First Report of Papaya Fruit Anthracnose Caused by Colletotrichum brevisporum in Brazil

Papaya fruits (Carica papaya L.) (cv. Golden) showing post-harvest anthracnose symptoms were observed during surveys of papaya disease in northeastern Brazil from 2008 to 2012. Fruits affected by anthracnose showed sunken, prominent, dark brown to black lesions. Small pieces (4 to 5 mm) of necrotic tissue were surface sterilized for 1 min in 1.5% NaOCl, washed twice with sterile distilled water, and plated onto potato dextrose agar (PDA) amended with 0.5 g liter–1 streptomycin sulfate. Macroscopic colony characters and microscopic morphology characteristics of four isolates were observed after growth on PDA (2) for 7 days at 25°C under a 12-hr light/dark cycle. Colonies varied between colorless and pale brown in reverse, with orange conidial mass. Conidia were hyaline, aseptate, cylindrical with round ends, slightly flattened, smooth-walled, guttulate, and 13.5 (10.5 to 17.1) μm × 3.8 (2.1 to 4.8) μm (l/w ratio = 3.5, n = 50), typical of Colletotrichum spp. DNA sequencing of partial sequences of actin (ACT) gene and the internal transcribed spacer (ITS1-5.8S-ITS2 rRNA) were conducted to accurately identify the species. Sequences of the papaya isolates were 99% similar to those of Colletotrichum brevisporum (GenBank Accession Nos. JN050216, JN050217, JN050238, and JN050239). A phylogenetic analysis using Bayesian inference and including published ACT and ITS data for C. brevisporum and other Colletotrichum species was carried out (1). Based on morphological and molecular data, the papaya isolates were identified as C. brevisporum. Conidia of the papaya isolates were narrower than those described for C. brevisporum (2.9 to 4.8 μm and 5 to 6 μm, respectively) (1), which may be due to differences in incubation temperature or a typical variation in conidial size in Colletotrichum species (3). Sequences of the isolates obtained in this study are deposited in GenBank (ACT Accession Nos. KC702903, KC702904, KC702905, and KC702906; ITS Accession Nos. HM163181, HM015851, HM015854, and HM015859). Cultures are deposited in the Culture Collection of Phytopathogenic Fungi of the Universidade Federal Rural de Pernambuco, Recife, Brazil (CMM 1672, CMM 1702, CMM 1822, and CMM 2005). Pathogenicity testing was conducted with all four strains of C. brevisporum on papaya fruits (cv. Golden). Fruits were wounded at the medium region by pushing the tip of four sterile pins through the surface of the skin to a depth of 3 mm. Mycelial plugs taken from the margin of actively growing colonies (PDA) of each isolate were placed in shallow wounds. PDA discs without fungal growth were used as control. Inoculated fruits were maintained in a humid chamber for 2 days at 25°C in the dark. After 6 days, anthracnose symptoms developed that were typical of diseased fruit in the field. C. brevisporum was successfully reisolated from symptomatic fruits to fulfill Koch's postulates. C. brevisporum was described from Neoregalia sp. and Pandanus pygmaeus in Thailand (1). To our knowledge, this is the first report of C. brevisporum in Brazil and the first report of this species causing papaya fruit anthracnose. References: (1) P. Noireung et al. Cryptogamie Mycol., 33:347, 2012. (2) B. C. Sutton. The Genus Glomerella and its anamorph Colletotrichum. CAB International, Wallingford, UK, 1992. (3) B. S. Weir et al. Stud. Mycol. 73:115, 2012.

Download Full-text

First Report of Anthracnose Caused by Colletotrichum spaethianum on Hemerocallis flava in Brazil

Plant Disease ◽

10.1094/pdis-10-13-1026-pdn ◽

2014 ◽

Vol 98 (7) ◽

pp. 997-997 ◽

Cited By ~ 4

Author(s):

W. A. S. Vieira ◽

S. J. Michereff ◽

A. C. Oliveira ◽

A. Santos ◽

M. P. S. Câmara

Keyword(s):

