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The role of the mediterranean fruit fly, Ceratitis capitata, in Botrytis bunch rot of grapeEngelbrecht, Rene 03 1900 (has links)
Thesis (MScAgric)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Botrytis bunch rot of grape is caused by Botrytis cinerea Pers. :Fr. Conidia of the
pathogen, which is dispersed by wind, water droplets and by insects, can penetrate the intact
grape berry cuticle, but disease expression occurs only under predisposing conditions. Since
relatively high infection rates often occur in vineyards, predisposing factors must play a
fundamental role in primary infection and subsequent disease occurrence. Insects can play a
very important role in this regard by depositing inocula at wound sites during feeding and by
providing fresh wounds during their oviposition and feeding activities. The aim of this study
was (i) to determine the potential of the Mediterranean fruit fly to transfer B. cinerea and
other bunch and fruit rot fungi in natura, (ii) to investigate the transport, deposition and
subsequent disease expression on grape berries in vitro, and (iii) to investigate fruit fly
activities and the nature of deposited conidia and mycelia of B. cinerea by aid of digital
photography and epifluorescence microscopy, respectively.
Two Sensus fruit fly traps containing the para-pheromone, Capilure, were installed in
orchards and five neighboring vineyards on four farms in the Stellenbosch region. Ceratitis
fruit flies were collected weekly, identified and counted to determine the fluctuations in fruit
fly population. Following field collection, the fruit flies were plated on Kerssies' B. cinerea
selective medium and the number of flies yielding the pathogen was recorded. Two fruit fly
species, C. capitata and C. rosa, were captured during the study period. Ceratitis rosa
numbers comprised only 1% of the total number of fruit flies captured. Ceratitis capitata
numbers, and the percentage B. cinerea contaminated flies generally increased after harvest in
the different orchards and vineyards. Following harvest, the percentage flies yielding B.
cinerea was higher in vineyards compared to orchards. Furthermore, in each vineyard an
increase in percentage B. cinerea contaminated fruit flies was preceded by a corresponding
increase in its neighboring orchard. The levels of both Penicillium and Alternaria
contaminated fruit flies stayed high throughout the investigation period, especially after
harvest of the orchard cultivars. Low incidence of Aspergillus, Mucor and Rhizopus spp.
were recorded on C. capitata. These findings suggest that the Mediterranean fruit fly may play an important role in the dispersal of inocula of fungi associated with postharvest decay
from early-maturing stone fruit orchards to mid- and late-maturing wine grape vineyards, and
in disease induction under conditions unfavourable for natural infection.
Three experiments were conducted to determine the potential of fruit flies in provoking B.
cinerea decay. In the first experiment, transport of conidia and disease expression were
investigated on rachis segments bearing unwounded berries only. In the second experiment,
the effect of wounding on disease expression was investigated. In the third experiment, the
effect of inoculum type (mycelia and conidia) on transportation and disease expression was
investigated on rachis segments bearing unwounded berries, and on segments with wounded
berries. The table grape cultivar, Dauphine, and the wine grape cultivar, Shiraz, were used at
véraison, two weeks before harvest and harvest, and the transport studies were conducted in
ethanol-disinfected perspex cages. Disease expression was studied in dry (~56% RH),
ethanol-disinfected perspex chambers incubated at 22°C. The isolations from berries revealed
that the flies deposited, without preference, high amounts of B. cinerea at various positions on
the grape berry's surface. The freezing studies showed that the deposited conidia germinated
and penetrated the berry skin at various positions. However, B. cinerea developed more often
at the pedicel end than on the cheek or style end, which indicated a peculiar interaction
between B. cinerea, the fruit fly and host tissue at this part of the berry. This phenomenon
was substantiated by the finding that B. cinerea also developed more often at the pedicel end
of berries that were not frozen. Further evidence for this interaction was found on intact
berries exposed to flies that carried mycelia after feeding on berries without sporulating
colonies of the pathogen, but showing symptoms of slippery skin. Significantly more decay
developed on wounded berries compared to the unwounded berries and more so at the wound
site. In addition, female fruit flies were responsible for significantly more decay development
than male fruit flies. The study thus proved that the Mediterranean fruit fly can promote B.
cinerea disease development under conditions unfavorable to natural infection.
The activities of the Mediterranean fruit fly, Ceratitis capitata, on grape berries were
monitored by aid of digital photography. In addition, the deposition of conidia and mycelia of
Botrytis cinerea at three sites (pedicel end, cheek and style end) on the grape berry,
germination of the fungal structures after dry (±56% RH) and moist (±93% RH) incubation
and wounds inflicted during ovipositioning were examined with an epifluorescence
microscope. The observations revealed that the fruit fly's activities were generally restricted to the grape berry. They visited the grape berry cheek more often, but visitations to the
pedicel end of berries increased substantially from véraison to harvest, indicating the
possibility of nutrient leakages at this site. Microscopy revealed that the flies deposited
conidia singular, in feeding packages and in faecal excrements on the berry surface. The
conidia in feeding packages were ensheathed by salivical fluids and occurred in clusters of 10
to 50 conidia. An average of 60% of the conidia in feeding packages germinated under dry
conditions (±56% RH). Conidia that passed through the intestinal tract of the fruit fly and that
were deposited in faecal excrements were deformed and low in viability. These conidia did
not occur in cluster format, but were proportionally spread with the faeces on the surface of
the grape berry. Conidia that were deposited singular and in faecal excrements did not
germinate unless incubated under moist conditions (± 93% RH). Wounds inflicted by female
fruit flies during ovipositioning were most frequently observed on the cheek. This
predisposition to B. cinerea infection of grape berries by the activities of fruit flies, suggested
an important role for the flies in the initiation of Botrytis bunch rot epidemics in vineyards. / AFRIKAANSE OPSOMMING: DIE ROL VAN DIE MEDITERREENSE VRUGTEVLIEG, CERATITIS CAPITATA,
IN BOTRYTIS CINEREA TROSVERROTTING VAN DRUIWE
Botrytis-trosverrotting van druiwe word deur Botrytis cinerea Pers. :Fr. veroorsaak.
