First Report of Fulvia fulva, Causal Agent of Tomato Leaf Mold, in Greenhouses in Southeastern Spain

Tomato (Solanum lycopersicum L.) is produced in more than 9,000 ha of greenhouses in Almería (southeastern Spain). During 2006 and 2007, a new disease was observed on almost all plants in 37 greenhouses. Yellow spots on upper and lower leaf surfaces were accompanied by gray-to-dark brown mycelia, conidiophores, and conidia on lower leaf surfaces. Affected leaves became necrotic and withered. Six isolates grown on malt extract agar (MEA) were identified as Fulvia fulva (1). The one- to three-celled conidia ranged from 21.8 × 7.8 μm to 21.5 × 6.5 μm. On MEA, potato dextrose agar, and V8 juice agar, the pathogen grew slowly; colonies were only 1 cm in diameter after 30 days. Colony color was initially intense yellow but became dark brown with age. In a growth chamber (12,000 lux for 16 h per day, 23 to 28°C, and 60 to 95% relative humidity), six pots containing five tomato plants (cv. SanPedro) at the four-true-leaf stage were inoculated with a conidial suspension (103 CFU/ml) of F. fulva. Control plants were sprayed with water. The trial was repeated once. Immediately after inoculation, plants were sealed in plastic bags for 8 days. Symptoms of the disease and signs of the pathogen were observed on all inoculated plants 18 days after inoculation. To our knowledge, this is the first report of leaf mold of tomato in Almería and it is becoming common in the greenhouse industry in this region. Reference: (1) P. Holliday and J. L. Mulder. No. 487 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1976.

Download Full-text

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.

Download Full-text

First Report of Ascochyta Leaf Spot Caused by Phoma exigua var. exigua on Common Bean in Greece

Plant Disease ◽

10.1094/pdis-92-4-0653c ◽

2008 ◽

Vol 92 (4) ◽

pp. 653-653 ◽

Cited By ~ 3

Author(s):

G. A. Bardas ◽

G. T. Tziros ◽

K. Tzavella-Klonari

Keyword(s):

Common Bean ◽

Leaf Spot ◽

Morphological Characteristics ◽

Pathogenic Fungi ◽

Weather Conditions ◽

Conidial Suspension ◽

Phoma Exigua ◽

First Report ◽

Plastic Bags ◽

And Control

Common bean (Phaseolus vulgaris L.) is cultivated extensively in Greece for dry and fresh bean production. During 2005 and 2006, a disease with typical blight symptoms was observed occasionally on dark red kidney, brown kidney, and black bean plants in most bean-producing areas of Greece. It rarely was destructive unless the crop had been weakened by some unfavorable environmental conditions. Infected leaves had brown-to-black lesions that developed concentric zones 10 to 30 mm in diameter and also contained small, black pycnidia. Concentric dark gray-to-black lesions also appeared on branches, stems, nodes, and pods. Infected seeds turned brown to black. Plants sometimes showed defoliation and pod drop. The fungus was consistently isolated on potato dextrose agar from diseased leaves and pods and identified as Phoma exigua var. exigua Sutton and Waterstone on the basis of morphological characteristics of conidia and pycnidia (1,2). Spores were massed in pycnidia from which they were forced in long, pink tendrils under moist weather conditions. Conidia were cylindrical to oval, allantoid, hyaline, pale yellow to brown, usually one-celled, and 2 to 3 × 5 to 10 μm. To satisfy Koch's postulates, a conidial suspension (1 × 106 conidia per ml) of the fungus was sprayed onto leaves and stems of bean seedlings (first-leaf stage) (cv. Zargana Hrisoupolis). Both inoculated and control seedlings (inoculated with sterile water) were covered with plastic bags for 72 h in a greenhouse at 23°C. Inoculated plants showed characteristic symptoms of Ascochyta leaf spot 12 to 15 days after inoculation. The fungus was reisolated from lesions that developed on the leaves and stems of all inoculated plants. The pathogen is present worldwide on bean. To our knowledge, this is the first report of P. exigua var. exigua on common bean in Greece. References: (1) D. F. Farr et al. Fungal Databases. Systematic Botany and Mycology Laboratory. Online publication. ARS, USDA, 2007. (2) B. C. Sutton and J. M. Waterstone. Ascochyta phaseolorum. No. 81 in: Descriptions of Pathogenic Fungi and Bacteria. CMI/AAB, Kew, Surrey, England, 1966.

