F. oxysporum, F.
proliferatum en F. solani as patogene van wingerd in Suid-Afrika, en die eerste aanmelding
van F. proliferatum as 'n patogeen van wingerd in die wêreld.
Phytophthora cinnamomi is konstant teen lae frekwensies vanuit terugsterwende
wingerd in kwekerye geïsoleer, alhoewel dit in risosfeer gronde teenwoordig was. Dit is
moontlik dat die ekstensiewe gebruik van chemikalieë teen donsskimmel in wingerdkwekerye
die wingerdplante kan beskerm teen infeksie deur P. cinnamomi. Die effek van chemikalieë
wat gebruik word teen donsskimmel op Phytophthora wortelverrotting van wingerd in
kwekerye, is 'n glashuis geëvalueer. Die chemikalieë wat gestoets is, het vir die gemete
parameters, tot baie min onderskeibare effek gelei relatief tot die kontrole plante, en daar is
afgelei dat die inokulasie tegniek verbetering benodig. Plante wat met fosforiensuur behandel
is, het egter geneig om langer te wees met meer blare, 'n groter stamdeursnee en
wortelvolume as kontrole plante of plante behandel met ander chemikalieë. Data verkry
vanuit die hierdie studie was onvoldoende, maar sekere neigings is aangedui wat deur verdere
glashuis- en veldproewe verklaar sal word.
Resultate wat in hierdie tesis weergegee is, het aangedui dat 'n algehele verskuiwing
in die status van grondgedraagde swamme geassosieer met wortels en krone van wingerd in
kwekerye vanaf die 1970s, toe Phytophthora en Pythium die dominante genera was,
plaasgevind het. Die voorkoms en rol van grondgedraagde swamme moet bepaal word, sodat
nuwe voldoende siektebestuurspraktyke ontwikkel kan word om verliese in wingerdkwekerye
te beperk en sodoende die volhoubare produksie van gesonde plante vir die wingerdbedryf te
verseker.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/49844 |
| Date | 03 1900 |
| Creators | Van Coller, Gerhardus J. (Gerhardus Johannes) |
| Contributors | Denman, S., Lamprecht, S. C., Crous, P. W., Stellenbosch University. Faculty of AgriSciences. Dept. of Plant Pathology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 155 p. : ill. |
| Rights | Stellenbosch University |
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