First Report of Pestalotiopsis microspora Causing Leaf Blight of Reineckea carnea in Central China

Pink reineckia (Reineckea carnea (Andrews) Kunth) is an evergreen herbaceous perennial plant widely grown as groundcover or for medical purposes in southern China. In 2006 and 2007, severe leaf blight was observed on pink reineckia in Wuhan, China. On newly formed pink reineckia leaves, symptoms were first noted in early May as grayish to dark brown, oval or irregular-shaped lesions, 1.5 to 0.2 × 0.5 to 0.1 cm (n = 50), on the leaf margin or leaf tip. A yellowish halo surrounded each lesion. Lesions enlarged and coalesced and diseased leaves became blighted during the fall and winter. In severely infected plots, most plants became straw-colored and had to be replaced with healthy seedlings. A fungus was isolated from surface-disinfested lesions on potato dextrose agar (PDA) at a frequency of 85.7%. One of 30 isolates, designated C2, was characterized further. The fungus growing on PDA at 20°C for 14 days formed zonate white colonies and black acervular conidiomata. Conidia of the fungus aggregated on acervuli as droplets. Conidia were fusiform and 20.7 to 32.2 × 5.8 to 9.8 μm (n = 50). Each conidium had one hyaline apical cell, one hyaline basal cell, and three dark brown median cells. There were two to four hyaline filamentous appendages 8.1 to 20.4 μm long attached to each apical cell and one hyaline appendage 2.4 to 7.1 μm long attached to each basal cell. The cultural and morphological characteristics of isolate C2 matched the description for Pestalotiopsis microspora (Speg.) Batista & Peres (1,2). The internal transcribed spacer (ITS) region of the ribosomal DNA (ITS1-5.8S-ITS2) was PCR-amplified and sequenced. The ITS sequence (606 bp) for isolate C2 (GenBank Accession No. EU935587) was 100% similar to P. microspora isolates TA-57 (GenBank Accession No. AY924267) and LK32 (GenBank Accession No. DQ001002). Pathogenicity of isolate C2 was tested with the method described by Keith et al. (2). Four detached leaves were wound inoculated or inoculated without wounding with mycelia on agar plugs (4 mm in diameter; three plugs per leaf) or conidial suspensions (107 conidia per ml; 20 μl on each of three sites per leaf). Control leaves were wound inoculated with PDA or sterile water. All inoculated leaves were maintained in a moist enamel tray under fluorescent light for 7 days at 20°C. The test was performed twice. After 4 days of incubation, necrotic leaf lesions resembling symptoms that occurred in the field were observed on the wound-inoculated leaves, whereas the control leaves and C2-inoculated leaves without wounding remained healthy. Therefore, wounding was necessary for symptom development (2). A fungus was reisolated from the C2-induced leaf lesions and the morphology of colonies and conidia were identical to that for isolate C2 of P. microspora. On the basis of the results of isolations, inoculations, and fungal identification, P. microspora was determined to be the causal agent for leaf blight of pink reineckia occurring in Wuhan, China. This fungus previously has been reported as the causal agent of scab disease of Psidium guajava in Hawaii (2), decline of Torreya taxifolia in Florida (3), and leaf blight of Lindera obtusiloba in Korea (1). To our knowledge, this is the first report of the occurrence of P. microspora on R. carnea. References: (1) Y. H. Jeon et al. Plant Pathol. 56:349, 2007. (2) L. M. Keith et al. Plant Dis. 90:16, 2006. (3) M. W. Schwartz et al. Plant Dis. 80:600, 1996.

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First Report of Leaf Blight of Japanese Yew Caused by Pestalotiopsis microspora in Korea

Plant Disease ◽

10.1094/pdis-08-13-0821-pdn ◽

2014 ◽

Vol 98 (5) ◽

pp. 691-691 ◽

Cited By ~ 2

Author(s):

Y. H. Jeon ◽

W. Cheon

Keyword(s):

