First Report of Glomerella cingulata on Common Guava in Argentina

In Argentina, common guava (Psidium guajava L.) is frequently planted in gardens, but commercial production is limited. In February 2001, anthracnose symptoms were detected on fruits of common guava in La Plata, Buenos Aires Province. Symptoms of grayish, circular, sunken spots approximately 5 cm long were observed only on the surface of green unripe fruits. In humid conditions, acervuli containing salmon-pink masses of spores and dark setae were found within lesions. Symptomatic tissue was surface-disinfested, placed on potato dextrose agar, and incubated at 20°C. Cultures were obtained with abundant, gray, aerial mycelium and one-celled, hyaline, oblong, or cylindrical conidia with rounded ends (9.7 to 14.5 × 3.2 to 5.2 μm). Scarce dark brown perithecia developed in 2-month-old cultures but were not observed on fruit tissues. Asci were not conspicuous and contained straight or slightly curved ascospores (11.5 to 25.3 × 4 to 7 μm). The pathogen was identified as Glomerella cingulata (Stoneman) Spauld. & Schrenk (anamorph Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. in Penz), based on morphological characteristics (1,2). Ten healthy, immature, attached fruits of common guava were inoculated with 3 × 106 conidia per ml of each of six isolates of G. cingulata, and ten were left untreated. Individual fruits were enclosed in plastic bags and kept at 15 to 20°C. After 72 h, bags were removed, and after 20 days, anthracnose symptoms were observed only on inoculated fruits. G. cingulata was reisolated from fruit lesions, and Koch's postulates were fulfilled. To our knowledge, this is the first report of G. cingulata on common guava in Argentina. References: (1) B. C. Sutton. The Coelomycetes. CMI, Kew, England, 1980. (2) J. A. von Arx. Phytopathol. Z. 29:413, 1957.

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First Report of Anthracnose Caused by Glomerella cingulata on Passion Fruit in Argentina

Plant Disease ◽

10.1094/pdis.2000.84.6.706a ◽

2000 ◽

Vol 84 (6) ◽

pp. 706-706 ◽

Cited By ~ 4

Author(s):

S. Wolcan ◽

S. Larran

Keyword(s):

Disease Incidence ◽

Morphological Characteristics ◽

Aerial Mycelium ◽

Passion Fruit ◽

High Yield ◽

Conidial Suspension ◽

Glomerella Cingulata ◽

First Report ◽

Plastic Bags ◽

Subtropical Fruit

Passion fruit (Passiflora edulis Sims.) is a subtropical fruit recently cultivated in Misiones Province, Argentina. In spring 1997, a severe epidemic of anthracnose was observed. Disease incidence was ≍95%, causing high yield losses. Sunken, gray lesions on the whole surface of young fruits were observed. Under humid conditions, acervuli containing masses of spores and dark setae were found within lesions. On leaves, tendrils, and twigs, circular and irregular brown spots with darker edges were observed. Abortion of flowers also was recorded. Cultures on potato dextrose agar yielded abundant, gray aerial mycelium and one-celled, hyaline, oblong conidia with obtuse or rounded ends (11.2 to 15.0 × 3.8 to 4.6 μm). Perithecia were scarce (90.2 to 220.0 μm). Asci were not conspicuous, and ascospores measured 10.8 to 23.4 × 3.5 to 7.0 μm. Based on morphological characteristics, the fungus was identified as Glomerella cingulata (anamorph Colletotrichum gloeosporioides) (2). Fruits and leaves of P. edulis with and without wounds were sprayed with a conidial suspension (106/ml) and incubated in plastic bags for 48 h. Lesions similar to original symptoms were observed after 2 weeks only on wounded leaves and fruits. G. cingulata was reisolated, confirming Koch's postulates. This disease has been recorded in Brazil and Japan (1). This is the first report of G. cingulata on passion fruit in Argentina. Reference: (1) E. Francisco Neto et al. Summa Phytopathol. 21:25, 1995. (2) J. A. von Arx. Phytopathol. Z. 29:413, 1957.

