scholarly journals Host Specificity and Variations in Aggressiveness of North Carolina Isolates of Phytophthora cryptogea and P. drechsleri in Greenhouse Ornamental Plants

Plant Disease ◽  
2013 ◽  
Vol 97 (1) ◽  
pp. 74-80 ◽  
Author(s):  
H. A. Olson ◽  
D. M. Benson
Keyword(s):  
North Carolina ◽  
Host Specificity ◽  
Plant Species ◽  
Root Rot ◽  
Ornamental Plants ◽  
Phytophthora Root Rot ◽  
Phytophthora Cryptogea ◽  
Foliar Symptoms ◽  
Single Host ◽  
African Marigold

Three isolates of Phytophthora cryptogea and three isolates of P. drechsleri were evaluated for host specificity and variations in aggressiveness on eight floriculture crops commonly grown in North Carolina. Plants were monitored for the development of foliar symptoms stemming from root rot caused by Phytophthora. No isolates of P. cryptogea or P. drechsleri had the same host range, though all P. cryptogea isolates caused foliar symptoms on gerbera daisy and annual stock, and all P. drechsleri isolates incited disease on osteospermum. No African marigold plants developed foliar symptoms of Phytophthora root rot. All P. cryptogea isolates caused foliar symptoms on at least three tested plant species. Isolates of P. drechsleri varied from highly specific and only causing disease on a single host species to relatively nonspecific and causing foliar symptoms on the majority of host plants. This is the first report of host specificity of ornamental isolates of P. drechsleri, and several of the tested plants are not reported hosts of P. drechsleri. Differences in isolate aggressiveness were found and depended on plant species; overall, isolates of P. drechsleri were more aggressive than P. cryptogea isolates. Isolations from nonsymptomatic inoculated plants suggest that these Phytophthora spp. could be moved between growers or from growers to consumers on nonsymptomatic infected ornamentals.

scholarly journals Incidence of Phytophthora Root Rot of Fraser Fir in North Carolina and Sensitivity of Isolates of Phytophthora cinnamomi to Metalaxyl

Plant Disease ◽  
2000 ◽  
Vol 84 (6) ◽  
pp. 661-664 ◽  
Author(s):  
D. M. Benson ◽  
L. F. Grand
Keyword(s):  
North Carolina ◽  
Root Rot ◽  
Phytophthora Cinnamomi ◽  
Disease Incidence ◽  
The State ◽  
Systematic Sampling ◽  
Phytophthora Root Rot ◽  
Fraser Fir ◽  
Phytophthora Spp ◽  
Old Trees

A survey of Fraser fir Christmas trees in North Carolina for incidence of Phytophthora root rot was conducted during 1997 and 1998. Field sites (7- to 13-year-old trees) and nursery transplant beds (4- to 5-year-old trees) selected at random were surveyed based on foliar symptoms of Phytophthora root rot. Field sites were surveyed with a random transect method (>3,000 trees/field) or by counting all trees (<3,000 trees/field). Overall, incidence of Phytophthora root rot averaged 9% over the 58 field sites sampled, with a range of 0 to 75%. No relationship was found between number of years Fraser fir had been planted in the field site and disease incidence. Disease incidence did not increase as field sites were rotated through second or third crops of Fraser fir. Phytophthora spp. were recovered from 1.8% of asymptomatic trees sampled from 58 field sites across the state. P. cinnamomi accounted for 91% of the Phytophthora isolates recovered. In nursery transplant beds where a systematic sampling procedure was used, incidence of diseased trees averaged 2%, with a range of 0 to 12% across 16 locations. Recovery of Phytophthora spp. averaged 1.2% from root samples collected from 50 asymptomatic seedlings at each location. Isolates collected from the field and nursery transplant beds were grown on cornmeal agar incorporated with 0, 1, 1.25, 10, or 100 μg a.i. metalaxyl/ml. All 166 isolates of P. cinnamomi tested were sensitive to metalaxyl at 1 or 1.25 μg a.i. metalaxyl/ml. Although incidence of Phytophthora root rot has not increased in the state compared to a survey done in 1976 to 1977, the disease continues to limit production of Fraser fir in North Carolina.

scholarly journals First Report of Phytophthora Root Rot of Sugar Beet, Caused by Phytophthora cryptogea, in Greece

