Thesis (MScAgric.)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: Phomopsis cane and leaf spot disease of grapevine is an economically important disease
in many of the vine-growing areas of the world. Four different Phomopsis spp. have
previously been associated with this disease. The present study investigates the
taxonomic significance of the different taxa found on grapevines in South Africa, as well
as the endophytic growth and fungicide sensitivity of Phomopsis viticola isolates. The
thesis is compiled of several different parts, which deal with specific, but related topics,
and hence some duplication has been unavoidable.
Understanding the epidemiology of a disease is important for the correct timing of
disease control. To investigate the endophytic growth of P. viticola, asymptomatic
shoots were collected at eight different growth stages. Nodes, internodes, leaf petioles,
leaves, tendrils and bunch peduncles were investigated. Two Phomopsis spp., taxon 1 and
2 were identified in this study. The Phomopsis viticola-complex had a relative
importance of 9% and accounted for 3% of the isolations. P. viticola (taxon 2) is mainly
isolated from the nodes and internodes. Inoculations of healthy, young vine tissue
confirmed taxon 2 to be a virulent pathogen, suggesting that it is a latent pathogen rather
than an endophyte. In contrast, taxon 1 appeared to be a true endophyte, and did not
seem to be an important pathogen on vines.
The true identity of the causal organism of Phomopsis cane and leaf spot disease
was investigated by collecting samples from 58 different vineyards in the grapevine
growing areas of the Western Cape. P. viiicola occurred in grapevine material collected
from Lutzville to Swellendam, but was not found in the Oudtshoorn and Orange River
grapevine areas. Diaporthe perjuncta (taxon 1), P. vutcola (taxon 2), taxon 3 and a
Phomopsis species commonly associated with shoot blight of peaches in the U.S.A., P.
amygdali, were identified among the South African grapevine isolates. Examination of
the Australian culture designated as taxon 4 found it to be a species of Libertella, thus
excluding it from the P. viticola-complex. An Italian isolate was found to represent a
species of Phomopsis not previously known from grapevines, and this was subsequently
described as taxon 5. Species delimitation was based on morphological and cultural
characteristics, stem inoculations and the formation of the teleomorph in vitro. The
identity of each morphological taxon was confirmed by means of phylogenetic analyses
of the nuclear ribosomal DNA internal transcribed spacers (ITS 1 and ITS2) and the 5'
end partial sequence of the mitochondrial small subunit (mtSSU). P. amygdali,
associated with peach shoot blight in the U.S.A., was isolated once only and appeared to
be of lesser importance in this disease complex. Furthermore, taxa 1 (Diaporthe
perjuncta) and 3 were also rarely encountered and proved to be non-pathogenic,
indicating their non-functional role in Phomopsis cane and leaf spot disease. Taxon 2
(Phomopsis viticolas was common and widely distributed in diseased vineyards. This
taxon was associated with the typical disease symptoms and proved to be pathogenic.
Morphologically taxon 2 corresponded best with P. viticola, which was also neotypified
in this study. Taxon 2 was mostly isolated from buds and nodes, indicating that these are
important sites in which the fungus survives during winter. Molecular data indicated that
taxon 3 and P. amygdali were not host specific to grapevine.
The currently used foliar fungicides were compared to the new strobilurin
fungicides. The effects of nine fungicides (azoxystrobin, flusilazole, folpet, fosetyl-
Al+mancozeb, kresoxim-methyl, mancozeb, penconazole, spiroxamine and
trifloxystrobin) were tested in vitro on inhibition of mycelial growth. The following EC50
(ug/ml) values were obtained: azoxystrobin (0.350), flusilazole (0.007), folpet (4.489),
fosetyl-Al+mancozeb (3.925), kresoxim-methyl (1.665), mancozeb (2.891), penconazole
(0.023), spiroxamine (0.321) and trifloxystrobin (0.051). Additionally, azoxystrobin,
folpet, kresoxim-methyl, mancozeb, propineb and trifloxystrobin were tested for their
ability to inhibit spore germination in vitro. The subsequent EC50 (ug/ml) values were
obtained: azoxystrobin 0.123), folpet (0.510), kresoxim-methyl (0.0037), mancozeb
(0.250), propineb (0.156) and trifloxystrobin (0.003). The results reported in part 4
showed that the strobilurin fungicides inhibited the mycelial growth and spore
germination of P. viticola. However, further trials need to be conducted to verify these
findings under field conditions. In the present study taxa 1, 3 and P. amygdali were
infrequently isolated, suggesting that they played a less prominent role in the P. viticolacomplex. / AFRIKAANSE OPSOMMING: Streepvleksiekte van wingerd is 'n ekonomies belangrike siekte wat in die meeste
wingerdproduserende gebiede van die wêreld voorkom. Vier Phomopsis spesies is in die
verlede met dié siekte geassosieer. Hierdie studie ondersoek die taksonomiese
belangrikheid van die verskillende taksa wat op wingerd in Suid Afrika gevind word,
asook die endofietiese groei en fungisiedsensitiwiteit van die Phomopsis vitico/a isolate.
Hierdie tesis bestaan uit verskeie dele met spesifieke, maar verwante onderwerpe wat tot
onafwendbare duplisering lei.
