scholarly journals Epipremnum, a new host for Phytophthora capsici

Plant Disease ◽  
2002 ◽  
Vol 86 (9) ◽  
pp. 1050-1050 ◽  
Author(s):  
R. L. Wick ◽  
M. B. Dicklow
Keyword(s):  
Mating Type ◽  
Phytophthora Capsici ◽  
Crown Rot ◽  
Fluorescent Light ◽  
Pathogenicity Test ◽  
Agar Culture ◽  
New Host ◽  
Solid Media ◽  
Breadth Ratio ◽  
Response To Temperature

From 1999 to 2001, a Massachusetts nursery received a number of shipments of Pothos, Epipremnum aureum (Lindl. & André) Bunting, with significant crown, petiole, and leaf rot. The plants were imported from Costa Rica. Sporangia were observed on diseased tissues, and five presumptive isolates of Phytophthora were recovered from infected petioles and stems for species identification. The five isolates were morphologically indistinguishable from each other. Sporangia were produced in water and on V8 juice agar under fluorescent light at 22°C. Mating type was determined by pairing isolates with A1 and A2 mating types of Phytophthora capsici Leonian. Sporangial measurements were taken from water cultures. Determination of caducity, and measurements of pedicels and oospores were taken from V8 agar cultures. Measurements represent an average of 50 observations a single isolate. In water culture, sporangia were borne in umbellate clusters. Sporangium length/breadth was 48.29 and 22.33 μm respectively; length/breadth ratio 2.16. On solid media, sporangia were upright and caducous. The bases of the sporangia were mostly tapered. Pedicel lengths were 22 to 49 μm (average 35 μm). Oogonia had amphigynous antheridia and developed only in the presence of an opposite mating type, and oospores measured 25.74 μm diameter. All five isolates were the A1 mating type. Chlamydospores were absent in V8 and corn meal agar (CMA) cultures. Metalaxyl sensitivity was determined at 0, 0.1, 0.5, and 5 ppm in CMA with five replications. The isolate was completely sensitive to 5 ppm metalaxyl, but grew as well as the controls at 0.1 ppm metalaxyl. Growth response to temperature was determined on V8 agar at 15, 20, 25, 30, and 35°C in five replications. After 4 days, colony diameters at 20, 25, and 30°C were not significantly different (P = 0.01) and colonies filled the 100-mm petri dishes. At 15 and 35°C, average colony diameter was 65.7 and 71.4 mm, respectively. Based on the above characteristics, the isolates were identified as P. capsici. Koch's postulates were carried out on pepper, Capsicum annuum ‘Italia’, squash, Cucurbita pepo ‘Patty Pan’ seedlings, and rooted cuttings of pothos. Pepper and squash seedlings and rooted pothos were transplanted in 4-in. (10 cm) pots containing a soilless growing medium (Metro Mix 360, W.R. Grace, Columbia, MD). Phytophthora cultures were grown on V8 juice agar for 4 days. An agar culture was added to 200 ml of sterile distilled water and briefly blended. Ten milliliters of the resulting mycelial slurry were pipetted in the soil one cm from the crown on two sides of the plant. Controls received no mycelial slurry. Petiole, leaf, and crown rot of pothos developed within 2 weeks following inoculation. Squash and pepper plants did not become diseased. In a second pathogenicity test, a 1-cm-diameter plug of mycelial growth from a V8 agar culture was placed between the stem and petiole of the lowest leaf of pothos cuttings directly after transplanting. Inoculated plants died within 3 days. The development of umbellate clusters of sporangia, sporangial shape, length/breadth ratio, and lack of pathogenicity to pepper suggest that the P. capsici isolated from pothos belong to the CAPB (tropical) subgroup of Mchau and Coffey (2). References: (1) S. S. A. Al-Hedaithy and P. H. Tsao. Mycologia 71:392, 1979. (2) G. R. Mchau. and M. D. Coffey. Mycol. Res. 99:89, 1995.

scholarly journals First Report of Crown and Root Rot Caused by Phytophthora capsici on Hydroponically Grown Cucumbers in Norway

