First Report of Phytophthora megasperma Causing Decline and Death on Celtis australis in Italy

European hackberry (Celtis australis L.) is a popular shade tree mainly planted in southern Europe and known to be tolerant to dry and poor soils. In early autumn 2013, hackberry plants grown in soil in a commercial nursery located in the floodplain in Umbria region showed symptoms of wilting, dieback, and death. Up to 100% of the canopy was affected, and over 60% of the plants were symptomatic or dead. A Phytophthora species was consistently isolated from symptomatic 6-year-old plants by plating small pieces of collar and root tissues, cut from the margin of dark-brown necrotic lesions, onto P5ARPH selective medium (4). Pure cultures were obtained by single-hyphal transfers on potato dextrose agar (PDA). Sporangia, produced on pepper seeds in soil extract solution (3), were nonpapillate and noncaducous, measuring 34.0 to 85.0 × 22.0 to 50.0 μm. Oospores had an average diameter of 44 μm with mostly paragynous antheridia. On the basis of morphological features, the isolates were identified as P. megasperma Drech. (2). The identity was confirmed by sequencing the cytochrome c oxidase subunit II (Cox II) (5), which gave 100% identity with P. megasperma sequences available in GenBank (GU222070), and by sequencing the internal transcribed spacer (ITS) using the universal primers ITS4 and ITS6, which gave 99% identity with the AF266794 sequence from Cooke et al. (1). The sequences of one isolate (AB239) were deposited in the European Nucleotide Archive (ENA) with accession numbers HG973451 and HG973450 for Cox II and ITS, respectively. Pathogenicity tests were conducted in the greenhouse with isolate AB239 on eight 2-year-old potted European hackberry plants. Mycelial plugs (5 mm diameter) cut from the margins of actively growing 8-day-old cultures on PDA were inserted through the epidermis to the phloem at the collar level. Two plants were used as controls and treated as described above except that sterile PDA plugs replaced the inoculum. Inoculated plants were kept for 4 weeks in a greenhouse at 24 ± 2°C. During that period, inoculated plants showed wilting symptoms similar to those observed in the field. Lesions were evident at all the inoculation points progressing downward to the roots. Colonies of Phytophthora were isolated from the margins of lesions and identified as P. megasperma, thus fulfilling Koch's postulates. Controls remained symptomless. P. megasperma taxonomy is rather complex since it embraces different subgroups, including host specialized forms (formae speciales), some of which are recognized as biological species. Based on morphological and molecular data presented here, the Phytophthora isolates from hackberry belong to P. megasperma sensu stricto, which is included in the “pathogenic to a broad range of hosts” (BHR) group (1). This pathogen is rather polyphagous, attacking mainly fruit and ornamental woody plants, commonly Prunus spp., Malus spp., and Actinidia deliciosa. Like other homothallic Phytophthora species, it is particularly dangerous due to its abundant production of thick-walled resting oospores that enable long-term survival in the soil. To our knowledge this is the first report of P. megasperma sensu stricto (1) on C. australis and its family Ulmaceae/Cannabaceae. References: (1) D. E. L. Cooke et al. Fungal Genet. Biol. 30:17, 2000. (2) D. C. Erwin and O. K. Ribeiro, American Phytopathological Society, St. Paul, MN, 1996. (3) E. Ilieva et al. Eur. J. Plant Path. 101:623, 1995. (4) S. N. Jeffers and S. B. Martin. Plant Dis. 70:1038, 1986. (5) F. N. Martin and P. W. Tooley. Mycologia 95:269, 2003.

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First Report of Phytophthora ramorum on Viburnum bodnantense in Belgium

Plant Disease ◽

10.1094/pdis.2003.87.2.203c ◽

2003 ◽

Vol 87 (2) ◽

pp. 203-203 ◽

Cited By ~ 11

Author(s):

D. De Merlier ◽

A. Chandelier ◽

M. Cavelier

Keyword(s):

