First Report of Downy Mildew (Hyaloperonospora lunariae) on White Mustard (Sinapis alba) in Brazil

Sinapis alba (Brassicaceae), white mustard, is broadly cultivated for its seed used as component of table mustard (4). In June 2013, a group of diseased S. alba were observed in a vegetable garden on the campus of the Universidade Federal de Viçosa (municipality of Viçosa, state of Minas Gerais, Brazil). Foliage of diseased plants showed numerous chlorotic areas that developed into severe leaf blight with abundant downy mildew growth abaxially. A dried representative specimen has been deposited in the herbarium at the Universidade Federal de Viçosa (accession no. VIC 39743). The fungus had the following morphology: Sporangiophores arborescent, dichotomously branched, 540 to 840 × 8 to 10 μm hyaline, smooth, branches 105 to 210 μm long; esterigmata subacutate and curved, in pairs, 15 to 42 μm long; sporangia globose, 18 to 24 × 15 to 18 μm, hyaline, smooth. DNA was extracted using a Wizard Promega purification kit. The cytochrome oxidase subunit II (COX2) region was amplified with COX2f and COX2r primers (3). The sequence has been deposited in GenBank (Accession No. KJ396953). DNA sequences representing morphologically similar taxa were downloaded from GenBank nucleotide database, aligned in MEGA 5, and analyzed using Bayesian inference and Markov chain Monte Carlo simulation implemented in MrBayes 3.0 with five repetitions. A sequence of Albugo candida was used as outgroup in the analysis. The morphological characteristics places the fungus on S. alba in the complex of species of Pernosporaceae that attack the Brassicaceae. These are notoriously difficult to discriminate by morphology but our COX2-based phylogenetic analysis places it in Hyaloperonospora lunariae (1). This species was previously only known to cause downy mildew on other species of Brassicaceae (Lunaria annua and Erucastrum nasturtiifolium) in Europe (2). To our knowledge, this is the first report of this pathogen-host association in the world. References: (1) O. Constantinescu and J. Fatehi. Nova Hediwigia 74:291, 2002 (2) D. F. Farr and A. Y. Rossman. Fungal Databases, Systematic Mycology and Microbiology Laboratory. Online publication. ARS, USDA, 2013. (3) D. S. S. Hudspeth et al. Mycologia 92:674, 2000. (4) B. B. Simpson and M. C. Ogorzaly. Econonic Botany. McGraw Hill, San Diego, CA, 2001.

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First Report of Leaf Blight of Japanese Yew Caused by Pestalotiopsis microspora in Korea

Plant Disease ◽

10.1094/pdis-08-13-0821-pdn ◽

2014 ◽

Vol 98 (5) ◽

pp. 691-691 ◽

Cited By ~ 2

Author(s):

Y. H. Jeon ◽

W. Cheon

Keyword(s):

