First Report of Diplodia seriata as Causal Agent of Olive Dieback in Croatia

In August 2010, a dieback of young olive (Olea europea L.) trees (cvs. Pendolino and Leccino) occurred in two orchards in Istria, Croatia. According to the producers, low temperatures during the winter severely damaged the plants and led to their decline. Distinctive symptoms, assumed fungal infection, were observed in internal tissue of stems and branches. Elongated brown necrosis, sometimes with black streaks, was visible under the bark, therefore Verticillium wilt was suspected. Of 1,086 trees in two orchards (4 ha), 165 (15%) showed symptoms. To isolate the causal agent, surface-sterilized wood chips of symptomatic tissue were placed on potato dextrose agar (PDA). Fungal colonies resembling Botryosphaeriaceae spp. grew from all wood fragments placed on PDA, and from these colonies, monohyphal isolates were obtained. For morphological identification, pycnidial formation was stimulated by growing the isolates on 2% water agar that included stems of plant species Foeniculum vulgare Mill. at room temperature under diffuse light. Pycnidia contained conidia that initially showed as hyaline, becoming light to dark brown as they matured, ovoid with truncated or rounded base and obtuse apex, aseptate, with wall moderately thick, externally smooth, roughened on the inner surface, and 22.8 to 23.5 × 9.6 to 10.5 μm. On the basis of these morphological characters, fungal species Diplodia seriata (teleomorph “Botryosphaeria” obtusa) was suspected (3). For molecular identification, four isolates (MN3, MN4, MN5, and MN6) were used for PCR to amplify the internal transcribed spacer (ITS) region and partial translation elongation factor 1-alpha (EF1-α) gene, using primers ITS4/ITS5 and EF1-728F/EF1-986R, respectively. Sequencing was performed with those amplified genes, then sequences were deposited in GenBank. Comparison of these sequences with GenBank sequences for referent D. seriata isolate CBS 112555 (AY259094 and AY573220) (3) showed 100% homology. On the basis of molecular data, the isolates were confirmed to be species D. seriata De Not. Pathogenicity tests were performed by inoculation of 2-year-old olive plants, six plants per tested cultivar (Pendolino and Leccino). For every cultivar, four plants were wounded and mycelium plugs from D. seriata cultures on PDA were placed on the wounds and sealed with Parafilm. Two control plants per tested cultivar were inoculated with sterile PDA plugs. After 2 months, six of eight inoculated plants wilted completely, and under the bark, brown necrosis was observed. D. seriata was constantly reisolated from the inoculated plants and fulfilled Koch's postulates and confirmed pathogenicity of D. seriata on olive as causal agent of olive dieback. Control plants showed no symptoms of the disease. This fungus has been recognized as the cause of fruit rot of olive (1) and branch canker or dieback in Spain (2). To our knowledge, this is the first report of D. seriata as a pathogen of olive in Croatia. Also, this is one of the first reports of D. seriata as the cause of olive dieback in the world, while Moral et al. (1,2) mostly reported it as the cause of olive fruit rot. Since the same symptoms of olive dieback were observed at other localities in Croatia, the disease could represent a serious threat, particularly for young olive orchards. References: (1) J. Moral et al. Plant Dis. 92:311, 2008. (2) J. Moral et al. Phytopathology 100:1340, 2010. (3) A. J. L. Phillips et al. Fungal Divers. 25:141, 2007.

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First Report of Fruit Rot of Melon Caused by Fusarium asiaticum in China

Plant Disease ◽

10.1094/pdis-08-20-1857-pdn ◽

2020 ◽

Author(s):

Fangmin Hao ◽

Quanyu Zang ◽

Weihong Ding ◽

Erlei Ma ◽

Yunping Huang ◽

...

Keyword(s):