Dna Sequences ◽

Apical Cell ◽

Morphological Characteristics ◽

Leaf Blight ◽

Economic Damage ◽

Leaf Margin ◽

Conidial Suspension ◽

First Report ◽

Pestalotiopsis Microspora ◽

Large Trees

Worldwide, Japanese yew (Taxus cuspidata Sieb. & Zucc.) is a popular garden tree, with large trees also being used for timber. In July 2012, leaf blight was observed on 10% of Japanese yew seedling leaves planted in a 500-m2 field in Andong, Gyeongsangbuk-do Province, South Korea. Typical symptoms included small, brown lesions that were first visible on the leaf margin, which enlarged and coalesced into the leaf becoming brown and blighted. To isolate potential pathogens from infected leaves, small sections of leaf tissue (5 to 10 mm2) were excised from lesion margins. Eight fungi were isolated from eight symptomatic trees, respectively. These fungi were hyphal tipped twice and transferred to potato dextrose agar (PDA) plates for incubation at 25°C. After 7 days, the fungi produced circular mats of white aerial mycelia. After 12 days, black acervuli containing slimy spore masses formed over the mycelial mats. Two representative isolates were further characterized. Their conidia were straight or slightly curved, fusiform to clavate, five-celled with constrictions at the septa, and 17.4 to 28.5 × 5.8 to 7.1 μm. Two to four 19.8- to 30.7-μm-long hyaline filamentous appendages (mostly three appendages) were attached to each apical cell, whereas one 3.7- to 7.1-μm-long hyaline appendage was attached to each basal cell, matching the description for Pestalotiopsis microspora (2). The pathogenicity of the two isolates was tested using 2-year-old plants (T. cuspidata var. nana Rehder; three plants per isolate) in 30-cm-diameter pots filled with soil under greenhouse conditions. The plants were inoculated by spraying the leaves with an atomizer with a conidial suspension (105 conidia/ml; ~50 ml on each plant) cultured for 10 days on PDA. As a control, three plants were inoculated with sterilized water. The plants were covered with plastic bags for 72 h to maintain high relative humidity (24 to 28°C). At 20 days after inoculation, small dark lesions enlarged into brown blight similar to that observed on naturally infected leaves. P. microspora was isolated from all inoculated plants, but not the controls. The fungus was confirmed by molecular analysis of the 5.8S subunit and flanking internal transcribed spaces (ITS1 and ITS2) of rDNA amplified from DNA extracted from single-spore cultures, and amplified with the ITS1/ITS4 primers and sequenced as previously described (4). Sequences were compared with other DNA sequences in GenBank using a BLASTN search. The P. microspora isolates were 99% homologous to other P. microspora (DQ456865, EU279435, FJ459951, and FJ459950). The morphological characteristics, pathogenicity, and molecular data assimilated in this study corresponded with the fungus P. microspora (2). This fungus has been previously reported as the causal agent of scab disease of Psidium guajava in Hawaii, the decline of Torreya taxifolia in Florida, and the leaf blight of Reineckea carnea in China (1,3). Therefore, this study presents the first report of P. microspora as a pathogen on T. cuspidata in Korea. The degree of pathogenicity of P. microspora to the Korean garden evergreen T. cuspidata requires quantification to determine its potential economic damage and to establish effective management practices. References: (1) D. F. Farr and A. Y. Rossman, Fungal Databases, Syst. Mycol. Microbiol. Lab. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ (2) L. M. Keith et al. Plant Dis. 90:16, 2006. (3) S. S. N. Maharachchikumbura. Fungal Diversity 50:167, 2011. (4) T. J. White et al. PCR Protocols. Academic Press, San Diego, CA, 1990.

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First Report of Pestalotiopsis mangiferae and P. vismiae Causing Twig Dieback of Myrica rubra in China

Plant Disease ◽

10.1094/pdis-12-11-1054-pdn ◽

2012 ◽

Vol 96 (4) ◽

pp. 588-588 ◽

Cited By ~ 6

Author(s):

F. Y. Chen ◽

L. M. Lu ◽

H. Z. Ni ◽

Y. Wang ◽

Y. G. Wang ◽

...

Keyword(s):

Basal Cell ◽

Southern China ◽

Apical Cell ◽

Morphological Characteristics ◽

Fluorescent Light ◽

Water Control ◽

First Report ◽

Myrica Rubra ◽

Potted Plants ◽

Detached Leaves

Chinese bayberry (Myrica rubra Siebold & Zucc.), an evergreen fruit tree, is widely grown in southern China. In 1999, severe twig dieback was observed on M. rubra in Taizhou and it spread to several major M. Rubra-producing areas of Zhejiang covering more than 6,000 ha by 2011. Symptoms were usually observed from June to November and first appeared as chlorosis of leaves and leaf drop, followed by the formation of dark brown lesions covered with white mycelia surrounding leaf scars. The lesions can extend to the whole twig and tree causing discoloration of the xylem. In most cases, infected trees die within 1 to 4 years. Two distinct fungi totaling 46 isolates were isolated from the surface-disinfested diseased twigs and cultured on potato dextrose agar (PDA) at 28°C. An isolate of each fungus, designated as C1 and B1, was characterized further following 10 days of growth on PDA at 28°C. C1 formed zonate, white colonies and black, acervular conidiomata with the conidia aggregated on acervuli as a creamy mass. Isolate B1 formed nonzonate, white colonies and black, acervular conidiomata with the conidia aggregated on acervuli as droplets. Conidia for each isolate were fusiform with five cells; one hyaline apical cell, one hyaline basal cell, and three, dark brown median cells. Conidia ranged from 17.8 to 25.2 × 6.7 to 9.2 μm for C1 and 21.2 to 27.8 × 4.3 to 7.5 μm for B1. There were two to three hyaline, filamentous appendages (9.8 to 23.5 μm long for C1 and 10.5 to 25.5 μm long for B1) attached to each apical cell, and one hyaline appendage (3.5 to 7.2 μm long for C1 and 3.0 to 6.8 μm long for B1) attached to each basal cell. The cultural and morphological characteristics of C1 (16 isolates) matched the description for Pestalotiopsis mangiferae while B1 (27 isolates) matched the description for P. vismiae (2). The PCR-amplified and sequenced internal transcribed spacer (ITS) region of the ribosomal DNA (ITS1-5.8S-ITS2) for isolate C1 (GenBank Accession No. JQ281542) and B1 (GenBank Accession No. JQ281543) were 99 and 100% homologous to that of the P. mangiferae isolate MM 102 (GenBank Accession No. GU722595) and P. vismiae isolate xsd08116 (GenBank Accession No. FJ481027), respectively. For pathogenicity tests, nine healthy detached leaves and 12 potted plants of M. rubra were wound inoculated with sterile water (control) or conidial suspensions (105 conidia per ml; 20 μl on each site) of C1 and B1, respectively, and maintained with relative humidity of more than 90% under fluorescent light at 28°C. Tests were performed twice. Necrotic lesions, resembling those that occurred in the field, were observed on all inoculated detached leaves and 33.3% of C1 and 25% of B1 inoculated potted plants 10 and 30 days following inoculation, respectively, while the controls remained healthy. Two fungi were reisolated from the lesions with identical morphology to the initial C1 and B1 inoculums. Therefore, P. mangiferae and P. vismiae were determined to be the causal agent for twig dieback of M. rubra in China. Pestalotiopsis spp. were previously reported as pathogens of loquat (4), mango (3), and blueberry (1) causing economic loss. To our knowledge, this is the first report of twig dieback disease of M. rubra caused by P. mangiferae and P. vismiae. References: (1) J. G. Espinoza et al. Plant Dis. 92:1407, 2008. (2) Q. X. Ge et al. Flora Fungorum Sinicorum. Vol. 38, Pestalotiopsis. Science Press, Beijing, 2009. (3). Y. Ko et al. Plant Dis. 91:1684, 2007. (4). A. E. Perelló and S. Larran. Plant Dis. 83:695, 1999.

