scholarly journals First Report of Crown Rot of Strawberry Caused by Macrophomina phaseolina in Chile

Plant Disease ◽  
2013 ◽  
Vol 97 (7) ◽  
pp. 996-996 ◽  
Author(s):  
S. Sánchez ◽  
M. Gambardella ◽  
J. L. Henríquez ◽  
I. Díaz
Keyword(s):  
Cross Sections ◽  
Vascular Ring ◽  
Aerial Mycelium ◽  
Macrophomina Phaseolina ◽  
The United States ◽  
Causal Agent ◽  
Crown Rot ◽  
First Report ◽  
San Pedro ◽  
Pure Cultures

In recent years, an increase of collapsed and dead strawberry plants has been observed in several fields in central Chile, specifically in San Pedro, Melipilla, an important area for strawberry cultivation in the country. To determine the causal agent of the disease and the extent of the problem, 25 sample sites of 1 ha each, distributed in different San Pedro zones, were surveyed at the end of the 2011 season (from December 2010 to February 2011). Cross sections of the crowns of symptomatic strawberry plants showed necrotic tissue and brown-red to dark brown areas on the vascular ring. Samples of the affected crowns were superficially disinfested and plated on potato dextrose agar with 200 μg/ml of streptomycin sulfate. Dark gray colonies were observed after 7 days of incubation at 24°C. Pure cultures of the pathogen showed aerial mycelium and abundant dark oblong sclerotia. Fifty sclerotia were measured, averaging 120 × 74 μm. Twenty-one isolates were identified molecularly utilizing the species specific primers MpKFI and MpKRI (2) that yielded a 350-bp fragment. The amplified DNA fragments were sequenced and BLAST analysis showed a 99% nucleotide sequence identity with Macrophomina phaseolina (GeneBank Accession No JX535007.1). Both morphological and molecular analyses confirmed that the isolated species corresponded to M. phaseolina, causal agent of crown and root rot in strawberry. Four representative isolates were selected to conduct pathogenicity tests. Inoculum was prepared by incubating the pathogen for 28 days at 20°C in sterilized oat seeds. Pots of 1.5 liters were filled with a mixed substrate of peat and perlite (2:1), amended with inoculated oats at 9 g per liter of substrate. ‘Camarosa’ strawberry plants were planted and grown in a glasshouse for 1 month. Six replicated plants per isolate and six plants growing on non-inoculated substrate were left as controls. Ninety-five percent of the inoculated plants showed wilt and collapse symptoms 22 days after transplant, whereas no symptoms were observed in the control plants. M. phaseolina was reisolated from the crowns of symptomatic plants, fulfilling Koch's postulates. The pathogen was isolated from symptomatic strawberry plants in 14 of the 25 sampled sites. Although M. phaseolina was described previously on other crops in Chile, to our knowledge, this is the first report of M. phaseolina causing crown rot of strawberry. The disease has been recently reported in Spain, the United States, and Argentina (1,3,4). References: (1) M. Avilés et al. Plant Pathol. 57:382, 2008. (2) B. Babu et al. Mycologia 99:797, 2007. (3) O. Baino et al. Plant Dis. 95:1477, 2011. (4) S. Koike. Plant Dis. 92:1253, 2008.

scholarly journals First Report of Macrophomina phaseolina Causing a Crown Rot of Strawberry in Florida

Plant Disease ◽  
2005 ◽  
Vol 89 (4) ◽  
pp. 434-434 ◽  
Author(s):  
J. Mertely ◽  
T. Seijo ◽  
N. Peres
Keyword(s):  
Methyl Bromide ◽  
Block Design ◽  
Vascular Ring ◽  
Macrophomina Phaseolina ◽  
Crown Rot ◽  
American Phytopathological Society ◽  
Charcoal Rot ◽  
Isolation Medium ◽  
Potato Dextrose Broth ◽  
First Report

