scholarly journals First Report of Phytophthora cinnamomi Root Rot, Stem, and Leaf Blight on Ivy

Plant Disease ◽  
1997 ◽  
Vol 81 (8) ◽  
pp. 960-960 ◽  
Author(s):  
K. Thinggaard ◽  
B. Toppe
Keyword(s):  
Nutrient Solution ◽  
Root Rot ◽  
Phytophthora Cinnamomi ◽  
Pond Water ◽  
Pathogenicity Test ◽  
Hedera Helix ◽  
Cedrus Deodara ◽  
First Report ◽  
Stems And Leaves ◽  
Pot Plants

Phytophthora cinnamomi was isolated from varieties of Hedera helix pot plants in 1989 in two Danish greenhouse nurseries. The symptoms were brown, rotten roots and stems, and brown areas developing from the base of the leaves. The fungus was isolated directly from roots, stems, leaves, and soil, and by baiting the nutrient solutions of the watering systems with needles of Cedrus deodara. The fungus was isolated on Phytophthora selective agar medium containing hymexazol and identified with the keys of Kröber (1) and Stamps et al. (2). The fungus was characterized by coralloid hyphal swellings, chlamydospores, lack of oogonia in single culture, and production of numerous, ovoid sporangia with a nonpapillate, wide pore. The sporangia produced many zoospores after 2 days flooding with autoclaved pond water on V8 juice agar, followed by internal proliferation. The fungus was also isolated in Norway in 1993 from ivy pot plants. The fungus was widespread in Danish and Norwegian pot plant nurseries in 1997 and caused losses in most varieties, especially at temperatures above 23°C. Effective fungicides are not available for use in Denmark and the disease is easily spread with cuttings, and through the watering system with recirculation of the nutrient solution. A Danish isolate of P. cinnamomi originating from roots of H. helix was used in a pathogenicity test. Five-week-old cuttings were inoculated by adding zoospores (5 per ml) to the recirculating nutrient solution. Control plants were on a separate bench with nutrient solution without the fungus. After 1 week, symptoms of root rot were observed, and 2 weeks after inoculation, 75% of plants expressed severe symptoms on roots, stems, and leaves. P. cinnamomi was reisolated from roots, stems, and leaves of diseased plants, but was not isolated from the control plants. The reisolate was morphologically identical to the original isolate. This is the first report of P. cinnamomi from ivy in Europe. References: (1) H. Kröber. Mitt. Biol. Bundesanst. Land Forstwirtsch. Berlin-Dahlem 225:73, 1985. (2) D. J. Stamps et al. 1990. Mycol. Pap. No. 162. CAB Int. Mycol. Inst., Kew, England.

scholarly journals Phytophthora mediterranea sp. nov., a New Species Closely Related to Phytophthora cinnamomi from Nursery Plants of Myrtus communis in Italy

Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 682
Author(s):  
Carlo Bregant ◽  
Antonio A. Mulas ◽  
Giovanni Rossetto ◽  
Antonio Deidda ◽  
Lucia Maddau ◽  
...  
Keyword(s):  
New Species ◽  
Root Rot ◽  
Phytophthora Cinnamomi ◽  
Colony Growth ◽  
Phytophthora Species ◽  
Maximum Temperature ◽  
Pathogenicity Test ◽  
Forest Nurseries ◽  
Collar And Root Rot ◽  
A New Species

Monitoring surveys of Phytophthora related diseases in four forest nurseries in Italy revealed the occurrence of fourteen Phytophthora species to be associated with collar and root rot on fourteen plants typical of Mediterranean and alpine regions. In addition, a multilocus phylogeny analysis based on nuclear ITS and ß-tubulin and mitochondrial cox1 sequences, as well as micromorphological features, supported the description of a new species belonging to the phylogenetic clade 7c, Phytophthora mediterranea sp. nov. Phytophthora mediterranea was shown to be associated with collar and root rot symptoms on myrtle seedlings. Phylogenetically, P. mediterranea is closely related to P. cinnamomi but the two species differ in 87 nucleotides in the three studied DNA regions. Morphologically P. mediterranea can be easily distinguished from P. cinnamomi on the basis of its smaller sporangia, colony growth pattern and higher optimum and maximum temperature values. Data from the pathogenicity test showed that P. mediterranea has the potential to threaten the native Mediterranean maquis vegetation. Finally, the discovery of P. cinnamomi in alpine nurseries, confirms the progressive expansion of this species towards cold environments, probably driven by climate change.

