scholarly journals First Report of Stem Rot of Guiana Chestnut (Pachira aquatica) Caused by Pythium splendens

Plant Disease ◽  
2004 ◽  
Vol 88 (1) ◽  
pp. 84-84 ◽  
Author(s):  
M. Tojo ◽  
K. Kuroda ◽  
H. Suzuki
Keyword(s):  
Tap Water ◽  
Stem Rot ◽  
Vascular Bundles ◽  
Centraalbureau Voor ◽  
First Report ◽  
Potted Plants ◽  
Tropical Plant ◽  
Pythium Splendens ◽  
Rdna Sequences ◽  
Mycelial Suspension

Guiana chestnut is a perennial tropical plant that has recently become popular as a potted ornamental in Japan. In October 2001, severe stem rot occurred on Guiana chestnut plants grown in a greenhouse in Mie Prefecture, Japan. Water-soaked lesions appeared initially at the base of the stems and enlarged gradually toward the tops of plants. The affected tissues were softened and turned dark brown. Rotting was observed in the vascular bundles with advanced disease development. Globose hyphal swellings were numerous on diseased stems. Sections from diseased stems were cleaned by washing with running tap-water, placed on water agar, and incubated at 25°C. A species of Pythium was identified on the basis of morphological and cultural characteristics (1) and isolated consistently from the rotted stems of diseased plants. All isolates produced abundant hyphal swellings that were globose, smooth, 12 to 39 μm in diameter, mostly terminal, dark colored, and with dense granulated contents. Zoospores were absent. All isolates were of the compatibility ‘+ type’ with production of sexual organs when paired with cultures of the ‘- type’ tester isolate of Pythium splendens Braun (CBS462.48). Oogonia produced by crossings between Guiana chestnut isolates and isolate CBS462.48 were terminal or intercalary, globose, smooth-walled, and 32 to 38 μm in diameter. Antheridia were terminal, one to three per oogonium, sac-like, and diclinous. Oospores were single, aplerotic, globose, and 28 to 32 μm in diameter. The thickness of the oospore wall ranged from 1 to 2 μm. The internal transcribed spacer rDNA sequences of representative isolate OPU591 from Guiana chestnut matched those of CBS462.48 (similarity 99.2%) and have been deposited in GenBank under the Accession No. AY375242. Pathogenicity tests were conducted on potted Guiana chestnut plants (30 cm high and 7 to 10 cm in diameter at base of the stem) using isolate OPU591. A mycelial suspension from one culture, grown at 25°C for 7 days on water agar, was inoculated onto a single plant. Prior to inoculation, a wound (10 mm deep and 30 mm long) was made on the surface at the stem base on five plants. The mycelial suspension was poured onto the base of the stems of five wounded and five nonwounded plants. In addition, five wounded and five nonwounded, noninoculated plants were used as controls. Plants were maintained in a greenhouse for 8 weeks after inoculation. The temperature and relative humidity in the greenhouse ranged from 25 to 30°C and 65 to 75%, respectively. Dark-brown rotting developed on the stems of all wounded, inoculated plants by 20 days after inoculation. P. splendens was isolated from diseased tissues and found to be morphologically identical to the original isolate. This confirmed P. splendens as the causal agent of the disease. Disease did not develop on nonwounded inoculated plants or noninoculated plants. To our knowledge, this is the first report of P. splendens on Guiana chestnut. Potted plants of Guiana chestnut are often injured by frequent transplanting and transferring. Such injuries may have predisposed the plant to infection by P. splendens. Reference: (1) A. J. van der Plaats-Niterink. Page 1 in: Monograph of the Genus Pythium. Studies in Mycology Vol. 21, Centraalbureau Voor Schimmelcultures, Baarn, the Netherlands, 1981.

scholarly journals First Report of Stem Blight on Perilla (Perilla frutescens) Caused by Corynespora cassiicola in Korea