Plant Disease ◽  
2008 ◽  
Vol 92 (7) ◽  
pp. 1138-1138 ◽  
Author(s):  
M. L. Herrero ◽  
M. B. Brurberg ◽  
A. Hermansen
Keyword(s):  
Mating Type ◽  
Phytophthora Capsici ◽  
Crown Rot ◽  
Yield Reduction ◽  
Cox1 Gene ◽  
Pathogenicity Test ◽  
Internal Transcribed Spacer Region ◽  
First Report ◽  
Leaf Stage ◽  
Root And Crown Rot

In December 2004, symptoms of root and crown rot were observed on cucumbers (Cucumis sativus L.) in a greenhouse in Norway. Cucumbers were the only crop of the greenhouse that used rockwool as a growing substrate in a hydroponical system. The first symptoms were detected in propagation material. One week after planting, symptoms of root and crown rot were observed and approximately 10% of the plants died. Later, losses of 50% in some greenhouses were observed. A yield reduction as much as 65% was estimated in the winter period (January and February). The two main cucumber cultivars planted were Armada and Lopez. In February 2005, Phytophthora capsici (Leonian) (1) was isolated on potato dextrose agar from a sample of cv. Lopez. The isolate produced deciduous, papillate sporangia (occasionally with two or three papilla) and pedicels that were sometimes longer than the sporangia. Sequencing of amplicons of the internal transcribed spacer region (ITS) rDNA and of the mitochondrial cytochrome c oxidase subunit 1 (Cox1) gene (2) confirmed the identification. Three isolates collected through 2005 from the same greenhouse were crossed with tester strains of P. cryptogea. Formation of oogonia and amphigynous antheridia was always observed in crosses with mating type A2; thus, all isolates were the A1 mating type. All three isolates grew well at 35°C and did not produce chlamydospores. A pathogenicity test was performed with one isolate of P. capsici. Four plants of cucumber cvs. Indira and Jessica were grown in a growth chamber at 24°C. Plants at the two-leaf stage were drenched with 20 ml of a zoospore suspension of 106 zoospores per ml per plant. After 18 days, all plants of both cultivars developed symptoms of crown rot or wilted and died. P. capsici was reisolated from inoculated plants of both cultivars. The pathogenicity test was repeated in the same way, but in a greenhouse with temperatures that ranged between 18 and 29°C. In addition, four plants of both cultivars at the four-leaf stage were inoculated with a suspension of 105 zoospores per ml. After 1 week, all plants developed crown rot or were irreversibly wilted, independently of the plant age or the zoospore concentration. To our knowledge, this is the first report of P. capsici in Norway. References: (1) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society St. Paul MN, 1996. (2) L. P. N. M. Kroon et al. Phytopathology 94:613, 2004.

scholarly journals Diversity of Phytophthora capsici in Northwest Spain: Analysis of Virulence, Metalaxyl Response, and Molecular Characterization

Plant Disease ◽  
2006 ◽  
Vol 90 (9) ◽  
pp. 1135-1142 ◽  
Author(s):  
C. Silvar ◽  
F. Merino ◽  
J. Díaz
Keyword(s):  
Mating Type ◽  
Rapd Analysis ◽  
Random Amplified Polymorphic Dna ◽  
Phytophthora Capsici ◽  
Crown Rot ◽  
Group Method ◽  
Pair Group ◽  
Highly Sensitive ◽  
Virulence Assay ◽  
Pepper Cultivar

Phytophthora crown rot, caused by Phytophthora capsici, is potentially the most destructive disease of pepper in Spain. Phenotypic and genetic diversity of 16 P. capsici isolates collected from 11 farms in northwest Spain was characterized based on virulence, mating type, sensitivity to metalaxyl, and genetic analysis using random amplified polymorphic DNA (RAPD) methods. Low variability was observed among the isolates in their metalaxyl response, with 87.5% being highly sensitive. No isolates of the A2 mating type were detected. More variability was found in the virulence assay, and isolates were classified into two groups according to their pathogenicity on a set of four pepper cultivar differentials. Genetic variation examined with eight RAPD primers generated 92 polymorphic bands and revealed the existence of different patterns among isolates. Cluster analysis using the unweighted pair-group method with arithmetic averages (UPGMA) separated the Spanish isolates into three RAPD groups and established a relationship between the Spanish population and a representative worldwide group of isolates. No correlation was found between groups obtained by RAPD analysis and groups defined by virulence or metalaxyl response.

scholarly journals Insensitivity to Metalaxyl Among Isolates of Phytophthora capsici Causing Root and Crown Rot of Pepper in Southern Italy