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First Report of Ascochyta rabiei Causing Ascochyta Blight of Chickpea in Argentina

Plant Disease ◽

10.1094/pdis-02-12-0153-pdn ◽

2012 ◽

Vol 96 (9) ◽

pp. 1375-1375 ◽

Cited By ~ 3

Author(s):

G. Viotti ◽

M. A. Carmona ◽

M. Scandiani ◽

A. N. Formento ◽

A. Luque

Keyword(s):

Disease Incidence ◽

Ascochyta Blight ◽

Morphological Characteristics ◽

Pathogenic Fungi ◽

Ascochyta Rabiei ◽

Infected Leaf ◽

Buenos Aires Province ◽

Conidial Suspension ◽

First Report ◽

Plastic Bags

In November 2011, lesions similar to those reported for Ascochyta blight (1) were observed on Cicer arietinum L. (chickpea) plants growing in three commercial fields located at Río Primero and Río Segundo (Cordoba Province) and Lobería (Buenos Aires Province), Argentina. Disease incidence (percentage of plants affected) was 100% in all fields surveyed. Plants showed leaves, petioles, stems, and pods with brown lesions. Symptoms on leaves and pods were circular to oval (2 to 14 mm) while in the stems the lesions were elongated (2 to 30 mm). Seeds appeared small and shriveled with brown discoloration. Morphology of the fungi was examined on infected tissues. Numerous black pycnidia measuring 94.6 to 217.9 μm (145.9 ± 28.8 μm), arranged in concentric rings, were observed within of all the lesions. Conidia were predominantly aseptate, straight, hyaline with blunt ends, and measured 9.3 to 12.9 (11.3 ± 1.12) × 3.3 to 5.0 μm (4.2 ± 0.51). Morphological characteristics of the pathogen were similar to those described for Ascochyta rabiei (Pass.) Labrousse (teleomorph Didymella rabiei (Kovacheski) v. Arx (= Mycosphaerella rabiei Kovacheski)) (2). Fungus from infected leaf tissues was isolated on potato dextrose agar. Pathogenicity tests were conducted on seedlings of the susceptible cultivar by spraying leaves of each of 100 seedling plants with 10 ml of a conidial suspension (2 × 104 conidia/ml) of the isolated pathogen with a handheld atomizer. Plants were covered with plastic bags and placed in a growing chamber at 20 to 25°C for 3 days. The plastic bags were removed and the plants were maintained in high humidity at the same temperature. Noninoculated plants were used as controls. After 5 days, all inoculated plants showed typical symptoms. Foliar and stem lesions symptoms were similar to those originally observed in the field. Control plants remained healthy. Koch's postulates were fulfilled by isolating A. rabiei from inoculated plants. The colonies and the morphology of conidia were the same as those of the original isolates. To our knowledge, this is the first report of A. rabiei infecting chickpeas in Argentina. The outbreak of Ascochyta blight in Argentina is of concern because of its severity and the possibility that the pathogen was introduced on seed. This report underscores the need for further research on effective management programs for Ascochyta blight. References: (1) B. Bayaa and W. Chen. Compendium of Chickpea and Lentil Diseases and Pests The American Phytopathological Society, St. Paul, MN, 2011. (2) E. Punithalingam and P. Holliday. Page 337 in: CMI Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1972.

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First Report of Colletotrichum gloeosporioides on Chinese Rose in Argentina

Plant Disease ◽

10.1094/pdis.2000.84.12.1345b ◽

2000 ◽

Vol 84 (12) ◽

pp. 1345-1345 ◽

Cited By ~ 1

Author(s):

M. C. Rivera ◽

E. R. Wright ◽

S. Carballo

Keyword(s):