Download Full-text

First Report of Black Spot Caused by Colletotrichum gloeosporioides on Paper Mulberry in China

Plant Disease ◽

10.1094/pdis-03-11-0186 ◽

2011 ◽

Vol 95 (7) ◽

pp. 880-880 ◽

Cited By ~ 15

Author(s):

J. Yan ◽

P. S. Wu ◽

H. Z. Du ◽

Q. E. Zhang

Keyword(s):

Colletotrichum Gloeosporioides ◽

Black Spot ◽

Pathogenic Fungi ◽

Conidial Suspension ◽

Stem Cuttings ◽

Sterile Water ◽

First Report ◽

Forest Park ◽

Plastic Bags ◽

Black Spots

Paper mulberry, Broussonetia papyrifera (L.) Venten. (family Moraceae), is a fast-growing tree with luxuriant branches and leaves. Because of strong adaptability and tolerance to unfavorable environmental conditions, it is an important tree species for shade or shelter and reforestation in mined areas and on hillsides. During the summer of 2010, brown-to-black spots were observed on leaves of paper mulberry in Baiwangshan Forest Park in Beijing, China. Early symptoms were round or elliptic, light brown, small lesions that later extended to round or irregular spots (4 to 6 × 4 to 8 mm) that were dark brown or black in the center with brown or light brown margins. Several dozen spots were found on severely infected leaves. Leaf tissues (2 × 2 mm), cut from the margins of lesions, were surface disinfected in 0.5% NaOCl solution for 3 min, rinsed three times with sterile water, plated on potato dextrose agar (PDA) and incubated at 25°C with a 12-h light and 12-h dark period. Numerous waxy subepidermal acervuli with setae were observed after 3 days. Acervuli were brown or black, round or elongate, and 100 to 250 μm in diameter. Setae were dark brown, erect straight or slightly curved, and 60 to 74 × 4 to 8 μm with one to two septa. Conidiophores were hyaline or light brown, short with no branches, and cylindrical with dimensions of 12 to 21 × 4 to 5 μm. Conidia were 11 to 21 × 3 to 6 μm, hyaline, aseptate, and cylindrical. Mycelia on PDA were off white-to-dark gray on the reverse side of the colony. Six isolates (BP21-1 to BP21-6) were obtained from different infected leaves and identified as Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. (teleomorph Glomerella cingulata (Stonem.) Spaulding & Schrenk) on the basis of reverse colony color, dimensions and colors of acervuli, conidiophores, and conidia (3). ITS1-5.8S-ITS2 rDNA sequence analysis was performed on all six isolates. The resultant sequences were identical (GenBank Accession No. HQ 654780) and revealed 99% similarity (100% coverage) with C. gloeosporioides isolates in the GenBank (Accession Nos. EU371022.1 and AY376532.1) (2). Pathogenicity was demonstrated using six potted 3-month-old paper mulberry trees. Isolate BP21-2 was grown on PDA for 14 days and conidia were harvested to prepare a suspension of 106 conidia/ml. Three plants were sprayed with the conidial suspension and three were sprayed with sterile water. All trees were covered with plastic bags for 24 h to maintain high humidity and incubated at 25°C for 6 days. All conidia-inoculated trees showed identical symptoms as the infected leaves in the park, while the control trees remained symptom free. Reisolation of the fungus confirmed that the causal agent was C. gloeosporioides. C. gloeosporioides is distributed worldwide causing anthracnose on a wide variety of plants including members of mulberry family Moraceae, e.g., mortality of stem cuttings and death of saplings on mulberry (Morus alba L.) in India (1). To our knowledge, this is the first report of C. gloeosporioides causing black spots on paper mulberry in China. References: (1) V. P. Gupta et al. Indian Phytopathol. 50:402, 1997. (2) K. D. Hyde et al. Fungal Divers. 39:147, 2009. (3) J. E. M. Mordue. No. 315 in: Descriptions of Pathogenic Fungi and Bacteria. CMI. Kew, Surrey, UK, 1971.