Plant Disease ◽  
1998 ◽  
Vol 82 (11) ◽  
pp. 1283-1283 ◽  
Author(s):  
A. M. Pennisi ◽  
G. E. Agosteo ◽  
S. O. Cacciola ◽  
A. Pane ◽  
R. Faedda
Keyword(s):  
Mating Type ◽  
Southern Italy ◽  
Phytophthora Capsici ◽  
Crown Rot ◽  
Metalaxyl Resistance ◽  
Local Selection ◽  
Capsicum Spp ◽  
Root And Crown Rot ◽  
Single Hypha

Pepper (Capsicum annuum L.) has become an economically important crop in the coastal provinces of Catanzaro and Vibo Valentia, in Calabria (southern Italy). An old local selection Riggitano, very susceptible to root and crown rot caused by Phytophthora capsici Leonian, is the prevalent cultivar in this area. Although repeated applications of metalaxyl are used as a soil drench, severe outbreaks occur each year on greenhouse crops. To examine metalaxyl resistance in P. capsici, 60 single-hypha isolates of P. capsici were tested in vitro for their level of sensitivity to metalaxyl. The isolates were collected from 1992 to 1997, during epidemic outbreaks of root and crown rot, from two commercial greenhouse pepper crops, near Vibo Valentia and Lametia Terme (Catanzaro). Fungicide sensitivity was determined by plating mycelial plugs onto potato dextrose agar (PDA) amended with metalaxyl. The fungicide was added to PDA after autoclaving, at final concentrations of 0.1, 1, 5, 10, 50, 100, and 200 μg/ml a.i. The percentage of inhibition of radial growth on metalaxyl-amended medium compared with the growth on unamended medium was determined after 6 days of incubation in the dark at 25°C. Three replicate petri dishes were used per treatment and each test was performed twice. The isolates were paired in culture on V8 agar with isolates of P. capsici of known mating type and all proved to be A2 mating type. Significant variation was observed among the isolates tested in responce to metalaxyl. The ED50 values for in vitro inhibition of mycelial growth by metalaxyl ranged from 1 to 11 μg/ml, whereas an ED 50 value of 0.1 μg/ml had been reported for a wild-type isolate of P. capsici obtained from pepper in northern Italy (3). The variation observed among the isolates from Calabria appeared unrelated to both the geographical origin and the year of isolation. The isolates from Calabria were inhibited by between 1 and 12% at 0.1 μg/ml and by between 7 and 27% at 1 μg/ml, proving to be less sensitive to metalaxyl than isolates from Capsicum spp. originating from Central America, tested by other authors (1). According to the criterion used in a recent screening for sensitivity to metalaxyl (2), 19% of the isolates from Calabria should be considered sensitive, as they were inhibited by more than 60% at 5 μg/ml, while all the others were intermediate, as they were inhibited less than 60% at 5 μg/ml but more than 60% at 100 μg/ml. On the basis of this preliminary screening, we report the presence of insensitivity to metalaxyl in field isolates of P. capsici in southern Italy. Although no isolate tested appeared highly resistant to metalaxyl, the presence of a high proportion of isolates with an intermediate level of resistance should be a reason for the growers to use metalaxyl more cautiously to control root and collar rot. References: (1) M. D. Coffey and L. A. Bower. Phytopathology 74:502, 1984. (2) G. Parra and J. Ristaino. Plant Dis. 82:711, 1998. (3) M. L. Romano and A. Garibaldi. La difesa delle piante 3:153, 1984.

scholarly journals Phytophthora cryptoea on Common Sage (Salvia officinalis L.) in Italy

Plant Disease ◽  
2015 ◽  
Vol 99 (1) ◽  
pp. 161-161 ◽  
Author(s):  
A. Garibaldi ◽  
D. Bertetti ◽  
P. Pensa ◽  
G. Ortu ◽  
M. L. Gullino
Keyword(s):  
Mating Type ◽  
Its Region ◽  
The United States ◽  
Soil Extract ◽  
Selective Medium ◽  
Salvia Officinalis ◽  
Crown Rot ◽  
Fluorescent Light ◽  
Root And Crown Rot ◽  
Salvia Officinalis L