scholarly journals First Report of Pythium Root Rot of Rau Ram (Polygonum odoratum)

Plant Disease ◽  
2005 ◽  
Vol 89 (3) ◽  
pp. 340-340
Author(s):  
E. N. Rosskopf ◽  
C. B. Yandoc ◽  
B. Stange ◽  
E. M. Lamb ◽  
D. J. Mitchell
Keyword(s):  
Root Rot ◽  
Vascular System ◽  
Pond Water ◽  
Centraalbureau Voor ◽  
First Report ◽  
Pathogenicity Tests ◽  
Symptomatic Tissue ◽  
Pythium Helicoides ◽  
Production House ◽  
Test Plants

Polygonum odoratum (= Persicaria odorata), known as rau ram or sang hum, is native to southeastern Asia and is a common herb in Vietnamese cuisine (1). It has been studied most extensively for its aromatic compound content (2). In Florida, rau ram commonly is grown hydroponically in greenhouses using large, cement beds with recirculated water. The plants form dense mats from which new growth is trimmed for market. During January of 2002, a severe dieback was observed in one production house in Saint Lucie County, FL. Plants with less severe symptoms were yellowed and stunted. Roots of symptomatic plants were largely decayed with root symptoms beginning as a tip necrosis. The cortex of severely affected roots slipped off easily, leaving a stringy vascular system. Plating of symptomatic tissue from 20 randomly selected plant samples was performed with multiple general and selective media including potato dextrose agar, corn meal agar with pimaricin, ampicillin, rifampicin, and pentachloronitrobenzene (PARP) (3). All colonies produced were identified as Pythium helicoides Drechsler on the basis of sporangial, oogonial, and antheridial characteristics (4). Isolates had proliferous, obovoid, papillate sporangia, and were homothallic with smooth-walled oogonia and thick-walled, aplerotic oospores. Multiple antheridial attachments per oogonium were common with the antheridium attached along its entire length. Pathogenicity tests were conducted using P. odoratum plants grown from commercial transplants. Two tests were performed. Each test was conducted using eight inoculated and eight control plants. In the first test, plants were maintained in 10-cm pots immersed in sterilized pond water for the duration of the test. Plants were inoculated with five 7- × 70-mm sections of freshly growing mycelial culture per plant using 10-day-old cultures of Pythium helicoides grown on water agar. Chlorosis was observed at approximately 2 months after inoculation. Root necrosis was observed in inoculated plants approximately 5 months after inoculation. This test was performed in the greenhouse with temperatures ranging from 20 to 30°C. The second test was performed in growth chambers at 35 to 40°C. Plants were maintained in 10-cm pots immersed in Hoagland's solution and were inoculated with four 6-mm plugs per plant. Symptoms were observed on inoculated plants at this temperature within 1 week of inoculation. No chlorosis or root decay was observed in noninoculated, immersed plants. The pathogen was reisolated from inoculated, symptomatic tissue. To our knowledge, this is the first report of root rot of P. odoratum caused by Pythium helicoides. References: (1) R. E. Bond. Herbarist 55:34, 1989. (2) N. X. Dung et al. J. Essent. Oil Res. 7:339, 1995. (3) M. E. Kannwischer and D. J. Mitchell. Phytopathology 68:1760, 1978. (4) A. J. van der Plaats-Niterink. Monograph of the Genus Pythium. Vol. 21, Studies in Mycology. Centraalbureau voor Schimmelcutltures, Baarn, The Netherlands, 1981.

scholarly journals First Report of Root Rot Caused by Sclerotium rolfsii on Daucus carota var. sativa in Southern Korea

Plant Disease ◽  
2011 ◽  
Vol 95 (12) ◽  
pp. 1585-1585
Author(s):  
J.-H. Kwon ◽  
Y. H. Lee ◽  
H.-S. Shim ◽  
J. Kim
Keyword(s):  
Daucus Carota ◽  
Root Rot ◽  
Pathogenic Fungus ◽  
Sclerotium Rolfsii ◽  
Agricultural Science ◽  
Control Treatment ◽  
Pathogenicity Test ◽  
Optimum Temperature ◽  
First Report ◽  
Causal Fungus