Plant Disease ◽  
2000 ◽  
Vol 84 (5) ◽  
pp. 593-593 ◽  
Author(s):  
G. S. Karaoglanidis ◽  
D. A. Karadimos ◽  
K. Klonari
Keyword(s):  
Sugar Beet ◽  
Root Rot ◽  
Soil Extract ◽  
American Phytopathological Society ◽  
Phytophthora Root Rot ◽  
Phytophthora Cryptogea ◽  
First Report ◽  
Solid Media ◽  
Necrotic Spots ◽  
Extract Medium

A severe rot of sugar beet roots was observed in the Amyndeon area of Greece during summer 1998. Infected plants initially showed a temporary wilt, which became permanent, and finally died. Slightly diseased roots showed necrotic spots toward the base, whereas more heavily diseased roots showed a more extensive wet rot that extended upward. Feeder roots also were infected and reduced in number because of decay. Rotted tissue was brown with a distinguishing black margin. In most of the isolations, carried out on potato dextrose agar (PDA), the pathogen obtained was identified as Phytophthora cryptogea Pethybr. & Lafferty Mycelium consisted of fairly uniform, fine hyphae that showed a slightly floral growth pattern. In autoclaved soil-extract medium, chains or clusters of hyphal swellings (average 12 µm diameter) formed. Sporangia were not produced on solid media but were abundant in soil-extract medium. Sporangia were oval to obpyriform in shape, nonpapillate with rounded bases, and varied in size (39 to 80 × 24 to 40 µm). Oospores were plerotic, thick-walled, and averaged 25 µm in diameter. The isolated pathogen, cultured on PDA, could not grow at all at 36°C. The closely related species P. drechsleri Tucker has been reported to cause similar root rot symptoms on sugar beet (3). However, P. drechsleri grows well at 36°C, while P. cryptogea cannot grow at this temperature; this is the major distinguishing feature that separates the two species (1). To test the pathogenicity of the organism, surface-sterilized sugar beet roots (cv. Rizor) were inoculated with 5-mm-diameter PDA plugs containing actively growing mycelium. Sterile PDA plugs were used to inoculate control sugar beet roots. Inoculated roots were kept at 27°C in the dark for 10 days. Extensive decay of inoculated roots developed, similar to decay observed in the field, whereas control roots showed no decay. P. cryptogea was reisolated from rotted tissues. This pathogen has been recognized previously as a cause of root rot of sugar beet in Japan (1) and Wyoming (2). This is the first report of Phytophthora root rot of sugar beet in Greece. References: (1) D. C. Erwin and O. K. Ribeiro. 1996. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN. (2) P. C. Vincelli et. al. Plant Dis. 74:614, 1990. (3) E. D. Whitnew and J. E. Duffus, eds. 1986. Compendium of Beet Diseases and Insects. The American Phytopathological Society, St. Paul, MN.

scholarly journals Mefenoxam Sensitivity, Aggressiveness, and Identification of Pythium Species Causing Root Rot on Floriculture Crops in North Carolina

Plant Disease ◽  
2015 ◽  
Vol 99 (11) ◽  
pp. 1550-1558 ◽  
Author(s):  
E. C. Lookabaugh ◽  
K. L. Ivors ◽  
B. B. Shew
Keyword(s):  
North Carolina ◽  
Host Species ◽  
Root Rot ◽  
Internal Transcribed Spacer ◽  
Ornamental Plants ◽  
Pythium Species ◽  
Selective Media ◽  
Microtiter Plates ◽  
Pythium Root Rot