The Netherlands ◽

Plant Protection ◽

Morphological Characteristics ◽

Pcr Primers ◽

Selective Medium ◽

Phytophthora Species ◽

Phytophthora Ramorum ◽

Pathogenicity Test ◽

First Report ◽

Root Necrosis

In the past decade, a new Phytophthora species inducing shoot canker on Rhododendron and dieback of Viburnum has been observed in Europe, mainly in Germany and the Netherlands, and California. This new pathogen has been named Phytophthora ramorum (3). In May 2002, a diseased Viburnum plant (Viburnum bodnantense) from the Plant Protection Service (Ministry of Agriculture, Belgium) was submitted to our laboratory for diagnosis. Symptoms included wilting, leaves turning from green to brown, discolored vascular tissues, and root necrosis. The plant came from a Belgian ornamental nursery that obtained supplies of stock plants from the Netherlands. Pieces of necrotic root tissue were excised, surface-disinfected, and transferred aseptically to a Phytophthora selective medium. P. ramorum was identified based on morphological characteristics, including the production of numerous, thin-walled chlamydospores (25 to 70 µm in diameter, average 43 µm) and deciduous, semi-papillate sporangia arranged in clusters. Radial growth after 6 days at 20°C on V8 juice agar was 2.8 mm per day. Random amplified microsatellite markers (RAMS) (2) from the total genomic DNA of the Belgian strain (CBS 110901) were similar to those of P. ramorum reference strains (CBS 101330, CBS 101332, and CBS 101554). Using PCR primers specific for P. ramorum, the identification was confirmed by W. A. Man in't Veld (Plantenziektenkundige Dienst, Wageningen, the Netherlands) (1). A pathogenicity test was carried out on three sterile cuttings of Rhododendron catawbiense (3). Brown lesions were observed on the inoculated cuttings after 6 to 7 days. None of the three uninoculated cuttings showed symptoms of infection. P. ramorum was reisolated from lesion margins on the inoculated cuttings. To our knowledge, this is the first report of the fungus from Belgium. Since our initial observation, we have found P. ramorum in other Belgian nurseries on R. yakusimanum. References: (1) M. Garbelotto et al. US For. Ser. Gen. Tech. Rep. PSW-GRT. 184:765, 2002. (2) J. Hantula et al. Mycol. Res. 101:565, 1997. (3) S. Werres et al. Mycol. Res. 105:1155, 2001.

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First Report of Phytophthora hydropathica Causing Wilting and Shoot Dieback on Viburnum in Italy

Plant Disease ◽

10.1094/pdis-03-14-0308-pdn ◽

2014 ◽

Vol 98 (11) ◽

pp. 1582-1582 ◽

Cited By ~ 5

Author(s):

S. Vitale ◽

L. Luongo ◽

M. Galli ◽

A. Belisario

Keyword(s):

Natural Infection ◽

Morphological Characteristics ◽

Leaf Tissue ◽

The United States ◽

Selective Medium ◽

Phytophthora Species ◽

Phytophthora Ramorum ◽

Width Ratio ◽

Morphological Identification ◽

First Report

The genus Viburnum comprises over 150 species of shrubs and small trees such as Laurustinus (Viburnum tinus L.), which is one of the most widely used ornamental plants in private and public gardens. Furthermore, it commonly forms stands of natural woodland in the Mediterranean area. In autumn 2012, a survey was conducted to determine the presence of Phytophthora ramorum on Viburnum in commercial nurseries in the Latium region where wilting, dieback, and death of twigs were observed on 30% of the Laurustinus plants. A Phytophthora species was consistently recovered from soil rich in feeder roots from potted Laurustinus plants showing symptoms. Soil samples were baited with rhododendron leaves. Small pieces of leaf tissue cut from the margin of lesions were plated on P5ARPH selective medium (4). Pure cultures, obtained by single-hypha transfers on potato dextrose agar (PDA), were petaloid. Sporangia formation was induced on pepper seeds (3). Sporangia were almost spherical, ovoid or obpyriform, non-papillate and non-caducous, measuring 36.6 to 71.4 × 33.4 to 48.3 μm (average 53.3 × 37.4 μm) with a length/width ratio of 1.4. Chlamydospores were terminal and 25.2 to 37.9 μm in diameter. Isolates were considered heterothallic because they did not produce gametangia in culture or on the host. All isolates examined had 30 to 35°C as optimum temperatures. Based on these morphological characteristics, the isolates were identified as Phytophthora hydropathica (2). Morphological identification was confirmed by internal transcribed spacer (ITS), and mitochondrial partial cytochrome oxidase subunit 2 (CoxII) with BLAST analysis in the NCBI database revealing 99% identity with ITS and 100% identity with CoxII. The sequences of the three isolates AB234, AB235, and AB236 were deposited in European Nucleotide Archive (ENA) with the accession nos. HG934148, HG934149, and HG934150 for ITS and HG934151, HG934152, and HG934153 for CoxII, respectively. Pathogenicity tests were conducted in the greenhouse on a total of six 1-year-old shoots cut from V. tinus plants with two inoculation points each. Mycelial plugs cut from the margins of actively growing 8-day-old cultures on PDA were inserted through the epidermis into the phloem. Controls were treated as described above except that sterile PDA plugs replaced the inoculum. Shoots were incubated in test tubes with sterile water in the dark at 24 ± 2°C. After 2 weeks, lesions were evident at the inoculation points and symptoms were similar to those caused by natural infection. P. hydropathica was consistently re-isolated from the margin of lesions, while controls remained symptomless. In the United States in 2008, P. hydropathica was described as spreading from irrigation water to Rhododendron catawbiense and Kalmia latifolia (2). This pathogen can also attack several other horticultural crops (1), but to our knowledge, this is the first report of P. hydropathica causing wilting and shoot dieback on V. tinus. References: (1) C. X. Hong et al. Plant Dis. 92:1201, 2008. (2) C. X. Hong et al. Plant Pathol. 59:913, 2010. (3) E. Ilieva et al. Eur. J. Plant Path. 101:623, 1995. (4) S. N. Jeffers and S. B. Martin. Plant Dis. 70:1038, 1986.