Colletotrichum Gloeosporioides ◽

Buenos Aires ◽

Morphological Characteristics ◽

Disease Prevalence ◽

Potato Dextrose Agar ◽

Conidial Suspension ◽

First Report ◽

Hibiscus Rosa Sinensis ◽

Leaf Drop ◽

Stems And Leaves

Chinese rose (Hibiscus rosa-sinensis L.) is a shrub frequently planted in Argentina. In November 1999, dieback and anthracnose symptoms were detected on stems and leaves of plants cv. Hawaii cultivated in Buenos Aires. Disease prevalence was 50%. Pieces of infected tissues were surface-sterilized for 1 min in 2% NaOCl, plated on potato-dextrose agar and incubated at 24 ± 2°C. The isolate that was consistently recovered from diseased tissues was identified as Colletotrichum gloeosporioides (Penz.) Penz. and Sacc., based on morphological characteristics (1,2). Teleomorph stage was not observed. Inoculation for pathogenicity testing was carried out by spraying a conidial suspension (6.5 × 106 conidia per ml) on plants with previously punctured leaves and pruned stems. Inoculated plants with unwounded tissues, as well as noninoculated controls, were included. Five replications of each treatment were done. Plants were incubated in moist chambers at 24°C. Whitish areas of 0.3 to 0.5 cm diameter surrounded by a purple halo developed on all punctured leaves within 10 days. Stem blight and leaf drop were observed. The center of the lesions was covered by black acervuli 14 days after inoculation. Unwounded and noninoculated controls remained symptomless. The pathogen was reisolated from inoculated leaves, completing Koch's postulates. This is the first report of C. gloeosporioides causing disease on Chinese rose in Argentina. References: (1) J. A. Bailey and M. J. Jeger, eds. 1992. Colletotrichum. CAB International, Surrey, England. (2) B. C. Sutton. 1980. The Coelomycetes. CMI, Kew.

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First Report of Fusarium Wilt on Eremophila spp. Caused by Fusarium oxysporum in Italy

Plant Disease ◽

10.1094/pdis-08-10-0597 ◽

2010 ◽

Vol 94 (12) ◽

pp. 1509-1509 ◽

Cited By ~ 1

Author(s):

G. Polizzi ◽

D. Aiello ◽

V. Guarnaccia ◽

A. Vitale ◽

G. Perrone ◽

...

Keyword(s):

Fusarium Oxysporum ◽

Morphological Characteristics ◽

Gene Sequences ◽

Single Spore ◽

First Report ◽

Potted Plants ◽

Plastic Bags ◽

Gene Coding ◽

Affected Plant ◽

Tubulin Protein

Eremophila spp. (Myoporaceae family), endemic to Australia, are evergreen shrubs or small trees occurring in arid, semi-arid, tropical, or temperate regions. In Europe, Eremophila spp. are grown for their horticultural appeal. During 2009 and 2010, extensive wilting was observed on 2-month to 1-year-old potted plants of Eremophila laanii F. Muell., E. glabra subsp. carnosa Chinnock, and E. maculata (Ker Gawl.) F. Muell. grown in a commercial nursery near Catania (southern Italy). Internally, symptomatic plants had conspicuous vascular discoloration from the crown to the canopy. Diseased crown and stem tissues were surface disinfested for 30 s in 1% NaOCl, rinsed in sterile water, plated on potato dextrose agar (PDA) amended with 100 mg/liter of streptomycin sulfate, and incubated at 25°C. A Fusarium sp. was consistently isolated from affected plant tissues. Colonies with purple mycelia and violet reverse colors developed after 9 days. On carnation leaf agar, single-spore isolates produced microconidia on short monophialides, macroconidia that were three to five septate with a pedicellate base, and solitary and double-celled or aggregated chlamydospores. A PCR assay was conducted on two representative isolates (ITEM 12591 and ITEM 12592) by analyzing sequences of the partial CaM gene (coding calmodulin protein) and benA (coding beta-tubulin protein) using the primers as reported by O'Donnell et al. (1). Calmodulin sequences of ITEM 12951 and ITEM 12952 isolates (GenBank Nos. FR671157 and FR671158) exhibited 99.8 and 99.5% identity with Fusarium oxysporum strain ITEM 2367 (GenBank No. AJ560774), respectively, and had 99.5% homology between them. BenA gene sequences of ITEM 12951 (GenBank No. FR671426) exhibited an identity of 100% to F. oxysporum f. sp. vasinfectum strain CC-612-3 (GenBank No. AY714092.1), and benA gene sequences of ITEM 12952 (GenBank No. FR671427) exhibited an identity of 100% to F. oxysporum f. sp. vasinfectum strain LA 140 (GenBank No. FJ466740.1), whereas the homology between the two strains is 99.5%. Morphological characteristics, as well as CaM and benA sequences, identified the isolates as F. oxysporum Schlechtend:Fr. Pathogenicity tests were performed by placing 1-cm2 plugs of PDA from 9-day-old mycelial cultures near the crown on potted, healthy, 3-month-old cuttings of E. laanii, E. glabra subsp. carnosa, and E. maculata. Twenty plants for each species were inoculated with each isolate. The same number of plants served as noninoculated controls. All plants were enclosed for 4 days in plastic bags and placed in a growth chamber at 24 ± 1°C. Plants were then moved to a greenhouse where temperatures ranged from 23 to 27°C. Symptoms identical to those observed in the nursery developed 20 days after inoculation with both strains. Crown and stem discoloration was detected in all inoculated plants after 45 days. Wilting was detected on 15% of plants. Control plants remained symptomless. F. oxysporum was consistently reisolated from symptomatic tissues and identified as previously above. To our knowledge, this is the first report of F. oxysporum causing disease of Eremophila spp. worldwide. Reference: (1) K. O'Donnell et al. Mycoscience 41:61, 2000.