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First Report of Stemphylium botryosum Causing Leaf Blight of Kiwi in the Province Imathia, Northern Greece

Plant Disease ◽

10.1094/pdis-92-4-0650b ◽

2008 ◽

Vol 92 (4) ◽

pp. 650-650 ◽

Cited By ~ 1

Author(s):

T. Thomidis ◽

T. J. Michailides

Keyword(s):

Apical Cell ◽

Morphological Characteristics ◽

Leaf Blight ◽

Width Ratio ◽

Northern Greece ◽

Cell Width ◽

Koch’S Postulates ◽

First Report ◽

Stemphylium Botryosum ◽

Koch's Postulates

In Greece, kiwi (Actinidia deliciosa) is mostly found in the northern part of the country where approximately 440,000 ha are grown. In the summer of 2006, a Stemphylium sp. was frequently isolated from leaves of kiwi (cv. Hayward) grown in the province of Imathia. Symptomatic leaves were covered with irregular, necrotic, brown areas. Lesions had a distinct margin that, in some cases, covered a wide part of the diseased leaves. Intense symptoms were frequently observed and associated with defoliation. This Stemphylium sp. was consistently isolated from diseased leaves onto potato dextrose agar (PDA) after surface sterilization with 0.1% chlorine solution. On the basis of morphological characteristics of mycelia, dimensions (length 20 to 29 μm and width 14 to 21 μm) and mean length/width ratio (1.42 μm) of conidia, and width and apical cell width of condiophores, the fungus was identified as Stemphylium botryosum (Wallr.) (2,3) Koch's postulates were completed in the laboratory by inoculating leaves of kiwi (cv. Hayward) with an isolate of S. botryosum originated from a symptomatic leaf of a Hayward kiwi. Twenty leaves were surface sterilized by dipping them into 0.1% chlorine solution for 2 to 3 min, washing in sterile distilled water, and allowing them to dry in a laminar flow hood. A leaf was then placed into a petri plate containing a wet, sterilized paper towel. Inoculation was made by transferring a 5-mm-diameter mycelial disc from the margins of a 7-day-old culture onto the center of each leaf surface. Petri plates were closed and incubated at 25°C with 12 h of light for 6 days. Koch's postulates were satisfied when the same S. botryosum was reisolated from 100% of inoculated leaves that developed symptoms similar to those observed in the vineyards. Leaves inoculated with a PDA plug alone (with no S. botryosum) did not develop any symptoms. Previously, Alternaria alternata was reported as the causal agent of a leaf spot pathogen of kiwi (1,4). To our knowledge, this is the first report of the occurrence of S. botryosum causing leaf blight of kiwi in Greece and worldwide. This pathogen can cause a high level of defoliation in diseased plants. References: (1) L. Corazza et al. Plant Dis. 83:487, 1999. (2) M. B. Ellis. Dematiaceous Hyphomycetes. Mycology Institute. London, England, 1971. (3) E. G. Simmons. Mycologia 61:1, 1969. (4) C. Tsahouridou and C. C. Thanassoulopoulos. Plant Dis. 84:371, 2000

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First Report of Fusarium Root Rot of Stored Carrot Caused by Fusarium avenaceum in Serbia

Plant Disease ◽

10.1094/pdis-07-14-0724-pdn ◽

2015 ◽

Vol 99 (2) ◽

pp. 286-286

Author(s):

I. Stanković ◽

K. Milojević ◽

A. Vučurović ◽

D. Nikolić ◽

B. Krstić ◽

...