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First Report of Armillaria tabescens Causing Armillaria Root Rot of Pindo Palm in South Carolina

Plant Disease ◽

10.1094/pd-90-1106a ◽

2006 ◽

Vol 90 (8) ◽

pp. 1106-1106 ◽

Cited By ~ 3

Author(s):

G. Schnabel ◽

P. K. Bryson ◽

M. A. Williamson

Keyword(s):

South Carolina ◽

Selective Medium ◽

Plant Diseases ◽

Universal Primers ◽

Its2 Region ◽

Palm Tree ◽

Single Spore ◽

First Report ◽

Single Spore Isolate ◽

Palm Trees

A Pindo palm tree (Butia capitata) declined in a commercial landscape setting in Georgetown, SC during June of 2005. In the spring, after looking healthy the previous year, the entire canopy collapsed with leaves attached. The canopy defoliated shortly thereafter. A cross section through primary and secondary roots of the wilting plant revealed necrotic areas with the presence of white mycelial fans. Diseased roots containing mycelial fans were collected and small sections were transferred to benomyl dichloran streptomycin (BDS) selective medium. Fungal cultures grew approximately 1 mm in diameter per day and developed aeriel mycelium first. Later, cultures developed mainly crustose mycelium with some parts being aerial. Ribosomal internal transcribed spacer (ITS) regions 1 and 2 were polymerase chain reaction amplified with universal primers ITS1-F and ITS4 and sequenced (GenBank Accession No. DQ109806). A BLAST search in GenBank of the ITS1-5.8S-ITS2 region identified the pathogen as Armillaria tabescens (Scop.) Emel (synonym Clitocybe tabescens (Fr.) Bres) with 98% sequence homology to A. tabescens single-spore isolate ss23 from South Carolina (Accession No. AY695408). The diploid culture from the roots of the Pindo palm was compatible with haploid tester strains of A. tabescens as indicated by diploidization of the haploid mycelium. The disease has been reported on Pindo palm in Florida (1), but to our knowledge, this is the first report of A. tabescens causing disease on Butia species in South Carolina. Our findings indicate that Pindo palm trees could be at risk for infection and should not be cultivated in soils containing pathogenic Armillaria species. Reference: (1) S. A. Alfieri, Jr. et al. Index of Plant Diseases in Florida (Revised). Fla. Dep. Agric. Consum. Serv. Div. Plant Ind. Bull. 11:389, 1984.

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First Report of Citrus Root Rot Caused by Phytophthora palmivora in Egypt

Plant Disease ◽

10.1094/pdis-02-13-0206-pdn ◽

2014 ◽

Vol 98 (1) ◽

pp. 155-155 ◽

Cited By ~ 1

Author(s):

Y. Ahmed ◽

A. M. D'Onghia ◽

A. Ippolito ◽

T. Yaseen

Keyword(s):