Dit is belangrik om die epidemiologie van 'n siekte te verstaan sodat korrekte en
tydsberekende siektebeheer toegepas kan word. Die endofietiese groei van P. vitico/a is
ondersoek deur simptoomlose lote by agt verskillende groei stadiums te versamel.
Nodusse, internodusse, blaarstele, blare, rankies en trosstele is ondersoek. Twee
Phomopsis spp., takson 1 en 2 is geïdentifiseer. Die Phomopsis vitico/a-kompleks het
3% van die isolasies uitgemaak en 'n relatiewe belangrikheid van 9% getoon. P. vitico/a
(takson 2) is meestal uit die nodus en internodus geïsoleer. lnokulasies van gesonde, jong
wingerdweefsel het bevestig dat takson 2 'n virulente patogeen is en dat die takson eerder
'n latente patogeen as 'n endofiet is. In teenstelling hiermee is takson 1 'n ware endofiet
en 'n onbelangrike patogeen op wingerd.
Die ware identiteit van die veroorsakende organisme van streepvlek is ondersoek
deur plantmateriaal vanaf 58 verskillende wingerde in die wingerproduserende gebiede
van die Wes-Kaap te versamel. P. vitico/a is in wingerdmateriaal vanaf Lutzville tot
Swellendam aangetref, maar nie in die Oudtshoorn en Oranjerivier wingerd produserende
gebiede nie. Diaporthe perjuncta (takson 1), P. vitico/a (takson 2), takson 3 en P.
amygdali is in die Suid Afrikaanse wingerdisolate geïdentifiseer. P. amygdali word met
lootverskroeiing van perske bome in die V.S.A. geassosieer. Die Australiese isolaat wat
benoem is as takson 4, is met die huidige ondersoek gevind om 'n spesie van Libertella
te wees. Takson 4 is daarvolgens uit die P. vitico/a-kompleks gelaat. 'n Italiaanse isolaat
het 'n nuwe spesie van Phomopsis op wingerd verteenwoordig en is vervolgens as takson
5 beskryf. Spesie-onderskeiding is op morfologiese en kulturele eienskappe,
staminokulasies en die vorming van die teleomorf in vitro gebaseer. Die identiteit vanelke morfologiese takson is met behulp van filogenetiese analises van die nukleêre
ribosomale DNS intern transkriberende spasieerders (ITS 1 en ITS2) en die 5' punt
gedeeltelike nukleotied volgorde van die mitochondriale klein subeenheid (mtSSU)
bevestig. P. amygdali is slegs een keer geïsoleer en blyk van minder belang in die
siektekompleks te wees. Takson 1 (Diaporthe perjuneta) en takson 3 het ook min
voorgekom en is nie-patogenies, wat hul nie-funksionele rol in streepvleksiekte aandui.
Takson 2 (P. viticola) is algemeen geïsoleer en kom wyd verspreid voor. Hierdie takson
is geassosieer met die tipiese siektesimptome en is ook patogenies. Morfologies stem
takson 2 met P. viiicola ooreen en is ook geneotipifiseer in hierdie studie. Takson 2 is
meestal vanaf die ogies en nodusse geïsoleer, wat daarop dui dat hierdie belangrike setels
is waar die swam tydens die winter oorleef. Die molekulêre data toon aan dat takson 3 en
P. amygdali nie gasheerspesifiek tot wingerd is nie.
Die swamdoders wat tans teen streepvlek gebruik word, is met die nuwe
strobilurin swamdoders vergelyk. Die effek van nege swamdoders (azoksistrobin,
flusilasool, folpet, fosetyl-Al + mancozeb, kresoxirn-metiel, mankozeb, penconasool,
spiroksamien en trifloksistrobin) is in vitro op die inhibisie van miseliumgroei getoets.
Die volgende EKso-waardes (g/ml) is verkry: azoxystrobin (0.350), flusilasool (0.007),
folpet (4.489), fosetiel-Al + mankozeb (3.925), kresoxirn-metiel (l.665), mankozeb
(2.891), penkonasool (0.023), spiroksamien (0.321) en trifloxystrobin (0.051).
Azoxystrobin, folpet, kresoxim-rnetiel, mankozeb, propineb en trifloksistrobin is ook in
vitro getoets vir hul inhibisie op spoorontkieming. Die volgende EKso-waardes is verkry:
azoxystrobin (0.123), folpet (0.510), kresoxim-metiel (0.0037), mankozeb (0.250),
propineb (0.156) en trifloxystrobin (0.003). Die resultate vervat in deel 4 toon dat die
strobilurin swamdoders die miseliumgroei en spoorontkieming van P. viticola inhibeer.
Toetsing in die veld word egter benodig om die effektiwiteit van die middels te bevestig.
In hierdie studie is taksa I, 3 en P. amygdali selde geïsoleer, wat aangedui het dat hierdie
taksa 'n minder belangrike rol in die P. viticola-kompleks speel.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/51945 |
| Date | 12 1900 |
| Creators | Mostert, Lizel |
| Contributors | 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 | 116 p. : ill. |
| Rights | Stellenbosch University |
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