First Report of Seedling Stem Rot on Jinxianlian (Anoectochilus roxburghii) Caused by Fusarium oxysporum in China

Anoectochilus roxburghii is an important Chinese herbal medicine plant belonging to Orchidaceae and known as Jinxianlian. This orchid is cultivated and mostly adopted to treat diabetes and hepatitis. About 2 billion artificially cultivated seedlings of Jinxianlian are required each year and approximately $600 million in fresh A. roxburghii seedlings is produced in China. From 2011, sporadic occurrence of stem rot on Jinxianlian have been observed in greenhouses in Jinhua City (N29°05′, E119°38′), Zhejiang Province. In 2018, nearly 30% of seedlings of Jinxianlian grown in greenhouse conditions were affected by stem rot in Jinhua City. Symptoms initially occurred in the stem at the soil line causing dark discoloration lesions, rotted tissues, wilting, and eventually leading to the death of the plants. A total of 23 diseased seedlings collected from seven different greenhouses were surface sterilized with 1.5% sodium hypochlorite for 3 min, then rinsed in water. Pieces of tissues disinfected from each sample were plated on 2% potato dextrose agar (PDA), and incubated at 25°C in the dark for 5 days (Kirk et al. 2008). A total of 19 isolates were recovered. They developed colonies with purple mycelia and beige or orange colors after 7 days of incubation under 25°C on PDA and carnation leaf agar (CLA) media (Kirk et al. 2008; Zhang et al. 2016). Colonies on PDA had an average radial growth rate of 3.1 to 4.0 mm /d at 25°C. Colony surface was pale vinaceous, floccose with abundant aerial mycelium. On CLA, aerial mycelium was sparse with abundant bright orange sporodochia forming on the carnation leaves. Microconidia were hyaline and oval-ellipsoid to cylindrical (3.7 to 9.3 × 1.3 to 2.9 μm) (n=19). Macroconidia were 3 to 5 septate and fusoid-subulate with a pedicellate base (27.4 to 35.6 × 3.2 to 4.2 μm) (n=19). These morphological features were consistent with Fusarium oxysporum (Sun et al. 2008; Lombard et al., 2019). To confirm the identification based on these morphological features, the internal transcribed spacer region (ITS) and translation elongation factor1 (TEF) were amplified from the DNA of 3 out of 19 isolates chosen at random respectively using the set primer ITS1/ITS4 and EF1/ EF2 (Sun, S., et al. 2018; Lombard et al., 2019). BLAST analysis revealed that the ITS sequences (OK147619, OK147620, OK147621) had 99% identity to that of F. oxysporum isolate JJF2 (GenBank MN626452) and TEF sequence (OK155999, OK156000, OK156001) had 100% identity to that of F. oxysporum isolate gss100 (GenBank MH341210). A multilocus phylogenetic analysis by Bayesian inference (BI) and maximum likelihood (ML) trees based on ITS and TEF indicated that the pathogen grouped consistently with F. oxysporum. Three out of 19 isolates chosen at random were selected to evaluate pathogenicity. Uninfected healthy A. roxburghii seedlings about 40 day-old planted in sterilized substrates were sprayed with distilled water containing 2 x 106 conidia per ml suspensions as inoculums, and plants sprayed with distilled water alone served as controls. Plants were then incubated at 25°C and 85% relative humidity. Ten plants were inoculated for each isolate. After 10 days, all plants inoculated developed stem rot symptoms, while control plants remained healthy. Cultures of Fusarium spp. were re-isolated only from inoculated plants with the frequency of 100% and re-identified by morphological characteristics as F. oxysporum, fulfilling Koch’s postulates. To the best of our knowledge, this is the first report of F. oxysporum causing stem rot on A. roxburghii seedlings. As F. oxysporum is a devastating pathogenic fungus with a broad host range, measures should be taken in advance to manage stem rot of A. roxburghii.

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First Report of Colletotrichum capsici Causing Anthracnose on Alocasia macrorrhizos in China

Plant Disease ◽

10.1094/pdis-06-20-1228-pdn ◽

2020 ◽

Author(s):

HaiYan Ben ◽

JianFei Huo ◽

YuRong Yao ◽

Wei Gao ◽

WanLi Wang ◽

...

Keyword(s):