Mating Type ◽

Root Rot ◽

Its Region ◽

Selective Medium ◽

Phytophthora Palmivora ◽

Universal Primers ◽

Potential Threat ◽

First Report ◽

Citrus Root ◽

International Mycological Institute

During spring-summer 2009, a survey was conducted to determine the species of Phytophthora present in citrus nurseries in Egypt. A total of 300 samples of soil and fibrous roots were collected from the rhizosphere of symptomatic Volkameriana lemon (Citrus volkameriana Tan. & Pasq.) plants growing in Delta (Benha-Qalyubia) and a desert (Cairo/Alexandria desert road) citrus nurseries. Plants showed various symptoms. Canopies of affected plants showed few and yellowish leaves, a general stunted growth, no new vegetation, and sometimes sudden desiccation; the root system showed few dark brown feeder roots, no new yellow-white apexes, and a fibrous appearance of the rootlets due to disintegration of the cortical bark but not of the xylem. Collected rootlets and soil were plated in Petri dishes containing a selective medium for the oomycete Phytophthora (2) and incubated for 3 to 6 days at 19 ± 1°C as described by Ippolito et al. (1). Pure cultures were obtained by single-hypha transfers and the isolates were identified as Phytophthora palmivora (Butler) Butler on the basis of morphological and cultural characteristics (3). Isolates formed stoloniferous colonies on potato dextrose agar (PDA) and grew between 10 and 30°C, with the optimum at 25°C. On V8 juice agar, they showed a highly fluffy pattern and produced terminal and intercalary globose chlamydospores. Sporangia were papillate, elliptical (45 to 51 × 29 to 35 μm; length/breadth ratio of 1.3:1.8), and were caducous with short pedicel. All isolates were A2 mating type, forming spherical oogonia and amphigynous antheridia in dual cultures with reference P. palmivora isolate of A1 mating type. Identification of the isolates was further confirmed by amplification and sequencing of the internal transcribed spacer (ITS) region using the universal primers ITS4 and ITS6. BLASTn analysis of ITS sequences (GenBank Accession No. HE583183) showed 99% homology with P. palmivora isolates available in GenBank. Pathogenicity tests for P. palmivora were conducted by inoculating three groups of ten 6-month-old Volkameriana lemon plants, transplanted into 1.4 liter pots with growing medium artificially inoculated at the rate of 1% (v/v) of P. palmivora inoculum produced according to Yaseen (4). Ten uninoculated plants served as a control. Two months after the inoculation, plants were analyzed for canopy symptoms and the presence of pathogen in feeder roots. More than 50% of inoculated plants showed foliage symptoms and extensive decay of feeder roots. Colonies of Phytophthora were recovered from necrotic rootlets and identified as P. palmivora, fulfilling Koch's postulates. To the best of our knowledge, this is the first report of P. palmivora as a pathogen to citrus plants in the Egyptian nurseries. P. palmivora should be considered a potential threat to the Egyptian citrus industry since it may negatively influence the nurseries and orchards production in the future. References: (1) A. Ippolito, V. De Cicco, and M. Salerno. Rivista di Patologia Vegetale 2:57, 1992. (2) H. Masago, M. Yoshikawa, M. Fukada, and N. Nakanishi. Phytopathology 67:425, 1977. (3) D. J. Stamps. Revised tabular key to the species of Phytophthora. CAB International Mycological Institute, Kew, Surrey, 1990. (4) T. Yaseen. Molecular diagnosis and biological control of Phytophthora-citrus root rot. PhD thesis. University of Bari, Italy, 2004.

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First Report of Phytophthora megasperma Associated with Decline and Death of Common Walnut Trees in Italy

Plant Disease ◽

10.1094/pdis-05-12-0470-pdn ◽

2012 ◽

Vol 96 (11) ◽

pp. 1695-1695 ◽

Cited By ~ 2

Author(s):

A. Belisario ◽

L. Luongo ◽

M. Galli ◽

S. Vitale

Keyword(s):