Konidia van die patogeen wat deur wind, waterdruppels en insekte versprei word, kan die
intakte druiweskil binnedring, maar siekte-uitdrukking vind slegs onder spesiale
omstandighede plaas. Aangesien relatief hoë infeksie vlakke algemeen in wingerde voorkom,
moet predisponerende faktore 'n fundamentele rol in die primêre infeksie, en die daaruit
voortspruitende siektetoestand speel. Insekte kan 'n baie belangrike bydrae lewer deur
inokuia tydens voeding by wonde te deponeer. Nuwe wonde kan ook tydens oviposisionering
en voeding ontstaan. Die doel van hierdie studie was om (i) die potensiaal van die
Mediterreense vrugtevlieg om B. cinerea en ander tros- en vrugverrottingswamme in natura
oor te dra, te bepaal; om (ii) die verspreiding, deponering en daaropvolgende siekteuitdrukking
op druiwekorrels in vitro te ondersoek; en om (iii) die aktiwiteite en aard van die
gedeponeerde konidia en miselia met behulp van digitale fotografie sowel as epifluoressensiemikroskopie
waar te neem.
Twee Sensus-vrugtelokvalle met die paraferomoon, Capilure, IS In vrugteboorde en
aangrensende wingerde in die Stellenbosch-omgewing aangebring. Ceratitis-vrugtevlieë is
weekliks versamel, geïdentifiseer en getel om fluktuasies in die vrugtevliegpopulasie te
bepaal. Na die veldversameling is die vrugtevlieë op Kerssies se B. cinerea-selektiewe
medium uitgeplaat. Gedurende die studie is twee spesies vrugtevlieë, C. capitata en C. rosa,
gevang. Na oesstyd het die aantal Ceratitis-vrugtevlieë en die persentasie vrugtevlieë, besmet
met B. cinerea, in die verskillende boorde en wingerde toegeneem. Na oestyd was die
persentasie vrugtevlieë wat B. cinerea gedra het, hoër in die wingerde as in die boorde. Elke
toename in die persentasie B. cinerea-besmette vrugtevlieë in 'n wingerd is voorafgegaan
deur 'n ooreenkomstige toename in die aangrensende vrugteboord. Die aantal vrugtevlieë
besmet met Penicillium en Alternaria spp. het tydens die navorsingstydperk deurgaans hoog
gebly, veral nadat die vrugteboord-kultivars geoes is. Die voorkoms van Aspergillus-,
Mucor- en Rhizopus spp. op Ceratitis-vrugtevlieë was deurgaans laag. Hierdie bevinding wys
daarop dat vrugtevlieë 'n belangrike rol speel in die verspreiding van swarninokula, wat met na-oes verrotting geassosieer word, van vroegrypwordende steenvrugteboorde na mid- en
laatrypwordende wyndruifwingerde.
Drie eksperimente is in vitro onderneem om vrugtevlieë se potensiaal om B. cinereaverrotting
te veroorsaak te bepaal. In die eerste eksperiment is ragi met slegs ongewonde
korrels gebruik om die oordrag van konidia en siekte-ontwikkeling te ondersoek. In die
tweede eksperiment is die effek van verwonding op siekte-ontwikkeling ondersoek. In die
derde eksperiment is die effek van inokulumtipe (miselia en konidia) op verspreiding en
siekte-ontwikkeling ondersoek deur ragis-segmente met gewonde korrels sowel as ragissegmente
met ongeskonde korrels te gebruik. Die tafeldruif-kultivar Dauphine en die
wyndruif-kultivar Shiraz, by kleurbreuk, twee weke voor oes en by oestyd, is in die
eksperimente gebruik. Die oordragstudies is in etanol-ontsmette perspex-hokke uitgevoer.
Siekte-ontwikkeling is bestudeer in droeë (±56% RH), etanol-ontsmette perspex-kamers en
geinkubeer by 22°C. By ondersoek is gevind dat vlieë, sonder voorkeur, groot hoeveelhede
B. cinerea op verskeie dele op die druiwekorrel-oppervlak deponeer. Bevriesingstudies het
aangetoon dat die gedeponeerde konidia op verskeie dele van die korrelontkiem en die skil
binnedring. Botrytis cinerea het egter meer dikwels by die korrelsteelkant as by die
stempelkant, of op die wang, ontwikkel. Hierdie bevinding het 'n eiesoortige interaksie
tussen B. cinerea, die vrugtevlieg en gasheerweefsel by die korrelsteelkant van die korrel
aangetoon. Die verskynsel is gestaaf deur die bevinding dat B. cinerea ook meer dikwels by
die korrelsteelkant van die korrels wat nie gevries is nie, ontwikkel het. Verdere bewys van
hierdie interaksie is gevind by ongeskonde korrels wat aan die vlieë wat miselia gedra het
blootgestel is. Die siekte het beduidend meer dikwels op gewonde as ongewonde korrels en
verder aansienlik meer dikwels op die wondoppervlakte ontwikkel. Dit was ook duidelik dat
vroulike vrugtevlieë baie meer vir verrotting verantwoordelik was as manlike vrugtevlieë.
Die studie bewys dus dat Mediterreense vrugtevlieë die ontwikkeling van B. cinerea kan
bevorder in omstandighede wat ongunstig is vir natuurlike infeksie.