Culture Media ◽

Fungal Growth ◽

Phytopathogenic Fungi ◽

Culture Collection ◽

Northeastern Brazil ◽

Width Ratio ◽

Rrna Gene ◽

First Report ◽

Detached Leaves ◽

Microscopic Morphology

In January 2011, leaves of several daylily (Hemerocallis flava L.) plants in nurseries in Vitória da Conquista, northeastern Brazil, showed typical anthracnose symptoms. Reddish brown lesions with a yellow halo were first observed at the tip leaves. As the disease progressed, the lesions rapidly expanded down the leaves, resulting in severe blight. Small pieces up to 5 mm in diameter were removed from the lesion margins, surface sterilized for 1 min in 1.5% NaOCl, washed twice with sterile distilled water, and plated onto potato dextrose agar (PDA) amended with 0.5 g liter−1 streptomycin sulfate. Macroscopic colony characters and microscopic morphology characteristics of two isolates were developed after growth on PDA for 7 days at 25°C under a 12-h light/dark cycle. Colonies presented effuse mycelium, initially white and becoming pale gray, with numerous black structures like sclerotia, setae, and acervuli absent in culture media. Conidia were hyaline, aseptate, curved or slightly curved, round or somewhat acute apex, base truncate, 13.4 to 22.7 (18.2 ± 2.16) μm length, and 3.2 to 5.8 (4.24 ± 0.62) μm width, length/width ratio 4.37, and were typical of Colletotrichum spp. DNA sequencing of partial sequence of actin (ACT), chitin synthase (CHS-1), and glyceraldehyde-3-phosphate dehydrogenase (GPD) genes and the internal transcribed spacer (ITS1-5.8S-ITS2 rRNA gene cluster) were conducted to accurately identify the species. Sequences of two daylily isolates were highly similar to those of C. spaethianum (Allesch.) Damm, P.F. Cannon & Crous. A phylogenetic analysis using Bayesian inference and including published ACT, CHS-1, GPDH, and ITS data for C. spaethianum and other Colletotrichum species associated with daylily anthracnose (1,3) showed that the isolated fungi belong to the C. spaethianum clade. Sequences of the isolates obtained in this study were deposited in GenBank (ACT Accession Nos. KC598114 and KC598115; CHS-1 Accession Nos. KC598116 and KC598117; GPDH Accession Nos. KC598118 and KC598119; ITS Accession Nos. KC598120 and KC598121). Cultures are deposited in the Culture Collection of Phytopathogenic Fungi of the Universidade Federal Rural de Pernambuco, Recife, Brazil (CMM1224 and CMM1225). Pathogenicity tests were conducted with the two C. spaethianum strains on daylily leaves. Mycelial plugs taken from the margin of actively growing colonies (PDA) of each isolate were applied in shallow wounds near the tip leaves. Four detached leaves were inoculated for each isolate, and PDA discs without fungal growth were used as controls. The leaves were maintained in humid chamber for 2 days at 25°C under a 12-h photoperiod. Anthracnose symptoms that closely resembled those observed in the affected nurseries were developed up to 5 days after inoculation. No symptoms developed on the control plants. C. spaethianum was successfully re-isolated from symptomatic plants to fulfill Koch's postulates. C. spaethianum was described from H. fulva and H. citrina in China, Hosta sielbodiana in Germany, and Lilium sp. in South Korea (3), and from Peucedanum praeruptorum in China (2). To our knowledge, this is the first report of C. spaethianum in Brazil and the first report on H. flava. References: (1) U. Damm et al. Fungal Divers. 39:45, 2009. (2) M. Guo et al. Plant Dis. 97:1380, 2013. (3) Y. Yang et al. Trop. Plant Pathol. 37:165, 2012.

Download Full-text

First Report of Colletotrichum siamense Causing Anthracnose of Guava (Psidium guajava) in Mexico

Plant Disease ◽

10.1094/pdis-03-21-0530-pdn ◽

2021 ◽

Author(s):

Edgar Edel Rodríguez-Palafox ◽

Alfonso Vásquez-López ◽

Guillermo Márquez-Licona ◽

Nelson Bernardi Lima ◽

Erika Lagunes-Fortiz ◽

...

Keyword(s):