Juglans Regia ◽

Morphological Characteristics ◽

Average Diameter ◽

Soil Extract ◽

Phytophthora Species ◽

Phytophthora Megasperma ◽

First Report ◽

Fruit Species ◽

Branch Dieback ◽

Common Walnut

Common walnut (Juglans regia L.) is an important nut crop in Italy, which is the fifth largest producer of walnut in Europe. In recent years, walnut decline and subsequent death has increased in many Italian commercial orchards. In the summer of 2010, several declining trees were present in waterlogged area of a walnut orchard located in the Veneto region. Symptoms included sparse foliage, wilting, and shoot and branch dieback. By the next year, a larger area of about 1 ha with 20% of dead trees was present, and soil/root samples were subjected to azalea leaf baiting and successively cultured on PARBH medium (3). Isolates were identified as Phytophthora megasperma based on morphological characteristics (2) and DNA sequence analysis. Sporangia were 35.0 to 62.0 × 12.0 to 30.0 μm, nonpapillate, and noncaducous when produced in soil extract solution. Oogonia had an average diameter of 36 μm with mostly paragynous antheridia. Identity was confirmed by sequence comparison in NCBI database with 99% and 100% identity for internal transcribed spacer (ITS) and mitochondrial partial COI (4) for cytochrome oxidase subunit 1, respectively. The sequences of the isolate AB199 were deposited in GenBank with the accession nos. HE805270 and HE805269 for ITS and COI, respectively. Pathogenicity tests were conducted in the greenhouse on six 1-year-old walnut shoots with two inoculation points each. Mycelial plugs cut from the margins of actively growing 8-day-old cultures on PDA were inserted through the epidermis to the phloem. Controls were treated as described above except for inoculation with sterile PDA plugs. After inoculation, shoots were incubated in test tubes with sterile water for 1 week in the dark at 22 ± 2°C. Lesions were evident at the inoculation points. P. megasperma was consistently reisolated from the margin of symptomatic tissues. Controls remained symptomless. P. megasperma is a polyphagous, ubiquitarious Phytophthora species that attacks many crops and fruit species including walnut. Although several other species of Phytophthora have been reported from Italy (1), to the best of our knowledge, this is the first report of Phytophthora decline on common walnut in Italy caused by P. megasperma. References: (1) A. Belisario et al. Acta Hort. 705:401, 2006. (2) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996. (3) G. C. Papavisas et al. Phytopathology 71:129, 1981. (4) G. P. Robideau et al. Mol. Ecol. Resour. 11:1002, 2011.

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First Report of Bud Rot of Canary Island Date Palm Caused by Phytophthora palmivora in Italy

Plant Disease ◽

10.1094/pdis-91-8-1059a ◽

2007 ◽

Vol 91 (8) ◽

pp. 1059-1059

Author(s):

A. Pane ◽

C. Allatta ◽

G. Sammarco ◽

S. O. Cacciola

Keyword(s):

Canary Island ◽

Date Palm ◽

Brown Rot ◽

Selective Medium ◽

Phytophthora Species ◽

Phytophthora Palmivora ◽

American Phytopathological Society ◽

First Report ◽

Phoenix Canariensis ◽

Electrophoretic Patterns

Canary Island date palm (Phoenix canariensis hort. ex Chabaud) is planted as an ornamental in Mediterranean climatic regions of the world. From 2004 to 2006, withering of the spear leaf was observed on screenhouse-grown potted plants of this palm in Sicily (Italy). The first symptom was a dark brown rot that extended from the petiole base of the spear to the adjacent youngest leaves and killed the bud. Dissection of plants revealed a foul-smelling internal rot. After the bud died, external older leaves remained green for months. As much as 10% of plants in a single nursery were affected. A Phytophthora species was consistently isolated from symptomatic plants on BNPRAH selective medium (4). Single zoospore isolates were obtained from the colonies. The species isolated was identified as Phytophthora palmivora (E. J. Butler) E. J. Butler on the basis of morphological and cultural characteristics (3). On V8 juice agar, the isolates produced elliptical to ovoid, papillate sporangia (33 to 77 × 22 to 38 μm) with a mean length/breadth ratio of 1.8. Sporangia were caducous with a short pedicel (mean pedicel length = 5 μm) and had a conspicuous basal plug. All isolates were heterothallic and produced amphigynous antheridia, oogonia, and oospores when paired with reference isolates of P. nicotianae and P. palmivora of the A2 mating type. The oogonium wall was smooth. Identification was confirmed by electrophoresis of mycelial proteins in polyacrylamide slab gels (1). The electrophoretic patterns of total mycelial proteins and four isozymes (alkaline phosphatase, esterase, glucose-6-phosphate dehydrogenase, and malate dehydrogenase of the isolates) from Phoenix canariensis were identical to those of P. palmivora reference isolates, including four Italian ones, two from pittosporum and olive, respectively, and two (IMI 390579 and 390580) from Grevillea spp. Phoenix canariensis isolates were clearly distinct from those of other heterothallic papillate species including P. capsici, P. citrophthora, P. katsurae, P. nicotianae, and P. tropicalis. Pathogenicity of one isolate from Phoenix canariensis (IMI 395345) was tested on 10 2-year-old potted Canary Island date palm plants. An aqueous 105 zoospores per ml suspension (200 μl) was pipetted onto unwounded petiole bases of the three youngest central leaves of each plant. Sterile water was pipetted onto 10 control plants. All plants were incubated in 100% humidity at 24°C for 48 h and maintained in a greenhouse at 20 to 28°C. Within 3 weeks after inoculation, inoculated plants developed symptoms identical to those observed on plants with natural infections. Control plants remained healthy. P. palmivora was reisolated from symptomatic plants. Phytophthora bud rot is a common palm disease worldwide and Phoenix canariensis is reported as a host (2). To our knowledge, this is the first report of Phytophthora bud rot on Phoenix canariensis in Italy. References: (1) S. O. Cacciola et al. EPPO Bull. 20:47, 1990. (2) M. L. Elliot et al., eds. Compendium of Ornamental Palm Diseases and Disorders. The American Phytopathological Society, St. Paul, MN, 2004. (3) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996. (4) H. Masago et al. Phytopathology, 67:425, 1977.