During the spring of 2013, many plants of common sage (Salvia officinalis L.), grown as potted plants in a commercial farm at Albenga (northern Italy) showed extensive symptoms of foliar wilt and root rot. The first symptoms developed with temperatures ranging between 8 and 26.5°C, average 17°C, and consisted of leaf chlorosis, wilting, and collapse. Severe root and crown rot were also observed, leading to sudden collapse of approximately 60% of the 6,000 plants within 60 days from transplant. Symptomatic tissues from the root and collar of infected plants were surface disinfested for 1 min in a 1% NaOCl solution, rinsed for 5 min in water, and placed on a selective medium for oomycetes (3). A Phytophthora-like organism (1) was consistently isolated and was transferred to carrot agar. Mycelial disks of the isolate DB13GIU02 were floated in petri plates containing soil extract (1), under continuous fluorescent light at room temperature. Hyphal swelling was abundant in such aqueous medium, measuring 6.4 to 20.1 (13.1 average) μm. Sporangia were obpyriform, persistent, and nonpapillate, measuring 25.3 to 55.1 × 17.9 to 37.1 (average 42.8 to 27.9) μm. Oospores and chlamydospores were absent. The same isolate was tested with two isolates of P. cryptogea from Quercus ilex (PH050, mating type A1) and from Pistacia lentiscus (PH017, mating type A2) on carrot agar, at 23 ± 1°C in the dark. Only the paring of DB13GIU02 with PH017 was successful and produced oogonia with diameter of 28.3 to 34.6 (average 31.7) μm, oospores with diameter of 28.0 to 32.2 (average 29.2) μm, and anphigynous antheridia of 10.5 to 15.1 × 11.6 to 15.1 (average 13.5 × 13.3) μm. DNA of the three isolates was extracted by using the Nucleospin Plant kit (Macherey Nagel). PCR of DNA amplified with primers Cryp 1 and Cryp 2 (4) from all P. cryptogea isolates produced a specific amplicon. The internal transcribed spacer (ITS) region of rDNA of the isolate DB13GIU02 was amplified using the primers ITS1/ITS4 and sequenced. BLAST analysis of the 845-bp segment (GenBank Accession No. KM458193) showed a 99% homology with the sequence of P. cryptogea GU111631. Pathogenicity tests were performed on healthy common sage 60-day-old plants by using one strain of P. cryptogea grown on a mixture of 2:1 wheat/hemp kernels. Infested kernels (10 g/liter of substrate) were mixed into a steam-disinfested substrate based on sphagnum peat/pomix/pine bark/clay (50:20:20:10 v/v). Control plants were treated with uninoculated wheat/hemp kernels mixed into the steam-disinfested soil. The trial was repeated once. Fifteen plants per treatment were used. All plants were kept in a growth chamber at 20 ± 1°C. Inoculated plants became chlorotic 7 days after inoculation, and root and crown rot developed 15 days after inoculation. P. cryptogea was consistently reisolated from inoculated plants. No colonies were isolated on the selective medium from control plants that remained symptomless. P. cryptogea has been reported on S. officinalis in the United States (2), while in Italy the same pathogen has been observed on S. leucantha. This is the first report of P. cryptogea on S. officinalis in Italy. The economic importance of the disease can increase due to the expanding use of this plant both as an aromatic for culinary purposes and for landscaping. References: (1) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. APS Press, St. Paul, MN, 1996. (2) S. T. Koike et al. Plant Dis. 81:959, 1997. (3) H. Masago et al. Phytopathology 67:25, 1977. (4) D. Minerdi et al. Eur. J. Plant Pathol. 122:227, 2008.

scholarly journals First Report of Phytophthora capsici on Cucumber and Melon in Southeastern Spain

Plant Disease ◽  
2002 ◽  
Vol 86 (5) ◽  
pp. 558-558 ◽  
Author(s):  
M. L. Herrero ◽  
R. Blanco ◽  
M. Santos ◽  
J. C. Tello
Keyword(s):  
Mating Type ◽  
Phytophthora Capsici ◽  
Crown Rot ◽  
Cucumis Sativus L ◽  
Leaf Stage ◽  
Southeastern Spain ◽  
Root And Crown Rot ◽  
Crown And Root Rot ◽  
Cucumis Melo L ◽  
First Time