Download Full-text

First Report of Gummosis Disease of Plum (Prunus salicina) Caused by a Botryosphaeria sp. in Taiwan

Plant Disease ◽

10.1094/pdis-92-3-0483a ◽

2008 ◽

Vol 92 (3) ◽

pp. 483-483 ◽

Cited By ~ 1

Author(s):

Y. Ko ◽

K. S. Yao ◽

C. Y. Chen ◽

C. W. Liu ◽

S. Maruthasalam ◽

...

Keyword(s):

Pathogenic Fungi ◽

Fluorescent Light ◽

Conidial Suspension ◽

Tropical Regions ◽

First Report ◽

Cornell University ◽

Ring Rot ◽

Prunus Salicina ◽

Plastic Bags ◽

Pathogenicity Tests

Plum (Prunus salicina Lindell) is grown on more than 3,870 ha in Taiwan. In 2004, a gummosis disease was observed on plum in the Ming Jian Region of Nantou County (120.675°E, 23.919°N), with 15% of the trees affected. Infections started on the current year's growth, primarily through lenticels, and formed small, sunken, discolored lesions. At later stages, white gum exuded from the lesions. Circular to oval, brown, necrotic areas were seen on the inner bark. Severely infected twigs showed defoliation and dieback. During the 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) and incubated at 25 ± 1°C for 3 days. On the basis of morphological traits, the fungus was identified as a Botryosphaeria sp. according to the CMI descriptions of Botryosphaeria ribis (3). Conidia (14.2 to 26.8 × 4.3 to 7.2 μm) were single celled, hyaline, and spindle shaped. Asci (105 to 135 × 12.5 to 15.5 μm) were hyaline, clavate, and bitunicate. Ascospores (18 to 22 × 7.0 to 8.2 μm) were hyaline and spindle shaped or fusoid. For pathogenicity tests, inoculum was prepared by culturing the fungus on PDA under continuous fluorescent light (128 ± 25 μE·m–2·s–1) at 25°C for 3 days. Two twigs on each of six trees were inoculated. Sharp incisions (3 × 3 × 3 mm) were made on healthy twigs (12 to 15 months old) with a sterilized scalpel and inoculated with either a 5-mm mycelial disc or 0.5 ml of a conidial suspension (105 conidia/ml) of the fungus. Inoculated areas were covered with moist, sterile cotton and the entire twigs were enclosed in plastic bags. Twigs inoculated with 5-mm PDA discs or sterile water alone served as controls. The symptoms described above were observed on all inoculated twigs 14 days after inoculation, whereas control twigs did not develop any disease symptoms. Reisolation from the inoculated twigs consistently yielded the Botryosphaeria sp., thus fulfilling Koch's postulates. Botryosphaeria spp. have been reported to cause stem blight of many plants in temperate and tropical regions of the world (4). In Taiwan, B. dothidea has been reported as the causal agent of gummosis disease of peach (1) and fruit ring rot of pear (2); however, to our knowledge, this is the first report of a Botryosphaeria sp. causing gummosis of plum. 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) E. Punithalingam and P. Holliday. No. 395 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1973. (4) W. A. Sinclair et al. Diseases of Trees and Shrubs. Cornell University Press, Ithaca, NY, 1987.

