scholarly journals Evaluation and Identification of Basil Germ Plasm for Resistance to Fusarium oxysporum f. sp. basilicum

Plant Disease ◽  
1997 ◽  
Vol 81 (9) ◽  
pp. 1077-1081 ◽  
Author(s):  
Reuven Reuveni ◽  
Nativ Dudai ◽  
Eli Putievsky ◽  
W. H. Elmer ◽  
R. L. Wick
Keyword(s):  
United States ◽  
Fusarium Oxysporum ◽  
Germ Plasm ◽  
The United States ◽  
Ocimum Basilicum ◽  
Artificial Inoculation ◽  
Growth Chamber ◽  
Thymus Vulgaris ◽  
Infested Soil ◽  
Causal Organism

Growth chamber evaluation of several cultivars of basil and related herbs examined in the United States revealed that identical cultivars from different sources did not differ in their reactions to artificial inoculation with Fusarium oxysporum f. sp. basilicum. Cultivars differed in susceptibility to the pathogen: “Spicy globe” miniature was the most susceptible, and lemon basil (Ocimum basilicum var. citriodorum), Origanum majorana, and Thymus vulgaris were rated as not susceptible. Twenty isolates of F. oxysporum, originating from stems of diseased basil plants in Israel, were pathogenic on basil in growth chamber and greenhouse tests. Under artificial inoculation, 2 isolates of F. oxysporum f. sp. basilicum from stems were pathogenic to basil but not to 9 species representing Lamiaceae, Cucurbitaceae, Solanaceae, and Compositae indicating the specificity of the pathogen to basil. These isolates were used for additional resistance tests. Ocimum basilicum var. purpurascens (Exotic) and var. citriodorum were rated as not susceptible to the pathogen under artificial inoculation. Resistant germ plasm was identified in several basil plants of a local variety originally introduced from the United States and reselected at Newe Ya'ar. Seeds were planted in the greenhouse in naturally highly infested soil. Symptomless plants that survived in naturally infested soil were the source for F1 seeds of resistant germ plasm, which was confirmed by artificial inoculations with both isolates of the pathogen. Further selection tests to improve resistance were conducted up to the F4 generation in infested soil in the greenhouse. All individuals of the present genetic line remained symptomless, while all individual plants of the original susceptible cultivar defoliated 3 weeks after planting into infested soil, suggesting that the resistance may be a single, dominant gene. The causal organism was reisolated only from the susceptible plants and not from the symptomless resistant plants through all the experiments.

scholarly journals Stewart's Wilt Reactions of an International Collection of Zea mays Germ Plasm Inoculated with Erwinia stewartii

Plant Disease ◽  
2000 ◽  
Vol 84 (8) ◽  
pp. 901-906 ◽  
Author(s):  
Jerald K. Pataky ◽  
Lindsey J. du Toit ◽  
Noah D. Freeman
Keyword(s):  
United States ◽  
Germ Plasm ◽  
Sweet Corn ◽  
The United States ◽  
River Valley ◽  
Ohio River ◽  
Ohio River Valley ◽  
The World ◽  
The Mean ◽  
Stewart's Wilt

Maize accessions were evaluated in 1997, 1998, and 1999 to identify additional sources of Stewart's wilt resistance and to determine if reactions differed among accessions collected from various regions of the United States and throughout the world. The distributions of Stewart's wilt reactions rated from 1 (no appreciable spread of symptoms) to 9 (dead plants) were relatively similar among groups of accessions from all regions of the world except for those from the Mid-Atlantic/Ohio River Valley region of the United States, the southern United States, and the northeastern United States. The mean and median Stewart's wilt rating for 1,991 accessions evaluated in 1997 was 4. The mean Stewart's wilt rating for 245 accessions collected from the Mid-Atlantic/Ohio River Valley region was 3.1, which was significantly lower than that for accessions from all other regions. The mean rating for accessions from the southern United States was 3.7, which also was lower than mean ratings for accessions from all other regions. Ratings from trials in 1997 and 1998 were highly correlated (r = 0.87) for 292 accessions and 15 sweet corn hybrid checks evaluated in both years. Of 20 accessions rated below 2 in 1997 and 1998, seven were from Virginia, seven were from the Ohio River Valley or central Corn Belt of the United States, four were from the northern or western Corn Belt of the United States, and two were from Spain. Ratings for these accessions ranged from 1.7 to 3.1 in 1999. Ratings ranged from 2.6 to 3.7 for F1 hybrids of these accessions crossed with one of two susceptible sweet corn inbreds, CrseW30 or Crse16, which were rated 5.7 and 5.4, respectively. Based on the reactions of this collection of germ plasm, it appears that high levels of Stewart's wilt resistance are prevalent only among accessions collected from areas where the disease has been endemic for several years, whereas moderate levels of resistance can be found in accessions collected from nearly everywhere in the world.

