First Report of Leaf Blight on Calathea picturata Caused by Exserohilum rostratum in Taiwan

Many Calathea species in the family Marantaceae are beautiful ornamental plants with variegated foliage. Among them, C. picturata ‘Argentea’, an evergreen perennial that has pale green leaves with dark green margins and a red underside, is a popular houseplant in Taiwan. In 2004, a new foliage disease that caused leaf blight of C. picturata ‘Argentea’ was first observed in a nursery in southern Taiwan. Initial symptoms were tiny, brown spots that appeared on the leaves of all ages, which quickly enlarged and coalesced. These necrotic lesions spread to cover the entire leaves in high temperature and moisture conditions and caused leaves to shrivel and eventually die. A dematiaceous hyphomycete with multicelled conidia was consistently isolated from the diseased leaves after being surfaced sterilized with 10% Clorox and placed on vegetable juice agar (10% V8 juice, 0.02% CaCO3, and 2% agar [VJA]). Pathogenicity of the isolate was tested by spraying ‘Argentea’ calathea leaves with a conidia suspension (1.6 × 105 conidia/ml) prepared from a culture grown on VJA at 28°C for 7 days. Plant leaves sprayed with distilled water were used as a control. Three pots of 15-cm high ‘Argentea’ calathea plants were inoculated with 10 ml of a conidia suspension and the experiment was conducted twice at 28°C and 90% relative humidity in a growth chamber. Tiny, brown spots started to show on all inoculated leaves 5 days after inoculation and the progression of symptom development was similar to that observed in nature. Control leaves remained asymptomatic. The same dematiaceous hyphomycete fungus was reisolated from 13 of 16 disease tissues taken from four symptomatic leaves. A colony of the calathea isolate was olive green when grown on potato dextrose agar (PDA) and conidia production was observed 7 days after incubation in darkness. The conidiophores were either branches from or the ends of normal mycelium, some of them geniculate with conidium produced at each bend measuring 142 to 602 (340) × 3 to 6 (4) μm on disease tissues and 51 to 150 (103) × 3 to 5 (4) μm on PDA. Conidia were multicelled with protruding hilum at the base, terminal cells thickened, olivaceous brown or golden brown in fusiform shape with blunt tips, 5 to 11 septate on disease tissues and 6 to 11 septate on PDA, measuring 46 to 166 (95) × 8 to 19 (13) μm on disease tissues and 58 to 145 (94) × 6 to 15 (11) μm on PDA, germinating by producing germ tubes semiaxially from each end. Morphological characteristics of the calathea isolate fit the description of the genus Exserohilum (2). Comparison of rDNA internal transcribed spacer (ITS) sequence of the calathea isolate with those in GenBank revealed that it shared 99.5% (549 of 552) similarity with a published sequence (GenBank Accession No. EU571210) (3) and Exserohilum rostratum was its closest species. ITS sequence analysis was done as previously described (1). Morphological and molecular data identified the pathogen as E. rostratum (Drechs.) Leonard & Suggs (= Bipolaris rostrata (Drechs.) Shoemaker). To our knowledge, this is the first report of leaf blight caused by E. rostratum on C. picturata in Taiwan. References: (1) L. L. Chern et al. Plant Dis. 94:1164, 2010. (2) K. J. Leonard. Mycologia 68:402, 1976. (3) R. Sappapan et al. J. Nat. Prod. 71:1657, 2008.

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First Report of Nigrospora Leaf Blight on Sesame Caused by Nigrospora sphaerica in China

Plant Disease ◽

10.1094/pdis-07-13-0684-pdn ◽

2014 ◽

Vol 98 (6) ◽

pp. 842-842 ◽

Cited By ~ 3

Author(s):

H. Zhao ◽

H. Y. Liu ◽

X. S. Yang ◽

Y. X. Liu ◽

Y. X. Ni ◽

...