Disease Incidence ◽

Morphological Characteristics ◽

Asia Pacific ◽

Stem Rot ◽

Perennial Herb ◽

Broad Host Range ◽

Distilled Water ◽

First Report ◽

Colletotrichum Capsici ◽

Initial Symptoms

Alocasia macrorrhizos (Linnaeus) G. Don is a perennial herb in the Araceae family. It is native to South Asia and the Asia-Pacific and has long been cultivated as it is an economically important medicinal and ornamental plant. During July 2012 and 2013, severe outbreaks of leaf spot and stem rot disease on this plant occurred in a greenhouse of Shunyi district, in Beijing, China (117°05’E, 40°13’N). The disease incidence was greater than 30%. The leaf spots first appeared as yellow dots. As lesions expanded, the symptoms were circular to subcircular, light brown lesions with darker brown edges, Around the lesions the leaf tissue was chlorotic causing the formation of a yellow halo (Suppl. Fig1). Initial symptoms on the stems were brown, round or fusiform spots . As the disease progressed, lesions enlarged and merged together. When humidity was high, black acervuli with grey brown cirrhus of conidia were rapidly produced in lesions. Infected plants eventually withered or collapsed from the stem rot (Suppl. Fig2). Infected tissues were surface-sterilized in 1% NaOCl for 1 min, washed three times with distilled water, and placed on potato dextrose agar (PDA). Colonies on PDA, growing at 25°C in darkness, showed grayish brown and grey brown conidial masses produced from acervuli with black seta (Suppl. Fig3). Acervuli (n=30) were dark brown to black and approximately round, 121 to 210 μm in diameter, averaging 166.5 μm (Suppl. Fig4). Setae (n=30) scattered in acervuli, black, septate, 94.4 to 128.4×3.4 to 4.7 μm, base inflated, and narrower toward the top (Suppl. Fig5). Conidiophores (n=50) were phialidic, hyaline, unicellular. Conidia (n=50) were hyaline, monospora, falcate, base obtuse, apices acute, and 20.5 to 24.7 ×2.8 to 3.4 μm (Suppl. Fig6). Six monoconidial isolates were made, and the morphological characteristics of the fungus were similar to those of Colletotrichum capsici (Syd.) Butler & Bisby (Mordue, 1971). In the greenhouse (25 to 30 °C, relative humidity 98%), pathogenicity tests were conducted by spraying a 106 spores /mL suspension on leaves and stems of 10 healthy potted A. macrorrhizos plants (3-year-old). A control was included that consisted of ten plants sprayed with sterile distilled water. All treated plants were covered with a plastic bag and removed 48 h later. After 12 days, all inoculated leaves and stems appeared with typical Anthracnose symptoms, whereas control plants remained healthy. The fungus was reisolated from diseased tissues, fulfilling Koch´s postulates. The ITS region of a representative isolate was amplified and sequenced using the primers ITS1/ITS4 (White et al. 1990).The obtained ITS sequence (GenBank Accession No. KJ018793.1) showed 100% similarity to Colletotrichum capsici (Accession No. HQ271469.1 and DQ454016.1). Colletotrichum capsici is synonymous to Colletotrichum truncatum. Colletotrichum capsici is a major phytopathogen with a broad host range which causes anthracnose disease. The first report of C. capsici as a pathogen of Alocasia macrorrhizos was reported in India in 1979 (Mathur, 1979). To our knowledge, this is the first record of C. capsici causing anthracnose on A. macrorrhizos in China.

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First report of Diaporthe ueckerae causing stem canker on soybean (Glycine max L.) in Colombia

Plant Disease ◽

10.1094/pdis-04-21-0718-pdn ◽

2021 ◽

Author(s):

Nathali López-Cardona ◽

YUDY ALEJANDRA GUEVARA ◽

Lederson Gañán-Betancur ◽

Carol Viviana Amaya Gomez

Keyword(s):

Management Strategies ◽

Elongation Factor ◽

Morphological Characteristics ◽

Aerial Mycelium ◽

Stem Canker ◽

Growth Stages ◽

Internal Transcribed Spacer Region ◽

First Report ◽

Glycine Max L ◽

Soybean Plants

In October 2018, soybean plants displaying elongated black to reddish-brown lesions on stems were observed in a field planted to the cv. BRS Serena in the locality of Puerto López (Meta, Colombia), with 20% incidence of diseased plants. Symptomatic stems were collected from five plants, and small pieces (∼5 mm2) were surface sterilized, plated on potato dextrose agar (PDA) and incubated for 2 weeks at 25°C in darkness. Three fungal isolates with similar morphology were obtained, i.e., by subculturing single hyphal tips, and their colonies on PDA were grayish-white, fluffy, with aerial mycelium, dark colored substrate mycelium, and produced circular black stroma. Pycnidia were globose, black, occurred as clusters, embedded in tissue, erumpent at maturity, with an elongated neck, and often had yellowish conidial cirrus extruding from the ostiole. Alpha conidia were observed for all isolates after 30 days growth on sterile soybean stem pieces (5 cm) on water agar, under 25ºC and 12 h light/12h darkness photoperiod. Alpha conidia (n = 50) measured 6.0 – 7.0 µm (6.4 ± 0.4 µm) × 2.0 – 3.0 µm (2.5± 0.4 µm), were aseptate, hyaline, smooth, ellipsoidal, often biguttulate, with subtruncate base. Beta conidia were not observed. Observed morphological characteristics of these isolates were similar to those reported in Diaporthe spp. by Udayanga et al. (2015). DNA from each fungal isolate was used to sequence the internal transcribed spacer region (ITS), and the translation elongation factor 1-α (TEF1) gene, using the primer pairs ITS5/ITS4 (White et al. 1990) and EF1-728F/EF1- 986R (Carbone & Kohn, 1999), respectively. Results from an NCBI-BLASTn, revealed that the ITS sequences of the three isolates (GenBank accessions MW566593 to MW566595) had 98% (581/584 bp) identity with D. miriciae strain BRIP 54736j (NR_147535.1), whereas the TEF1 sequences (GenBank accessions MW597410 to MW597412) had 97 to 100% (330-339/339 bp) identity with D. ueckerae strain FAU656 (KJ590747). The species Diaporthe miriciae R.G. Shivas, S.M. Thomps. & Y.P. Tan, and Diaporthe ueckerae Udayanga & Castl. are synonymous, with the latter taking the nomenclature priority (Gao et al. 2016). According to a multilocus phylogenetic analysis, by maximum likelihood, the three isolates clustered together in a clade with reference type strains of D. ueckerae (Udayanga et al. 2015). Soybean plants cv. BRS Serena (growth stages V3 to V4) were used to verify the pathogenicity of each isolate using a toothpick inoculation method (Mena et al. 2020). A single toothpick colonized by D. ueckerae was inserted directly into the stem of each plant (10 plants per isolate) approximately 1 cm below the first trifoliate node. Noncolonized sterile toothpicks, inserted in 10 soybean plants served as the non-inoculated control. Plants were arbitrarily distributed inside a glasshouse, and incubated at high relative humidity (>90% HR). After 15 days, inoculated plants showed elongated reddish-brown necrosis at the inoculated sites, that were similar to symptoms observed in the field. Non-inoculated control plants were asymptomatic. Fungal cultures recovered from symptomatic stems were morphologically identical to the original isolates. This is the first report of soybean stem canker caused by D. ueckerae in Colombia. Due to the economic importance of this disease elsewhere (Backman et al. 1985; Mena et al. 2020), further research on disease management strategies to mitigate potential crop losses is warranted.