Keyword(s):

Root Rot ◽

Apical Cell ◽

Morphological Characteristics ◽

Fusarium Avenaceum ◽

Control Treatment ◽

Fluorescent Light ◽

Fungal Mycelium ◽

Vegetable Crops ◽

Orange Pigment ◽

First Report

Carrot (Daucus carota L. subsp. sativus (Hoffm.) Thell., Apiaceae), a widely consumed antioxidant-rich plant, is among the major vegetable crops grown in Serbia, with average annual production of 65,400 tons on approximately 7,000 ha (4). In May 2013, a severe root rot was observed on approximately 20% of cold-stored carrot roots originating from Gospođinci, South Bačka District, Serbia. Symptoms included dry rot of the collar and crown as well as large, brown to dark brown, circular, sunken lesions on the stored roots. Frequently, abundant whitish mycelium was observed covering the surface of the colonized roots. To determine the causal agent, small pieces of infected tissue were surface-disinfested with 2% NaOCl without rinsing, air-dried, and placed on potato dextrose agar. Five single-spore isolates obtained from collar and crown tissue sections, as well as nine isolates from root sections, all formed abundant, cottony white to pale salmon fungal colonies with reddish orange pigment on the reverse surface of the agar medium when grown at 25°C under 12 h of fluorescent light per day. All recovered isolates formed numerous, three- to six-septate, hyaline, needle-like, straight to slightly curved, fusoid macroconidia (30 to 80 × 4 to 5.5 μm, average 58.3 × 4.9 μm, n = 100 spores) each with a tapering apical cell. Microconidia of all isolates were generally scarce, two- to four-septate, spindle-shaped, and 15 to 35 × 3 to 5 μm (average 21.3 × 4.2 μm). Chlamydospores were not observed. Based on these morphological characteristics, the pathogen was identified as Fusarium avenaceum (Fries) Saccardo (1). The pathogenicity on carrot was tested for isolate 19-14 by inoculating each of five carrot roots surface-disinfected with 2% NaOCl, by placing a mycelial plug into the surface of a wound created with a cork borer. Carrot roots inoculated with sterilized PDA plugs served as a negative control treatment. After 5 days of incubating the roots at 25°C, root rot symptoms identical to those observed on the source carrot plants developed on all inoculated roots, and the pathogen was re-isolated from each of these roots using the same procedure descibed above. There were no symptoms on the control roots. Morphological species identification was confirmed by sequencing the translation elongation factor (EF-1α) gene (2). Total DNA was extracted directly from fungal mycelium of isolate 19-14 with a DNeasy Plant Mini Kit (Qiagen, Hilden, Germany), and PCR amplification was performed with primer pair EF-1/EF-2 (2). Sequence analysis of the EF-1α gene revealed 100% nucleotide identity of isolate 19-14 (GenBank Accession No. KM102536) with the EF-1α sequences of two F. avenaceum isolates from Canada (KC999504 from rye and JX397864 from Triticum durum). To our knowledge, this is the first report of F. avenaceum causing collar, crown, and root rots of stored carrot in Serbia. Since F. avenaceum can produce several mycotoxins, including moniliformin, acuminatopyrone, and chrysogine (3), the presence of this pathogen on stored carrots could represent a significant constraint for carrot production in Serbia, for both direct yield losses and potential mycotoxin contamination. References: (1) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual, Blackwell Publishing, London, UK, 2006. (2) K. O'Donnell et al. Proc. Natl. Acad. Sci. U.S.A. 95:2044, 1998. (3) J. L. Sorenson. J. Agric. Food Chem. 57:1632, 2009. (4) Statistical Office, Republic of Serbia. Retrieved from http://webrzs.stat.gov.rs in May 2014.

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First Report of Brown Leaf Spot of Juglans hybrid Caused by Ophiognomonia leptostyla in China

Plant Disease ◽

10.1094/pdis-05-21-0981-pdn ◽

2021 ◽

Author(s):

Chunlin Yang ◽

Feng Liu ◽

Qian Zeng ◽

Xiulan Xu ◽

Yicong Lv ◽

...

Keyword(s):