Keyword(s):

Morphological Characteristics ◽

Leaf Blight ◽

Morphological Data ◽

Its2 Region ◽

Oilseed Crop ◽

Conidial Suspension ◽

First Report ◽

Initial Symptoms ◽

Central Regions ◽

Leaf Pathogen

Sesame (Sesamum indicum L.) is an important oilseed crop widely grown in the central regions of China. A new leaf blight has increasingly been observed in sesame fields in Anhui, Hubei, and Henan provinces since 2010. Approximately 30 to 40% of the plants were symptomatic in the affected fields. Initial symptoms were yellow to brown, irregularly shaped lesions. Lesions later expanded and the affected leaves tuned grayish to dark brown and wilted, with a layer of whitish mycelial growth on the underside. Severe blighting caused the center of lesions to fall out, leaving holes in the leaves. Sections of symptomatic leaf tissues were surface-sterilized in 75% ethanol for 30 s, then in 1% HgCl2 for 30 s, rinsed three times in sterile distilled water, and plated onto potato dextrose agar (PDA). The resulting fungal colonies were initially white, and then became grayish-brown with sporulation. Conidia were single-celled, black, smooth, spherical, 14.2 to 19.8 μm (average 17.1 μm) in diameter, and borne on a hyaline vesicle at the tip of each conidiophore. Morphological characteristics of the isolates were similar to those of Nigrospora sphaerica (1). To verify the identification based on morphological features, the ITS1-5.8S-ITS2 region of the ribosomal RNA was amplified using ITS1 (5′-TCCGTAGGTGAACCTGCGG-3′) and ITS4 (5′-TCCTCCGCTTATTGATATGC-3′) primers (3), and then sequenced and compared to the GenBank database through a BLAST search. Comparison of the sequence revealed 100% similarity to N. sphaerica (GenBank Accession No. JF817271.1). On the basis of morphological data and the ITS rDNA sequence, the isolate was determined to be N. sphaerica. Pathogenicity tests were conducted using fresh and healthy sesame leaves of 10 plants. A conidial suspension (106 conidia/ml) collected from a 7-day-old culture on PDA was used for inoculation. Leaves of 10 plants were spray-inoculated with the spore suspension at the 6-week-old growth stage, and an additional 10 plants were sprayed with sterile water. Inoculated plants were covered with polyethylene bags to maintain high humidity. Plants were kept at 28°C and observed for symptom every day. Ten to 15 days after inoculation, inoculated leaves developed blight symptoms similar to those observed on naturally infected leaves. No symptoms were observed on the control leaves. N. sphaerica was re-isolated from the inoculated leaves, thus fulfilling Koch's postulates. N. sphaerica has been reported as a leaf pathogen on several hosts worldwide (2). To our knowledge, this is the first report of Nigrospora leaf blight on sesame caused by N. sphaerica in China. References: (1) M. B. Ellis. Dematiaceous Hyphomycetes. CMI, Kew, Surrey, UK, 1971. (2) D. F. Farr and A. Y. Rossman. Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ . July 01, 2013. (3) M. A. Innis et al. PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA, 1990.

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First Report of Leaf Blight in Chinese Hickory (Carya cathayensis) Caused by Alternaria petroselini in China

Plant Disease ◽

10.1094/pdis-02-13-0176-pdn ◽

2013 ◽

Vol 97 (9) ◽

pp. 1253-1253 ◽

Cited By ~ 1

Author(s):

Y. H. Liu ◽

C. Q. Zhang ◽

B. C. Xu

Keyword(s):