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First Report of Fusarium proliferatum Causing Rot of Garlic Bulbs (Allium sativum) in India

Plant Disease ◽

10.1094/pdis-08-11-0649 ◽

2012 ◽

Vol 96 (2) ◽

pp. 290-290 ◽

Cited By ~ 9

Author(s):

N. Ravi Sankar ◽

Gundala Prasad Babu

Keyword(s):

Sodium Hypochlorite ◽

Allium Sativum ◽

Morphological Characteristics ◽

Aerial Mycelium ◽

Its Region ◽

Fusarium Proliferatum ◽

Distilled Water ◽

Sequence Comparisons ◽

First Report ◽

Plant Pathol

In September 2009, diseased garlic bulbs (Allium sativum L. cv. Yamuna Safed) were received from producers and exporters in Hyderabad, Andra Pradesh, India. From 2009 to 2010, similar symptoms were observed on stored garlic bulbs (cvs. Yamuna Safed and Agrifound White) in Chittoor, Kadapa, and Hyderabad districts. In some locations, approximately 60% of the garlic bulbs were affected. At first, infected bulbs showed water-soaked, brown spots and then the disease progressed as small, slightly depressed, tan lesions. A total of 120 diseased samples were collected from all localities. Infected tissues were surface sterilized in 1% sodium hypochlorite for 2 min, rinsed three times in sterile distilled water, plated on potato dextrose agar (PDA), and incubated at 25°C for 7 days. Resultant fungal colonies were fast growing with white aerial mycelium and violet to dark pigments. Hyphae were septate and hyaline. Conidiophores were short, simple, or branched. Microconidia were abundant, single celled, oval or club shaped, measuring 4.5 to 10.5 × 1.3 to 2.5 μm, and borne in chains from both mono-and polyphialides. Macroconidia were not produced. On the basis of morphological characteristics, the pathogen was identified as Fusarium proliferatum (Matsushima) Nirenberg (2). Identification was confirmed by amplification of the internal transcribed spacer (ITS) region. Genomic DNA was extracted from pure cultures of an isolate, and the ITS region was amplified using the ITS4/5 primer pair. PCR amplicons of approximately 574 bp were obtained from isolates, and sequence comparisons with GenBank showed 99% similarity with F. proliferatum (Accession No. FN868470.1). Sequence from this study was submitted to GenBank nucleotide database (Accession No. AB646795). Pathogenicity tests were conducted with three isolates of the fungus following the method of Dugan et al. (1). Each assay with an isolate consisted of 10 garlic cloves disinfected in 1% sodium hypochlorite for 45 s, rinsed with sterile distilled water, and injured to a depth of 4 mm with a sterile 1-mm-diameter probe. The wounds were filled with PDA colonized by the appropriate isolate from a 5-day-old culture. Ten cloves for each tested isolate received sterile PDA as a control. The cloves were incubated at 25°C for 5 weeks; tests were repeated once. After 17 days, rot symptoms similar to the original symptoms developed on all inoculated cloves and F. proliferatum was consistently reisolated from symptomatic tissue, fulfilling Koch's postulates. No fungi were recovered from control cloves. F. proliferatum has been reported on garlic in the northwestern United States (1), Serbia (4), and Spain (3). To our knowledge, this is the first report of F. proliferatum causing rot disease on garlic bulbs in India. References: (1) F. M. Dugan et al. Plant Pathol. 52:426, 2003. (2) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Publishing, Oxford, UK, 2006. (3) D. Palmero et al. Plant Dis. 94:277, 2010. (4) S. Stankovic et al. Eur. J. Plant Pathol. 48:165, 2007.