Basal Cell ◽

Leaf Spot ◽

Juglans Regia ◽

Apical Cell ◽

Morphological Characteristics ◽

Control Measures ◽

Effective Control ◽

First Report ◽

Brown Leaf Spot ◽

Brown Leaf

“Chuanzao 2” is a walnut variety derived from the hybridization of Juglans regia L. and J. sigillata Dode distributed in southwest China, where it is an economically important tree species in rural regions (Xiao et al. 2012). In April 2020, the variety in a walnut garden showed symptoms of brown leaf spot in Beishan Town (107°21′43.93″E, 31°28′12.34″N), Dazhou City in Sichuan, China, with 5% to 10% of leaves per plant affected (5 plants). Symptomatic leaves showed brown to dark brown spots (2 to 5 mm) with a dark brown to black halo and grayish-tan center. The spots were subcircular to irregular in shape, and gradually expanded and formed necrotic spots. A single conidium isolation was performed (Senanayake et al. 2020) and transferred to Potato Dextrose Agar (PDA). Five isolates were obtained from five different infected leaves. Colonies of five isolates were subcircular, erose or dentate, flat or effuse, white initially, gradually becoming yellowish with white margins, developed and fluffy aerial mycelia, and conidiogenensis was produced underneath mycelia after 25-days-incubation. Conidiogenous cells were subcylindrical to cylindrical, or irregular in shape, and hyaline. Macroconidia were lunate, reniform, hyaline, basal cell bluntly rounded, apical cell with acute end, 1-septate, rarely aseptate, sometimes slightly constricted at septum, basal cell equal or larger than apical cell, and measured 16.5 to 30.5 × 5 to 8.5 μm (mean = 23.2 × 6.3 μm, n = 50). Microconidia were not observed. These morphological characteristics resembled those of Ophiognomonia leptostyla (Fr.) Sogonov (Walker et al. 2012a). For molecular identification, genomic DNA (isolates SICAUCC 21-0008 and SICAUCC 21-0010) was extracted, and the internal transcribed spacers (ITS) region, guanine nucleotide-binding protein subunit beta (MS204) gene, and translation elongation factor 1-alpha (tef1-α) were amplified and sequenced by using the primers ITS5/ITS4 (White et al. 1990), E1F1/E5R1a (Walker et al. 2012a), and EF1-728F/EF1-1567R (Walker et al. 2012b), respectively. Phylogenetic analyses (maximum likelihood) based on a combined dataset showed 100% bootstrap support values in a clade with O. leptostyla. The sequences of ITS, MS204, and tef1-α genes were deposited in GenBank with accession numbers MW493111/MZ026300, MW495270/MZ031975, and MW495271/MZ031974, respectively. To fulfill Koch’s postulates, five healthy hybrid plants (2 to 3 years old) with 5 to 8 leaves per plant were spray inoculated with conidium suspensions (104 conidia/mL; isolate SICAUCC 21-0008) prepared from 40-days-old cultures onto the wounded sites via pin-prick inoculation. Similarly, five noninoculated plants sprayed with sterile water served as controls. Plants were placed in a growth chamber at 25℃ on a 12-h fluorescent light/dark regime and daily sprayed with sterile distilled water. After two weeks, observed symptoms were similar to those from natural infections. No disease symptoms were found on control plants. The fungus O. leptostyla was reisolated from the diseased leaves and characterized morphologically. O. leptostyla is a global pathogen and has been reported to cause the leaf spot in many walnut trees, viz. J. ailantifolia, J. californica, J. cinerea, and J. major, etc. To our knowledge, this is the first report of O. leptostyla causing brown leaf spot on Juglans hybrid (J. regia × J. sigillata) in China. The increasing risk of this pathogen in the walnut-growing areas of Sichuan Province of China needs a further exploration and outreach effort to develop effective control measures. Chunlin Yang, Feng Liu, and Qian Zeng contributed equally to this paper.

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First report of Coniella castaneicola causing leaf blight on blueberry (Vaccinium virgatum) in China

Plant Disease ◽

10.1094/pdis-05-21-1122-pdn ◽

2021 ◽

Author(s):

Jiahao Lai ◽

Guihong Xiong ◽

Bing Liu ◽

Weigang Kuang ◽

Shuilin Song

Keyword(s):

Molecular Identification ◽

Morphological Characteristics ◽

Leaf Blight ◽

Yield Potential ◽

Effective Control ◽

Economic Losses ◽

Distilled Water ◽

First Report ◽

Fungal Isolates ◽

Blight Disease

Blueberry (Vaccinium virgatum), an economically important small fruit crop, is characterized by its highly nutritive compounds and high content and wide diversity of bioactive compounds (Miller et al. 2019). In September 2020, an unknown leaf blight disease was observed on Rabbiteye blueberry at the Agricultural Science and Technology Park of Jiangxi Agricultural University in Nanchang, China (28°45'51"N, 115°50'52"E). Disease surveys were conducted at that time, the results showed that disease incidence was 90% from a sampled population of 100 plants in the field, and this disease had not been found at other cultivation fields in Nanchang. Leaf blight disease on blueberry caused the leaves to shrivel and curl, or even fall off, which hindered floral bud development and subsequent yield potential. Symptoms of the disease initially appeared as irregular brown spots (1 to 7 mm in diameter) on the leaves, subsequently coalescing to form large irregular taupe lesions (4 to 15 mm in diameter) which became curly. As the disease progressed, irregular grey-brown and blighted lesion ran throughout the leaf lamina from leaf tip to entire leaf sheath and finally caused dieback and even shoot blight. To identify the causal agent, 15 small pieces (5 mm2) of symptomatic leaves were excised from the junction of diseased and healthy tissue, surface-sterilized in 75% ethanol solution for 30 sec and 0.1% mercuric chloride solution for 2 min, rinsed three times with sterile distilled water, and then incubated on potato dextrose agar (PDA) at 28°C for 5-7 days in darkness. Five fungal isolates showing similar morphological characteristics were obtained as pure cultures by single-spore isolation. All fungal colonies on PDA were white with sparse creeping hyphae. Pycnidia were spherical, light brown, and produced numerous conidia. Conidia were 10.60 to 20.12 × 1.98 to 3.11 µm (average 15.27 × 2.52 µm, n = 100), fusiform, sickle-shaped, light brown, without septa. Based on morphological characteristics, the fungal isolates were suspected to be Coniella castaneicola (Cui 2015). To further confirm the identity of this putative pathogen, two representative isolates LGZ2 and LGZ3 were selected for molecular identification. The internal transcribed spacer region (ITS) and large subunit (LSU) were amplified and sequenced using primers ITS1/ITS4 (Peever et al. 2004) and LROR/LR7 (Castlebury and Rossman 2002). The sequences of ITS region (GenBank accession nos. MW672530 and MW856809) showed 100% identity with accessions numbers KF564280 (576/576 bp), MW208111 (544/544 bp), MW208112 (544/544 bp) of C. castaneicola. LSU gene sequences (GenBank accession nos. MW856810 to 11) was 99.85% (1324/1326 bp, 1329/1331 bp) identical to the sequences of C. castaneicola (KY473971, KR232683 to 84). Pathogenicity was tested on three blueberry varieties (‘Rabbiteye’, ‘Double Peak’ and ‘Pink Lemonade’), and four healthy young leaves of a potted blueberry of each variety with and without injury were inoculated with 20 μl suspension of prepared spores (106 conidia/mL) derived from 7-day-old cultures of LGZ2, respectively. In addition, four leaves of each variety with and without injury were sprayed with sterile distilled water as a control, respectively. The experiment was repeated three times, and all plants were incubated in a growth chamber (a 12h light and 12h dark period, 25°C, RH greater than 80%). After 4 days, all the inoculated leaves started showing disease symptoms (large irregular grey-brown lesions) as those observed in the field and there was no difference in severity recorded between the blueberry varieties, whereas the control leaves showed no symptoms. The fungus was reisolated from the inoculated leaves and confirmed as C. castaneicola by morphological and molecular identification, fulfilling Koch’s postulates. To our knowledge, this is the first report of C. castaneicola causing leaf blight on blueberries in China. The discovery of this new disease and the identification of the pathogen will provide useful information for developing effective control strategies, reducing economic losses in blueberry production, and promoting the development of the blueberry industry.

