bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Wounds as a Factor to Infection of Cabbage by Ascospores of Sclerotinia sclerotiorum
Authors: Hudyncia J. , Shew H. D. , Cody B. R. , Cubeta M. A.
Published: May 2007

A semi-selective medium was used to examine the aerobiology of ascospores of Sclerotinia sclerotiorum in five commercial cabbage fields in eastern North Carolina. Ascospores were present in all five fields from 26 September to 30 November. However, numbers of ascospores varied greatly depending on location, sampling date, and time. In general, peak ascospore deposition occurred between 11:00 A.M. and 1:00 P.M., with the number of colonies recovered ranging from 3 to 55/dish (9 cm in diameter). Peak ascospore numbers at all locations were found from mid- to late October, but a second, smaller peak was also evident at each location in late November. Information obtained was employed to evaluate the role of wounding in infection of cabbage by ascospores of S. sclerotiorum in controlled environmental chambers. A method for production and release of ascospores of S. sclerotiorum was employed in controlled-environment chambers for the inoculation of cabbage plants with one of three representative foliar wounds: a bruise, a cut, or a non-lethal freeze. Wounding treatments were applied to 7-week-old cabbage plants, misting was added to maintain continuous leaf wetness, and ascospores were released from apothecia twice daily for four consecutive days. Spore trapping with a semi-selective medium indicated that inoculum was evenly distributed within the chambers and deposition was similar to levels recorded in the field. At 31 days after inoculation, disease incidence ranged from 0% on the control to 96% on the freeze treatments. Freeze-treated plants showed the highest disease severity throughout the entire incubation period. Mean area under the disease progress curve of severity values were 0, 0.2, 34 and 60 for the control, cut, bruise, and freeze treatments, respectively. Results indicate that freeze and bruise injuries are important factors associated with infection of cabbage by S. sclerotiorum.
Identification and Etiology of Visible Quiescent Infections of Monilinia fructicola and Botrytis cinerea in Sweet Cherry Fruit
Authors: Adaskaveg J. E. , Förster H. , Thompson D. F.
Published: May 2007

Visible quiescent infections were detected as small (<1 mm) necrotic flecks on green cv. Bing cherry fruit and as reddish halos surrounding tannish spots (1 to 2 mm) on immature, yellow-pink cv. Rainier cherry fruit in commercial orchards in California. Monilinia fructicola or Botrytis cinerea, the fungal pathogens causing brown rot and gray mold of cherry fruit, respectively, were isolated from most of the viable infections. M. fructicola was isolated more frequently from quiescent infections than B. cinerea in two years of the study, whereas similar isolation frequencies for both fungi were obtained in the other two years of sampling from one commercial Rainier cherry orchard. Using immature-pink Bing fruit that were inoculated in the laboratory, significantly more visible quiescent infections than active decay were reproduced in 6-, 9-, or 12-h wetness-period treatments after inoculation as compared to 18- or 24-h wetness periods where more active decay developed. Non-visible quiescent infections of M. fructicola or B. cinerea of immature Bing and Rainier fruit collected 2 weeks before harvest were identified on surface-sterilized, paraquat-treated fruit. In both years of the study, significantly more brown rot and gray mold occurred on the surface-sterilized, paraquat-treated fruit than on the non-treated or surface-sterilized fruit, indicating the presence of non-visible quiescent infections by these fungi in cherry fruit. Thus, for the first time, we demonstrated the presence of visible quiescent infections caused by M. fructicola and B. cinerea and we confirmed the occurrence of non-visible quiescent infections in sweet cherry fruit in California.
First Report of Arceuthobium hondurense on Pinus tecunumannii
Authors: Mathiasen R. , Beatty J. , Melgar J.
Published: May 2007

Honduran dwarf mistletoe (Arceuthobium hondurense Hawksw. & Wiens) is a rare dwarf mistletoe found only in Honduras (1,2). Thus far, it has been reported to parasitize only Pinus oocarpa Schiede (2). In October 1999, we observed infection by A. hondurense on P. tecunumannii (Schw.) Eguiluz et Perry along the trail to the summit of Montana del Celaque (elevation 1,750 to 1,800 m) on the east side of Celaque National Park, ≈5 km west of Gracias (Department Lempira), Honduras. Infected pines had witches′ brooms, and mistletoe shoot production was common on infected branches. This is the first report of A. hondurense on P. tecunumannii. Specimens of A. hondurense from P. tecunumannii were collected and have been deposited at the Herbario, Escuela Nacional de Ciencias Forestales, Siguatepeque, Honduras, and at the Deaver Herbarium, Northern Arizona University, Flagstaff.