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First Report of Fusarium ipomoeae Causing Peanut leaf Spot in China

Plant Disease ◽

10.1094/pdis-01-21-0226-pdn ◽

2021 ◽

Author(s):

Manlin Xu ◽

Xia Zhang ◽

Jing Yu ◽

zhiqing Guo ◽

Ying Li ◽

...

Keyword(s):

Leaf Spot ◽

Genomic Dna ◽

Block Design ◽

Management Strategies ◽

Morphological Characteristics ◽

Ethanol Solution ◽

Distilled Water ◽

Conidial Suspension ◽

Internal Transcribed Spacer Region ◽

First Report

Peanut (Arachis hypogaea L.) is one of the most economically important crops as an important source of edible oil and protein. In August 2020, circular to oval-shaped brown leaf spots (2-6 mm in diameter) with well-defined borders surrounded by a yellow margin were observed on peanut plant leaves in Laixi City, Shandong Province, China. Symptomatic plants randomly distributed in the field, the incidence was approximately 5%. Leave samples were collected consisted of diseased tissue and the adjacent healthy tissue. The samples were dipped in a 70% (v/v) ethanol solution for 30 s and then soaked in a 0.1% (w/v) mercuric chloride solution for 60 s. The surface-sterilized tissues were then rinsed three times with sterile distilled water, dried and placed on Czapek Dox agar supplemented with 100 μg/ml of chloramphenicol. The cultures were incubated in darkness at 25 °C for 3–5 days. Fungal colonies were initially white and radial, turning to orange-brown in color, with abundant aerial mycelia. Macroconidia were abundant, 4 to 7 septate, with a dorsiventral curvature, and were 3.3–4.5 × 18.5–38.1 μm (n=100) in size; microconidia were absent; chlamydospores were produced in chains or clumps, ellipsoidal to subglobose, and thick walled. The morphological characteristics of the conidia were consistent with those of Fusarium spp. To identify the fungus, an EasyPure Genomic DNA Kit (TransGEN, Beijing, China) was used to extract the total genomic DNA from mycelia. The internal transcribed spacer region (ITS rDNA) and the translation elongation factor 1-α gene (TEF1) were amplified with primers ITS1/ITS4 (White et al. 1990) and EF1/EF2 (O’Donnell et al. 1998), respectively. Based on BLAST analysis, sequences of ITS (MT928727) and TEF1 (MT952337) showed 99.64% and 100% similarity to the ITS (MT939248.1), TEF1 (GQ505636.1) of F. ipomoeae isolates. Sequence analysis confirmed that the fungus isolated from the infected peanut was F. ipomoeae (Xia et al. 2019). The pathogenicity of the fungus was tested in the greenhouse. Twenty two-week-old peanut seedlings (cv. Huayu20) grown in 20-cm pots (containing autoclaved soil) were sprayed with a conidial suspension (105 ml−1) from a 15-day-old culture. Control plants were sprayed with distilled water. The experiment was conducted as a randomized complete block design, and placed at 25 °C under a 12-h photoperiod with 90% humidity. Symptoms similar to those in the field were observed on leaves treated with the conidial suspension ten days after inoculation, but not on control plants. F. ipomoeae was re-isolated from symptomatic leaves but not from the control plants. Reisolation of F. ipomoeae from inoculated plants fulfilled Koch's postulates. To our knowledge, this is the first report of F. ipomoeae causing peanut leaf spot in China. Our report indicates the potential spread of this pathogen in China and a systematic survey is required to develop effective disease management strategies.

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First Report of a Chaetomella sp. Causing a Leaf Spot on Sansevieria trifasciata in China

Plant Disease ◽

10.1094/pdis-10-12-0993-pdn ◽

2013 ◽

Vol 97 (7) ◽

pp. 992-992 ◽

Cited By ~ 4

Author(s):

Y. L. Li ◽

Z. Zhou ◽

W. Lu ◽

J. R. Ye

Keyword(s):