Phylogenetic Analysis ◽

Species Complex ◽

Aerial Mycelium ◽

Its Region ◽

Psidium Guajava ◽

Culture Collection ◽

First Report ◽

Colletotrichum Species ◽

Guava Fruit ◽

Colletotrichum Siamense

Guava (Psidium guajava L.) is a small tree belonging to the Myrtaceae family and it is distributed worldwide in the tropical and subtropical areas. During the summer of 2019, symptoms of fruit anthracnose were observed on approx. 90% of 250 guava trees located in backyards in Juan Jose Rios, Sinaloa, Mexico. Lesions on guava fruit were irregular, necrotic, and sunken. On advanced infections, acervuli containing salmon-pink masses of spores were observed on the lesions. Twenty fruits were collected from 10 trees (2 fruits per tree). Colletotrichum-like colonies were consistently isolated on PDA medium and 20 monoconidial isolates were obtained. Four isolates were selected as representatives for morphological characterization, multilocus phylogenetic analysis, and pathogenicity tests. The isolates were deposited in the Culture Collection of Phytopathogenic Fungi of the Faculty of Agriculture of El Fuerte Valley at the Sinaloa Autonomous University (Accession nos. FAVF205–FAVF208). Colonies on PDA medium were flat with an entire margin, with abundant felty and white aerial mycelium, with pink conidial masses. Conidia (n= 100) were cylindrical, hyaline, aseptate, with ends rounded, and measuring 14.8 to 18.1 × 4.4 to 5.3 μm. Based on morphological features, the isolates were tentatively allocated in the C. gloeosporioides species complex (Weir et al. 2012). For molecular identification, genomic DNA was extracted, and the internal transcribed spacer (ITS) region (White et al. 1990), as well as partial sequences of actin (ACT), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), β-tubulin (TUB2), chitin synthase (CHS-1) and glutamine synthetase (GS) genes were amplified by PCR (Weir et al. 2012), and sequenced. A phylogenetic tree based on Bayesian inference and including published ITS, GAPDH, TUB2, ACT, CHS-1, and GS data for Colletotrichum species was constructed. The multilocus phylogenetic analysis clearly distinguished the four isolates FAVF205–FAVF208 as C. siamense separating it from all other species within the C. gloeosporioides species complex. The sequences were deposited in GenBank (accessions nos. ITS: MW598512–MW598515; GAPDH: MW595216–MW595219; TUB2: MW618012–MW618015; ACT: MW595208–MW595211; CHS-1: MW595212–MW595215; and GS: MW618008–MW618011). Pathogenicity of the four isolates was verified on 40 healthy guava fruits. Twenty fruits were wounded with a sterile toothpick (2 mm in depth) and a mycelial plug (6 mm of diameter) was placed on each wound. Ten fruits inoculated with a PDA plug without mycelial growth served as controls. The fruit was kept in a moist plastic chamber at 25°C for 7 days. Pathogenicity of each isolate was tested with both non-wound and wound inoculation methods. The experiments were repeated twice with similar results. All inoculated fruits developed sunken necrotic lesions 4 days after inoculation, whereas no symptoms were observed on the control fruits. The fungi were consistently re-isolated only from the diseased fruits, fulfilling Koch´s postulates. Colletotrichum siamense has been previously reported on guava fruit in India (Sharma et al. 2015). However, to our best knowledge, this is the first report of C. siamense causing fruit anthracnose on guava in Mexico. Therefore, it is necessary to explore the diversity of Colletotrichum species on guava in detail through subsequent phylogenetic studies as well as to monitor the distribution of this pathogen into other Mexican regions.

Download Full-text

First Report of Leaf Spot Caused by Phoma dictamnicola on Dictamnus dasycarpus in Korea

Plant Disease ◽

10.1094/pdis-06-14-0658-pdn ◽

2014 ◽

Vol 98 (10) ◽

pp. 1443-1443

Author(s):

J. H. Park ◽

S. E. Cho ◽

C. K. Lee ◽

S. H. Lee ◽

H. D. Shin

Keyword(s):

Leaf Spot ◽

Its Region ◽

Molecular Data ◽

Culture Collection ◽

Morphological Identification ◽

Conidial Suspension ◽

Aesthetic Value ◽

Transparent Plastic ◽

First Report ◽

Plastic Bags

Dictamnus dasycarpus Turcz, known as densefruit pittany, is a perennial herbal plant belonging to the Rutaceae. In Oriental medicine, this plant is used for treatment of various ailments (4). Since the white and purple striped flowers and glossy leaves are of aesthetic value, the plant is popular in gardens throughout Korea. In July 2012, a leaf spot was observed on hundreds of D. dasycarpus with nearly 100% incidence in a garden in Gapyeong County, Korea. Lesions on leaves reaching up to 20 mm in diameter were circular to irregular, brown to dark brown, then becoming zonate with age, and finally fading to grayish brown in the center with a reddish brown margin. The disease caused premature defoliation and reduced plant vigor as well as aesthetic value. In June 2014, the same symptoms were found on D. dasycarpus in a nursery in Jinju City, Korea. Representative samples were deposited in the Korea University Herbarium (KUS). Pycnidia on lesions were epiphyllous, immersed or semi-immersed in host tissue, light brown to olive brown, and 90 to 210 μm in diameter. Ostioles were 15 to 30 μm wide and surrounded by a ring of darker cells. Conidia were hyaline, smooth, ellipsoidal to nearly reniform, straight to mildly curved, aseptate or rarely medianly 1-septate with age, 5.5 to 9.6 × 1.8 to 3.6 μm, and contained small oil drops. These characteristics were consistent with the previous descriptions of Phoma dictamnicola Boerema, Gruyter & Noordel. (1,2). A monoconidial isolate was cultured on potato dextrose agar plates and deposited in the Korea Agricultural Culture Collection (Accession No. KACC46948). Morphological identification of the fungus was confirmed by molecular data. Genomic DNA was extracted using a DNeasy Plant Mini Kit (Qiagen Inc., Valencia, CA). The internal transcribed spacer (ITS) region of rDNA was amplified using the ITS1/ITS4 primers and sequenced. The resulting sequence of 505 bp was deposited in GenBank (Accession No. KM047023). A BLAST search showed that the ITS sequence shared >99% similarity with that of P. dictamnicola (GU237877). For the pathogenicity tests, inoculum was prepared by harvesting conidia from 30-day-old cultures of KACC46948 and a conidial suspension (2 × 106 conidia/ml) was sprayed onto leaves of five healthy seedlings. Five seedlings were sprayed with sterile distilled water, serving as controls. The plants were covered with transparent plastic bags for 48 h in a 25°C glasshouse with a 12-h photoperiod. After 10 days, typical leaf spot symptoms started to develop on the leaves of the inoculated plants. The fungus, P. dictamnicola, was re-isolated from those lesions, confirming Koch's postulates. No symptoms were observed on control plants. Previously, Phoma leaf spot on Dictamnus spp. has been reported in the Netherlands and North America (3) and recently in China (1). To our knowledge, this is the first report of leaf spot on D. dasycarpus caused by P. dictamnicola in Korea. Our observations suggest that low humidity with good ventilation as well as removal of infected leaves and plant debris might be main strategies for preventing this disease. References: (1) Q. Bai et al. Plant Dis. 95:771, 2011. (2) G. H. Boerema et al. Phoma Identification Manual: Differentiation of Specific and Infra-Specific Taxa in Culture. CABI Publishing. Wallingford, UK, 2004. (3) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab., Online publication, USDA ARS, Retrieved June 19, 2014. (4) J. L. Yang et al. Planta Med. 77:271, 2011.