Die aktiwiteite van die Mediterreense vrugtevlieg C. capitata op die druiwekorrels is met
behulp van digitale fotografie waargeneem. Verder is die deponering van konidia en miselia
van B. cinerea op die verskillende dele (korrelsteelkant, wang en stempelkant) van die korrel,
ontkieming van die swamstrukture na droeë (±56% RH) en nat (±93% RH) inkubasie en
wonde wat tydens oviposisionering veroorsaak is, met epifluoressensie-mikroskopie
ondersoek. Die waarnemings het onthul dat die vrugtevlieg se aktiwiteite gewoonlik tot die druiwekorrel beperk is. Hulle het korrelwange meer dikwels besoek. Besoek aan die
korrelsteelkant het aansienlik toegeneem van kleurbreuk tot oestyd, wat op die moontlikheid
van voedingstof-lekkasie by die deel aandui. Mikroskoopstudies het aangedui dat vlieë
konidia enkel, in voedingspakkies en in fekale uitskeidings op die korreloppervlakte
deponeer. Die konidia in die voedingspakkies is deur speekselvloeistof omhul en het in
groepe van 10 tot 50 konidia voorgekom. Gemiddeld 60% van die konidia in
voedingspakkies het in droeë omstandighede (±56% RH) ontkiem. Konidia wat deur die
spysverteringskanaal van die vrugtevlieg gegaan het en in die fekale ekskresie gedeponeer is,
was misvorm en het lae lewensvatbaarheid gehad. Laasgenoemde konidia was nie in groepe
gedeponeer nie, maar is proporsioneel met die feces op die oppervlak van die druiwekorrel
versprei. Konidia wat enkel en in feces gedeponeer is, het nie ontkiem nie, tensy toestande
vogtig (±56% RH) was. Wonde wat deur die vroulike vrugtevlieë tydens oviposisionering
veroorsaak is, is meer dikwels op die wang van die korrelopgemerk. Hierdie predisposisie
van druiwekorrels tot B. cinerea-infeksie, meegebring deur die aktiwiteit van die vrugtevlieg,
dui daarop dat die rol wat die vrugtevlieg in die inisiëring van Botrytis trosverrottingepidemies
in wingerde speel, van beduidende belang is.
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Diversity and dispersal of the ophiostomatoid fungus, Knoxdaviesia proteae, within Protea repens infructescencesAylward, Janneke 04 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Two genera of ophiostomatoid fungi occur in the seed-bearing structures of serotinous
Protea species in the Cape Floristic Region. These fungi are dispersed by arthropods,
including mites and beetles that visit the Protea host plants. Although the vectors of Proteaassociated
ophiostomatoid fungi are known, their dispersal patterns remain unknown –
especially the manner in which recently burnt fynbos vegetation is recolonized. Additionally,
their reproduction strategy has not previously been investigated. The focus of this study was,
therefore, to determine the extent of within- and between-plant dispersal of Proteaassociated
ophiostomatoid fungi at the population level and to investigate their reproductive
strategy. One Protea-associated ophiostomatoid fungus, Knoxdaviesia proteae, is found
exclusively in the fruiting structures of P. repens and was the focus of this study. In order to
interrogate natural populations of this fungus, 12 polymorphic microsatellite markers
specific to K. proteae were developed with an ISSR-PCR enrichment strategy and
pyrosequencing. These markers were amplified in two distantly separated populations of K.
proteae. The genetic and genotypic diversities of both populations were exceptionally high
and neither showed significant population differentiation. The lack of population structure in
both populations implies that K. proteae individuals within a P. repens stand are in
panmixia. As one of the sampling sites had burnt recently, the process whereby young
fynbos is recolonized could be investigated. Compared to the adjacent, unburnt area, K.
proteae individuals in the burnt area of this population had significantly less private alleles,
suggestive of a young population that had experienced a genetic bottleneck. Knoxdaviesia
proteae individuals that did not originate from the adjacent unburnt area were encountered
within the burnt site and, additionally, isolation-by-distance could not be detected. The
parsimony-based haplotype networks and the tests for linkage disequilibrium indicated that
recombination is taking place within as well as between the two distantly separated
populations. The observed panmixia in P. repens stands, widespread recolonization and the high genetic similarity and number of migrants between the two populations emphasizes
long-distance dispersal and therefore the role of beetles in the movement of K. proteae. This
cohesive genetic structure and connection across large distances is likely a result of multiple
migration events facilitated by beetles carrying numerous phoretic mites. / AFRIKAANSE OPSOMMING: Twee genera ophiostomatoid swamme kom in die saad-draende strukture van bloeiende
Protea spesies in the Kaapse Floristiese Streek voor. Hierdie Protea-verwante
ophiostomatoid swamme word gekenmerk deur hul assosiasie met geleedpotige vektore –
spesifiek die myt en kewer besoekers van die Protea gasheer plante. Alhoewel die
geleedpotige vektore van Protea-verwante ophiostomatoid swamme bekend is, is die wyse
waarop hierdie swamme versprei onbekend; veral die manier waarop onlangse gebrande
fynbos geherkoloniseer word. Verder is die voortplantings-strategie van hierdie swamme
nog nie voorheen ondersoek nie. Die fokus van hierdie studie was dus om die omvang van
binne- en tussen-plant verspreiding van Protea-verwante ophiostomatoid swamme te bepaal
op die populasie vlak en om hul voorplantings-strategie te ondersoek. Een Protea-verwante
ophiostomatoid swam, Knoxdaviesia proteae, word uitsluitlik in die vrugdraende strukture
van P. repens aangetref en was die fokus van hierdie studie. Om natuurlike populasies van
hierdie swam te ondersoek is 12 mikrosatelliet-merkers spesifiek vir K. proteae ontwerp
deur ‘n ISSR-PCR strategie en “pyro”-basisvolgorde bepaling te gebruik. Hierdie merkers is
geamplifiseer in twee K. proteae populasies wat ver van mekaar geskei is. Die genetiese en
genotipiese diversiteit van beide populasies was uitsonderlik hoog en nie een het beduidende
populasie-differensiasie getoon nie. Die gebrek aan populasie struktuur in beide populasies
veronderstel dat K. proteae individue binne ‘n P. repens stand in panmiksia is. Aangesien
een van die steekproef terreine onlangs gebrand het, kon die herkolonisasie proses van jong
fynbos ondersoek word. In vergelyking met die aangrensende, ongebrande area, het K.