Download Full-text

First Report of Botrytis Blight on Medinilla magnifica and Various Species of Mandevilla and Allamanda in Italy

Plant Disease ◽

10.1094/pdis.2002.86.10.1175a ◽

2002 ◽

Vol 86 (10) ◽

pp. 1175-1175

Author(s):

A. M. Pennisi ◽

S. O. Cacciola ◽

F. Raudino ◽

A. Pane

Keyword(s):

Glucose Solution ◽

Brown Rot ◽

Pathogenic Fungi ◽

Tropical Species ◽

Conidial Suspension ◽

Transparent Plastic ◽

First Report ◽

Plastic Bags ◽

Lateral Branches ◽

Modal Values

Medinilla magnifica Lindl., Mandevilla splendens (Hook.) Woodson, the hybrid Mandevilla × amoena ‘Alice du Pont’ (pink allamanda), and various species of Allamanda, such as A. cathartica L. and A. blanchetii A. DC. (purple allamanda), are grown in Sicily as ornamentals. After a frost in early December 2001, a sudden wilt of container-grown cuttings of these tropical species was observed in a plastic-covered production greenhouse, with ≈30% of M. magnifica plants and 70% of Mandevilla and Allamanda plants affected. Medinilla plants (≈35 cm high) had been rooted in trays and transplanted individually in 30-cm-diameter pots. Allamanda (recently rooted cuttings) and Mandevilla (well-established) plants showed symptoms ranging from a dark brown rot at the base of stems to a tan-to-brown rot of stem midsection, respectively. Tissues surrounding lesions were water-soaked and covered by gray mycelium. On Allamanda and Mandevilla plants, lesions extended rapidly to lateral branches, and to the petiole and midrib of leaves that became chlorotic and wilted. As stems were girdled, infected plants collapsed, although the roots appeared healthy. Botrytis cinerea Pers.:Fr. was consistently isolated from infected stem pieces surface-disinfested with 1% NaOCl for 1 min and placed on potato dextrose agar (PDA, Oxoid). Morphology and size (6 to 8 × 8 to 12 μm, modal values 7 × 10 μm) of conidia produced on PDA matched those reported for B. cinerea (1). Dark, spherical, and irregularly shaped sclerotia (1 to 6 mm diameter, mean size 3.3 × 2.3 mm) were produced on PDA. Pathogenicity of a single-conidium isolate isolated from M. magnifica was confirmed using two inoculation methods. Twenty 3-month-old cuttings of M. magnifica and pink and purple allamanda were sprayed with a conidial suspension (106 conidia per ml in a 2% glucose solution). A 2% glucose solution was sprayed on 20 control plants. Plants were sealed in transparent plastic bags for 7 days at 15 to 24°C. Typical symptoms developed only on stems of inoculated pink and purple allamanda cuttings 7 days after inoculation. B. cinerea was reisolated from affected tissues. In a separate test, stems of 10 6-month-old plants of M. magnifica and pink allamanda were inoculated by inserting a 3-mm plug taken from 10-day-old sporulating colonies growing on PDA on a superficial cut made with a sterile scalpel. The inoculated wounds were sealed with Parafilm. Ten wounded but noninoculated plants were used as controls. Plants were kept in high humidity at 10 to 20°C. After 10 days, stem necrosis, leaf chlorosis, and wilt were observed on inoculated pink allamanda plants. On inoculated M. magnifica plants, necrotic lesions were observed on stems (45 to 70 mm long and 10 to 18 mm wide) covered by gray mycelium, but the stem was not girdled. B. cinerea was reisolated from infected tissues of inoculated plants to complete Koch's postulates. No lesions developed on noninoculated control plants. To our knowledge, this is the first report from Italy of Botrytis blight on these species. The occurrence of frost may have predisposed these tropical species to infection by B. cinerea. Reference: (1) M. B. Ellis and J. M. Waller. No 431 in: Descriptions of Pathogenic Fungi and Bacteria, CMI, Kew, Surrey, UK, 1974.