Dna Sequences ◽

Apical Cell ◽

Morphological Characteristics ◽

Leaf Blight ◽

Economic Damage ◽

Leaf Margin ◽

Conidial Suspension ◽

First Report ◽

Pestalotiopsis Microspora ◽

Large Trees

Worldwide, Japanese yew (Taxus cuspidata Sieb. & Zucc.) is a popular garden tree, with large trees also being used for timber. In July 2012, leaf blight was observed on 10% of Japanese yew seedling leaves planted in a 500-m2 field in Andong, Gyeongsangbuk-do Province, South Korea. Typical symptoms included small, brown lesions that were first visible on the leaf margin, which enlarged and coalesced into the leaf becoming brown and blighted. To isolate potential pathogens from infected leaves, small sections of leaf tissue (5 to 10 mm2) were excised from lesion margins. Eight fungi were isolated from eight symptomatic trees, respectively. These fungi were hyphal tipped twice and transferred to potato dextrose agar (PDA) plates for incubation at 25°C. After 7 days, the fungi produced circular mats of white aerial mycelia. After 12 days, black acervuli containing slimy spore masses formed over the mycelial mats. Two representative isolates were further characterized. Their conidia were straight or slightly curved, fusiform to clavate, five-celled with constrictions at the septa, and 17.4 to 28.5 × 5.8 to 7.1 μm. Two to four 19.8- to 30.7-μm-long hyaline filamentous appendages (mostly three appendages) were attached to each apical cell, whereas one 3.7- to 7.1-μm-long hyaline appendage was attached to each basal cell, matching the description for Pestalotiopsis microspora (2). The pathogenicity of the two isolates was tested using 2-year-old plants (T. cuspidata var. nana Rehder; three plants per isolate) in 30-cm-diameter pots filled with soil under greenhouse conditions. The plants were inoculated by spraying the leaves with an atomizer with a conidial suspension (105 conidia/ml; ~50 ml on each plant) cultured for 10 days on PDA. As a control, three plants were inoculated with sterilized water. The plants were covered with plastic bags for 72 h to maintain high relative humidity (24 to 28°C). At 20 days after inoculation, small dark lesions enlarged into brown blight similar to that observed on naturally infected leaves. P. microspora was isolated from all inoculated plants, but not the controls. The fungus was confirmed by molecular analysis of the 5.8S subunit and flanking internal transcribed spaces (ITS1 and ITS2) of rDNA amplified from DNA extracted from single-spore cultures, and amplified with the ITS1/ITS4 primers and sequenced as previously described (4). Sequences were compared with other DNA sequences in GenBank using a BLASTN search. The P. microspora isolates were 99% homologous to other P. microspora (DQ456865, EU279435, FJ459951, and FJ459950). The morphological characteristics, pathogenicity, and molecular data assimilated in this study corresponded with the fungus P. microspora (2). This fungus has been previously reported as the causal agent of scab disease of Psidium guajava in Hawaii, the decline of Torreya taxifolia in Florida, and the leaf blight of Reineckea carnea in China (1,3). Therefore, this study presents the first report of P. microspora as a pathogen on T. cuspidata in Korea. The degree of pathogenicity of P. microspora to the Korean garden evergreen T. cuspidata requires quantification to determine its potential economic damage and to establish effective management practices. References: (1) D. F. Farr and A. Y. Rossman, Fungal Databases, Syst. Mycol. Microbiol. Lab. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ (2) L. M. Keith et al. Plant Dis. 90:16, 2006. (3) S. S. N. Maharachchikumbura. Fungal Diversity 50:167, 2011. (4) T. J. White et al. PCR Protocols. Academic Press, San Diego, CA, 1990.

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First Report of Bremia lactucae Causing Downy Mildew on Helichrysum bracteatum in Italy

Plant Disease ◽

10.1094/pdis.2003.87.3.315a ◽

2003 ◽

Vol 87 (3) ◽

pp. 315-315 ◽

Cited By ~ 1

Author(s):

A. Garibaldi ◽

A. Minuto ◽

G. Gilardi ◽

M. L. Gullino

Keyword(s):

Downy Mildew ◽

Morphological Characteristics ◽

The United States ◽

Northern Italy ◽

Plant Diseases ◽

Bremia Lactucae ◽

First Report ◽

Parasitic Fungi ◽

Commercial Farms ◽

Helichrysum Bracteatum

Helichrysum bracteatum, also known as strawflower, is commonly grown for the production of dried flowers and, more recently, as a potted plant. This latter cultivation system is becoming increasingly important on the Liguria Coast in northern Italy. During the spring of 2002, severe oubreaks of a previously unknown disease were observed in commercial farms in the area of Albenga (northern Italy) on several cultivars of H. bracteatum. Leaves of infected plants appeared curled and blistered; the infected portions of leaves turned chlorotic. On the lower leaf surface of chlorotic areas, a dense, whitish growth was evident. Infected leaves eventually wilted without dropping. Basal leaves with poor air circulation were the most severely affected. Certain cultivars of H. bracteatum (such as ‘Florabella Pink’) were most seriously affected, while others (‘Florabella Gold’ and ‘Florabella White’) had less disease. Microscopic observations revealed sporangiophores emerging from the stomata that were dichotomically branched, ending with 4 to 7 sterigmata. The sporangia were globose and measured 15.5 to 16.8 μm in diameter. The pathogen was identified as Bremia lactucae based on the morphological characteristics. Pathogenicity was confirmed by inoculating healthy H. bracteatum (100-day-old ‘Florabella Gold’) as well as Lactuca sativa (25-day-old ‘Salad bowl’) plants with a sporangial suspension (1 × 105 sporangia/ml). Five plants of H. bracteatum and 10 of lettuce were used as replicates. Noninoculated plants served as controls. Inoculated and uninoculated plants were maintained in a growth chamber at 20°C and 90 to 95% relative humidity. After 7 to 10 days, typical symptoms of downy mildew developed on H. bracteatum and lettuce plants artificially inoculated. Bremia lactucae was observed on infected leaves. Uninoculated plants did not show symptoms. To our knowledge, this is the first report of Bremia lactucae on H. bracteatum in Italy. B lactucae was previously reported as the causal agent of downy mildew on H. bracteatum in several countries including the United Kingdom (3), the United States (1), and Egypt (2). References: (1) S. A. Alfieri et al. Index of plant diseases in Florida. Bull No. 11, 1984. (2) H. Elarosi and M. W. Assawah. Rev. Plant Prot. Res., 39:583, 1959. (3) W. C. Moore. British Parasitic Fungi. Cambridge University Press, Cambridge, 1959.

