bluuebunny/crossref_metadata_2025 huggingface dataset:
First Report of Downy Mildew Disease of Rose Caused by Peronospora sparsa in KwaZulu Natal, Southern Africa
Authors: Achar P. N.
Published: May 2007

In October and November of 1996, typical downy mildew symptoms appeared on rose plants cultivated in many areas in KwaZulu Natal, South Africa. White mycelial mats were observed on the lower surface of young and mature leaves and on stems at the base of the plants and shoot apices. Leaves and stems developed purplish to black spots. Flowers and buds had downy mildew-like growth on peduncles, calyces, and petals. Plants were poorly developed and generally chlorotic, and several were stunted. The most severe symptoms included premature leaf drop followed by plant death. The fungus from leaf and stem lesions was identified microscopically as Peronospora sparsa based on the following characteristics: conidia, sub-elliptical ranging from 20 to 23 μm long and 14.0 to 18.0 μm wide; conidiophores 150 to 350 μm long and 6 to 10 μm wide. Conidiophores protruded through the stomata as bunches of slender structures bearing conidia at the tips. The optimum temperature for sporulation and germination was 18°C. Artificially inoculated healthy mature leaves and stems developed purplish to dark brown lesions similar to those described from the field samples. The fungus was confirmed on the artificially inoculated tissues to complete Koch's postulates. The disease has been reported in all rose growing regions in KwaZulu Natal and causes up to 100% losses in some areas since its first appearance towards the beginning of winter 1996. The president of the Natal Rose Society, KwaZulu Natal, predicts that in the year 2000 rose plants may be eliminated if immediate control measures for Peronospora sparsa are not implemented. Rose is grown for local needs and has high export value in South Africa. This is the first report of the downy mildew of rose caused by Peronospora sparsa in South Africa.
Coniothyrium minitans on Apothecia of Sclerotinia trifoliorum
Authors: Wang L. , Vincelli P.
Published: May 2007

During a study of apothecial dynamics of Sclerotinia trifoliorum at the University of Kentucky Spindletop Farm at Lexington, an apothecium with small black patches on the surface of the hymenium was found. The affected apothecium was incubated in a moist chamber at room temperature. After 3 days, white, cottony mycelium was observed on the surface of the hymenium; pycnidia formed in the mycelium and around the stipe of the apothecium several days later. The apothecium eventually decayed and shrunk. Pycnidia measured 168 to 520 μm (mean 311 μm). Pycnidiospores were dark brown en masse; they were ovoid to ellipsoid, measuring 3.1 to 8.2 μm (mean 6.0 μm) in length and 3.1 to 4.1 μm (mean 3.7 μm) in width, and were faintly verrucose. Fresh sclerotia of S. trifoliorum were produced in vitro and then inoculated with pycnidiospores produced on potato dextrose agar. Inoculated sclerotia were incubated in a moist chamber at room temperature. After 7 to 10 days, inoculated sclerotia shriveled and decayed, pycnidia formed on their surfaces, and the same fungus was isolated. The fungus was identified as Coniothyrium minitans Campbell. Among 58 apothecia examined in the field on 1 November, three were apparently parasitized; pycnidia developed on one of these following a 3-day incubation. Weather conditions during the preceding 2 weeks had been generally humid with above-normal temperatures (daily mean air temperature range and interquartile range were 4.0 to 20.0 and 8.9 to 16.1°C, respectively), which may have favored activity of the mycoparasite. C. minitans was reported by Campbell (1) in California on sclerotia formed in cultures of Sclerotinia sclerotiorum. It causes decay of sclerotia of several Sclerotinia spp., some Botrytis spp., and Sclerotium cepivorum in soil. Consequently, it may have considerable biological control potential. It has been recorded in 29 countries and on all continents except South America (2). The fungus previously has been isolated from only sclerotia or, in a few instances, directly from soil. This is the first report on C. minitans parasitic on apothecia collected from the field.

References: (1) W. A. Campbell. Mycologia 39:190, 1947. (2) C. Sandys-Winsch et al. Mycol. Res. 97:1175, 1993.
Effects of Endophytic Infection by Fusarium moniliforme on Corn Growth and Cellular Morphology
Authors: Yates I. E. , Bacon C. W. , Hinton D. M.
Published: May 2007

Kernels of corn, Zea mays, were inoculated with Fusarium moniliforme to analyze seedling growth and development during endophytic, symptomless infection. In planta F. moniliforme distribution and seedling growth, expressed as shoot diameter, plant height, leaf length, and dry weight, were examined weekly for 28 days after planting. Even though no visible disease symptoms developed, F. moniliforme was isolated from most segments taken from seedlings grown from inoculated, but not noninoculated, kernels from the earliest to the latest sampling. F. moniliforme did not alter the rate or percentage of kernel germination, but seedlings grown from inoculated kernels had suppressed shoot diameter, plant height, leaf length, and plant weight 7 days after planting. However, seedling growth from inoculated kernels was similar to or greater than that from noninoculated kernels at 28 days. Histological modifications in seedlings grown from inoculated kernels included accelerated lignin deposition in shoots and modified chloroplast orientation in leaves. In summary, gross morphology and histology were altered in corn seedlings during symptomless, endophytic infection by F. moniliforme.
Weather Variables Associated with Infection of Tomato Fruit by Colletotrichum coccodes
Authors: Sanogo S. , Pennypacker S. P. , Stevenson R. E. , MacNab A. A.
Published: May 2007