scholarly journals Black Choke Disease Caused by an Ephelis sp. on Purple Fountain Grass in Maryland

Plant Disease ◽  
2006 ◽  
Vol 90 (1) ◽  
pp. 112-112
Author(s):  
E. Lewis Roberts ◽  
J. F. White
Keyword(s):  
United States ◽  
North America ◽  
The United States ◽  
Maximum Parsimony Analysis ◽  
Bootstrap Support ◽  
Herbarium Specimens ◽  
Dense Layer ◽  
Causal Organism ◽  
Plant Nursery ◽  
Choke Disease

Purple fountain grass (Pennisetum alopecuroides) is indigenous to Asia, prized for its foxtail-like purple flowers, and widely used as an ornamental. During October 1999, black choke disease was found on P. alopecuroides cv. Hameln (L.) Spreng at a plant nursery in Maryland. Disease symptoms include mummification of inflorescences by black conidial stromata, distorted leaf tissue, and a dense layer of white epiphytic mycelium on the adaxial leaves and culms. Stromata were initially white but became black with age. Microscopic analysis of the isolated fungus indicated that the causal organism was an Ephelis sp., American Type Culture Collection No. MYA-3317. The ephelidial conidia developed in sporodochia on stromata and were hyaline, filiform to acicular, and 18 to 21 × 1 μm. Cultures on potato dextrose agar were off-white and 50 mm in diameter after 14 days at 23°C. Analysis of herbarium specimens of several Balansia spp. revealed that the Ephelis sp. isolate bears morphological resemblance to Asian and not American Balansieae. In fact, the infection observed on Pennisetum sp. forms similarly to Ephelis sp. infection on Oryza sativa L. (Asian) that also results in development of stromata on panicles and a mycelial network enclosing the panicles, preventing maturation and expansion. On both plants, the infected inflorescence becomes black with age and appears mummified as pseudosclerotia form. Furthermore, flag leaves and tillers of both plants appear slightly distorted and silver due to the epibiotic mycelia. The causal agent of black choke disease on rice is Ephelis oryzae Syd. (teleomorph = Balansia oryzae-sativae Hashioka). The mature stroma of E. oryzae forms on the inflorescence and is embedded with a layer of ovate perithecia. Immature stromata bear conidiomata that are cupulate to cushion shaped and black, producing hyaline, branched conidiophores that terminate in phialides. Conidia are ephelidial, filiform to acicular, hyaline, and 18 to 22 × 1.5 μm (2). To determine the phylogenetic relationship between other balansioid fungi and the Ephelis sp. isolate, the nuclear ribosomal internal transcribed spacer (ITS1) region was amplified with primers ITS4 and ITS5 (3). Maximum parsimony analysis of the ITS1 sequences showed that the Ephelis sp. infecting P. alopecuroides cv. Hameln grouped (100% bootstrap support) in a clade with Ephelis oryzae, Balansia sclerotica, Balansia andropogonis, and Balansia sp.; all endemic to Asia and tightly groups with the Asian rice pathogen Ephelis oryzae (100% bootstrap support). Further phylogenetic analysis using topological constraints indicated that Ephelis sp. is not appropriately grouped with American balansioid species. Since P. alopecuroides is often imported to North America from Asia (1), it is likely that Ephelis sp. on P. alopecuroides is endemic to Asia and perhaps was transported along with its host to North America. The disease ontogeny, morphology, and sequence similarities between the Ephelis sp. isolated from Pennisetum sp. and E. oryzae suggests that these fungi are evolutionarily close, sibling species, or conspecific. To our knowledge, this is the first report of choke disease on P. alopecuroides in the United States. References: (1) A. S. Hitchcock. Manual of the Grasses of the United States. A. Chase, ed. U.S. Government Print Office, Washington DC, 1951 (2) F. N. Lee and P. S. Gunnell. Udbatta. Page 29 in: Compendium of Rice Diseases. R. K. Webster and P. S. Gunnell, eds. The American Phytopathological Society, St. Paul. MN, 1992. (3) J. F. White Jr. et al. Mycologia 89:408, 1997.