Plant Disease ◽  
2009 ◽  
Vol 93 (5) ◽  
pp. 550-550 ◽  
Author(s):  
H. B. Lee ◽  
C. J. Kim ◽  
H. Y. Mun
Keyword(s):  
Perilla Frutescens ◽  
Morphological Data ◽  
Conidial Suspension ◽  
Corynespora Cassiicola ◽  
Cucumis Sativus L ◽  
First Report ◽  
Potted Plants ◽  
Rdna Sequences ◽  
Pathogenicity Tests ◽  
Stem Lesions

Perilla or kkaennip (Perilla frutescens (L.) Britton), an annual herb of the mint family, Lamiaceae, is used in salads and kimchi and for wrapping sliced raw fish. In September 2007, a disease occurred on greenhouse-produced perilla (cv. Manchu) in Gwangyang and Jeonnam provinces, Korea. Symptoms included leaf blight and irregularly shaped stem lesions approximately 1 to 3 cm long. Plants eventually died. In some greenhouses, 10 to 30%, and occasionally as much as 70%, of the plants were affected. Isolations on potato dextrose agar yielded a fungus with single conidiophores (439 to 656 [average 524] μm long × 6.2 to 11.6 [average 9.2] μm wide) with three to eight septa. Conidia were fusiform, obclavate to subcylindrical, straight or curved, and 30.4 to 180.1 (average 98.2) μm long × 6.7 to 18.1 (average 10.5) μm wide with 5 to 16 (commonly 13) distosepta. On the basis of morphological data and ITS rDNA sequences, the fungus was identified as Corynespora cassiicola (Berk. & Curt.) Wei. (1,2). Sequences of one isolate, EML-COR1, were more than 99% identical to sequences of C. cassiicola ATCC64204 (GenBank Accession No. AY238606) and C. cassiicola (GenBank Accession No. EF490450). In pathogenicity tests, the stems and leaves of two 2-month-old wounded and nonwounded potted plants (cv. Manchu) were sprayed until runoff with a conidial suspension of 5 × 104 conidia per ml. The plants were maintained for 48 h in a humid chamber and then moved to a greenhouse. Symptoms similar to those observed in the commercial greenhouse developed on wounded stems within 10 days. On nonwounded plants, symptoms developed 3 to 4 weeks after inoculation. C. cassiicola was reisolated from these lesions. Control plants (sprayed with distilled water) remained symptomless. The experiment was repeated with similar results. Although C. cassiicola causes blight of cucumber (Cucumis sativus L.), sesame (Sesamum indicum L.), and other crops, to our knowledge, this is the first report of C. cassiicola on perilla. References: (1) M. B. Ellis. Page 372 in: Dematiaceous Hyphomycetes. 1971. (2) J. L. D. Silva et al. Plant Pathol. 55:580, 2006.

scholarly journals First Report of Diaporthe amygdali Associated with Twig Canker and Shoot Blight of Nectarine in Spain

Plant Disease ◽  
2021 ◽  
Author(s):  
Francisco Beluzán ◽  
Diego Olmo ◽  
Maela León ◽  
Paloma Abad-Campos ◽  
Josep Armengol
Keyword(s):  
Prunus Persica ◽  
Tap Water ◽  
Elongation Factor ◽  
Its Region ◽  
Sodium Hypochlorite Solution ◽  
First Report ◽  
Potted Plants ◽  
Randomized Design ◽  
Shoot Blight ◽  
One Year

