Ana Paula Ramos

Genome size analyses of Pucciniales reveal the largest fungal genomes.

Rust fungi (Basidiomycota, Pucciniales) are biotrophic plant pathogens which exhibit diverse complexities in their life cycles and host ranges. The completion of genome sequencing of a few rust fungi has revealed the occurrence of large genomes. Sequencing efforts for other rust fungi have been hampered by uncertainty concerning their genome sizes. Flow cytometry was recently applied to estimate the genome size of a few rust fungi, and confirmed the occurrence of large genomes in this order (averaging 225.3 Mbp, while the average for Basidiomycota was 49.9 Mbp and was 37.7 Mbp for all fungi). In this work, we have used an innovative and simple approach to simultaneously isolate nuclei from the rust and its host plant in order to estimate the genome size of 30 rust species by flow cytometry. Genome sizes varied over 10-fold, from 70 to 893 Mbp, with an average genome size value of 380.2 Mbp. Compared to the genome sizes of over 1800 fungi, Gymnosporangium confusum possesses the largest fungal genome ever reported (893.2 Mbp). Moreover, even the smallest rust genome determined in this study is larger than the vast majority of fungal genomes (94%). The average genome size of the Pucciniales is now of 305.5 Mbp, while the average Basidiomycota genome size has shifted to 70.4 Mbp and the average for all fungi reached 44.2 Mbp. Despite the fact that no correlation could be drawn between the genome sizes, the phylogenomics or the life cycle of rust fungi, it is interesting to note that rusts with Fabaceae hosts present genomes clearly larger than those with Poaceae hosts. Although this study comprises only a small fraction of the more than 7000 rust species described, it seems already evident that the Pucciniales represent a group where genome size expansion could be a common characteristic. This is in sharp contrast to sister taxa, placing this order in a relevant position in fungal genomics research.

Flow cytometry reveals that the rust fungus, Uromyces bidentis (Pucciniales), possesses the largest fungal genome reported—2489 Mbp

Among the Eukaryotes, Fungi have relatively small genomes (average of 44.2 Mbp across 1850 species). The order Pucciniales (Basidiomycota) has the largest average genome size among fungi (305 Mbp), and includes the two largest fungal genomes reported so far (Puccinia chrysanthemi and Gymnosporangium confusum, with 806.5 and 893.2 Mbp, respectively). In this work, flow cytometry was employed to determine the genome size of the Bidens pilosa rust pathogen, Uromyces bidentis. The results obtained revealed that U. bidentis presents a surprisingly large haploid genome size of 2489 Mbp. This value is almost three times larger than the previous largest fungal genome reported and over 50 times larger than the average fungal genome size. Microscopic examination of U. bidentis nuclei also showed that they are not as different in size from the B. pilosa nuclei when compared with the differences between other rusts and their host plants. This result further reinforces the position of the Pucciniales as the fungal group with the largest genomes, prompting studies addressing the role of repetitive elements and polyploidy in the evolution, pathological specialization and diversity of fungal species.

First record of the pepper tree psyllid, Calophya schini Tuthill (Hemiptera, Calophyidae), in the Palaearctic region

The presence of the psyllid Calophya schini infesting the Peruvian pepper tree, Schinus molle, was detected in several localities in the region of Lisbon, in Portugal. This is the first record of this jumping plant-louse in Europe and the Palaearctic region.

Validation of standards suitable for genome size estimation of fungi

Genome size information is fundamental to genome sequencing and may also uncover genomic aspects of evolution. Flow Cytometry, the preferred method for genome size estimation, requires suitable standards. Here we validate Inonotus hispidus, Colletotrichum acutatum and Cenococcum geophilum (41, 68 and 203Mbp), as standards for fungal genome size estimation.