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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 Colletotrichum truncatum on Alfalfa in Turkey

Plant Disease ◽

10.1094/pdis.2000.84.1.100a ◽

2000 ◽

Vol 84 (1) ◽

pp. 100-100 ◽

Cited By ~ 2

Author(s):

C. Eken ◽

E. Demirci

Keyword(s):

Morphological Characteristics ◽

Conidial Suspension ◽

Colletotrichum Truncatum ◽

First Report ◽

Clear Area ◽

Granular Cytoplasm ◽

Symptomatic Tissue ◽

Medicago Sativa L ◽

Stem Lesions ◽

And Control

During the summer of 1997 and 1998, a pathogen identified as Colletotrichum truncatum (Schwein.) Andrus & W.D. Moore was isolated from lesions on stems of alfalfa (Medicago sativa L.) plants in Erzurum, Turkey. Typical symptoms on stems of mature plants were large, sunken, irregularly shaped black lesions. Twenty-eight cultures of C. truncatum were isolated from stem lesions. Acervuli containing spores and dark setae were observed within lesions. Conidia were hyaline, one-celled, falcate to nearly straight with a prominent clear area in the center of highly granular cytoplasm, and measured 16.3 to 20.6 × 3.1 to 4.5 μm. These morphological characteristics were consistent with the description of C. truncatum (1). The pathogenicity of two isolates was determined on alfalfa cv. Bilensoy. Alfalfa seedlings (6-week-old) were inoculated with a conidial suspension of the fungus (1.4 × 107 conidia per ml), incubated in a moist chamber for 3 days, and subsequently transferred to growth chambers maintained at 25°C with a 12-h photoperiod. Ten plants were inoculated with each isolate. Symptoms first appeared on stems 12 days after inoculation. Sunken, irregularly shaped black lesions occasionally girdled stems of plants inoculated with C. truncatum. Symptoms did not appear on stems of control plants inoculated with sterile distilled water. C. truncatum was reisolated from symptomatic tissue. This is the first report of C. truncatum on alfalfa from Turkey. Reference: (1) B. C. Sutton. 1992. Pages 1–27 in: Colletotrichum Biology, Pathology and Control. J. A. Bailey and M. J. Jeger, eds. CAB International, Wallingford, U.K.

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First Report of Leaf Spot Disease Caused by Colletotrichum gloeosporioides on Chinese Bean Tree in China

Plant Disease ◽

10.1094/pdis-03-12-0261-pdn ◽

2013 ◽

Vol 97 (1) ◽

pp. 138-138 ◽

Cited By ~ 1

Author(s):

B. Z. Fu ◽

M. Yang ◽

G. Y. Li ◽

J. R. Wu ◽

J. Z. Zhang ◽

...