DNA-based quantification of Fusarium oxysporum f. sp. vasinfectum in environmental soils to describe spatial variation in inoculum density

Plant Disease ◽  
2022 ◽  
Author(s):  
Roy Davis ◽  
Thomas Isakeit ◽  
Thomas Chappell
Keyword(s):  
United States ◽  
Fusarium Oxysporum ◽  
Spatial Scales ◽  
The United States ◽  
Inoculum Density ◽  
Root Knot Nematode ◽  
West Texas ◽  
Sudden Appearance ◽  
Digital Polymerase Chain Reaction ◽  
Race 4

Fusarium wilt of cotton, caused by the soilborne fungal pathogen Fusarium oxysporum f. sp. vasinfectum (FOV), occurs in regions of the United States where cotton (Gossypium spp.) is grown. Race 4 of this pathogen (FOV4) is especially aggressive and does not require the co-occurrence of the root knot nematode (Meloidogyne incognita) to infect cotton. Its sudden appearance in far-west Texas in 2016 after many years of being restricted to California is of great concern, as is the threat of its continued spread through the cotton-producing regions of the United States. The aim of this research was to analyze the spatial variability of FOV4 inoculum density in the location where FOV4 is locally emerging, using quantitative and droplet digital polymerase chain reaction (qPCR and ddPCR) methods. Soil samples collected from a field with known FOV4 incidence in Fabens, Texas were analyzed. Appreciable variation in inoculum density was found to occur at spatial scales smaller than the size of plots involved in cultivar trial research, and was spatially autocorrelated (Moran’s I, Z = 17.73, p < 0.0001). These findings indicate that for cultivar trials, accounting for the spatial distribution of inoculum either by directly quantifying it or through the use of densely-distributed “calibration checks” is important to the interpretation of results.

scholarly journals Suppression of Fusarium Wilt Caused by Fusarium oxysporum f. sp. niveum Race 2 on Grafted Triploid Watermelon

Plant Disease ◽  
2014 ◽  
Vol 98 (10) ◽  
pp. 1326-1332 ◽  
Author(s):  
Anthony P. Keinath ◽  
Richard L. Hassell
Keyword(s):  
Fusarium Oxysporum ◽  
Fusarium Wilt ◽  
Disease Incidence ◽  
The United States ◽  
Infested Soil ◽  
Marketable Yield ◽  
Race 1 ◽  
Susceptible Control ◽  
Triploid Watermelon ◽  
Race 2

Fusarium wilt of watermelon, caused by the soilborne fungal pathogen Fusarium oxysporum f. sp. niveum race 2, is a serious, widespread disease present in major watermelon-growing regions of the United States and other countries. ‘Fascination,’ a high yielding triploid resistant to race 1, is grown in southeastern states in fields that contain a mixture of races 1 and 2. There is some benefit to using cultivars with race 1 resistance in such fields, even though Fascination is susceptible to Fusarium wilt caused by race 2. Experiments in 2012 and 2013 were done in fields infested primarily with race 2 and a mixture of races 1 and 2, respectively. Fascination was grafted onto four rootstock cultivars: bottle gourd (Lagenaria siceraria) ‘Macis’ and ‘Emphasis’ and interspecific hybrid squash (Cucurbita maxima× C. moschata) ‘Strong Tosa’ and ‘Carnivor.’ Nongrafted and self-grafted Fascination were used as susceptible control treatments. In both experiments, mean incidence of plants with symptoms of Fusarium wilt was ≥52% in the susceptible control treatments and ≤6% on the grafted rootstocks. Disease incidence did not differ between rootstock species or cultivars. In both years, Fascination grafted onto Strong Tosa and Macis produced more marketable-sized fruit than the susceptible control treatments. Grafted Emphasis and Carnivor also produced more fruit than the control treatments in 2012. The cucurbit rootstocks suppressed Fusarium wilt caused by race 2 and increased marketable yield of triploid watermelon grown in infested soil.