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First Report of Phytophthora tentaculata Causing Root and Stem Rot of Oregano in Italy

Plant Disease ◽

10.1094/pdis-93-8-0843b ◽

2009 ◽

Vol 93 (8) ◽

pp. 843-843 ◽

Cited By ~ 2

Author(s):

P. Martini ◽

A. Pane ◽

F. Raudino ◽

A. Chimento ◽

S. Scibetta ◽

...

Keyword(s):

Dna Amplification ◽

Its Region ◽

Selective Medium ◽

Stem Rot ◽

Universal Primers ◽

Basal Stem Rot ◽

First Report ◽

Soilborne Disease ◽

Potted Plants ◽

Morphological Criteria

Oregano (Origanum vulgare L.; Lamiaceae) is cultivated for culinary and medicinal purposes and as an ornamental. In October of 2007, 1- to 2-year-old potted plants of oregano showed symptoms of decline associated with root and basal stem rot in a nursery in Liguria (northern Italy) that produces 1 million to 1.5 million potted aromatic plants per year. Aboveground symptoms included leaf russeting and chlorosis, wilt, defoliation and dieback of twigs, browning of the basal stem, and subsequent collapse of the entire plant. Approximately 80% of the plants died within 30 days after the appearance of the first symptoms on the canopy. Approximately 20% of a stock of 30,000 oregano plants was affected. Stocks of other aromatic species, such as mint, lavender, rosemary, and sage, appeared healthy. A Phytophthora species was consistently isolated from symptomatic stems and roots of oregano plants on BNPRAH selective medium (2). Ten pure cultures were obtained by single-hypha transfers, and the species was identified as Phytophthora tentaculata Kröber & Marwitz by morphological criteria and sequencing of the internal transcribed spacer (ITS) region of rDNA using the ITS 4 and ITS 6 universal primers for DNA amplification. Isolates from oregano formed stoloniferous colonies with arachnoid mycelium on potato dextrose agar and had a growth rate of 2 to 3 mm per day at 24°C with optimum, minimum, and maximum temperatures of 24, 8, and 34°C, respectively. Sporangia formed in soil extract solution and were papillate and spherical or ovoid to obpyriform with a length/breadth ratio of 1.3:1. Few sporangia were caducous and all had a short pedicel (<5 μm). Hyphal swellings and chlamydospores were produced in sterile distilled water and corn meal agar, respectively. All isolates were homothallic and produced globose terminal oogonia (mean diameter of 34 μm) with one or occasionally two paragynous, monoclinous, or diclinous antheridia. Amphigynous antheridia were also observed. The sequence of the ITS region of the rDNA (GenBank No. FJ872545) of an isolate from oregano (IMI 395782) showed 99% similarity with sequences of two reference isolates of P. tentaculata (Accession Nos. AF266775 and AY881001). To test for pathogenicity, the exposed root crowns of 10 6-month-old potted plants of oregano were drench inoculated with 10 ml of a suspension of 2 × 104 zoospores/ml of isolate IMI 395782. Sterile water was pipetted onto the roots of 10 control plants. All plants were maintained in 100% humidity at 22 to 24°C in a greenhouse under natural light and watered once a week. Within 3 weeks after inoculation, all inoculated plants developed symptoms identical to those observed in the nursery and died within 30 to 40 days after the appearance of the first symptoms. Control plants remained healthy. P. tentaculata was reisolated solely from symptomatic plants. P. tentaculata has been reported previously on several herbaceous ornamental plants (1,3). However, to our knowledge, this is the first report of this species on O. vulgare. Root and basal stem rot caused by P. tentaculata is the most serious soilborne disease of oregano reported in Italy so far. References: (1) G. Cristinzio et al. Inf. Fitopatol. 2:28, 2006. (2) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996. (3) H. Kröber and R. Marwitz. Z. Pflanzenkr. Pflanzenschutz 100:250, 1993.