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First Report of Leaf Spot Disease on Walnut Caused by Colletotrichum fioriniae in China

Plant Disease ◽

10.1094/pdis-09-14-0938-pdn ◽

2015 ◽

Vol 99 (2) ◽

pp. 289-289 ◽

Cited By ~ 9

Author(s):

Y. Z. Zhu ◽

W. J. Liao ◽

D. X. Zou ◽

Y. J. Wu ◽

Y. Zhou

Keyword(s):

Dna Sequences ◽

Leaf Spot ◽

Juglans Regia ◽

Morphological Characteristics ◽

Leaf Spot Disease ◽

Koch’S Postulates ◽

First Report ◽

Spot Disease ◽

Leaf Spots ◽

Koch's Postulates

In May 2014, a severe leaf spot disease was observed on walnut tree (Juglans regia L.) in Hechi, Guangxi, China. Leaf spots were circular to semicircular in shape, water-soaked, later becoming grayish white in the center with a dark brown margin and bordered by a tan halo. Necrotic lesions were approximately 3 to 4 mm in diameter. Diseased leaves were collected from 10 trees in each of five commercial orchards. The diseased leaves were cut into 5 × 5 mm slices, dipped in 75% ethanol for 30 s, washed three times in sterilized water, sterilized with 0.1% (w/v) HgCl2 for 3 min, and then rinsed five times with sterile distilled water. These slices were placed on potato dextrose agar (PDA), followed by incubating at 28°C for about 3 to 4 days. Fungal isolates were obtained from these diseased tissues, transferred onto PDA plates, and incubated at 28°C. These isolates produced gray aerial mycelium and then became pinkish gray with age. Moreover, the reverse of the colony was pink. The growth rate was 8.21 to 8.41 mm per day (average = 8.29 ± 0.11, n = 3) at 28°C. The colonies produced pale orange conidial masses and were fusiform with acute ends, hyaline, sometimes guttulate, 4.02 to 5.25 × 13.71 to 15.72 μm (average = 4.56 ± 0.31 × 14.87 ± 1.14 μm, n = 25). The morphological characteristics and measurements of this fungal isolate matched the previous descriptions of Colletotrichum fioriniae (Marcelino & Gouli) R.G. Shivas & Y.P. Tan (2). Meanwhile, these characterizations were further confirmed by analysis of the partial sequence of five genes: the internal transcribed spacer (ITS) of the ribosomal DNA, beta-tubulin (β-tub) gene, glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene, chitin synthase 3(CHS-1) gene, and actin (ACT) gene, with universal primers ITS4/ITS5, T1/βt2b, GDF1/GDR1, CHS1-79F/CHS1-354R, and ACT-512F/ACT-783R, respectively (1). BLAST of these DNA sequences using the nucleotide database of GenBank showed a high identify (ITS, 99%; β-tub, 99%; GAPDH, 99%; CHS-1, 99%; and ACT, 100%) with the previously deposited sequences of C. fioriniae (ITS, KF278459.1, NR111747.1; β-tub, AB744079.1, AB690809.1; GAPDH, KF944355.1, KF944354.1; CHS-1, JQ948987.1, JQ949005.1; and ACT, JQ949625.1, JQ949626.1). Koch's postulates were fulfilled by inoculating six healthy 1-year-old walnut trees in July 2014 with maximum and minimum temperatures of 33 and 26°C. The 6-mm mycelial plug, which was cut from the margin of a 5-day-old colony of the fungus on PDA, was placed onto each pin-wounded leaf, ensuring good contact between the mycelium and the wound. Non-colonized PDA plugs were placed onto pin-wounds as negative controls. Following inoculation, both inoculated and control plants were covered with plastic bags. Leaf spots, similar to those on naturally infected plants, were observed on the leaves inoculated with C. fioriniae within 5 days. No symptoms were observed on the negative control leaves. Finally, C. fioriniae was re-isolated from symptomatic leaves; in contrast, no fungus was isolated from the control, which confirmed Koch's postulates. To our knowledge, this is the first report of leaf disease on walnut caused by C. fioriniae. References: (1) L. Cai et al. Fungal Divers. 39:183, 2009. (2) R. G. Shivas and Y. P. Tan. Fungal Divers. 39:111, 2009.