Response of Sugarbeet Lines to Isolates of Fusarium oxysporum f. sp. Betae from the United States

2009 ◽  
Vol 46 (1) ◽  
pp. 11-26 ◽  
Author(s):  
L E Hanson ◽  
A L Hill ◽  
B J Jacobsen ◽  
L Panella
Keyword(s):  
United States ◽  
Fusarium Oxysporum ◽  
The United States

scholarly journals First Report of Stem Rot of Stevia Caused by Sclerotinia sclerotiorum in North Carolina

Plant Disease ◽  
2014 ◽  
Vol 98 (10) ◽  
pp. 1433-1433 ◽  
Author(s):  
A. Koehler ◽  
H. Shew
Keyword(s):  
United States ◽  
North Carolina ◽  
Sclerotinia Sclerotiorum ◽  
The United States ◽  
Stem Rot ◽  
Stem Tissue ◽  
Causal Organism ◽  
Broad Institute ◽  
Stem Lesions ◽  
Β Tubulin

Stevia (Stevia rebaundiana Bertoni) is an emerging perennial crop in the United States. The crop is grown for 3 to 5 years with two harvests per growing season. Stevia contains numerous glycosides that are used as a natural noncaloric sweetener, and in 2008 was approved by the USDA as a sugar substitute. In commercial plantings of second-year stevia in North Carolina, diseased plants were observed in April and May of 2013. Diseased plants were observed in several counties in the state in fields that had been planted primarily in a corn-soybean rotation prior to stevia planting. Symptoms included wilting, chlorotic leaves, necrotic leaves at the base of the stem, bleached stem lesions, and dead plants. Symptomatic plants often also had tufts of white hyphae present on stems and large, irregularly shaped 2- to 8-mm black sclerotia frequently were present on the base of the stem. Isolations from infected stem tissue were made on potato dextrose agar amended with 50 μg/ml of streptomycin sulfate and penicillin G. Based on hyphal and sclerotial characteristics, isolates were tentatively identified as Sclerotinia sclerotiorum (Lib.) de Bary (4). Koch's postulates were confirmed on 10-week-old Stevia plants cv. G3 grown in the greenhouse in 10-cm-diameter pots containing a sterile 1:1:1 sand, loam, media mix. Oat grains infested with one isolate obtained from diseased field plants served as the inoculum. Oats were sterilized on three consecutive days, inoculated with colonized agar plugs of S. sclerotiorum, and then incubated at room temperature until they were thoroughly colonized. Three infested oat grains were buried 1 cm deep approximately 2 cm from the base of the plant in each of the six test pots and plants were observed over a 3-week period for symptoms. Symptoms developed on all plants within 5 days of inoculation. Leaves began to wilt, then turned chlorotic and necrotic, with stem lesions and sclerotia present at the base of the plant. Isolations were taken from infected stem tissue and pure cultures were prepared for molecular identification. Uninoculated control plants did not develop symptoms. Pathogen identification was confirmed using universal primers ITS 4,5 and β-tubulin (2,3). Mycelium from the cultured greenhouse stem isolations were grown in potato dextrose broth. Mycelium samples were aspirated and lyophilized prior to DNA extraction. Extracted DNA was amplified through PCR with ITS and β-tubulin primers and sent for sequencing. Sequences were aligned using CLC Workbench. Sequences from ITS45 had 100% identity to S. sclerotiorum GenBank Accession No. KF859933.1, confirming S. sclerotiorum as the causal organism. The β-tubulin sequence was compared against the Broad Institute S. sclerotiorum whole genome shotgun sequence and was confirmed to have 100% identity to the beta tubulin chain (5). This is the first report of S. sclerotiorum on stevia in the United States. Chang et al. (2) reported a stem rot of stevia in Canada and confirmed S. sclerotiorum as the causal organism. References: (1) K. Chang et al. Plant Dis. 81:311, 1997. (2) J. Freeman et al. Eur. J. Plant Pathol. 108:877, 2002. (3) N. L. Glass and G. C. Donaldson. Appl. Environ. Microbiol. 61:1323, 1995. (4) J. E. M. Mordue and P. Holliday. CMI No. 513, 1976. (5) Sclerotinia sclerotiorum Sequencing Project, Broad Institute of Harvard and MIT. Online: http://www.broadinstitute.org/ , accessed July 16, 2014.