References: (1) F. G. Hawksworth and D. Wiens. 1996. Dwarf Mistletoes: Biology, Pathology, and Systematics. U.S. Dep. Agric. Agric. Handb. 709. (2) R. Mathiasen et al. Phytologia 36:211, 1998.
Natural Outbreak of a Bacterial Fruit Rot of Cantaloupe in Georgia Caused by Acidovorax avenae subsp. citrulli
Authors: Walcott R. R. , Langston D. B. , Sanders F. H. , Gitaitis R. D. , Flanders J. T.
Published: May 2007

In April and July 1999, cantaloupe plants (Cucumis melo) from commercial greenhouses and fields in Grady, Colquitt, Mitchell, and Tift counties, GA, exhibited severe foliar necrosis and a fruit rot. Foliar symptoms were V-shaped, necrotic lesions occurring at the margin of the leaf and extending inward toward the midrib. Symptoms on the fruit surface were observed after net development and occurred randomly as round, necrotic, sunken spots or cracks a few millimeters in diameter. A soft rot originating from lesions on the surface of the fruit expanded into the flesh. Approximately 5% of the fruits were affected. Bacteria recovered from cantaloupe fruit and leaf tissues produced nonfluorescent, smooth, off-white colonies on King's medium B. Characteristic of Acidovorax avenae subsp. citrulli, the bacteria produced pits in carboxymethyl cellulose media (WFB 44), and reduced Tween 80 to give a visible precipitate on WFB 68 media (1). Based on fatty acid analysis, all strains were identified as A. avenae subsp. citrulli by Microbial Identification System software, version 3.6 (MIDI, Newark, DE), and similarity indices of 0.06, 0.79, 0.21, and 0.43 were recorded for strains recovered form Grady, Tift, Colquitt, and Mitchell counties, respectively. Using specific oligonucleotide primers (WFB 1/2) (2), PCR conducted on DNA from each strain yielded a 390-bp DNA fragment, confirming similarity to A. avenae subsp. citrulli. Indirect enzyme-linked immunosorbent assay with genus-specific antibodies also verified that the bacteria were Acidovorax spp. Pathogenicity of the A. avenae subsp. citrulli strains was confirmed by inoculating and observing symptom development on 2-week-old watermelon seedlings. Although all strains were identified and confirmed as A. avenae subsp. citrulli, restriction fragment length polymorphism data indicated that the Tift County strain was distinguishable from the others, suggesting that inoculum for these outbreaks may have originated from at least two different sources.

References: (1) R. D. Gitaitis. 1993. Development of a seedborne assay for watermelon fruit botch. Pages 9–18 in: Proc. 1st Int. Seed Testing Assoc. Plant Dis. Commit., Ottawa, Canada. (2) R. R. Walcott and R. D. Gitaitis. (Abstr.) Phytopathology 88(suppl.):S92, 1998.
Cost of Fungicides Used to Manage Potato Late Blight in the Columbia Basin: 1996 to 1998
Authors: Johnson Dennis A. , Cummings Thomas F. , Hamm Philip B.
Published: May 2007

The cost of managing potato late blight with fungicides in the Columbia Basin of Washington and Oregon in 1996 to 1998 was documented and compared with the cost of managing the epidemic in 1995. Mean number of fungicide applications on late-season potatoes from 1996 to 1998 ranged from 5.3 to 8.8 in the north Columbia Basin of Washington and 8.5 to 12.3 in the southern basin of Washington and Oregon. Mean cost per hectare of fungicides and application on late-season potatoes in 1998 was $316 per hectare ($128 per acre) in Washington's north basin and $472 per hectare ($191 per acre) in Washington's south basin. Even though the price of most fungicides had increased since 1995, total cost of control per hectare over the season was less during 1996 to 1998 than in 1995 because of altered management practices. These included fewer fungicide applications, a shift toward lower cost fungicides, substitution of aerial application by chemigation, and a reduction in the number of fields chemically desiccated before harvest. Total cost of managing late blight and tuber rot loss was $22.3 million in 1998, whereas it was $30 million in 1995. The 1998 cost included $19.8 million for fungicide applications and materials, $1.1 million for canopy desiccation, and $1.4 million loss due to tuber rot in storage.
Mycoflora of Stone Fruit Mummies in California Orchards
Authors: Hong C. X. , Michailides T. J. , Holtz B. A.
Published: May 2007