Leaf Spot ◽

Disease Incidence ◽

Morphological Characteristics ◽

Leaf Tissue ◽

Aerial Mycelium ◽

Control Treatment ◽

Distilled Water ◽

First Report ◽

Potted Plants ◽

Fungal Isolates

Sansevieria trifasciata originates from tropical West Africa. It is widely planted as a potted ornamental in China for improving indoor air quality (1). In February 2011, leaves of S. trifasciata plants in an ornamental market of Anle, Luoyang City, China, were observed with sunken brown lesions up to 20 mm in diameter, and with black pycnidia present in the lesions. One hundred potted plants were examined, with disease incidence at 20%. The symptomatic leaves affected the ornamental value of the plants. A section of leaf tissue from the periphery of two lesions from a plant was cut into 1 cm2 pieces, soaked in 70% ethanol for 30 s, sterilized with 0.1% HgCl2 for 2 min, then washed five times in sterilized distilled water. The pieces were incubated at 28°C on potato dextrose agar (PDA). Colonies of two isolates were brown with submerged hyphae, and aerial mycelium was rare. Abundant and scattered pycnidia were reniform, dark brown, and 200 to 350 × 100 to 250 μm. There were two types of setae on the pycnidia: 1) dark brown setae with inward curved tops, and 2) straight, brown setae. Conidia were hyaline, unicellular, cylindrical, and 3.75 to 6.25 × 1.25 to 2.50 μm. Morphological characteristics suggested the two fungal isolates were a Chaetomella sp. To confirm pathogenicity, six mature leaves of a potted S. trifasciata plant were wounded with a sterile pin after wiping each leaf surface with 70% ethanol and washing each leaf with sterilized distilled water three times. A 0.5 cm mycelial disk cut from the margin of a 5-day-old colony on a PDA plate was placed on each pin-wounded leaf, ensuring that the mycelium was in contact with the wound. Non-colonized PDA discs were placed on pin-wounded leaves as the control treatment. Each of two fungal isolates was inoculated on two leaves, and the control treatment was done similarly on two leaves. The inoculated plant was placed in a growth chamber at 28°C with 80% relative humidity. After 7 days, inoculated leaves produced brown lesions with black pycnidia, but no symptoms developed on the control leaves. A Chaetomella sp. was reisolated from the lesions of inoculated leaves, but not from the control leaves. An additional two potted plants were inoculated using the same methods as replications of the experiment, with identical results. To confirm the fungal identification, the internal transcribed spacer (ITS) region of rDNA of the two isolates was amplified using primers ITS1 and ITS4 (2) and sequenced. The sequences were identical (GenBank Accession No. KC515097) and exhibited 99% nucleotide identity to the ITS sequence of an isolate of Chaetomella sp. in GenBank (AJ301961). To our knowledge, this is the first report of a leaf spot of S. trifasciata caused by Chaetomella sp. in China as well as anywhere in the world. References: (1) X. Z. Guo et al. Subtropical Crops Commun. Zhejiang 27:9, 2005. (2) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, San Diego, CA, 1990.

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First Report of Colletotrichum clavatum Causing Quince Anthracnose in Serbia

Plant Disease ◽

10.1094/pdis-01-14-0052-pdn ◽

2014 ◽

Vol 98 (9) ◽

pp. 1272-1272

Author(s):

S. Živković ◽

V. Gavrilović ◽

T. Popović ◽

N. Dolovac ◽

N. Trkulja

Keyword(s):

Management Practices ◽

Morphological Characteristics ◽

Aerial Mycelium ◽

Fruit Trees ◽

Morphological Identification ◽

Distilled Water ◽

First Report ◽

Mediterranean Countries ◽

Wide Range ◽

Plant Pathol

Quince (Cydonia oblonga Mill.) tree is traditionally grown in Serbia. The fruits are used for compote, marmalade, and brandy production. In December 2012, quince fruits cv. Leskovacka with symptoms of postharvest anthracnose were collected in a storage facility in the area of Sabac, western Serbia. The symptoms were observed on fruits approximately 2 months after harvest. The incidence of the disease was about 3%, but the symptoms were severe. Affected fruits showed sunken, dark brown to black lesions with orange conidial masses produced in black acervuli. Small pieces (3 to 5 mm) of necrotic tissue were surface sterilized for 1 min in 1% NaOCl, washed twice with sterile distilled water, and placed on potato dextrose agar (PDA). Macroscopic and microscopic morphology characteristics of three isolates were observed after growth on PDA for 7 days at 25°C under a 12-h photoperiod. Fungal colonies developed white to gray dense aerial mycelium with orange conidial masses in the center of the colony. Conidia were hyaline, aseptate, clavate with rounded distal apices, 15.2 (12.8 to 16.8) × 4.5 (4.0 to 5.2) μm (mean L/W ratio = 3.3, n = 100). Morphological characteristics are consistent with the description of Colletotrichum clavatum (2). Fungal isolates were also characterized by sequencing of the internal transcribed spacer (ITS) rDNA region using ITS1/IT4 primers and β-tubuline 2 gene using T1/T2 primers. The nucleotide sequences were deposited in GenBank (ITS Accession Nos. KF908866, KF908867, and KF908868; β-tubuline 2 gene KF908869, KF908870, and KF908871). BLAST analyses of ITS and β-tubuline 2 gene sequences showed that isolates from quince were 100% identical to other C. clavatum in GenBank (ITS JN121126, JN121130, JN121132, and JN121180; β-tubuline 2 gene JN121213 to 17, JN121219, JN121228, JN121261 to 62, and JN121266 to 69), thus confirming the morphological identification. To fulfill Koch's postulates, asymptomatic fruits of quince cv. Leskovacka (five fruits per isolate) were surface sterilized with 70% ethanol, wounded with a sterile needle, and inoculated with 50 μl of a spore suspension (1 × 106 conidia/ml). Five control fruits were inoculated with 50 μl of sterile distilled water. The experiment was repeated twice. After 10 days of incubation in plastic containers, under high humidity (>90% RH) at 25°C, typical anthracnose symptoms developed on inoculated fruits, while control fruits remained symptomless. The isolates recovered from symptomatic fruits showed the same morphological features as original isolates. C. clavatum previously indicated as group B (3), or genetic group A4 within the C. acutatum sensu lato complex (4), is responsible for olive anthracnose in some Mediterranean countries (1,2), and has been reported as causal agent of anthracnose on a wide range of other hosts including woody and herbaceous plants, ornamentals, and fruit trees worldwide (4). To our knowledge, this is the first report of C. clavatum in Serbia, and the first report of quince anthracnose caused by this pathogen in Europe. Anthracnose caused by C. clavatum can endanger the production and storage of quince in the future, and may require investigation of new disease management practices to control this fungus. References: (1) S. O. Cacciola et al. J. Plant Pathol. 94:29, 2012. (2) R. Faedda et al. Phytopathol. Mediterr. 50:283, 2011. (3) R. Lardner et al. Mycol. Res. 103:275, 1999. (4) S. Sreenivasaprasad and P. Talhinhas. Mol. Plant Pathol. 6:361, 2005.