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First Report of Fusarium oxysporum f. sp. lycopersici Race 3 Causing Fusarium Wilt on Tomato in Korea

Plant Disease ◽

10.1094/pdis-01-13-0073-pdn ◽

2013 ◽

Vol 97 (10) ◽

pp. 1377-1377 ◽

Cited By ~ 4

Author(s):

H.-W. Choi ◽

S. K. Hong ◽

Y. K. Lee ◽

H. S. Shim

Keyword(s):

Fusarium Wilt ◽

Dna Sequences ◽

Vascular Tissue ◽

Elongation Factor ◽

Morphological Characteristics ◽

Spore Suspension ◽

Vascular Bundles ◽

Laboratory Manual ◽

First Report ◽

Blastn Analysis

In July 2010, fusarium wilt symptoms of tomato (Lycopersicon esculentum Mill.) plants were found in two commercial greenhouses in the Damyang area of Korea. Approximately 1% of 7,000 to 8,000 tomato plants were wilted and chlorotic in each greenhouse. The vascular tissue was usually dark brown and the discoloration extended to the apex. Fragments (each 5 × 5 mm) of the symptomatic tissue were surface-sterilized with 1% NaOCl for 1 min, then rinsed twice in sterilized distilled water (SDW). The tissue pieces were placed on water agar and incubated at 25°C for 4 to 6 days. Nine Fusarium isolates were obtained from four diseased plants, of which three isolates were identified as F. oxysporum based on morphological characteristics on carnation leaf agar medium and DNA sequences of the translation elongation factor 1-alpha (EF-1α) gene (2). Macroconidia were mostly 3- to 5-septate, slightly curved, and 28 to 53 × 2.8 to 5.2 μm. Microconidia were abundant, borne in false heads or short monophialides, generally single-celled, oval to kidney shaped, and 5 to 23 × 3 to 5 μm. Chlamydospores were single or in short chains. The EF-1α gene was amplified from three isolates by PCR assay using ef1 and ef2 primers (3), and the amplification products were sequenced. The nucleotide sequences obtained were deposited in GenBank (Accession Nos. KC491844, KC491845, and KC491846). BLASTn analysis showed 99% homology with the EF-1α sequence of F. oxysporum f. sp. lycopersici MN-24 (HM057331). Pathogenicity tests and race determination were conducted using root-dip inoculation (4) on seedlings of tomato differential cultivars: Ponderosa (susceptible to all races), Momotaro (resistant to race 1), Walter (resistant to races 1 and 2), and I3R-1 (resistant to all races). A spore suspension was prepared by flooding 5-day-old cultures on potato dextrose agar with SDW. Plants at the first true-leaf stage were inoculated by dipping the roots in the spore suspension (1 × 106 conidia/ml) for 10 min. Inoculated plants were transplanted into pots containing sterilized soil, and maintained in the greenhouse at 25/20°C (12/12 h). Twenty-four seedlings of each cultivar were arranged into three replications. An equal number of plants of each cultivar dipped in water were used as control treatments. Disease reaction was evaluated 3 weeks after inoculation, using a disease index on a scale of 0 to 4 (0 = no symptoms, 1 = slightly swollen and/or bent hypocotyl, 2 = one or two brown vascular bundles in the hypocotyl, 3 = at least two brown vascular bundles and growth distortion, 4 = all vascular bundles brown and the plant either dead or very small and wilted). All isolates caused symptoms of fusarium wilt on all cultivars except I3R-1, indicating that the isolates were race 3. The pathogen was reisolated from the discolored vascular tissue of symptomatic plants. Control plants remained asymptomatic, and the pathogen was not reisolated from the vascular tissue. Fusarium wilt of tomato caused by isolates of F. oxysporum f. sp. lycopersici races 1 and 2 has been reported previously; however, race 3 has not been reported in Korea (1). To our knowledge, this is the first report of isolates of F. oxysporum f. sp. lycopersici race 3 on tomato in Korea. References: (1) O. S. Hur et al. Res. Plant Dis. 18:304, 2012 (in Korean). (2) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Publishing, Ames, IA, 2006. (3) K. O'Donnell et al. Proc. Nat. Acad. Sci. 95:2044, 1998. (4) M. Rep et al. Mol. Microbiol. 53:1373, 2004.

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First Report of Dieback on Hybrid Rhododendrons Caused by Neofusicoccum luteum and N. parvum in Spain

Plant Disease ◽

10.1094/pdis-10-10-0723 ◽

2011 ◽

Vol 95 (2) ◽

pp. 221-221 ◽

Cited By ~ 6

Author(s):

C. Pintos Varela ◽

V. Redondo Fernández ◽

J. P. Mansilla Vázquez ◽

O. Aguín Casal

Keyword(s):

