Several species of fungi and oomycetes including
Fusarium, Rhizoctonia, Phytophthora
and
Pythium
have been reported as root pathogens of apple where they contribute to a phenomenon known as apple ...replant disease. In South Africa, little is known about specific species in these genera and their pathogenicity toward apple. Therefore, these aspects were investigated along with the development and optimization of qPCR tests for detection and quantification of the most virulent oomycete species. In eight investigated orchards, the oomycete
Phythophthora cactorum
was widely distributed, while nine
Pythium
species were differentially distributed among the orchards
. Pythium irregulare
was the most widely distributed and the most virulent species along with
P. sylvaticum, P. vexans
and
Ph. cactorum.
Seven binucleate
Rhizoctonia
anastomosis groups (AGs) were also differentially distributed among the orchards, with the majority appearing to be non-pathogenic while certain AG-I and AG-F isolates exhibited low virulence on apple. In the genus
Fusarium, F. oxysporum
was widely distributed, but isolates were non-pathogenic.
Fusarium solani
and
F. avenaceum
were less frequently encountered, with only some isolates having low virulence. qPCR data obtained from seedling roots inoculated with the most virulent
Pythium
species (
P. irregulare, P. sylvaticum
and
P. vexans
) and the genus
Phytophthora
were not always reproducible between trials, or isolates of the same species. In general, seedling growth inhibition was associated with the presence of a low amount of pathogen DNA (±40 fg μl
−1
to 2 pg μl
−1
) in roots.
Pythium irregulare,
although having the lowest DNA concentrations in roots, was the only species for which a significant negative correlation was found between seedling weight and pathogen DNA concentration.
Two cases of phaeohyphomycotic infections were caused by
, not previously identified in human infections, and one new species,
, respectively. Morphological and cultural investigation as well as ...phylogenetic analysis was constructed based on maximum likelihood analyses using actin and -tubulin sequences to identify the fungal isolates.
Genera of phytopathogenic fungi: GOPHY 2 Marin-Felix, Y.; Hernández-Restrepo, M.; Wingfield, M.J. ...
Studies in mycology,
03/2019, Letnik:
92, Številka:
1
Journal Article
Recenzirano
Odprti dostop
This paper represents the second contribution in the Genera of Phytopathogenic Fungi (GOPHY) series. The series provides morphological descriptions and information regarding the pathology, ...distribution, hosts and disease symptoms for the treated genera. In addition, primary and secondary DNA barcodes for the currently accepted species are included. This second paper in the GOPHY series treats 20 genera of phytopathogenic fungi and their relatives including: Allantophomopsiella, Apoharknessia, Cylindrocladiella, Diaporthe, Dichotomophthora, Gaeumannomyces, Harknessia, Huntiella, Macgarvieomyces, Metulocladosporiella, Microdochium, Oculimacula, Paraphoma, Phaeoacremonium, Phyllosticta, Proxypiricularia, Pyricularia, Stenocarpella, Utrechtiana and Wojnowiciella. This study includes the new genus Pyriculariomyces, 20 new species, five new combinations, and six typifications for older names.
Sixteen Pythium isolates from diverse hosts and locations, which showed similarities in their morphology and sequences of the internal transcribed spacer (ITS) region of their rRNA gene, were ...investigated. As opposed to the generally accepted view, within single isolates ITS sequence variations were consistently found mostly as part of a tract of identical bases (A-T) within ITS1, and of GT or GTTT repeats within the ITS2 sequence. Thirty-one different ITS sequences obtained from 39 cloned ITS products from the 16 isolates showed high sequence and length polymorphisms within and between isolates. However, in a phylogenetic analysis, they formed a cluster distinct from those of other Pythium species. Additional sequencing of two nuclear genes (elongation factor 1α and β-tubulin) and one mitochondrial gene (nadh1) revealed high levels of heterozygosity as well as polymorphism within and between isolates, with some isolates possessing two or more alleles for each of the nuclear genes. In contrast to the observed variation in the ITS and other gene areas, all isolates were phenotypically similar. Pythium mercuriale sp. nov. (Pythiaceae) is characterized by forming thin-walled chlamydospores, subglobose to obovoid, papillate sporangia proliferating internally and smooth-walled oogonia surrounded by multiple antheridia. Maximum likelihood phylogenetic analyses based on both ITS and β-tubulin sequence data place P. mercuriale in a clade between Pythium and Phytophthora.