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First Report of Phytophthora cinnamomi on Quercus laurifolia

Plant Disease ◽

10.1094/pdis.2002.86.4.441d ◽

2002 ◽

Vol 86 (4) ◽

pp. 441-441 ◽

Cited By ~ 7

Author(s):

A. K. Wood ◽

F. H. Tainter

Keyword(s):

Phytophthora Cinnamomi ◽

Soil Extract ◽

Selective Medium ◽

Phytophthora Species ◽

Soil Samples ◽

Tissue Samples ◽

First Report ◽

Central Florida ◽

Oak Trees ◽

Length Width

In May 2001, bleeding cankers were observed on several laurel oak (Quercus laurifolia) trees in central Florida. Affected trees had chlorotic leaves, sparse canopies, and little new growth. Multiple cankers were present on the trunk and extended from the soil line up to approximately 5 m. Each canker had a reddish to dark brown or black exudate. From two of the infected trees, tissue samples were taken from beneath the bark around the edge of an actively growing lesion and transferred directly to Phytophthora-selective medium (1), and three soil cores (2 cm in diameter, 20 cm deep) were collected from the base of each tree. A baiting bioassay (with camellia leaf disks and shore juniper and eastern hemlock needles as baits) was used to assay fresh composite soil samples for Phytophthora species (1). P. cinnamomi was recovered from both tissue and soil samples (2). Mycelia were coralloid with abundant hyphal swellings. Sporangia were produced in 1.5% nonsterilized soil extract solution. Sporangia were ovoid to ellipsoid in shape and nonpapillate. Average sporangium size was 72 × 45 μm (length × width). To our knowledge, this is the first report of P. cinnamomi on laurel oak trees. References: (1) A. J. Ferguson and S. N. Jeffers. Plant Dis. 83:1129, 1999. (2) G. M. Waterhouse. Key to the species of Phytophthora de Bary. Mycol. Pap. 92. CMI. Kew, UK, 1963.

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First Report of Phytophthora tropicalis on Rhododendron in Italy

Plant Disease ◽

10.1094/pdis-04-13-0445-pdn ◽

2013 ◽

Vol 97 (10) ◽

pp. 1385-1385 ◽

Cited By ~ 2

Author(s):

L. Luongo ◽

M. Galli ◽

S. Vitale ◽

A. Haegi ◽

A. Belisario

Keyword(s):

Late Summer ◽

Selective Medium ◽

Phytophthora Species ◽

Width Ratio ◽

Broad Host Range ◽

In Planta ◽

First Report ◽

European Nucleotide Archive ◽

Pure Cultures

The genus Rhododendron comprises over 1,000 species, which represent many important ornamental shrubs. Microbial isolations were made from Rhododendron catawbiense plants showing symptoms of wilt, dieback, and death of shoots obtained from two nurseries in the Latium region in the late summer of 2012. A Phytophthora species was consistently recovered by plating small pieces of stem and collar tissues, cut from the margin of lesions, on P5ARPH selective medium. Pure cultures were obtained by single-hyphal transfers and they grew in a rosaceous pattern on potato dextrose agar (PDA) at an optimum temperature of 28 to 30°C. Sporangia formation was induced on pepper seeds (3). Sporangia were ellipsoid, fusiform or obpyriform, papillate, occasionally bipapillate, caducous, with a long pedicel (up to 100 μm), and mean dimensions of 45 × 25 μm with a mean length/width ratio of 1.8. Chlamydospores ranged from 25 to 32 μm in diameter. Isolates were considered heterothallic because they did not produce gametangia in vitro or in planta. On the basis of morphological features, the isolates were identified as Phytophthora tropicalis Aragaki & Uchida. Identity was confirmed by sequence comparison in GenBank with 99% homology both for internal transcribed spacer (ITS) and mitochondrial partial COI for cytochrome oxidase subunit 1. The sequences of two isolates AB211 and AB212 were deposited in the European Nucleotide Archive (ENA) with accession nos. HF937577 and HF937578 for ITS, and HF937579 and HF937580 for COI, respectively. Pathogenicity tests were conducted in the greenhouse on a total of six 1-year-old shoots cut from R. catawbiense plants with two inoculation points each. Mycelial plugs cut from the margins of actively growing 8-day-old cultures on PDA were inserted through the epidermis to the phloem. Controls were treated as described above except for inoculation with sterile PDA plugs. Inoculated shoots were incubated in test tubes with sterile water for 1 week in the dark at 26 ± 2°C. Lesions were evident at the inoculation points. P. tropicalis was consistently reisolated from the margin of symptomatic tissues. Control shoots remained symptomless. In Italy, P. tropicalis has been reported on several ornamental species (1) and on apricot trees (4) indicating a broad host range. On the same host it has been reported in Virginia, United States (2). To the best of our knowledge, this is the first report of Phytophthora damage on Rhododendron caused by P. tropicalis in Italy. References: (1) S. O. Cacciola et al. Plant Dis. 90: 680, 2006. (2) C. X. Hong et al. Plant Dis. 90: 525, 2006. (3) E. Ilieva et al. Eur. J. Plant Path. 101: 623, 1995. (4) A. Pane et al. Plant Dis. 93: 844, 2009.