First Report of Puccinia hemerocallidis Causing Daylily Rust in Europe

Starting in November 2015, rust symptoms were observed on daylily plants in gardens in Portugal, namely in the Lisbon and Tavira areas, and at Funchal on Madeira island. Diseased plants presented bright orange pustules frequently entirely covering the leaves of Hemerocallis lilioasphodelus L. plants (25 to 75% of leaf surface covered with pustules), with most plants symptomatic (85 to 90% of plants affected). Diseased plants were recorded in six out on nine gardens surveyed. Microscopic examination of pustules revealed the presence of urediniospores and teliospores. Uredinia were subepidermal and yellow or orange-yellow but soon erumpent and bright orange. Urediniospores were globose to ellipsoid, 19 to 24 × 16 to 21 μm, pale yellow, uniformly echinulate. Telia were subepidermal and blackish-brown. Teliospores were produced in locules, clavate to ellipsoid, 30 to 40 × 12 to 15 μm, pedicellate, and surrounded by brown paraphyses. Morphological characteristics match the description of Puccinia hemerocallidis von Thümen (EPPO 2009). Specimens were stored in the fungal collection of the “João de Carvalho e Vasconcelos” herbarium (LISI-Fungi) under accession numbers LISI-Fungi-00063 to 00066. Detached leaves of healthy H. lilioasphodelus and H. minor Mill plants (five leaves per species) were inoculated by spraying a urediniospore suspension as described by Mueller et al. (2003). Inoculated leaves were maintained in a wet chamber under darkness at 20°C. Uredinia were observed 4 days after inoculation on H. lilioasphodelus leaves and 12 days after inoculation on H. minor leaves. The experiment was repeated twice with similar results. Quick Links Add to favorites E-mail to a colleague Alert me when new articles cite this article Download to citation manager Related articles found in APS Journals Article History Issue Date: 14 Sep 2016 Published: 13 Jul 2016 First Look: 23 May 2016 Accepted: 13 May 2016 First Report of Puccinia hemerocallidis Causing Daylily Rust in Europe — Plant Disease http://apsjournals.apsnet.org/doi/full/10.1094/PDIS-02-16-0242-PDN[17-10-2016 14:18:06] Symptoms and the morphology of urediniospores were similar to those observed in field infections. Hemerocallis is a monocotyledonous genus originating from eastern Asia, with several species cultivated as perennial garden plants in many parts of the world, regarded by horticulturalists as easy to cultivate. Daylily rust has been reported from different areas of eastern and southeastern Asia, including Siberia (Russia) where P. hemerocallidis was first described in 1880 on H. fulva L. It was not until the 21st century that the disease was reported from all continents (in Australia, South Africa, Brazil, Colombia, Venezuela, Panama, Canada, and the United States) (EPPO 2009) except Europe, where it is part of the A1 list of quarantine pests (EPPO 2015). The European Plant Protection Organization (EPPO) pointed out the risk of inoculum survival as urediniospores overwintering on foliageretaining plants under mild winter conditions in southern European countries (EPPO 2009), similar to the scenario in the southern United States (Williams-Woodward et al. 2001). In cooler climates, where daylilies lose their leaves during winter, the disease cycle is naturally broken as urediniospores are unable to survive and overwintering teliospores fail to continue the P. hemerocallidis life cycle due to the virtual absence of the aecial host (Patrinia spp.) in Europe and North America (EPPO 2009). This represents the first report of this disease in Portugal and in Europe, raising concern on its dissemination into the European daylily industry (with over 2,000 European-bred cultivars), as most cultivars tested in the United States are susceptible (Blythe et al. 2015; Mueller et al. 2003). References: Section: Blythe, E. K., et al. 2015. HortTechnology 25:551. [ISI] EPPO. 2009. EPPO Bull 39:48. 10.1111/j.1365-2338.2009.02235.x [CrossRef] EPPO. 2015. EPPO A1 AND A2 lists of pests recommended for regulation as quarantine pests. EPPO, Paris. Mueller, D. S., et al. 2003. HortScience 38:1137. [ISI] Williams-Woodward, J. L., et al. 2001. Plant Dis. 85:1121. 10.1094/PDIS.2001.85.10.1121C [Abstract]