proteae individue in die gebrande area beduidend minder private allele gehad. Dit dui op ‘n
jong populasie wat ‘n genetiese bottelnek beleef het. Knoxdaviesia proteae individue wat nie
van die aangrensende, ongebrande area afkomstig is nie is ook binne die gebrande terrein
aangetref. Verder is afsondering-deur-afstand nie aangetref nie. Die parsimonie-gebaseerde haplotiepe-netwerke en die toetse vir koppeling-onewewigtigheid het aangedui dat
rekombinasie binne sowel as tussen die twee populasies plaasvind. Die panmiksia wat
waargeneem is in P. repens populasies, wydverspreide herkolonisasie en die hoë genetiese
ooreenkoms en hoeveelheid immigrante tussen die twee populasies beklemtoon lang afstand
verspreiding en dus die rol van kewers in die beweging van K. proteae. Hierdie
samehangende genetiese struktuur en die verband oor groot afstande is waarskynlik ‘n
gevolg van verskeie migrasies gefasiliteer deur kewers wat talle foretiese myte dra.
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Isolation and characterisation of a polygalacturonase-inhibiting protein (PGIP) and its encoding gene from Vitis vinifera L.De Ascensao, Ana 12 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: Polygalacturonase-inhibiting proteins (PGIPs) are present in the cell walls of a variety
of plant species. These proteins have been shown to specifically inhibit
endopolygalacturonases (endo-PGs) secreted by invading fungal pathogens as part
of the induced disease resistance mechanism of plants. This is the first report on the
isolation and characterisation of a pgip gene from Vitis vinifera L., designated
grapevine pgip1. A single open reading frame encoding a deduced polypeptide of
333 amino acids with a predicted molecular mass of 37.1 kOa and a calculated
isoelectric point of 8.61 was identified from a 5.6 kb subgenomic fragment of
V. vinifera cv Pinotage. Nucleotide and derived amino acid sequence analysis of
grapevine pgip1 showed significant homology with other characterised PGIP
encoding genes and revealed features characteristic of PGIPs found in several other
plant families. Genomic DNA analysis showed that grapevine pgip1 belongs to a
small multigene family in Vitis cultivars. From Northern blot analysis it was evident
that expression of the PGIP family is both tissue- and developmental stage specific.
The grapevine pgip1 was transiently expressed in Nicotiana benthamiana L. with
potato virus X (PVX) as a vector. Grapevine PGIP1 isolated from crude protein
extracts of PVX-infected N. benthamiana were tested and showed inhibitory activity
against polygalacturonases (PGs) from Botrytis cinerea.
Grapevine PGIPs have not previously been purified and characterised. Molecular
analyses have confirmed that PGIPs are typically encoded by multigene families and
that the inhibitor specificities and kinetics of the isolated proteins differ within and
among species. In this study, two PGIP isomers from V. vinifera berries were
isolated. The one isomer, designated PGIP-A, was partially purified and had a
molecular mass of 39 kOa, whereas the other PGIP, designated PGIP-B, was
purified and had a molecular mass of 42 kOa as determined by sodium dodecyl
sulphate-polyacrylamide gel electrophoresis (SOS-PAGE) and Western blot analysis.
Both proteins were cell wall-bound. Enzymatic deglycosylation confirmed that PGIP-B
is a glycosylated protein. Grapevine PGIP-A showed strong inhibitory activity against
a homogeneous PG from Aspergillus niger and to a lesser extent against PG from
Fusarium moniliforme, but was unable to interact with a crude PG preparation from
B. cinerea. Grapevine PGIP-B was able to strongly inhibit PGs from B. cinerea as
well as from Colletotrichum gleosporoides, yet showed no inhibition towards PG from
A. niger.
The grapevine pgip1 gene was expressed under the control of the Cauliflower
mosaic virus (CaMV) 35S promoter in tobacco plants via Agrobacterium tumefaciensmediated
transformation. Transgenic tobacco plants expressing the grapevine PGIP
(gPGIP1) were used to demonstrate the effectiveness of this inhibitor against fungal
PGs and to investigate whether gPGIP1 influences disease development. Northern
blot analysis identified 19 transgenic plants expressing pgip1 transcript levels. Crude PGIP extracts from the transgenic tobacco plants inhibited PGs from B. cinerea and
C. gleosporoides, but not PG from A. niger. Leaves from untransformed tobacco
plants, from transgenic tobacco lines showing high and low PG inhibition, and from
transgenic plants that did not express pgip1, were inoculated with B. cinerea.
