Thesis (MScAgric)--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: Phaeomoniella chlamydospora, Eutypa lata, Phomopsis, Phaeoacremonium, and
Botryosphaeria spp. are important trunk disease pathogens that cause premature decline and
dieback of grapevine. Previous research has focused primarily on wine grapes and the incidence
and symptomatology of these pathogens on table grapes were largely unknown. A survey was
therefore conducted to determine the status and distribution of these pathogens and associated
symptoms in climatically diverse table grape growing regions. Fifteen farms were identified in
the winter rainfall (De Doorns, Paarl and Trawal) and summer rainfall (Upington and
Groblersdal) areas. Samples were taken in July and August 2004 from Dan-ben-Hannah
vineyards that were 8 years and older. Distal ends of arms were removed from 20 randomly
selected plants in each vineyard. These sections were dissected and isolations were made from
each of the various symptom types observed: brown or black vascular streaking, brown internal
necrosis, wedge-shaped necrosis, watery necrosis, esca-like brown and yellow soft wood rot, as
well as asymptomatic wood. Fungal isolates were identified using molecular and morphological
techniques. Pa. chlamydospora was most frequently isolated (46.0%), followed by
Phaeoacremonium aleophilum (10.0%), Phomopsis viticola (3.0%), Botryosphaeria obtusa
(3.0%), B. rhodina (2.2%), B. parva (2.0%), Fusicoccum vitifusiforme (0.6%), B. australis, B.
dothidea and an undescribed Diplodia sp. (0.2% each), while E. lata was not found. Most of
these pathogens were isolated from a variety of symptom types, indicating that disease diagnosis
can not be based on symptomatology alone. Pa. chlamydospora was isolated from all areas
sampled, although most frequently from the winter rainfall region. Pm. aleophilum was found
predominantly in Paarl, while P. viticola only occurred in this area. Although B. obtusa was not
isolated from samples taken in De Doorns and Groblersdal, it was the most commonly isolated
Botryosphaeria sp., being isolated from Upington, Paarl and Trawal. B. rhodina occurred only
in Groblersdal and B. parva in Paarl, Trawal and Groblersdal, while B. australis was isolated
from Paarl only. The rest of the isolates (33%) consisted of sterile cultures, Exochalara,
Cephalosporium, Wangiella, Scytalidium, Penicillium spp. and two unidentified basidiomycetes,
which were isolated from five samples with yellow esca-like symptoms from the Paarl area. These findings clearly illustrate that grapevine trunk diseases are caused by a complex of fungal
pathogens, which has serious implications for disease diagnosis and management.
Protection of wounds against infection by any of these trunk disease pathogens is the
most efficient and cost-effective means to prevent grapevine trunk diseases. However, previous
research on the effectiveness of chemical pruning wound protectants has mostly focused on the
control of Eutypa dieback only. Fungicide sensitivity studies have been conducted for Pa.
chlamydospora, P. viticola and Eutypa lata, but no such studies have been conducted for the
pathogenic Botryosphaeria species from grapevine in South Africa. Ten fungicides were
therefore tested in vitro for their efficacy on mycelial inhibition of the four most common and/or
pathogenic Botryosphaeria species in South Africa, B. australis, B. obtusa, B. parva and B.
rhodina. Iprodione, pyrimethanil, copper ammonium acetate, kresoxim-methyl and boscalid
were ineffective in inhibiting the mycelial growth at the highest concentration tested (5 μg/ml;
20 μg/ml for copper ammonium acetate). Benomyl, tebuconazole, prochloraz manganese
chloride and flusilazole were the most effective fungicides with EC50 values for the different
species ranging from 0.36-0.55, 0.07-0.17, 0.07-1.15 and 0.04-0.36 μg/ml, respectively. These
fungicides, except prochloraz manganese chloride, are registered on grapes in South Africa and
were also reported to be effective against Pa. chlamydospora, P. viticola and E. lata. Results
from bioassays on 1-year-old Chenin Blanc grapevine shoots indicated that benomyl,
tebuconazole and prochloraz manganese chloride were most effective in limiting lesion length in
pruning wounds that were inoculated with the Botryosphaeria spp after fungicide treatment. The
bioassay findings were, however, inconclusive due to low and varied re-isolation data of the
inoculated lesions. Benomyl, tebuconazole, prochloraz manganese chloride and flusilazole can
nonetheless be identified as fungicides to be evaluated as pruning wound protectants in
additional bioassays and vineyard trials against Botryosphaeria spp. as well as the other
grapevine trunk disease pathogens. / AFRIKAANSE OPSOMMING: Phaeomoniella chlamydospora, Eutypa lata, Phomopsis, Phaeoacremonium, en
Botryosphaeria spesies is die mees belangrikste stamsiekte patogene wat agteruitgang en vroeë
terugsterwing van wingerd veroorsaak. Voorafgaande navorsing het hoofsaaklik gefokus op
wyndruiwe en die voorkoms en simptomatologie van hierdie patogene op tafeldruiwe is dus
grootliks onbekend. ‘n Opname is gevolglik gedoen in verskillende klimaaatsareas waar
tafeldruiwe verbou word om die voorkoms en verspreiding, asook die simptome geassosieer met
hierdie patogene, te bepaal. Vyftien plase is geïdentifiseer in die winter- (De Doorns, Paarl en
Trawal) en somer-reënval (Upington en Groblersdal) streke. Wingerde (8 jaar en ouer) met die
kultivar Dan-ben-Hannah is gekies vir opname en monsters is gedurende Julie en Augustus 2004
geneem. Die distale deel van ‘n arm is verwyder vanaf 20 lukraak gekose plante in elke
wingerd. Hierdie dele is ontleed en isolasies is gemaak vanuit elke simptoomtipe wat beskryf is,
naamlik bruin en swart vaskulêre verkleuring, bruin interne nekrose, wig-vormige nekrose,
waterige nekrose, esca-geassosieerde bruin en geel sagte houtverrotting en asimptomatiese hout.