Disease Incidence ◽

Elongation Factor ◽

Morphological Characteristics ◽

Its Region ◽

Fruit Rot ◽

Post Inoculation ◽

Basal Cells ◽

First Report ◽

Fusarium Asiaticum ◽

Sterile Needle

Melon (Cucumis melo L.) is a member of the Cucurbitaceae family, an important economical and horticultural crop, which is widely grown in China. In May 2020, fruit rot disease with water-soaked lesions and pink molds on cantaloupe melons was observed in several greenhouses with 50% disease incidence in Ningbo, Zhejiang Province in China. In order to know the causal agent, diseased fruits were cut into pieces, surface sterilized for 1 min with 1% sodium hypochlorite (NaClO), 2 min with 75% ethyl alcohol, rinsed in sterile distilled water three times (Zhou et al. 2018), and then placed on potato dextrose agar (PDA) medium amended with streptomycin sulfate (100 μg/ml) plates at 25°C for 4 days. The growing hyphae were transferred to new PDA plates using the hyphal tip method, putative Fusarium colonies were purified by single-sporing. Twenty-five fungal isolates were obtained and formed red colonies with white aerial mycelia at 25°C for 7 days, which were identified as Fusarium isolates based on the morphological characteristics and microscopic examination. The average radial mycelial growth rate of Fusarium isolate Fa-25 was 11.44 mm/day at 25°C in the dark on PDA. Macroconidia were stout with curved apical and basal cells, usually with 4 to 6 septa, and 29.5 to 44.2 × 3.7 to 5.2 μm on Spezieller Nährstoffarmer agar (SNA) medium at 25°C for 10 days (Leslie and Summerell 2006). To identify the species, the internal transcribed spacer (ITS) region and translational elongation factor 1-alpha (TEF1-α) gene of the isolates were amplified and cloned. ITS and TEF1-α was amplified using primers ITS1/ITS4 and EF1/EF2 (O’Donnell et al. 1998), respectively. Sequences of ITS (545 bp, GenBank Accession No. MT811812) and TEF1-α (707 bp, GenBank Acc. No. MT856659) for isolate Fa-25 were 100% and 99.72% identical to those of F. asiaticum strains MSBL-4 (ITS, GenBank Acc. MT322117.1) and Daya350-3 (TEF1-α, GenBank Acc. KT380124.1) in GenBank, respectively. A phylogenetic tree was established based on the TEF1-α sequences of Fa-25 and other Fusarium spp., and Fa-25 was clustered with F. asiaticum. Thus, both morphological and molecular characterizations supported the isolate as F. asiaticum. To confirm the pathogenicity, mycelium agar plugs (6 mm in diameter) removed from the colony margin of a 2-day-old culture of strain Fa-25 were used to inoculate melon fruits. Before inoculation, healthy melon fruits were selected, soaked in 2% NaClO solution for 2 min, and washed in sterile water. After wounding the melon fruits with a sterile needle, the fruits were inoculated by placing mycelium agar plugs on the wounds, and mock inoculation with mycelium-free PDA plugs was used as control. Five fruits were used in each treatment. The inoculated and mock-inoculated fruits were incubated at 25°C with high relative humidity. Symptoms were observed on all inoculated melon fruits 10 days post inoculation, which were similar to those naturally infected fruits, whereas the mock-inoculated fruits remained symptomless. The fungus re-isolated from the diseased fruits resembled colony morphology of the original isolate. The experiment was conducted three times and produced the same results. To our knowledge, this is the first report of fruit rot of melon caused by F. asiaticum in China.

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First Report of Web Blight on Oregano (Origanum vulgare L.) Caused by Rhizoctonia solani AG-1-IB in Italy

Plant Disease ◽

10.1094/pdis-02-13-0138-pdn ◽

2013 ◽

Vol 97 (8) ◽

pp. 1119-1119 ◽

Cited By ~ 2

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

P. Pensa ◽

A. Poli ◽

M. L. Gullino

Keyword(s):

Rhizoctonia Solani ◽

Its Region ◽

Morphological Characters ◽

Anastomosis Group ◽

Morphological Identification ◽

Pathogenicity Test ◽

Origanum Vulgare ◽

First Report ◽

Plastic Bags ◽

Hyphal Diameter

Origanum vulgare L., common name oregano, family Labiatae, is grown for its aromatic and medicinal properties and as ornamental. In the fall of 2012, a blight was observed in a farm located near Albenga (northern Italy) on 6% of 30,000 50-day-old plants, grown in trays in a peat/perlite mix. Semicircular, water soaked lesions appeared on leaves and stems, starting from the basal ones. As the disease progressed, blighted leaves turned brown, withered, clung to the shoots, and matted on the surrounding foliage. Eventually, infected plants died. Leaf and stem fragments taken from the margin of the diseased tissues belonging to 10 plants were disinfected for 10 s in 1% NaOCl, rinsed with sterile water, and plated on potato dextrose agar (PDA). A fungus with the morphological characters of Rhizoctonia solani was consistently recovered. Three isolates of R. solani obtained from affected plants were successfully anastomosed with R. solani isolate AG 1 (ATCC 58946). Three pairings were made for each tester strain. The hyphal diameter at the point of anastomosis was reduced, the anastomosis point was obvious, and death of adjacent cells was observed. Results were consistent with other reports on anastomosis reactions (2). Isolates from oregano were paired with R. solani isolates AG 2, 3, 4, 6, 7, or 11 and examined microscopically. Anastomosis was not observed in any of the pairings. Tests were conducted twice. Mycelium of 10-day-old isolates from oregano appeared reddish brown, coarse, and radiate. Numerous dark brown sclerotia, 0.3 to 1.0 mm diameter (average 0.7) developed within 10 days after transfer of mycelia to PDA in 90 mm diameter petri dishes at 21 to 24°C. The descriptions of mycelium and sclerotia were typical for subgroup IB Type 1 (4). The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS1/ITS4 and sequenced. BLASTn analysis (1) of the 538 bp showed a 99% homology with the sequence of R. solani FJ746937, confirming the morphological identification of the species. The nucleotide sequence has been assigned the GenBank Accession KC493638. For pathogenicity tests, one of the isolates assigned to the anastomosis group AG-1-IB was tested by placing 9 mm diameter mycelial disks removed from PDA 10-day-old cultures of the fungus on leaves of 90-day-old oregano plants (n = 35). Thirty-five plants inoculated with non-inoculated PDA disks served as controls. Plants were covered with plastic bags and maintained in a growth chamber at 25 ± 1°C with 12 h light/dark. The first symptoms, similar to those observed in the farm, developed 3 days after inoculation. Nine days after the artificial inoculation, 50% of plants were dead. About 10 colonies of R. solani were reisolated from infected leaves of inoculated plants. Control plants remained healthy. The pathogenicity test was carried out twice with similar results. Symptoms caused by R. solani have been recently observed on O. vulgare in Greece (3). This is, to our knowledge, the first report of blight of O. vulgare caused by R. solani in Italy. References: (1) S. F. Altschul et al. Nucleic Acids Res., 25:3389, 1997. (2) D. E. Carling. Grouping in Rhizoctonia solani by hyphal anastomosis reactions. In: Rhizoctonia Species: Taxonomy, Molecular Biology, Ecology, Pathology and Disease control. Kluwer Academic Publishers, The Netherlands, pp. 37-47, 1996. (3) C. D. Holevas et al. Benaki Phytopathol. Inst., Kiphissia, Athens, 19:1-96, 2000. (4) R. T. Sherwood. Phytopathology 59:1924, 1969.