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 Fusarium oxysporum f. sp. lycopersici Race 3 and F. oxysporum f. sp. radicis-lycopersici in Tomatoes in the Azapa Valley of Chile

Plant Disease ◽

10.1094/pdis-03-14-0303-pdn ◽

2014 ◽

Vol 98 (10) ◽

pp. 1432-1432 ◽

Cited By ~ 4

Author(s):

G. Sepúlveda-Chavera ◽

W. Huanca ◽

R. Salvatierra-Martínez ◽

B. A. Latorre

Keyword(s):

Fusarium Oxysporum ◽

Tap Water ◽

Universal Primers ◽

Conidial Suspension ◽

Laboratory Manual ◽

First Report ◽

Solanum Lycopersicum L ◽

Vascular Discoloration ◽

Seedling Roots ◽

Pcr Assays

Tomato (Solanum lycopersicum L.) is an important crop in the Azapa Valley (18°35′ S, 69°30′ W) in northern Chile, with approximately 600 ha of fresh tomatoes under greenhouses. Cultivars resistant to Fusarium oxysporum f. sp. lycopersici (FOL) races 1 and 2 are mainly used. However, in 2012 and 2013, Fusarium wilt incidence was 2 to 3%. Symptoms appeared unilaterally and consisted of yellowing, leaf wilting of lower leaves, dark brown vascular discoloration, and plant death. The aim of this study was to determine the causal agent of tomato wilt in seven tomato greenhouses in the Azapa Valley. Stem samples (5 × 5 mm) were obtained 10 cm of the stem base from wilted tomatoes ‘Naomi’ (BIOAMERICA S.A., Chile) or from Maxifort tomato rootstock (De Ruiter Seed, USA), both FOL resistant to races 1 and 2. Samples were washed with tap water, surface sterilized with 1% NaClO for 3 min, and incubated on sterile moist paper towels in petri plates for 5 days at 22°C. Mycelial fragments from white colonies, emerging from diseased tissues, were transferred to PDA. Six Fusarium isolates were characterized by the presence of hyaline macroconidia, mostly 3 to 5 septate, slightly curved (19.2 to 32.1 × 2.9 to 4.5 μm) and single-celled, oval to elongated microconidia (3.1 to 8.9 × 2.0 to 4.0 μm). Chlamydospores were single or in pairs. These isolates were identified as F. oxysporum (3). The identity of F. oxysporum was confirmed by PCR assays using genomic DNA of each isolated and the universal primers Uni F and Uni R that generate a 672-bp PCR product. The pathogenic form and races were determined by PCR assays using the specific primers uni, sp13, sp23, and sprl that were able to discriminate all the three FOL races as well as F. oxysporum f. sp. radicis-lycopersici (FORL) isolates (2). The sp13 and sp23 primers amplified DNA bands of 445 and 518 bp, confirming the identity of FOL race 3. However, sprl amplified a fragment of 947 bp corresponding to FORL (2). Pathogenicity tests were conducted on 25-day-old seedlings (10 seedlings per isolate) of tomato ‘Poncho Negro,’ which is susceptible to FOL and FORL. Seedling roots were cut, submerged for 5 min in conidial suspension of 2 × 106 conidia/ml, and transplanted to 250-ml plastic containers with sterile substrate (sand/peat, 1:1). Equally treated non-inoculated seedlings were left as controls. The first symptoms induced by each of the five FOL isolates appeared 8 days after incubation under greenhouse and were characterized by yellowing of older leaves, sometimes affecting one side of the plant, vascular discoloration of the stem, and eventually plant death. In contrast, all seedlings inoculated with a FORL isolate developed a necrotic lesion and vascular discoloration at the base of the stems near the soil line, followed by wilting and plant death. Control plants remained asymptomatic. F. oxysporum was re-isolated only from inoculated plants, completing Koch's postulates. FOL and FORL were reported earlier in other tomato growing areas of Chile (1), located over 1,000 km south of the Azapa Valley. However, this is the first report of FOL race 3 and FORL in the Azapa Valley and FOL race 3 is reported for the first time in Chile. References: (1) S. Acuña. Compendio de Fitopatógenos de Cultivos Agrícolas. Servicio Agrícola y Ganadero. Gobierno de Chile, 2008. (2) Y. Hirano and T. Arie. J. Gen. Plant Pathol. 72:273, 2006. (3) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Publishing, Ames, IA, 2006.