Field experiments were conducted to determine the relationship of tomato anthracnose to weather variables. Sixteen potted tomato plants were exposed to field conditions within rows of tomato plants for 4 consecutive days at various time periods during the 1993 and 1994 summer growing seasons. Incidence of fruit infection by Colletotrichum coccodes was correlated with rain variables (amount and duration of rain) alone and in combination with other meteorological factors. The best fitting regression equation, accounting for 72% of the variation in anthracnose incidence (arcsine-square root transformed), was Y = 111.77 - 1.16 HNRo, in which HNRo is the numbers of hours during which no rainfall occurs within 4-day intervals that tomato fruit were exposed to field conditions in central Pennsylvania.
Quantitative Relationship Between Leaf Rust and Wheat Yield in Mississippi
Authors: Khan M. A. , Trevathan L. E. , Robbins J. T.
Published: May 2007

Yield losses in wheat (Triticum aestivum) caused by leaf rust were evaluated in cultivar trials at five locations in Mississippi over a 4-year period from 1986 through 1989. Different levels of disease developed in the various trials over the 4-year period. There was no significant interaction between location and cultivar when yield data were collected from sites in the north and central areas of the state. A model derived from data for eight cultivars at two locations showed a negative linear relationship between yield and leaf rust. Total grain yield was reduced by 1% for each 1% increase in rust when the percentage flag leaf area covered by pustules was assessed visually at Feekes stage 11.1. Using this model, and rust ratings from three additional locations, predicted yields were statistically similar to recorded yields.
Effects of Soil Water Content and Soil Temperature on Efficacy of Metham-Sodium Against Verticillium dahliae
Authors: Saeed I. A. M. , Rouse D. I. , Harkin J. M. , Smith K. P.
Published: May 2007

Soil column studies were conducted to investigate the influence of soil water content and temperature on the efficacy of metham-sodium and its degradation product methyl isothiocyanate against Verticillium dahliae. The viability of the microsclerotia (MS) of the fungus in the top 30 cm of fumigated and control columns was measured. Temperatures for studies were 2 or 22°C, and the soil water content, expressed as soil matric potential, varied from -23 (wet), -113 (moist), to -2485 J/kg (dry). There was a significant interaction of soil water content and temperature on the efficacy of metham-sodium against V. dahliae MS. For the low soil temperature (2°C) the fumigant was more effective against MS of the fungus in wet than in moist or dry soil Soil water content did not affect fungicidal activity of metham-sodium when the soil columns were maintained at 22°C. These results suggest that the fumigant has a greater efficacy against V. dahliae in wet/cold soil conditions compared to the other conditions tested. Consequently, it was recommended that metham-sodium be applied to fields by chemigation in late fall or early spring to obtain efficacious results.
Viruses of White Clover in Pastures of Pennsylvania, New York, and Vermont
Authors: Sherwood Robert T.
Published: May 2007

Incidence of six viruses was tested in white clover from 28 rotationally grazed pastures of Pennsylvania (PA), New York (NY), and Vermont (VT). Each of 17 PA pastures was sampled fall 1994, spring 1995, fall 1995, and spring 1996, and 10 pastures were sampled fall 1996. Each of five NY and six VT pastures was sampled spring and fall 1995 and 1996. Enzyme-linked immunosorbent assays (ELISA) were conducted for red clover vein mosaic virus (RCVMV), white clover mosaic virus (WCMV), alfalfa mosaic virus (AlMV), peanut stunt virus (PSV), clover yellow mosaic virus (CYMV), and the potyvirus group (POTY). RCVMV, WCMV, AlMV, and POTY were detected in 28, 28, 27, and 25 of the 28 pastures and in 67, 32, 30, and 7% of the 3,065 samples tested, respectively. PSV occurred at low to moderate levels in 11 PA pastures. PSV was rare in NY and was not detected in VT. CYMV was never found. Incidence of each virus varied significantly among pastures. For any given virus, there was not a significant variation in incidence among sampling dates within the NY-VT samples. RCVMV, WCMV, and POTY varied among dates within PA.
Sodium Hypochlorite: Effect of Solution pH on Rice Seed Disinfestation and Its Direct Effect on Seedling Growth
Authors: Chun S.-C. , Schneider R. W. , Cohn M. A.
Published: May 2007

Bacteria were completely eliminated from rice seeds following immersion in household bleach solutions (50% bleach and 2.6% NaOCl) adjusted to pH 7.0 in 0.5 M potassium phosphate, while fungi were eliminated at pH 5.0 and below. Mercuric chloride was used to disinfest non-dormant rice seeds in order to test the direct effect of sodium hypochlorite on rice seedling growth apart from an indirect effect related to elimination of microbial contaminants. Seeds were immersed for 2 h in each solution or water in each of the following treatments: (i) sterilewater followed by sterile water, (ii) HgCl2(1,000 μg/ml) followed by sterile water, (iii) HgCl2followed by KH2PO4(0.3 M), (iv) HgCl2followed by NaOCl, and (v) NaOCl followed by sterile water. Sodium hypochlorite solutions were prepared in 0.3 M potassium phosphate, which gave a final pH of 7.3. Seedling growth in treatments in which seeds were treated with HgCl2followed by NaOCl, and NaOCl followed by sterile water, was significantly greater than those treatments in which seeds were treated with sterile water followed by sterile water, HgCl2followed by sterile water, and HgCl2followed by KH2PO4. Sodium hypochlorite stimulated rice seedling growth directly, as opposed to an indirect effect related to elimination of microbial contaminants or alleviation of dormancy.
Thyronectria balsamea on Abies fraseri in Pennsylvania and North Carolina
Authors: Wenner N. G. , Merrill W. , Moody J. T.
Published: May 2007

