Thesis (MSc)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: This thesis consists of four chapters that present research findings on Colletotrichum
diseases associated with Proteaceae worldwide. The first chapter is a review of literature
regarding the taxonomy and histology of Colletotrichum species associated with Proteaceae. The
literature is not restricted to Proteaceae hosts, as information regarding Colletotrichum on
Proteaceae is very limited.
In chapter two, Colletotrichum spp. associated with proteaceous hosts growing in various
parts of the world were identified based on morphology, sequence data of the internal transcribed
spacer region (ITS-I, ITS-2), the 5.8S gene, and partial sequences of the B-tubulin gene. Four
species of Colletotrichum were associated with Proteaceae. Colletotrichum gloeosporioides was
isolated from Protea cynaroides cultivated in South Africa and Zimbabwe and from a
Leucospermum sp. in Portugal, but is known to occur worldwide on numerous hosts. A recently
described species, C. boninense, was associated with Zimbabwean and Australian Proteaceae, but
also occurred on a Eucalyptus sp. in South Africa. This represents a major geographical and host
extension for the species, and a description of the African strains is provided. Colletotrichum
crassipes was represented by a single isolate obtained from a Dryandra plant in Madeira.
Colletotrichum acutatum was isolated from Protea and Leucadendron in South Africa as well as
from other proteaceous hosts occurring elsewhere. Colletotrichum acutatum f. sp. hakea was
isolated from Hakea in South Africa. In chapter three, pathogenicity of these Colletotrichum species to certain proteas was
established, relative aggressiveness of the different species tested and host response to them were
compared as well as the effect that wounding had on host response. From the results obtained it
is concluded that C. acutatum and C. gloeosporioides are the primary pathogens associated with
Colletotrichum leaf necrosis, and C. acutatum is the main cause of anthracnose and stem necrosis
of Proteaceae in South Africa.
A histological study was performed in chapter four in response to the findings from the
previous chapter. The behaviour of two C. acutatum isolates (one originating from Protea and
the other from Hakea, C. acuataum f.sp. hakea) was studied on inoculated Protea leaf surfaces
using light and scanning electron microscopy. Colletotrichum acutatum from Protea formed
melanised appressoria on the leaf surface, whereas C. acutatum from Hakea formed very low
numbers of both melanised and unmelanised appressoria. Most of the appressoria formed by C.
acutatum from Protea were formed on the cell junctions and on the periclinal walls of the
epidermal cells. From this study it is clear that C. acutatum f. sp. hakea is not a pathogen of
Protea. Consequently the current use of this isolate as a biological control agent of Hakea in
South Africa poses no threat to indigenous Protea species. Colletotrichum acutatum from Protea
(although closely related to C. acutatum f. sp. hakea), is a pathogen of Protea, which was
confirmed by histological observations.
In conclusion, the present study has shown that several species of Colletotrichum are
associated with diseased Proteaceae. These species differed in their pathogenicity and
aggressiveness when inoculated onto certain protea cultivars. These differences could be
partially explained by examining the behaviour of C. acutatum on the leaf surface. It is clear, however, that the distribution of the different species, their aggressrveness on different
Proteaceae and their modes of infection needs to be investigated further. This work provides a
basis for future research on the long-term effective management of these pathogens in fynbos
production. / AFRIKAANSE OPSOMMING: Hierdie tesis bestaan uit vier hoofstukke wat handeloor navorsing van Colletotrichum
siektes van Proteaceae wêreldwyd. Die eerste hoofstuk is 'n oorsig van literatuur rakende die
taksonomie en histologie van die Colletotrichum spesies wat met Proteaceae geassosieer
word. Die literatuur oorsig is nie beperk tot die Proteaceae nie aangesien baie min inligting
rakende Colletotrichum op Proteaceae bestaan.