Herbaceous ornamental plants exhibiting symptoms of Pythium root rot were collected from 26 greenhouses in 21 counties in North Carolina (NC) from 2010 to 2012. Plant symptoms ranged from mild stunting to severe wilting, root rot, and death. Roots were plated on selective media, and 356 isolates of Pythium were recovered from 34 host species. Selected isolates were identified by sequencing of the internal transcribed spacer (ITS) rDNA gene region. Seventeen Pythium species were identified, with P. aphanidermatum, P. irregulare, and P. myriotylum comprising 75% of the 320 isolates sequenced. Twelve of the 26 greenhouses had more than one species present. Mefenoxam sensitivity was tested in vitro by growing isolates in wells of microtiter plates containing clarified V8 agar amended with 100 µg a.i./ml mefenoxam. Colonization was scored after 24 to 48 h using a scale of 0 (no growth) to 5 (entire well colonized). Fifty-two percent of the isolates were resistant to mefenoxam (mean score ≥4). All 32 isolates of P. myriotylum were sensitive, whereas sensitivity varied among isolates of P. aphanidermatum and P. irregulare. Resistant and sensitive isolates of the same species were found within the same greenhouses. The aggressiveness of P. aphanidermatum and P. irregulare isolates was evaluated on poinsettia, Gerbera daisy, and petunia. P. aphanidermatum was more aggressive than P. irregulare on poinsettia and petunia; symptoms were mild and no differences in aggressiveness were observed on Gerbera daisy. Sensitivity to mefenoxam was not related to aggressiveness.

scholarly journals First Report of Phoma terrestris Causing Red Root Rot on Sweet Corn (Zea mays) in North Carolina

Plant Disease ◽  
2007 ◽  
Vol 91 (8) ◽  
pp. 1054-1054 ◽  
Author(s):  
S. R. Koenning ◽  
J. W. Frye ◽  
J. K. Pataky ◽  
M. Gibbs ◽  
D. Cotton
Keyword(s):  
North Carolina ◽  
Root Rot ◽  
Sweet Corn ◽  
Adventitious Shoot ◽  
Fresh Market ◽  
First Report ◽  
The North ◽  
Field Corn ◽  
Foliar Symptoms ◽  
Corn Plants

Red root rot, caused by Phoma terrestris E. M. Hansen, caused premature senescence and yield reductions to fresh-market sweet corn in Hyde County, North Carolina in July 2006. Foliar symptoms developed over a period of 5 to 8 days approximately 1 to 2 weeks after anthesis and included desiccation of leaves and poor development of ears. By 3 weeks after pollination, when the sweet corn was harvested, crowns and the first aboveground internode of affected plants were rotted and reddish colored, but roots appeared normal. The root mass of affected plants tended to be greater than that of unaffected plants. Incidence of symptomatic plants was greater than 30% in some fields and was lower on crops planted and harvested early. Symptomatic and asymptomatic plants were adjacent in affected fields. Diseased plants were more common in fields of sweet corn that followed soybean (Glycine max) or a double-crop of onions (Allium cepa) than in fields that followed corn. Incidence of symptomatic plants also differed among adjacent plantings of different sweet corn hybrids. Hybrids ‘173A’, ‘182A’, ‘378a’, and ‘XTH1178’ had a high incidence of symptomatic plants and ‘372A’, ‘278A’, ‘8101’, and ‘8102’ were less affected. Samples of symptomatic plants of the hybrid ‘182A’ were examined at the North Carolina Plant Disease and Insect Clinic during August. Olivaceous black pycnidia with long setae around the ostioles were imbedded in the stalk near the first node aboveground. Numerous conidia (1.8 to 2.3 × 4.5 to 5.5 μm) were released in cirri from pycnidia. When cultured on potato dextrose agar (PDA), the fungus produced a red pigment and intercalary and terminal chlamydospores. Pathogenicity was demonstrated in the greenhouse by transplanting corn seedlings or direct-seeding corn into pots of soil infested with plates of PDA containing chlamydospores and hyphae. A suspension of chlamydospores and hyphae also was injected into the stems of plants 28 days after transplanting. Five replicates of the pathogenicity experiments were repeated twice with noninoculated controls. After 8 weeks, P. terrestris was recovered from the roots of all inoculated plants. Soil inoculation resulted in necrotic root tissue in approximately 25% of inoculated plants. Approximately 90% of inoculated plants had discolored crowns that resembled symptoms from field infected plants. Stem inoculations resulted in necrosis extending 2 to 5 cm from the point of injection and resulted in shoot death of 40% of inoculated plants that resulted in the development of an adventitious shoot. Red root rot was prevalent on field corn in the Delmarva Peninsula throughout the late 1980s and 1990s (1). To our knowledge, this is the first report of this disease causing damage to sweet corn in North Carolina. Foliar symptoms and discoloration of crowns of diseased sweet corn plants were similar to previously described symptoms of red root rot on field corn (2), however, roots of affected sweet corn plants were not substantially rotted and did not have a symptomatic reddish pink or dark carmine color, presumably because sweet corn is harvested prior to the development of root symptoms. References: (1) K. W. Campbell et al. Plant Dis. 75:1186, 1991. (2) D. G. White, ed. Compendium of Corn Diseases. The American Phytopathological Society, St Paul, MN, 1999.

