First Report of Anthracnose on Fruits of Duchesnea indica Caused by Colletotrichum acutatum in Northwestern Argentina

Duchesnea indica (Andrews) Focke, a cosmopolitan wild species related to the cultivated strawberry that is widely distributed in northwestern Argentina, grows in close proximity to strawberry crops and has proven to be almost immune to Colletotrichum spp. isolated from diseased strawberry plants (1), hence it has never been considered a phytopathological risk. During a field survey of “La Heladera” (27°01′45″S, 65°39′20″W), Tafí del Valle (Tucumán, Argentina) from November 2009 to November 2010, a genotype of D. indica showing fruits with dark brown, necrotic, irregular, circular lesions of 5 to 20 mm in diameter were collected. Setose acervuli were observed on the center of the fruit lesions. Pathogens were obtained from 10 diseased fruit collected at random, and four fungal isolates were isolated per fruit on potato dextrose agar (PDA). To reduce the number of samples for evaluation, two isolates per fruit that were exhibiting stable but distinctive morphological features were chosen to continue the studies. Isolates were characterized by morphological, molecular, and phytopathological criteria. After 10 days of incubation on PDA medium at 28°C with continuous white light, colonies exhibited a gray, aerial mycelium, whereas the reverse of the colony is a pale maroon with a radial, pale salmon color. Masses of salmon-colored conidia formed in the center of the colonies. Conidia were hyaline, one celled, fusiform, tapered to a point at both ends, and measured 14.8 to 17.3 × 4.5 to 7.4 μm (n = 100). Setae were scarce and sclerotia were absent. All morphological characteristics that were observed indicated that the isolates were C. acutatum (3). To fulfill Koch's postulates and verify the pathogenicity on commercial varieties of strawberry, six healthy plants of D. indica and Fragaria × ananassa cv. Camarosa with mature fruits were used to test each isolate. Four plants were spray inoculated with conidial suspensions of the virulent isolates (1.5 × 106 conidia/ml) and two with sterile distilled water as controls. Both treatments were maintained under white light (2,000 lux, 12 h per day) at 28°C and 70% relative humidity. Nine days after the inoculation, dark brown lesions and salmon-colored masses of conidia were observed only in inoculated fruits of both genotypes. The fungus isolated from diseased fruits and the conidia that were produced were identical to the isolates used to inoculate the plants. To confirm pathogen identity, PCR amplification with the species-specific pair of primer CaInt2/ITS4 (4) were carried out using fungal total DNA from the original isolates and isolates obtained from inoculated fruits. An amplification product of approximately 490 bp, which is specific for C. acutatum, was observed in all DNA samples (4). Although C. acutatum has already been reported in Fragaria × ananassa in Argentina (2), to our knowledge, this is the first report of C. acutaum causing anthracnose in D. indica species. This result is relevant since this species grows close to strawberry fields and can be an alternative host and potential vector of the anthracnose disease agent. References: (1) M. E. Arias. Frutillas Silvestres y Especies Relacionadas con la Cultivada. EDUNT, Argentina, 2007. (2) C. J. Ramallo et al. Plant Dis. 84:706. 2000. (3) B. J. Smith and L. L. Black. Plant Dis. 74:69, 1990. (4) S. Sreenivasaprasad et al. Plant Pathol. 45:650, 1996.

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First Report of Colletotrichum gloeosporioides on Strawberry in Northwestern Argentina

Plant Disease ◽

10.1094/pdis.2000.84.5.595c ◽

2000 ◽

Vol 84 (5) ◽

pp. 595-595 ◽

Cited By ~ 4

Author(s):

M. E. Mónaco ◽

S. M. Salazar ◽

A. Aprea ◽

J. C. Díaz Ricci ◽

J. C. Zembo ◽

...