Transgenic leaves showed a reduction in the size of necrotic lesions of macerated
tissues of approximately 45% relative to control and non-expressing transgenic
leaves. The results from the heterologous expression of gPGIP1, together with the
results from the protein purifications and inhibition studies, indicate that the isolated
grapevine pgip1 gene encodes the isolated PGIP-B isomer. This work has
; established a good model system to study certain aspects of plant-pathogen
interactions in grapevine. Heterologous expression of gPGIP1 has demonstrated that
PGIP inhibition of fungal PGs slows disease development of B. cinerea in planta. / AFRIKAANSE OPSOMMING:
Sien volteks vir opsomming
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Characterisation of Cylindrocarpon spp. associated with black foot disease of grapevineHalleen, Francois 12 1900 (has links)
Dissertation (PhD (Agric))--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: During the past few years a drastic reduction has been noted in the survival rate of
grafted grapevines in nurseries, as well as in young vineyards in the Western Cape Province of
South Africa. Circumstantial evidence suggested that Cylindrocarpon spp., which cause black
foot disease of grapevine, were associated with this decline. Black foot disease of grapevine is a
relatively new, and as yet poorly known disease affecting vines in various countries where
grapevines are cultivated. Primary aims of this research have been (1) to conduct nursery
surveys in order to determine which fungi are involved in the decline phenomenon, with special
reference to the involvement of Cylindrocarpon spp., (2) to identify and characterise the
organisms believed to be the causal organisms of black foot disease, and (3) the development of
control and/or management strategies to prevent or eradicate Cylindrocarpon infections.
Nursery grapevines were sampled at different stages from three commercial nurseries in
the Wellington area of the Western Cape Province and were investigated during the 19992000
season by means of destructive sampling. The first samples were taken in September from
callused cuttings prior to planting in nurseries. After planting, asymptomatic rooted cuttings
were selected from nurseries after 3, 6 and 9 months. Isolation studies clearly demonstrated that
different “Cylindrocarpon spp.” infected cuttings from nursery soils. These species rarely
occurred in rootstock propagation material prior to planting. At the time of planting, the
susceptible basal ends (especially the pith area) of most of the nursery cuttings are partly or even
fully exposed. Callus roots also break during the planting process, resulting in small wounds
susceptible to infection by soilborne pathogens. The isolation studies revealed that the first
infections occurred in the roots, followed by infections of the rootstocks. These infections
increased progressively during the course of the growing season.
Substantial variation in cultural and morphological characters was observed among the
Cylindrocarpon isolates obtained from the nursery survey, as well as from isolations that were
made from diseased grapevines. Morphological and phylogenetic studies were conducted to
identify these “Cylindrocarpon spp.” and to establish their association with black foot disease.
Sequences of the partial nuclear large subunit ribosomal DNA (LSU rDNA), internal transcribed spacers 1 and 2 of the rDNA including the 5.8S rDNA gene (ITS), and partial β-tubulin gene
introns and exons were used for phylogenetic inference. Phylogenetic analyses confirmed the
diversity observed among the isolates and four Cylindrocarpon-like species were identified.
One of these species was initially identified as Cylindrocarpon destructans. However, further
research revealed C. destructans to represent a species complex. Grapevine isolates of “C.
destructans” proved to be identical to the ex-type strain of Cylindrocarpon liriodendri, which
also produced a teleomorph, Neonectria liriodendri in culture. A second species was newly
described in this study as Cylindrocarpon macrodidymum (Neonectria macrodidyma). The two
remaining Cylindrocarpon-like species were placed in a new genus, Campylocarpon. The two
species were named Campylocarpon fasciculare and Campylocarpon pseudofasciculare.
Pathogenicity studies confirmed that all four species were able to reduce root and shoot mass
significantly.
Knowledge obtained pertaining to the disease cycle of black foot disease suggest that suitable
management strategies should focus on prevention of primary infection in nurseries. However,
at present, no fungicides are registered for control of this disease in South African vineyards or
nurseries. Thirteen fungicides were screened in vitro for mycelial inhibition of these pathogens.
Prochloraz manganese chloride, benomyl, flusilazole and imazalil were the most effective
fungicides tested, and were subsequently included in semi-commercial field trials. Basal ends of
grafted cuttings were dipped (1 min) in various chemical and biological treatments prior to
planting in open-rooted nurseries. Black foot pathogens were not isolated from grafted cuttings
prior to planting in nurseries. Additional treatments involved soil amendments with
Trichoderma formulations and hot water treatment (50°C for 30 min) of dormant nursery
grapevines. Field trials were evaluated after a growing season of eight months. The incidence of
black foot pathogens was not significantly and/or consistently reduced by the majority of
chemical or biological treatments. However, these pathogens were not isolated from uprooted
plants that were subjected to hot water treatment. It is therefore recommended that hot water
treatment of dormant nursery plants be included in an integrated strategy for the proactive
management of black foot disease in grapevine nurseries. / AFRIKAANSE OPSOMMING: Gedurende die afgelope paar jaar is ‘n drastiese afname waargeneem in die sukses van
geënte wingerdplante in kwekerye, sowel as jong wingerde van die Wes-Kaap.
Omstandigheidsgetuienis dui daarop dat Cylindrocarpon spp., wat die wingerdsiekte swartvoet
veroorsaak, geassosieer word met hierdie agteruitgang. Swartvoet is ‘n relatiewe nuwe siekte
waarvan daar baie min inligting bekend is, alhoewel dit voorkom in verskeie lande waar wingerd
verbou word. Die primêre doel van navorsing was (1) om opnames in wingerdkwekerye uit voer
om te bepaal watter swamme betrokke is by die verskynsel van agteruitgang, met spesiale
verwysing na die betrokkenheid van Cylindrocarpon spp., (2) om die organismes te identifiseer
en te karakteriseer wat daarvan verdink word dat hulle die siekte swartvoet veroorsaak, en (3)
om beheer en/of bestuurspraktyke te ontwikkel om Cylindrocarpon infeksies te voorkom of uit
te wis.
