Gibellula flava sp. nov. (Cordycipitaceae, Hypocreales), a new pathogen of spider from China

Gibellula is an exclusively spider-pathogen genus, with most species immediately recognized by their distinctive conidial state, but also including the teleomorphic states of these fungi that were previously included in the rejected genus Torrubiella. Two sexual specimens and an asexual morph specimen were collected from Anhui Province, China, and were recognized as the same species based on molecular evidence. Its asexual morph differs from Gibellula pulchra, to which it is morphologically similar, in having shorter verrucose conidiophores with slightly smaller metulae, phialides and conidia. Its sexual morph is characterized by producing superficial and elongate ellipsoid small perithecia with short asci on a cream-yellow mycelial mat covering the host. Multi-locus (SSU, LSU, TEF, and RPB1) phylogenetic analyses showed that the specimens belong to a strongly supported subclade, and formed a sister subclade with G. pulchra and Gibellula sp. A combination of morphological characteristics and its phylogenetic placement confirmed that these unique specimens are a new species, which is described as Gibellula flava.

Characteristics of Phomopsis juglandina (Sacc.) Hohn. Associated with Dieback of Walnut in the Climatic Conditions of Southern Romania

Phomopsis juglandina (Sacc.) Höhn., which is the conidial state of Diaporthe juglandina (Fuckel) Nitschke, and the main pathogen causing the dieback of branches and twigs of walnut was recently detected in many orchards from Romania. The symptomatological, morphological, ultrastructural, and cultural characteristics, as well as the pathogenicity of an isolate of this lignicolous fungus, were described and illustrated. The optimum periods for infection, under the conditions prevailing in Southern Romania, mainly occur in the spring (April) and autumn months (late September-beginning of October). Strong inverse correlations (p < 0.001) were found between potential evapotranspiration and lesion lengths on walnut branches in 2019. The pathogen forms two types of phialospores: alpha and beta; the role of beta phialospores is not well known in pathogenesis. In Vitro, the optimal growth temperature of mycelial hyphae was in the range of 22–26 °C, and the optimal pH is 4.4–7. This pathogen should be monitored continuously due to its potential for damaging infestations of intensive plantations.

First Report of Curvularia lunata Causing Leaf Spot on Lotus in China

Lotus (Nelumbo nucifera Gaertn.) is a flowering aquatic plant, and is widely planted as a vegetable and ornamental plant in China. In June 2011, a leaf spot was observed on lotus in Pingxiang City of Jiangxi Province, causing approximately 60% of leaves to die and leading to 10 to 15% yield loss. Initial symptoms were purple-brown spots emerging on the leaf surfaces with diameters ranging from 0.5 to 3 cm, which later developed grayish white centers and a black-brown banding pattern on the edges. Lesions often merged to form large necrotic areas, covering more than 70% of the leaf surface, which may have contributed to plant death. Small pieces (5 mm2) of symptomatic leaves were excised from the junction of diseased and healthy tissue, surface sterilized in 70% ethanol solution for 1 min and 0.1% mercuric chloride solution for 5 min, washed in three changes of sterile distilled water, and transferred to potato dextrose agar plates. Cultures were maintained in an incubator at 25°C for 5 to 7 days. After 7 days, six black-brown colonies were isolated, which developed dark brown septate conidiophores. Conidia were 20 to 25 × 9 to 13 μm, with three-horizontal septa, and curved at the third cell from the base that was longer and darker than the others. Cells at each end were subhyaline and intermediate cells were medium brown. These characteristics were consistent with Curvularia lunata (Wakker) Boedijng (1,2,4). Molecular characterization was based on rDNA sequence. For two isolates, DNA was extracted using a CTAB protocol with 0.8% mercaptoethanol, then the ITS1-5.8S-ITS2 region was amplified with primers ITS1 (5′-TCCGTAGGTGAACCTGCGG-3′) and ITS4 (5′-TCCTCCGCTTATTGATATGC-3′) (3). PCR products were cloned and sequencing reactions were run on an AB3730 Stretch DNA sequencing system. On the basis of a comparison of 598 base pairs, both isolates had the same sequence (GenBank Accession No. JQ701798), which differed by one base pair from Cochliobolus lunatus NBRC 100173 (GenBank Accession No. JN943426) (conidial state: Curvularia lunata). Pathogenicity experiments were conducted by inoculating a conidial suspension (106 CFU/ml) on five newly matured leaves of healthy lotus. Plants inoculated with sterile water served as the noninoculated controls. Plants were incubated in the greenhouse at 20 to 25°C. All the inoculated leaves started showing disease symptoms (purple flecks) after 7 days and the noninoculated control plants remained asymptomatic. C. lunata was consistently recovered from all inoculated plants, except the control, thus fulfilling Koch's postulates. To our knowledge, this is the first report of leaf spot caused by C. lunata on lotus in China. References: (1) M. B. Ellis. Dematiaceous Hyphomycetes. Commonwealth Mycological Institute, Kew, Surrey, England, 1971. (2) M. M. Hawa, et al. Plant Dis. 93: 971, 2009. (3) K. J. Martin and P. T. Rygiewicz. BMC Microbiol. 5:28, 2005. (4) F. B. Rocha et al. Austral. Plant Pathol. 33: 601, 2004.