Strawberry (Fragaria × ananassa Duchesne) is produced as an annual winter crop in raised, plastic-mulched beds on 2,800 ha in west central Florida. In December 2001, a grower submitted collapsed and dying strawberry plants from a commercial field to the University of Florida in Dover. The cut crowns of affected plants revealed dark brown necrotic areas on the margins and along the woody vascular ring. Macrophomina phaseolina was isolated from pieces of infected tissue cut aseptically from the crowns and placed on a medium containing 12 g of Difco potato dextrose broth, 17 g of Bacto agar, 250 mg of ampicillin, and 100 mg of streptomycin sulfate per liter of water. The fungus produced numerous, dark, oblong sclerotia in the isolation medium after 4 to 5 days incubation at 24°C under constant fluorescent lighting. In 10-day-old cultures, sclerotia ranged in size from 55 to 190 μm long by 50 to 135 μm wide (average 105 × 74 μm). Ostiolate pycnidia bearing relatively large, broadly ellipsoidal, hyaline conidia occasionally developed on the host tissue after 8 to 10 days of incubation (2). During the 2003-2004 season, M. phaseolina was isolated from dying strawberry plants taken from the original field and two additional farms. Affected plants were often found along field margins or other areas inadequately fumigated with methyl bromide. Two single-spore isolates from different fields were tested for pathogenicity on nursery runner plants (cv. Strawberry Festival) grown for 4 weeks in the greenhouse on artificial potting soil. The fungal isolates were grown on corn meal agar at 24°C for 4 days and allowed to colonize sterile wooden toothpicks placed on the medium for an additional 5 days. Prior to use, the toothpicks were sterilized by autoclaving twice in deionized water and a third time in V8 juice. Six plants were inoculated with each isolate by inserting a colonized toothpick into each crown. Sterile, V8-infused toothpicks were inserted into the crowns of corresponding control plants. The plants were incubated in a greenhouse in a randomized complete block design with two replicates of three plants each. After 3 days, 33 to 100% of the inoculated plants developed wilting in one or more leaves. All inoculated plants collapsed or died within 2 weeks of inoculation, while the control plants remained healthy during the observation period. The pathogen was readily reisolated from inoculated plants. Charcoal rot disease caused by M. phaseolina has been reported on strawberry in France, India, and Illinois (2,3). To our knowledge, this is the first report from Florida. M. phaseolina may be an emerging threat as the Florida strawberry industry transitions from methyl bromide to other fumigants in 2005. References: (1) J. Maas. Macrophomina leaf blight and dry crown rot. Page 26 in: Compendium of Strawberry Diseases. 2nd ed. J. L. Maas, ed. The American Phytopathological Society, St. Paul, MN, 1998. (2) G. S. Smith and T. D. Wyllie. Charcoal rot. Pages 29–31 in: Compendium of Soybean Diseases. G. L. Hartman et al., eds. 4th ed. The American Phytopathological Society, St. Paul, MN. 1999. (3) B. Tweedy et al. Plant Dis. Rep. 42:107, 1958.

scholarly journals First Report of Crown and Root Rot in Strawberry Caused by Macrophomina phaseolina in Israel

Plant Disease ◽  
2005 ◽  
Vol 89 (9) ◽  
pp. 1014-1014 ◽  
Author(s):  
A. Zveibil ◽  
S. Freeman
Keyword(s):  
Root Rot ◽  
Fungal Pathogens ◽  
Macrophomina Phaseolina ◽  
Crown Rot ◽  
Plant Mortality ◽  
Charcoal Rot ◽  
First Report ◽  
Production Stages ◽  
Pure Cultures ◽  
Pathogenicity Assay