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First Report of Damping-Off Caused by Rhizoctonia solani AG-4 on Mediterranean Fan Palm in Italy

Plant Disease ◽

10.1094/pdis-94-1-0125a ◽

2010 ◽

Vol 94 (1) ◽

pp. 125-125 ◽

Cited By ~ 3

Author(s):

G. Polizzi ◽

D. Aiello ◽

I. Castello ◽

V. Guarnaccia ◽

A. Vitale

Keyword(s):

Rhizoctonia Solani ◽

Disease Incidence ◽

Morphological Characteristics ◽

Mediterranean Area ◽

Western Mediterranean ◽

Fluorescent Light ◽

Damping Off ◽

Centraalbureau Voor ◽

First Report ◽

Stem Lesions

Mediterranean fan palm (Chamaerops humilis L.), one of just two autochthonous European palms, is native to the western Mediterranean Region in southwestern Europe and northwestern Africa. It can be found growing wild in the Mediterranean area. In Europe, this species is very popular as an ornamental plant. In March 2009, a widespread damping-off was observed in a stock of approximately 30,000 potted 1-month-old plants of C. humilis cv. Vulcano in a nursery in eastern Sicily. Disease incidence was approximately 20%. Disease symptoms consisted of lesions at the seedling shoot (plumule). Stem lesions were initially orange, turned brown, and followed by death of the entire plumule or eophyll. A fungus with mycelial and morphological characteristics of Rhizoctonia solani Kühn was consistently isolated from lesions when plated on potato dextrose agar (PDA) amended with streptomycin sulfate at 100 μg/ml. Fungal colonies were initially white, turned brown with age, and produced irregularly shaped, brown sclerotia. Mycelium was branched at right angles with a septum near the branch and a slight constriction at the branch base. Hyphal cells removed from cultures grown at 25°C on 2% water agar were determined to be multinucleate when stained with 1% safranin O and 3% KOH solution (1) and examined at ×400. Anastomosis groups were determined by pairing isolates with tester strains AG-1 IA, AG-2-2-1, AG-2-2IIIB, AG-2-2IV, AG-3, AG-4, AG-5, AG-6, and AG-11 on 2% water agar in petri plates (3). Anastomosis was observed only with tester isolates of AG-4, giving both C2 and C3 reactions (2). One representative isolate obtained from symptomatic tissues was deposited at the Fungal Biodiversity Centre, Centraalbureau voor Schimmelcultures (CBS No. 125095). Pathogenicity tests were performed on container-grown, healthy, 1-month-old seedlings. Twenty plants of C. humilis cv. Vulcano were inoculated near the base of the stem with two 1-cm2 PDA plugs from 5-day-old mycelial cultures. The same number of plants served as uninoculated controls. Plants were incubated in a growth chamber and maintained at 25°C and 95% relative humidity on a 12-h fluorescent light/dark regimen. Symptoms identical to those observed in the nursery appeared 5 days after inoculation and all plants died within 20 days. No disease was observed on control plants. A fungus identical in culture morphology to R. solani AG-4 was consistently reisolated from symptomatic tissues, confirming its pathogenicity. To our knowledge, this is the first report in the world of R. solani causing damping-off on Mediterranean fan palm. References: (1) R. J. Bandoni. Mycologia 71:873, 1979. (2) D. E. Carling. Page 37 in: Grouping in Rhizoctonia solani by Hyphal Anastomosis Reactions. Kluwer Academic Publishers, the Netherlands, 1996. (3) C. C. Tu and J. W. Kimbrough. Mycologia 65:941, 1973.

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First report of banana (Musa acuminate L. AAA Cavendish, cv. Formosana) leaf spot disease caused by Curvularia geniculata in China

Plant Disease ◽

10.1094/pdis-09-21-2001-pdn ◽

2021 ◽

Author(s):

Yanxiang Qi ◽

Yanping Fu ◽

Jun Peng ◽

Fanyun Zeng ◽

Yanwei Wang ◽

...