Keyword(s):

White Light ◽

Colletotrichum Gloeosporioides ◽

Morphological Characteristics ◽

Fragaria Ananassa ◽

Disease Symptoms ◽

Northwestern Argentina ◽

First Report ◽

Spray Inoculation ◽

Strawberry Anthracnose ◽

Pathogenicity Tests

Colletotrichum gloeosporioides was isolated from symptomatic strawberry (Fragaria × ananassa Duch. ‘Chandler’) growing in Lules (Tucumán, Argentina). Isolates were characterized based on several criteria. Potato dextrose agar (PDA) was used to evaluate cultural and morphological characteristics of the isolates. After 10 days on PDA at 28°C under continuous white light, colonies showed abundant aerial, cottony white to pale beige growth, with orange asexual fruiting bodies in older colonies. Isolates displayed cylindrical conidia, rounded at both ends, averaging 10.4 × 3.9 µm (length by width). A sexual phase (perithecia) was observed in all isolates in 2-month-old cultures on PDA at 28°C under continuous white light. Pathogenicity tests were conducted with healthy plants of cvs. Pájaro and Chandler. Spray inoculation with conidial suspensions (106 conidia per ml) resulted in disease symptoms (petiole and crown lesions with wilting of crown-infected plants) 7 days after inoculation. Infection progressed at a higher rate in Pájaro than in Chandler. Reisolations from infected strawberry lesions yielded isolates with characteristics identical to the isolate used to inoculate the host. Based on morphological and cultural characteristics, isolates were identified as C. gloeosporioides Penz. & Sacc. (teleomorph Glomerella cingulata Spauld & H. Schenk) (1). This is the first report of C. gloeosporioides causing strawberry anthracnose in northwestern Argentina. Reference: (1) P. S. Gunnell and W. D. Gubler. Mycol. 84:157, 1992.

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First Report of Anthracnose Fruit Rot Caused by Colletotrichum acutatum on Strawberry in Denmark

Plant Disease ◽

10.1094/pd-89-0432b ◽

2005 ◽

Vol 89 (4) ◽

pp. 432-432 ◽

Cited By ~ 6

Author(s):

T. Sundelin ◽

M. Schiller ◽

M. Lübeck ◽

D. F. Jensen ◽

K. Paaske ◽

...

Keyword(s):

Morphological Characteristics ◽

Aerial Mycelium ◽

Fruit Rot ◽

Colletotrichum Acutatum ◽

Enzyme Linked Immunosorbent Assay ◽

First Report ◽

Small Fruit ◽

Quarantine Pathogen ◽

Species Specific ◽

Pointed End

Strawberry (Fragaria × ananassa) is the most important small fruit crop in Denmark. The quarantine pathogen Colletotrichum acutatum was detected for the first time in June 2000 in Denmark in a production field on the island of Falster. Strawberry plants of cv. Kimberly showed typical symptoms of anthracnose fruit rot. On mature fruits, brown-to-black lesions with spore masses that were orange to salmon in color were observed. Mummified berries were also observed. The fungus was isolated and identified on the basis of morphological characteristics, and identification was confirmed using enzyme-linked immunosorbent assay at the Central Science Laboratory, York, U.K. Species-specific polymerase chain reaction with the C. acutatum-specific primer pairs acut1/col2 (1) and CaInt2/ITS4 (3) also supported the identification. Additionally, the internal transcribed spacer regions, ITS1 and ITS2, of the ribosomal DNA were sequenced in both directions (GenBank Accession No. AY818361). Homology searches with this sequence using BLAST also confirmed the identity. Colonies grown on potato dextrose agar developed white-to-grey aerial mycelium with salmon-colored spore masses, and were beige to black on the reverse side. Conidia were 11.3 (7.3 to 16.6) μm × 3.9 (2.5 to 5.2) μm, hyaline, cylindrical with at least one pointed end, and aseptate. Mycelial growth rate was 8.4 mm per day at 25°C which is similar to earlier reports (2). Spray-inoculated (106 conidia per ml) strawberry fruits cv. Elsanta developed brown, sunken, irregular lesions with salmon-colored acervuli after 2 to 5 days at 25°C. Koch's postulates were fulfilled since the reisolated fungus from these lesions developed the same morphological characteristics as described above. To our knowledge, this is the first report of C. acutatum in Denmark. References: (1) P. V. Martinez-Culebras et al. J. Phytopathol. 151:135, 2003. (2) B. J. Smith et al. Plant Dis. 74:69, 1990. (3) S. Sreenivasaprasad et al. Plant Pathol. 45:650, 1996.