A phenomenon of wilting in strawberry (Fragaria × ananassa Duchesne) transplants, cultivated for annual winter production, was observed on several cultivars at 14 farmers' plots in nine growing regions in Israel during September and October 2004. Typical ‘charcoal rot’ symptoms included necrotic root and crown rot accompanied by plant wilting and chlorosis of leaves (1). Pure cultures of Macrophomina phaseolina were isolated from affected roots and crowns of plants (1) when incubated at 25°C in the dark on potato dextrose agar (PDA) (Difco Laboratories, Sparks, MD) medium containing 250 mg/l of chloramphenicol. Dark, oblong sclerotia averaging 40 μm wide by 200 μm long were observed in the infected root tissue and in culture 7 to 10 days after isolation (2). Twenty-two single sclerotium isolates were recovered from five infected cultivars (Yuval, Herut, Tamar, Hadas, and Malach) and three representative isolates were used in two pathogenicity assays. Inoculum of M. phaseolina was produced by blending 3-week-old cultures on PDA plates (9 cm diameter) in 100 ml of sterile distilled water, filtering the suspension through eight layers of gauze, and adjusting the concentration to 105 sclerotia per ml. In the first pathogenicity assay, each of the three isolates was inoculated on five plants (cv. Malach). Plants were produced from nursery runners and potted in a soilless coconut and styrofoam (3:1 vol/vol) medium, 1 liter per pot. Each plant was inoculated by pouring 50 ml of sterile water containing 105 sclerotia per ml per pot. Plants were incubated at 30°C with 12-h day/night conditions and watered with 100 ml every 3 to 7 days. Five noninoculated control plants were included. Necrosis at the base of petioles and chlorosis of leaves, followed by initial wilting of leaves, were observed after 2 weeks on inoculated plants. Plant mortality was first recorded approximately 5 weeks after inoculation and 100% mortality was recorded 10 weeks postinoculation. In the second pathogenicity assay, the same three isolates were used to inoculate four plants each of two different cultivars (Malach and Hadas) as described previously. Identical disease symptoms, as described previously, were observed 17 days after inoculation. Initial plant mortality was observed approximately 6 weeks postinoculation. In both pathogenicity assays, M. phaseolina was readily reisolated on amended PDA from all symptomatic and dead plants, which successfully completed Koch's postulates. Noninoculated control plants remained healthy. Although M. phaseolina has been reported in other crops in Israel, to our knowledge, this is the first report of the pathogen on strawberry in our country. This study suggests that the current soil fumigation regimen for control of fungal pathogens such as M. phaseolina, utilizing alternatives to methyl bromide which is currently being phased out in Israel, may not be adequate to maintain healthy strawberry material at all production stages. A similar observation was recently reported in Florida (2). Charcoal rot of strawberry has also been recorded on strawberry in France, India, and Egypt (1). References: (1) J. Maas. Macrophomina leaf blight and dry crown rot and Macro-phomina root rot and charcoal rot. Pages 26 and 59 in: Compendium of Strawberry Diseases. 2nd ed. J. L. Maas, ed. The American Phytopathological Society, St. Paul, MN, 1998. (2) J. Mertely et al. Plant Dis. 89:434, 2005.

scholarly journals First Report of Cowpea aphid-borne mosaic virus on Sesame in Paraguay

Plant Disease ◽  
2011 ◽  
Vol 95 (5) ◽  
pp. 613-613 ◽  
Author(s):  
L. Gonzalez Segnana ◽  
M. Ramirez de Lopez ◽  
A. P. O. A. Mello ◽  
J. A. M. Rezende ◽  
E. W. Kitajima
Keyword(s):  
Electron Microscopy ◽  
Nucleotide Sequence ◽  
Mosaic Virus ◽  
The United States ◽  
Causal Agent ◽  
Nucleotide Sequence Analysis ◽  
Type I ◽  
First Report ◽  
San Pedro ◽  
Cowpea Aphid