Management Practices ◽

Morphological Characteristics ◽

Morphological Characterization ◽

Leaf Blight ◽

Internal Transcribed Spacers ◽

Infected Leaf ◽

First Report ◽

Plastic Bags ◽

Initial Symptoms ◽

Carya Cathayensis

Chinese hickory (Carya cathayensis) is one of the important economic forest crops in Zhejiang and Anhui Provinces, China. In 2012, nearly 40% of hickory orchards and 6.8% of hickory trees were affected by leaf blight in Zhejiang. Initial symptoms consisted of small, brown, water-soaked lesions, which subsequently enlarged and developed a black sporulating necrotic center surrounded by a chlorotic halo. Infected leaf samples collected from 25 different orchards in Lin'an and 13 different orchards in Chun'an were surface sterilized with 1.5% sodium hypochlorite for 1.5 min, rinsed in water, plated on 2% potato dextrose agar (PDA), and incubated at 25°C in the dark for 1 week. Single conidium cultures were consistently isolated and cultured on PDA and V8 agar for morphological characterization (1,3). On both agar media, colonies were dark olive brown with smooth margins and concentric rings of sporulation. Conidia were solitary, darkly pigmented, predominantly ovoid-subsphaeroid, and 23 to 52 × 13 to 23 μm with up to six or seven transepta and one to three longisepta. The ribosomal internal transcribed spacers ITS1 and ITS2 of 10 isolates were amplified using primers ITS1/ITS4 on DNA extracted from mycelium and nucleotide sequences showed 100% similarity to that of A. petroselini (GenBank Accession Nos. AY154685.1 and EU807868.1). To confirm pathogenicity, 10 uninfected leaves from each of 10 C. cathayensis trees were sprayed either with a conidia suspension (105 conidia per ml) or with distilled water only to serve as an un-inoculated control. Leaves were subsequently wrapped in plastic bags to retain moisture, and incubated for 48 h. After 1 week, 8 of 10 isolates caused lesions identical to those initially described whereas no symptoms developed on water inoculated leaves. Cultures reisolated from lesions and cultured on PDA exhibited morphological characteristics identical to A. petroselini (1,2,3), confirming Koch's postulates. To our knowledge, this is the first report of leaf blight in C. cathayensis, and this identification would allow producers to identify for appropriate management practices. References: (1) P. M. Kirk et al. The Dictionary of the Fungi, 10th edition, page 159. CABI Bioscience, UK, 2008. (2) B. M. Pryor et al. Mycologia 94:49, 2002. (3) E. G. Simmons. Alternaria: An Identification Manual. CBS Fungal Biodiversity Centre, Utrecht, The Netherlands, 2007.

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First Report of Penicillium digitatum causing Postharvest rot of Citron Fruit in Kunming, China

Plant Disease ◽

10.1094/pdis-10-21-2386-pdn ◽

2021 ◽

Author(s):

Huan Ren ◽

Gao Yang ◽

Xue Li ◽

Shijun Xing ◽

Yating Gao ◽

...

Keyword(s):