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First Report of Anthracnose Fruit Rot Caused by Colletotrichum acutatum on Strawberry in Korea

Plant Disease ◽

10.1094/pdis-92-8-1247c ◽

2008 ◽

Vol 92 (8) ◽

pp. 1247-1247 ◽

Cited By ~ 1

Author(s):

M. H. Nam ◽

T. I. Kim ◽

M. L. Gleason ◽

J. Y. Song ◽

H. G. Kim

Keyword(s):

Pcr Amplification ◽

Morphological Characters ◽

Fruit Rot ◽

Colletotrichum Acutatum ◽

Pathogenicity Test ◽

First Report ◽

Strawberry Anthracnose ◽

Dark Green ◽

Average Size ◽

Species Specific

Symptoms typical of anthracnose fruit rot; sunken, dark brown lesions on maturing fruits, were found in a commercial field of strawberry (Fragaria × ananassa) cv. Cal Giant in Yangyang County, Korea in May 2007. Masses of conidia were produced in acervuli in the center of lesions. The fungus was isolated on potato dextrose agar (PDA). Colonies grown on PDA were pale to mouse gray and became dark green to black in reverse. Conidia were formed in orange-to-salmon pink masses in the center of the culture. The average size of conidia on PDA was 15.2 × 4.6 μm, and they were hyaline, straight, cylindrical, with pointed ends, and aseptate (1). The fungus did not form an ascigerous stage in culture. Mycelial growth rate was 7.5 mm per day at 25°C on PDA. The identity of two isolates was confirmed as Colletotrichum acutatum J.H. Simmonds by PCR amplification using species-specific primers TBCA and TB5 (2), resulting in a characteristic 330-bp band on agarose gel. Morphological characters were in accordance with previous reports on C. acutatum. A pathogenicity test was conducted with five healthy plants of cvs. Cal Giant, Maehyang, Seolhyang, Kumhyang, Akihime, and Redpearl. After fruits and flowers were sprayed with a conidia suspension (105 conidia per ml), the plants were maintained at 10 to 25°C and 100% relative humidity in a greenhouse. As a control, five healthy plants were sprayed with sterile distilled water and incubated under the same conditions. Dark brown, water-soaked spots appeared on mature fruits of all cultivars after 5 days, and lesions on green fruits appeared on individual achenes. Flowers developed dark lesions, dried out, and died. No symptoms were found on the control plants. After the pathogen was reisolated from fruits and flowers lesions, the morphological characters developed in culture as described above. To our knowledge, this is the first report of C. acutatum causing strawberry anthracnose in Korea. References: (1) B. J. Smith and L. L. Black. Plant Dis. 74:69, 1990. (2) P. Talhinhas et al. Appl. Environ. Microbiol. 71:2987, 2005.

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First Report of Stalk Rot Disease of Sugarcane Caused by Phaeocytostroma sacchari in Mexico

Plant Disease ◽

10.1094/pdis-05-13-0563-pdn ◽

2014 ◽

Vol 98 (3) ◽

pp. 420-420

Author(s):

J. R. Saucedo Carabez ◽

S. Ochoa Ascencio ◽

J. M. Tovar Pedraza

Keyword(s):