In die tweede hoofstuk word die Colletotrichum spesies wat met proteas in verskeie dele
van die wêreld geassosieer word, op grond van morfologie, DNS volgorde data van die
interne getranskribeerde spasieerder area ("ITS-I, ITS-2"), die 5.8S geen, en gedeeltelike
DNS volgordes van die B-tubulin geen geïdentifiseer. Vier Colletotrichum spesies is met die
Proteaceae geassosieer. Colletotrichum gloeosporioides is geïsoleer vanaf Protea cynaroides
wat in Suid-Afrika en Zimbabwe gekweek is en vanaf 'n Leucospermum sp. in Portugal, maar
is bekend op verskeie gashere wêreldwyd. 'n Spesie wat onlangs beskryf is, C. boninense, is
met Zimbabwiese en Australiaanse Proteaceae geassosieer, maar kom ook op 'n Eucalyptus
sp. in Suid-Afrika voor. Dit is 'n groot uitbreiding van die geografiese voorkoms en
gasheerreeks van hierdie spesie en 'n beskrywing van die Afrikaanse rasse word gegee.
Colletotrichum crassipes is verteenwoordig deur 'n enkele isolaat wat vanaf 'n Dryandra
plant in Madeira verkry is. Colletotrichum acutatum is vanaf Protea en Leucadendron in
Suid-Afrika asook vanaf ander proteas wat elders voorkom, geïsoleer. Colletotrichum
acutatum f. sp. hakea is vanaf Hakea in Suid-Afrika geïsoleer. In hoofstuk drie is die patogenisiteit van hierdie Colletotrichum spesies teenoor sekere
proteas getoets, die relatiewe aggressiwiteit van die verskillende spesies is vergelyk, asook die
gasheer se reaksie teenoor die spesies en die effek wat verwonding op die gasheer gehad het.
Daar kan afgelei word vanaf die resultate dat C. acutatum en C. gloeosporioides die primêre
patogene is wat met Colletotrichum blaarnekrose geassosieer word, en dat C. acutatum die
hoof oorsaak is van antraknose en lootnekrose van Proteaceae in Suid-Afrika.
'n Histologiese studie is in hoofstuk vier uitgevoer in reaksie op die bevindings van die
vorige hoofstuk. Die gedrag van twee C. acutatum isolate (een vanaf Protea en die ander
vanaf Hakea, C. acutatum f.sp. hakea) op die oppervlaktes van geïnokuleerde Protea blare is
bestudeer deur gebruik te maak van lig- en skandeer-elektronmikroskopie. Colletotrichum
acutatum vanaf Protea vorm gemelaniseerde appressoria op die blaaroppervlak, terwyl C.
acutatum vanaf Hakea klein hoeveelhede van beide gemelaniseerde en ongemelaniseerde
appressoria vorm. Meeste van die appressoria wat deur C. acutatum vanaf Protea gevorm
word, vorm op die aanhegtingspunte tussen selle en op die periklinale wande van die
epidermale selle. Vanuit hierdie studie is dit duidelik dat C. acutatum f. sp. hakea nie 'n
patogeen van Protea is nie. Gevolglik hou die huidige gebruik van hierdie isolaat as
biologiese beheer agent van Hakea in Suid-Afrika geen gevaar in vir inheemse Protea spesies
nie. Colletotrichum acutatum vanaf Protea (alhoewel dit naverwant is aan C. acutatum f. sp.
hakea) is 'n patogeen van Protea en hierdie stelling is ook bevestig deur histologiese
waarnemmgs.
Ter samevatting het hierdie studie getoon dat verskeie Colletotrichum spesies
geassosieer word met siektes van Proteaceae. Hierdie spesies het van mekaar verskil rakende
patogenisiteit en aggressiwiteit nadat hulle op sekere protea kultivars geïnokuleer is. Hierdie verskille kon gedeeltelik verklaar word deur die gedrag van C. acutatum op die
blaaroppervlaktes van verskillende protea kultivars. Dit is duidelik dat die verspreiding van
die verskillende spesies, hulle aggressiwiteit op verskillende Proteaceae en hul infeksie
metodes verder ondersoek moet word. Hierdie studie verskaf 'n basis vir toekomstige
navorsing rakende lang-termyn effektiewe bestuur van hierdie patogene in fynbos
aanplantings.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/53732 |
| Date | 03 1900 |
| Creators | Lubbe, Carolien M. |
| 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 | English |
| Type | Thesis |
| Format | 126 pages : illustrations |
| Rights | Stellenbosch University |
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