scholarly journals Effect of Plant Age and Acibenzolar-S-methyl on Development of Downy Mildew of Basil

HortScience ◽  
2014 ◽  
Vol 49 (11) ◽  
pp. 1392-1396 ◽  
Author(s):  
Jaimin S. Patel ◽  
Shouan Zhang ◽  
Maria I. Costa de Novaes
Keyword(s):  
United States ◽  
Downy Mildew ◽  
The United States ◽  
Ocimum Basilicum ◽  
Plant Age ◽  
Management Tools ◽  
Management Measures ◽  
Progress Curve ◽  
Recent Emergence ◽  
Culinary Herb

Sweet basil (Ocimum basilicum) is an important annual culinary herb grown in the United States. Recently, basil production was drastically affected by downy mildew caused by Peronospora belbahrii, a recently discovered foliar disease of basil in Homestead, FL. The disease has spread to more than 30 states in the United States causing significant losses to basil growers. As a result of the recent emergence of the disease, limited management tools are available for control of downy mildew, and it is critical for growers to apply management measures at appropriate times. This study was designed to evaluate 2- to 7-week-old basil plants for their susceptibility to downy mildew. Another objective of the study was to evaluate the effect of a pre-inoculation application of acibenzolar-S-methyl (ASM) for control of downy mildew. The results suggested that 2- to 3-week-old basil was more susceptible to downy mildew than 4- to 7-week-old plants. The area under the disease progress curve (AUDPC) was smaller for 5- to 7-week-old ASM-treated basil plants than for 2- to 4-week-old ASM-treated basil plants. This study indicated that 2- to 3-week-old basil plants need to be protected, and ASM should be applied before pathogen infection on 5- to 7-week-old plants to reduce downy mildew to a greater extent.

scholarly journals First Report of Clubroot on Canola Caused by Plasmodiophora brassicae in North Dakota

Plant Disease ◽  
2014 ◽  
Vol 98 (10) ◽  
pp. 1438-1438 ◽  
Author(s):  
K. Chittem ◽  
S. M. Mansouripour ◽  
L. E. del Río Mendoza
Keyword(s):  
United States ◽  
North Dakota ◽  
Plasmodiophora Brassicae ◽  
The United States ◽  
Soil Samples ◽  
Pcr Analysis ◽  
Infested Soil ◽  
First Report ◽  
Resting Spores ◽  
Pathogenicity Tests