Nectarine (Prunus persica (L.) Batsch var. nucipersica (Suckow) C. K. Schneid.) is a fruit crop widely cultivated throughout the Mediterranean basin. In Spain, it is mainly grown in eastern regions of the country. In March 2018, 5-year-old nectarine trees showing twig canker symptoms were observed after a rainy spring period in a 0.5 ha orchard located at Alaior, Menorca island (Spain). Cankers were frequent on affected trees (approximately, 80% of the total trees), thus leading to shoot blight. Ten twig segments of one-year old wood with cankers were cut, washed under running tap water, surface disinfected for 1 min in a 1.5% sodium hypochlorite solution and rinsed twice in sterile distilled water. Small pieces (2 mm) of affected tissues were taken from the margin of the cankers and plated on potato dextrose agar (PDA) supplemented with 0.5 g/L of streptomycin sulphate (PDAS). The plates were then incubated at 25 ºC in the dark for 7 to 10 d. Actively growing colonies were first hyphal-tipped and then transferred to PDA and 2% water agar supplemented with sterile pine needles and incubated at 21-22ºC under a 12h/12h near UV / darkness cycle during 21 d (León et al. 2020). Colonies were white at first, becoming light cream, with visible solitary and aggregate pycnidia at maturity. Alpha conidia were aseptate, fusiform, hyaline, multi-guttulated (mean ± SD = 7.4 ± 0.7 × 2.8 ± 0.4 µm, n = 100). Beta and gamma conidia were not observed. The morphological and cultural characteristics of the isolates were congruent with those of Diaporthe spp. (Gomes et al. 2013). The ITS1-5.8S-ITS2 (ITS) region and fragments of β-tubulin (tub2), the translation elongation factor 1-alpha (tef1-α) gene regions, histone H3 (his3) and calmodulin (cal) genes of representative isolate DAL-59 were amplified and sequenced (Santos et al. 2017). The BLASTn analysis revealed 100% similarity with sequences of D. mediterranea (Synonym D. amygdali) (Hilário et al. 2021) isolate DAL-34 from almond (ITS: MT007489, tub2: MT006686, tef1-α: MT006989, his3: MT007095 and cal: MT006761). Sequences of isolate DAL-59 were deposited in GenBank Database (ITS: MT007491, tub2: MT006688, tef1-α: MT006991, his3: MT007097 and cal: MT006763). Pathogenicity tests were conducted using one-year-old potted plants of nectarine cv. Boreal, which were inoculated with isolate DAL-59. In each plant, a 3 mm wound was made in the center of the main branch (about 30 cm length) with a scalpel. Colonized agar plugs with 3 mm diameter, which were obtained from active 10-day-old colonies growing on PDA, were inserted underneath the epidermis and the wounds sealed with Parafilm. Inoculated plants were incubated in a growth chamber at 23 ºC with 12 h of light per day. Controls were inoculated with uncolonized PDA plugs. There were twelve plants per treatment, which were arranged in a completely randomized design. Five days after inoculation necrosis development was observed in the area of inoculation. Wilting and twig blight symptoms over the lesion occurred 3-wk after inoculation and pycnidia were detected, while the controls remained asymptomatic. Diaporthe amygdali was re-isolated from symptomatic tissues and identified as described above to satisfy Koch’s postulates. To our knowledge, this is the first report of D. amygdali causing twig canker and shoot blight disease on nectarine in Spain.

scholarly journals First Report of the Pathogenicity of Rhizoctonia solani on Salvinia molesta and S. minima in Florida

Plant Disease ◽  
2002 ◽  
Vol 86 (7) ◽  
pp. 813-813
Author(s):  
M. B. Rayachhetry ◽  
T. R. Center ◽  
T. D. Center ◽  
P. Tipping ◽  
P. D. Pratt ◽  
...  
Keyword(s):  
Rhizoctonia Solani ◽  
Native Species ◽  
Tap Water ◽  
Tween 80 ◽  
Fluorescent Light ◽  
Distilled Water ◽  
Salvinia Molesta ◽  
Potato Dextrose Broth ◽  
First Report ◽  
Mycelial Suspension