Carrot (Daucus carota var. sativa DC.), an important root vegetable, is cultivated widely because of its dietary fiber and beta carotene. In June 2009 and June 2010, a disease suspected as root rot of carrot caused by Sclerotium rolfsii occurred in a 5-ha field in Jinju, Korea. Early symptoms consisted of water-soaked lesions on root and lower stem tissue near the soil line. Infected plants gradually withered and white mycelial mats appeared on the surface of roots. Numerous sclerotia were often produced on stem and root surfaces in contact with the soil. The heavily infected carrots became rotted and blighted and the whole plant eventually died. The freshly isolated pathogenic fungus was grown on potato dextrose agar (PDA) and examined microscopically. Optimum temperature for mycelia growth or sclerotia formation was 25 to 30°C. Numerous globoid sclerotia formed on the PDA after 18 days of mycelial growth. The sclerotia (1 to 3 mm in diameter) were white at first and then gradually turned dark brown. Aerial mycelia usually formed, consisting of many narrow hyphal strands 3 to 9 μm wide. The white mycelium formed a typical clamp connection after 5 days of growth at optimum temperature. To fulfill Koch's postulates, 10 carrot seedlings were inoculated with colonized agar discs (6 mm in diameter) of the causal fungus directly on the root and incubated in a humid chamber at 25°C for 24 h. Ten carrot seedlings were inoculated similarly with agar discs as the control treatment. After this period, the inoculated and noninoculated plants were maintained in a greenhouse. Eight days after inoculation, the disease symptoms seen in the field were reproduced and the fungus was reisolated from the artificially inoculated plants. To confirm identity of the causal fungus, the complete internal transcribed spacer (ITS) rDNA region of the causal fungus was amplified using the primers ITS1 and ITS4 (2) and sequenced. The resulting sequence of 684 bp was deposited in GenBank (Accession No. JF342557). The sequence was 99% similar to sequences of Athelia rolfsii (Sclerotium rolfsii) in GenBank. Cultures of S. rolfsii have been deposited with the Korean Agricultural Culture Collection (KACC 45154), National Academy of Agricultural Science, Korea. On the basis of symptoms, fungal colonies, the ITS sequence, and the pathogenicity test on the host plant, this fungus was identified as S. rolfsii Saccardo (1). To our knowledge, this is the first report of root rot of carrot caused by S. rolfsii in Korea. This disease is highly dependent upon environmental conditions, including warm weather and high humidity. Recent occurrence of the disease suggests that S. rolfsii could spread widely. References: (1) J. E. M. Mordue. CMI Descriptions of Pathogenic Fungi and Bacteria. No. 410, 1974. (2) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, Inc., New York, 1990.

scholarly journals First Report of Rhizoctonia solani Causing a Disease of Sunflower in India

Plant Disease ◽  
2010 ◽  
Vol 94 (4) ◽  
pp. 488-488 ◽  
Author(s):  
K. Srinivasan ◽  
S. Visalakchi
Keyword(s):  
Rhizoctonia Solani ◽  
Root Rot ◽  
Crown Rot ◽  
Pathogenicity Test ◽  
American Phytopathological Society ◽  
First Report ◽  
Leaf Yellowing ◽  
Crown Tissue ◽  
Symptomatic Tissue ◽  
White Mycelium