scholarly journals Distribution and Host Range of the Burrowing Nematode in Puerto Rican Soils

1969 ◽  
Vol 47 (1) ◽  
pp. 28-37
Author(s):  
Alejandro Ayala ◽  
Jessé Román
Keyword(s):  
Puerto Rico ◽  
Puerto Rican ◽  
Host Range ◽  
Plant Species ◽  
Root Rot ◽  
Ornamental Plants ◽  
The State ◽  
The Other ◽  
Burrowing Nematode

Because of quarantine recently established by the State of California on ornamental material imported from Puerto Rico, Hawaii, and Florida, a study was undertaken in 1955, which lasted until 1960, to determine the distribution of the burrowing nematode in Puerto Rico. Six of the most important ornamental nurseries and several localities in which economic important crops are grown were sampled. Eight different ornamental plants were found infected with burrowing nematodes in three of the nurseries. The nematode was found to be widely distributed and a serious problem in one of the nurseries, where it was presumably introduced with infected banana material. In the other two the nematode was present in limited numbers only and infected very few plants. The nematode was well distributed in banana and plantain, in which it caused a root rot condition that usually destroyed whole plantations. The distribution of the nematode and symptoms caused to these crops are discussed. Coffee and noncultivated cotton were also found to be attacked by the nematode. Five of the twelve plant species here reported as hosts of the burrowing nematode in Puerto Rico are probably newly reported hosts.

scholarly journals Identification, Mefenoxam Sensitivity, and Compatibility Type of Phytophthora spp. Attacking Floriculture Crops in North Carolina

Plant Disease ◽  
2005 ◽  
Vol 89 (2) ◽  
pp. 185-190 ◽  
Author(s):  
J. Hwang ◽  
D. M. Benson
Keyword(s):  
North Carolina ◽  
Species Identification ◽  
Plant Species ◽  
Mating Type ◽  
Single Source ◽  
Phytophthora Cryptogea ◽  
African Violet ◽  
Phytophthora Spp ◽  
Sensitivity Tests ◽  
Symptomatic Plant

Phytophthora isolates were collected from floriculture crops grown in commercial greenhouses in North Carolina for species identification, compatibility type determination, and mefenoxam sensitivity tests. Isolation from 41 symptomatic plant species at 29 production locations resulted in 483 isolates from eight crops at seven locations. Phytophthora cryptogea (184 isolates) was recovered from dusty miller and gerbera daisy. All isolates of P. cryptogea were insensitive or intermediate in sensitivity to mefenoxam at 1 μg a.i./ml and were A1 compatibility type. P. nicotianae (273 isolates) was isolated from African violet, lavender, pansy, petunia, and vinca. Of these isolates, 21% were insensitive to mefenoxam at either 1 or 100 μg a.i./ml. Isolates of P. nicotianae from five locations were A2 compatibility type, whereas isolates on pansy at one location were A1 compatibility type. English ivy grown at two locations was infected with P. palmivora. All 26 isolates of P. palmivora were sensitive to mefenoxam and were A1 compatibility type. Mating type and mefenoxam sensitivity were uniform among isolates of P. nicotianae and P. palmivora from a given crop at a given location, suggesting that epidemics within a location may have originated from a single source of inoculum.

scholarly journals Grafting Fraser Fir onto Rootstocks of Selected Abies Species

HortScience ◽  
2002 ◽  
Vol 37 (5) ◽  
pp. 815-818 ◽  
Author(s):  
Eric Hinesley ◽  
John Frampton
Keyword(s):  
North Carolina ◽  
Root Rot ◽  
Field Experiments ◽  
Interspecific Variation ◽  
Phytophthora Root Rot ◽  
Fraser Fir ◽  
Christmas Trees ◽  
Nordmann Fir ◽  
Canaan Valley ◽  
Turkish Fir