In August 1996, several 4- to 6-m-tall Abies fraseri (Pursh) Poir. in Adams County, PA, were found bearing numerous dead branches and/or dead tops. The trees had been severely stressed by being ball-and-burlapped and replanted in 1993. Distinct cankers occurred between the living and dead portions of stems and branches. Associated with these cankers were abundant, reddish-orange, erumpent stroma, each bearing three to 10 similarly colored cupulate ascomata. The latter contained asci bearing two to four large, muriform ascospores that, as they matured, formed large numbers of small ascoconidia, indicating the pathogen was Thyronectria balsamea (Cooke & Peck) Seeler (= Nectria balsamea Cooke & Peck). In September 1996, cankered dead stems and branches from affected A. frasrei Christmas tree plantations in Avery County, NC, were found bearing the same pathogen. This fungus is known on A. bal-samea (L.) Mill. from northern Minnesota east through Canada to northern New York and Newfoundland (2). Funk (1) reported it from A. lasio-carpa (Hook.) Nutt. in (presumably) British Columbia, but gave no details. This is the first report of it in the eastern United States south of northern New York, a considerable extension of its known range, and the first report of it from A. fraseri. Voucher specimens are in PACMA (Pennsylvania State University Mycologica Herbarium, Mont Alto Campus).

References: (1) A. Funk. Can. For. Serv. BC-X-222:142, 1981. (2) E. V. Seeler, Jr. J. Arnold Arbor. 21:442, 1940.
Detection of Bermuda Grass White Leaf Disease in Italy and Characterization of the Associated Phytoplasma by RFLP Analysis
Authors: Marcone C. , Ragozzino A. , Seemüller E.
Published: May 2007

Bermuda grass showing symptoms of a white leaf disease has been observed in fruit orchards, vegetable fields, and uncultivated areas in the Latium and Campania regions of central and southern Italy. Using polymerase chain reaction (PCR) amplification with phytoplasma-specific primers, all symptomatic plants tested positively; whereas no amplification product was obtained from nonsymptomatic plants. Restriction fragment length polymorphism (RFLP) analysis of the PCR-amplified ribosomal DNA revealed a uniform pattern that was similar to that of the Bermuda grass white leaf phytoplasma collected in Thailand, which is known to be a member of the sugarcane white leaf phytoplasma group. By RFLP analysis, the phytoplasma infecting Bermuda grass could be distinguished from other group members, including the phytoplasmas associated with sugarcane white leaf and Brachiaria white leaf. This is the first report on the presence of the Bermuda grass white leaf phytoplasma in Europe.
Impact of Temperature, Osmotic Potential, and Osmoregulant on the Growth of Three Ectotrophic Root-Infecting Fungi of Kentucky Bluegrass
Authors: Plumley Karen A. , Gould Ann B. , Clarke Bruce B.
Published: May 2007

Two isolates each of Magnaporthe poae, Gaeumannomyces incrustans, and Leptosphaeria korrae were grown at 25°C in liquid shake culture in minimal salts medium (-0.12 MPa) or minimal salts medium adjusted to -0.5 MPa with KCl, MgCl2, or polyethylene glycol (PEG). Fungal dry weight of all three species was greater in minimal salts medium amended to -0.5 MPa with MgCl2 than in nonamended medium, and dry weight in medium amended with PEG was not different from dry weights in nonamended medium or medium amended with KCl. Fungi were incubated at varying temperatures on a minimal salts solid-agar medium (-0.12 MPa) adjusted to osmotic potentials ranging from -0.5 to -5.0 MPa with KCl or MgCl2. Optimum growth of M. poae, G. incrustans, and L. korrae on nonamended medium occurred at 30, 30, and 25°C, respectively. At optimum temperatures for each species, fungal growth was greatest at the higher osmotic potentials tested (-0.5 to -1.0 MPa) and decreased in a linear manner as osmotic potential decreased. In most cases, growth was detected at the lowest osmotic potential measured (-5.0 MPa). The relationship of fungal growth to osmotic potential depended on both temperature and osmoregulant. At temperatures optimal or nearly optimal for fungal development, the growth of all three fungi declined more rapidly with decreasing osmotic potential when grown on medium amended with MgCl2 than on medium amended with KCl. At the highest temperature evaluated for growth of M. poae and L. korrae (35 and 30°C, respectively), growth on medium amended with KCl was curvilinear and peaked at osmotic potentials of -2.5 to -3.0 MPa. Furthermore, between osmotic potentials of -2.0 and -5.0 MPa, M. poae grew best at 35°C. When maintained on nonamended minimal salts medium (-0.12 MPa) in liquid culture at 25°C or on nonamended solid-agar medium at temperatures optimal for growth, M. poae grew at a faster daily rate than L. korrae.
Spatial and Temporal Patterns of Aspergillus flavus Strain Composition and Propagule Density in Yuma County, Arizona, Soils
Authors: Orum Thomas V. , Bigelow Donna M. , Nelson Merritt R. , Howell Donald R. , Cotty Peter J.
Published: May 2007