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First Report of Wilt and Dieback on Pokeweed (Phytolacca decandra) Caused by Phytophthora nicotianae

Plant Disease ◽

10.1094/pdis.2003.87.1.101c ◽

2003 ◽

Vol 87 (1) ◽

pp. 101-101

Author(s):

A. Belisario ◽

M. Maccaroni ◽

L. Corazza

Keyword(s):

Tap Water ◽

Selective Medium ◽

Phytophthora Species ◽

Phytophthora Nicotianae ◽

Malt Extract ◽

Internal Transcribed Spacer Region ◽

Invasive Weed ◽

Disease Symptoms ◽

First Report ◽

Perennial Plant

Pokeweed (Phytolacca decandra, synonym Phytolacca americana) is a root perennial plant that produces a succulent annual stem. In late June 2001, a severe dieback occurred on a group of pokeweed plants being grown as ornamentals in a garden in Rome. Disease symptoms consisted of leaf wilting followed by collapse of the plant. Stem collars and roots had dark brown-to-black water-soaked lesions. A wet rot was observed on plants with advanced disease symptoms. Isolations, from sections of roots and stems previously washed in running tap water, were made on PARBhy selective medium (10 mg of pimaricin, 250 mg of ampicillin [sodium salt], 10 mg of rifampicin, 50 mg of hymexazol, 15 mg of benomyl, 15 g of malt extract, and 20 g of agar in 1,000 ml of H2O) (2), followed by incubation at 20°C. A species of Phytophthora identified based on morphological and cultural characteristics (1) was isolated consistently from rotted roots and collars of diseased plants. All isolates produced papillate, spherical, ovoid to obturbinate, noncaducous sporangia and terminal and intercalary chlamydospores. Hyphal swellings with hyphal outgrowths were present. Observed characteristics were similar to those described for P. nicotianae. Isolates were mating type A2 with amphigynous antheridia in paired cultures with the A1 tester isolate of P. nicotianae. Identification was confirmed by comparing restriction fragment length polymorphism patterns of the internal transcribed spacer region of ribosomal DNA with those obtained from previously identified Phytophthora species. Pathogenicity tests were conducted on 10 2-month-old potted pokeweed plants. Inoculum was prepared by inoculating sterilized millet seeds moistened with V8 broth with plugs of mycelium and growing for 4 weeks. The inoculum was added to potting soil at 3% (wt/vol), and sporulation was induced by flooding the soil for 48 h. Five uninoculated plants were used as controls. Plants were maintained outdoors and assessed for symptoms within 2 months after inoculation. Wilting, root rot, and dark brown lesions on the collar developed on inoculated plants. The pathogen was reisolated from the inoculated plants and morphologically identical to the original isolates, which confirmed P. nicotianae as the causal agent of the disease. Few diseases have been reported on Phytolacca decandra. This species is not only an invasive weed, but is also cultivated as an ornamental and medicinal plant. In addition, antiviral (PAP) and antifungal (Pa-AFP) proteins that are used as a remedy for several human and plant infections have been extracted from the plant. To our knowledge, this is the first report of P. nicotianae on pokeweed. References: (1) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996. (2) A. M.Vettraino et al. Plant Pathol. 50:90, 2001.

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