During the spring of 2009, symptoms including leaf yellowing and wilting, root rot, and death of plants were noted in sunflower (Helianthus annuus L.) crops in Dharmapuri District, Tamilnadu, India. In some fields, approximately 30% of the plants were affected. The disease began when plants were approximately 10 weeks old and occurred on scattered or adjacent plants. The presence of white mycelium was observed on necrotic crowns. Symptomatic tissue was surface disinfested in 70% alcohol for 30 s and 0.5% sodium hypochlorite for 1 min and plated onto potato dextrose agar (PDA) (1). One isolate (coded SV001) had near right-angle branching with basal constriction and adjacent septa and sclerotia typical of Rhizoctonia spp. (2). Cream-colored colonies produced irregular, light brown sclerotia that were 3.0 to 7.3 mm (average 3.8 mm) in diameter. Hyphae were 6.8 to 7.0 μm (average 6.9 μm) wide and multinucleate (8 to 15 nuclei per cell). On the basis of hyphal anastomosis with several known AG testers, the fungus was characterized as Rhizoctonia solani Kühn AG-IV (3). One culture was deposited at the Madras University Botany Laboratory, Center for Advanced Studies in Botany, University of Madras, Chennai, India. In a pathogenicity test, R. solani SV001 was grown on PDA for 5 days at 24°C in the dark. Five-millimeter-diameter disks were placed at the base of sunflower plants (cv. Mordan). Four sunflower plants in each of three pots were inoculated; noninoculated plants served as controls. Plants were placed in a glasshouse maintained at 25 to 27°C. Inoculated plants developed yellow foliage and crown rot and root rot symptoms after 7 to 12 days and died in 17 to 20 days. No symptoms were observed on noninoculated plants. The pathogen was reisolated from fragments of necrotic crown tissue of inoculated plants. To our knowledge, this is the first report of R. solani AG-IV causing a disease of sunflower plants in India. References: (1). R. C. Fenille et al. Plant Pathol. 54:325, 2005. (2). J. R. Parmeter et al. Phytopathology 59:1270, 1969. (3) B. Sneh et al. Identification of Rhizoctonia Species. The American Phytopathological Society, St Paul, MN, 1991.

scholarly journals First Report of Crown and Root Rot Caused by Pythium myriotylum on Hemp (Cannabis sativa) in Arizona

Plant Disease ◽  
2021 ◽  
Author(s):  
Jiahuai Hu
Keyword(s):  
Root Rot ◽  
Cannabis Sativa ◽  
Morphological Characteristics ◽  
Crown Rot ◽  
Pathogenicity Test ◽  
Light Cycle ◽  
Pythium Myriotylum ◽  
First Report ◽  
Leaf Chlorosis ◽  
Query Coverage

During August and September 2020, symptoms of leaf chlorosis, stunting, and wilting were observed on indoor hemp plants (Cannabis sativa L. cv. ‘Wedding Cake’) in a commercial indoor facility located in Coolidge, Arizona. Plants were grown in soilless coconut coir growing medium (Worm Factory COIR250G10), watered with 1.5 to 2.1 liters every 24 h through drip irrigation, and supplemented with 18 h of lighting. About 35% of plants displayed symptoms as described above and many symptomatic plants collapsed. To identify the causal agent, crown and root tissues from four symptomatic plants were harvested and rinsed with tap water. Tissue fragments (approx. 2 to 4 mm in size) were excised from the margins of the stem and root lesions, surface sterilized in 0.6% sodium hypochlorite for 1 min, rinsed well in sterile distilled water, blotted dry, and plated on potato dextrose agar (PDA) and on oomycete-selective clarified V8 media containing pimaricin, ampicillin, rifampicin, and pentachloronitrobenzene (PARP). Plates were incubated at room temperature (21-24 oC). Five isolates resembling Pythium were transferred after 3 days and maintained on clarified V8 media. Morphological characteristics were observed on grass blade cultures (Waterhouse 1967). Grass blades were placed on CV8 inoculated with the isolate. After a 1-day incubation at 25°C, the colonized blades were transferred to 8 ml of soil water extract in a Petri dish. Ten sporangia and oogonia were selected randomly and their diameters were measured under the microscope. Sporangia were mostly filamentous, undifferentiated or inflated lobulate, ranging from 7 to 17 µm in diameter. Knob-like appressoria were observed on branching clusters. Bulbous-like antheridia were formed on branched stalk with 1-8 antheridia per oogonium. Globose oogonia were terminal or intercalary and ranged from 21 to 33 µm in diameter. Globose oospores were mostly aplerotic and ranged from 15 to 21 μm in diameter. Based on these morphological characteristics, isolates were tentatively identified as Pythium myriotylum (Watanabe, 2002). Genomic DNA was extracted from mycelial mats of two isolates using DNeasy Plant Pro Kit (Qiagen Inc., Valencia, CA) according to the manufacturer’s instructions. The internal transcribed spacer (ITS) region of rDNA was amplified with primers ITS1/ITS4 and two identical nucleotide sequences were obtained and deposited under accession number MW380925. A BLASTn search revealed ≥ 98% query coverage and 100% match with sequences HQ237488.1, KY019264.1, and KM434129, which were isolates of P. myriotylum from palm, tobacco, and ginger, respectively. To fulfill Koch’s postulates, pathogenicity tests were conducted with 2 isolates using plants of ‘Wedding Cake’ grown in 12 1.9-liter pots filled with a steam-disinfested potting mix (Sungro Professional Growing Mix). Pots were placed in a plastic container and watered to flooding three times a week. Plants were maintained in a greenhouse with 18 h/10 h day/night supplemental light cycle (15-28 oC). Plants were fertilized weekly with Peters Professional fertilizer at 1mg/ml. Four plants were inoculated with each isolate at three weeks after seed sowing by placing two 5-mm mycelial plugs from active growing 4 days-old cultures on PDA media adjacent to the main root mass at an approximately 3 cm depth. Four plants were inoculated with blank PDA plugs as controls. Symptoms of leaf chlorosis, crown rot and wilting were observed after four weeks while control plants remained symptomless. P. myriotylum was re-isolated from necrotic roots of inoculated plants after surface-sterilization, but not from control plants. The pathogenicity test was repeated once. While P. myriotylum often occurs in warmer regions and has a wide host range of >100 host plant species including numerous economically important crops (Wang et al., 2003), there are only two reports of this pathogen on indoor hemp plants in a greenhouse in Connecticut (McGehee et al., 2019) and in Canada (Punja et al., 2019). This is the first report of P. myriotylum causing root and crown rot of indoor hemp in Arizona. A more careful water management in soilless growth medium to reduce periods of saturation would minimize the risk of Pythium root rot in indoor hemp production.