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First Report of Brown Rot Caused by Monilinia fructicola on Nectarine in Serbia

Plant Disease ◽

10.1094/pdis-08-12-0718-pdn ◽

2013 ◽

Vol 97 (1) ◽

pp. 147-147 ◽

Cited By ~ 9

Author(s):

J. Hrustić ◽

M. Mihajlović ◽

B. Tanović ◽

G. Delibašić ◽

I. Stanković ◽

...

Keyword(s):

Prunus Persica ◽

Its Region ◽

Fruit Rot ◽

Economic Losses ◽

Morphological Identification ◽

Single Spore ◽

Daily Growth ◽

Causal Organism ◽

First Report ◽

Apple Fruits

In August 2011, nectarine (Prunus persica (L.) Batsch var. nucipersica (Suckow) C. K. Schneid) fruit originated from Oplenac region with symptoms of fruit rot was collected at a green market in Belgrade. Fruit had large, brown, sunken lesions covered with grayish brown tufts. Symptoms resembled those caused by species of Monilinia including M. laxa, M. fructigena, or M. fructicola (2). In order to isolate the causal organism, small superficial fragments of pericarp were superficially disinfected with commercial bleach and placed on potato dextrose agar (PDA). The majority (32 out of 33) isolates formed rosetted non-sporulating colonies with lobed margins resembling those of M. laxa. However, one isolate (Npgm) produced an abundant, grayish-white colony with even margins and concentric rings of sporogenous mycelium, resembling those described for M. fructicola (2). Conidia were one-celled, hyaline, ellipsoid to lemon shaped, 7.38 to 14.76 × 4.92 to 9.84 μm, and borne in branched monilioid chains. The average daily growth on PDA at 24°C was 10.9 mm. A single-spore isolate of Npgm was identified as M. fructicola based on the morphology of colony and conidia, temperature requirements, and growth rate (2). Morphological identification was confirmed by an amplified product of 535 bp using genomic DNA extracted from the mycelium of pure culture and species-specific PCR for the detection of M. fructicola (2). The ribosomal internal transcribed spacer (ITS) region of rDNA of Npgm was amplified and sequenced using primers ITS1/ITS4. Sequence analysis of ITS region revealed 100% nucleotide identity between the isolate Npgm (GenBank Accession No. JX127303) and 17 isolates of M. fructicola from different parts of the world, including four from Europe (FJ411109, FJ411110, GU967379, JN176564). Pathogenicity of the isolate Npgm was confirmed by inoculating five surface-disinfected mature nectarine and five apple fruits by placing a mycelial plug under the wounded skin of the fruit. Nectarine and apple fruits inoculated with sterile PDA plugs served as a negative controls. After a 3-day incubation at 22°C, inoculated sites developed brown lesions and the pathogen was succesfully reisolated. There were no symptoms on the control nectarine or apple fruits. M. fructicola is commonly present in Asia, North and South America, New Zealand, and Australia, while in the EPPO Region the pathogen is listed as an A2 quarantine organism (3). In Europe, the first discovery of M. fructicola was reported in France and since then, it has been found in Hungary, Switzerland, the Czech Republic, Spain, Slovenia, Italy, Austria, Poland, Romania, Germany, and Slovakia (1). Most recently, M. fructicola was found on stored apple fruits in Serbia (4). To our knowledge, this is the first report of M. fructicola decaying peach fruit in Serbia. These findings suggest that the pathogen is spreading on its principal host plants and causing substantial economic losses in the Serbian fruit production. References: (1) R. Baker et al. European Food Safety Authority. Online publication. www.efsa.europa.eu/efsajournal . EFSA J. 9:2119, 2011. (2) M. J. Côté. Plant Dis. 88:1219, 2004. (3) OEPP/EPPO. EPPO A2 list of pests recommended for regulation as quarantine pests. Version 2009-09. http://www.eppo.org/QUARANTINE/listA2.htm . (4). M. Vasic et al. Plant Dis. 96:456, 2012.