Dna Sequences ◽

Uv Light ◽

Morphological Characteristics ◽

Phytophthora Ramorum ◽

Malt Extract ◽

First Report ◽

Agar Plug ◽

Thin Walled ◽

Neofusicoccum Luteum

During the conducting of Phytophthora ramorum surveys at Galician public parks (northwestern Spain) in 2010, established Rhododendron spp. plants were observed to be exhibiting leaf spots and necrosis, shoot blight, and cankers and dieback of shoots and branches. Branches and leaves of affected rhododendrons contained pseudothecia with bitunicate asci and hyaline pseudoparaphyses, and pycnidia were observed within the same stromatic masses. Symptomatic samples were disinfested in 0.5% sodium hypochlorite for 3 min. Tissues were cut from the margin of lesions, placed onto malt extract agar amended with streptomycin (25 μg ml–1), and incubated at 25°C in the dark. Cultures displaying morphological characteristics associated with Botryosphaeriaceae species were subcultured on 2% water agar with sterilized Pinus pinaster needles as a substrate and incubated at 25°C under near-UV light to encourage pycnidial production (1). Single conidial cultures gave rise to two distinct colonies on potato dextrose agar (PDA) at 25°C. In type 1, isolates produced a sparse, aerial mycelium and a characteristic yellow pigment that was more intense after 3 days, thereafter becoming violaceous and gradually turning dark gray. Growth occurred in the range of 4 to 38°C with an optimum at 29°C. Conidia were hyaline, fusiform, aseptate, thin walled, and averaged 21.1 (14.3 to 25.0) × 5.7 (4.3 to 6.8) μm with a length/width (L/W) ratio of 3.7 ± 0.4 (n = 100). On the basis of these characteristics, isolates were identified as Neofusicoccum luteum (1,3). Colonies of type 2 produced a dense, white-to-yellowish mycelium that rapidly became gray followed by marked diurnal zonation. Mycelial growth occurred in the range of 6 to 38°C with an optimum at 29 to 30°C. Conidia were hyaline, elliptical or fusiform, aseptate, thin walled, and averaging 18.3 (14.1 to 20.7) × 5.8 (4.6 to 7.0) μm with a L/W ratio of 3.2 ± 0.4 (n = 100). These isolates were identified as N. parvum (1,2). Identity was confirmed by DNA sequences analysis of internal transcribed spacer (ITS) regions. Comparison of the sequences of type 1 and 2 showed 100% homology with N. luteum and N. parvum (GenBank Accession Nos. EU673311 and GU251146, respectively). Representative sequences were deposited at GenBank (Accession Nos. HQ197352 and HQ197351). Pathogenicity of each isolate of N. luteum and N. parvum was confirmed by inoculating four 3-year-old Rhododendron spp. seedlings grown in pots. Shallow cuts were made in three branches of each plant. A colonized 6-mm agar plug, removed from the margin of an actively growing colony, was inserted beneath the flap and sealed with Parafilm. Four control seedlings received only sterile PDA agar plugs. Plants were maintained at 26°C and 70% humidity for 21 days. Inoculated plants began showing symptoms after 3 days. Necrosis progressed quickly and bidirectionally from the wound, resulting in death of leaves and wilting of shoots. N. luteum and N. parvum were reisolated from all inoculated plants but not from the controls. To our knowledge, this is the first report of N. luteum and N. parvum on Rhododendron spp. in Spain. References: (1) P. W. Crous et al. Stud. Mycol. 55:235, 2006. (2) S. R. Pennycook et al. Mycotaxon 24:445, 1985. (3) A .J. L. Phillips et al. Sydowia 54:59, 2002.

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First Report of Downy Mildew Caused by Peronospora sordida on Butterflybush (Buddleja stachyoides) in Brazil

Plant Disease ◽

10.1094/pdis-10-12-0965-pdn ◽

2013 ◽

Vol 97 (4) ◽

pp. 560-560

Author(s):

S. T. Albuquerque ◽

F. B. Rocha ◽

R. W. Barreto

Keyword(s):