Morphological Characteristics ◽

Penicillium Digitatum ◽

Green Water ◽

Universal Primers ◽

Single Strain ◽

First Report ◽

Rdna Its ◽

Its Sequence Analysis ◽

Initial Symptoms ◽

Citrus Medica

Citron (Citrus medica L.) is a perennial evergreen woody tree of Rutaceae family and Genus of Citrus. The citron is cultivated for its economic, medicinal and ornamental values in the south of China. (Yang et al., 2015). The shapes range from spherical to ovate and the sizes range from 3 to 5 kg (Klein et al., 2016). In June 2021, some postharvest citron fruits (Citrus medica var. medica) were found to have decay with a green or greyish mycelium on part or whole citron in 2 farmer’s markets in Kunming city, Yunnan Province (N 25°02′; E 102°42′), southwest China. Initial symptoms appeared as white, brown, and irregular necrotic spots in the pericarp. The lesions enlarged gradually and developed into green, water-soaked areas which extend rapidly. Eventually, the diseased fruits were rotten, soften, and the green spore masses confined to the surface (Fig. 1A). The incidence of this disease in postharvest citron fruits ranges from 15 % to 35 %, which is extremely destructive to the fruit of Rutaceae family plants (Chen et al., 2019). Small pieces (5 mm2) of symptomatic citron fruits were surface disinfected in 75 % ethanol and 0.3 % NaClO for 30 s and 2 min respectively, rinsed with distilled water for three times, blotted dry, placed onto potato dextrose agar (PDA) medium aseptically and incubated in a growth chamber at 25 ± 1 ℃, after 7 days, different colonies grew on PDA plates that were isolated and purified on new PDA medium at 25 ± 1 ℃ for 7 days. Inoculating repeatedly until six single-strain (XY01 to XY06) were obtained, and these isolates were stored in 15 % glycerol at –80 ℃ in a refrigerator in the State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan Agricultural University. The selected pathogens (XY01 to XY06) were inoculated on PDA medium, incubated at 25 ± 1 ℃. After 7 days, colonies of the isolate obverse are olive green, the white margin and greyish-green spores on the surface, and the reverse colorless to cream yellow or pale dull brown. Colonies texture was velutinous, with a special fragrance. The conidia structure was very fragile and break up easily into many cellular elements. Conidiophores were terverticillate, produced by subsurface or aerial hyphae, irregularly branched and composed of short stipes with few metulae and branches that terminate in whorls of three to six phialides, which are often solitary, cylindrical with a short neck. Conidia are hyaline to pale green, smooth-walled, without septate, partially ellipsoidal, or obovate (4.9 to11.9× 4.3 to 8.9 μm). Partial cylindrical (8.2 to 10.5× 2.7 to 5.3 μm), there are some small conidia, which were ellipsoidal or spherical (3.9 to 5.2× 2.7 to 5.2 μm). According to morphological characteristics, the fungus was identified as Penicillium digitatum (Pers.) Sacc. Isolate XY01 and XY02 were used for molecular identification and genomic DNA was extracted using the CTAB method (Aboul-Maaty & Oraby, 2019). The universal primers ITS1 and ITS4 were used to amplify and sequence the ITS1, 5.8S, and ITS2 rDNA region. Using NCBI’s BLASTn tools, the nucleotide sequences of XY01 and XY02 (Gen-Bank accessions MZ976843 and OK513274) show 100 % identity to MK450692 (P. digitatum strain CMV010G4). Pathogenicity tests have used the fruits (Citrus medica), which maturity was more than 80%. The pathogens (XY01, XY02) were cultured for 7 days on PDA medium, washed with sterilized water the resulting spore suspensions diluted to 1.0 × 106 spores/ml. Wounds (0.5 × 0.5 cm) were made on the surface of citron fruits by scraping with a sterile scalpel and then treated with 200 µl of spore suspension (Wild, 1994). Control citron fruits were treated with sterile water. citron fruits were incubated at 24-26 °C. Each treatment was performed in triplicate with 6 citron fruits. After 3 days, all fruits had developed lesions, in a water-stained, pale brown, and rapidly formed white hyphae, white mold layer was observed with a length of 1.5-2.5 cm and a width of 1-2 cm (Fig.1C), but control did induce infection. After 7 days, decay developed more quickly, the hyphae rapidly expanded on the surface of the pericarp, with vague and irregular edges, then a green mold layer was formed, the whole fruit was observed to rot and soften, When the citron was cut, the white flesh inside turned black and rotted (Fig.1B). P. digitatum was consistently reisolated from the inoculated plants but not from the controls. No symptoms developed on the control (Fig.1D). According to Koch’s postulates, the inoculated strains of XY01 and XY02 were the isolates causing citron decay disease. Based on symptoms, morphological characteristics, rDNA-ITS sequence analysis, and pathogenicity, this fungus was identified as P. digitatum. To our knowledge, this is the first report of the distribution of P. digitatum on Citron (Citrus medica) in China.

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First Report of Cylindrocarpon destructans var. destructans Causing Black Root Rot of Sanqi (Panax notoginseng) in China

Plant Disease ◽

10.1094/pdis-11-12-1104-pdn ◽

2014 ◽

Vol 98 (1) ◽

pp. 162-162 ◽

Cited By ~ 12

Author(s):

Z. S. Mao ◽

Y. J. Long ◽

Y. Y. Zhu ◽

S. S. Zhu ◽

X. H. He ◽

...

Keyword(s):