Aspergillus flavus isolates from Arizona can be divided into S and L strains on the basis of sclerotial morphology. These genetically distinct strains differ in aflatoxin production. To help understand factors influencing the aflatoxin producing potential of A. flavus communities, spatial and temporal patterns of strain incidence were compared with patterns of A. flavus propagule density in Yuma County soils. Strain S isolates were found in all sampled fields, but the percentage of strain S isolates ranged from 4 to 93%. A nested analysis of variance was used to determine the spatial scale at which most variability in strain composition and propagule density occurred. For both variables, the largest component of variance occurred among fields within areas at a spatial scale of 1 to 5 km. There was also spatial structure (12 to 21% of the variance) at the subregional level (> 20 km) in strain composition, but not in propagule density. Temporal patterns for both variables were similar. The sampling periods with the highest incidence of strain S isolates, August 1994 (60%) and July 1995 (62%), occurred during cotton boll formation. The regional average for A. flavus propagule density was near 1000 propagules/g in the summer, but less than 100 propagules/g in the spring. The results suggest that insights into factors influencing the toxigenicity and propagule density of A. flavus communities might be achieved most readily by contrasting fields in close spatial proximity.
Number of Tebuconazole Applications for Maximizing Disease Control and Yield of Peanut in Growers' Fields in Alabama
Authors: Bowen K. L. , Hagan A. K. , Weeks J. R.
Published: May 2007

Disease and yields of peanut were monitored in growers' fields treated with zero, one, two, three, and four applications of tebuconazole. Yields ranged from 1,918 to 6,891 kg/ha and averaged 4,319 kg/ha over eight locations in 3 study years. Defoliation caused by peanut leaf spots (Cercospora arachidicola and Cercosporidium acutatum) and incidence of southern stem rot (Sclerotium rolfsii) were inversely related to number of tebuconazole applications, while yield was directly related to number of tebuconazole applications. Average yields with zero, one, two, and four tebuconazole applications (each application at 0.25 kg a.i./ha) were 3,609, 4,088, 4,526, and 4,868 kg/ha, respectively. Data from each location were best modeled by quadratic equations allowing determination of numbers of tebuconazole applications for minimal disease and maximal yields. Calculated spray numbers indicate that between three and four applications of tebuconazole is best for disease control and yield maximization.
Blue-stain Fungi Associated with Roots of Southern Pine Trees Attacked by the Southern Pine Beetle, Dendroctonus frontalis
Authors: Otrosina William J. , Hess Nolan J. , Zarnoch Stanley J. , Perry Thelma J. , Jones John P.
Published: May 2007

Forty paired plots were established from eastern Texas to Alabama to study root-infecting, blue-stain fungi in southern pine stands undergoing southern pine beetle (SPB) attack. Woody roots were sampled in plots undergoing recent or current attack by the SPB. Comparisons were made between occurrence of Leptographium spp. and related fungi and data on various characteristics of natural stands and plantations studied. Three fungal species, L. terebrantis, L. procerum, and Ophiostoma ips, along with unidentified Leptographium and Graphium species, were isolated from sampled roots. L. terebrantis was isolated more frequently from SPB-attacked plots (P < 0.001) than was either L. procerum or O. ips. More blue-stain fungal species and related genera were isolated from SPB-attacked plots than from control plots (P < 0.001). This also was true for combined isolation percentages of L. terebrantis, L. procerum, and O. ips (P = 0.03). Presence of blue-stain fungi also was associated with higher stand basal area in the control plots (P = 0.045). Isolation frequencies of O. ips and L. procerum, along with the combination of these fungal species with L. terebrantis, were logistically related to increasing stand basal area in the control plots (P = 0.02, 0.02, and 0.01, respectively). No logistic relationship was found for frequency of any of the three blue-stain species with respect to basal area in SPB-attacked plots. These results suggest blue stain fungi are important in the dynamics of susceptibility of southern pines to SPB attack.
Differential Cultivars and Criteria for Evaluating Resistance to Rhizoctonia solani in Seedling Brassica oleracea
Authors: Keinath Anthony P. , Farnham Mark W.
Published: May 2007

Growth-room and field experiments were conducted to develop methods of studying resistance in Brassica oleracea crops to Rhizoctonia solani anastomosis groups (AG) 2-1 and 4, causal agents of wirestem. Seedlings of 12 cultivars (3 each of broccoli, cauliflower, cabbage, and collard) at the four- to five-leaf stage were transplanted to trays in a growth room and covered with steamed soil infested with cornmeal-sand cultures or sclerotia of R. solani or to fumigated field plots infested with sclerotia. The percent healthy, diseased, and dead plants was assessed every 3 to 5 days for 2 weeks in the growth room and for 3 weeks in field trials. At harvest, plants were dug out with roots intact and rated for wirestem severity. In most experiments, wirestem incidence (percent diseased and dead plants) stabilized within 10 to 14 days after inoculation. Inoculation with cornmeal-sand cultures of both AGs and sclerotia of AG-4 resulted in severe wirestem in all experiments, whereas sclerotia of AG-2-1 were less effective in the growth room and not effective in the field. Percent healthy and surviving (healthy plus diseased) plants, area under the disease progress curve (AUDPC), and wirestem severity all separated the most susceptible from the partially resistant cultivars more consistently than fresh weight of inoculated plants expressed as a percentage of noninoculated plant weight. Wirestem severity and AUDPC were always negatively and significantly (P ≤ 0.01) correlated with percent healthy plants. Although genotype by environment interactions were observed, the cauliflower cvs. Snowcone and Snow Crown were severely diseased in all experiments, whereas collard cv. Blue Max was consistently and significantly (P ≤ 0.05) less diseased.
Evidence for the Association of a Bipartite Geminivirus with Tomato Leaf Curl Disease in Pakistan
Authors: Mansoor S. , Khan S. H. , Saeed M. , Bashir A. , Zafar Y. , Malik K. A. , Markham P. G.
Published: May 2007