Download Full-text

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.

Download Full-text

First Report of Myrothecium roridum Causing Myrothecium Leaf Spot on Salvia spp. in the United States

Plant Disease ◽

10.1094/pdis-91-6-0772b ◽

2007 ◽

Vol 91 (6) ◽

pp. 772-772 ◽

Cited By ~ 7

Author(s):

J. A. Mangandi ◽

T. E. Seijo ◽

N. A. Peres

Keyword(s):

United States ◽

Leaf Spot ◽

Pathogenic Fungi ◽

Lower Surface ◽

The United States ◽

Plant Diseases ◽

Control Measures ◽

Conidial Suspension ◽

First Report ◽

Myrothecium Roridum

The genus Salvia includes at least 900 species distributed worldwide. Wild species are found in South America, southern Europe, northern Africa, and North America. Salvia, commonly referred to as sage, is grown commercially as a landscape plant. In August 2006, pale-to-dark brown, circular leaf spots 5 to 20 mm in diameter with concentric rings were observed on Salvia farinacea ‘Victoria Blue’. Approximately 5% of the plants in a central Florida nursery were affected. Lesions were visible on both leaf surfaces, and black sporodochia with white, marginal hyphal tuffs were present mostly on the lower surface in older lesions. Symptoms were consistent with those of Myrothecium leaf spot described on other ornamentals such as gardenia, begonia, and New Guinea impatiens (4). Isolations from lesions on potato dextrose agar produced white, floccose colonies with sporodochia in dark green-to-black concentric rings. Conidia were hyaline and cylindrical with rounded ends and averaged 7.4 × 2.0 μm. All characteristics were consistent with the description of Myrothecium roridum Tode ex Fr. (2,3). The internal transcribed spacer regions ITS1, ITS2, and the 5.8s rRNA genomic region of one isolate were sequenced (Accession No. EF151002) and compared with sequences in the National Center for Biotechnology Information (NCBI) database. Deposited sequences from M. roridum were 96.3 to 98.8% homologous to the isolate from salvia. To confirm pathogenicity, three salvia plants were inoculated by spraying with a conidial suspension of M. roridum (1 × 105 conidia per ml). Plants were covered with plastic bags and incubated in a growth chamber at 28°C for 7 days. Three plants were sprayed with sterile, distilled water as a control and incubated similarly. The symptoms described above were observed in all inoculated plants after 7 days, while control plants remained symptomless. M. roridum was reisolated consistently from symptomatic tissue. There are more than 150 hosts of M. roridum, including one report on Salvia spp. in Brunei (1). To our knowledge, this is the first report of Myrothecium leaf spot caused by M. roridum on Salvia spp. in the United States. Even the moderate level disease present caused damage to the foliage and reduced the marketability of salvia plants. Therefore, control measures may need to be implemented for production of this species in ornamental nurseries. References: (1) D. F. Farr et al. Fungal Databases. Systematic Botany and Mycology Laboratory. Online publication. ARS, USDA, 2006, (2) M. B. Ellis. Page 449 in: Microfungi on Land Plants: An Identification Handbook. Macmillan Publishing, NY, 1985. (3) M. Fitton and P. Holliday. No. 253 in: CMI Descriptions of Pathogenic Fungi and Bacteria. The Eastern Press Ltd. Great Britain, 1970. (4) M. G. Daughtrey et al. Page 19 in: Compendium of Flowering Potted Plant Diseases. The American Phytopathological Society. St. Paul, MN, 1995.