In autumn 1999, crown and root rot along with wilting of cucumber (Cucumis sativus L.) were observed in greenhouses in southeastern Spain (Granada). Symptoms appeared again during the 2000 to 2001 growing season. In spring 2001, root and crown symptoms were observed also on melon (Cucumis melo L.) in greenhouses in another area of southeastern Spain (Almeria). Isolates from diseased plants from both locations were identified as Phytophthora capsici (Leonian). Isolates produced papillate sporangia of variable shape, some of them with two or three papilla. Sporangia were caducous with pedicels of variable lengths that could be longer than the sporangia. Three isolates were crossed with P. capsici strains of known mating type. All isolates produced amphigynous antheridia and were mating type A1. Isolates grew well at 35°C and did not produce chlamydospores. Pathogenicity was examined for one isolate from cucumber and one from melon. Cucumber and melon plants at the four-leaf stage and pumpkin (Cucurbita maxima × C. moschata) plants at the five-leaf stage were inoculated with a mycelium suspension. Both isolates caused wilting and death of plants on the three host species tested. The pathogen was reisolated from roots and stems of diseased plants. To our knowledge, this is the first time P. capsici has been found on cucumber in Spain. It is also the first time P. capsici has been found on melon in the greenhouses of southeastern Spain, and the first time it has been reported to cause root and crown rot of melon. Previously, P. capsici has been reported to cause disease of field-grown melon (2) and greenhouse-grown pepper (Capsicum annum) (1) in eastern and southeastern Spain, respectively. References: (1) J. C Tello. Comun. INIA 22, 1984. (2) J. J. Tuset Barrachina. An. INIA 7:11, 1977.

scholarly journals A PCR-based Assay for Distinguishing between A1 and A2 Mating Types of Phytophthora capsici

2017 ◽  
Vol 142 (4) ◽  
pp. 260-264
Author(s):  
Ping Li ◽  
Dong Liu ◽  
Min Guo ◽  
Yuemin Pan ◽  
Fangxin Chen ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Mating Type ◽  
Phytophthora Capsici ◽  
Mating Types ◽  
Sequence Repeat ◽  
Chain Reaction ◽  
Plant Parasite ◽  
Dna Fragment ◽  
Polymerase Chain ◽  
Microsatellite Diversity

Sexual reproduction in the plant parasite Phytophthora capsici Leonian requires the interaction of two distinct mating types, A1 and A2. Co-occurrence of these mating types can enhance the genetic diversity of P. capsici and alter its virulence or resistance characteristics. Using an intersimple sequence repeat (ISSR) screen of microsatellite diversity, we identified, cloned, and sequenced a novel 1121-base pair (bp) fragment specific to the A1 mating type of P. capsici. Primers Pcap-1 and Pcap-2 were designed from this DNA fragment to specifically detect the A1 mating type. Polymerase chain reaction (PCR) using these primers amplified an expected 997-bp fragment from known A1 mating types, but yielded a 508-bp fragment from known A2 mating types. This PCR-based assay could be adapted to accurately and rapidly detect the co-occurrence of A1 and A2 P. capsici mating types from field material.

scholarly journals First Report of Rhizoctonia solani AG 4 on Lamb's Lettuce in Italy

Plant Disease ◽  
2006 ◽  
Vol 90 (8) ◽  
pp. 1109-1109 ◽  
Author(s):  
A. Garibaldi ◽  
G. Gilardi ◽  
M. L. Gullino
Keyword(s):  
Rhizoctonia Solani ◽  
Morphological Characteristics ◽  
Northern Italy ◽  
Crown Rot ◽  
Pathogenicity Test ◽  
First Report ◽  
Pathogenicity Tests ◽  
Hyphal Diameter ◽  
Wheat Kernels ◽  
Extensive Necrosis