First Report of Cane Blight on Blackberry Caused by Diaporthe eres in Croatia

A cane disease of blackberry (Rubus sp.) cv. Thornfree was observed in May and June 2010 in two growing regions in the eastern part of Slavonia in Croatia. Symptoms consisted of bleached areas between and around cane nodes with some canes showing wilt symptoms. Infected areas were covered with numerous, black pycnidia immersed in the epidermal tissue. Disease occurrence in orchards growing cv. Thornfree ranged between 1 and 15%. Thirty disease samples were collected, disinfected (1 min in 70% ethanol and 2 min in 1% NaOCl), and placed in a moist chamber for 4 days. Fungal sporulating structures were then picked off and placed on potato dextrose agar (PDA). Fungal isolates obtained were identified as a Phomopsis sp., the conidial state of Diaporthe (3), on the basis of cultural and morphological characteristics. Alpha conidia were unicellular, hyaline, fusiform, sometimes tapering toward one or both ends, biguttulate (sometimes with several guttules), and 5.2 to 9.7 × 1.4 to 2.7 μm (average 6.5 × 2.1 μm). Beta conidia were hyaline, aseptate, filiform, hamate, and 16.6 to 28.2 × 0.5 to 1.5 μm (average 24.0 × 1.1 μm). The teleomorph was not observed. Biomolecular analysis was performed to identify the fungal species by sequencing the internal transcribed spacer (ITS) region spanning ITS 1, 5.8S rDNA, and ITS 2 of two isolates (Phk1 and Phk2). The amplified product was sequenced (GenLab-Enea, Rome, Italy) and a BLAST search of the NCBI nucleotide database was performed. Sequences from Phk1 and Phk2 (GenBank Accession Nos. HQ533144 and HQ533143, respectively) were identical to authentic and vouchered Diaporthe eres Nitschke (GenBank DQ491514, BPI 748435, and CBS 109767) ITS sequences in GenBank. Fungal isolates for pathogenicity tests were grown on PDA at 25°C for 7 days (12 h light/dark regimen). Inoculations were made on 30 to 40 cm long green shoots of potted plants of the blackberry cv. Thornfree. One-centimeter long wounds were made with a sterile scalpel and mycelia of D. eres were placed in the wounds. Inoculation sites were covered with a piece of wet cotton wool and aluminum foil to retain moisture. Three replications of 10 plants each were inoculated and these plus 10 control plants (inoculated with plugs of PDA only) were maintained in a growth chamber at 25°C. After 25 days, lesions developed on all 30 inoculated plants that averaged 15 mm long and control plants remained symptomless. D. eres was reisolated from inoculated plants, thus completing Koch's postulates. Phomopsis spp. have previously been reported on blackberry canes in Serbia (1) and Yugoslavia (2,4), however, to our knowledge, this is the first report of the occurrence of D. eres (anamorph P. oblonga) on blackberry in Croatia. References: (1) M. Arsenijevic. Biljni Lekar 34:117, 2006. (2) M. Muntanola-Cvetkovic et al. Zast. Bilja 36:325, 1985. (3) B. C. Sutton. Page 569 in: The Coelomycetes. CMI, Kew, Surrey, UK, 1980. (4) M. Veselic et al. Zast. Bilja 49:76, 1998.