Download Full-text

First Report of Leaf Spot of Spinach Caused by Pleospora betae in Spain

Plant Disease ◽

10.1094/pdis-04-14-0367-pdn ◽

2014 ◽

Vol 98 (11) ◽

pp. 1583-1583 ◽

Cited By ~ 4

Author(s):

D. D. M. Bassimba ◽

J. L. Mira ◽

A. Vicent

Keyword(s):

Leaf Spot ◽

Spinacia Oleracea ◽

Disease Incidence ◽

Control Measures ◽

Conidial Suspension ◽

First Report ◽

Leaf Spots ◽

Plastic Bags ◽

Swiss Chard ◽

Spinach Leaves

The production of spinach (Spinacia oleracea L.) in Spain has increased 50% since 2009, mainly due to the commercialization of fresh-cut spinach leaves packaged in modified atmosphere containers. In October 2012, light brown leaf spots 1 to 2 cm in diameter with dark concentric rings were observed in a commercial spinach production area in Valencia Province, Spain. The initial outbreak comprised an area of about 3 ha with a 20% disease incidence. Symptomatic leaves from spinach cv. Apollo were collected in the affected area and were surface disinfected with 0.5% NaOCl for 2 min. Small fragments from lesions were placed onto potato dextrose agar (PDA) amended with 0.5 g streptomycin sulfate/liter. Fungal colonies developed after 3 days of incubation at 23°C from about 90% of the infected tissues plated. Isolates were transferred to oatmeal agar (OA) (1) and water agar (WA) amended with autoclaved pea seeds (2). Plates were incubated for 30 days at 24°C with 13 h of fluorescent light and 11 h of dark for morphological examination. Colonies were olivaceous grey in OA and pycnidia developed in WA were globose to subglobose, olivaceous black, and 100 to 200 μm in diameter. Conidia were globose to ellipsoidal, hyaline, aseptate, and 3.8 to 7.7 × 2.4 to 3.9 μm. Swollen cells were observed. Isolates showed a positive reaction to NaOH (1). Partial 18S, ITS1, 5.8S, ITS2, and partial 28S ribosomal RNA (rRNA) regions were amplified using the primers ITS1 and ITS4 (4) and sequenced from DNA extracted from the isolate designated as IVIA-V004 (GenBank Accession No. KF321782). The sequence had 100% identity (e-value 0.0) with that of Pleospora betae (Berl.) Nevod. (syn. Phoma betae A.B. Frank) representative strain CBS 523.66 (1). Pathogenicity tests were performed twice by inoculating 4-month-old plants of spinach cv. Apollo, table beet (Beta vulgaris L.) cv. Detroit, and Swiss chard (B. vulgaris subsp. cicla) cv. Verde de Penca Blanca. Plants were inoculated by spraying a conidial suspension of isolate IVIA-V004 (10 ml/plant, 105 conidia/ml water) using a manual pressure sprayer. Plants were immediately covered with black plastic bags and incubated in a growth chamber at 23°C. In each experiment, four plants of each host were inoculated with the fungus and four additional plants sprayed with sterile distilled water were used as controls. Plastic bags were removed after 48 h and leaf spots similar to those observed in affected spinach plants in the field were visible on all spinach, table beets, and Swiss chard plants 3 to 5 days after inoculation. No symptoms were observed on control plants. Fungal colonies morphologically identified as P. betae were re-isolated from leaf lesions on inoculated plants, but not from asymptomatic leaves of control plants. To our knowledge, this is the first report of leaf spot caused by P. betae on spinach in Spain, where it was previously described affecting sugar beet (3). The disease reduces the quality of spinach leaves and proper control measures should be implemented. References: (1) G. H. Boerema et al. Phoma Identification Manual, Differentiation of Specific and Infra-Specific Taxa in Culture. CABI Publishing, Wallingford, UK, 2004. (2) O. D. Dhingra and J. B. Sinclair. Basic Plant Pathology Methods, 2nd ed. CRC Press, Boca Raton, FL, 1995. (3) P. Melgarejo et al. Patógenos de Plantas Descritos en España. MARM-SEF, Madrid, 2010. (4) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA, 1990.

Download Full-text