Sesame (Sesamum indicum L.) is cultivated mainly in the central region of the Departamento de San Pedro in Paraguay from October to February and the seed are exported to Asia. The crop is grown on 100,000 ha annually and Escoba blanca is the most common cultivar. The crop plays an important socioeconomical role since it is cultivated mostly by small growers. A disease characterized by yellowing and curling down leaves and shortening of the internodes has been observed in almost all sesame-growing areas. It is referred to locally as “ka'are” because the affected sesame plant resembles Chenopodium ambrosioides L. This disease occurred occasionally and was of marginal importance prior to 2005, but during the last five growing seasons the disease incidence has increased substantially, with some growers losing the entire crop. To determine the causal agent, symptomatic leaf samples were collected from five commercial fields near Colonia San Pedro and Choré, Departamento San Pedro in December 2009. Preliminary transmission electron microscopy (TEM; Zeiss EM900) of extracts from symptomatic leaves revealed the presence of elongated flexible particles resembling a potyvirus. Mechanical transmission assays resulted in chlorotic local lesions on C. quinoa and C. amaranticolor, mosaic on Vigna unguiculata and Nicotiana benthamiana, and symptoms on sesame that are similar to those observed in the field. The disease could also be reproduced in sesame by aphid (Myzus persicae) transmission in a nonpersistent manner. TEM examination of leaf sections of these naturally or experimentally infected plants showed the presence of the type I cylindrical inclusions and masses of filamentous particles. Leaf extracts of naturally or experimentally infected sesame and test plants were positive for Cowpea aphid-borne mosaic virus (CABMV) on the basis of plate-trapped antigen (PTA)-ELISA. CABMV as the causal agent of “ka'are” disease of sesame in Paraguay was further confirmed by analyzing part of the nucleotide sequence of CABMV coat protein and 3′ nontranslated region that were obtained directly from reverse transcription-PCR product amplified with PV1-antisense primer (5′-gatttaggtgacactatagt17-3′) and WCIEN-sense primer (5′-atggtttggtgyatygaraat-3′) (1,2). Comparisons of the 676-bp nucleotide sequence of two sesame virus isolates (GenBank Accession Nos. HQ336402 and HQ336403) revealed 92% identity with the corresponding nucleotide sequence of CABMV available in the GenBank (Accession No. AF348210). Thus, all the assays indicated that the “ka'are” disease of sesame in Paraguay is caused by an isolate of CABMV. Several cowpea fields, nearby sesame diseased crops, also contained plants exhibiting mosaic symptoms. Transmission assays, electron microscopy, PTA-ELISA, and nucleotide sequence analysis indicated that they were also infected by CABMV and may play an important role in the epidemiology of this disease on sesame. CABMV isolates from passion fruit and cowpea from Brazil were mechanically transmitted to sesame but induced milder symptoms. CABMV-infected sesame was described in the United States (3), but to our knowledge, this is the first report of a severe disease on sesame caused by this virus in Paraguay. References: (1) A. Gibbs and A. Mackenzie. J. Virol. Methods 63:9, 1997. (2) L. D. C. Mota et al. Plant Pathol. 53:368, 2004. (3) H. R. Pappu et al. Arch. Virol. 142:1919, 1997.

scholarly journals First Report of Pilidium concavum on Paeonia suffruticosa in China

Plant Disease ◽  
2010 ◽  
Vol 94 (2) ◽  
pp. 271-271 ◽  
Author(s):  
Y. B. Duan ◽  
Y. B. Kang ◽  
Z. Z. Yu
Keyword(s):  
Aerial Mycelium ◽  
Causal Agent ◽  
Its2 Region ◽  
Paeonia Suffruticosa ◽  
Humid Atmosphere ◽  
First Report ◽  
Leaf Spots ◽  
Initial Symptoms ◽  
Perennial Shrub ◽  
Pure Cultures