Lamb's lettuce or corn salad (Valerianella olitoria) is increasingly grown in Italy and used primarily in the preparation of mixed processed salad. In the fall of 2005, plants of lamb's lettuce, cv Trophy, exhibiting a basal rot were observed in some commercial greenhouses near Bergamo in northern Italy. The crown of diseased plants showed extensive necrosis, progressing to the basal leaves, with plants eventually dying. The first symptoms, consisting of water-soaked zonate lesions on basal leaves, were observed on 30-day-old plants during the month of October when temperatures ranged between 15 and 22°C. Disease was uniformly distributed in the greenhouses, progressed rapidly in circles, and 50% of the plants were affected. Diseased tissue was disinfested for 1 min in 1% NaOCl and plated on potato dextrose agar amended with 100 μg/liter of streptomycin sulfate. A fungus with the morphological characteristics of Rhizoctonia solani was consistently and readily isolated and maintained in pure culture after single-hyphal tipping (3). The five isolates of R. solani, obtained from affected plants successfully anastomosed with tester isolate AG 4, no. RT 31, received from R. Nicoletti of the Istituto Sperimentale per il Tabacco, Scafati, Italy (2). The hyphal diameter at the point of anastomosis was reduced, and cell death of adjacent cells occurred (1). Pairings were also made with AG 1, 2, 3, 5, 7, and 11 with no anastomoses observed between the five isolates and testers. For pathogenicity tests, the inoculum of R. solani (no. Rh. Vale 1) was grown on autoclaved wheat kernels at 25°C for 10 days. Plants of cv. Trophy were grown in 10-liter containers (20 × 50 cm, 15 plants per container) on a steam disinfested substrate (equal volume of peat and sand). Inoculations were made on 20-day-old plants by placing 2 g of infected wheat kernels at each corner of the container with 3 cm as the distance to the nearest plant. Plants inoculated with clean wheat kernels served as controls. Three replicates (containers) were used. Plants were maintained at 25°C in a growth chamber programmed for 12 h of irradiation at a relative humidity of 80%. The first symptoms, consisting of water-soaked lesions on the basal leaves, developed 5 days after inoculation with crown rot and plant kill in 2 weeks. Control plants remained healthy. R. solani was consistently reisolated from infected plants. The pathogenicity test was carried out twice with similar results. This is, to our knowledge, the first report of R. solani on lamb's lettuce in Italy as well as worldwide. The isolates were deposited at the AGROINNOVA fungal collection. The disease continues to spread in other greenhouses in northern Italy. References: (1) D. Carling. Rhizoctonia Species: Pages 37–47 in: Taxonomy, Molecular Biology, Ecology, Pathology and Disease Control. B. Sneh et al., eds. Kluwer Academic Publishers, the Netherlands, 1996. (2) J. Parmeter et al. Phytopathology, 59:1270, 1969. (3) B. Sneh et al. Identification of Rhizoctonia Species. The American Phytopathological Society, St. Paul, MN, 1996.

scholarly journals Distribution and Alteration of Mating Type of Phytophthora capsici Population from Red Pepper in Korea

2002 ◽  
Vol 30 (2) ◽  
pp. 152-156 ◽  
Author(s):  
Jeong-Young Song ◽  
Sung-Joon Yoo ◽  
Hong-Gi Kim
Keyword(s):  
Mating Type ◽  
Phytophthora Capsici ◽  
Red Pepper

scholarly journals First Report of Tar Spot on Orange Geiger, Cordia sebestena, Caused by Diatractium cordianum in Florida

Plant Disease ◽  
2008 ◽  
Vol 92 (8) ◽  
pp. 1250-1250 ◽  
Author(s):  
A. J. Palmateer ◽  
J. M. Pérez ◽  
R. A. Cating ◽  
R. C. Ploetz ◽  
M. A. Hoy
Keyword(s):  
Host Record ◽  
The United States ◽  
South Florida ◽  
Fluorescent Light ◽  
New Host ◽  
5.8S Rdna ◽  
Caribbean Islands ◽  
New Host Record ◽  
Tar Spot ◽  
Water Saturated