A new conifer-inhabiting species of Ceratocystis from Norway

A new species, Ceratocystis norvegica J. Reid & Hausner sp. nov., is described from Norway. Based on morphological criteria and analyses of rDNA internal transcribed spacer and small subunit rDNA sequences, strains collected from galleries of the bark beetle Ips typographus on Picea abies (L.) H. Karst, were shown to be distinct both from members of the Ceratocystis coerulescens complex and from other species described previously from conifers. Ceratocystis norvegica has the following defining characteristics: convergent ostiolar hyphae; a sharply defined temperature optimum at 20 °C; an apparent lack of a conidial state; and ascospores that on germination produce either self-fertile or self-sterile strains.

Powdery mildew Phyllactinia corni causing disease on Cornus mas (Cornaceae) – a new record for Slovakia

<i>Phyllactinia corni</i>, a powdery mildew on <i>Cornus mas</i>, is reported for the first time from Slovakia. The conidial state and mature cleistothecia found at two locations in Slovakia are described and illustrated.

First Report of Blueberry Botrytis Blight in Buenos Aires, Entre Ríos, and Córdoba, Argentina

Since 2003, a new field disease has been observed on several cultivars of highbush blueberry (Vaccinium corymbosum L.) in Buenos Aires (Baradero, Colonia Urquiza, Lima, Mercedes, and San Pedro), Entre Ríos (Concordia, Gualeguaychú, and Larroque), and Córdoba (Capilla del Monte and La Cumbre). Infected flowers turned brown to tan with a water-soaked appearance and shriveled up. Blighted flowers typically did not produce fruits; even an entire cluster of berries could be aborted. A chlorotic area, that later became necrotic and turned light brown, developed when leaves were in contact with blighted flowers. A watery rot developed on fruit occasionally before harvest but more generally after harvest. Infected tender green twigs also became blighted, with leaf tissue becoming brown to black. Older twigs and stems were also blighted. Abundant, gray mycelium with conidial masses developed on all affected tissues under moist conditions. Sections of infected leaves, twigs, stems, flowers, and fruits were surfaced sterilized with 0.2% NaOCl, plated on 2% potato dextrose agar (pH 7), and incubated at 22°C. Pure cultures formed a whitish dense mycelial mat and turned gray after 72 h. Conidia were ellipsoid, hyaline, nonseptate, and formed on botryose heads. They ranged from 5.8 to 9 × 8.1 to 13.7 μm (average 8.6 × 10.2 μm). Black, round, and irregular microsclerotia developed on 7-day-old cultures with an average size of 1.1 × 1.7 mm. Morphological characteristics agree with those described for Botrytis cinerea Pers.:Fr (1). Pathogenicity was tested on 10 12-month-old potted blueberry plants cv. O'Neal by spraying a suspension of 1 × 106 conidia per ml of sterile distilled water. Ten plants used as controls were sprayed with sterile distilled water. Each plant was covered with a transparent polyethylene bag for 48 h and incubated at 20 ± 2°C in humid chambers for 15 days. Lesions similar to those observed in the fields developed after 4 days and asexual fructifications developed after 5 days. The same pathogen was reisolated from the lesions, thus completing Koch's postulates. Water-treated plants remained symptomless. To our knowledge, this is the first report of a disease caused by B. cinerea on blueberry in Buenos Aires, Córdoba, and Entre Ríos provinces of Argentina. References: (1) M. V. Ellis and J. M. Waller. Sclerotinia fuckeliana (conidial state: Botrytis cinerea) No. 431 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1974.