Identifikasie van die swamagtige isolate is gedoen op grond van morfologiese eienskappe en
molekulêre tegnieke. Pa. chlamydospora is die meeste geïsoleer (46.0%), gevolg deur
Phaeoacremonium aleophilum (10.0%), Phomopsis viticola (3.0%), Botryosphaeria obtusa
(3.0%), B. rhodina (2.2%), B. parva (2.0%), Fusicoccum vitifusiforme (0.6%), B. australis, B.
dothidea en ‘n onbeskryfde Diplodia sp. (0.2% elk), terwyl E. lata nie geïsoleer is nie. Hierdie
patogene is elk geïsoleer vanuit ‘n verskeidenheid simptoomtipes, wat daarop dui dat
siektediagnose nie alleenlik op simptomatologie gebaseer kan word nie. Pa. chlamydospora is
geïsoleer vanuit al die gebiede, alhoewel die patogeen opmerklik meer voorgekom het in die
winter-reënval area. Pm. aleophilum het hoofsaaklik voorgekom in Paarl, terwyl P. viticola
slegs in hierdie area voorgekom het. Alhoewel B. obtusa nie voorgekom het in die De Doorns en
Groblersdal areas nie, was dit die mees algemeen geïsoleerde Botryosphaeria sp. en het in
Upington, Paarl en Trawal voorgekom. B. rhodina het slegs in Groblersdal voorgekom, B. parva
in Paarl, Groblersdal en Trawal en B. australis het slegs in Paarl voorgekom. Die res van die isolate (33%) het bestaan uit steriele kulture, Exochalara, Cephalosporium, Wangiella,
Scytalidium, en Penicillium spesies asook twee onbekende basidiomycete isolate, geïsoleer
vanuit vyf monsters met geel eska-geassosieerde simptome vanuit die Paarl area. Hierdie
resultate illustreer dus die feit dat wingerdstamsiektes deur ‘n kompleks van swampatogene
veroorsaak word, wat belangrike implikasies het vir die bestuur en diagnose van hierdie siektes.
Wondbeskerming teen infeksie van enige van hierdie stamsiekte patogene is die mees
doeltreffende en koste-effektiewe manier om wingerdstamsiektes te voorkom. Vorige navorsing
aangaande die effektiwiteit van chemiese wondbeskermingsmiddels het egter slegs gefokus op
die beheer van Eutypa terugsterwing. In vitro swamdoder sensitiwiteitstoetse is gedoen vir Pa.
chlamydospora, P. viticola en Eutypa lata, maar geen studies is al gedoen ten opsigte van die
patogeniese Botryosphaeria spesies op wingerd in Suid-Afrika nie. Tien swamdoders is dus
getoets vir inhibisie van in vitro miseliumgroei van die vier mees algemene en/of patogeniese
Botryosphaeria spesies wat in Suid-Afrika voorkom, naamlik B. australis, B. obtusa, B. parva en
B. rhodina. Iprodione, pyrimethanil, koper ammonium asetaat, kresoxim-metiel en boscalid was
oneffektief by die hoogste konsentrasies getoets (5 μg/ml; 20 μg/ml vir koper ammonium
asetaat). Benomyl, tebuconasool, prochloraz mangaan chloried en flusilasool was die mees
effektiewe swamdoders met EC50 waardes tussen 0.36-0.55, 0.07-0.17, 0.07-1.15 en 0.04-0.36
μg/ml, onderskeidelik vir die verskillende spesies. Hierdie fungisiedes, behalwe prochloraz
mangaan chloried, is geregistreer op druiwe in Suid-Afrika en is ook effektief gevind teenoor Pa.
chlamydospora, P. viticola en E. lata. Resultate van biotoetse op 1-jaar-oue Chenin Blanc
wingerd lote het getoon dat benomyl, tebuconasool en prochloraz mangaan chloried die
effektiefste was om die lengte van letsels in snoeiwonde, geinokuleer met Botryosphaeria
spesies na die aanwending van swamdoder behandelings, te verminder. Die bevindinge was
egter onbeslis as gevolg van die lae en variërende her-isolerings data. Benomyl, tebuconasool,
prochloraz mangaan chloried en flusilasool kan egter geïdentifiseer word as swamdoders wat
verder geevalueer kan word as snoeiwond beskermingsmiddels teen Botryosphaeria spesies
asook ander wingerd stamsiekte patogene in verdere biotoetse en wingerdproewe.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/21550 |
| Date | 04 1900 |
| Creators | Bester, Wilma |
| Contributors | Fourie, P.H., 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 | 65 leaves : ill. |
| Rights | Stellenbosch University |
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