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First Report of Leaf Spot Caused by Phoma dictamnicola on Dictamnus dasycarpus in Korea

Plant Disease ◽

10.1094/pdis-06-14-0658-pdn ◽

2014 ◽

Vol 98 (10) ◽

pp. 1443-1443

Author(s):

J. H. Park ◽

S. E. Cho ◽

C. K. Lee ◽

S. H. Lee ◽

H. D. Shin

Keyword(s):

Leaf Spot ◽

Its Region ◽

Molecular Data ◽

Culture Collection ◽

Morphological Identification ◽

Conidial Suspension ◽

Aesthetic Value ◽

Transparent Plastic ◽

First Report ◽

Plastic Bags

Dictamnus dasycarpus Turcz, known as densefruit pittany, is a perennial herbal plant belonging to the Rutaceae. In Oriental medicine, this plant is used for treatment of various ailments (4). Since the white and purple striped flowers and glossy leaves are of aesthetic value, the plant is popular in gardens throughout Korea. In July 2012, a leaf spot was observed on hundreds of D. dasycarpus with nearly 100% incidence in a garden in Gapyeong County, Korea. Lesions on leaves reaching up to 20 mm in diameter were circular to irregular, brown to dark brown, then becoming zonate with age, and finally fading to grayish brown in the center with a reddish brown margin. The disease caused premature defoliation and reduced plant vigor as well as aesthetic value. In June 2014, the same symptoms were found on D. dasycarpus in a nursery in Jinju City, Korea. Representative samples were deposited in the Korea University Herbarium (KUS). Pycnidia on lesions were epiphyllous, immersed or semi-immersed in host tissue, light brown to olive brown, and 90 to 210 μm in diameter. Ostioles were 15 to 30 μm wide and surrounded by a ring of darker cells. Conidia were hyaline, smooth, ellipsoidal to nearly reniform, straight to mildly curved, aseptate or rarely medianly 1-septate with age, 5.5 to 9.6 × 1.8 to 3.6 μm, and contained small oil drops. These characteristics were consistent with the previous descriptions of Phoma dictamnicola Boerema, Gruyter & Noordel. (1,2). A monoconidial isolate was cultured on potato dextrose agar plates and deposited in the Korea Agricultural Culture Collection (Accession No. KACC46948). Morphological identification of the fungus was confirmed by molecular data. Genomic DNA was extracted using a DNeasy Plant Mini Kit (Qiagen Inc., Valencia, CA). The internal transcribed spacer (ITS) region of rDNA was amplified using the ITS1/ITS4 primers and sequenced. The resulting sequence of 505 bp was deposited in GenBank (Accession No. KM047023). A BLAST search showed that the ITS sequence shared >99% similarity with that of P. dictamnicola (GU237877). For the pathogenicity tests, inoculum was prepared by harvesting conidia from 30-day-old cultures of KACC46948 and a conidial suspension (2 × 106 conidia/ml) was sprayed onto leaves of five healthy seedlings. Five seedlings were sprayed with sterile distilled water, serving as controls. The plants were covered with transparent plastic bags for 48 h in a 25°C glasshouse with a 12-h photoperiod. After 10 days, typical leaf spot symptoms started to develop on the leaves of the inoculated plants. The fungus, P. dictamnicola, was re-isolated from those lesions, confirming Koch's postulates. No symptoms were observed on control plants. Previously, Phoma leaf spot on Dictamnus spp. has been reported in the Netherlands and North America (3) and recently in China (1). To our knowledge, this is the first report of leaf spot on D. dasycarpus caused by P. dictamnicola in Korea. Our observations suggest that low humidity with good ventilation as well as removal of infected leaves and plant debris might be main strategies for preventing this disease. References: (1) Q. Bai et al. Plant Dis. 95:771, 2011. (2) G. H. Boerema et al. Phoma Identification Manual: Differentiation of Specific and Infra-Specific Taxa in Culture. CABI Publishing. Wallingford, UK, 2004. (3) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab., Online publication, USDA ARS, Retrieved June 19, 2014. (4) J. L. Yang et al. Planta Med. 77:271, 2011.

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First Report of Gliocephalotrichum bulbilium Causing Fruit Rot of Posthavest Mangosteen in China

Plant Disease ◽

10.1094/pdis-09-13-0917-pdn ◽

2014 ◽

Vol 98 (7) ◽

pp. 994-994 ◽

Cited By ~ 1

Author(s):

Y. X. Li ◽

W. X. Chen ◽

A. Y. Liu ◽

Q. L. Chen ◽

S. J. Feng

Keyword(s):