Tomato leaf curl disease is the most important constraint on tomato production in Pakistan, where it is found throughout the country. The disease, which occurs in high incidence in Punjab and Sindh provinces, causes 30 to 40% yield losses in the spring crop and uneconomically high losses when grown as an autumn crop. The symptoms of the disease include upward or downward leaf curling, vein thickening, and stunting of the plant. The disease is transmitted by Bemisia tabaci whiteflies (non-B, biotype K) and is suspected to be caused by a geminivirus. For the detection of geminivirus, total DNA was extracted from infected plants, fractionated in an agarose gel, transferred to a nylon membrane, and Southern blotted. A full-length clone of DNA-A of cotton leaf curl virus from Pakistan (S. Mansoor, I. Bedford, M. S. Pinner, A. Bashir, R. Briddon, J. Stanley, Y. Zafar, K. A. Malik, and P. G. Markham, unpublished) was labeled with [32P]dCTP by the oligo-labeling method and hybridized at medium stringency. Geminivirus DNA forms that are normally found in infected plants were detected in plants with tomato leaf curl disease but not in healthy plants. To further confirm the presence of a whiteflytransmitted geminivirus, universal primers for dicot-infecting geminiviruses (1) were used in polymerase chain reaction (PCR) and a product of expected size (approximately 2.7 kb) was detected. The 2.7-kb PCR-amplified DNA from diseased tomato plants was labeled with [32P]dCTP and used as probe in Southern hybridization. This probe also detected geminivirus DNA forms at medium stringency. Both monopartite and bipartite geminiviruses transmitted by whiteflies have been reported to cause leaf curl symptoms on tomato from the Eastern hemisphere. Degenerate primers (PBLv2040 and PCRc1), which amplify B component DNA, were used to determine if tomato leaf curl was monopartite or bipartite (2). A product of expected size (0.65 kb) was amplified, suggesting this virus to be bipartite. DNA-B PCR product obtained from diseased tomato plants was hybridized as described above and detected geminivirus DNA forms at medium stringency. Samples of diseased tomato plants were collected from tomato fields throughout Punjab. DNA-A was detected in all 20 samples whereas DNA B was detected in 17 samples when hybridized by dot blot method at medium stringency. Our data show that tomato leaf curl virus from Pakistan is a bipartite geminivirus. This is the first evidence for a bipartite geminivirus in tomato plants from Pakistan.

References: (1) R. W. Briddon and P. G. Markham. Mol. Biotechnol. 1:202, 1993. (2) M. R. Rojas et al. Plant Dis. 77:340, 1993.
First Report of Broad Bean Wilt Fabavirus on Polygonum fagopyrum
Authors: Bellardi M. G. , Rubies-Autonell C.
Published: May 2007

Buckwheat (Polygonum fagopyrum L.) is an annual medicinal plant useful in convalescence and treatment of anemia. It is widely grown in Europe, where it is sometimes used as human food. In a survey made during 1995 to 1996 in the Emilia-Romagna region (northern Italy), a virus was consistently isolated from plants showing yellow or chlorotic mottle on the leaves. It was mechanically transmitted to herbaceous hosts, including Chenopodium amaranticolor Coste et Reyn., C. murale L., C. quinoa Willd., Gomphrena globosa L., and Vicia faba L. (which showed systemic vein clearing, necrosis of terminal leaves, wilting, and death) and identified by indirect enzyme-linked immunosorbent assay (PAS-ELISA, using A protein) as broad bean wilt fabavirus (BBWV) serotype I. Moreover, elongated, potyvirus-like particles, 750 nm in length, were observed by electron microscopy of leaf dips from symptomatic leaf samples of P. fagopyrum. These particles were identified as turnip mosaic potyvirus (TuMV) on the basis of differential host reactions and by serological assays, including PAS-ELISA, immunoelectron microscopy, and gold-labeled antibody decoration. Both BBWV and TuMV may have been transmitted to P. fagopyrum by the abundant aphid populations from other medicinal plants cultivated in the same location. In particular, Digitalis lanata Ehrh. and Hesperis matronalis L. were found to be infected by the same two viruses (50% of diseased plants). This note represents the first report of BBWV, alone or in mixed infections with TuMV, in P. fagopyrum.
First Report of Phytophthora cinnamomi Root Rot, Stem, and Leaf Blight on Ivy
Authors: Thinggaard K. , Toppe B.
Published: May 2007

Phytophthora cinnamomi was isolated from varieties of Hedera helix pot plants in 1989 in two Danish greenhouse nurseries. The symptoms were brown, rotten roots and stems, and brown areas developing from the base of the leaves. The fungus was isolated directly from roots, stems, leaves, and soil, and by baiting the nutrient solutions of the watering systems with needles of Cedrus deodara. The fungus was isolated on Phytophthora selective agar medium containing hymexazol and identified with the keys of Kröber (1) and Stamps et al. (2). The fungus was characterized by coralloid hyphal swellings, chlamydospores, lack of oogonia in single culture, and production of numerous, ovoid sporangia with a nonpapillate, wide pore. The sporangia produced many zoospores after 2 days flooding with autoclaved pond water on V8 juice agar, followed by internal proliferation. The fungus was also isolated in Norway in 1993 from ivy pot plants. The fungus was widespread in Danish and Norwegian pot plant nurseries in 1997 and caused losses in most varieties, especially at temperatures above 23°C. Effective fungicides are not available for use in Denmark and the disease is easily spread with cuttings, and through the watering system with recirculation of the nutrient solution. A Danish isolate of P. cinnamomi originating from roots of H. helix was used in a pathogenicity test. Five-week-old cuttings were inoculated by adding zoospores (5 per ml) to the recirculating nutrient solution. Control plants were on a separate bench with nutrient solution without the fungus. After 1 week, symptoms of root rot were observed, and 2 weeks after inoculation, 75% of plants expressed severe symptoms on roots, stems, and leaves. P. cinnamomi was reisolated from roots, stems, and leaves of diseased plants, but was not isolated from the control plants. The reisolate was morphologically identical to the original isolate. This is the first report of P. cinnamomi from ivy in Europe.