Orthotropic shoots (tips of primary axes) from 3-year-old Fraser fir seedlings [Abies fraseri (Pursh) Poir.] were grafted onto rootstocks of Fraser fir, Korean fir (A. koreana Wils.), momi fir (A. firma Sieb. & Zucc.), Nordmann fir (A. nordmanniana (Steven) Spach.), Turkish fir (A. bornmuelleriana Mattf.), and West Virginia balsam fir from Canaan Valley (Canaan fir) [A. balsamea (L.) Mill. var. phanerolepis Fern.]. Firstyear survival in the greenhouse was 92% to 98% except for momi fir (83%). The percentage of grafted plants with orthotropic shoots was 92% to 98%, except for Korean (81%) and momi fir (86%). Plants were subsequently established in replicated field experiments on three sites in the piedmont and mountains of North Carolina. In general, leader elongation of grafted Fraser fir scions was greater than leader growth on nongrafted transplants, including Fraser fir. Differences in survival appear to reflect interspecific variation in resistance to phytophthora root rot and/or tolerance of warm environments. Grafting may offer the potential to grow Abies Christmas trees on previously unsuitable sites, or to reclaim or continue using sites already seriously impacted by root rot.

scholarly journals First Report of Phytophthora Root Rot Caused by Phytophthora cryptogea on Spinach in California

Plant Disease ◽  
2010 ◽  
Vol 94 (1) ◽  
pp. 131-131 ◽  
Author(s):  
S. T. Koike ◽  
Frank N. Martin
Keyword(s):  
Root Rot ◽  
Spinacia Oleracea ◽  
Root Zone ◽  
Sequence Data ◽  
Soil Extract ◽  
Phytophthora Root Rot ◽  
Phytophthora Cryptogea ◽  
First Report ◽  
Root Rots ◽  
Zoospore Release

In 2006 and 2007, commercially grown spinach (Spinacia oleracea) in California's coastal Salinas Valley (Monterey County) was affected by an unreported root rot disease. Disease was limited to patches along the edges of fields. Affected plants were stunted with chlorotic older leaves. As disease progressed, most of the older foliage first wilted and then turned tan and dry; youngest leaves remained green but were stunted and leathery in texture. Plants most severely affected died. Symptoms on roots were mostly restricted to the distal portion of the root system, where feeder roots and the main taproot turned black. Isolations from root lesions consistently resulted in the recovery of a Phytophthora sp. The isolates were heterothallic, and on the basis of morphological and cytochrome oxidase 2 gene sequence data (GenBank Accession No. GQ984233), the pathogen was identified as Phytophthora cryptogea. To evaluate pathogenicity, individual inocula of four isolates were prepared by incubating colonized 6-mm-diameter V8 agar plugs in filtered soil extract for 2 days at 20°C to induce sporangia production. These cultures were then chilled at 4°C for 20 min and returned to room temperature for 1 h to induce zoospore release (4). Four-week-old spinach plants (cv. Bolero) were uprooted, soaked in suspensions of 1.0 × 105 zoospores/ml for 10 min, and repotted. After treatment, pots were placed in shallow trays of water for 24 h to saturate the root zone, then were removed from trays and incubated in a greenhouse. After 9 days, inoculated plants showed foliar wilting and chlorosis similar to that observed in the field; after 13 days, roots were examined and found to show the black necrosis as seen in the field. P. cryptogea was isolated from all inoculated plants. Control spinach plants, treated with soil extract only, did not develop disease. This experiment was completed two times and the results were similar. To our knowledge, this is the first report of Phytophthora root rot of spinach caused by P. cryptogea in California. This finding is significant because spinach in California is subject to root rots caused by three other pathogens (Fusarium oxysporum, Pythium spp., and Rhizoctonia solani) (1); symptoms from these root rots are very similar to those caused by P. cryptogea, thereby complicating diagnosis. This pathogen has been documented on spinach in Germany and Sweden (2,3). References: (1) S. T. Koike et al. Vegetable Diseases: A Color Handbook. Manson Publishing LtD. London, 2007. (2) H. Krober and E.-O. Beckmann. Phytopathol. Z. 78:160, 1973. (3) M. Larsson and J. Olofsson. Plant Pathol. 43:251, 1994. (4) S. A. Tjosvold et al. Plant Dis. 93:371, 2009.

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