Paeonia suffruticosa Andrews, a deciduous perennial shrub, is known for its beautiful and charming flowers. It is regarded as the flower symbol of China and cultivated throughout the country. Since 2006, large, brown necrotic spots have been observed on numerous P. suffruticosa plants in gardens in Luoyang, China. Spots appeared each year and were observed on more than 50% of the plants, sometimes affecting more than half of the leaf. Initial symptoms appeared as small, round, water-soaked lesions in the middle or on the margin of leaves. These areas enlarged up to 1 to 3 cm in diameter and were circular or irregular, brown to dark brown, and pale brown on the margins. In a humid atmosphere, black, sessile, discoid conidiomata developed on the spots and exuded a pink spore mass that turned brown with age. Conidiophores were hyaline, unicellular, cylindrical, and fusiform and 5.0 to 8.0 μm long and 1.4 to 2.0 μm wide. Pure cultures were obtained by plating the spores on potato dextrose agar (PDA) medium. In culture, the fungus produced a gray-to-brown colony with whitish aerial mycelium. The morphology and size of conidia were comparable with previous descriptions of Pilidium concavum (Desm.) Höhn. (1). The ITS1-5.8S-ITS2 region of the isolate was amplified by PCR with primers ITS1 and ITS4 and sequenced. The 472-nt sequence was 100% identical to that of the Pilidium concavum specimen voucher BPI 1107275 (GenBank Accession No. AY487094). To validate Koch's postulates, pathogenicity was tested by inoculating 10 leaves of P. suffruticosa with mycelia plugs from a colony growing on PDA; leaves inoculated with the plugs of PDA medium only served as the control. Leaves were covered with plastic for 24 h to maintain high relative humidity. After 7 days, 100% of the mycelium-inoculated leaves showed symptoms identical to those observed on P. suffruticosa leaves affected in the field, whereas all leaves inoculated with PDA medium only remained free of symptoms. Reisolation of the fungus from leaf lesions confirmed that the causal agent was Pilidium concavum. Thus, we concluded that Pilidium concavum is the causal agent of leaf spots of P. suffruticosa. This disease has been reported to be frequently occurring on P. suffruticosa stems imported from Japan (1), but to our knowledge, this is the first report of Pilidium concavum on P. suffruticosa in China. References: (1) M. E. Palm. Mycologia 83:787, 1991.

scholarly journals First Report of Macrophomina phaseolina Causing Trunk and Cordon Canker Disease of Grapevine in the United States

Plant Disease ◽  
2019 ◽  
Vol 103 (3) ◽  
pp. 579-579 ◽  
Author(s):  
M. T. Nouri ◽  
G. Zhuang ◽  
C. M. Culumber ◽  
F. P. Trouillas
Keyword(s):  
United States ◽  
Macrophomina Phaseolina ◽  
The United States ◽  
Canker Disease ◽  
First Report

scholarly journals First report of Meloidogyne javanica pathogenic on hybrid lavender (Lavandula ×intermedia) in the United States

Plant Disease ◽  
2021 ◽  
Author(s):  
Samara A. Oliveira ◽  
Daniel M. Dlugos ◽  
Paula Agudelo ◽  
Steven N. Jeffers
Keyword(s):  
South Carolina ◽  
Sandy Loam ◽  
Meloidogyne Javanica ◽  
The United States ◽  
Crown Rot ◽  
Cultivated Plants ◽  
Broad Host Range ◽  
First Report ◽  
Tomato Roots ◽  
The Usa