Downy Mildew ◽

Phylogenetic Study ◽

Representative Specimen ◽

Podosphaera Xanthii ◽

First Report ◽

Blast Search ◽

Reproductive Structures ◽

Plant Press ◽

First Time ◽

The Relationship

Butterflybush (common name in Brazil, verbasco), Buddleja stachyoides Cham. & Schltdl. (Buddlejaceae), is an erect herb or small shrub, native to Brazil, that is listed both as a folk medicinal plant and as a pasture weed (4). In March 2012, a group of B. stachyoides plants growing in a pasture in Viçosa (state of Minas Gerais, Brazil), were found bearing typical downy mildew symptoms. The only pathogen reported associated with this plant species is Podosphaera xanthii (1) and because there is no record of downy mildew on members of Buddleja in Brazil, an investigation was carried out to clarify the pathogen identity. Diseased plants had lesions on living leaves that were vein-delimited, chlorotic, coalescing, and becoming necrotic adaxially and bearing downy mildew-like colonies over diseased tissues abaxially. The samples were dried in a plant press and a representative specimen was deposited in the local herbarium at the Universidade Federal de Viçosa (Accession No. VIC 31836). Reproductive structures were scraped from leaves with a scalpel and mounted in lactophenol. Preliminary observations indicated the pathogen as belonging to Peronospora (Peronosporaceae). The pathogen had the following morphology: Sporangiophores are 288 to 641 μm long, dichotomously branching up to seven times, hyaline, smooth, 5 to 16 μm wide at the trunk, branches 63 to 202 μm long; tips subacute, in pairs or rarely single, 5 to 19 μm long; sporangia subglobose to ellipsoidal, 12 to 22 × 11 to 17 μm, pale yellowish brown, non-papillate. Only one species of Peronospora is known to infect members of Buddleja, namely Peronospora hariotii Gäum. (1). Nevertheless, the pathogen on B. stachyoides has smaller sporangia as compared to those of P. hariotii (20 to 26 × 16 to 21 μm) (2) and it was closer to P. sordida (3). DNA of the pathogen from B. stachyoides was extracted and the cytochrome c oxidase subunit II (COX2) and internal transcribed spacer (ITS) regions were sequenced. Sequences were deposited in GenBank (COX2 as JX982637; ITS as JX982638). A BLAST search yielded 99% and 100% of maximum identity with P. sordida for COX2 and ITS, respectively. A more detailed phylogenetic study is necessary to clarify the relationship between P. sordida, P. hariotii, and related species causing downy mildew on closely related hosts. To our knowledge, this is the first report of P. sordida occurring on a member of the genus Buddleja. This is also the first time that P. sordida is reported from South America. References: (1) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , 19 October 2012. (2) S. M. Francis. C.M.I. Descr. Pathog. Fungi Bact. 767:1, 1983. (3) G. Hall. I.M.I. Descr. Fungi Bact. 1062:1, 1991. (4) K. G. Kissmann and D. Groth. Plantas Infestantes e Nocivas. São Paulo, BASF, 1997.

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First Report of Fusarium succisae Causing Flower Rot on Thread-leaf Coreopsis

Plant Disease ◽

10.1094/pdis-12-13-1205-pdn ◽

2014 ◽

Vol 98 (7) ◽

pp. 1002-1002 ◽

Cited By ~ 2

Author(s):

H.-W. Choi ◽

S. K. Hong ◽

Y. K. Lee ◽

W. G. Kim

Keyword(s):

Dna Sequences ◽

Production Control ◽

Fusarium Species ◽

Elongation Factor ◽

Morphological Characteristics ◽

Spore Suspension ◽

Sugar Solution ◽

Laboratory Manual ◽

First Report ◽

Blastn Analysis

In July 2010, flower rot of thread-leaf coreopsis (Coreopsis verticillata) was found in a garden in the Icheon City, Korea. The disease affected about 20 to 50% of a 100 m2 area. The disease was characterized by the appearance of pinkish mycelia on the stigmata and inflorescences of flowers. In some cases, flowers failed to bloom or turned brown before opening fully. Fragments (each 5 × 5 mm) of the symptomatic tissue were surface-sterilized with 1% NaOCl for 1 min, and then rinsed twice in sterilized distilled water. The tissue pieces were placed on water agar (WA) and incubated at 25°C for 4 to 6 days. Twenty-two isolates of Fusarium species were obtained from the diseased flowers. All isolates were identified as Fusarium succisae based on their morphological characteristics on carnation leaf agar (CLA) medium and DNA sequences of the translation elongation factor 1-alpha gene (1). Macroconidia and sporodochia were sparsely produced on CLA medium. Microconidia were abundant, borne in false heads, oval or allantoid and sometimes pyriform, and measured 4.2 to 13 × 2.2 to 5.4 μm. Chlamydospores were absent. The EF-1α gene was amplified from three isolates by PCR assay and the amplification products were sequenced (2). The nucleotide sequences obtained were deposited in GenBank with accession numbers KF514658, KF514659, and KF514660. BLASTn analysis showed 99% homology with the EF-1α sequence of F. succisae NRRL13613 (GenBank Accession No. AF160291). Pathogenicity tests were conducted with inoculation of flowers on Coreopsis verticillata. Spore suspension was prepared by flooding 7-day-old cultures on potato dextrose agar with sterilized 2% (w/v) sugar solution. When the plants started to have buds, the isolates were inoculated by placing one drop (20 μl) of spore suspension (1 × 106 spores ml−1) into the buds. Fifteen buds of the plants were arranged into three replications. The control was treated with sterilized 2% sugar solution. Inoculated plants were kept in a greenhouse at 25/20°C (12 h/12 h). Three weeks after inoculation, the symptoms were observed on buds with mycelial production. Control plants had no mycelia on buds. F. succisae was re-isolated from the inoculated flowers. To our knowledge, this is the first report of flower rot of thread-leaf coreopsis caused by F. succisae. References: (1) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Publishing, Ames, IA, 2006. (2) K. O'Donnell et al. Proc. Nat. Acad. Sci. 95:2044, 1998.