scholarly journals First report of Fusarium falciforme (FSSC 3+4) causing root rot on chickpea in Mexico

Plant Disease ◽  
2021 ◽  
Author(s):  
Sixto Velarde Felix ◽  
Victor Valenzuela ◽  
Pedro Ortega ◽  
Gustavo Fierros ◽  
Pedro Rojas ◽  
...  
Keyword(s):  
Fusarium Solani ◽  
Root Rot ◽  
Species Complex ◽  
Elongation Factor ◽  
Morphological Characteristics ◽  
Aerial Mycelium ◽  
Pathogenicity Test ◽  
Conidial Suspension ◽  
Single Spore ◽  
First Report

Chickpea (Cicer aretinium L.) is a legume crop of great importance worldwide. In January 2019, wilting symptoms on chickpea (stunted grow, withered leaves, root rot and wilted plants) were observed in three fields of Culiacan Sinaloa Mexico, with an incidence of 3 to 5%. To identify the cause, eighty symptomatic chickpea plants were sampled. Tissue from roots was plated on potato dextrose agar (PDA) medium. Typical Fusarium spp. colonies were obtained from all root samples. Ten pure cultures were obtained by single-spore culturing (Ff01 to Ff10). On PDA the colonies were abundant with white aerial mycelium, hyphae were branched and septae and light purple pigmentation was observed in the center of old cultures (Leslie and Summerell 2006). From 10-day-old cultures grown on carnation leaf agar medium, macroconidias were falciform, hyaline, with slightly curved apexes, three to five septate, with well-developed foot cells and blunt apical cells, and measured 26.6 to 45.8 × 2.2 to 7.0 μm (n = 40). The microconidia (n = 40) were hyaline, one to two celled, produced in false heads that measured 7.4 to 20.1 (average 13.7) μm × 2.4 to 8.9 (average 5.3) μm (n = 40) at the tips of long monophialides, and were oval or reniform, with apexes rounded, 8.3 to 12.1 × 1.6 to 4.7 μm; chlamydospores were not evident. These characteristics fit those of the Fusarium solani (Mart.) Sacc. species complex, FSSC (Summerell et al. 2003). The internal transcribed spacer and the translation elongation factor 1 alpha (EF1-α) genes (O’Donnell et al. 1998) were amplified by polymerase chain reaction and sequenced from the isolate Ff02 and Ff08 (GenBank accession nos. KJ501093 and MN082369). Maximum likelihood analysis was carried out using the EF1-α sequences (KJ501093 and MN082369) from the Ff02 and Ff08 isolates and other species from the Fusarium solani species complex (FSSC). Phylogenetic analysis revealed the isolate most closely related with F. falciforme (100% bootstrap). For pathogenicity testing, a conidial suspension (1x106 conidia/ml) was prepared by harvesting spores from 10-days-old cultures on PDA. Twenty 2-week-old chickpea seedlings from two cultivars (P-2245 and WR-315) were inoculated by dipping roots into the conidial suspension for 20 min. The inoculated plants were transplanted into a 50-hole plastic tray containing sterilized soil and maintained in a growth chamber at 25°C, with a relative humidity of >80% and a 12-h/12-h light/dark cycle. After 8 days, the first root rot symptoms were observed on inoculating seedlings and the infected plants eventually died within 3 to 4 weeks after inoculation. No symptoms were observed plants inoculated with sterilized distilled water. The fungus was reisolated from symptomatic tissues of inoculated plants and was identified by sequencing the partial EF1-α gene again and was identified as F. falciforme (FSSC 3 + 4) (O’Donnell et al. 2008) based on its morphological characteristics, genetic analysis, and pathogenicity test, fulfilling Koch’s postulates. The molecular identification was confirmed via BLAST on the FusariumID and Fusarium MLST databases. Although FSSC has been previously reported causing root rot in chickpea in USA, Chile, Spain, Cuba, Iran, Poland, Israel, Pakistan and Brazil, to our knowledge this is the first report of root rot in chickpea caused by F. falciforme in Mexico. This is important for chickpea producers and chickpea breeding programs.