Stone fruit mummies infected by Monilinia fructicola were periodically collected in winter from trees and from the ground in eight orchards in 1995-96 and from five orchards in 1996-97. Mycoflora were determined by spreading mummy washings and plating inner tissues onto petri dishes containing acidified potato dextrose agar, then counting colonies of individual fungi after incubation at 23°C for 4 days. Twenty genera, representing 29 fungal species, were isolated from both mummy washings and inner tissues. Aspergillus japonicus, A. terreus, and species of Harknesia, Paecilomyces, and Trichoderma are the first recorded from species of Prunus in the United States, and Aureobasidium pullulans and Epicoccum purpurascens are the first reported for California. The principal mycoflora recovered from mummy washings were species of non-filamentous yeasts (32.1%), Penicillium (28.8%), Cladosporium (11.4%), and Mucor (10.8%). Major mycoflora of mummy inner tissues were species of Penicillium (23.7%), Mucor (19.6%), Cladosporium (17.3%), and Rhizopus (11.1%). The relative recoveries of individual fungi from mummy inner tissues differed with location, Prunus species, and sampling position (tree or ground), and changed as the season progressed. The relative recovery of M. fructicola from mummy inner tissues was negatively correlated with Botrytis (R = -0.53, P = 0.0052), Penicillium (R = -0.58, P = 0.0681), and Rhizopus (R = -0.50, P = 0.0696). These results could help obtain naturally occurring antagonists and maximize their use in biocontrol systems aimed at reducing primary inoculum for blossom blight of stone fruits in California orchards.
Identification and Phylogenetic Analysis of a New Phytoplasma from Diseased Chayote in Brazil
Authors: Montano H. G. , Davis R. E. , Dally E. L. , Pimentel J. P. , Brioso P. S. T.
Published: May 2007

Chayote (Sechium edule) (Cucurbitaceae), also known as vegetable pear, mirliton, or mango squash, is a commercially important vegetable crop in Brazil, where it is affected by chayote witches'-broom disease. Affected plants exhibit witches'-broom growths and other symptoms characteristic of plant diseases caused by phytoplasmas. Since previous electron microscopic studies revealed the association of a phytoplasma with chayote witches'-broom, the present work was aimed at detecting and classifying the phytoplasma that may be the causal agent of the disease. Strains of a phytoplasma belonging to group 16SrIII (X-disease phytoplasma group) were discovered in chayote affected by witches'-broom disease and in diseased plants of Momordica charantia that were growing as weeds in fields of chayote in Brazil. On the basis of results from restriction fragment length polymorphism and nucleotide sequence analyses of 16S rDNA, the phytoplasma was classified in a new subgroup, designated subgroup III-J. This classification was supported by a phylogenetic tree constructed by the Neighbor-Joining method.
Incidence of Tomato spotted wilt virus (Bunyaviridae) and Tobacco Thrips in Virginia-Type Peanuts in North Carolina
Authors: Garcia L. E. , Brandenburg R. L. , Bailey J. E.
Published: May 2007

Virginia-type peanut (Arachis hypogaea) cultivars were monitored for incidence of Tomato spotted wilt virus (TSWV) and abundance of Frankliniella fusca, the tobacco thrips, in North Carolina during 1995 and 1996. A preliminary evaluation of 225 peanut genotypes for TSWV-resistant or -tolerant genotypes was conducted in 1995. The incidence of TSWV in cultivar NC-9 was twice that of cultivar NC-V11. In 1996, field trials designed to evaluate TSWV susceptibility were conducted with three widely grown commercial peanut cultivars in North Carolina. They were NC-9, NC-V11, and NC-12C, a newly released cultivar. A randomized complete block design was utilized at three locations. Disease incidence was evaluated weekly from 2 weeks postplanting until 2 weeks prior to harvest. Mechanical inoculation of the three cultivars resulted in no difference in relative leaf virus titer as determined from optical density readings following DAS-ELISA for 4 successive weeks beginning at 13 days postinoculation. NC-9 ranked highest in incidence of disease (7%), followed by NC-12C (6%) and NC-V11 (5%). Thrips counts were greatest on NC-V11, followed by NC-9 and NC-12C. Disease incidence overall was 5.96%, but ranged from 3.08 to 11.15% among the three sites. Yield was affected by the temporal occurrence of symptoms beginning at the fifth week postplanting. Greatest yield losses occurred in those plants with the earliest visible foliar symptoms.
First Report of Botrytis Blight, Caused by Botrytis cinerea, on Hibiscus in South Africa
Authors: Swart L. , Langenhoven P.
Published: May 2007