In July 2007, tar spot symptoms were observed on the leaves of orange Geiger, Cordia sebestena L. (Boraginaceae), in the landscape and a commercial nursery in Homestead, FL. The disease appears to be spreading and is locally severe. Symptoms were circular, slightly hypertrophied spots approximately 5 to 8 cm in diameter, which were slightly chlorotic on the abaxial surface and had numerous circular blackened stroma, 0.2 to 0.4 mm in diameter, on the adaxial surface. As leaves aged and yellowed, the areas around the spots remained pale green. Embedded in the stroma were numerous perithecia, 173 to 312 μm in diameter, circular to irregular in shape, with lateral necks as much as 200 μm long and 73 to 104 μm in diameter. Asci, 77 to 92 × 11 to 13 μm, contained elongate, two-celled ascospores, 50 to 61 × 3 to 5 μm that had a conspicuous constriction at the dividing cell wall. These dimensions and the pathogen's appearance matched closely with those published for Diatractium cordianum (Ellis & Kelsey) Syd (1). Young, symptomless leaves of C. sebestena were sprayed to runoff with a suspension of ascospores approximately 104 ml–1 that were harvested from affected leaves. Inoculated leaves were placed on water-saturated paper towels in petri plates and maintained in a growth chamber at 25°C with fluorescent light at 10 h day–1. Symptoms similar to those observed on affected trees in the landscape began to develop after 21 days and perithecia were evident after 28 days. An ITS 1, ITS 2, and 5.8s rDNA sequence was deposited in GenBank (Accession No. EU541488). A herbarium specimen was deposited at the U.S. National Fungus Collections (BPI No. 878441). This is a new host record for D. cordianum and is the first time the pathogen has been reported in the United States. Previous records were from Venezuela and several Caribbean islands, including Cuba and Jamaica. Symptoms of this disease have not been observed on Texas wild olive, Cordia boissieri, in close proximity to affected C. sebestena. P. F. Cannon (1) indicated that the disease had no economic impact. However, the conspicuous nature of symptoms on C. sebestena and the importance of this tree in the South Florida ornamental trade (2) suggest that this disease may become significant on the latter host. References: (1) P. F. Cannon. Mycol. Res. 92:327, 1989. (2) E. F. Gilman and D. G. Watson. Fact Sheet ST-182. Univ. Fla, Fla Coop Ext. Serv., 1993.

scholarly journals First Report of Phytophthora capsici Infecting Lima Bean (Phaseolus lunatus) in the Mid-Atlantic Region

Plant Disease ◽  
2002 ◽  
Vol 86 (9) ◽  
pp. 1049-1049 ◽  
Author(s):  
C. R. Davidson ◽  
R. B. Carroll ◽  
T. A. Evans ◽  
R. P. Mulrooney ◽  
S. H. Kim
Keyword(s):  
Phytophthora Capsici ◽  
Petri Dish ◽  
Lima Bean ◽  
Phaseolus Lunatus ◽  
Pathogenicity Test ◽  
Atlantic Region ◽  
Kent County ◽  
Original Field ◽  
Lima Beans ◽  
Stem Lesions

Lima beans are an important crop in Delaware and the Mid-Atlantic Region. In the summer of 2000, five commercial cultivars (3–28, 184–85, C-elite Sel, Butter Bean, and Jackson Wonder) of lima bean in Delaware, Maryland, and New Jersey were observed with white, appressed mycelia on infected pods that appeared distinctly different from signs of downy mildew infection caused by Phytophthora phaseoli. Isolations were made by placing diseased pods between layers of rye media (1). A fungus that produced white mycelia with sporangia was consistently isolated. All Phytophthora isolates from the infected pods were heterothallic, grew at 35°C, had as much as 100 μm long pedicles on varying shapes of caducous sporangia with tapering base and >2 papillae, and were identified as P. capsici (2). Initially, three surface-disinfected pods from cv. Early Thorogreen plants grown in the greenhouse were floated on 20 ml of sterile water in a petri dish, and each was inoculated with a disk of P. capsici. This was repeated for nine isolates obtained from lima bean. After incubation for 7 days at room temperature, all 27 pods were infected, and P. capsici was reisolated from all the pods. A pathogenicity test was performed on the same cultivars from which the original field isolates were collected. Three seedlings and two plants with mature pods were inoculated with a sporangial suspension of each of the nine isolates and placed in a dew chamber for 5 days at 20 to 25°C and 100% relative humidity. White mycelial growth was observed on seedlings and mature pods. One inoculated plant developed brown-to-black stem lesions with white mycelia. All pods on the mature plants showed appressed, white mycelia identical to that observed in the commercial lima bean fields. P. capsici was consistently reisolated from all inoculated plants. In 2000, most infected pods in infested fields were observed low in the plant canopy or touching the soil. However, in 2001, infected pods were mostly in the lower and mid-portion of the plants observed in baby lima bean fields in Kent County, DE. References: (1) C. E. Caten and J. L. Jinks. Can. J. Bot. 46:329, 1967. (2) D. C. Erwin and O. K. Ribeiro. Phytophthora capsici. Page 264 in: Phytophthora Diseases Worldwide. The American Phytopathological Society, St Paul, MN, 1996.

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