Download Full-text

First Report of Colletotrichum karstii Causing Anthracnose on Blueberry Leaves in Brazil

Plant Disease ◽

10.1094/pdis-07-14-0717-pdn ◽

2015 ◽

Vol 99 (1) ◽

pp. 157-157 ◽

Cited By ~ 5

Author(s):

J. A. Rios ◽

D. B. Pinho ◽

W. R. Moreira ◽

O. L. Pereira ◽

F. A. Rodrigues

Keyword(s):

Molecular Characterization ◽

Control Strategies ◽

Mangifera Indica ◽

Molecular Data ◽

Culture Collection ◽

Control Treatment ◽

First Report ◽

Plastic Bags ◽

Morphological And Molecular Data ◽

Southern Highbush

Anthracnose or ripe rot of blueberry (Vaccinium spp.) is caused predominantly by Colletotrichum fioriniae, which belongs to the C. acutatum complex since it has cylindrical conidia with both ends acute (2). In May 2013, an isolate typical of the C. boninense complex (cylindrical conidia with both ends rounded) (1) was obtained from leaves of southern highbush blueberry seedlings in a nursery located in the municipality of Pelotas, Rio Grande do Sul, Brazil. The symptoms initially appear as circular, necrotic lesions 10 to 30 mm in diameter. At high humidity, lesions expand rapidly to cover the entire foliar surface, leading to severe defoliation of the seedlings. This disease occurred in 100% of the seedlings, causing serious losses in the nursery. A single-conidium culture was obtained on potato-dextrose-agar (PDA) medium followed by morphological and molecular characterization. This culture was deposited at the culture collection of the Universidade Federal de Viçosa, Brazil (Accession No. COAD 1741). Conidia were cylindrical, aseptate, hyaline, rounded at both ends, and 11 to 16 μm (μ = 13) long and 5 to 6 μm (μ = 5.5) wide (n = 100). For the molecular characterization, sequences of the internal transcribed spacer (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and β-tubulin 2 (βt) regions were obtained and deposited in GenBank (KM055653 to KM055655). A search of the Q-bank Fungi database using the ITS, βt, and GAPDH sequences retrieved C. karstii with 100, 99, and 100% identities, respectively. Based on morphological and molecular data, the fungus was identified as C. karstii. To verify pathogenicity, 20 leaves from the upper branches of 1-m tall blueberry seedlings were inoculated with 6-mm-diameter plugs from a 7-day-old culture. PDA plugs were placed on the leaves of seedlings to serve as the control. Initially, seedlings were maintained at 25 ± 2°C in the dark. Thereafter, seedlings were covered with plastic bags and transferred to a greenhouse. Anthracnose symptoms on the leaves were observed at 5 days after inoculation. Seedlings from the control treatment remained symptomless. The fungus was re-isolated from the necrotic lesions, confirming Koch's postulates. C. karstii has a wide host range and in Brazil has been previously reported on Bombax aquaticum, Carica papaya, Eugenia uniflora, Malus domestica, and Mangifera indica (1,3,4). To the best of our knowledge, this is the first report of C. karstii causing anthracnose on the leaves of blueberry seedlings in Brazil or worldwide. Due to the high disease severity and intense defoliation of blueberry seedlings, this pathogen represents a new threat for nurseries. Therefore, control strategies should be investigated for this disease. References: (1) U. Damm et al. Stud. Mycol. 73:1, 2012. (2) U. Damm et al. Stud. Mycol. 73:37, 2012. (3) Lima et al. Plant Dis. 97:1248, 2014. (4) Velho et al. Plant Dis. 98:157, 2014.

Download Full-text

Double Gamers—Can Modified Natural Regulators of Higher Plants Act as Antagonists against Phytopathogens? The Case of Jasmonic Acid Derivatives

International Journal of Molecular Sciences ◽

10.3390/ijms21228681 ◽

2020 ◽

Vol 21 (22) ◽

pp. 8681

Author(s):

Nicolò Orsoni ◽

Francesca Degola ◽

Luca Nerva ◽

Franco Bisceglie ◽

Giorgio Spadola ◽

...