Root Rot ◽

Morphological Characteristics ◽

Panax Notoginseng ◽

Its Sequence ◽

Single Spore ◽

Black Root Rot ◽

First Report ◽

Cylindrocarpon Destructans ◽

Its Sequence Analysis ◽

Four Levels

Sanqi (Panax notoginseng (Burk.) F. H. Chen) is planted on >10,000 ha in China and is a popular Chinese medicinal material (2). Black root rot is a recently identified but worsening problem on Sanqi since 2010 in Wenshan, China. Of the plant tubers examined from 185 ha, 8.5 to 27.4% were black with necrotic lesions. The base of leaves of infected plants had brown, sunken, necrotic lesions, and symptomatic plants had one to three chlorotic leaves. A fungus was isolated consistently from the basal leaves, bulb, and tubers of symptomatic plants. Six single-spore isolates were cultured on potato sucrose agar (PSA) at 25 ± 1°C in the dark. The mycelium of each culture was white initially on PSA, and then became rust-colored. The adaxial surfaces of the plates were black. Conidiophores were 13.6 to 167.3 × 1.4 to 21.8 μm (avg. 68.6 × 2.9 μm), single or with up to four levels of branching and two to three branches (or phialides) per level. The basal branches were often divergent, whereas the terminal branches were usually more appressed. Sporodochia were not present. Microconidia were 0-septate, 4.1 to 9.5 × 2.7 to 4.1 μm (avg. 8.2 × 2.9 μm). Conidia were 1- to 3-septate and occasionally 4-septate. One- to 3-septate conidia were clavate, with a truncate or slightly protruding conidial base, 9.2 to 40.8 × 3.5 to 6.8 μm (avg. 26.7 × 5.2 μm); whereas 4-septate conidia were 32.6 to 50.3 × 5.4 to 6.8 μm (avg. 40.9 × 6.5 μm). Chlamydospores were abundant, golden to brown, single or in chains or clumps, and up to 21.8 μm in diameter. PCR amplification was carried out for one isolate, RR926, using rDNA internal transcribed spacer (ITS) primer pairs ITS1F and ITS4 (4). Sequencing of the PCR product (GenBank Accession No. KC904953) revealed 99% similarity (99% coverage) with the ITS sequence of Cylindrocarpon destructans var. destructans (AM419065). Phylogenetic analysis (MEGA 4.1) using the neighbor-joining algorithm placed the isolate in a well-supported cluster (>90% bootstrap value based on 1,000 replicates) with AM419065. Therefore, the pathogen was identified as C. destructans (Zinssm.) Scholten var. destructans (teleomorph Ilyonectria radicicola (Gerlach & L. Nilsson) P. Chaverri & C. Salgado) based on morphological characteristics and rDNA-ITS sequence analysis (1,3). Pathogenicity tests of the six isolates were conducted on five 1-year-old and five 3-year-old plants/isolate. The roots of all plants were washed with sterilized water, and then surface-sterilized with 75% ethanol. Inoculum (1 ml of 106 conidia/ml) of each isolate was brushed onto the roots of each plant with a paintbrush. Inoculated plants were planted in pots in a mixture of sterilized quartz sand:vermiculite:pearlite (2:1:1, v/v). The pots were placed under black shadecloth. The roots of five 1-year-old and five 3-year-old plants were brushed similarly with sterilized water as control treatments. After 30 days, symptoms similar to those on the original diseased plants were observed on the roots of all plants inoculated with the six isolates. The roots of non-inoculated plants remained healthy. The experiment was repeated. The same pathogen was re-isolated from the inoculated plants, but no pathogen was isolated from roots of the control plants. C. destructans var. destructans is widely distributed in soils (1), but to our knowledge, this is the first report of this fungus causing black root rot of Sanqi in China. References: (1) P. Charerri et al. Stud. Mycol. 68:57, 2011. (2) C. Y. Hu. New Rural Technol. 2:59, 2013 (in Chinese). (3) K. A. Seifert and P. E. Axelrood. Can. J. Plant Pathol. 20:115, 1998. (4) K. A. Seifert et al. Phytopathology 93:1533, 2003.

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First Report of Garlic Leaf Blight Caused by Botrytis porri in China

Plant Disease ◽

10.1094/pdis-93-11-1216b ◽

2009 ◽

Vol 93 (11) ◽

pp. 1216-1216 ◽

Cited By ~ 2

Author(s):

J. Zhang ◽

G. Q. Li ◽

D. H. Jiang

Keyword(s):