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First Report of Downy Mildew Caused by Peronospora belbahrii on Sweet Basil (Ocimum basilicum) in Cyprus

Plant Disease ◽

10.1094/pdis-07-13-0759-pdn ◽

2014 ◽

Vol 98 (2) ◽

pp. 283-283 ◽

Cited By ~ 5

Author(s):

L. Kanetis ◽

A. Vasiliou ◽

G. Neophytou ◽

S. Samouel ◽

D. Tsaltas

Keyword(s):

Downy Mildew ◽

Disease Incidence ◽

Infected Plant ◽

Morphological Characteristics ◽

Ocimum Basilicum ◽

First Report ◽

Consensus Sequences ◽

Sweet Basil ◽

Plastic Bags ◽

Necrotic Spots

Sweet basil (Ocimum basilicum L.) is an economically important annual aromatic plant, grown mostly for culinary use for both fresh and dry consumption and as a source of essential oil. In Cyprus, approximately 4 ha are grown annually, either in greenhouses as a year-round crop or in open fields from April to November, and the majority of the production is exported to the European market. During May 2012, a sweet basil cv. Genovese Gigante greenhouse operation in the area of Limassol was severely affected by a foliar disease, causing almost 100% crop losses. Within a few days, a similar, heavy disease incidence was also reported from a nearby greenhouse facility on the Genovese-type cultivars Superbo, Aroma 2, and Bonazza, as well as on Thai basil (O. basilicum var. thyrsiflorum). Successively, destructive hits of similar symptomatology have been reported from other areas and since then the disease appears to have been well-established in the country, causing major economic damages. It is also noteworthy to mention that in greenhouse infections the disease remains active even during winter, considering the mild environmental conditions and the monoculture fashion followed. Symptoms appeared on the leaves initially as interveinal, zonal, chlorotic lesions, followed by the appearance of a fuzzy, purplish sporulation on the abaxial side. Progressively, infected leaves curled and sporadic necrotic spots were evident and finally abscised. Light microscopic examination of infected samples revealed the presence of straight, hyaline sporangiophores (n = 15) typical of downy mildew, 210 to 590 μm long (mean = 350.7 μm; SD ± 117.5 μm) × 12 to 15 μm wide (mean = 13.1 μm; SD ± 1.4 μm). Sporangiophores were monopodially branched three to five times, terminating with curved branchlets bearing single sporangia at their tips. The sporangia (n = 25) were purplish-grey, ovoid to subglobose, and measured 32 to 22 μm in length (mean = 27.2 μm; SD ± 2.8 μm) and 30 to 10 μm in breadth (mean = 21.7 μm; SD ± 4.8 μm). Based on these morphological characteristics, the causal agent was identified as Peronospora belbahrii Thines (1,4). Furthermore, genomic DNA was extracted from infected plant tissue from eight different samples according to Dellaporta et al. (2). The complete ITS rDNA region was amplified and sequenced using primers ITS5 and ITS4 (3). Two of the consensus sequences were deposited in GenBank (Accession Nos. KF419289 and KF419290) and a BLAST analysis in the NCBI database revealed 99% similarity to all of the P. belbahrii sequences and other Peronospora sp. previously reported on sweet basil (Accession Nos. AY831719, DQ479408, FJ394336, and FJ436024). In a pathogenicity trial, five 40-day-old potted sweet basil plants were spray-inoculated with a sporangial suspension (1 × 105 sporangia/ml) until runoff, bagged for 24 h, and placed in a growth chamber at 18°C. Subsequently, the plastic bags were removed and the plants were kept at 22°C with a 16-h photoperiod and 80% relative humidity. Additionally, five plants were water-sprayed and served as controls. Typical downy mildew symptoms appeared 6 to 8 days after inoculation, while the uninoculated plants remained disease-free. To our knowledge, this is first report of downy mildew on sweet basil in Cyprus. References: (1) L. Belbahri et al. Mycol. Res. 109:1276, 2005. (2) S. L. Dellaporta et al. Plant Mol. Biol. Rep., 1:19, 1983. (3) G. Nagy and A. Horvat, Plant Dis. 93:1999, 2009. (4) M. Thines et al. Mycol. Res. 113:532, 2009.