Keyword(s):

Jasmonic Acid ◽

Plant Pathogens ◽

Higher Plants ◽

Fungal Growth ◽

Pathogenic Fungi ◽

Inhibitory Effect ◽

Fungal Species ◽

Phytopathogenic Fungi ◽

Phaeomoniella Chlamydospora ◽

Horticultural Crops

As key players in biotic stress response of plants, jasmonic acid (JA) and its derivatives cover a specific and prominent role in pathogens-mediated signaling and hence are promising candidates for a sustainable management of phytopathogenic fungi. Recently, JA directed antimicrobial effects on plant pathogens has been suggested, supporting the theory of oxylipins as double gamers in plant-pathogen interaction. Based on these premises, six derivatives (dihydrojasmone and cis-jasmone, two thiosemicarbazonic derivatives and their corresponding complexes with copper) have been evaluated against 13 fungal species affecting various economically important herbaceous and woody crops, such as cereals, grapes and horticultural crops: Phaeoacremonium minimum, Neofusicoccum parvum, Phaeomoniella chlamydospora, Fomitiporia mediterranea, Fusarium poae, F. culmorum, F. graminearum, F. oxysporum f. sp. lactucae,F. sporotrichioides, Aspergillus flavus, Rhizoctonia solani,Sclerotinia spp. and Verticillium dahliae. The biological activity of these compounds was assessed in terms of growth inhibition and, for the two mycotoxigenic species A. flavus and F. sporotrichioides, also in terms of toxin containment. As expected, the inhibitory effect of molecules greatly varied amongst both genera and species; cis-jasmone thiosemicarbazone in particular has shown the wider range of effectiveness. However, our results show that thiosemicarbazones derivatives are more effective than the parent ketones in limiting fungal growth and mycotoxins production, supporting possible applications for the control of pathogenic fungi.

Download Full-text

Novel Bifunctional Inhibitor of Xylanase and Aspartic Protease: Implications for Inhibition of Fungal Growth

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.45.7.2008-2017.2001 ◽

2001 ◽

Vol 45 (7) ◽

pp. 2008-2017 ◽

Cited By ~ 22

Author(s):

Chandravanu Dash ◽

Absar Ahmad ◽

Devyani Nath ◽

Mala Rao

Keyword(s):

Growth Inhibition ◽

Fungal Growth ◽

Phytopathogenic Fungi ◽

Aspartic Protease ◽

Cellular Growth ◽

Alternative Mechanism ◽

Trinitrobenzenesulfonic Acid ◽

Woodward’S Reagent K ◽

Bifunctional Inhibitor ◽

Fungal Growth Inhibition

ABSTRACT A novel bifunctional inhibitor (ATBI) from an extremophilicBacillus sp. exhibiting an activity against phytopathogenic fungi, including Alternaria, Aspergillus, Curvularia, Colletotricum, Fusarium, and Phomopsis species, and the saprophytic fungus Trichoderma sp. has been investigated. The 50% inhibitory concentrations of ATBI ranged from 0.30 to 5.9 μg/ml, whereas the MIC varied from 0.60 to 3.5 μg/ml for the fungal growth inhibition. The negative charge and the absence of periodic secondary structure in ATBI suggested an alternative mechanism for fungal growth inhibition. Rescue of fungal growth inhibition by the hydrolytic products of xylanase and aspartic protease indicated the involvement of these enzymes in cellular growth. The chemical modification of Asp or Glu or Lys residues of ATBI by 2,4,6-trinitrobenzenesulfonic acid and Woodward's reagent K, respectively, abolished its antifungal activity. In addition, ATBI also inhibited xylanase and aspartic protease competitively, withKi values 1.75 and 3.25 μM, respectively. Our discovery led us to envisage a paradigm shift in the concept of fungal growth inhibition for the role of antixylanolytic activity. Here we report for the first time a novel class of antifungal peptide, exhibiting bifunctional inhibitory activity.

Download Full-text

First Report of Impatiens Downy Mildew Outbreaks Caused by Plasmopara obducens Throughout the Hawai'ian Islands

Plant Disease ◽

10.1094/pdis-10-13-1017-pdn ◽

2014 ◽

Vol 98 (5) ◽

pp. 696-696 ◽

Cited By ~ 7

Author(s):

J. A. Crouch ◽

M. P. Ko ◽

J. M. McKemy

Keyword(s):