Keyword(s):

Leaf Spot ◽

Disease Incidence ◽

Morphological Characteristics ◽

Universal Primers ◽

Leaf Spot Disease ◽

Leaf Margin ◽

Conidial Suspension ◽

Tropical Fruit ◽

First Report ◽

Spot Disease

Banana (Musa acuminate L.) is an important tropical fruit in China. During 2019-2020, a new leaf spot disease was observed on banana (M. acuminate L. AAA Cavendish, cv. Formosana) at two orchards of Chengmai county (19°48ʹ41.79″ N, 109°58ʹ44.95″ E), Hainan province, China. In total, the disease incidence was about 5% of banana trees (6 000 trees). The leaf spots occurred sporadically and were mostly confined to the leaf margin, and the percentage of the leaf area covered by lesions was less than 1%. Symptoms on the leaves were initially reddish brown spots that gradually expanded to ovoid-shaped lesions and eventually become necrotic, dry, and gray with a yellow halo. The conidia obtained from leaf lesions were brown, erect or curved, fusiform or elliptical, 3 to 4 septa with dimensions of 13.75 to 31.39 µm × 5.91 to 13.35 µm (avg. 22.39 × 8.83 µm). The cells of both ends were small and hyaline while the middle cells were larger and darker (Zhang et al. 2010). Morphological characteristics of the conidia matched the description of Curvularia geniculata (Tracy & Earle) Boedijn. To acquire the pathogen, tissue pieces (15 mm2) of symptomatic leaves were surface disinfected in 70% ethanol (10 s) and 0.8% NaClO (2 min), rinsed in sterile water three times, and transferred to potato dextrose agar (PDA) for three days at 28°C. Grayish green fungal colonies appeared, and then turned fluffy with grey and white aerial mycelium with age. Two representative isolates (CATAS-CG01 and CATAS-CG92) of single-spore cultures were selected for molecular identification. Genomic DNA was extracted from the two isolates, the internal transcribed spacer (ITS), large subunit ribosomal DNA (LSU rDNA), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), translation elongation factor 1-alpha (TEF1-α) and RNA polymerase II second largest subunit (RPB2) were amplified and sequenced with universal primers ITS1/ITS4, LROR/LR5, GPD1/GPD2, EF1-983F/EF1-2218R and 5F2/7cR, respectively (Huang et al. 2017; Raza et al. 2019). The sequences were deposited in GenBank (MW186196, MW186197, OK091651, OK721009 and OK491081 for CATAS-CG01; MZ734453, MZ734465, OK091652, OK721100 and OK642748 for CATAS-CG92, respectively). For phylogenetic analysis, MEGA7.0 (Kumar et al. 2016) was used to construct a Maximum Likelihood (ML) tree with 1 000 bootstrap replicates, based on a concatenation alignment of five gene sequences of the two isolates in this study as well as sequences of other Curvularia species obtained from GenBank. The cluster analysis revealed that isolates CATAS-CG01 and CATAS-CG92 were C. geniculata. Pathogenicity assays were conducted on 7-leaf-old banana seedlings. Two leaves from potted plants were stab inoculated by puncturing into 1-mm using a sterilized needle and placing 10 μl conidial suspension (2×106 conidia/ml) on the surface of wounded leaves and equal number of leaves were inoculated with sterile distilled water serving as control (three replicates). Inoculated plants were grown in the greenhouse (12 h/12 h light/dark, 28°C, 90% relative humidity). Necrotic lesions on inoculated leaves appeared seven days after inoculation, whereas control leaves remained healthy. The fungus was recovered from inoculated leaves, and its taxonomy was confirmed morphologically and molecularly, fulfilling Koch’s postulates. C. geniculata has been reported to cause leaf spot on banana in Jamaica (Meredith, 1963). To our knowledge, this is the first report of C. geniculata on banana in China.

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First Report of Fusarium pernambucanum Causing Fruit Rot of Muskmelon in China

Plant Disease ◽

10.1094/pdis-07-21-1520-pdn ◽

2021 ◽

Author(s):

Xianping Zhang ◽

Jiwen Xia ◽

Jiakui Liu ◽

Dan Zhao ◽

Lingguang Kong ◽

...

Keyword(s):