White Light ◽

Vascular Tissue ◽

Morphological Characteristics ◽

Aerial Mycelium ◽

Saccharum Officinarum ◽

Sodium Hypochlorite Solution ◽

Internal Transcribed Spacer Region ◽

First Report ◽

Stalk Rot ◽

Rot Disease

In April 2009 and 2010, severe symptoms of stalk rot of sugarcane (Saccharum officinarum L.) plants cvs. MEX-79-431, MEX-69-749, and RB-73-9735 were observed in commercials fields located in southeast Michoacan state, Mexico. The diseased plants exhibited complete discoloration of foliage, ascendant necrosis and rot in the internal stalk tissue, and disintegration of vascular tissue. Symptoms were most evident in the nodes with intense purple coloration. Dead plants were observed. Two diseased plants of each cultivar were collected. Pieces of symptomatic stem tissue were surface sterilized with 2% sodium hypochlorite solution for 1 min, washed with sterile distilled water, dried on sterilized paper, and plated onto potato dextrose agar (PDA). Petri dishes were incubated at 22°C under continuous white light for 72 h. A fungus was consistently isolated. On PDA, colonies had sparse aerial mycelium in the center and dense in the margins with black masses of conidia. The fungus isolated was grown on dishes containing 2% water agar (WA) overlaid with pine needles and incubated at 22°C under continuous white light for 2 weeks to induce the formation of fruiting bodies. Pycnidia produced in WA were black, up to 500 μm in diameter, usually globose, blister shaped without peaks, scattered, and multilocular. Conidiophores were cylindrical, hyaline, 5 to 20 × 1.5 to 2 μm, and formed in the pycnidial cavity. Conidia were ellipsoidal to oblong, unicellular, pale brown to dark brown, 8.5 to 12.5 × 3 to 4.5 μm, biguttulate, and non-septate. Paraphyses were hyaline, aseptate, occasionally branched, and flexuous. On the basis of cultural and morphological characteristics, the fungus was identified as Phaeocytostroma sp. DNA from an isolate was extracted and the internal transcribed spacer region (ITS1-5.8S-ITS2) of rDNA was amplified using primers ITS1 and ITS4 (2). PCR products were purified and sequenced. The resulting sequence of 536 bp was deposited in GenBank (Accession No. KC893550). BLAST analysis showed a 99% similarity with the sequence of Phaeocytostroma sacchari (FR748047). Pathogenicity tests of an isolate of P. sacchari were performed on 6-month-old sugarcane plants (cvs. MEX-79-431, MEX-69-749, and RB-73-9735). A 1-cm-deep wound near the base of the stem was created with a sterilized needle. Mycelial plugs (9 mm diameter) of 6-day-old PDA cultures were deposited on wounds and wrapped with Parafilm. Four plants of each cultivar were inoculated and 12 control plants were treated similarly with PDA plugs instead of fungal inoculum. Plants were placed at 28°C and 95% relative humidity for 72 h. All the inoculated plants exhibited typical wilt symptoms 4 weeks after inoculation, whereas control plants remained healthy. P. sacchari was consistently re-isolated from artificially inoculated plants. To our knowledge, this is the first report of P. sacchari on sugarcane in Mexico. The occurrence of stalk rot disease of sugarcane caused by P. sacchari has been described causing severe losses in sugarcane-producing countries such as South Africa and India (1). References: (1) R. Viswanathan et al. Sugar Tech. 5: 61, 2003. (2) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.

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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 Botryosphaeria dothidea, Diplodia seriata, and Neofusicoccum luteum Associated with Canker and Dieback of Grapevines in Tunisia

Plant Disease ◽

10.1094/pdis-05-13-0530-pdn ◽

2014 ◽

Vol 98 (3) ◽

pp. 420-420 ◽

Cited By ~ 6

Author(s):

S. Chebil ◽

R. Fersi ◽

A. Yakoub ◽

S. Chenenaoui ◽

M. Chattaoui ◽

...

Keyword(s):