Kwekeryplantjies in drie kommersiële kwekerye in die Wellington omgewing van die
Wes-Kaap is gedurende verskillende tye gedurende die groeiseisoen gemonitor. Die opnames
het plaasgevind gedurende die 19992000 seisoen deur middel van destruktiewe
monsterneming. Die eerste monsters is geneem in September nadat die stokkies geënt en
gekallus is en voordat dit in die kwekery geplant is. Na plant is asimptomatiese, gewortelde
plante vanuit die kwekerye na 3, 6 en 9 maande uitgehaal. Isolasiestudies dui duidelik daarop
dat verskillende “Cylindrocarpon spp.” plante vanuit die kwekerygrond geïnfekteer het. Hierdie
spesies het selde voorgekom in onderstok-voortplantingsmateriaal voor plant. Tydens plant is
die vatbare basale gedeelte, veral die pit, van die meeste geënte stokkies gedeeltelik of selfs
volledig blootgestel. Kalluswortels breek ook tydens plant wat wonde laat vir infeksie deur
grondgedraagde siektes. Die isolasiestudies dui ook daarop dat die eerste infeksies in die wortels
plaasgevind het, gevolg deur infeksies van die onderstokke. Hierdie infeksies het toenemend
voorgekom gedurende die verloop van die groeiseisoen.
Substansiële variasie in kultuur- en morfologiese eienskappe is waargeneem in die
Cylindrocarpon isolate wat tydens die kwekeryopnames versamel is, sowel as van isolasies wat
gemaak is uit siek plante. Morfologiese en filogenetiese studies is uitgevoer om hierdie “Cylindrocarpon spp.” te identifiseer en hul betrokkenheid by die siekte swartvoet uit te klaar.
Gedeeltelike DNS volgordes van die groot ribosomale subeenheid (“LSU rDNA”), interne
getranskribeerde spasiëerderarea (“ITS1, “ITS2”), insluitend die 5.8S rRNS geen, en
gedeeltelike β-tubilien geen introns and eksons is gebruik vir filogenetiese analise.
Filogenetiese analises het die diversiteit wat waargeneem is tussen die verskillende isolate
bevestig deurdat vier Cylindrocarpon-agtige spesies geïdentifiseer is. Een van hierdie spesies is
aanvanklik geïdentifiseer as Cylindrocarpon destructans. Verdere navorsing het egter daarop
gedui dat C. destructans ‘n spesie-kompleks verteenwoordig. “C. destructans” afkomstig van
wingerd blyk identies te wees aan die ex-tipe isolaat van Cylindrocarpon liriodendri, wat ook ’n
teleomorf, Neonectria liriodendri in kultuur vorm. ’n Tweede spesie is nuut beskryf in hierdie
studie as Cylindrocarpon macrodidymum (Neonectria macrodidyma). Die twee oorblywende
Cylindrocarpon-agtige spesies is geplaas in ‘n nuwe genus, Campylocarpon. Die twee spesies
staan bekend as Campylocarpon fasciculare en Campylocarpon pseudofasciculare.
Patogenisiteitstudies het bevestig dat al vier spesies die vermoë het om wortel- en lootmassa van
wingerdplant drasties te verlaag.
Kennis wat opgedoen is rakende die lewensiklus van swartvoet dui daarop dat
bestuurspraktyke daarop moet fokus om primêre infeksies in wingerdkwekerye te voorkom. Op
die oomblik is daar egter geen fungisiedes geregistreer vir die beheer van die siekte in Suid-
Afrikaanse wingerde of kwekerye nie. Dertien fungisiedes is in vitro geëvalueer om te bepaal of
dit miseliumgroei van hierdie swamme kan inhibeer. Prochloraz mangaan chloried, benomyl,
flusilasool en imazalil was die effektiefste fungisiedes wat ondersoek is, en is gevolglik ingesluit
in semi-kommersiële veldproewe. Die basale gedeelte van geënte stokkies is gedoop (1 min) in
verskeie chemies en biologiese behandelings voordat dit geplant is in die kwekerye. Patogene
wat geassosieer word met swartvoet is nie vanuit geënte stokkies geïsoleer voordat dit in die
kwekerye geplant is nie. Addisionele behandelings het bestaan uit grondtoevoegings met
Trichoderma formulasies, sowel as warmwaterbehandeling (50°C vir 30 min) van dormante
kwekeryplante. Die veldproewe is geëvalueer na ‘n groeiseisoen van 8 maande. Die voorkoms
van swartvoet patogene is nie betekenisvol/konstant verlaag deur die meeste chemies en
biologiese behandelings nie. Hierdie patogene is egter nie vanuit plante geïsoleer wat na uithaal
aan warmwaterbehandeling blootgestel is nie. Dit word dus aanbeveel dat
warmwaterbehandeling van dormante kwekeryplante deel word van ‘n geïntegreerde strategie vir
die pro-aktiewe beheer van swartvoet in wingerdkwekerye.
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Botryosphaeria diseases of proteaceaeDenman, Sandra 03 1900 (has links)
Dissertation (PhD (Agric))--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Fungi belonging to the genus Botryosphaeria are heterotrophic micromycetes that can be
pathogens on woody plants. They cause serious, and in some cases devastating losses to
crops through leaf necrosis, stem cankers and plant death. The Proteaceae cut-flower
industry in South Africa accounts for 70% of the national cut-flower enterprise.
Botryosphaeria diseases are a major impediment to production and trade of Proteaceae
and there is an urgent need to investigate the etiology, epidemiology and control of these
diseases. Losses of one of the most important proteas, P. magnifica, amount to 50% or
more, locally. The main aims of this study were therefore to establish the etiology and
aspects of epidemiology of Botryosphaeria stem cankers on P. magnifica and other
Proteaceae, and to investigate methods of disease control.