scholarly journals First Report of Powdery Mildew Incited by Erysiphe heraclei on English Ivy (Hedera helix) in Italy

Plant Disease ◽  
2008 ◽  
Vol 92 (2) ◽  
pp. 313-313 ◽  
Author(s):  
A. Garibaldi ◽  
D. Bertetti ◽  
J. Rossi ◽  
M. L. Gullino
Keyword(s):  
Nucleotide Sequence ◽  
Powdery Mildew ◽  
Its Region ◽  
The United States ◽  
Tube Length ◽  
Herbarium Specimens ◽  
Pathogenicity Test ◽  
Hedera Helix ◽  
First Report ◽  
Germ Tubes

Hedera helix L. (Araliaceae) is a common ornamental species that is able to grow in shaded areas and is often used in parks and gardens. During the fall of 2006, severe outbreaks of a previously unknown powdery mildew were observed in several gardens in Liguria (northern Italy). Both surfaces of young leaves of affected plants were covered with dense, white mycelia and conidia. As the disease progressed, infected leaves turned yellow and dropped. Mycelia and conidia were also observed on young stems. Conidia were hyaline, cylindrical, borne singly, and measured 38 to 51 × 12 to 18 (average 42 × 16) μm. Single germ tubes, moderately long (average 26 μm), developed at the end of conidia. Appressoria of germ tubes and hyphae were lobed (three to four lobes). Conidiophores, 68 to 82 × 7 to 8 (average75 × 8) μm, showed foot cells measuring 39 to 60 × 7 to 8 (average 52 × 8) μm, followed by one shorter cell measuring 19 to 28 × 8 to 9 (average 23 × 9) μm. Fibrosin bodies were absent. Chasmothecia were numerous, spherical, amber-colored then brown at maturity, with diameters ranging from 97 to 140 (average 120) μm, containing four asci shortly stalked, 57 to 72 × 32 to 51 (average 65 × 41 μm). Ascospores were ellipsoid and measured 24 to 34 × 15 to 20 (average 30 × 17) μm. The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS4/ITS6 and sequenced. BLASTn analysis (1) of the 613-bp fragment showed an E-value of 0.0 with Erysiphe heraclei. The nucleotide sequence has been assigned GenBank Accession No. EU 010381. In GenBank, our nucleotide sequence shows an E-value of 0.0 also with E. betae. However, the comparison of appressorium shape and germ tube length observed on our microorganism with those described for E. betae by Braun (2) suggests that the causal agent of the powdery mildew reported on ivy is E. heraclei. Furthermore, symptoms described on our host, appressorium shape and the length of conidiophores, are different from those of Oidium araliacearum described by Braun (2) on Araliaceae. Inoculations were made by gently pressing diseased leaves onto leaves of five healthy H. helix plants. Three noninoculated plants served as controls. Inoculated and noninoculated plants were maintained in a greenhouse at temperatures between 21 and 25°C. After 15 days, typical powdery mildew colonies developed on inoculated plants. Noninoculated plants did not show symptoms. The pathogenicity test was carried out twice. To our knowledge, this is the first report of the presence of powdery mildew on H. helix caused by E. heraclei in Italy. A powdery mildew caused by E. cichoracearum was previously reported on H. canariensis var. azorica in Italy (3), while a powdery mildew on H. helix caused by O. araliacearum and Golovinomyces orontii, respectively, were observed in the United States (4) and Germany. Herbarium specimens of this disease are available at AGROINNOVA Collection, University of Torino, Italy. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) U. Braun. A Monograph of the Erysiphaceae (Powdery Mildews). Cramer, Berlin, Germany, 1987. (3) C. Nali. Plant Dis. 83:198, 1999. (4) G. S. Saenz and S. T. Koike. Plant Dis. 82:127, 1998.