Roselle (Hibiscus sabdariffa L.) is an annual herb grown in China, Thailand, Mexico, and Africa. Different plant parts are used for cold and hot beverages, food ingredients, edible oil, and medicinal properties. In May 1999, a disease was observed in a commercial field of 6-month-old H. sabdariffa plants in Eshowe, KwaZulu-Natal, South Africa. Stems of diseased plants had brown, sunken lesions covered with green-gray spore masses. Infected stems collapsed. Lesions initiated on stems expanded rapidly under cool, humid conditions. In some cases, lesions developed on the flower stalk and expanded to the calyx, causing death of the calyx. Leaves had no lesions or sporulation, but as stem blight progressed, leaves wilted and fell off. Botrytis cinerea Pers.:Fr. (1) was consistently isolated from affected stem and flower stalk tissues. The pathogen produced profuse conidia and mycelia on the surface of dead and infected stems and calyxes, which resulted in a moldy gray appearance. The average size of conidia produced on naturally infected stems ranged from 5.5 to 8.0 × 6.0 to 13.0 μm (average 6.5 × 9.2 μm). On potato dextrose agar (1-month-old culture), conidia ranged from 5.0 to 9.5 × 6.5 to 12.5 μm (average 7.3 × 8.7 μm) based on 50 spore measurements. Microsclerotia were round or irregular and ranged from 1.2 to 3.0 × 1.0 to 2.5 mm (average 2.1 × 2.0 mm). Koch's postulates were confirmed by spraying potted, 6-month-old H. sabdariffa plants with a spore suspension (1 × 105 conidia per ml). Inoculated plants were enclosed in transparent plastic bags for 7 days at 15 and 20°C (night and day) in a glasshouse. Typical symptoms developed on stems and calyxes within 7 days after inoculation. B. cinerea was reisolated from affected tissues. Botrytis gray mold blight has been recorded on H. rosa-sinensis L. and Hibiscus sp. in Florida (2), but this is the first report of Botrytis blight on Hibiscus spp. in South Africa. Because the disease can result in plant death, Botrytis blight may have a significant impact on the establishment and yield of this crop in the field, especially under cool, wet growing conditions.

References: (1) M. B. Ellis. 1971. Dematiaceous Hyphomycetes. CAB, Kew, Surrey, England. (2) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN.
First Report of Bacterial Spot of Lettuce Caused by Xanthomonas campestris pv. vitians in Turkey
Authors: Sahin F.
Published: May 2007

During spring 1999, lettuce (Lactuca sativa) plants grown at Oltu in the eastern Anatolia region of Turkey were observed with numerous lesions typical of bacterial leaf spot. Lesions on leaves were irregular, small, pale green to black, water-soaked, and 2 to 5 mm in diameter. Coalescing lesions sometimes caused defoliation of older leaves. Isolations made from diseased leaves on yeast dextrose carbonate agar yielded nearly pure cultures of a yellow pigmented bacterium typical of a xanthomonad. Five bacterial strains were purified and used for further tests. The strains reacted positively with a Xanthomonas-specific monoclonal antibody, X1, in indirect enzyme-linked immunosorbent assays (1). Fatty acid analysis identified the strains as X. campestris pv. vitians (proposed name X. axonopodis pv. vitians), with greatest similarity indices of 29 to 71% (2). Pathogenicity of strains was confirmed on 5-week-old lettuce plants (cv. Darkland) sprayed with bacterial suspensions containing 108 CFU/ml of sterile water. Inoculated and sterile water-sprayed control plants were covered with polyethylene bags for 48 h at 25°C, after which bags were removed and plants were maintained in the greenhouse. Water-soaked spots similar to those in the field were observed on inoculated plants within 5 to 7 days. No symptoms developed on control plants. The bacterium was reisolated from inoculated plants and identified as X. campestris pv. vitians. This is the first report of bacterial leaf spot of lettuce in Turkey.