Root-knot nematodes (RKNs), Meloidogyne spp., are some of the most economically important pathogens of cultivated plants. Meloidogyne javanica is one of the most destructive RKN species and is well known for its broad host range and the severe damage it causes to plant roots (Perry et al. 2009). In Feb 2018, four mature dead and dying hybrid lavender plants (Lavandula ×intermedia ‘Phenomenal’) were collected in Edgefield County, South Carolina, and suspected of having Phytophthora root and crown rot (Dlugos and Jeffers 2018). Greenhouse-grown plants had been transplanted in Dec 2016 and Jan 2017 into a sandy loam soil on a site that had been fallow or in pasture for over 30 years. Some plants began to turn gray and die in summer 2017, and approximately 40% of 1230 plants were symptomatic or dead by Feb 2018. Phytophthora spp. were not isolated from the collected plants but were isolated from plants collected on subsequent visits. Instead, all four plants had small, smooth galls on the roots. Lavender roots were examined microscopically (30-70×), and egg masses of RKNs were observed on the galls. Mature, sedentary RKN females were handpicked from galled roots, and perineal patterns of 10 specimens were examined and identified as M. javanica. Juveniles and eggs were extracted from lavender roots by the method of Coolen and D’herde (1972). To confirm species identification, DNA was extracted from 10 individual juveniles, and a PCR assay was conducted using species-specific primers for M. javanica, Fjav/Rjav (Zijlstra et al. 2000). A single amplicon was produced with the expected size of approximately 720 bp, which confirmed identity as M. javanica. To determine pathogenicity, M. javanica from lavender roots were inoculated onto susceptible tomato plants for multiplication, and severe gall symptoms occurred on tomato roots 60 days later. Nematodes were extracted from tomato roots and inoculated onto healthy, rooted cuttings of ‘Phenomenal’ lavender plants growing in pots of soilless medium in a greenhouse. Plants were inoculated with 0, 1000, 2000, 5000, or 10000 eggs and juveniles of M. javanica. Five single-plant replicates were used for each treatment, and plants were randomized on a greenhouse bench. Plants were assessed 60 days after inoculation, and nematodes were extracted from roots and counted. The reproduction factor was 0, 43.8, 40.9, 9.1, 7.7, and 2.6 for initial nematode populations 0, 1000, 2000, 5000, and 10000, respectively, which confirmed pathogenicity (Hussey and Janssen 2002). Meloidogyne javanica also was recovered in Mar 2018 from galled roots on a ‘Munstead’ (L. angustifolia) lavender plant from Kentucky (provided by the Univ. of Kentucky Plant Disease Diagnostic Laboratories), and an unidentified species of Meloidogyne was isolated in Aug 2020 from a ‘Phenomenal’ plant grown in Florida. COI mtDNA sequences from the SC (MZ542457) and KY (MZ542458) populations were submitted to Genbank. M. javanica previously was found associated with field-grown lavender (hybrid and L. angustifolia) in Brazil, but pathogenicity was not studied (Pauletti and Echeverrigaray 2002). To our knowledge, this is the first report of M. javanica pathogenic to L. ×intermedia in the USA, and the first time RKNs have been proven to be pathogenic to Lavandula spp. following Koch’s Postulates. Further studies are needed to investigate the geographic distribution of M. javanica on lavender and the potential threat this nematode poses to lavender production in the USA.

scholarly journals First Report of Choke Disease Caused by Epichloë typhina on Orchardgrass (Dactylis glomerata) in China

Plant Disease ◽  
2009 ◽  
Vol 93 (6) ◽  
pp. 673-673 ◽  
Author(s):  
C. J. Li ◽  
Z. F. Wang ◽  
N. Chen ◽  
Z. B. Nan
Keyword(s):  
Dactylis Glomerata ◽  
The United States ◽  
Leaf Sheath ◽  
Climatic Conditions ◽  
Disease Spread ◽  
Willamette Valley ◽  
First Report ◽  
Epichloë Typhina ◽  
Pure Cultures ◽  
Choke Disease