Curvularia Blight on Lolium perenne on Turfgrasses in Argentina

Lolium perenne L. is commonly used alone or in association with blue-grass and fescues in sport fields, parks, and gardens. During 2003, symptoms of an unknown disease were observed on L. perenne turfgrass in western Buenos Aires. Initial symptoms were indefinite yellow and green dappled spots that extended downward from the leaf tip, turned brown and finally gray, causing leaf death. Segments of symptomatic leaf tissues were surface sterilized and placed on 2% potato dextrose agar in petri dishes. After 4 days at room temperature, blackish brown colonies developed with dark brown septate conidiophores. Conidia were 21 to 29 × 9 to 13 μm, 3-septa, curved at the third cell from the base that is longer and darker than the others. Cells at each end are subhyaline and intermediate cells are medium brown. These characteristics are consistent with Curvularia lunata (Wakker) Boedijng (1). Pathogenicity tests were performed in five plastic trays with substrate of natural soil and sand (1:1 [v/v]) where the turfgrass (L. perenne cv. El Cencerro) was seeded. Plants were inoculated by spraying a suspension of 2 × 106 conidia per ml of sterile distilled water. Controls were sprayed with sterile distilled water. The trays were covered with transparent plastic bags, sprayed periodically with water, and incubated at 25°C in a greenhouse for 20 days. The first symptoms were observed 3 days later. After 9 days, 24% of the grass surface area showed blight lesions. C. lunata was consistently reisolated from affected tissues. Control plants remained symptomless. To our knowledge, this is the first report of C. lunata affecting L. perenne in Argentina. Reference: (1) M. B. Ellis and I. A. S. Gibson Cochliobolus lunatus (conidial state: Curvularia lunata). Page 474 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1975.

First Report of Powdery Mildew Caused by Podosphaera leucotricha on Prunus africana in Kenya

Prunus africana, formerly known as Pygeum africanum, is widely distributed in moist, tropical Africa and produces durable timber. Extracts from its bark are used in treatment of prostate disorders. Powdery mildew was observed on nursery-grown seedlings of P. africana in Kenya (Nyeri, Kiambu, and Kericho districts) in the dry seasons of 1998, 1999, and 2000. White ectotrophic mycelial growth was observed on leaves. The fungus caused stunting, distortion of leaves, surface necrosis of invaded tissues, and general decline in growth of seedlings that led to premature leaf fall and death. Invaded leaflets wilted and dropped, leaving behind a bare stem. The primary mycelium was hyaline, with no secondary brown mycelium. The conidial state was conspicuous, with conidia produced in chains. Appressoria were unlobed and nipple shaped. Conidiophores were straight and three-celled, measuring 75 to 112 μm. Conidiophore foot cells were topped by a longer cell and one or two shorter cells measuring 35 to 77 μm. Conidia had fibrosin bodies, were ovoid, and measured 27 to 30 × 17 to 18 μm. The fungus was identified by the International Mycological Institute IMI (W6496) as Podosphaera leucotricha (Ellis & Everh.) E. S. Salmon. Infected leaves of P. africana were deposited at the East African Herbarium, National Museums of Kenya (Accession No. KM-KEFRI/446/2001). Pathogenicity was confirmed by inoculating seedlings of P. africana by gently pressing infected leaves with abundant sporulation onto healthy leaves. The plants were then incubated under moist conditions for 48 h and thereafter maintained in a glasshouse. After 15 days, powdery mildew symptoms developed on seedlings. Examination of leaves confirmed that they were infected with Podosphaera leucotricha. Uninoculated control plants were free of powdery mildew. To our knowlege, this is the first report of Podosphaera leucotricha as a pathogen of P. africana. Reference: 1. H. J. Boesewinkel. Bot. Rev. 46:167, 1980.