References: (1) A. M. Alvarez et al. Phytopathology 84:1449, 1994. (2) Vauterin et al. Int. J. Syst. Bact. 45:472, 1995.
Stem Blight of Eustoma grandiflorum Caused by Sclerotium rolfsii
Authors: McGovern R. J. , Bouzar H. , Harbaugh B. K.
Published: May 2007

During a 4-week period in May through June 1996, 15% of 50 mature lisianthus (Eustoma grandiflorum) ‘Maurine Blue’ and ‘Maurine White’ plants exhibited stem blight in a landscape planting in west-central Florida. Initial disease symptoms included stem necrosis at the soil line, and yellowing and tan discoloration of leaves. As blighting of the stem progressed, infected plants wilted and died. Symptomatic stem sections from three plants were surface-disinfested in 0.5% NaOCl and placed on acidified 25% potato dextrose agar (APDA). Sclerotium rolfsii Sacc. was isolated from all three diseased stems. Pathogenicity of each of three S. rolfsii isolates was confirmed using two lisianthus ‘Flamenco Blue’ plants grown in 10.2-cm-diameter plastic pots containing a peat-based medium. Sclerotia produced on APDA were sprinkled on the soil surface around each plant base; 50, 100, and 5 sclerotia from isolates A, B, and C, respectively, were used (isolate C grew more slowly and produced fewer sclerotia than either A or B). Two noninoculated lisianthus served as controls. Plants were maintained in a greenhouse at minimum and maximum temperatures of ≈24 and 35°C, respectively. Plants inoculated with sclerotia from isolates A and B developed blight symptoms within 6 days. One of two plants inoculated with isolate C developed blight symptoms within 17 days, and the other remained symptomless, as did the control plants. Infection by S. rolfsii was confirmed by reisolation from symptomatic tissue. This is the first report of stem blight of lisianthus caused by S. rolfsii.
Characterization of a Virus Infecting Lisianthus
Authors: Chen C. C. , Chen Y. K. , Hsu H. T.
Published: May 2007

A virus was isolated in Taiwan from imported lisianthus (Eustoma russellianum) plants bearing viruslike symptoms and was biologically, physically, and serologically characterized. Purified virions are isometric and measure 32 to 33 nm in diameter. The virus from Taiwan is morphologically similar to and serologically related to Lisianthus necrosis necrovirus (LNV) reported in Japan. This lisianthus virus does not have the same host range that was reported for LNV from Japan, but inoculation studies show that it is a strain of LNV.
Occurrence, Distribution, and Relative Incidence of Five Viruses Infecting Cucurbits in the State of São Paulo, Brazil
Authors: Yuki V. A. , Rezende J. A. M. , Kitajima E. W. , Barroso P. A. V. , Kuniyuki H. , Groppo G. A. , Pavan M. A.
Published: May 2007

Cucurbits species grown in 38 of 40 agricultural regions in the state of São Paulo, Brazil, were surveyed for the relative incidence of Cucumber mosaic virus (CMV), Papaya ringspot virus-type W (PRSV-W), Watermelon mosaic virus-2 (WMV-2), Zucchini lethal chlorosis virus(ZLCV), and Zucchini yellow mosaic virus (ZYMV) during May 1997 and June 1999. Samples from 621 plants, representing eight cultivated species, six wild species, and one commercial hybrid (Cucurbita moschata × C. maxima), were analyzed by plate trapped antigen enzyme-linked immunosorbent assay (PTA-ELISA). PRSV-W and ZYMV were the most frequently found viruses, accounting for 49.1 and 24.8%, respectively, of 605 samples tested. ZLCV, CMV, and WMV-2 were detected in 7.8, 6.0, and 4.5% of 612, 497, and 423 samples tested, respectively. Double infection was found in 97 samples, and triple infection was found in 10 samples. Quadruple infection was detected in one C. pepo sample. Plants that were symptomatic but negative by PTA-ELISA might be due to abiotic agents, infection by virus for which antiserum was not available, such as Squash mosaic virus, or infection with an as yet uncharacterized virus.
Effects of Plant Spacing and Cultivar on Incidence of Botrytis Fruit Rot in Annual Strawberry
Authors: Legard D. E. , Xiao C. L. , Mertely J. C. , Chandler C. K.
Published: May 2007