Its Region ◽

The United States ◽

Psidium Guajava ◽

Morphological Characters ◽

Fruit Rot ◽

Diseased Plant ◽

Garcinia Mangostana ◽

Single Spore ◽

Tropical Fruit ◽

First Report

Mangosteen (Garcinia mangostana L., Guttiferae) is a tropical fruit renowned for its pleasant taste, rich nutrition, and medicinal value. Little research about mangosteen diseases during storage and transport has been reported. In June of 2012, fruit rots on mangosteens imported from Thailand were observed in Guangzhou, China. In infected fruits, pericarps showed an increased firmness, were discolored to deep pink, and the edible aril became brown and rotten. In order to search for the etiological agent of this rot symptom, infected mangosteens were analyzed. Diseased mangosteen tissues were surface-sterilized with 70% alcohol, then with 0.1% HgCl2, dipped in sterilized water three times, and placed onto potato dextrose agar (PDA) at 26°C. The fungi isolated from tissues of the pericarp and aril were similar in morphology and grew rapidly, covering the plate surface (9 mm diameter) after 2 to 3 days of incubation at 26°C. The morphological characters of 10 single-spore isolates were observed. These isolates showed light yellow to light brown fertile colonies on PDA. On corn meal agar (CMA), conidiophores were erect, arising from wide hyphae; they were composed of a basal stipe ending in a penicillate conidiogenous apparatus with directly subtending sterile stipe extensions ranging from 74.5 to 195.0 μm long. Conidia were unicellular, smooth, oblong to elliptical, 6.3 to 8.5 × 2.5 to 3.0 μm, and accumulated in a mucilaginous mass. Chlamydospores were multicellular, dark brown, regular in shape and thick-walled, and 40.0 to 52.5 μm in diameter. On the basis of these morphological characters, these isolates were identified as Gliocephalotrichum bulbilium (2). To confirm the identity of this fungus, genomic DNA of two isolates was extracted, and fragments of ITS region and β-tubulin gene were amplified by PCR, sequenced, and compared with sequences of Gliocephalotrichum species available in NCBI GenBank. Both DNA regions (GenBank Accession Nos. KF716166 and KF716168) had sequence similarities of 99% and 97%, respectively, to other G. bulbilium sequences at GenBank. Pathogenicity tests were conducted on three detached fruits for two isolates. Fruits were inoculated using 5-mm mycelial disks with conidia taken from 3-day-old cultures of G. bulbilium isolate Gb1 and Gb10 grown on PDA. Controls were inoculated with PDA disks only. All treated fruits were kept individually in a humid chamber at 26°C. Tests were repeated twice. Three days after inoculation, white mycelial growth for Gb was observed at inoculation sites. Eight days after inoculation, mycelium of Gb nearly covered the fruit, causing fruit rot, and the pericarp became hard and light in color. The control fruit did not rot. G. bulbilium was re-isolated from diseased plant tissue, thus fulfilling Koch's postulates. G. bulbilium has been reported causing postharvest fruit rot of rambutan (Nephelium lappaceum) and guava (Psidium guajava) in some locations (3,4). Moreover, the fungus caused cranberry fruit rot in the United States (1). To our knowledge, this is the first report of G. bulbilium causing postharvest fruit rot of mangosteen in China. It is uncertain whether the fungus infected mangosteen in Thailand and was carried to China due to commercial relationship. References: (1) C. Constantelos et al. Plant Dis. 95:618, 2011. (2) C. Decock et al. Mycologia 98:488, 2006. (3) L. M. Serrato-Diaz et al. Plant Dis. 96:1225, 2012. (4) A. Sivapalan et al. Australas. Plant Pathol. 27:274, 1998.

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First Report of Stemphylium vesicarium as Causal Agent of Wilting and Root Rotting of Radish Sprouts in Italy

Plant Disease ◽

10.1094/pdis-92-4-0651c ◽

2008 ◽

Vol 92 (4) ◽

pp. 651-651 ◽

Cited By ~ 3

Author(s):

A. Belisario ◽

S. Vitale ◽

L. Luongo ◽

S. Nardi ◽

S. Talevi ◽

...

Keyword(s):

Its Region ◽

Mediterranean Area ◽

Morphological Characters ◽

Causal Agent ◽

Brown Spot ◽

Stemphylium Vesicarium ◽

First Report ◽

Radish Sprouts ◽

Pleospora Allii ◽

Artificial Inoculations

A consistent contamination from a Stemphylium sp. was detected on radish (Raphanus sativus) seeds by a seed blotter test. Twenty-five percent of seed lots were contaminated. Stemphylium vesicarium (teleomorph Pleospora allii) was identified on the basis of morphological characters of conidia and conidiophores (4). Conidia were golden brown to dark drown, oblong to oval with one to four transverse and one to three longitudinal septa, constricted at one to three of the major transverse septa. Conidia dimensions ranged from 12 to 22 × 30 to 40 μm. Conidiophores were straight or occasionally one-branched with a swollen apex and one to four septate. Pseudothecia with asci and ascopores were observed on radish seeds. Asci were cylindrical to clavate with eight ascospores with up to six transverse septa and numerous longitudinal septa. Species identification was also confirmed after comparing the sequences of the internal transcribed spacer (ITS) region of rDNA and gpd (glyceraldehyde-3-phosphate dehydrogenase) (3) of four isolates with those of Stemphylium species already present in the NCBI database. Accessions Nos. AM 746020 to AM746023 and AM883174 to AM883177 were deposited for ITS and gpd, respectively. Artificial inoculations were carried out on radish seeds previously disinfected with 1% sodium hypochlorite for 10 min and then plated on S. vesicarium sporulating colonies grown on potato dextrose agar (PDA). The four sequenced isolates were tested for pathogenicity. Disinfected seeds were plated onto PDA only and used as a control. After 48 h of incubation, seeds were sown in sterilized soil in plastic plates. The emerging and the eventually dead plants were counted. Stem necrosis and root rotting developed on sprouts within the first week after sowing. On the surviving infected plantlets, wilting and death occurred on more than 70% of the plants within 4 weeks after sowing. Control plantlets obtained from disinfected seeds remained healthy. The fungus reisolated from wilted and dead plants was morphologically identical to the original isolates, thus confirming S. vesicarium as the causal agent. In Italy, this pathogen is common on asparagus (1), but it has also been reported on Allium spp., tomato, and pear. On European pear it is the causal agent of brown spot (2), a destructive disease in the Mediterranean area but also in the Netherlands and other continental European countries. On the basis of these results, seed contamination with S. vesicarium can represent a threat for the production of radish for sprout consumption. To our knowledge, this is the first report of S. vesicarium on radish plantlets in Italy. References: (1) F. Del Zan et al. L'informatore Agrario 11:95, 1989. (2) I. Llorente and E. Montesinos. Plant Dis. 90:1368, 2006. (3) B. M. Pryor and D. M. Bigelow. Mycologia 95:1141, 2003. (4) E. G. Simmons. Sydowia 38:284, 1985.

