A New Canker Disease of Apple, Pear, and Plum Rootstocks-Caused by<i>Diaporthe ambigua</i>in South Africa

Smit, W. A.; Viljoen, Christopher D.; Wingfield, Brenda D.; Wingfield, M.J.; Calitz, F. J.

doi:10.1094/pd-80-1331

Cited by 36 publications

(22 citation statements)

References 6 publications

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“…Barr, C. macrospora (Kobayashi & Ito) Barr, C. nitschkei (Otth.) Barr, and C. radicalis (Smit et al 1996(Smit et al , 1997, was used as the outgroup taxon to root the phylogenetic trees (Table 1). Cultures are maintained in the culture collection (CMW) of the Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, South Africa.…”

Section: Fungal Isolatesmentioning

confidence: 99%

Conspecificity of Endothia eugeniae and Cryphonectria cubensis: a re-evaluation based on morphology and DNA sequence data

Myburg

Wingfield

et al. 2003

Mycoscience

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Cryphonectria cubensis and Endothia eugeniae are fungal pathogens of Eucalyptus and clove that were reduced to synonymy on the basis of results of crossinoculation studies, isozyme analysis, cultural studies, and morphology. A previous phylogenetic study on Cryphonectria, based on sequence variation in the ITS region of the ribosomal RNA operon, also supported the conspecificity of C. cubensis and E. eugeniae, but was based on only one E. eugeniae isolate. New collections from clove in Brazil and Indonesia have become available, providing the opportunity to reconsider the conspecificity of C. cubensis and E. eugeniae. The occurrence of C. cubensis on clove was confirmed based on morphological comparisons and phylogenetic analyses of ribosomal DNA and -tubulin gene sequence data. In addition to C. cubensis, other fungi morphologically similar to Cryphonectria species on the basis of their orange stromata were present on some clove specimens, but no isolates were available for these fungi. Furthermore, some isolates, for which no herbarium material exists, grouped separately from the C. cubensis clade and closer to the Cryphonectria clade. The presence of more than one closely related fungus on clove raises questions relating to the legitimacy of the synonymy of E. eugeniae and C. cubensis. Based on the presence of C. cubensis on the type specimen of E. eugeniae, we recognize the synonymy of the two fungi but provide evidence that other fungi, more closely related to Cryphonectria spp. than to C. cubensis, are present on clove.

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Section: Fungal Isolatesmentioning

confidence: 99%

Conspecificity of Endothia eugeniae and Cryphonectria cubensis: a re-evaluation based on morphology and DNA sequence data

Myburg

Wingfield

et al. 2003

Mycoscience

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“…include important pathogens of stone fruits, pome fruits, and grapevines worldwide (27,36,37). One of these species, D. perjuncta, is an important pathogen of grapevines (27).…”

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confidence: 99%

Transfection of Diaporthe perjuncta with Diaporthe RNA Virus

Moleleki¹,

Heerden²,

Wingfield

et al. 2003

Appl Environ Microbiol

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Diaporthe perjuncta is a pathogen of grapevines worldwide. A positive-strand RNA virus, Diaporthe RNA virus (DaRV), occurs in hypovirulent isolates of this fungus. A virus-free isolate from a South African grapevine was transfected with in vitro-transcribed positive strands of DaRV. Based on reverse transcription-PCR and partial sequence analysis, the transfected virus was identified as DaRV. The in vitro-transcribed RNA transcripts used to transfect fungal spheroplasts contained parts of the vector at their distal ends. These vector sequences were separated from the DaRV genome during replication in the new host. The transfected isolate had morphological features that differed from those of the isogenic virus-free strain, including production of a yellow pigment, a decreased growth rate, and lack of sporulation. An apple-based pathogenicity test did not reveal any differences in virulence between the virus-free and DaRV-transfected isolates. This study showed that virus-free fungal hosts can be successfully transfected with viruses other than the Cryphonectria parasitica hypovirus.Mycoviruses from many species of fungi have been observed and characterized at the genomic level (6,22,30). The fungal hosts include several well-known plant pathogens, including Cryphonectria parasitica (17,19,20,35),5,14,23,24,25), Helminthosporium victoriae (34), Sphaeropsis sapinea (32, 38), and Diaporthe perjuncta (28,31,37). In C. parasitica, the viruses CHV1-EP713 and CHV1-Euro7 mediate hypovirulence to various degrees (7,11,13). Vegetative compatibility groups restrict the spread of such viruses and have reduced the success of biological control through hypovirulence in the United States (1,2,3,26).The interest in viruses that infect fungi is strongly linked to the potential use of these viruses as biological control agents of plant-pathogenic fungi. An emerging area of interest is the use of mycoviruses to study basic genetic processes that lead to fungal pathogenesis (29). The fungal reaction, commonly manifested as hypovirulence-associated traits, is not a general response of the fungus to hypovirus infection but rather is a response triggered by molecular cues encoded by specific viral sequences (10, 12). Reverse genetics developed for the C. parasitica hypovirus has shown that specific mutations and deletions of specific regions of the hypovirus are associated with specific responses in the pathogen. For example, deletion of the papain-like protease, p29, from CHV1-EP713 encoded by open reading frame A restores orange pigmentation and moderately increases sporulation in transfected isolates (15).Although several mycoviral genomes have been sequenced and characterized, only the C. parasitica hypoviruses have been used in transfection and transformation studies (16). Thus, the progress in developing mycoviruses as possible biological control agents has been slow. In order to advance the field further, the reverse genetics developed for C. parasitica hypoviruses must be extended to mycoviruses with properties different from ...

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“…The basis of sexuality in D. ambigua clearly needs further study. At this stage we suspect, however, that D. ambigua on fruit trees is native in the country and that it probably originated from native woody plants such as rooibos tea (Aspalathus linearis) (Smit et al, 1994a).…”

Section: Discussionmentioning

confidence: 97%

“…Diaporthe canker of apple, pear and plum rootstocks is an important disease affecting the longevity and productivity of orchards in the Cape Province of South Africa (Smit et al, 1994a). Symptoms of the disease include pointed lesions that are depressed and separated from the bark by longitudinal cracks along their margins.…”

Section: Introductionmentioning

confidence: 99%

Vegetative incompatibility in Diaporthe ambigua

Smit

Wingfield²,

Wingfield³

1997

Plant Pathology

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Vegetative compatibility of strains of Diaporthe ambigua has not previously been examined. Single ascospore and single ascus strains, originating from individual apple, pear and plum rootstocks, were paired on freshly prepared oatmeal agar to determine if vegetative incompatibility could be detected in D. ambigua. Barrage reactions were evident as black lines along the zone of mycelial contact between expanding colonies (vegetative incompatibility reaction). Strains from cankers within an area were of numerous vegetative compatibility groups (VCGs). Strains from adjacent rootstocks usually differed in VCG. D. ambigua has the ability to outcross, and does so, despite its apparent homothallic nature. DsRNA-containing strains of D. ambigua developed a broad, clear zone when paired with a dsRNA-containing strain from a different VCG.

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A New Canker Disease of Apple, Pear, and Plum Rootstocks-Caused byDiaporthe ambiguain South Africa

Cited by 36 publications

References 6 publications

Conspecificity of Endothia eugeniae and Cryphonectria cubensis: a re-evaluation based on morphology and DNA sequence data

Conspecificity of Endothia eugeniae and Cryphonectria cubensis: a re-evaluation based on morphology and DNA sequence data

Transfection of Diaporthe perjuncta with Diaporthe RNA Virus

Vegetative incompatibility in Diaporthe ambigua

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