References: (1) H. Kröber. Mitt. Biol. Bundesanst. Land Forstwirtsch. Berlin-Dahlem 225:73, 1985. (2) D. J. Stamps et al. 1990. Mycol. Pap. No. 162. CAB Int. Mycol. Inst., Kew, England.
Immunological Detection of a GarV-Type Virus in Argentine Garlic Cultivars
Authors: Helguera Marcelo , Bravo-Almonacid Fernando , Kobayashi Ken , Rabinowicz Pablo D. , Conci Vilma , Mentaberry Alejandro
Published: May 2007

A cDNA library representing the genomes of several garlic viruses was generated using a viral RNA mixture as template. Analysis of randomly selected clones allowed the identification of different viral genomic sequences. On the basis of amino acid and nucleotide sequence comparisons, one of them was assigned to garlic virus A (GarV-A), a novel flexuous, rod-shaped virus recently reported in Japan. The coat protein (CP) of this virus was expressed in Escherichia coli cells and used as immunogen to produce polyclonal antibodies. The expression protein was recognized by an antiserum detecting garlic mite-borne filamentous virus, but did not react with antibodies specific for other garlic viruses. Antibodies raised against the viral CP reacted with extracts infected with garlic mite-borne viruses and fail to recognize preparations of onion yellow dwarf potyvirus, leek yellow stripe potyvirus, and carnation latent carlavirus. The same antibodies decorated viral particles exhibiting a modal length of 586 nm in immuno electron microscopy with decoration assays. Double-antibody enzyme-linked immunosorbent assays and tissue printing assays performed with these antibodies allowed detection of GarV-A in most garlic cultivars used in Argentina.
Aggressiveness of Stagonospora nodorum Isolates Obtained from Wheat in the Northern Great Plains
Authors: Krupinsky J. M.
Published: May 2007

Isolates of Stagonospora nodorum, obtained from diseased wheat leaves collected in fields in Montana, North Dakota, and South Dakota, were tested on detached seedling leaves of wheat and found to be pathogenic. Differences among isolates chosen at random were detected in the first phase of the inoculations. Isolates associated with severe and mild symptom severity, as measured by lesion size, were selected in phase two. Isolates associated with severe and mild symptom severity were statistically differentiated in phase three. The ability of isolates to cause significant differences in symptom severity was interpreted as differences in aggressiveness. The differences among isolates detected with detached leaf experiments was confirmed with glasshouse inoculations of seedling wheat plants. The high aggressive isolates consistently produced higher symptom severity on wheat seedlings, as measured by percentage necrosis, than low aggressive isolates. Cultivars were consistently differentiated with isolates associated with different levels of aggressiveness. With unselected isolates, the cultivar × isolate interaction was nonsignificant, indicating a lack of specificity. With high and low aggressive isolates, the cultivar × isolate interaction was significant. Considering that the magnitude of the mean squares for interactions were rather low compared to the main effects, it is speculated either that specificity is detected with the present isolates but only at a low level, or that specificity is apparent only when isolate extremes are tested. With studying isolates in phases rather than random comparisons, fungal isolates associated the high and low aggressiveness can be identified and, once identified, isolates from different hosts or geographical areas can be compared in an efficient and meaningful manner.
Aggressiveness of Stagonospora nodorum Isolates from Perennial Grasses on Wheat
Authors: Krupinsky J. M.
Published: May 2007

Isolates of Stagonospora nodorum from 13 perennial grasses were tested on detached wheat leaves. Grass isolates that were consistently associated with large or small lesions were statistically differentiated. Some grass isolates were detected that were associated with large lesions on wheat (high symptom severity), but most isolates produced small lesions (mild level of symptom severity). The ability of grass isolates to cause significant differences in symptom severity, as measured by lesion length, was interpreted as differences in aggressiveness. Grass isolates that were associated with high symptom severity were found to be similar to selected wheat isolates in their level of aggressiveness. Results were confirmed with inoculations of seedling wheat plants in the glasshouse. Wheat cultivars were statistically differentiated from one another with all types of isolates. The cultivar × isolate interactions were, generally, not significant with unselected isolates, indicating a low possibility of specificity. In contrast, when isolates associated with large and small lesions were compared, the cultivar × isolate interaction was significant in most experiments, but the magnitude of the mean square for the interaction was low compared to the mean squares of the main effects. The ability of S. nodorum to infect perennial grasses would improve the likelihood of survival of this fungus between wheat crops. Because most isolates are not associated with severe symptom severity, their potential effect on wheat is probably less than would be expected considering the potential number of isolates available from the grasses.
Rapid Detection of Phytophthora infestans in Late Blight-Infected Potato and Tomato Using PCR
Authors: Trout C. L. , Ristaino J. B. , Madritch M. , Wangsomboondee T.
Published: May 2007