United States ◽

Downy Mildew ◽

The United States ◽

Molecular Data ◽

Economic Losses ◽

Voucher Specimen ◽

First Report ◽

Plastic Bags ◽

Leaf Surfaces ◽

Impatiens Walleriana

Downy mildew of impatiens (Impatiens walleriana Hook.f.) was first reported from the continental United States in 2004. In 2011 to 2012, severe and widespread outbreaks were documented across the United States mainland, resulting in considerable economic losses. On May 5, 2013, downy mildew disease symptoms were observed from I. walleriana ‘Super Elfin’ at a retail nursery in Mililani, on the Hawai'ian island of Oahu. Throughout May and June 2013, additional sightings of the disease were documented from the islands of Oahu, Kauai, Maui, and Hawai'i from nurseries, home gardens, and botanical park and landscape plantings. Symptoms of infected plants initially showed downward leaf curl, followed by a stippled chlorotic appearance on the adaxial leaf surfaces. Abaxial leaf surfaces were covered with a layer of white mycelia. Affected plants exhibited defoliation, flower drop, and stem rot as the disease progressed. Based on morphological and molecular data, the organism was identified as Plasmopara obducens (J. Schröt.) J. Schröt. Microscopic observation disclosed coenocytic mycelium and hyaline, thin-walled, tree-like (monopodial branches), straight, 94.0 to 300.0 × 3.2 to 10.8 μm sporangiophores. Ovoid, hyaline sporangia measuring 11.0 to 14.6 × 12.2 to 16.2 (average 13.2 × 14.7) μm were borne on sterigma tips of rigid branchlets (8.0 to 15.0 μm) at right angle to the main axis of the sporangiophores (1,3). Molecular identification of the pathogen was conducted by removing hyphae from the surface of three heavily infected leaves using sterile tweezers, then extracting DNA using the QIAGEN Plant DNA kit (QIAGEN, Gaithersburg, MD). The nuclear rDNA internal transcribed spacer was sequenced from each of the three samples bidirectionally from Illustra EXOStar (GE Healthcare, Piscataway, NJ) purified amplicon generated from primers ITS1-O and LR-0R (4). Resultant sequences (GenBank KF366378 to 80) shared 99 to 100% nucleotide identity with P. obducens accession DQ665666 (4). A voucher specimen (BPI892676) was deposited in the U.S. National Fungus Collections, Beltsville, MD. Pathogenicity tests were performed by spraying 6-week-old impatiens plants (I. walleriana var. Super Elfin) grown singly in 4-inch pots with a suspension of 1 × 104 P. obducens sporangia/ml until runoff using a handheld atomizer. Control plants were sprayed with distilled water. The plants were kept in high humidity by covering with black plastic bags for 48 h at 20°C, and then maintained in the greenhouse (night/day temperature of 20/24°C). The first symptoms (downward curling and chlorotic stippling of leaves) and sporulation of the pathogen on under-leaf surfaces of the inoculated plants appeared at 10 days and 21 days after inoculation, respectively. Control plants remained healthy. Morphological features and measurements matched those of the original inoculum, thus fulfilling Koch's postulates. To our knowledge, this is the first report of downy mildew on I. walleriana in Hawai'i (2). The disease appears to be widespread throughout the islands and is likely to cause considerable losses in Hawai'ian landscapes and production settings. References: (1) O. Constantinescu. Mycologia 83:473, 1991. (2) D. F. Farr and A. Y. Rossman. Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ July 16, 2013. (3) P. A. Saccardo. Syllogue Fungorum 7:242, 1888. (4) M. Thines. Fungal Genet Biol 44:199, 2007.

Download Full-text

First Report of Stigmina palmivora Causing Leaf Spots on Phoenix roebelenii in Brazil

Plant Disease ◽

10.1094/pdis-10-13-1030-pdn ◽

2014 ◽

Vol 98 (6) ◽

pp. 849-849 ◽

Cited By ~ 1

Author(s):

A. Colmán ◽

R. A. da Silva ◽

R. Alves ◽

M. Silva ◽

R. W. Barreto

Keyword(s):