Morphological Characteristics ◽

Aerial Mycelium ◽

Its2 Region ◽

Pathogenicity Test ◽

Botryosphaeria Dothidea ◽

Diplodia Seriata ◽

First Report ◽

Grapevine Dieback ◽

Pinus Spp ◽

Neofusicoccum Luteum

In 2011, common symptoms of grapevine dieback were frequently observed in 2- to 5-year-old table grape (Vitis vinifera L.) cvs. in four vineyards located in northern Tunisia. The symptoms included dead spur and cordons, shoot dieback, and sunken necrotic bark lesions, which progressed into the trunk resulting in the death of large sections of the vine. Longitudinal and transversal sections of cordons and spurs from symptomatic vines revealed brown wedge-shaped cankers of hard consistency. Twelve symptomatic samples from spur and cordons were collected, surface disinfected by dipping into 5% (v/v) sodium hypochlorite for 2 min, and small pieces from the edge of necrotic and healthy tissue were removed and plated onto potato dextrose agar (PDA) at 25°C in the dark. Based on colony and conidia morphological characteristics, isolates were divided in three species, named Diplodia seriata, Botryosphaeria dothidea, and Neofusicoccum luteum. D. seriata colonies were gray-brown with dense aerial mycelium producing brown cylindric to ellipsoid conidia rounded at both ends and averaged 22.4 × 11.7 μm (n = 50). B. dothidea colonies were initially white with abundant aerial mycelium, gradually becoming dark green olivaceous. Conidia were fusiform to fusiform elliptical with a subobtuse apex and averaged 24.8 × 4.7 μm (n = 50). N. luteum colonies were initially pale to colorless, gradually darkening with age and becoming gray to dark gray producing a yellow pigment that diffuses into the agar. Conidia were hyaline, thin-walled, aseptate, fusiform to fusiform elliptical, and averaged 19.8 × 5.5 μm (n = 50). Identity of the different taxa was confirmed by sequence analyses of the internal transcribed spacer (ITS1-5.8S-ITS2) region of the rDNA and part of the elongation factor 1-alpha (EF1-α) gene. BLAST analysis of sequences indicated that six isolates were identified as D. seriata (GenBank: AY259094, AY343353), one isolate as B. dothidea (AY236949, AY786319) and one isolate as N. luteum (AY259091, AY573217). Sequences were deposited in GenBank under accessions from KC178817 to KC178824 and from KF546829 to KF546836 for ITS region and EF1-α gene, respectively. A pathogenicity test was conducted on detached green shoots cv. Italia for the eight Botryosphaeriaceae isolates. Shoots were inoculated by placing a colonized agar plug (5 mm diameter) from the margin of a 7-day-old colony on fresh wound sites made with a sterilized scalpel. Each wound was covered with moisturized cotton and sealed with Parafilm. Control shoots were inoculated using non-colonized PDA plugs. After 6 weeks, discoloration of xylem and phloem and necrosis with average length of 38.8, 17.6, and 11.2 mm were observed from inoculated shoots with D. seriata, N. luteum, and B. dothidea, respectively, and all three fungi were re-isolated from necrotic tissue, satisfying Koch's postulates. Control shoots showed no symptoms of the disease and no fungus was re-isolated. In Tunisia, Botryosphaeria-related dieback was reported only on citrus tree caused by B. ribis (2), on Pinus spp. caused by D. pinea (4), on Quercus spp. caused by D. corticola (3), and on olive tree (Olea europea) caused by D. seriata (1). To our knowledge, this is the first report of D. seriata, B. dothidea, and N. luteum associated with grapevine dieback in Tunisia. References: (1) M. Chattaoui et al. Plant Dis. 96:905, 2012. (2) H. S. Fawcett. Calif. Citrogr. 16:208, 1931. (3) B. T. Linaldeddu et al. J. Plant Pathol. 91:234. 2009. (4) B. T. Linaldeddu et al. Phytopathol. Mediterr. 47:258, 2008.

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First Report of Clubroot on Capsella bursa-pastoris Caused by Plasmodiophora brassicae in Sichuan Province of China

Plant Disease ◽

10.1094/pdis-04-13-0395-pdn ◽

2014 ◽

Vol 98 (5) ◽

pp. 687-687 ◽

Cited By ~ 2

Author(s):

L. Ren ◽

X. P. Fang ◽

C. C. Sun ◽

K. R. Chen ◽

F. Liu ◽

...

Keyword(s):

Plasmodiophora Brassicae ◽

Tap Water ◽

Disease Incidence ◽

Morphological Characteristics ◽

Pcr Amplification ◽

Sichuan Province ◽

Clubroot Disease ◽

Cruciferous Vegetable ◽

First Report ◽

Resting Spores

Shepherd's purse (Capsella bursa-pastoris (L.) Medicus) is an edible and wild medicinal plant widely distributed in China. This plant has been cultivated in Shanghai, China, since the end of the 19th century. Infection of C. bursa-pastoris by Plasmodiophora brassicae, the causal agent of clubroot disease on Brassica spp. has been reported in Korea (2), but is not known to occur in China. In February of 2011, stunted and wilted shepherd's purse (SP) plants were observed in a field planted to oilseed rapes (B. napus) in Sichuan Province of China. Symptomatic SP plants also exhibited root galls. Disease incidence was 6.2% and 100% for SP and B. napus, respectively. Root galls on diseased SP plants were collected for pathogen identification. Many resting spores were observed when the root galls were examined under a light microscope. The resting spores were circular in shape, measuring 2.0 to 3.1 μm in diameter (average 2.6 μm). PCR amplification was conducted to confirm the pathogen. DNA was extracted from root galls and healthy roots (control) of SP. Two primers, TC2F (5′-AAACAACGAGTCAGCTTGAATGCTAGTGTG-3′) and TC2R (5′-CTTTAGTTGTGTTTCGGCTAGGATGGTTCG-3′) were used to detect P. brassicae (1). No PCR amplifications were observed with the control DNA as template. A fragment of the expected size (approximately 520 bp) was obtained when DNA was amplified from diseased roots of SP. These results suggest that the pathogen in the galled roots of SP is P. brassicae. Pathogenicity of P. brassicae in SP was tested on plants of both SP and Chinese cabbage (CC) (B. campestris ssp. pekinensis). A resting spore suspension prepared from naturally infected SP roots was mixed with a sterilized soil in two plastic pots, resulting in a final concentration of 5 × 106 spores/g soil. Soil treated with the same volume of sterile water was used as a control. Seeds of SP and CC were pre-germinated on moist filter paper for 2 days (20°C) and seeded into the infested and control pots, one seed per pot for planted for CC and four seeds per pot for SP. The pots were placed in a chamber at 15 to 25°C under 12 h light and 12 h dark. Plants in each pot were uprooted after 4 weeks and the roots of each plant were washed under tap water and rated for clubroot disease. No disease symptoms were observed in the control treatments of SP or CC. Plants of both species showed symptoms of clubroot, with the disease incidence of 62.5% and 100% on SP and CC, respectively. The pathogen was isolated from diseased roots of each plant and confirmed as P. brassicae based on morphological characteristics and PCR detection. To our knowledge, this is the first report of clubroot disease on C. bursa-pastoris in Sichuan Province of China. This finding suggests that it may be necessary to manage C. bursa-pastoris in cruciferous vegetable (cabbage, turnip) and oilseed rape production fields. References: (1) T. Cao et al. Plant Dis. 91:80, 2007. (2) W. G. Kim et al. Microbiology 39:233, 2011.