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First Report of Rubber Tree Stem Rot Caused by Fusarium oxysporum in China

Plant Disease ◽

10.1094/pdis-01-14-0004-pdn ◽

2014 ◽

Vol 98 (7) ◽

pp. 1008-1008 ◽

Cited By ~ 3

Author(s):

B.-X. Li ◽

T. Shi ◽

X.-B. Liu ◽

C.-H. Lin ◽

G.-X. Huang

Keyword(s):

Fusarium Oxysporum ◽

Apical Cell ◽

Rubber Tree ◽

Morphological Characteristics ◽

Plant Diseases ◽

Tree Bark ◽

Stem Rot ◽

Tree Plantation ◽

Tropical Regions ◽

First Report

Rubber tree (Hevea brasiliensis) is an important crop in tropical regions of China. In October 2013, a new stem rot disease was found on cv. Yunyan77-4 at a rubber tree plantation in Hekou, Yunnan Province. There were about 100 plants, and diseased rubber trees accounted for 30% or less. Initially, brown-punctuate secretion appeared on the stem, which was 5 to 6 cm above the ground. Eventually, the secretion became black and no latex produced from the rubber tree bark. After removing the secretion, the diseased bark was brown putrescence, but the circumambient bark was normal. Upon peeling the surface bark, the inner bark and xylem had brown rot and was musty. The junction between health and disease was undulate. On the two most serious plants, parts of leaves on the crown were yellow, and the root near the diseased stem was dry and puce. The pathogen was isolated and designated HbFO01; the pathogenicity was established by following Koch's postulates. The pathogen was cultivated on a potato dextrose agar (PDA) plate at 28°C for 4 days. Ten plants of rubber tree cv. Yunyan77-4 were selected from a disease-free plantation in Haikou, Hainan Province, and the stem diameter was about 7 cm. The bark of five plants was peeled, and one mycelium disk with a diameter of 1 cm was inserted into the cut and covered again with the bark. The other five plants were treated with agar disks as controls. The inoculation site was kept moist for 2 days, and then the mycelium and agar disk were removed. On eighth day, symptoms similar to the original stem lesions were observed on stems of inoculated plants, while only scars formed on stems of control plants. The pathogen was re-isolated from the lesions of inoculated plants. On PDA plates, the pathogen colony was circular and white with tidy edges and rich aerial hyphae. Microscopic examination showed microconidia and chlamydospores were produced abundantly on PDA medium. The falciform macroconidia were only produced on lesions and were slightly curved, with a curved apical cell and foot shaped to pointed basal cell, usually 3-septate, 16.2 to 24.2 × 3.2 to 4.0 μm. Microconidia were produced in false heads, oval, 0-septate, 6.2 to 8.2 × 3.3 to 3.8 μm, and the phialide was cylindrical. Chlamydospores were oval, 6.4 to 7.2 × 3.1 to 3.8 μm, alone produced in hypha. Morphological characteristics of the specimen were similar to the descriptions for Fusarium oxysporum (2). Genomic DNA of this isolate was extracted with a CTAB protocol (4) from mycelium and used as a template for amplification of the internal transcribed spacer (ITS) region of rDNA with primer pair ITS1/ITS4 (1). The full length of this sequence is 503 nt (GenBank Accession No. KJ009335), which exactly matched several sequences (e.g., JF807394.1, JX897002.1, and HQ451888.1) of F. oxysporum. Williams and Liu had listed F. oxysporum as the economically important pathogen of Hevea in Asia (3), while this is, to our knowledge, the first report of stem rot caused by F. oxysporum on rubber tree in China. References: (1) D. E. L. Cooke et al. Fungal Genet. Biol. 30:17, 2000. (2) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual, 2006. (3) T. H. Williams and P. S. W. Liu. A host list of plant diseases in Sabah, Malaysia, 1976. (4) J. R. Xu et al. Genetics 143:175, 1996.

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First Report of Phyllosticta capitalensis Causing Black Freckle Disease on Rubus chingii in China

Plant Disease ◽

10.1094/pdis-05-21-1031-pdn ◽

2021 ◽

Author(s):

Wenhao Zhang ◽

Dan Su ◽

Rui Sun

Keyword(s):