Several fungal trunk pathogens are associated with olive trunk diseases in South Africa. Little is known regarding the inoculum sources of these pathogens in the olive industry, and no specific ...management strategies are in place. The aim of this study was to investigate the status of olive nurseries in South Africa, with regard to the presence of trunk pathogens in olive plant material, to determine whether nursery material can be considered inoculum sources contributing to long-distance dispersal of these pathogens. Isolations were made from asymptomatic cuttings from mother blocks (stage 1), asymptomatic and symptomatic rooted cuttings (stage 2), and 1- to 2-year-old trees (stage 3) of eight cultivars in two nurseries. Known olive trunk pathogens of Nectriaceae, Diaporthaceae, Botrysphaeriaceae, Togniniaceae, Phaeomoniellaceae, and Pleurostomataceae were recovered.
was detected in a single stage 1 cutting. Stage 3 material showed the highest incidence of fungi from these families, with
having the highest incidence in both nurseries (82.2 and 36.7% of the 1- to 2-year-old trees).
was present in 28.9% of the trees from one nursery (stage 3). The remaining pathogens occurred in ≤13.3% of the material. These results indicate that nursery propagation material from mother blocks harbors low levels of trunk pathogens and that additional infections occur during the nursery process. Management strategies should focus on the prevention and elimination of infections in mother blocks as well as during the propagation process to ensure that pathogen-free material is delivered to producers.
Nineteen Phaeoacremonium species are currently known in South Africa. These have been reported from grapevines, fruit trees, fynbos twig litter and arthropods. In other countries some of these ...Phaeoacremonium species are also known from hosts such as European olive, quince
and willow that commonly occur in the Western Cape Province of South Africa, where most South African records of Phaeoacremonium have been made. The aim of this study was to investigate the species diversity and host-range of Phaeoacremonium in the Western Cape Province of South
Africa by characterising 156 isolates collected from 29 woody hosts. Phylogenetic analyses of combined actin and beta-tubulin datasets allowed for the identification of 31 species among the 156 isolates, including 13 new species and 3 known species that had not been recorded in South Africa
previously. The new Phaeoacremonium species include P. album, P. aureum, P. bibendum, P. gamsii, P. geminum, P. junior, P. longicollarum, P. meliae, P. oleae,
P. paululum, P. proliferatum, P. rosicola and P. spadicum. All previous records of P. alvesii in South Africa were re-identified as P. italicum, but both species were recovered during this survey. A total of 35 described
Phaeoacremonium species are now known from South Africa, more than double the number reported from any other country. This high diversity reflects the high diversity of indigenous flora of the Cape Floral Region, a biodiversity hotspot mainly situated in the Western Cape Province. Paraphyly
and incongruence between individual phylogenies of the actin and beta-tubulin regions complicated species delimitation in some cases indicating that additional phylogenetic markers should be investigated for use in Phaeoacremonium phylogenies to prevent misidentifications and the introduction
of vague species boundaries.