Salvinia molesta Mitchell (giant salvinia) and S. minima Baker (common salvinia) are exotic aquatic ferns that have invaded drainage basins in Texas, Louisiana, Alabama, Arizona, California, Florida, Georgia, Hawaii, Mississippi, North Carolina, and Oklahoma (2). These ferns rapidly colonize bodies of water and form thick mats, displace native species, disrupt recreational activities like boating and fishing, block drainage and irrigation intakes, interfere with electricity generation, and degrade water quality (1). Patches of water-soaked lesions were observed on the pinnules and rachises of screenhouse-grown S. molesta plants in Florida. Mycelia spread centrifugally from these patches and caused diseased plants to disintegrate and sink. Brown-to-black sclerotia were formed on and around the disintegrated plants. A fungus was consistently isolated from symptomatic tissues of S. molesta plants. Seven-day-old cultures turned buff-colored and produced sclerotia on potato dextrose agar, while cultures on water agar were hyaline and produced black sclerotia. Both types of sclerotia were not differentiated into rind and medulla. The mycelia branched at right angles from the main hyphae, were constricted at the base of the angle, and had a septum after the constriction. Vegetative cells were multinucleate. The fungus was identified as Rhizoctonia solani Kühn (3,4). Koch's postulates were performed to confirm pathogenicity on S. molesta and S. minima. Seven-day-old cultures of R. solani that were grown in potato dextrose broth were filtered through four layers of cheesecloth and washed with distilled water. Fourteen grams of the mycelial residue was suspended in 28 ml of distilled water and macerated in a small blender for 30 s to obtain a mycelial suspension. Healthy S. molesta and S. minima plants grown in screenhouse-tanks were immersed in tap water supplemented with 1 drop per 4 liters of surfactant (Tween 80), rinsed thoroughly, and approximately 40 g of the plants was floated in plastic jars (18.5 cm diameter × 7.5 cm high) filled to a depth of 5 cm with tap water. Three jars each of S. molesta and S. minima were misted with 1.5 ml of the mycelial suspension. Individual jars were covered with a clear plastic lid with a 2.5-cm-diameter hole in the center for ventilation. These jars were placed in a growth chamber maintained at 28 (+1)°C and 12-h fluorescent light cycles. Typical water-soaked lesions appeared on pinnules within 3 to 7 days, spread rapidly, and resulted in disintegration of pinnules and rachises. R. solani was consistently reisolated from symptomatic tissues of both Salvinia species. To our knowledge, this is the first report confirming pathogenicity of R. solani on S. molesta and S. minima. This fungus should be further evaluated as a potential mycoherbicide for control of Salvinia species. References: (1) K. L. S. Harley and D. S. Mitchell. J. Aust. Inst. Agric. Sci. 47:67, 1981. (2) C. C. Jacono et al. Castanea 66:214, 2001. (3) B. Sneh et al. Identification of Rhizoctonia Species. The American Phytopathological Society, St. Paul, MN, 1991. (4) C. C. Tu and J. W. Kimbrough. Bot. Gaz. 139:454, 1978.

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

Plant Disease ◽  
2009 ◽  
Vol 93 (8) ◽  
pp. 843-843 ◽  
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.

scholarly journals First Report of Septoria apocyni Causing Spot Blight on the Species of Apocynum venetum and Poacynum pictum in China

Plant Disease ◽  
2014 ◽  
Vol 98 (10) ◽  
pp. 1429-1429 ◽  
Author(s):  
P. Gao ◽  
T. Y. Duan ◽  
Z. B. Nan ◽  
P. J. O'Connor
Keyword(s):  
Tap Water ◽  
Disease Incidence ◽  
Relevant Literature ◽  
Fungal Mycelium ◽  
Infected Leaf ◽  
Colorless Needle ◽  
Literature Report ◽  
First Report ◽  
Apocynum Venetum ◽  
Mycelial Suspension