Average Length ◽

Morphological Characteristics ◽

Its Region ◽

Gray Mold ◽

Leaf Blight ◽

Lesion Length ◽

Width Ratio ◽

Its Sequence ◽

First Report ◽

5.8S Rdna

In the spring of each year from 2007 to 2009, a leaf blight of garlic (Allium sativum L.) was observed in more than 50 fields in Zhushan County of Hubei Province, China. Gray mold was observed on many of the blighted garlic leaves. The percentage of garlic plants with blight and gray mold symptoms ranged from 10 to 50% with one to three blighted leaves on each plant, which severely reduced the yield of young garlic plants (produced as a green vegetable). Ten strains of a Botrytis sp. were isolated from symptomatic garlic leaves collected from 10 different fields. These strains were inoculated onto potato dextrose agar (PDA) in petri dishes and incubated at 20°C for 3 to 15 days for observation of colony characteristics and morphology of sclerotia and conidia. All 10 Botrytis strains formed flat and “ropy” mycelia (mycelial strands) on PDA. Abundant sporulation with a gray powdery appearance was observed on the colonies after 6 days. Conidiophores were erect with alternate branches at the top and ranged from 907 to 1,256 μm high. Conidia were borne in botryose clusters on conidiophores, obovate, and 10.4 to 17.6 × 7.6 to 13.1 μm with an average length/width ratio of 1.36. Discrete sclerotia were produced on each colony after 15 days. Mature sclerotia were black, cerebriform and convoluted, and 1.9 to 9.1 × 1.6 to 6.5 mm. Morphological characteristics of the colonies, conidia, and sclerotia of these Botrytis strains were similar to Botrytis porri Buchwald (1,2). Strain GarlicBC-16 was selected as a representative for molecular identification. Genomic DNA was extracted from mycelia of this strain and used as a template for amplification of the internal transcribed spacer (ITS) region of rDNA using primer pair ITS1/ITS4. A 539-bp amplicon was obtained and sequenced (GenBank Accession No. EU519206). Excluding the flanking regions, the amplicon contained a 453-bp ITS sequence (ITS1 + 5.8S rDNA + ITS2) 100% identical to the ITS sequence of strain MUCL3234 of B. porri (GenBank Accession No. AJ716292). Pathogenicity of strain GarlicBC-16 was tested by inoculation of 10 young and fully expanded garlic leaves taken from 100-day-old garlic plants with mycelial agar plugs (three plugs per leaf and spaced by 5 cm). Ten garlic leaves inoculated with agar plugs of PDA alone served as controls. Inoculated garlic leaves were covered with a plastic film (0.1 mm thick; Gold Mine Plastic Industrial Ltd. Jiangmen, China) and incubated at 20°C with 12-h light/12-h dark. Control leaves remained healthy after 48 to 120 h, but gray, water-soaked lesions appeared on leaves inoculated with strain GarlicBC-16 after 48 h. The average lesion length reached 27.3 mm after 90 h and abundant sporulation was produced on necrotic leaf lesions after 120 h. Microscopic examination showed the shape and size of conidia that formed on garlic leaf lesions were similar to those formed by strain GarlicBC-16 on PDA. On the basis of the isolation, identification, and pathogenicity tests, B. porri was determined to be the causal agent of garlic leaf blight in Zhushan County. B. porri has been reported to cause neck rot of leek (A. porrum) (1) and clove rot of garlic (2), and has been isolated from asymptomatic foliage and seeds of A. cepa (3). To our knowledge, this is the first report of garlic leaf blight caused by B. porri in China. References: (1) S. K. Asiedu et al. Plant Dis. 70:259, 1986. (2) F. M. Dugan et al. J. Phytopathol. 155:437. 2007. (3) L. J. du Toit et al. Plant Dis. 86:1178, 2002.

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First Report of Phytophthora sansomeana Causing Wilting and Stunting on Corn in Ohio

Plant Disease ◽

10.1094/pdis-94-1-0125c ◽

2010 ◽

Vol 94 (1) ◽

pp. 125-125 ◽

Cited By ~ 7

Author(s):

L. X. Zelaya-Molina ◽

M. L. Ellis ◽

S. A. Berry ◽

A. E. Dorrance

Keyword(s):