Although there is a vast body of information pertaining to this fungus, which was
reviewed in Chapter 1, there is relatively little information available on Botryosphaeria
on Proteaceae. The taxonomy of Botryosphaeria requires thorough review, and
molecular techniques need to be employed to resolve species identities.
In Chapter 2, it was found that Phyllachora proteae, a leaf pathogen of proteas,
produced a Fusicoccum anamorph, which is described as F. proteae. A sphaeropsis-like
synanamorph was associated with F. proteae and a new combination for P. proteae is
proposed in Botryosphaeria, as B. proteae.
The taxonomy of Botryosphaeria is in disarray at both the generic and the specific
level. In Chapter 3 the taxonomic history of Botryosphaeria is reviewed, and the genus
circumscribed and distinguished from other morphologically similar genera. Although
several anamorph genera have been linked to Botryosphaeria, based on morphological
observations and phylogenetic analysis of lTS rDNA sequence data, two anamorph
genera are now recognised, those with pigmented conidia (Diplodia), and those with
hyaline conidia (Fusicoccum). Botryosphaeria proteae should thus be excluded from
Botryosphaeria.
Several pathogenic Botryosphaeria spp. have an endophytic phase within their
hosts. They are therefore imported unwittingly into other countries where they may pose
a risk to agriculture and indigenous vegetation. The current global distribution of Botryosphaeria spp. associated with Proteaceae is clarified and a key to these taxa
associated with Proteaceae is provided in Chapter 4. Five Botryosphaeria spp. are
associated with cut-flower Proteaceae worldwide viz. B. lute a, B. obtusa, B. protearum,
B. proteae and B. rib is. B. protearum is described as a new species.
A thorough understanding of disease epidemiology is essential to effect a
reduction of losses. In Chapter 5, I show that on P. magnifica, lesions caused by
Botryosphaeria protearum, which lead to the formation of stem cankers, are initiated in
the mid-rib vein or margin of leaves. Koch's postulates were satisfied and it was found
that the number of lesions that developed from artificial inoculations correlated with
starch levels present in leaves at the time of inoculation.
In Chapter 6 it is shown that B. protearum exists as an endophyte in leaves of P.
magnifica in naturally occurring as well as cultivated plants. In natural stands of proteas
stem cankers are rare, but in cultivated plantations the incidence is high. Nutritional
analyses indicate that higher levels of nitrogen occur in leaves of cultivated plants in
spring, which could enhance disease development. High levels of sodium in the leaves of
wild plants may restrict disease development.
The severe economic losses caused by B. protearum make the search for
improved methods of disease control essential. Fungicide applications form an important
component of an integrated approach to disease management. In Chapter 7, in vitro tests
demonstrate that tebuconazole, benomyl, prochloraz me, iprodione and fenarimol reduce
the mycelial growth of B. protearum effectively. In the field there was a 25-85%
reduction in the occurrence of stem cankers by applying fungicides or sanitation pruning.
The best control was achieved by using benomyl, bitertanol, fenarimol, iprodione,
prochloraz manganese chloride alternated with mancozeb and tebuconazole
prophylactically. If sanitation pruning is combined with regular applications of
fungicides, disease can be combated. / AFRIKAANSE OPSOMMING: Mikrofungi wat tot die genus Botryosphaeria behoort, is heterotrofiese organismes, wat
patogenies op houtagtige plante kan wees. Hulle veroorsaak ernstige, en in sommige
gevalle, verwoestende verliese, deur blaarnekrose, stamkankers en plantafsterwing. Die
Proteaceae snyblom-industrie in Suid-Afrika maak 70% van die nasionale snyblomindustrie
uit. Botryosphaeria siektes is 'n belangrike struikelblok in die produksie en
handeldryf van Proteaceae, en daar is 'n ernstige behoefte om die etiologie,
epidemiologie en beheer van siektes te ondersoek. Verliese van een van die belangrikste
proteas, P. magnifica, beloop plaaslik 50% of meer. Die hoof doelstellings van hierdie
studie was dus om die etiologie en epidemiologie van Botryosphaeria stamkankers op P.
magnifica en ander Proteaceae vas te stel en metodes van siektebeheer te ondersoek.
Hoewel daar 'n wye hoeveelheid inligting rakende die swam bestaan, wat in
Hoofstuk I hersien is, is daar relatief min inligting oor Botryosphaeria op Proteaceae
beskikbaar. Die taksonomie van Botryosphaeria benodig deeglike hersiening, en
molekulêre tegnieke word benodig om spesie-identiteite op te klaar.
In Hoofstuk 2 is gevind dat Phyllachora proteae, 'n blaarpatogeen van proteas, 'n
Fusicoccum anamorf produseer, wat as F. proteae beskryf word. 'n Sphaeropsis-agtige
synanamorf is met F. proteae geassosieer en 'n nuwe kombinasie vir P. proteae is as B.
proteae in Botryosphaeria voorgestel.
Die taksonomie van Botryosphaeria is, beide op die genus- as die spesievlak, in
wanorde. In Hoofstuk 3 word die taksonomiese geskiedenis van Botryosphaeria hersien,
en die genus word omskryf en van ander morfologies soortgelyke genera onderskei.
Hoewel verskeie anamorf genera al met Botryosphaeria op grond van morfologiese
waarnemings en filogenetiese analise van ITS rDNA volgorde data verbind is, word twee
anamorf genera nou herken, dié met gepigmenteerde konidia (Diplodia), en dié met
deurskynende konidia (Fusicoccum). Botryosphaeria proteae moet dus van
Botryosphaeria uitgesluit word.