Phylogenetic Analyses ◽

Apical Cell ◽

Morphological Characteristics ◽

Fruit Rot ◽

Likelihood Method ◽

Correct Identification ◽

Pathogenicity Test ◽

First Report ◽

The Core ◽

Representative Isolate

Muskmelon (Cucumis melo L.) is one of the most widely cultivated and economically important fruit crops in the world. However, many pathogens can cause decay of muskmelons; among them, Fusarium spp. is the most important pathogen, affecting fruit yield and quality (Wang et al. 2011). In May 2017, fruit rot symptoms were observed on ripening muskmelons (cv. Jipin Zaoxue) in several fields in Liaocheng of Shandong Province, China. Symptoms appeared as brown, water-soaked lesions, irregularly circular in shape, with the lesion size ranging from a small spot (1 to 2 cm) to the decay of the entire fruit. The core and the surface of the infected fruit were covered with white to rose-reddish mycelium. Two infected muskmelons were collected from each of two fields, 10 km apart. Tissues from the inside of the infected fruit were surface disinfected with 75% ethanol for 30 s, and cultured on potato dextrose agar (PDA) at 25 °C in the dark for 5 days. Four purified cultures were obtained using the single spore method. On carnation leaf agar (CLA), macroconidia had a pronounced dorsiventral curvature, falcate, 3 to 5 septa, with tapered apical cell, and foot-shaped basal cell, measuring 19 to 36 × 4 to 6 μm. Chlamydospores were abundant, 5.5–7.5 μm wide, and 5.5–10.5 μm long, ellipsoidal or subglobose. No microconidia were observed. These morphological characteristics were consistent with the descriptions of F. pernambucanum (Santos et al. 2019). Because these isolates had similar morphology, one representative isolate was selected for multilocus phylogenetic analyses. DNA was extracted from the representative isolate using the CTAB method. The nucleotide sequences of the internal transcribed spacers (ITS) (White et al. 1990), translation elongation factor 1-α gene (TEF1), RNA polymerase II second largest subunit gene (RPB2), calmodulin (CAM) (Xia et al. 2019) were amplified using specific primers, sequenced, and deposited in GenBank (MN822926, MN856619, MN856620, and MN865126). Based on the combined dataset of ITS, TEF1, RPB2, CAM, alignments were made using MAFFT v. 7, and phylogenetic analyses were processed in MEGA v. 7.0 using the maximum likelihood method. The studied isolate (XP1) clustered together with F. pernambucanum reference strain URM 7559 (99% bootstrap). To perform pathogenicity test, 10 μl of spore suspensions (1 × 106 conidia/ml) were injected into each muskmelon fruit using a syringe, and the control fruit was inoculated with 10 μl of sterile distilled water. There were ten replicated fruits for each treatment. The test was repeated three times. After 7 days at 25 °C, the interior of the inoculated muskmelons begun to rot, and the rot lesion was expanded from the core towards the surface of the fruit, then white mycelium produced on the surface. The same fungus was re-isolated from the infected tissues and confirmed to fulfill the Koch’s postulates. No symptoms were observed on the control muskmelons. To our knowledge, this is the first report of F. pernambucanum causing of fruit rot of muskmelon in China. Considering the economic value of the muskmelon crop, correct identification can help farmers select appropriate field management measures for control of this disease.

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First Report of Damping-Off Caused by Rhizoctonia solani AG-4 on Lagunaria patersonii in Italy

Plant Disease ◽

10.1094/pdis-92-5-0836a ◽

2008 ◽

Vol 92 (5) ◽

pp. 836-836 ◽

Cited By ~ 3

Author(s):

D. Aiello ◽

G. Parlavecchio ◽

A. Vitale ◽

E. Lahoz ◽

R. Nicoletti ◽

...

Keyword(s):

Rhizoctonia Solani ◽

Morphological Characteristics ◽

Ruthenium Red ◽

Fluorescent Light ◽

Damping Off ◽

First Report ◽

Pectic Enzymes ◽

Electrophoretic Patterns ◽

Blue Solution ◽

Hyphal Diameter

Lagunaria patersonii (Adr.) G. Don (cow itch tree) is native to Australia and tolerates salted winds. During July 2007, damping-off of cow itch tree was observed on 4-month-old seedlings growing in a commercial nursery in eastern Sicily, Italy. More than 20% of the seedlings showed disease symptoms. First symptoms consisting of water-soaked lesions at the seedling base that expand rapidly girdle the stem and collapse the seedling in a few days. Diseased tissues were disinfested for 1 min in 1% NaOCl, rinsed in sterile water, plated on potato dextrose agar (PDA) amended with streptomycin sulphate at 100 mg/l, and then incubated at 25°C. A fungus with mycelial and morphological characteristics of Rhizoctonia solani Kühn was consistently yielded. Fungal colonies were initially white, turned brown with age, and produced irregularly shaped, brown sclerotia. Microscopic examination revealed that hyphae had a right-angle branching pattern, were constricted at the base of the branch near the union with main hyphae, and septate near the constriction. Basidia were not observed in the greenhouses or on the plates. Hyphal cells were determined to be multinucleate when stained with 0.5% aniline blue solution and examined at ×400 magnification with a microscope. Anastomosis groups were determined by pairing isolates on 2% water agar in petri plates (3). Pairings were made with tester strains of AG-1 IA, AG-2-2-1, AG-2-2IIIB, AG-2-2IV, AG-3, AG-4, AG-5, AG-6, AG-11. Anastomosis was observed only with tester isolates of AG-4 producing both C2 and C3 reactions. The hyphal diameter at the point of anastomosis was reduced, the anastomosis point was obvious, and cell death of adjacent cells was observed. These results were consistent with other reports on anastomosis reactions (1). The identification of group AG-4 within R. solani has been confirmed by electrophoretic patterns of pectic enzymes (polygalacturonases) in vertical pectin-acrylamide gel stained with ruthenium red (2). Pathogenicity tests were conducted on potted, healthy, 3-month-old seedlings of cow itch tree. Twenty plants were inoculated by placing plugs of PDA from 5-day-old mycelial cultures near the base of the stem. The same number of plants was treated with 1 cm2 PDA plugs as control. Plants were kept at 25°C and 95% relative humidity on a 12-h fluorescent light/dark regimen. Wilt symptoms due to basal stem rot, identical to ones observed in the nursery, appeared 10 days after inoculation and all inoculated plants showed symptoms within 1 month. Control plants remained healthy. The pathogen was reisolated from symptomatic tissues, completing Koch's postulates. To our knowledge, this is the first report in the world of R. solani causing disease on L. patersonii. References: (1) D. E. Carling. Page 37 in: Grouping in Rhizoctonia solani by Hyphal Anastomosis Reactions. Kluwer Academic Publishers, the Netherlands, 1996. (2) R. H. Cruickshank and G. C. Wade. Anal. Biochem. 107:177, 1980. (3) C. C. Tu and J. W. Kimbrough. Mycologia 65:941, 1973.

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