North Dakota leads the United States in canola (Brassica napus L.) production (4). A canola field with a distinct patch of dead plants spreading over an area of approximately 0.4 ha was detected in Cavalier County, North Dakota, in early September 2013. Numerous spots within the patch had plant mortalities >80%. Dead plants pulled from the soil had roots with severe galling and clubbing. Clubbed roots were brittle and disintegrated easily when pressed between fingers. Root and soil samples collected at several locations within and outside the affected patch were pooled in separate groups. All plants collected in the patch were symptomatic but those collected outside were not. In the lab, total genomic DNA from three symptomatic and two healthy root samples was extracted using standard procedures and freehand slices were prepared for observation with a compound microscope. Also, DNA from pooled soil samples was extracted using FastDNA Spin Kit for Soil (MP Biomedicals, Solon, OH). Round resting structures ranging from 2.2 to 4.2 μm in diameter were observed by microscopic examination of symptomatic root tissues. These structures resembled those typically produced by Plasmodiophora brassicae Woronin. This initial identification was later confirmed through PCR analysis using the species specific primers TC1F/R and TC2F/R (1). PCR products of 548 bp (TC1F/R) and 519 bp (TC2F/R) were produced in the three symptomatic and two infested soil samples, confirming the presence of P. brassicae. PCR amplicons were not detected in healthy root and soil samples. Pathogenicity tests were conducted in greenhouse to fulfill Koch's postulates. Briefly, five square plastic pots (10 × 10 × 13 cm) were filled with a 10-cm layer of Sunshine Mix #1 potting mix (Fison Horticulture, Vancouver, BC, Canada) and then 1 g of ground root galls (approximately 5 × 105 resting spores) was spread evenly on its surface and covered with 2 cm of soilless mix. A similar number of pots were filled only with soilless mix and used as controls. All pots were planted with two seeds of canola cv. Westar and incubated in greenhouse conditions at 21°C and 16 h light daily. The experiment was conducted twice. Four weeks after planting, all plants in the inoculated pots had developed galls while plants in control pots were symptomless. Presence of P. brassicae resting spores in the newly developed galls was confirmed by microscopic observations and PCR. Based on the symptoms, morphology of resting spores, PCR reactions, and pathogenicity tests, we confirm the presence of P. brassicae on canola. While P. brassicae has been reported as widespread in North America (2), to our knowledge, this is the first report of clubroot on canola in North Dakota and the United States. Clubroot became the most important disease affecting canola production in central Alberta, Canada, within 5 years of its discovery in 2003 (3); since then, the disease has been detected in Saskatchewan and Manitoba (3), Canadian provinces that share borders with North Dakota. Considering the difficulties in management of clubroot, measures should be initiated to limit the spread of the disease before it could pose a threat to United States canola production. References: (1) T. Cao et al. Plant Dis. 91:80, 2007. (2) G. Dixon J. Plant Growth Regul. 28:194, 2009. (3) S. Strelkov and S. Hwang. Can. J. Plant Pathol. 36(S1):27, 2014. (4) USDA-NASS, Ag. Statistics No. 81, 2012.

scholarly journals Cross Pathogenicity and Vegetative Compatibility of Fusarium oxysporum Isolated from Sugar Beet

Plant Disease ◽  
2013 ◽  
Vol 97 (9) ◽  
pp. 1200-1206 ◽  
Author(s):  
Kimberly M. Webb ◽  
Austin J. Case ◽  
Mark A. Brick ◽  
Kris Otto ◽  
Howard F. Schwartz
Keyword(s):  
United States ◽  
Phaseolus Vulgaris ◽  
Sugar Beet ◽  
Fusarium Oxysporum ◽  
The United States ◽  
Population Diversity ◽  
Vegetative Compatibility ◽  
Pathogenic Variation ◽  
Dry Edible Bean ◽  
Reliable Methods

Fusarium oxysporum f. sp. betae causes Fusarium yellows in sugar beet (Beta vulgaris). The F. oxysporum population from sugar beet can be highly variable in virulence and morphology and many isolates are nonpathogenic. Rapid and reliable methods to identify pathogenic isolates from nonpathogenic F. oxysporum generally are unavailable. Little is known about nonpathogenic isolates, including the role they may play in population diversity or virulence to sugar beet. Sugar beet is often grown in rotation with other crops, including dry edible bean (Phaseolus vulgaris) and onion (Allium cepa), with F. oxysporum able to cause disease on all three crops. Thirty-eight F. oxysporum isolates were collected from symptomatic sugar beet throughout the United States to investigate diversity of the F. oxysporum population and the influence of crop rotation on pathogenic variation. These isolates were characterized for pathogenicity to sugar beet, dry edible bean, and onion, as well as vegetative compatibility. Pathogenicity testing indicated that some F. oxysporum isolates from sugar beet may cause disease on onion and dry edible bean. Furthermore, vegetative compatibility testing supported previous reports that F. oxysporum f. sp. betae is polyphyletic and that pathogenic isolates cannot be differentiated from nonpathogenic F. oxysporum using vegetative compatibility.

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