Keyword(s):

Leaf Spot ◽

Colletotrichum Gloeosporioides ◽

Disease Incidence ◽

Phylogenetic Analyses ◽

Morphological Characteristics ◽

Leaf Spot Disease ◽

First Report ◽

Spot Disease ◽

Rdna Its ◽

Its Sequence Analysis

Chinese bean tree, Catalpa fargesii f. duciouxii (Dode) Gilmour, is an ornamental arbor plant. Its roots, leaves, and flowers have long been used for medicinal purposes in China. During July 2010, severe outbreaks of leaf spot disease on this plant occurred in Kunming, Yunnan Province. The disease incidence was greater than 90%. The symptoms on leaves began as dark brown lesions surrounded by chlorotic halos, and later became larger, round or irregular spots with gray to off-white centers surrounded by dark brown margins. Leaf tissues (3 × 3 mm), cut from the margins of lesions, were surface disinfected in 0.1% HgCl2 solution for 3 min, rinsed three times in sterile water, plated on potato dextrose agar (PDA), and incubated at 28°C. The same fungus was consistently isolated from the diseased leaves. Colonies of white-to-dark gray mycelia formed on PDA, and were slightly brown on the underside of the colony. The hyphae were achromatic, branching, septate, and 4.59 (±1.38) μm in diameter on average. Perithecia were brown to black, globose in shape, and 275.9 to 379.3 × 245.3 to 344.8 μm. Asci that formed after 3 to 4 weeks in culture were eight-spored, clavate to cylindrical. The ascospores were fusiform, slightly curved, unicellular and hyaline, and 13.05 to 24.03 × 10.68 to 16.02 μm. PCR amplification was carried out by utilizing universal rDNA-ITS primer pair ITS4/ITS5 (2). Sequencing of the PCR products of DQ1 (GenBank Accession No. JN165746) revealed 99% similarity (100% coverage) with Colletotrichum gloeosporioides isolates (GenBank Accession No. FJ456938.1, No. EU326190.1, No. DQ682572.1, and No. AY423474.1). Phylogenetic analyses (MEGA 4.1) using the neighbor-joining (NJ) algorithm placed the isolate in a well-supported cluster (>90% bootstrap value based on 1,000 replicates) with other C. gloeosporioides isolates. The pathogen was identified as C. gloeosporioides (Penz.) Penz. & Sacc. (teleomorph Glomerella cingulata (Stoneman) Spauld & H. Schrenk) based on the morphological characteristics and rDNA-ITS sequence analysis (1). To confirm pathogenicity, Koch's postulates were performed on detached leaves of C. fargesii f. duciouxii, inoculated with a solution of 1.0 × 106 conidia per ml. Symptoms similar to the original ones started to appear after 10 days, while untreated leaves remained healthy. The inoculation assay used three leaves for untreated and six leaves for treated. The experiments were repeated once. C. gloeosporioides was consistently reisolated from the diseased tissue. C. gloeosporioides is distributed worldwide causing anthracnose on a wide variety of plants (3). To the best of our knowledge, this is the first report of C. gloeosporioides causing leaf spots on C. fargesii f. duciouxii in China. References: (1) B. C. Sutton. Page 1 in: Colletotrichum: Biology, Pathology and Control. CAB International. Wallingford, UK, 1992. (2) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990. (3) J. Yan et al. Plant Dis. 95:880, 2011.

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First Report of Powdery Mildew Caused by Erysiphe diffusa, Oidium neolycopersici, and Podosphaera xanthii on Papaya in Taiwan

Plant Disease ◽

10.1094/pdis-05-11-0362 ◽

2011 ◽

Vol 95 (9) ◽

pp. 1188-1188 ◽

Cited By ~ 6

Author(s):

J.-G. Tsay ◽

R.-S. Chen ◽

H.-L. Wang ◽

W.-L. Wang ◽

B.-C. Weng

Keyword(s):