Pure Culture ◽

Leaf Surface ◽

The United States ◽

Culture Collection ◽

Commonwealth Mycological Institute ◽

First Report ◽

Leaf Spots ◽

Nucleotide Homology ◽

Query Coverage ◽

Representative Samples

Phoenix roebelenii (Arecaceae), known as dwarf date (tamareira-anã in Brazil), is a palm native to Southeast Asia and widely cultivated worldwide because of its ornamental value and ease of adaptation to a broad range of climates and soil types (4). In June 2012, some individuals were observed in a private garden in the municipality of Viçosa (state of Minas Gerais, Brazil) bearing numerous necrotic lesions on its leaves. Representative samples were taken, dried in a plant press, and brought to the laboratory for examination. A fungus was regularly associated with the leaf spots. Fungal structures were mounted in lactophenol and slides were examined under a microscope (Olympus BX 51). Spores were taken from sporulating colonies with a sterile fine needle and plated on PDA for isolation. A pure culture was deposited in the culture collection of the Universidade Federal de Viçosa (accession COAD1338). A dried herbarium sample was deposited in the local herbarium (VIC39741). The fungus had the following morphology: conidiophores grouped on sporodochia, cylindrical, 12 to 29 × 5 to 6 μm, dark brown; conidiogenous cells, terminal, proliferating percurrently (annellidic), 8 to 20 × 5 to 6 μm, pale to dark brown; conidia obclavate to subcylindrical, straight, 58 to 147 × 5 to 6 μm, 6 to 16 septate, hila thickened and darkened with a thin-walled projecting papilla, dark brown, and verrucose. The morphology of the Brazilian collections agrees well with the description of Stigmina palmivora (2), a species known to cause leaf spots on P. roebelenii in the United States (Florida) and Japan (3). Pathogenicity was demonstrated through inoculation of leaves of healthy plants by placing 6 mm diameter cuture disks of COAD1338 on the leaf surface followed by incubation in a moist chamber for 48 h and then transferred to a greenhouse bench at 21 ± 3°C. Typical leaf spots were observed 15 days after inoculation. DNA was extracted from the isolate growing in pure culture and ITS and LSU sequences were generated and deposited in GenBank under the accession numbers KF656785 and KF656786, respectively. These were compared by BLASTn with other entries in GenBank, and the closest match for each region were Mycosphaerella colombiensis strain X215 and M. irregulariamosa strain CPC 1362 (EU514231, GU2114441) with 93% of nucleotide homology (over 100% query coverage) for ITS and 98% of nucleotide homology (over 100% query coverage) for LSU. There are no sequences for S. palmivora deposited in public databases for comparison, but for Stigmina platani, the type species in this genus, 86% and 96% nucleotide homology for ITS and LSU with S. palmivora were found. The genus Stigmina is regarded as being polyphyletic (1) and this is probably reflected by these low homology levels found in the BLASTn search. To our knowledge, this is the first report of Stigmina palmivora in Brazil. References: (1) P. W. Crous et al. Stud. Mycol. 75:37, 2012. (2) M. B. Ellis. Dematiaceous Hyphomycetes. Commonwealth Mycological Institute, Kew, UK, 1971. (3) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab. ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , 2013. (4) H. Lorenzi et al. Palmeira no Brasil: Exóticas e Nativas, 2nd ed. Editora Plantarum, Nova Odessa, Brazil, 2005.

Download Full-text

First Report of Leaf Blight and Stem Canker of Pachysandra terminalis Caused by Pseudonectria pachysandricola in Korea

Plant Disease ◽

10.1094/pdis-09-11-0813 ◽

2012 ◽

Vol 96 (2) ◽

pp. 287-287

Author(s):

K. S. Han ◽

J. H. Park ◽

S. E. Cho ◽

H. D. Shin

Keyword(s):

United States ◽

Its Region ◽

Stem Canker ◽

The United States ◽

Culture Collection ◽

Leaf Blight ◽

First Report ◽

Cornell University ◽

Plastic Bags ◽

Young Leaves

Pachysandra terminalis Siebold & Zucc., known as Japanese pachysandra, is a creeping evergreen perennial belonging to the family Buxaceae. In April 2011, hundreds of plants showing symptoms of leaf blight and stem canker with nearly 100% incidence were found in a private garden in Suwon, Korea. Plants with the same symptoms were found in Seoul in May and Hongcheon in August. Affected leaves contained tan-to-yellow brown blotches. Stem and stolon cankers first appeared as water soaked and developed into necrotic lesions. Sporodochia were solitary, erumpent, circular, 50 to 150 μm in diameter, salmon-colored, pink-orange when wet, and with or without setae. Setae were hyaline, acicular, 60 to 100 μm long, and had a base that was 4 to 6 μm wide. Conidiophores were in a dense fascicle, not branched, hyaline, aseptate or uniseptate, and 8 to 20 × 2 to 3.5 μm. Conidia were long, ellipsoid to cylindric, fusiform, rounded at the apex, subtruncate at the base, straight to slightly bent, guttulate, hyaline, aseptate, 11 to 26 × 2.5 to 4.0 μm. A single-conidial isolate formed cream-colored colonies that turned into salmon-colored colonies on potato dextrose agar (PDA). Morphological and cultural characteristics of the fungus were consistent with previous reports of Pseudonectria pachysandricola B.O. Dodge (1,3,4). Voucher specimens were housed at Korea University (KUS). Two isolates, KACC46110 (ex KUS-F25663) and KACC46111 (ex KUS-F25683), were accessioned in the Korean Agricultural Culture Collection. Fungal DNA was extracted with DNeasy Plant Mini DNA Extraction Kits (Qiagen Inc., Valencia, CA). The complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced using ABI Prism 337 automatic DNA sequencer (Applied Biosystems, Foster, CA). The resulting sequence of 487 bp was deposited in GenBank (Accession No. JN797821). This showed 100% similarity with a sequence of P. pachysandricola from the United States (HQ897807). Isolate KACC46110 was used in pathogenicity tests. Inoculum was prepared by harvesting conidia from 2-week-old cultures on PDA. Ten young leaves wounded with needles were sprayed with conidial suspensions (~1 × 106 conidia/ml). Ten young leaves that served as the control were treated with sterile distilled water. Plants were covered with plastic bags to maintain a relative humidity of 100% at 25 ± 2°C for 24 h. Typical symptoms of brown spots appeared on the inoculated leaves 4 days after inoculation and were identical to the ones observed in the field. P. pachysandricola was reisolated from 10 symptomatic leaf tissues, confirming Koch's postulates. No symptoms were observed on control plants. Previously, the disease was reported in the United States, Britain, Japan, and the Czech Republic (2,3), but not in Korea. To our knowledge, this is the first report of P. pachysandricola on Pachysandra terminalis in Korea. Since this plant is popular and widely planted in Korea, this disease could cause significant damage to nurseries and the landscape. References: (1) B. O. Dodge. Mycologia 36:532, 1944. (2) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , September 24, 2011. (3) I. Safrankova. Plant Prot. Sci. 43:10, 2007. (4) W. A. Sinclair and H. H. Lyon. Disease of Trees and Shrubs. 2nd ed. Cornell University Press, Ithaca, NY, 2005.