Orchardgrass or cocksfoot (Dactylis glomerata L.) has been widely cultivated as a forage crop in many provinces of China (1). It is also a native perennial forage grass, which grows at the edge of forests, shrubs, and mountainous grasslands in Xinjiang and Sichuan (2). In September of 2007, signs of choke disease on orchardgrass were observed in a native grassland under birch woodland near Altai City, Xinjiang, China. Stromata, which formed on culms of diseased grass, enclosing the inflorescence and leaf sheath, were 4.5 to 5.5 mm long, smooth or wrinkled, white and later becoming yellowish or yellow, tuberculate, dry, and covered with perithecia. Inflorescences surrounded by fungal stromata were choked and failed to mature, thus restricting seed production. Pure cultures were obtained by directly scraping stromata from the surface and incubating it on antibiotic potato dextrose agar (PDA). The colonies were cottony, white on the upper surface, and white to yellow on the reverse. The growth rate was 13 to 21 mm per week at 25°C on PDA. Conidia were hyaline, lunate to reniform, and measured 4.1 ± 0.5 × 2.2 ± 0.5 μm. They accumulated in small globose heads at the tips of conidiogenous cells and were produced singly on conidiophores of 13 to 33 μm long and 2.7 to 4.1 μm wide at the base. Internal transcribed spacer (ITS) sequence by BLAST search had 99% similarity with an Epichloë typhina isolate of orchardgrass in Spain (GenBank Accession No. AM262420.1). Cultural characteristics, microscopic examination, and phylogenetic analysis showed that this choke disease on D. glomerata was caused by the fungus E. typhina (Pers.) Tul. & C. Tul. as described by White (4). To our knowledge, this is the first report of E. typhina causing choke disease on orchardgrass in China. The pathogen has been identified in France, England, Germany, Sweden, Switzerland, and the United States (3,4) with the same symptoms as those reported here. In 1997, choke disease was found in 70% of the fields in the Willamette Valley of Oregon, with disease incidences ranging from 0.05 to 28%. It was predicted to increase and spread under the prevailing climatic conditions (3). This new disease report is to provide observational and diagnostic information to help with recognition and prevention of disease spread in orchardgrass cultivation regions of China. References: (1) X. R. Chao et al. Shandong Agric. Sci. 1:7, 2005. (2) S. X. Jia, ed. China Forage Plant Flora. China Agriculture Press, Beijing, 1987. (3) W. F. Pfender and S. C. Alderman. Plant Dis. 83:754, 1999. (4) J. W. White. Mycologia 85:444, 1993.

scholarly journals First Report of Root and Stem Rot Caused by Phytophthora nicotianae on Peperomia tetraphylla in China

Plant Disease ◽  
2010 ◽  
Vol 94 (9) ◽  
pp. 1171-1171 ◽  
Author(s):  
D. X. Zeng ◽  
X. L. Wu ◽  
Y. H. Li
Keyword(s):  
Southern China ◽  
Aerial Mycelium ◽  
Its Region ◽  
Soil Extract ◽  
Phytophthora Nicotianae ◽  
Stem Rot ◽  
Molecular Characteristics ◽  
Its Sequence ◽  
First Report ◽  
Pure Cultures

Peperomia tetraphylla, an evergreen herb, is becoming increasingly popular as a potted ornamental plant in southern China. In the summer of 2008, in some commercial flower nurseries in Shenzhen, Guangdong Province, P. tetraphylla showed extensive black stem and root rot, with leaves dropping from the rotten stem. Small pieces (approximately 3 mm2) of stems and leaves were excised from the margins of the black lesions, surface disinfected for 30 s to 1 min in 0.1% HgCl2, plated onto potato dextrose agar (PDA), and incubated at 25°C in the dark. All the plated samples yielded Phytophthora, and microscopic examination of pure cultures grown on PDA plates showed arachnoid colonies with abundant aerial mycelium, chlamydospores, and a few sporangia. Numerous sporangia were formed in sterile soil extract. Sporangia were ovoid or obpyriform, noncaducous, with prominent solitary papillae, and measured 31 to 52 μm (average 38 μm) × 21 to 34 μm (average 27 μm). Chlamydospores were spherical and 21 to 34 μm in diameter (average 28 μm). The internal transcribed spacer (ITS) region of rDNA of a single isolate was amplified using primers ITS4/ITS5 and sequenced (2). The ITS sequence, when submitted for a BLAST search in the NCBI database, showed 100% homology with the sequences of two reference isolates of Phytophthora nicotianae (Accession Nos. AY833526 and EU433396) and the consensus ITS sequence was deposited in the NCBI as Accession No. GQ499373. The isolate was identified as Phytophthora nicotianae on the basis of morphological and molecular characteristics (1). Pathogenicity of the isolate was confirmed by inoculating 1-year-old plants of P. tetraphylla growing in pots. The isolate was grown for 7 days on PDA plates and mycelial plugs, 5 mm in diameter and taken from the advancing margins of the colonies, were buried approximately 1 cm deep near the base of the stem in such a way that the mycelium on the plugs was in contact with the surface of the stem, which had been wiped earlier with 70% ethanol and gently wounded with a needle. Plants treated the same way but inoculated with sterile PDA plugs served as control plants. Three plants in each pot were inoculated and there were five replications each for the treatment and the control. All plants were kept in a greenhouse at 22 to 32°C. After 6 to 7 days, the inoculated plants showed black lesions around the mycelial plugs; symptoms of root and stem rot developed rapidly thereafter and the plants collapsed within 2 weeks. All symptoms on the inoculated plants were identical to those observed in naturally diseased plants, whereas the control plants remained healthy. The same fungus was consistently reisolated from the inoculated plants. To our knowledge, this is the first report of Phytophthora nicotianae on P. tetraphylla in China. References: (1) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996. (2) J. B. Ristaino et al. Appl. Environ. Microbiol. 64:948, 1998.