Powdery Mildew ◽

Morphological Characteristics ◽

Its Region ◽

Podosphaera Xanthii ◽

Oidium Neolycopersici ◽

First Report ◽

Plastic Bags ◽

The World ◽

Golovinomyces Cichoracearum ◽

Powdery Mildew Fungi

Powdery mildew can be found in most papaya (Carica papaya L.) fields during the winter and spring seasons in Taiwan. It usually causes severe yellowing of the leaf lamina and petiole and serious defoliation. Three types of powdery mildew fungi were isolated from papaya leaves in Chiayi City (23.28°N, 120.28°E) at the beginning of 2008. Conidia of the first one were single, globose, hyaline, and 24 to 36 × 14 to 18 μm (average 30.2 × 15.6 μm) without fibrosin bodies and with straight or occasionally flexuous conidiophores at the base. The second one had short pseudo-chains of two to four conidia which were ellipsoidal to ovoid, hyaline, and 24 to 40 × 12 to 16 μm (average 29.7 × 13.4 μm) without fibrosin bodies. The third type had chains of ellipsoidal conidia that were hyaline, 24 to 28 × 12 to 16 μm (average 26.3 × 14.4 μm) and contained fibrosin bodies. To confirm the identity of the three fungi, the internal transcribed spacer (ITS) region of rDNA was amplified using the primer pairs G1 (5′-TCC GTA GGT GAA CCT GCG GAA GGA T-3′)/Ed2 (5′-CGC GTA GAG CCC ACG TCG GA-3′), G1 (5′-TCC GTA GGT GAA CCT GCG GAA GGA T-3′)/On2 (5′-TGT GAT CCA TGT GAC TGG AA-3′), and S1 (5′-GGA TCA TTA CTG AGC GCG AGG CCC CG-3′)/S2 (5′-CGC CGC CCT GGC GCG AGA TAC A-3′). The alignment of obtained sequences (GenBank Accession Nos. GU358452, 507 bp; GU358451, 580 bp; and GU358450, 455 bp) showed a sequence identity of 100, 99, and 99% with the ITS sequences of Erysiphe diffusa, Oidium neolycopersici, and Podosphaera xanthii (GenBank Accession Nos. FJ378880, EU909694, and GQ927254), respectively. On the basis of morphological characteristics and ITS sequence similarities, these fungi were identified as E. diffusa (Cooke & Peck) U. Braun & S. Takam., O. neolycopersici L. Kiss, and P. xanthii (Castagne) U. Braun & S. Takam., respectively (1,3). Single colonies on papaya leaves infected with powdery mildew were identified in the laboratory and maintained on papaya leaves as inoculum. Pathogenicity was confirmed through inoculations by gently pressing a single colony of each fungus onto leaves of healthy papaya seedlings (cv. Horng-Fe). Five seedlings were inoculated for each fungus and then covered with plastic bags for 2 days. Five noninoculated seedlings served as control. After inoculation, treated plants were maintained separately from the control in different rooms of a greenhouse at 25°C under natural daylight conditions. Seven days after inoculation, typical symptoms of powdery mildew were observed on inoculated plants, but not on noninoculated plants. The same species from diseased lesions following artificial inoculation with each fungus were identified with light microscopy. Papaya was previously described as a host to O. caricae Noack in many tropical and subtropical areas of the world including Taiwan (2). However E. cruciferarum, Golovinomyces cichoracearum, Oidiopsis sicula, O. caricae, O. caricae-papayae, O. caricicola, O. indicum, O. papayae, Ovulariopsis papayae, P. caricae-papayae, P. macularis, P. xanthii, and Streptopodium caricae were reported to infect papaya (4). To our knowledge, this is the first report of papaya powdery mildew caused by E. diffusa and O. neolycopersici in the world and the first report of the three fungi found on papaya in Taiwan. References: (1) U. Braun and S. Takamatsu. Schlechtendalia 4:1, 2000. (2) H. S. Chien and H. L. Wang. J. Agric. Res. China 33:320, 1984. (3) L. Kiss et al. Mycol. Res. 105:684, 2001. (4) J. R. Liberato et al. Mycol. Res. 108:1185, 2004.

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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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