Download Full-text

First Report of Leaf Spot of Sweet Basil Caused by Cercospora guatemalensis in Korea

Plant Disease ◽

10.1094/pdis-05-12-0436-pdn ◽

2012 ◽

Vol 96 (10) ◽

pp. 1580-1580

Author(s):

J. H. Park ◽

K. S. Han ◽

J. Y. Kim ◽

H. D. Shin

Keyword(s):

Leaf Spot ◽

Morphological Characteristics ◽

Its Region ◽

Culture Collection ◽

Distilled Water ◽

First Report ◽

Sweet Basil ◽

Organic Farm ◽

Leaf Spots ◽

Close Phylogenetic Relationship

Sweet basil, Ocimum basilicum L., is a fragrant herb belonging to the family Lamiaceae. Originated in India 5,000 years ago, sweet basil plays a significant role in diverse cuisines across the world, especially in Asian and Italian cooking. In October 2008, hundreds of plants showing symptoms of leaf spot with nearly 100% incidence were found in polyethylene tunnels at an organic farm in Icheon, Korea. Leaf spots were circular to subcircular, water-soaked, dark brown with grayish center, and reached 10 mm or more in diameter. Diseased leaves defoliated prematurely. The damage purportedly due to this disease has reappeared every year with confirmation of the causal agent made again in 2011. A cercosporoid fungus was consistently associated with disease symptoms. Stromata were brown, consisting of brown cells, and 10 to 40 μm in width. Conidiophores were fasciculate (n = 2 to 10), olivaceous brown, paler upwards, straight to mildly curved, not geniculate in shorter ones or one to two times geniculate in longer ones, 40 to 200 μm long, occasionally reaching up to 350 μm long, 3.5 to 6 μm wide, and two- to six-septate. Conidia were hyaline, acicular to cylindric, straight in shorter ones, flexuous to curved in longer ones, truncate to obconically truncate at the base, three- to 16-septate, and 50 to 300 × 3.5 to 4.5 μm. Morphological characteristics of the fungus were consistent with the previous reports of Cercospora guatemalensis A.S. Mull. & Chupp (1,3). Voucher specimens were housed at Korea University herbarium (KUS). An isolate from KUS-F23757 was deposited in the Korean Agricultural Culture Collection (Accession No. KACC43980). Fungal DNA was extracted with DNeasy Plant Mini DNA Extraction Kits (Qiagen Inc., Valencia, CA). The complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced. The resulting sequence of 548 bp was deposited in GenBank (Accession No. JQ995781). This showed >99% similarity with sequences of many Cercospora species, indicating their close phylogenetic relationship. Isolate of KACC43980 was used in the pathogenicity tests. Hyphal suspensions were prepared by grinding 3-week-old colonies grown on PDA with distilled water using a mortar and pestle. Five plants were inoculated with hyphal suspensions and five plants were sprayed with sterile distilled water. The plants were covered with plastic bags to maintain a relative humidity of 100% for 24 h and then transferred to a 25 ± 2°C greenhouse with a 12-h photoperiod. Typical symptoms of necrotic spots appeared on the inoculated leaves 6 days after inoculation, and were identical to the ones observed in the field. C. guatemalensis was reisolated from symptomatic leaf tissues, confirming Koch's postulates. No symptoms were observed on control plants. Previously, the disease was reported in Malawi, India, China, and Japan (2,3), but not in Korea. To our knowledge, this is the first report of C. guatemalensis on sweet basil in Korea. Since farming of sweet basil has recently started on a commercial scale in Korea, the disease poses a serious threat to safe production of this herb, especially in organic farming. References: (1) C. Chupp. A Monograph of the Fungus Genus Cercospora. Ithaca, NY, 1953. (2) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology & Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , May 5, 2012. (3) J. Nishikawa et al. J. Gen. Plant Pathol. 68:46, 2002.

Download Full-text