The species of Apocynum venetum and Poacynum pictum grow widely from the middle to northwestern regions of China. During the summers of 2011 to 2013, a spot blight was found in wild and cultivated both species in Altay Prefecture of the Xinjiang Uygur Autonomous Region, China. The spot blight caused leaf yellowing and leaf drop, and serious damage to plant phloem. Lesions were circular to irregular, and the diameter of lesions on A. venetum and P. pictum was 1.84 to 6.84 × 1.23 to 4.24 mm and 2.05 to 7.09 × 1.46 to 5.65 mm, respectively. Pycnidia were 70 to 115 × 52 to 120 μm, scattered, spherical, buried, and had a brown hard shell with a prominent ostiole. Conidia were colorless, needle-shaped, or linear. The conidia base was obtuse, containing 3 to 5 indistinct septa, 46.3 to 110.3 × 2 to 2.5 μm. Fungal cultures were obtained by cutting 1-cm-long infected leaf pieces from the margins of the lesions following routine surface sterilizing procedures. The sections were placed on potato dextrose agar (PDA) in petri dishes and incubated at 23°C for 4 weeks (4). Hyphae had septa, the aerial and base mycelium was white and rufous, and the back of the colony was sunken and cracked after 2 weeks, but no spore was observed. To verify the identity, total DNA was extracted directly from fungal mycelium with a UNIQ-10 fungal genomic DNA extraction kit (Sangon Biotech, Shanghai, China) and PCR amplification performed with primers ITS1/ITS4 (3). A 512-bp PCR product was sequenced and contrasted with GenBank sequences using BLAST, which revealed 99% identity with Septoria sp. (GenBank Accession No. KC134322.1). To confirm pathogenicity, A. venetum and P. pictum were planted in pots and grown in a greenhouse. After 6 weeks of growth, plants were inoculated by spraying a mycelial suspension onto the foliage while control plants received a similar application of sterilized distilled water. Five pots (3 plants per pot) were used for each treatment. The pots were then placed on plates filled with tap water and covered with Plexiglas hoods in the greenhouse at 20 to 25°C. Lesions began to appear 6 to 7 days after inoculation with the mycelial suspension, whereas control plants remained healthy. The average disease incidence was 19.3%. The symptoms and morphology were similar to Septoria apocyni in Teterevnikova (2). It was determined that spot blight of A. venetum and P. pictum was caused by S. apocyni based on morphological comparison. There is one relevant literature report of spot blight on A. venetum and P. pictum in China, but without any details of the pathogenicity or morphology of the pathogen (1). We believe that this is the first report of S. apocyni occurring on the species of A. venetum and P. pictum in China. References: (1) W. Sun et al. Special Economic Animal and Plant 8:23, 2005. (2) D. N. Teterevnikova. Page 79 in: Septoria sp. Fungus of USSR. Armenian Academy of Sciences Publishing, Armenia, USSR, 1987. (3) G. J. M. Verkley et al. Mycologia 96:558, 2004. (4) W. Zhang et al. Plant Dis. 96:1374, 2012.

scholarly journals First Report of Phytophthora cactorum Causing Fruit Rot on Avocado in Spain

Plant Disease ◽  
2005 ◽  
Vol 89 (12) ◽  
pp. 1363-1363
Author(s):  
C. J. López-Herrera ◽  
R. M. Pérez-Jiménez ◽  
T. Zea-Bonilla
Keyword(s):  
Tap Water ◽  
Pathogenic Fungi ◽  
Persea Americana ◽  
Southern Spain ◽  
Fruit Rot ◽  
Sterile Water ◽  
Phytophthora Cactorum ◽  
First Report ◽  
Apical Necrosis ◽  
Mycelial Suspension