The effects of within-row plant spacing and cultivar on the incidence of Botrytis fruit rot (Botrytis cinerea) and marketable yield of annual strawberry were evaluated during the 1997-98 and 1998-99 seasons. Three cultivars (Camarosa, Rosa Linda, and Sweet Charlie) and four plant spacings (23, 30, 38, and 46 cm) were evaluated. Marketable yield and the incidence of Botrytis fruit rot were determined twice weekly. Cultivar and spacing effects were analyzed for three periods each season (early, late, and whole season). In 1997-98, spacing effects were observed on weekly incidence of Botrytis rot for the late period (P = 0.0925) and on cumulative incidence for the whole season period (P = 0.0795). Further analysis of the late and whole season periods revealed a spacing effect for Camarosa (P = 0.0102). Spacing also had a dramatic effect on cumulative and weekly Botrytis incidence for the late and whole season periods during the 1998-99 season (P ≤ 0.0014), when narrower spacings had higher incidence of Botrytis than wider spacings. Marketable yields were higher at narrower spacings during the early period for both seasons. Whole season marketable yields were also higher at the narrower spacings despite higher incidence of Botrytis. There were significant differences in susceptibility among cultivars.
First Report of Verticillium Wilt of Sugar Beet, Caused by Verticillium dahliae, in Greece
Authors: Karadimos D. A. , Karaoglanidis G. S. , Klonari K.
Published: May 2007

Wilting sugar beet plants (Beta vulgaris L.) were observed in fields in the Larissa area of central Greece during the summers of 1997 and 1998. Diseased plants, showing general yellowing and epinasty, were sporadically distributed in the fields. As symptoms progressed, the outer leaves wilted and became desiccated. Inner leaves showed marginal and interveinal yellowing. These areas later turned brown and became necrotic. Longitudinal sections of the roots of diseased plants displayed browning of vascular tissues. Fungal isolates obtained from discolored vascular tissues on potato dextrose agar (PDA) medium were identified as Verticillium dahliae based on morphological features (1). Cultures grew moderately fast on PDA at 23°C. Mycelia were hyaline and white to cream colored, becoming black with formation of microsclerotia. Conidiophores were hyaline and verticillately branched, with three to four phialides at each node. Conidia borne on phialides were ellipsoidal to short and cylindrical and mainly one-celled (2.5 to 8 × 1.4 to 3.2 µm). Microsclerotia began to form in 6- to 7-day-old cultures and were dark brown to black and varied in shape and size (25 × 50 to 100 µm diameter). Pathogenicity tests were carried out using the root-dip technique. Two-week-old seedlings (cv. Rizor) were inoculated by dipping roots in an aqueous suspension of 108 conidia per ml for 1 min. Inocula were obtained from 2-week-old cultures grown on PDA at 21°C by adding sterile water to the petri dish, gently shaking to detach conidia from the conidiophores, and filtering through a doublelayer of sterile cheesecloth. Roots of control plants were dipped in distilled water, and seedlings were transplanted to pots and placed in a growth chamber at 23°C with a 12-h photoperiod. Inoculated plants exhibited wilted leaves with interveinal yellowing ≈30 days after inoculation; symptoms were not observed on control plants. V. dahliae was reisolated from artificially inoculated plants. Measurements of yield parameters in healthy and diseased plants showed that the sugar content of diseased roots was significantly reduced, whereas root weight was not affected. Such results agree with a previous report on the effects of the disease on yield parameters (2). However, the disease is of minor importance in Greece mainly because of the low number of infected plants in the fields. This is the first report of Verticillium wilt of sugar beet in Greece.

References: (1) Anonymous. 1971. Verticillium dahliae. No 256: Descriptions of Plant Pathogenic Fungi and Bacteria. Common w. Mycol. Inst., Kew, England. (2) J. O. Gaskill and W. A. Krentzer. Phytopathology 30:769, 1940.
First Report of Cucurbit yellow stunting disorder virus in Morocco
Authors: Desbiez C. , Lecoq H. , Aboulama S. , Peterschmitt M.
Published: May 2007