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First Report of Spencermartinsia viticola, Neofusicoccum australe, and N. parvum Causing Branch Canker of Citrus in California

Plant Disease ◽

10.1094/pdis-02-11-0092 ◽

2011 ◽

Vol 95 (6) ◽

pp. 770-770 ◽

Cited By ~ 15

Author(s):

A. O. Adesemoye ◽

A. Eskalen

Keyword(s):

Elongation Factor ◽

Its Region ◽

Morphological Characters ◽

Petroleum Jelly ◽

First Report ◽

Riverside County ◽

Multiple Species ◽

Minor Disease ◽

A Minor ◽

Factor Α

Dothiorella gummosis and canker on citrus is generally viewed as a minor disease but can result in serious decline of trees. Symptoms, mostly found on branches, include grayish-to-brown cast on cankered bark, which can extend into the xylem. Dothiorella gummosis was earlier believed to be caused by Dothiorella gregaria (2). In a continuing survey on citrus in six California counties (Fresno, Riverside, San Diego, San Luis Obispo, Tulare, and Ventura) in 2010, branch cankers were collected. Small pieces of symptomatic tissues were plated onto potato dextrose agar amended with 0.01% tetracycline (PDA-tet) and incubated at 25°C for 4 days. Fungi most frequently isolated were initially identified as Botryosphaeriaceae based on morphological characters (1,3). Total genomic DNA was PCR amplified with primers Bt2a/2b for the β-tubulin (BT); EF1-728F/986R for the elongation factor α-1 (EF); and ITS4/5 for the internal transcribed spacer ITS1-5.8S-ITS2 regions (3). Sequences were compared in a BLAST search. Spencermartinsia viticola UCP105 was isolated from cv. Parent Washington on Sour Orange rootstock in Tulare County, Neofusicoccum australe UCR1110 from cv. Satsuma in Riverside County, and N. parvum UCR1166 from cv. Meyer Lemon on Volkameriana rootstock in Ventura County. Sequences of UCP105, UCR1110, and UCR1166 have been deposited in GenBank under Accession Nos. JF271766, JF271776, and JF271780 for BT; JF271784, JF271793, and JF271796 for EF; and JF271748, JF271758, and JF271762 for the ITS regions. The sequences matched with isolates in GenBank as follows: ITS region of strain UCP105—98% match with Accession Nos. AY905556–8; BT of strain UCR1110—99% with GU251879–80; and EF of strain UCR1166—98% with GU251238. Pathogenicity tests were conducted by inoculating green shoots of healthy citrus trees similar to cultivar/rootstock from which each isolate was obtained. Fresh wounds were made on 1-year-old citrus shoots with a 3-mm cork borer, and the freshly wounded surfaces were inoculated with 3-mm mycelial plugs from 5-day-old cultures on PDA-tet. Control shoots were inoculated with sterile agar plugs and each treatment had 10 replicates. Inoculated wounds and shoot ends were covered with petroleum jelly and wrapped with Parafilm to prevent desiccation. Shoots were incubated at 25°C in moist chambers for 4 weeks. Lesions were observed on all inoculated shoots except for the control. Mean lesion lengths were 6.4, 7.0, and 6.9 cm for UCP105, UCR1110, and UCR1166, respectively, which were significantly (P = 0.05) different from the control (0.8 cm). The three isolates were reisolated from symptomatic tissues of inoculated shoots to confirm their pathogenicity. This test was repeated and similar results were obtained. Results indicate that there are multiple species in the Botryosphaeriaceae family causing symptoms on citrus that were previously believed to be caused by D. gregaria. To our knowledge, this is the first report of S. viticola, N. australe, and N. parvum on citrus in California. References: (1) P. W. Crous et al. Stud. Mycol. 55:235, 2006. (2) V. McDonald et al. Plant Dis. 93:967, 2009. (3) B. Slippers et al. Mycologia 96:83, 2004.