Late blight caused by the oomycete pathogen Phytophthora infestans is a devastating disease of potato and tomato worldwide. A rapid and accurate method for specific detection of P. infestans is necessary for determination of late blight in infected fruit, leaves, and tubers. Ribosomal DNA (rDNA) from four isolates of P. infestans representing the four genotypes US1, US6, US7, and US8 was amplified using polymerase chain reaction (PCR) and the universal primers internal transcribed spacer (ITS) 4 and ITS5. PCR products were sequenced using an automated sequencer. Sequences were aligned with published sequences from 5 other Phytophthora species, and a region specific to P. infestans was used to construct a PCR primer (PINF). Over 140 isolates representing 14 species of Phytophthora and at least 13 other genera of fungi and bacteria were used to screen the PINF primer. PCR amplification with primers PINF and ITS5 results in amplification of an approximately 600 base pair product with only isolates of P. infestans from potato and tomato, as well as isolates of P. mirabilis and P. cactorum. P. mirabilis and P. cactorum are not pathogens of potato; however, P. cactorum is a pathogen of tomato. P. infestans and P. cactorum were differentiated by restriction digests of the amplified product. The PINF primer was used with a rapid NaOH lysis technique for direct PCR of P. infestans from infected tomato and potato field samples. The PINF primer will provide a valuable tool for detection of P. infestans in potatoes and tomatoes.
The Appearance of Metalaxyl-Resistant Isolates of Phytophthora infestans in Delaware
Authors: Sedegui M. , Carroll R. B. , Morehart A. L. , Mulroony R. P. , Whalen J. M.
Published: May 2007

Prior to 1995, late blight of potatoes (Solanum tuberosum L.) caused by Phytophthora infestans (Mont.) de Bary had not been reported from Delaware for decades. In that year, the fungus was isolated from potato foliage collected from fields in the Dover area that sustained severe foliage loss due to the disease. To establish pathogenicity, potato and tomato plants grown in the greenhouse were inoculated with the isolates obtained and Koch's postulates were completed. Analyses to determine mating type, genotype at two allozyme loci (2), Gpi and Pep, and sensitivity to metalaxyl were also completed. Measurements were made every 5 days and EC50 values were calculated for radial mycelial growth on metalaxyl-amended agar, for leaflets inoculated with P. infestans floated in metalaxyl solutions, and for inoculated potato tuber disks deposited on filter paper saturated with metalaxyl (1). Isolates were pathogenic to potatoes and tomatoes, were A2 mating type with Gpi 100/111/122 and Pep 100/100 (same as US-8), and displayed resistance to metalaxyl up to 140 mg/l.

References: (1) K. L. Deahl et al. Am. Potato J. 70:779, 1993. (2) S. B. Goodwin et al. Plant Dis. 79:1181, 1995.
A New Race of Fusarium oxysporum f. sp. melonis Causing Fusarium Wilt of Muskmelon in the Central Valley of California
Authors: Gwynne B. J. , Gordon T. R. , Davis R. M.
Published: May 2007

In 1996, cantaloupe (Cucumis melo L. cv. Durango) vines in two fields exhibited wilt, vascular discoloration, and necrotic streaks on the stems. Fusarium oxysporum Schlechtend.:Fr. was isolated from the stems of vines from both fields. One isolate from each field was compared with known isolates of F. oxysporum f. sp. melonis (Leach & Currence) W.C. Snyder & H.N. Hansen races 1 and 2 in a differential host range experiment in the greenhouse. Three-week-old seedlings were root-dip inoculated with monoconidial isolates at a concentration of 5 × 105 spores per ml. Control plants were dipped in water. In two experiments, the test isolates killed the susceptible varieties Top Mark and Magnum .45 and the race 2 resistant varieties Durango, Gold Mine, and Perlita FR. Seedlings of variety Charentais with the Fom2 gene conferring resistance to race 1 were resistant to both test isolates. It was determined that both of these isolates are associated with vegetative compatibility group (VCG) 0134 (1). This is the first report of race 1 and VCG 0134 of F. oxysporum f. sp. melonis causing Fusarium wilt of muskmelon in the Central Valley of California, and the first reported occurrence of race 1 in California since 1973 (2). Cantaloupe varieties currently grown in California are susceptible to race 1 of F. oxysporum f. sp. melonis

References: (1) D. J. Jacobson and T. R. Gordon. Phytopathology 78:668, 1988. (2) J. V. Leary and W. D. Wilbur. Phytopathology 66:15, 1976.
Leaf Curl Disease of Carica papaya from India May Be Caused by a Bipartite Geminivirus
Authors: Saxena Sangeeta , Hallan Vipin , Singh B. P. , Sane P. V.
Published: May 2007

Papaya has considerable economic importance to agriculture in India. Papaya leaf curl disease was first reported in 1939 by Thomas and Krishnaswamy (3). This disease is of moderate incidence and widely distributed in India. Recent observations of papaya fields in India indicated that there has been a continued increase in the incidence of papaya leaf curl disease (as shown by symptoms), resulting in severe economic losses. The disease is characterized by downward curling and cupping of leaves followed by vein clearing and thickening. Enations develop in the form of frills on green veins. The affected leaves become leathery and brittle and the petioles become twisted in a zig-zag manner. Diseased plants may bear a few small fruits, which are distorted in shape and tend to fall prematurely. The disease could be transmitted by the whitefly Bemisia tabaci Genn. Therefore, possible involvement of a geminivirus was suspected. Three different cloned geminiviral DNAs, Indian tomato leaf curl virus (ITLCV) (2), tomato yellow leaf curl virus from Sardinia (TYLCV Sar), and tomato golden mosaic virus (TGMV), were used as probes (with radioactive labeling) to detect the presence of geminiviral DNA from infected papaya tissue in both slot-blot and Southern blot hybridization studies with high stringency washes. These DNA probes gave strong signals with DNA isolated from infected papaya tissue whereas they did not give any signals with DNA from healthy tissue. Further, successful polymerase chain reaction (PCR)-based amplification of fragments from both DNA-A and DNA-B components with geminivirus degenerate primers (1) was accomplished only from the DNA of infected papaya plants. The PCR-amplified DNA fragments gave positive signals in Southern blot hybridization with the three geminiviral DNA probes. These results suggest that the causal agent of papaya leaf curl disease is a bipartite geminivirus that may be provisionally called papaya leaf curl virus (PLCV).