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Diaporthe species causing stem gray blight of red-fleshed dragon fruit (Hylocereus polyrhizus) in Malaysia

Scientific Reports ◽

10.1038/s41598-021-83551-z ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Abd Rahim Huda-Shakirah ◽

Yee Jia Kee ◽

Kak Leong Wong ◽

Latiffah Zakaria ◽

Masratul Hawa Mohd

Keyword(s):

Dna Sequences ◽

Morphological Characteristics ◽

First Report ◽

Fungal Isolates ◽

Dragon Fruit ◽

Cameron Highlands ◽

Hylocereus Undatus ◽

Hylocereus Polyrhizus ◽

Β Tubulin

AbstractThis study aimed to characterize the new fungal disease on the stem of red-fleshed dragon fruit (Hylocereus polyrhizus) in Malaysia, which is known as gray blight through morphological, molecular and pathogenicity analyses. Nine fungal isolates were isolated from nine blighted stems of H. polyrhizus. Based on morphological characteristics, DNA sequences and phylogeny (ITS, TEF1-α, and β-tubulin), the fungal isolates were identified as Diaporthe arecae, D. eugeniae, D. hongkongensis, D. phaseolorum, and D. tectonendophytica. Six isolates recovered from the Cameron Highlands, Pahang belonged to D. eugeniae (DF1 and DF3), D. hongkongensis (DF9), D. phaseolorum (DF2 and DF12), and D. tectonendophytica (DF7), whereas three isolates from Bukit Kor, Terengganu were recognized as D. arecae (DFP3), D. eugeniae (DFP4), and D. tectonendophytica (DFP2). Diaporthe eugeniae and D. tectonendophytica were found in both Pahang and Terengganu, D. phaseolorum and D. hongkongensis in Pahang, whereas D. arecae only in Terengganu. The role of the Diaporthe isolates in causing stem gray blight of H. polyrhizus was confirmed. To date, only D. phaseolorum has been previously reported on Hylocereus undatus. This is the first report on D. arecae, D. eugeniae, D. hongkongensis, D. phaseolorum, and D. tectonendophytica causing stem gray blight of H. polyrhizus worldwide.

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First Report of Root Rot Caused by Fusarium solani on Benincasa hispida in the United States

Plant Disease ◽

10.1094/pdis-06-11-0494 ◽

2012 ◽

Vol 96 (2) ◽

pp. 294-294 ◽

Cited By ~ 2

Author(s):

P. Ji ◽

J. Yin ◽

K. L. Jackson

Keyword(s):

United States ◽

Dna Sequences ◽

Root Rot ◽

Morphological Characteristics ◽

The United States ◽

First Report ◽

Benincasa Hispida ◽

Field Samples ◽

Vegetable Farm ◽

Wax Gourd

Root rot was observed on wax gourd (Benincasa hispida (Thunb.) Cogn.) cv. Black Giant in August 2010 in a commercial vegetable farm in southern Georgia. Approximately 5% of the plants were affected and infected roots turned light to dark brown with partial or entire roots affected and the lower leaves became wilted. Symptomatic roots from six plants were surface sterilized with 0.6% sodium hypochlorite and plated on potato dextrose agar (PDA) medium. Pure cultures had white mycelia and spore masses and were obtained from all six plants by subculturing hyphal tips onto PDA. One- to two-celled, oval- to kidney-shaped microconidia and cylindrical macroconidia with two or three cells plus apical and basal cell were produced, which averaged 12.5 × 4 μm and 28 × 4.5 μm, respectively. Microconidia were abundant and macroconidia were sparse on PDA. Single-spore isolates were obtained and identified as a Fusarium sp. by PCR analysis with primers ITS-Fu-f and ITS-Fu-r (1). Genomic DNA of two isolates obtained from different plants was extracted and a portion of the translation elongation factor 1-α (TEF) gene of the isolates was amplified and sequenced (3). When compared with sequences available in the GenBank database, DNA sequences of the two isolates (GenBank Accession No. JF928376) shared 100% sequence identity with F. solani strain FRC S1734 (GenBank Accession No. DQ247527). The fungus was identified as F. solani (Mart.) Sacc. based on molecular analysis and morphological characteristics (2). Oat grains were separately infected with two isolates, BG2a and BG6, and used to inoculate healthy, 3-week-old wax gourd seedlings (cv. Black Giant) under greenhouse conditions (14-h photoperiod, 24 to 30°C). Each seedling was grown in a 10-cm pot containing a commercial potting mix, and five healthy plants were inoculated with each isolate by placing 15 infected oat grains around each plant at a depth of 5 cm in the soil. Five plants treated with noninfected oat grains served as controls. Symptoms identical to those on field samples developed on all inoculated plants 3 weeks after inoculation but not on the control plants. F. solani was reisolated from inoculated symptomatic plants and the identity was confirmed, which completed Koch's postulates. The experiment was repeated one more time under similar conditions. To our knowledge, this is the first report of root rot caused by F. solani on wax gourd in the United States. Wax gourd is an important specialty crop in the southeastern United States and the occurrence of this disease needs to be taken into account in wax gourd production. References: (1) K. A. Abd-Elsalam et al. Afr. J. Biotechnol. 2:82, 2003. (2) C. Booth. Fusarium Laboratory Guide to the Identification of the Major Species. CMI, Kew, England, 1977. (3) D. M. Geiser et al. Eur. J. Plant Pathol. 110:473, 2004.

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