In October, 1999, severe yellowing symptoms were observed in a melon (Cucumis melo L.) crop grown under plastic tunnels in the region of Agadir, Morocco. Large populations of whiteflies (Bemisia tabaci) were noticed during the early stages of the crop. At harvest, leaf samples were collected from two symptomatic plants and one symptomless plant. A mature yellow leaf was assayed from each symptomatic plant and for one of these two plants a younger leaf exhibiting only yellow spots. Cucurbit aphid-borne yellows virus, which causes similar symptoms in melons, was not detected by double-antibody sandwich enzyme-linked immunosorbent assay tests. Total RNA was extracted from fresh leaf tissues and submitted to reverse transcription and polymerase chain reaction with primers specific to two whitefly-transmissible viruses: Beet pseudo-yellows virus (BPYV) and Cucurbit yellow stunting disorder virus (CYSDV) (2). No amplification was obtained with BPYV-specific primers. In contrast, an expected 465-bp product was amplified in all samples from symptomatic plants with CYSDV-specific primers. No amplification was detected in samples from the symptomless plant nor from healthy control plants. B. tabaci-transmitted CYSDV has been reported in the Middle East, southwestern Europe, and North America (1,4). This is the first report of CYSDV in Morocco, and it follows the first report of another B. tabaci-transmitted virus, Tomato yellow leaf curl virus, in tomato (3), suggesting an important change in the viral pathosystem affecting vegetable crops in Morocco.

References: (1) Kao et al. Plant Dis. 84:101, 2000. (2) Livieratos et al. Plant Pathol. 47:362, 1998. (3) Peterschmitt et al. Plant Dis. 83:1074, 1999. (4) Wisler et al. Plant Dis. 82:270, 1998.
Pear Scab: Components of Potential Ascospore Dose and Validation of an Ascospore Maturity Model
Authors: Spotts Robert A. , Cervantes Louis A. , Niederholzer Franz J. A.
Published: May 2007

Variables necessary to calculate potential ascospore dose (PAD) for Venturia pirina, the causal agent of pear scab, were measured: area of individual leaves averaged 20.0 cm2, number of lesions per infected leaf ranged from 1.8 to 2.2, 13.5 to 41.7% of lesions were fertile (contained pseudothecia), number of pseudothecia per fertile lesion ranged from 15.2 to 24.4, and number of asci per pseudothecium averaged 131.5. The proportions of orchard floor covered with leaves (leaf litter density) were 0.34 and 0.67 for mowed and nonmowed orchards, respectively. Incidence of infected leaves ranged from 0.1 to 32.3%. Calculated PAD ranged from 1,114 to 708,320 ascospores per m2 in a commercial and an unsprayed orchard, respectively. For validation of a previously published model relating ascospore maturity to degree-days with a 0°C base, a linear regression equation was developed using 11 data sets collected between 1981 and 1998. The slope of the line was not different (P = 0.951) from that of the original model.
Development and Evaluation of a Standard Method for Screening for Resistance to Radopholus similis in Bananas
Authors: Marin Douglas H. , Barker Kenneth R. , Kaplan David T. , Sutton Turner B. , Opperman Charles H.
Published: May 2007

The description and evaluation of a standard assay method for screening for resistance of bananas to the burrowing nematode (Radopholus similis) under greenhouse conditions is presented. Seven banana genotypes, ranging from susceptible to resistant, were used to evaluate the method. Banana plants from tissue culture, grown in 0.4-liter Styrofoam cups containing sterilized sand as substrate, were maintained in the greenhouse for 4 weeks before inoculation. Two hundred burrowing nematodes, reared in monoxenic carrot-disk culture, were used as inoculum for each container. Plants were kept in the greenhouse for an additional 8 weeks at about 27°C and 80% relative humidity after inoculation. Burrowing nematodes reproduced well in the susceptible cultivars False Horn, Grande Naine, Valery, and Lacatan, whereas the reproductive fitness was very low in the resistant cultivars Pisang Jari Buaya and Yangambi. An intermediate reaction between these two groups was observed with Pisang mas. A similar trend was obtained in a follow-up field test, which indicated that the method is accurate and reliable. Assessments of total-root necrosis associated with this pathogen were also comparable between greenhouse and field conditions. However, nematode effects on the roots were more severe in the greenhouse test than in the field. In spite of low nematode reproductive fitness, root necrosis was relatively high in the two resistant cultivars tested in the greenhouse trial.
Differential Seed Infection of Wheat Cultivars by Stagonospora nodorum
Authors: Shah Denis A. , Bergstrom Gary C. , Sorrells Mark E.
Published: May 2007