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First Report of Gummosis Disease of Japanese Apricot Caused by Botryosphaeria dothidea in Taiwan

Plant Disease ◽

10.1094/pdis-05-10-0384 ◽

2011 ◽

Vol 95 (1) ◽

pp. 77-77

Author(s):

Y. Ko ◽

C. W. Liu ◽

S. S. Chen ◽

K. Y. Chiu ◽

Y. W. Sun ◽

...

Keyword(s):

Direct Sequencing ◽

Morphological Characteristics ◽

Pcr Amplification ◽

Conidial Suspension ◽

Botryosphaeria Dothidea ◽

Cortical Cells ◽

Japanese Apricot ◽

First Report ◽

Representative Sequence ◽

Plastic Bags

Japanese apricot (Prunus mume Sieb. et Zucc.) is an economically important fruit crop grown on more than 10,000 ha in Taiwan. During May 2008, twigs of Japanese apricot trees in the commercial farms of Renai Region (Nantou County) showed symptoms of gummosis disease, with 12 to 18% of the trees affected. The disease was more severe on trees weakened by drought stress. Limb and twig infections began around lenticles as small, sunken, discolored lesions at the margins of wounds. Following infection, cortical cells collapsed, bark became depressed, and blisters developed, which were often cracked with whitish gummy exudation. Necrotic areas were seen on the cortical tissues. Leaves showed yellowing and drooping. In winter months, numerous black pycnidia or perithecia formed on infected twigs. Single conidial isolates of the pathogen were obtained from diseased twigs on acidified potato dextrose agar (PDA) incubated at 25 ± 1°C for 3 days. On the basis of morphological characteristics, the fungus was identified as Botryosphaeria dothidea (3). Conidia (17 to 22.6 × 4.3 to 6.0 μm) were hyaline, unicellular, and spindle shaped. Asci (78 to 125 × 15 to 17 μm) were hyaline, bitunicate, clavate, and eight spored. Ascospores (18 to 22 × 7.0 to 8.2 μm) were hyaline and spindle shaped or fusoid. The pathogen identity was further confirmed by PCR amplification and sequencing of ribosomal DNA internal transcribed spacer from the fungus with the primers ITS5: 5′-GGAAGTAAAAGTCGTAACAAGG-3′ and ITS4: 5′-TCCTCCGCTTATTGATATGC-3′ (4), and a representative sequence was deposited in NCBI GenBank (Accession No. GU594225). The sequence showed 99 to 100% homology with previously characterized strains of B. dothidea (GenBank Accession Nos. EU441944, DQ177876, and AY786320). Pathogenicity tests were conducted with inoculum prepared by culturing the fungus on PDA under a continuous photoperiod of 128 ± 25 μE·m–2·s–1 at 25°C for 3 days. Shallow cuts (3 × 3 × 3 mm) were made on 12- to 15-month-old healthy twigs with a scalpel and inoculated with either a 5-mm mycelial disc or 0.5 ml of conidial suspension (105 conidia/ml) of the fungus. Two twigs on each of six trees were inoculated. Inoculated areas were covered with moist, sterile cotton and the entire twigs were enclosed in plastic bags. Twigs were inoculated with 5-mm PDA discs or sterile water for controls. The symptoms described above were observed on all inoculated twigs 14 days after inoculation, whereas control twigs remained healthy. Reisolation from the inoculated twigs consistently yielded B. dothidea. In Taiwan, B. dothidea has been reported as the causal agent of gummosis of peach (1) and fruit ring rot of pear (2); however, to our knowledge, this is the first report of B. dothidea causing gummosis on Japanese apricot. References: (1) Y. Ko et al. Plant Pathol. Bull. 1:70, 1992. (2) Y. Ko et al. Plant Prot. Bull. (Taiwan) 35:211, 1993. (3) B. Slippers et al. Mycologia 96:83, 2004. (4) T. J. White et al. In: Amplification and Direct Sequencing of Fungal Ribosomal RNA Genes for Phylogenetics. Academic Press. San Diego, CA, 1990.