scholarly journals First Report of Root Rot Caused by Pythium spiculum Affecting Cork Oaks at Doñana Biological Reserve in Spain

Plant Disease ◽  
2013 ◽  
Vol 97 (7) ◽  
pp. 991-991 ◽  
Author(s):  
P. De Vita ◽  
M. S. Serrano ◽  
C. Ramo ◽  
C. Aponte ◽  
L. V. García ◽  
...  
Keyword(s):  
Root Rot ◽  
Phytophthora Cinnamomi ◽  
Quercus Suber ◽  
First Report ◽  
Root Necrosis ◽  
Pathogenicity Tests ◽  
Branch Dieback ◽  
The University ◽  
Virulence Group ◽  
Biological Reserve

Cork oaks (Quercus suber L.) are key tree species at Doñana Biological Reserve (DBR), Huelva, Spain. Sampling was conducted on a total of 13 trees exhibiting symptoms of decline (foliar wilting and defoliation, branch dieback, and root necrosis). In 2008. Phytophthora cinnamomi was isolated from feeder roots of one tree and Pythium spiculum from two additional oaks. In 2011, both pathogens were isolated from six oaks, only P. cinnamomi from three oaks, and only Py. spiculum from one oak. This expansion was associated with high winter rainfall levels since 2009 that led to long periods of soil flooding. While P. cinnamomi is well known to cause a root disease on Q. suber (2), P. spiculum is a newly described species isolated from Quercus, Vitis, Prunus, Castanea, and Celtis species, but its pathogenicity was demonstrated only on Q. ilex (syn. Q. rotundifolia) (1). Pathogenicity tests were conducted on 4-year-old Q. suber plants. Inocula consisted of two isolates of Py. spiculum from DBR (DO8 and DO36 from Q. suber). For comparison with these, three isolates previously tested on Q. ilex (1) were included: two isolates of Py. spiculum, PA54 (from Q. suber) and PE156 (from Q. ilex); and one isolate of P. cinnamomi, PE90 (from Q. ilex). All these isolates came from the Andalucía region, stored at the oomycete collection of the University of Córdoba, and showed a 99 to 100% homology with their expected ITS sequences in GenBank (DQ196131 for Py. spiculum and AY943301 for P. cinnamomi). Inoculum was prepared by shaking and mixing propagule-bearing mycelium produced in carrot broth petri dishes (20°C, 4 weeks) in sterile water, to produce a concentration of 3 × 104 oospores × ml−1 (Py. spiculum) or 3 × 104 chlamydospores × ml−1 (P. cinnamomi). One hundred milliliters of inoculum was applied to each root (1). There were 10 inoculated plants per isolate and 10 non-inoculated control plants. All plants were waterlogged 2 days per week to favor root infection and maintained in an acclimatised greenhouse (12–28°C). Three months later, the inoculated plants showed symptoms of root necrosis that resulted in foliar wilting followed occasionally by defoliation. Control plants did not develop foliar symptoms nor root necrosis. Root damage severity assessed on a 0 to 4 scale (3) exhibited significant differences (P < 0.05) in relation to the control plants for all the isolates tested, with isolate PE90 (P. cinnamomi) and isolates PA54, DO8, and DO36 (P. spiculum) all averaging a root necrosis value of 2.5. Isolate PE156 of P. spiculum produced values of root necrosis (1.6 in average) significantly lower (P < 0.05) than the rest. This isolate belongs to the low virulence group of P. spiculum described on Q. ilex (1). The inoculated oomycete was always reisolated from necrotic roots and never from roots of control plants. To the best of our knowledge, this is the first report of P. spiculum as the cause of root rot of Q. suber. References: (1) Romero et al. J. Phytopathol. 155:289, 2007. (2) Sánchez et al. For. Pathol. 32:5, 2002. (3) Sánchez et al. For. Pathol. 35:115, 2005.