References: (1) M. R. Rojas et al. Plant Dis. 77:340, 1993. (2) K. M. Srivastava et al. J. Virol. Methods 51:297, 1995. (3) K. M. Thomas and C. S. Krishnaswamy. Curr. Sci. 8:316, 1939.
First Report of Rhizoctonia solani AG-7 on Potato in Mexico
Authors: Carling D. E. , Brainard K. A. , Virgen-Calleros G. , Olalde-Portugal V.
Published: May 2007

Among isolates of Rhizoctonia solani Kühn collected as sclerotia from potato (Solanum tuberosum L.) tubers harvested from the Toluca Valley in 1995 was one isolate (MexND) of anastomosis group 7 (AG-7). Virulence of this and other isolates of R. solani representing AG-3 (four isolates) or AG-7 (four isolates), was determined on developing potato plants (cv. Russet Burbank) in growth chamber studies at 10 and 21°C by methods used previously (1). A control treatment was inoculated with sterile disks of potato dextrose agar (PDA). Seed tubers were placed on a layer of pasturized sand-soil mix near the bottom of 6- × 25-cm black plastic tubes, then covered with 2 to 3 cm of the sand-soil mix. Seed tubers used in virulence tests carried no R. solani as they had been surface disinfested by immersing for 2 min in a 1.85% solution of formaldehyde. Inoculum, in the form of one 7-mm agar disk cut from the growing edge of appropriate colonies growing on PDA, was placed 2 to 3 cm above the seed and covered with 7 to 10 cm of sand-soil mix (1). Each treatment had five replications. Plants were harvested after control plants had emerged, 29 days at 21°C and 36 days at 10°C, and damage to roots and shoots was assessed according to Carling and Leiner (1). All four isolates of AG-3, one from the U.S. and three from Mexico, caused major damage to roots and shoots at both temperatures. The two isolates of AG-7 from the U.S. caused superficial discoloration to shoots at both temperatures but the two isolates of AG-7 from Japan caused no damage to shoots. None of the four isolates of AG-7 damaged roots at either temperature. MexND caused no damage to roots or shoots at 21°C but produced lesions (< 1 mm in diameter) on roots and shoots at 10°C. Thus, MexND caused less damage to potato than AG-3, more damage than other isolates of AG-7, and appears more aggressive at lower temperatures. This is the first reported occurrence of R. solani AG-7 in Mexico and its first reported recovery from a potato tuber-borne sclerotium.

Reference: (1) D. E. Carling and R. H. Leiner. Phytopathology 80:930, 1990.
First Report of Anthracnose of Lentil Incited by Colletotrichum truncatum in Bulgaria
Authors: Kaiser W. J. , Mihov M. , Muehlbauer F. J. , Hannan R. M.
Published: May 2007

In June 1992 and 1995, anthracnose of lentil (Lens culinaris Medik.) incited by Colletotrichum truncatum (Schwein.) Andrus & W. D. Moore was widespread in field trials at the Institute for Wheat and Sunflower ‘Dobroudja’ near General Toshevo in northeastern Bulgaria. Lesions on the leaves, stems, and pods were usually white to grayish on younger plants, often turning brown as plants matured. Severe infection usually resulted in dieback and/or death of plants. Acervuli containing spores and dark setae were observed within lesions, and conidia from the acervuli produced pure cultures of C. truncatum. Conidia were hyaline, onecelled, falcate to nearly straight with a prominent clear area in the center of highly granular cytoplasm, and measured 17.6 to 19.8 × 4.4 μm. C. truncatum was seed-borne in naturally infected lentil cv. Tadjikskaya 95 at low frequencies (<2%). Koch's postulates were fulfilled by inoculating the foliage of lentil cvs. Brewer and Pardina and reisolating the fungus from stem and petiole lesions. In pathogenicity tests, three isolates of C. truncatum from the foliage and seeds of lentil caused severe symptoms on inoculated lentil cvs. Brewer and Pardina, similar to those observed on diseased lentils in Bulgaria. The fungus also caused moderate symptoms on inoculated faba bean (Vicia faba L.) and pea (Pisum sativum L.), and light symptoms on inoculated chickpea (Cicer arietinum L.). In 1995, 258 USDA Plant Introduction (PI) accessions from the USDA lentil core collection were screened in replicated trials in northeastern Bulgaria and disease symptoms were observed in >90% of the lines. Anthracnose severity ranged from light to severe. A few accessions appeared to have acceptable levels of resistance to the disease. These included accessions from Iran (PI 431714 and 431717) and Spain (PI 533693). Also that year, C. truncatum was isolated from stem lesions of naturally infected bitter vetch (Vicia ervilia (L.) Willd.) at the Institute for Wheat and Sunflower ‘Dobroudja’. The disease in Bulgaria appears to be identical to one causing anthracnose of lentil in Canada (1) and the United States (2). This is the first report of C. truncatum causing anthracnose of lentil in Bulgaria.

References: (1) R. A. A. Morrall. Plant Dis. 72:994, 1988. (2) J. R. Venette et al. Plant Dis. 78:1216, 1994.