United States ◽

Growth Rate ◽

Morphological Characteristics ◽

Petri Dish ◽

The United States ◽

The State ◽

Its Sequence ◽

First Report ◽

Its Sequence Analysis ◽

Pathogenicity Tests

During the spring of 2004, corn seedlings with symptoms of wilting and stunting were observed in corn fields with emergence problems in Madison and Brown counties, Ohio. Phytophthora isolates were recovered from sections of root tissue of diseased seedlings placed on dilute V8 media amended with pentachloronitrobenzene, iprodione, benlate, neomycin sulfate, and chloramphenicol. Colonies were rosaceous on potato dextrose agar, with a growth rate of 5 mm per day. Homothallic isolates with paragynous antheridia were observed on lima bean agar (LBA); oogonia were 35 to 50 μm in diameter. Sporangia were ovoid to obpyriform, nonpapillate, with an average size of 49 × 30 μm. Pathogenicity was tested on corn seeds using a petri dish assay with 3-day-old cultures on LBA and a sand-cornmeal cup test amended with inoculum from 7-day-old cultures on LBA (1). After 1 week in the petri dish assay, the seeds failed to germinate completely and were covered with white, fungal-like, aerial mycelia and the pathogen was recovered from brown discolored radicle roots. In the cup assay, 2-week-old seedlings developed the same symptoms observed in the field; the pathogen was also isolated from brown discolored roots. In both assays, no symptoms developed in the noninoculated controls. Both pathogenicity tests were repeated two times. Genomic DNA was extracted from mycelia of two isolates and the internal transcribed spacer (ITS) region was amplified and sequenced using ITS6/ITS4 primers (2). Both isolates had identical ITS sequences (GenBank Accession No. GQ853880). A BLAST search of the NCBI database showed 100% homology with the sequence of the haplotype isolate of Phytophthora sansomeana (Accession No. EU925375). P. sansomeana is a new species characterized principally by a large oogonial diameter (37 to 45 μm), rapid growth rate (7 to 10 mm/day), and an ITS sequence falling in Cooke's clade 8 (4). Pathogenicity tests, morphological characteristics, and the ITS sequence analysis indicate that P. samsomena is the causal agent of the symptoms observed on corn seedlings. P. sansomeana has been reported as a pathogen of soybean in Indiana, Douglas-fir in Oregon, and weeds in alfalfa fields in New York (4). To our knowledge, this is the first report of P. sansomeana infecting corn in Ohio, albeit other isolates have previously been recovered from soybean in the state. There are four previous reports of Phytophthora spp. affecting corn in the United States and Mexico (3). Crop rotation will have little effect in management of this pathogen since corn and soybean are produced in the same fields continuously throughout the state. References: (1) K. E. Broders et al. Plant. Dis. 91:727, 2007. (2) D. E. L. Cooke et al. Fungal Genet. Biol. 30:17, 2000. (3) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN. 1989. (4) E. M. Hansen et al. Mycologia 101:129, 2009.

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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 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 Sclerotinia sclerotiorum on Campanula carpatica and Schizanthus × wisetonensis in Italy

Plant Disease ◽

10.1094/pdis.2002.86.1.71a ◽

2002 ◽

Vol 86 (1) ◽

pp. 71-71

Author(s):

A. Garibaldi ◽

A. Minuto ◽

M. L. Gullino

Keyword(s):

United States ◽

Sclerotinia Sclerotiorum ◽

Ornamental Plants ◽

Soil Surface ◽

The United States ◽

First Report ◽

Potted Plants ◽

Initial Symptoms ◽

Stem Necrosis ◽

Campanula Carpatica

The production of potted ornamental plants is very important in the Albenga Region of northern Italy, where plants are grown for export to central and northern Europe. During fall 2000 and spring 2001, sudden wilt of tussock bellflower (Campanula carpatica Jacq.) and butterfly flower (Schizanthus × wisetonensis Hort.) was observed on potted plants in a commercial greenhouse. Initial symptoms included stem necrosis at the soil line and yellowing and tan discoloration of the lower leaves. As stem necrosis progressed, infected plants growing in a peat, bark compost, and clay mixture (70-20-10) wilted and died. Necrotic tissues were covered with whitish mycelia that produced dark, spherical (2 to 6 mm diameter) sclerotia. Sclerotinia sclerotiorum was consistently recovered from symptomatic stem pieces of both plants disinfested for 1 min in 1% NaOCl and plated on potato dextrose agar amended with streptomycin sulphate at 100 ppm. Pathogenicity of three isolates obtained from each crop was confirmed by inoculating 45- to 60-day-old C. carpatica and Schizanthus × wisetonensis plants grown in containers (14 cm diameter). Inoculum that consisted of wheat kernels infested with mycelia and sclerotia of each isolate was placed on the soil surface around the base of previously artificially wounded or nonwounded plants. Noninoculated plants served as controls. All plants were maintained outdoors where temperatures ranged between 8 and 15°C. Inoculated plants developed symptoms of leaf yellowing, followed by wilt, within 7 to 10 days, while control plants remained symptomless. White mycelia and sclerotia developed on infected tissues and S. sclerotiorum was reisolated from inoculated plants. To our knowledge, this is the first report of stem blight of C. carpatica and Schizanthus × wisetonensis caused by S. sclerotiorum in Italy. The disease was previously observed on C. carpatica in Great Britain (2) and on Schizanthus sp. in the United States (1). References: (1) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN, 1989. (2) J. Rees. Welsh J. Agric. 1:188, 1925.

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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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