scholarly journals First Report of Phytophthora citrophthora on Penstemon barbatus in Italy

Plant Disease ◽  
2006 ◽  
Vol 90 (9) ◽  
pp. 1260-1260 ◽  
Author(s):  
A. Garibaldi ◽  
D. Bertetti ◽  
D. Minerdi ◽  
M. L. Gullino
Keyword(s):  
Its Region ◽  
The United States ◽  
Phytophthora Species ◽  
Crown Rot ◽  
Pathogenicity Test ◽  
Phytophthora Citrophthora ◽  
First Report ◽  
Blastn Analysis ◽  
Root And Crown Rot ◽  
Pathogenicity Tests

Penstemon barbatus (Cav.) Roth (synonym Chelone barbata), used in parks and gardens and sometimes grown in pots, is a plant belonging to the Scrophulariaceae family. During the summers of 2004 and 2005, symptoms of a root rot were observed in some private gardens located in Biella Province (northern Italy). The first symptoms resulted in stunting, leaf discoloration followed by wilt, root and crown rot, and eventually, plant death. The diseased tissue was disinfested for 1 min in 1% NaOCl and plated on a semiselective medium for Oomycetes (4). The microorganism consistently isolated from infected tissues, grown on V8 agar at 22°C, produced hyphae with a diameter ranging from 4.7 to 5.2 μm. Sporangia were papillate, hyaline, measuring 43.3 to 54.4 × 26.7 to 27.7 μm (average 47.8 × 27.4 μm). The papilla measured from 8.8 to 10.9 μm. These characteristics were indicative of a Phytophthora species. The ITS region (internal transcribed spacer) of rDNA was amplified using primers ITS4/ITS6 (3) and sequenced. BLASTn analysis (1) of the 800 bp obtained showed a 100% homology with Phytophthora citrophthora (R. & E. Sm.) Leonian. The nucleotide sequence has been assigned GenBank Accession No. DQ384611. For pathogenicity tests, the inoculum of P. citrophthora was prepared by growing the pathogen on autoclaved wheat and hemp kernels (2:1) at 25°C for 20 days. Healthy plants of P. barbatus cv. Nano Rondo, 6 months old, were grown in 3-liter pots (one plant per pot) using a steam disinfested substrate (peat/pomix/pine bark/clay 5:2:2:1) in which 200 g of kernels per liter of substrate were mixed. Noninoculated plants served as control treatments. Three replicates were used. Plants were maintained at 15 to 20°C in a glasshouse. The first symptoms, similar to those observed in the gardens, developed 21 days after inoculation, and P. citrophthora was consistently reisolated from infected plants. Noninoculated plants remained healthy. The pathogenicity test was carried out twice with similar results. A nonspecified root and crown rot of Penstemon spp. has been reported in the United States. (2). To our knowledge, this is the first report of P. citrophthora on P. barbatus in Italy as well as in Europe. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997 (2) F. E. Brooks and D. M. Ferrin. Plant Dis. 79:212, 1995. (3) D. E. L. Cooke and J. M. Duncan. Mycol. Res. 101:667, 1997. (4) H. Masago et al. Phytopathology 67:425, 1977.

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