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First Report of Alternaria japonica, a causal agent of black spot, on kale in South Carolina, United States

Plant Disease ◽

10.1094/pdis-01-21-0085-pdn ◽

2021 ◽

Author(s):

Anthony P. Keinath ◽

Sean M Toporek ◽

Virginia DuBose ◽

Sierra H. Zardus ◽

Justin B. Ballew

Keyword(s):

United States ◽

South Carolina ◽

Disease Incidence ◽

Elongation Factor ◽

Black Spot ◽

Its Region ◽

Causal Agent ◽

Eastern United States ◽

First Report ◽

Leaf Spots

In January 2020, charcoal gray, dull lesions were observed on leaves of organic kale (Brassica oleracea var. acephala) cv. Darkibor in two fields in Lexington County, South Carolina, the county with the most acres of leafy brassicas in the state. Leaf spots, also visible on the leaf underside, covered <5% of the leaf area. No spores were present. Portions of leaf spots from eight leaves, four per field, were cultured on one-quarter-strength potato dextrose agar (PDA/4). Eleven isolates of Alternaria spp. were recovered. Isolates ALT12 and UL3 were cultured in A. solani medium and DNA was extracted (Maiero et al. 1991). The internal transcribed spacer (ITS) region, translation elongation factor 1-alpha (tef1), RNA polymerase second largest subunit (rpb2), and Alternaria major allergen (Alt a 1) genes were amplified with the primer pairs V9G/ITS4, EF1-728F/EF1-986R, RPB2-5F2/FRPB2-7cR, and Alt-for/Alt-rev, respectively, and sequenced (Woudenberg et al. 2014). Sequences for isolates ALT12 and UL3, collected from different leaves in the same field, were identical to each other and to isolate AC97 (ITS accession number: LC440597; tef1: LC482018; rpb2: LC476803; Alt a 1: LC481628) of A. japonica Yoshii (Nishikawa and Nakashima 2020). ITS, tef1, repb2, and Alta a 1 sequences for each isolate were deposited in GenBank under the accessions MW374952, MW389653, MW389655, and MW389657 for ALT12 and MW374951, MW389652, MW389654, and MW389656 for UL3, respectively. Conidia of A. japonica (20 of ALT12, 10 of UL3) produced by 7-day-old cultures on Spezieller Nährstoffarmer Agar measured 62.1 ± 11.4 x 18.8 ± 2.2 μm (standard deviation). Median numbers of transverse and longitudinal septae were 6 (4 to 8) and 2 (1 to 3), respectively. Conidia formed singly or in chains of two. Cells were constricted around the transverse septae (Nishikawa and Nakashima 2020; Woudenburg et al. 2014). Chlamydospores were present in cultures of ALT12. ALT12 was pathogenic on kale cv. Darkibor and Winterbor inoculated in a greenhouse following procedures of Al-Lami et al. (2019). Four replicate pots with two plants each were used; plants were 6, 9, and 5 weeks old in trials 1, 2, and 3, respectively. The oldest three leaves of each plant were spray inoculated with a suspension of 5 x 105 conidia/ml; noninoculated control plants were sprayed with water. All plants were kept for 48 h at 100% RH, then moved to a bench in a greenhouse held at 21/16°C day/night temperatures. The second and third oldest leaves were rated 13 days after inoculation. Small gray or black spots developed on inoculated leaves and petioles in all trials, and on one noninoculated leaf in trial one. Disease incidence on inoculated leaves (73.1%) was greater than on noninoculated leaves (0.05%) (P<0.0001). Cultivars did not differ in susceptibility (P=0.12). Portions of lesions on inoculated leaves and portions of noninoculated leaves were cultured onto PDA/4 amended with antibiotics (Keinath 2013). A. japonica was reisolated from 46 of 50 inoculated leaf blades; 22 of 28 inoculated petioles; and 1 of 8, 0 of 8, and 0 of 7 noninoculated leaves in the three trials, respectively. Growers in South Carolina consider black spot, or Alternaria leaf spot, the most important fungal disease on organic kale. The presence of a second causal agent in addition to A. brassicae may increase disease occurrence. A. japonica previously was reported on arugula in California (Tidwell et al. 2014). This is the first report of A. japonica in the eastern United States.

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First Report of Fruit Rot on Schisandra chinensis Caused by Penicillium glabrum and P. adametzii in China

Plant Disease ◽

10.1094/pdis-08-12-0799-pdn ◽

2013 ◽

Vol 97 (2) ◽

pp. 288-288 ◽

Cited By ~ 2

Author(s):

C. Q. Chen ◽

Y. Zhi ◽

J. Gao

Keyword(s):