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First Report of Damping-Off on African Daisy Caused by Rhizoctonia solani AG-4 in Italy

Plant Disease ◽

10.1094/pdis-92-9-1367b ◽

2008 ◽

Vol 92 (9) ◽

pp. 1367-1367 ◽

Cited By ~ 2

Author(s):

D. Aiello ◽

I. Castello ◽

A. Vitale ◽

E. Lahoz ◽

R. Nicoletti ◽

...

Keyword(s):

Rhizoctonia Solani ◽

Morphological Characteristics ◽

Aerial Mycelium ◽

Ruthenium Red ◽

Fluorescent Light ◽

Damping Off ◽

First Report ◽

Perennial Plant ◽

Pectic Enzymes ◽

Electrophoretic Patterns

Osteospermum (African Daisy or Cape Daisy) is a genus belonging to the Calendulae with a large number of perennial plant species. In February of 2007, a severe damping-off occurred on 3- to 4-month-old potted cuttings of Osteospermum ‘Impassion Rose Purple’, ‘Impassion White’, ‘Impassion Purple’, and ‘Impassion White Rose’ cultivated in a nursery in eastern Sicily. More than 30% of the plants were infected. Disease symptoms consisted of extensive water-soaked lesions at the base of the stem followed by wilt and collapse of the plant. Isolations from diseased tissues on potato dextrose agar (PDA) amended with streptomycin sulfate at 100 mg/l consistently recovered a fungus with morphological characteristics of Rhizoctonia solani. Fungal colonies were initially white, turned brown after 2 to 3 days, and produced irregularly shaped, brown sclerotia after 1 week. Microscopic examination revealed that hyphae had right angle branching patterns, were constricted at the base of the branch near the union with main hyphae, and septate near the constriction. The number of nuclei per hyphal cell was determined on cultures grown at 25°C on 2% water agar in petri plates. Mycelium was stained with 0.5% aniline blue solution (4) and examined with a microscope at ×400. The hyphal cells were all multinucleate. Anastomosis groups were determined by pairing isolates (3) with tester isolates of AG-1 IA, AG-2-2-1, AG-2-2IIIB, AG-2-2IV, AG-3, AG-4, AG-5, AG-6, and AG-11. Anastomosis was observed only with tester isolates of AG-4, giving C2 reactions (1) at a high frequency. The identification of group AG-4 within R. solani had been obtained by electrophoretic patterns of pectic enzymes (polygalacturonases) in vertical pectin-acrylamide gel stained with ruthenium red (2). All isolates of R. solani collected from infected plants were paired in all combinations on PDA plus 1% activated charcoal and examined for somatic interaction. All paired colonies merged without producing visible tufts of aerial mycelium. Absence of tufts and the lack of formation of heterokaryon at the hyphal interaction zone indicated that all isolates belonged to the same mating type with the same mating alleles (3). Pathogenicity tests were performed by placing plugs of PDA from 5-day-old mycelial cultures in the soil near the base of the stem on 20 potted, healthy, 2-month-old cuttings of Osteospermum cv. Impassion Rose Purple. The same number of plants treated with 1/cm2 PDA plugs served as controls. Following inoculation, all plants were maintained in a growth chamber at 25°C and 95% relative humidity on a 12-h fluorescent light/dark regimen. Wilt symptoms and lesions at the base of stem identical to those observed in the nursery developed 7 days after inoculation, and all inoculated plants died within 20 days. Control plants remained symptomless. R. solani AG-4 was consistently reisolated from symptomatic tissues, completing Koch's postulates. To our knowledge, this is the first report of damping-off on the genus Osteospermum caused by R. solani. 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) M. C. Juliàn et al. Phytopathology 86:566, 1996. (4) C. C. Tu and J. W. Kimbrough. Mycologia 65:941, 1973.