The area of avocado (Persea americana Mill.) orchards in southern Spain has increased recently and is currently at 8,063 ha. Avocado production in this part of Spain was 72,581 t during 2003. During February 2004, apical necrosis was observed on avocado fruits (cv. Hass) in one orchard in Vélez-Málaga, Málaga Province, southern Spain. Dark brown lesions and necrotic flecking of the flesh also were observed on fruits. Isolations from the skin of the fruit previously washed with tap water and disinfested with 20% sodium hypochlorite on potato dextrose agar (PDA) consistently resulted in mycelial colonies. Sporangia produced on V8 juice by successive washing of mycelia with saline solution (1) measured 31 to 37.2 (33.3) × 21.7 to 28.8 (24.2) μm in size. The pathogen was identified as Phytophthora cactorum on the basis of morphological structures (mycelia, sporangia, chlamydospores, and oospores) formed when grown on V8 juice and PDA (2). To confirm pathogenicity, a mycelial suspension was obtained by blending mycelia grown for 1 week on PDA in 200 ml of sterile water. Three healthy avocado fruits were inoculated with the suspension by injection; three other fruits were inoculated by placing a drop of suspension on the unbroken skin of the fruit. The same number of fruit was inoculated as controls using sterile water instead of mycelial suspension. The inoculated fruits were incubated for 5 days in a moist chamber at 24°C in darkness. Spots appeared on all fruits for both inoculation methods, and the pathogen was isolated and identified as P. cactorum. No symptoms appeared on the control fruits. To our knowledge, this is the first report of P. cactorum causing fruit rot on avocado in Spain. References: (1) D. Chen and G. A. Zentmeyer. Mycologia 62:397, 1970. (2) G. M. Waterhouse and J. M. Waterston. No. 111 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1966.

scholarly journals First Report of Downy Mildew on Nursery-Grown Hellebore Caused by Peronospora pulveracea in California

Plant Disease ◽  
2009 ◽  
Vol 93 (3) ◽  
pp. 319-319 ◽  
Author(s):  
C. Y. Warfield ◽  
C. L. Blomquist ◽  
E. E. Lovig
Keyword(s):  
Downy Mildew ◽  
The United States ◽  
Early Spring ◽  
Economic Losses ◽  
Late Winter ◽  
Internal Transcribed Spacer Region ◽  
First Report ◽  
Potted Plants ◽  
Rdna Sequences ◽  
Young Leaves

Hellebore or Lenten rose (Helleborus × hybridus) is an evergreen, herbaceous perennial in the family Ranunculaceae. Hellebores are sold as decorative, potted plants and as shade-loving landscape plants favored for their attractive and prolonged blooms in late winter or early spring. In April of 2008, downy mildew-like growth was observed on the foliage of approximately 60 containerized plants of Helleborus ‘Blue Lady’, ‘Pink Lady’, ‘White Lady’, and ‘Royal Heritage’ grown outdoors in a retail nursery in coastal San Mateo County, California. Infected foliage had angular, vein-delimited, dark brown-to-black speckled lesions on adaxial leaf surfaces turning dry and necrotic with age. Young leaves were small and distorted. Affected flowers were spotted and brown. The abaxial sides of affected leaves had light brown-to-purplish downy mildew-like growth. Subhyaline conidia, globose to ellipsoid in shape, ranged from 25 to 31 × 17 to 24 μm (average 28 × 21 μm). Conidiophores ranged from 265 to 375 × 5 to 11.5 μm (average 333 × 8.9 μm), branching dichotomously four to five times in the upper half. Morphological measurements fell within the range previously described for Peronospora pulveracea and P. alpicola, which were reported on Helleborus spp. and Ranunculus aconitifolius, respectively (1,2). DNA sequence of the internal transcribed spacer region of rDNA of our isolate (Genbank Accession No. FJ384778) matched sequences of P. pulveracea (Genbank Accession No. AY198270) and P. alpicola (Genbank Accession No. AY198271) with 100% identity. These two organisms are taxonomically indistinguishable by rDNA sequences and are likely to be the same species (3). To our knowledge, this is the first report of P. pulveracea on Helleborus × hybridus in California and the United States. Lenten rose is commercially propagated by seed, which is a potential pathway for introduction of this pathogen. Mature plants are sold and shipped intra- and interstate as decorative flowering plants or nursery stock. The importance and economic impact of this disease is limited, but significant economic losses could occur during production. References: (1) E. A. Gäumann. Beitr. Kryptogamenflora Schweiz 5:113, 1923. (2) G. Hall. Mycopathologia 126:57, 1994. (3) H. Voglmayr. Mycol. Res. 107:1132, 2003.

scholarly journals First Report of Phaeoacremonium mortoniae Causing Petri Disease of Grapevine in Spain

