Browsing by Author "Crous, Pedro W."
Now showing 1 - 4 of 4
Results Per Page
Sort Options
- ItemDiaporthaceae associated with root and crown rot of maize(International Mycological Association, 2011-03-10) Lamprecht, Sandra C.; Crous, Pedro W.; Groenewald, Johannes Z.; Tewoldemedhin, Yared T.; Marasas, Walter F. O.Several isolates of coelomycetous fungi with pigmented conidia were consistently isolated from diseased roots of Zea mays in irrigated plots monitored in the KwaZulu-Natal Province of South Africa. Based on their morphology, these isolates could be identified as representative of Stenocarpella macrospora, S. maydis, and Phaeocytostroma ambiguum. Although species of Stenocarpella are well-known as causal agents of cob and stalk rot and leaf blight of maize in South Africa, the occurrence and importance of P. ambiguum is less well documented and understood. To determine the role of P. ambiguum as a root pathogen of maize, pathogenicity tests were conducted under glasshouse conditions at 18 °C night and 28 °C day temperatures using a pasteurised soil, river sand and perlite medium and a 0.5 % sand-bran inoculum. Based on these results, P. ambiguum was shown to be a primary pathogen of maize, but to be less virulent than the positive control, S. maydis. Furthermore, to clarify the higher-level phylogeny of these fungal genera, isolates were subjected to DNA sequencing of the nuclear ribosomal DNA(ITS & LSU). Partial gene sequences of the translation elongation factor 1-alpha gene were added to confirm the species monophyly. To resolve the generic placement of Phaeocytostroma, additional species such as P. sacchari, P. plurivorum and P. megalosporum were also added to the analysis. Based on these results, Stenocarpella and Phaeocytostroma were shown to be two well defined genera, belonging to Diaporthales, Diaporthaceae, being closely allied to Phomopsis (Diaporthe). All three genera were also observed to form alpha as well as beta conidia, and although this phenomenon is well documented for Phomopsis and Phaeocytostroma, it is a new observation for Stenocarpella. In spite of the differences in conidial pigmentation, no support could be obtained for polyphyly in Diaporthaceae, suggesting that as observed in Botryosphaeriaceae (Botryosphaeriales), conidial pigmentation is not informative at the family level in Diaporthales.
- ItemLiberomyces pistaciae sp. nov., the causal agent of pistachio cankers and decline in Italy(Pensoft Publishers, 2018) Vitale, Salvatore; Aiello, Dalia; Guarnaccia, Vladimiro; Luongo, Laura; Galli, Massimo; Crous, Pedro W.; Polizzi, Giancarlo; Belisario, Alessandra; Voglmayr, HermannA new canker and decline disease of pistachio (Pistacia vera) is described from Sicily (Italy). Observations of the disease and sampling of the causal agent started in spring 2010, in the area where this crop is typically cultivated, Bronte and Adrano (Catania province) and later extended to the Agrigento and Caltanissetta provinces. Isolations from the margins of twig, branch and stem cankers of declining plants resulted in fungal colonies with the same morphology. Pathogenicity tests on 5-year-old potted plants of Pistacia vera grafted on P. terebinthus reproduced similar symptoms to those observed in nature and the pathogen was confirmed to be a coloniser of woody plant tissue. Comparison of our isolates with the type of the apparently similar Asteromella pistaciarum showed that our isolates are morphologically and ecologically different from A. pistaciarum, the latter being a typical member of Mycosphaerellaceae. Asteromella pistaciarum is lectotypified, described and illustrated and it is considered to represent a spermatial morph of Septoria pistaciarum. Multi-locus phylogenies based on two (ITS and LSU rDNA) and three (ITS, rpb2 and tub2) genomic loci revealed isolates of the canker pathogen to represent a new species of Liberomyces within the Delonicicolaceae (Xylariales), which is here described as Liberomyces pistaciae sp. nov. (Delonicicolaceae, Xylariales). The presence of this fungus in asymptomatic plants with apparently healthy woody tissues indicates that it also has a latent growth phase. This study improves the understanding of pistachio decline, but further studies are needed for planning effective disease management strategies and ensuring that the pathogen is not introduced into new areas with apparently healthy, but infected plants.
- ItemPhyllosticta citricarpa and sister species of global importance to Citrus(British Society for Plant Pathology, 2020) Guarnaccia, Vladimiro; Gehrmann, Thies; Silva-Junior, Geraldo J.; Fourie, Paul H.; Haridas, Sajeet; Vu, Duong; Spatafora, Joseph; Martin, Francis M.; Robert, Vincent; Grigoriev, Igor V.; Groenewald, Johannes Z.; Crous, Pedro W.Several Phyllosticta species are known as pathogens of Citrus spp., and are responsible for various disease symptoms including leaf and fruit spots. One of the most important species is P. citricarpa, which causes a foliar and fruit disease called citrus black spot. The Phyllosticta species occurring on citrus can most effectively be distinguished from P. citricarpa by means of multilocus DNA sequence data. Recent studies also demonstrated P. citricarpa to be heterothallic, and reported successful mating in the laboratory. Since the domestication of citrus, different clones of P. citricarpa have escaped Asia to other continents via trade routes, with obvious disease management consequences. This pathogen profile represents a comprehensive literature review of this pathogen and allied taxa associated with citrus, focusing on identification, distribution, genomics, epidemiology and disease management. This review also considers the knowledge emerging from seven genomes of Phyllosticta spp., demonstrating unknown aspects of these species, including their mating behaviour.
- ItemSpecies of Diaporthe on Camellia and Citrus in the Azores Islands(Firenze University Press, 2018) Guarnaccia, Vladimiro; Crous, Pedro W.Species of Diaporthe are important plant pathogens, saprobes, and endophytes on a wide range of plant hosts. Species such as D. citri are well-known on Citrus, as agents of pre- or post-harvest infections, causing dieback, melanose and stem-end rot on fruit. In this study we explored the occurrence and diversity of Diaporthe associated with tropical and sub-tropical plants. In particular, species of Camellia and Citrus were sampled. Surveys were carried out during 2017 in the Azores Islands, Portugal. Ten Diaporthe strains were isolated from symptomatic twigs and leaves. Five representative isolates were subjected to morphological characterization and multi-locus phylogeny based on five genomic loci (ITS, tef1, cal, his3 and tub2). Diaporthe citri was found associated with shoot blight on Citrus reticulata, which represents a new record for Europe. A new species, Diaporthe portugallica sp. nov. was isolated and described from leaf spots on Camellia sinensis.