Verskeie patogeniese Botryosphaeria spp. het 'n endofitiese fase in hul
lewenssiklus. Hulle word dus onwetend in ander lande ingevoer waar hulle 'n gevaar vir
landbou en inheemse plantegroei kan inhou. Die huidige wêreldverspreiding van Botryosphaeria spp. wat met Proteaceae geassosieer word is opgeklaar, en in Hoofstuk 4
word 'n sleutel tot die taksa wat met Proteaceae geassosieer word verskaf. Vyf
Botryosphaeria spp. word met snyblom Proteaceae wêreldwyd geassosieer, naamlik B.
lutea, B. protearum, B. proteae, B. ribis en B. obtusa. B. protearum word as 'n nuwe
spesie beskryf.
'n Deeglike kennis van siekte-epidemiologie is noodsaaklik ten einde verliese te
verminder. In Hoofstuk 5 dui ek aan dat letsels wat lei tot stamkankers, veroorsaak deur
Botryosphaeria protearum op P. magnifica, in die hoofnerf of rant van blare ontstaan.
Koch se postulate is uitgevoer en daar is vasgestel dat die aantal letsels wat vanuit
kunsmatige inokulasies ontwikkel het korreleer met die styselvlakke teenwoordig in die
blare ten tye van die inokulasie.
In Hoofstuk 6 word getoon dat B. protearum as 'n endofiet in die blare van P.
magnifica. In natuurlike standplase van proteas is stamkankers skaars, maar in verboude
plantasies is die voorkoms hoog. Voedingsanalises dui aan dat hoër vlakke van stikstof
in die blare van verboude plante in die lente voorkom, wat siekte-ontwikkeling moontlik
kan bevorder. Hoë vlakke van natrium in die blare van natuurlike plante mag siekteontwikkeling
beperk.
Die ernstige ekonomiese verliese wat deur B. protearum veroorsaak word, maak
die soektog na verbeterde metodes van siektebeheer noodsaaklik. Fungisiedtoedienings
maak 'n belangrike deel uit van 'n geïntegreerde benadering tot siektebeheer. In
Hoofstuk 7 dui in vitro toetse aan dat tebuconazole, benomyl, prochloraz me, iprodione
en fenarimol die miseliumgroei van B. protearum effektief verminder. 'n Vermindering
van 25-85% is aangetoon in die voorkoms van stamkankers in die veld, deur die
toediening van fungisiedes en sanitasiesnoei. Die beste beheer is verkry deur die
voorkomende toediening van benomyl, bitertanol, fenarimol, iprodione en prochloraz
manganese chloride, afgewissel met mancozeb en tebuconazole, op plante in die veld.
Indien sanitasiesnoei met gereelde toedienings van fungisiedes gekombineer word, kan
die siekte bekamp word.
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THE USE OF PROPICONAZOL (TILT CGA 64250) FOR CONTROL OF PHYMATOTRICHUM OMNIVORUM IN PEACHES (PRUNUS PERSICA L. BATCH) AND GRAPES (VITIS VINIFERA).Juarez Gonzalez, Rogelio Ausencio. January 1983 (has links)
No description available.
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Modelling long-distance airborne dispersal of fungal spores and its role in continental scale plant disease epidemicsCox, James Alexander January 2015 (has links)
No description available.
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Analysis of genes differentially expressed in Fuerte avocado fruit in response to Colletotrichum gloeosporioides infectionTchatchou, Arnaud Thierry Djami 01 February 2013 (has links)
The anthracnose pathogen, Colletotrichum gloeosporioides (Penz.) Penz. & Sacc., is a
major cause of disease in the avocado industry, causing significant economic losses, and
infects all cultivars. In South Africa, Fuerte and Hass varieties are the most widely grown.
Identification of genes differentially expressed in avocado during infection with the fungus
represents an important step towards understanding the plant’s defence responses and
would assist in designing appropriate intervention strategies. In this study, 454 sequencing
and analysis of the transcriptome of infected Fuerte avocado fruits were performed using
the Roche 454 GS FLX Titanium platform. cDNA libraries enriched for differentially
expressed genes were constructed from unharvested and harvested avocado fruit tissues
collected after 1, 4 and 24 h post-infection and after 3, 4, 5 and 7 day post-infection, then
sequenced.The expression profiles of the genes expressed were measured by a hierarchical
clustering algorithm.Subsequently, quantitative real-time PCR was employed to measure
the expression of some candidate resistance genes to anthracnose disease and to validate
the sequencing results. The single sequencing run produced 215 781 reads from the
transcriptome. A total of 70.6 MB of sequence data was generated and subjected to BLAST
searches of which about 1500 genes encoding proteins predicted to function in signal
transduction, transcriptional control, metabolism, defence, stress response, transportation
processes and some genes with unknown functions were identified. The expression profiles
studies showed that many expressed genes were either up or down regulated after infection
in avocado fruits when compared to the uninfected sample. Salicylic acid and ethylene
were identified to be involved in the signalling networks activated in avocado fruit during
C. gloeosporioides infection. This study showed that avocado is able to respond to C.
gloeosporioides infection by exhibiting a sophisticated molecular system for pathogen
recognition and by activating structural and biochemical defence mechanisms.
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Antifungal and antimycotoxigenic activities of four weedy plant extracts against selected mycotoxigenic fungiThembo, Kaizer Mokemane January 2012 (has links)
Thesis (Ph.D. (Medical Science)) -- University of Limpopo, 2012
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Lettuce stunt : effect of Pythium populations and interactions between Pythium tracheiphilum and nematodesGracia, Javier January 1989 (has links)
No description available.
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