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First Report of Beech Leaf Disease, Caused by Litylenchus crenatae mccannii, on American Beech (Fagus grandifolia) in Virginia

Plant Disease ◽

10.1094/pdis-08-21-1713-pdn ◽

2021 ◽

Author(s):

Mihail R. Kantor ◽

Zafar Ahmad Handoo ◽

Lynn Carta ◽

Shiguang Li

Keyword(s):

North America ◽

Rhode Island ◽

Morphological Characteristics ◽

Pcr Amplification ◽

Fagus Crenata ◽

Fagus Grandifolia ◽

American Beech ◽

First Report ◽

Leaf Disease ◽

Foliar Nematode

Beech leaf disease (BLD) was first reported in 2012 in Lake County, Ohio on American beech trees (Fagus grandifolia Ehrh.). Since then, it spread across the Northeastern United States and has been reported from Ohio, Pennsylvania, New York, New Jersey, Connecticut, Rhode Island, Maine, West Virginia, and Ontario, Canada (Carta et al. 2020; Mara and LaMondia 2020, Reid et al. 2020). The symptoms of BLD are characterized by dark interveinal banding of leaves appearing soon after spring flush that become chlorotic and necrotic through autumn, resulting in canopy thinning in advanced stages, followed in some young trees by death. Litylenchus crenatae mccannii has similar morphological characteristics with Litylenchus crenatae (Kanzaki et al. 2019) reported on Fagus crenata from Japan. However that beech species has not shown BLD symptoms or yielded any L. crenatae mccannii in North America. There are several morphological differences between the two. The North American subspecies have shorter post-uterine sac, narrower body width in mature females, shorter tail in immature females, longer tail in mature females, and longer stylet in males when compared to the Japanese subspecies (Carta et al. 2020). BLD symptoms were found on American beech trees in Prince William Forest Park, Prince William County, Virginia in June, 2021. The affected leaves contained females, males, and juveniles with morphometrics consistent with L. crenatae mccannii (Carta et al. 2020). The crude genomic DNA from a live single Litylenchus was prepared with freeze-thaw lysis (Carta and Li, 2019). The ITS PCR were performed by using the procedures and primer set, ITS-CL-F2 and 28S-CL-R described in the previous study (Carta and Li, 2020). The visualization, the cleanup and the direct DNA sequencing of the PCR products were performed by using the procedures described in the previous studies (Carta and Li, 2018 and 2019). Sequences were submitted to GenBank as accessions MZ611855 and MZ611856. This represents the first report of BLD in Virginia. It is also approximately 300 miles south of the 2020 detection of BLD from New Cumberland, WV, and represents the southernmost detection of the disease and nematode in North America. The author(s) declare no conflict of interest. References Carta, L.K., Li, S. 2018. Improved 18S small subunit rDNA primers for problematic nematode amplification. Journal of Nematology. 50, 533-542. Carta, L.K., Li, S. 2019. PCR amplification of a long rDNA segment with one primer pair in agriculturally important nematodes. Journal of Nematology. 51, e2019-26. Carta, L.K., Li, S. 2020. Improvement of long segment ribosomal PCR amplification for the molecular taxonomic identification of Litylenchus crenatae mccannii in beech trees with beech leaf disease. Journal of Nematology. 52, e2020-016. Kanzaki, N., Ichihara, Y., Aikawa, T., Ekino, T., Masuya, H. 2019. Litylenchus crenatae n. sp. (Tylenchomorpha: Anguinidae), a leaf gall nematode parasitising Fagus crenata Blume Nematology 21 (1), 5-22. http://www.brill.com/nematology doi: 10.1163/15685411-00003190 Marra, R.E., LaMondia, J. 2020. First report of beech leaf disease, caused by the foliar nematode, Litylenchus crenatae mccannii, on American beech (Fagus grandifolia) in Connecticut. Plant Disease (early view). https://doi.org/10.1094/PDIS-02-20-0442-PDN Reed, S. E., Greifenhagen, S., Yu, Q., Hoke A., Burke D. J., Carta L. K., Handoo Z.A., Kantor, M.R., Koch, J. 2020. Foliar nematode, Litylenchus crenatae ssp. mccannii, population dynamics in leaves and buds of beech leaf disease-affected trees in Canada and the US. Forest Pathology 50 (3), e12599.

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