Recent studies in grape-growing areas including Australia, California, and Spain have revealed an extensive diversity of Diatrypaceae species on grapevines showing dieback symptoms and cankers. ...However, in South Africa, little is known regarding the diversity of these species in vineyards. The aim of this study was, therefore, to identify and characterize Diatrypaceae species associated with dieback symptoms of grapevine in South Africa. Isolates were collected from dying spurs of grapevines aged 4 to 8 years old, grapevine wood showing wedge-shaped necrosis when cut in cross section as well as from perithecia on dead grapevine wood. The collected isolates were identified based on morphological characters and phylogenetic analyses of the internal transcribed spacer region (ITS) and β-tubulin gene. Seven Diatrypaceae species were identified on grapevine, namely Cryptovalsa ampelina, C. rabenhorstii, Eutypa consobrina, E. lata, E. cremea sp. nov., Eutypella citricola, and E. microtheca. The dying spurs yielded the highest diversity of species when compared with the wedge-shaped necrosis and/or perithecia. C. ampelina was the dominant species in the dying spurs, followed by E. citricola, whereas E. lata was the dominant species isolated from the wedge-shaped necroses and perithecia. These results confirm E. lata as an important grapevine canker pathogen in South Africa, but the frequent association of C. ampelina with spur dieback suggests that this pathogen plays a more prominent role in dieback than previously assumed. In some cases, more than one species were isolated from a single symptom, which suggests that interactions may be occurring leading to decline of grapevines. C. rabenhorstii, E. consobrina, E. citricola, E. microtheca, and E. cremea are reported for the first time on grapevine in South Africa.
Several Phytophthora spp. are known to cause a range of symptoms on citrus, resulting in significant crop losses worldwide. In South Africa, Phytophthora remains a destructive citrus disease, but the ...species and their distribution have not been well documented. A total of 162 Phytophthora isolates was collected from 60 citrus orchards in seven provinces of South Africa (Eastern Cape, Kwazulu-Natal, Limpopo, Mpumalanga, Northern Cape, North West and Western Cape). Isolates were identified to the species level through PCR-RFLP (restriction fragment length polymorphism) analyses of the internal transcribed spacer region. The identity of a subset of the isolates was confirmed using morphological and sequence analyses. Phytophthora nicotianae was the predominant species (76 % of isolates) and occurred in 80 % of the orchards in all of the provinces, followed by P. citrophthora (22 % of isolates in 28 % of orchards). The P. citrophthora isolates were further subdivided into two previously identified subgroups, G1 and G2, with most (69 %) of the isolates belonging to the G1 subgroup. Other Phytophthora species included P. multivora in the Western Cape Province, and an unknown species in the Eastern Cape Province with high sequence similarity (98 %) to a putative new species submitted to GenBank as Phytophthora taxon Sisuluriver. Phytophthora palmivora, a known citrus pathogen, was not identified. Most of the P. nicotianae isolates (79 %) were of the A1 mating type. The P. citrophthora isolates were mostly sterile (64 %), including most of the G1 isolates (81 %). The remaining G1 isolates (19 %) belonged to the A1 mating type, whereas almost all G2 isolates belonged to the A2 mating type except for one isolate that was sterile.
A recent olive trunk disease survey performed in the Western Cape Province, South Africa, identified several fungi associated with olive trunk disease symptoms, including species of Basidiomycota, ...Botryosphaeriaceae, Coniochaetaceae, Calosphaeriaceae, Diaporthaceae, Diatrypaceae, Phaeomoniellaceae, Phaeosphaeriaceae, Symbiotaphrinaceae, Togniniaceae, and Valsaceae. Many of the species recovered had not yet been reported from olive trees; therefore, the aim of this study was to determine their pathogenicity toward this host. Pathogenicity tests were first conducted on detached shoots to select virulent isolates, which were then used in field trials. During field trials, 2-year-old olive branches of 15-year-old trees were inoculated by inserting colonized agar plugs into artificially wounded tissue. Measurements were made of the internal lesions after 8 months. In total, 58 isolates were selected for the field trials. Species that formed lesions significantly larger than the control could be considered as olive trunk pathogens. These included
,
,
,
, isolates of the
complex,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
, an undescribed
sp.,
sp., two undescribed
spp., and four
spp.
can be regarded as one of the main olive trunk pathogens in South Africa because of its high incidence from olive trunk disease symptoms in established orchards and its high virulence in pathogenicity trials.
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