Plant Disease ◽  
2007 ◽  
Vol 91 (9) ◽  
pp. 1206-1206 ◽  
Author(s):  
D. Gramaje ◽  
S. Alaniz ◽  
A. Pérez-Sierra ◽  
P. Abad-Campos ◽  
J. García-Jiménez ◽  
...  
Keyword(s):  
Tap Water ◽  
Sodium Hypochlorite Solution ◽  
Malt Extract ◽  
Distilled Water ◽  
Conidial Suspension ◽  
Internal Transcribed Spacer Region ◽  
Fungal Isolation ◽  
Centraalbureau Voor ◽  
First Report ◽  
Grapevine Decline

In May 2006, symptoms of grapevine decline were observed on 4-year-old grapevines (cv. Cabernet Sauvignon) grafted onto 110 R rootstock in Daimiel (Ciudad Real Province, central Spain). Affected vines had low vigor, reduced foliage, and chlorotic leaves. Cross or longitudinal sections of the rootstock trunk showed black spots and dark streaking of the xylem vessels. Five symptomatic plants were collected and analyzed for fungal isolation. Sections (10 cm long) were cut from the basal end of the rootstocks, washed under running tap water, surface sterilized for 1 min in a 1.5% sodium hypochlorite solution, and washed twice with sterile distilled water. The sections were split longitudinally and small pieces of discolored tissues were plated onto malt extract agar (MEA) supplemented with 0.5 g L–1 of streptomycin sulfate. Plates were incubated at 25 to 26°C in the dark for 14 to 21 days and all colonies were transferred to potato dextrose agar (PDA). A Phaeoacremonium sp. was consistently isolated from necrotic tissues. Single conidial isolates were obtained and grown on PDA and MEA in the dark at 25°C for 2 to 3 weeks until colonies produced spores (3). Colonies were yellowish white on PDA and white-to-pale gray on MEA. Conidiophores were short and unbranched, 12.5 to 37.5 (20.5) μm long, and often consisting of a single subcylindrical phialide. Conidia were hyaline, oblong to ellipsoidal or reniform, 2.5 to 7.5 (4.6) μm long, and 1.2 to 1.9 (1.6) μm wide. On the basis of these characteristics, the isolates were identified as Phaeoacremonium mortoniae (2,3). Identity of isolate Pmo-1 was confirmed by PCR-restriction fragment length polymorphism of the internal transcribed spacer region (Phaeoacremonium-specific primers Pm1-Pm2) with the restriction enzymes BssKI, EcoO109I, and HhaI (1). Additionally, the β-tubulin gene fragment (primers T1 and Bt2b) of this isolate was sequenced (GenBank Accession No. EF517921). The sequence was identical to the sequence of P. mortoniae (GenBank Accession No. DQ173109). Pathogenicity tests were conducted on 2-month-old grapevine seedlings (cv. Tempranillo) using two isolates, Pmo-1 and a reference isolate of P. mortoniae (CBS-101585) obtained from the Centraalbureau voor Schimmelcultures (Utrecht, the Netherlands). Seedlings were inoculated when two to three leaves had emerged by watering the roots with 25 mL of a conidial suspension (106 conidia mL–1) harvested from 21-day-old cultures grown on PDA. Controls were inoculated with sterile distilled water. There were 20 replicates for each isolate with an equal number of uninoculated plants. Seedlings were maintained in a greenhouse at 23 to 25°C. Within 2 months after inoculation, symptoms developed as reduced growth, chlorotic leaves, severe defoliation, and finally wilting. Control plants did not show any of these symptoms. The fungus was reisolated from internal tissues of the crown area and the stems of all inoculated seedlings, completing Koch's postulates. To our knowledge, this is the first report of P. mortoniae causing young grapevine decline in Spain. References: (1) A. Aroca and R. Raposo. Appl. Environ. Microbiol. 73:2911, 2007. (2) M. Groenewald et al. Mycol. Res. 105:651, 2001. (3) L. Mostert et al. Stud. Mycol. 54:1, 2006.