First Report of Puccinia thaliae Causing Rust on Canna spp. in Europe

In August and September 2015, rust symptoms were observed on naturalized Canna indica L. plants near Faial da Terra and Feteira villages on São Miguel Island in the Azores archipelago and also on Canna × hybrida plants in a garden at Funchal in Madeira Island, both in Portugal. No rust symptoms were detected in canna on the Portuguese mainland. Disease symptoms were observed on both leaf surfaces, with orange-yellow pustules frequently uniformly covering the entire surface. Infection spots became necrotic with time, and many small holes (3 to 5 mm diameter) developed on older leaves as a result of such necroses. At the Azores, disease incidence was high, with most plants exhibiting disease symptoms, and severity was mostly high, with the surface of many leaves in each plant covered with spore masses. At Madeira, incidence was low, with only a few plants showing symptoms, but severity was moderate, with some leaves per plant exhibiting partial or nearly total coverage by pustules. Microscopic examination of pustules revealed the presence of urediniospores and teliospores. Urediniospores were subglobose, ovoid or piriform, echinulate, 25 to 37 × 18 to 27 μm, with two equatorial pores. Teliospores were clavate to cylindrical, with rounded apex, frequently slightly constricted at the sept, palebrown, 43 to 67 × 15 to 18 μm, with a short pedicel, matching the description of Puccinia thaliae Dietel (Sivanesan 1970). Infected plant material was stored in the fungal collection of the João de Carvalho e Vasconcelos herbarium (LISI-Fungi) under Accession Nos. LISIQuick Links Add to favorites E-mail to a colleague Alert me when new articles cite this article Download to citation manager Related articles found in APS Journals Article History Print: 6 May 2016 Ahead of Print: 22 Mar 2016 First Look: 19 Jan 2016 Accepted: 9 Jan 2016 First Report of Puccinia thaliae Causing Rust on Canna spp. in Europe — Plant Disease http://apsjournals.apsnet.org/doi/full/10.1094/PDIS-12-15-1404-PDN[27-10-2016 11:36:02] Fungi-00049 and LISI-Fungi-00057 (for Azores and Madeira material, respectively). For the fulfillment of Koch’s postulates, the lower leaf surface of healthy Canna × hybrida plants was inoculated by rubbing a piece of an infected leaf with sporulating urediniospore masses. Inoculated plants were sprayed with sterile water, maintained in a wet chamber under darkness for 24 h at approximately 20°C, and left under glasshouse conditions until appearance of symptoms. Chloroses were visible one week after inoculation and uredinia were observed 15 to 18 days after inoculation. Symptoms and the morphology of urediniospores were similar to those observed in field infections. Canna is a monocotyledonous genus in the family Cannaceae originating from tropical and subtropical regions of America, with several species naturalized in other parts of the world including regions of temperate climate. Plants of Canna × hybrida are popular garden ornamentals in many parts of the world, regarded by horticulturalists as easy to cultivate and virtually disease-free. Canna rust has been reported from different areas of the Americas (Brito and Garrido 2011; Kaur et al. 2011) but also in Australasia (Jeeva et al. 2003; Neo and Tham 2009). This represents the first report of this disease in Portugal and in Europe, raising concern for its dissemination into European and North African Canna. References: Section: Brito, M., and Garrido, M. J. 2011. Fitopatol. Venez. 24:59. Jeeva, M. L., et al. 2003. New Dis. Rep. 8:24. Kaur, R., et al. 2011. Plant Dis. 95:353. 10.1094/PDIS-03-10-0209. [Abstract] [ISI] Neo, N. W., and Tham, F. Y. 2009. New Dis. Rep. 19:67. Sivanesan, A. 1970. Descriptions of Pathogenic Fungi and Bacteria, No. 267. CMI, Kew, Surrey, UK.

Hercinothrips dimidiatus Hood (Thysanoptera: Thripidae), a new pest of Aloe arborescens Miller in Europe

Hercinothrips dimidiatus Hood (Thysanoptera: Thripidae) was detected in several localities in the region of Lisbon, in Portugal, infesting Aloe arborescens Miller (Asphodelaceae) and causing considerable damage. This is the first record of this thrips in Europe and in the Palaearctic region.