Its Region ◽

Causal Agent ◽

Surface Strain ◽

Fruit Rot ◽

Conidial Suspension ◽

Schisandra Chinensis ◽

Sterile Water ◽

Differential Growth ◽

First Report ◽

Sequence Identity

Schisandra (Schisandra chinensis (Turcz.) Baill) is an important medicinal herb in China, which is mainly used for treatment of insomnia and memory decay. In September 2010, rot was observed on approximately 5% of the fruits during ripening of schisandra in several orchards at Linjiang City and Ji'an City, Jilin Province. Watery spots on infected fruits of schisandra appeared at the end of ripening, and then the fruits darkened in color, shrunk, and turned soft. The surface of the lesions became covered with masses of blue-green mycelium, conidiophores, and conidia under high humidity. To isolate the causal agent, conidia and conidiophores were suspended in sterile water and streaked onto the surface of potato dextrose agar (PDA). Single hyphal tips were then transferred to new PDA plates to be purified. The isolates were then cultured on CYA (Czapek yeast extract agar) and two kinds of strains (wwzqm1 and wwzqm2) were established based on differential growth rate, microscopic features, and colony color. Pathogenicity of each strain was tested on 25 healthy mature fruits of schisandra cv. Red Pearl by inoculating the fruit surface with a 15 μl conidial suspension (106 conidia/ml). Control fruits were treated with sterile water. Fruits were kept at 25°C and 90% relative humidity. After a 5-day incubation, symptoms described above were observed on all inoculated fruits, whereas all control fruits were symptomless. The causal agent was reisolated, confirming Koch's postulates. Strain wwzqm1 was identified as Penicillium glabrum (Wehmer) Westling on the basis of its morphology. Conidiophores arose from basal hyphae, with stipes smooth or finely roughened, 50.5 to 300.0 × 2.5 to 3.5 μm, penicillus monoverticillate, and bearing verticils of 8 to 12 phialides. Conidia were globose to subglobose, approximately 2.9 to 3.5 μm in diameter, with smooth or nearly smooth walls, and conidial chains in compact columns. Colonies grown for 7 days on CYA at 25°C attained a diameter of 32.4 to 39.1 mm, with the center of a deep bluish green, plane, velutinous, and heavily sporulated. Margin mycelium of the colony was white, with a yellowish brown under surface. Strain wwzqm2 was identified as P. adametzii K. M. Zalessky according to its morphological features with conidiophores born from funicolose hyphae, stipes smooth, 10.2 to 20.1 × 1.5 to 2.5 μm, penicillus monoverticillate, and bearing verticils of 4 to 6 phialides. Conidia were nearly globose to glubose, 2.0 to 2.7 μm in diameter, with smooth or finely roughened walls, and conidial chains loose and irregular. Colonies on CYA at 25°C for 7 days grew rather fast and reached a diameter of 50.3 to 60.2 mm, and were deep grayish green, near plane, floccose or funicolose, and heavily sporulated. Margin mycelium of the colony was white with a yellowish brown under surface (1). The internal transcribed spacer (ITS) region of ribosomal DNA (rDNA) was amplified for wwzqm1 and wwzqm2 using primers ITS4/ITS5 and sequenced. BLASTn analysis of the 595 bp wwzqm1 (GenBank Accession No. JN887323) amplicon had 99% sequence identity with P. glabrum (DQ681321) and the 568 bp wwzqm2 amplicon (JN887322) had 99% sequence identity with P. adametzii (AF033401). To our knowledge, this is the first report of fruit rot on S. chinensis caused by P. glabrum and P. adametzii in China. Reference: (1). H. Z. Kong. Penicillium et Teleomorphi Cognati. Flora Fungorum Sinicorum. Science Press, Beijing, 35:43, 2007.

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Phylogeny and Mycotoxin Profile of Pathogenic Fusarium Species Isolated from Sudden Decline Syndrome and Leaf Wilt Symptoms on Date Palms (Phoenix dactylifera) in Tunisia

Toxins ◽

10.3390/toxins13070463 ◽

2021 ◽

Vol 13 (7) ◽

pp. 463

Author(s):

Amal Rabaaoui ◽

Chiara Dall’Asta ◽

Laura Righetti ◽

Antonia Susca ◽

Antonio Logrieco ◽

...

Keyword(s):

Rna Polymerase Ii ◽

Fusarium Solani ◽

Fusarium Species ◽

Elongation Factor ◽

Phoenix Dactylifera ◽

Fusarium Proliferatum ◽

Fruit Rot ◽

Morphological Identification ◽

Single Strain ◽

Date Palms

In 2017–2018, extensive symptoms of sudden decline and fruit rot were observed on date palms in southern Tunisia. Samples of diseased plants were randomly collected in six localities. Based on morphological identification, Fusarium was the most frequent fungal genus detected. A sequencing of translation elongation factor, calmodulin, and second largest subunit of RNA polymerase II genes was used to identify 63 representative Fusarium strains at species level and investigate their phylogenetic relationships. The main species detected was Fusarium proliferatum, and at a much lesser extent, Fusarium brachygibbosum, Fusarium caatingaense, Fusarium clavum, Fusarium incarnatum, and Fusarium solani. Pathogenicity on the Deglet Nour variety plantlets and the capability to produce mycotoxins were also assessed. All Fusarium species were pathogenic complying Koch’s postulates. Fusarium proliferatum strains produced mainly fumonisins (FBs), beauvericin (BEA), and, to a lesser extent, enniatins (ENNs) and moniliformin (MON). All F. brachygibbosum strains produced low levels of BEA, diacetoxyscirpenol, and neosolaniol; two strains produced also T-2 toxin, and a single strain produced HT-2 toxin. Fusarium caatingaense, F. clavum, F. incarnatum produced only BEA. Fusarium solani strains produced MON, BEA, and ENNs. This work reports for the first time a comprehensive multidisciplinary study of Fusarium species on date palms, concerning both phytopathological and food safety issues.

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