scholarly journals First Report of Phytophthora taxon niederhauserii Causing Root and Stem Rot of Mimosa in Italy

Plant Disease ◽  
2013 ◽  
Vol 97 (5) ◽  
pp. 688-688 ◽  
Author(s):  
R. Faedda ◽  
S. O. Cacciola ◽  
A. Pane ◽  
P. Martini ◽  
M. Odasso ◽  
...  
Keyword(s):  
Mating Type ◽  
Consensus Sequence ◽  
Aerial Mycelium ◽  
Selective Medium ◽  
Phytophthora Species ◽  
Stem Rot ◽  
Basal Stem Rot ◽  
First Report ◽  
Acacia Dealbata ◽  
Potted Plants

Mimosa [Acacia dealbata Link, syn. Acacia decurrens (Wendl. F.) Wild. var. dealbata (Link) F. Muell., Fabaceae] is an evergreen shrub native to southeastern Australia that is cultivated as an ornamental plant in warm temperate regions of the world. In spring 2010, in a commercial nursery in Liguria (northern Italy), 6- to 10-month-old potted plants of A. dealbata showed symptoms of sudden collapse, defoliation, and wilt associated with root and basal stem rot. An abundant gum exudate oozed from the basal stem. A Phytophthora species was consistently isolated from roots and stem on BNPRAH selective medium (4). On V8 agar (V8A), axenic cultures obtained by single hyphal transfers formed stellate to radiate colonies with aerial mycelium whereas on potato dextrose agar (PDA) the colonies grew more slowly than on V8A and showed stoloniform mycelium and irregular margins. Minimum and maximum growth temperatures on PDA were 10 and 35°C, with the optimum at 30°C. In water, all isolates produced catenulate or single fusiform hyphal swellings and ellipsoid, nonpapillate, persistent sporangia. Dimensions of sporangia were 46.1 to 65.4 × 23.1 to 30.8 μm (mean l/b ratio 2.1). All isolates were A1 mating type and produced spherical oogonia with amphyginous antheridia when paired with A2 mating type of P. drechsleri Tucker on V8A plus β-sytosterol (4). Internal transcribed spacer (ITS) regions of rDNA of the representative Phytophthora isolate IMI 500394 from A. dealbata were amplified and sequenced in both directions with primers ITS6/ITS4. The consensus sequence (GenBank Accession No. JF900371) was 99% similar to sequences of several isolates identified as Phytophthora taxon niederhauserii Z.G. Abad and J.A. Abad (e.g., GQ848201 and EU244850). Pathogenicity tests were performed on 1-year-old potted plants of A. dealbata with isolate IMI 500394. Twenty plants were transplanted into pots (12-cm-diameter) filled with soil infested (4% v/v) with the inoculum of IMI500394 produced on kernel seeds. Plants were kept in a greenhouse with natural light at 25 ± 2°C and watered to field capacity weekly. All inoculated plants showed symptoms of wilt, leaf chlorosis, and basal stem rot within 3 to 4 weeks. Twenty control plants transplanted in autoclaved soil mix remained healthy. P. taxon niederhauserii was reisolated solely from inoculated plants, thus fulfilling Koch's postulates. Since 2003, this pathogen has been found on bottlebrush and rock rose grown in a nursery in Sicily (southern Italy), as well as on Banksia in a nursery in Liguria (2,3). To our knowledge, this is the first report of P. taxon niederhauserii on A. dealbata. P. taxon niederhauserii, recently described as P. niederhauserii sp. nov. (1), is a polyphagous pathogen that was originally reported on arborvitae and ivy in North Carolina in 2001. References: (1) Z. G. Abad et al. Mycologia (in press), 2013. (2) S. O. Cacciola et al. Plant Dis. 93:1075, 2009. (3) S. O. Cacciola et al. Plant Dis. 93:1216, 2009. (4) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996.

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