scholarly journals First Report of Brown Root Rot on Alfalfa Caused by Phoma sclerotioides in the Continental United States

Plant Disease ◽  
1999 ◽  
Vol 83 (11) ◽  
pp. 1071-1071 ◽  
Author(s):  
C. R. Hollingsworth ◽  
F. A. Gray
Keyword(s):  
United States ◽  
Root Rot ◽  
Experimental Unit ◽  
Diseased Plant ◽  
Pathogenicity Test ◽  
Forage Crops ◽  
First Report ◽  
Severity Rating ◽  
Phoma Sclerotioides ◽  
Brown Root Rot

Phoma sclerotioides G. Preuss ex Sacc. (previously named Plenodomus meliloti Dearn. & G.B. Sanford) is associated with root rot and extensive winterkill of leguminous forage crops, such as clover (Trifolium and Melilotus spp.), sainfoin (Onobrychis viciifolia), and alfalfa (Medicago sativa). Winterkill and root rot of irrigated alfalfa were observed for the first time in a field of cv. Multiplier in western Wyoming during the spring of 1996. Dark brown to black, sunken, rotting lesions were noted on upper secondary roots and taproots of dead and living diseased plants. Superficial and embedded beaked pycnidia and pycnosclerotia were observed near root lesions. A Phoma sp. isolated from a diseased plant in Farson, WY, was maintained on potato dextrose and half-strength V8-juice agars. Beaked pycnidia, typical of P. sclerotioides, were observed in culture when grown at 10°C for 2 months. A pathogenicity test was performed on cv. Multiplier. Two barley seeds colonized by a Phoma sp. derived from a Wyoming isolate were positioned on taproots of healthy, greenhouse-grown, 5-month-old plants ≈2.5 cm below the crown and were covered with a small piece of sterile cotton. Three replicate samples (24 plants inoculated and 24 plants uninoculated per replicate) were winter-hardened for 4 weeks (15.6°C/10°C, day/night, for 2 weeks, followed by 10°C/7.2°C, day/night, for 2 weeks) and placed outside during January 1998 in Laramie, WY, for a 4-month winter exposure period. Plants were rated for disease during June 1998. A disease severity rating of 1 to 5 was assigned to each experimental unit, where 1 = no disease and 5 = dead plant. The percentage of diseased plants at each severity rating for all inoculated plants was 1 = 19%, 2 = 33%, 3 = 31%, 4 = 13%, and 5 = 4%. Mycelium typical of P. sclerotioides was found on 99% of inoculated plant roots whether or not they had pycnidia. Pycnidia were found on the lower stems and petioles of some inoculated plants. Three percent of control plants also developed brown root rot (BRR) symptoms (taproot lesions or discoloration) by June 1998. The percentage of diseased plants at each severity rating for all uninoculated plants was 1 = 96%, 2 = 4%, and 3 through 5 = 0%. Aboveground propagule placement likely contributed to the spread of BRR by raindrop splash and wind-driven plant debris to adjacent alfalfa. Most inoculated plants had immature pycnidia or protopycnidia (94%), whereas 6.9% of the plants also had fully mature, beaked pycnidia. Pure fungal cultures were obtained from several diseased roots and compared with the original Wyoming Phoma sp. culture and a Canada isolate of P. sclerotioides (ATCC no. 56515) (2): colony, pycnidial, and conidial morphologies were identical, completing Koch's postulates. This is the first report of BRR on alfalfa in the continental United States. References: (1) J. G. N. Davidson. 1990. Brown root rot. Pages 29–31 in: Compendium of Alfalfa Disease. 2nd ed. The American Phytopathological Society, St. Paul, MN. (2) C. R. Hollingsworth et al. Phytopathology 88(suppl.):S39, 1999.

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