Tap Water ◽

Morphological Characteristics ◽

Guizhou Province ◽

Broad Host Range ◽

Distilled Water ◽

Conidial Suspension ◽

First Report ◽

Representative Isolate ◽

Rubus Chingii ◽

Phyllosticta Capitalensis

Rubus chingii is used as an important traditional Chinese medicine, and belongs to the family Rosaceae. The fruit has multiple pharmacological activities, including antioxidant, anti-inflammatory, and improving cognitive impairment (Na Han et al. 2012). In June 2019, a new fungal infection was observed on the leaves of R. chingii in Qiandongnan Miao and Dong Autonomous Prefecture, Guizhou Province, China, forming small lesions with reddish-brown edges along leaf veins. Over 500 plants were surveyed, and nearly 20% of the plants were symptomatic. The diseased plants grew poorly and appeared stunted, and severely affected plants died. Five symptomatic leaves were randomly collected from the field and washed with tap water and distilled water successively. The edges of infected leaf tissue were cut into small pieces (4 to 5 mm2), surface sterilized with 70% ethanol for 30 s and 0.1% HgCl2 for 1 minute, and then rinsed three times in sterile distilled water (Chen et al. 2016). The same fungus was isolated from 41 pieces. The hyphae of a representative isolate were gray, the colony surface was granular, the edges were uneven and white, and the culture turned black over time with black spherical conidia. Conidia were nearly elliptical, unicellular, and each with a hyaline, unstable apical appendage, 3 to 10 µm long. The size of conidia was 10 to 18 μm in length and 4 to 8 μm in width. These morphological characteristics are consistent with those described for the fungus Phyllosticta capitalensis. (Wikee et al. 2013). For an accurate identification, genomic DNA of a representative isolate of the pathogen was extracted to amplify the internal transcribed spacer (ITS) region, the transcription elongation factor (tefa-1), and actin (ACT) genes with the ITS1/ITS4, EF1-728F/EF1-986R, and ACT-512F/ACT-783R (Cheng, L. L. ,et al. 2019), respectively. The ITS, tefa-1 and actin gene sequences were deposited in GenBank and assigned accession numbers MW308365, MW714380 and MW714381, respectively. BLAST search analysis of GenBank (NCBI) showed that the sequences had 100% similarity with those of Phyllosticta capitalensis (GenBank accession no. ITS, MN548091; tefa-1, MN958711; and ACT, MN565575). The pathogenicity of Phyllosticta capitalensis was verified using six healthy detached leaves from healthy R. chingii plants around 40 cm tall. A total of nine plants were used, and three leaves from each plant were artificially inoculated. Each wound was inoculated with conidial suspension (106 mL-1), while the control leaves were coated by sterile water. All the treated plants were covered with plastic bags for 2 days, incubated at 28ºC and 85% relative humidity, with a 12-hour photoperiod. After 15 days following inoculation, the injured leaves showed similar symptoms to the above-mentioned lesions, while the control and uninjured leaves were still healthy. P. capitalensis were reisolated from inoculated leaves, fulfilling Koch’s postulates. P. capitalensis is an endophyte, widely distributed in various host plants in China. (Lu, J. M, et al. 2016). To the best of our known, this is the first report of black freckle disease caused by P. capitalensis on Rubus chingii in China. P. capitalensis is a destructive plant pathogen with an unusually broad host range and our findings will be useful for its management and for further research. The author(s) declare no conflict of interest.

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First Report of Fusarium Wilt of Strawberry Caused by Fusarium oxysporum in South Carolina

Plant Disease ◽

10.1094/pdis-02-12-0164-pdn ◽

2012 ◽

Vol 96 (6) ◽

pp. 911-911 ◽

Cited By ~ 4

Author(s):

M. Williamson ◽

D. Fernández-Ortuño ◽

G. Schnabel

Keyword(s):

South Carolina ◽

Fusarium Oxysporum ◽

Fusarium Wilt ◽

The United States ◽

Crown Rot ◽

Distilled Water ◽

Conidial Suspension ◽

Internal Transcribed Spacer Region ◽

Clemson University ◽

First Report

During October 2011, wilted and dead strawberry (Fragaria × ananassa cv. Albion) plants from two commercial fields in South Carolina were sent to the Clemson University Plant Problem Clinic in Pendleton, SC. Symptoms consisted of wilting and chlorosis of foliage, scorch and dieback of older leaves, and stunting of plants. Internal vascular and cortical tissues of plant crowns showed a distinct reddish brown discoloration. To isolate the causal agent, necrotic crown tissue selected from two symptomatic plants from one location and four symptomatic plants from the other were placed on acidified potato dextrose agar (APDA) and on quarter strength acidified PDA (QPDA). Colonies with light purple mycelia and beige or orange reverse colony colors developed on APDA after 5 days of incubation at 25°C. Colonies on QPDA were light purple. Morphology, growth, and development of macroconidia and microconida were consistent with descriptions of Fusarium oxysporum Schlechtend emend. Snyder & Hansen (3). Genomic DNA from 3 isolates (11-1246A, 11-1247A, and 11-1247B) was extracted and purified according to Chi et al. (1). The internal transcribed spacer region comprising ITS1, ITS2, and 5.8S rRNA was amplified by primers ITS1 and ITS4 (4). The sequence comparison revealed a 100% match with F. oxysporum sequences in GenBank. To confirm the pathogenicity of the fungus, roots of 15 strawberry plants (cv. Albion) were cut and then five plants were soaked for 10 min in either 500 ml of conidial suspension (104 conidia/ml) of one of the two isolates or in sterile distilled water. All were then potted in 15-cm pots with artificial peat-based soil mix and maintained at 25°C in the greenhouse. After 6 weeks, all plants inoculated with isolates 1247A and B were stunted and developed wilt symptoms similar to those observed in the field, while the control plants remained healthy. Support roots on all affected plants were soft and flaccid and new feeder roots had brown lesions. Crowns of three plants inoculated with isolate 1247A and four plants inoculated with 1247B showed vascular discoloration. To reisolate, crowns were plated as above and roots were surface sterilized in 10% bleach for 1 min and rinsed in sterile distilled water prior to plating on QPDA. F. oxysporum was isolated at frequencies of 70 and 100% from crowns and 100% from roots of all inoculated plants. To our knowledge, this is the first report of the occurrence of Fusarium wilt caused by F. oxysporum on strawberry plants in South Carolina. The presence of Fusarium wilt in South Carolina should alert growers, county agents, and specialists to properly identify Fusarium wilt symptoms, which may be confused with Anthracnose or Phytophthora crown rot of strawberry. The disease has been reported previously in other countries including the United States (2). References: (1) M. H. Chi et al. Plant Pathol. J. 25:108, 2009. (2) S. T. Koike et al. Plant Dis. 93:1077, 2009. (3) W. C. Snyder and H. N. Hansen. Am. J. Bot. 27:64, 1940. (4) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Application. Academic Press, NY, 1993.

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First Report of Fusarium oxysporum Causing Wilt on Coriander in China

Plant Disease ◽

10.1094/pdis-05-21-1002-pdn ◽

2021 ◽

Author(s):

Xin Li ◽

Hua-jun Kang ◽

Qian Zhao ◽

Yanxia Shi ◽

Ali Chai ◽

...

Keyword(s):

Fusarium Oxysporum ◽

Genomic Dna ◽

Morphological Identification ◽

Broad Host Range ◽

Pathogenicity Test ◽

Distilled Water ◽

Conidial Suspension ◽

First Report ◽

Leaf Yellowing ◽

Vascular Discoloration

Coriander (Coriandrum sativum L), which belongs to the family Apiaceae, is a medicinal and aromatic plant. In China, coriander is widely cultivated in several parts as a vegetable crop. During August 2019 to June 2020, wilting symptoms were observed on coriander (cv. 'Tiegan') in a commercial plantation, with disease incidence of approximately 25 to 40% in Xiajiawang village (118°88′E, 35°46′N) of Linyi city, Shandong province, China. Symptoms included wilting and leaf yellowing, plant stunting, root rot, and vascular discoloration of the stem bases and roots. A total of eight symptomatic plants were uprooted and collected from three fields. To determine the cause of the disease, symptomatic root tissues were excised, surface disinfected with 75% ethanol for 30s, followed by three washes with sterile distilled water, and then placed on potato dextrose agar (PDA) and incubated at 28°C for 6 days. In total, 10 cultures were obtained and purified by single-spore subcultures on PDA for morphological identification. The morphology of multiple colonies was consistent and originally white, later becoming light to dark purple in color with abundant aerial hyphae. Macroconidia were hyaline and falcate, straight to slightly curved, 3-4 septate, 27.86 to 34.23 × 4.07 to 6.13 μm (n = 30), with apical cells curved and basal cells foot-shaped. Microconidia were hyaline, oval or ellipsoid, 0-1 septate, with a flat base, measuring 5.67 to 9.37 × 3.66 to 5.40 μm (n = 30). These morphological characteristics resembled those of Fusarium oxysporum (Leslie and Summerell 2006). Genomic DNA was extracted from fungal mycelium using the Plant Genomic DNA Kit (Tiangen, China). The nuclear ribosomal internal transcribed spacer (ITS), translation elongation factor 1-alpha (TEF-1α) and mitochondrial small subunit (mtSSU) genes were amplified with primer pairs ITS1/ITS4 (White et al. 1990), EF1Ha/EF2Tb (O’ Donnell et al. 1998) and NMS1a/NMS2b (Li et al. 1994). The resulting ITS (550-bp), TEF1-α (681-bp) and mtSSU (692-bp) sequences of isolate QC20091601 were deposited in GenBank (accession nos. MW900439, MW692008 and MW711738, respectively). BLAST analysis demonstrated 100% identities to the ITS, TEF-1α and mtSSU sequences of F. oxysporum (MN856370.1, MN507110.1 and MN386808.1), respectively. According to the morphological and molecular identification, the fungus was identified as F. oxysporum. In the pathogenicity test, healthy coriander plants (cv. 'Tiegan') at the 4-true-leaf stage were inoculated by dipping the roots into a conidial suspension of 1 × 107 conidia/mL for 10 min. Plants dipped in sterile distilled water served as controls. All treated plants were placed in a greenhouse maintained at temperature 30°C and 80% relative humidity. Ten days later, inoculated plants developed typical symptoms of leaf yellowing, wilting and vascular discoloration, which were identical to those observed in the fields, whereas the control plants remained healthy. F.oxysporum was reisolated from the symptomatic roots, and its identity was confirmed by PCR with the primes described above, fulfilling Koch's postulates. To our knowledge, this is the first report of F. oxysporum as a pathogen on coriander in China. F. oxysporum is a destructive plant pathogen with an unusually broad host range and worldwide distribution, prevention and control measures should be taken in advance.

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