Seed of soft white winter wheat collected from New York regional cultivar trials in 1995 and 1996 were assayed on an agar medium selective for Stagonospora nodorum. Incidence of seed infection varied with production environment. Relative incidence of seed infection differed significantly among cultivars and was consistent across environments. The flag leaves and ears of 12 cultivars were inoculated quantitatively at flowering in a glasshouse. Cultivars did not differ significantly in disease on the flag leaves. Incidence of seed infection for all cultivars was above 60%, but was significantly lower in Delaware and Houser than in other cultivars. Results confirm that wheat cultivars differ in their relative susceptibility to seed infection by S. nodorum. Resistance in wheat to seed infection by S. nodorum may be a useful mechanism for reducing initial inoculum in areas where infected seed is considered the primary inoculum source for Stagonospora nodorum blotch.
Preplanting Bahia Grass or Wheat Compared for ControllingMesocriconema xenoplaxand Short Life in a Young Peach Orchard
Authors: Nyczepir A. P. , Bertrand P. F.
Published: May 2007

The effects of four preplant ground cover systems as alternatives to chemical control of Mesocriconema xenoplax were investigated from 1991 to 1998. Ground cover establishment was initiated in 1991 in an orchard known to be infested with M. xenoplax and having a history of peach tree short life (PTSL). Ground cover systems included (i) Pensacola bahia grass, (ii) Tifton 9 bahia grass, (iii) winter wheat (Triticum aestivum ‘Stacy’), and (iv) naturally occurring weeds that were maintained over the entire orchard floor. Ground cover evaluation was initiated in 1994, when herbicide was applied to the ground cover plots and half the weed plots were fumigated with methyl bromide. Peach trees were planted into all plots in 1995. Fumigation effect on M. xenoplax population density collapsed 25 months after application. Young peach trees grew faster for the first 13 months in killed Pensacola bahia grass sod and fumigated soil, intermediate in Tifton 9 bahia grass and wheat plots, and slowest in unfumigated weed plots. By the end of the experiment, tree growth was greatest in Pensacola bahia grass killed sod and least in the unfumigated weed plots. Preplant wheat was as effective as fallow for 3 years plus a preplant methyl bromide fumigation in increasing tree survival from PTSL.
Particle Lengths of Whitefly-Transmitted Criniviruses
Authors: Liu H.-Y. , Wisler G. C. , Duffus J. E.
Published: May 2007

An improved method for particle length measurement was used for six members of the genus Crinivirus. Particle measurements were conducted with a CCD-72S solid state camera, which was interfaced with a Zeiss EM 109 electron microscope, and analyzed using the analysis 2.1 Image Analysis Software. In comparisons of specimen preparation methods, the leaf dip method is more representative and reproducible than the antibody capture method or preparation from purified virions. Particle length (nm) ranges of whitefly-transmitted criniviruses are: Abutilon yellows virus (AYV), 800 to 850; Cucurbit yellow stunting disorder virus (CYSDV), 750 to 800; Lettuce chlorosis virus (LCV), 800 to 850; Lettuce infectious yellows virus (LIYV), 700 to 750; Tomato chlorosis virus (ToCV), 800 to 850; and Tomato infectious chlorosis virus (TICV), 850 to 900.
First Report of Rhizoctonia solani AG-3 on Potato in Catalonia (NE Spain)
Authors: El Bakali M. A. , Martín M. P. , García F. F. , Montón R. C. , Moret B. A. , Nadal P. M.
Published: May 2007

During the last 3 years, potatoes (Solanum tuberosum L.) with symptoms typical of Rhizoctonia canker and black scurf have been found in Catalonia; from 21,546 samples submitted to the official diagnostic laboratory (Laboratori de Sanitat Vegetal, DARP, Generalitat de Catalunya), 20% were infected with R. solani. Also, basidia and basidiospores of Thanatephorus cucumeris (A.B. Frank) Donk, the teleomorph of R. solani, have been observed frequently on stems near the soil surface. Previous work (1) has reported R. solani in the same geographic area, but anastomosis groups (AG) were not identified. Isolates (103) were collected from damaged roots, mature or progeny tubers, soil, debris, and weeds (roots and stem of Oxalis latifolia, Diplotaxis eurocoides, Solanum nigrum, Sorghum halepense, and Chenopodium album) in fields where potatoes were cultivated. All isolates were multinucleate, variable in number of nuclei (mean = 12, range = 7 to 19), and with morphological features typical of R. solani (3). Following the procedure of Parmeter et al. (2), all isolates (84) were identified as R. solani AG-3. Thirty-two isolates were evaluated for pathogenicity on potato plants at 20 to 25°C in the greenhouse. Germinated tubers (sprout length 3 cm) free of Rhizoctonia were placed in pea-sand mix (3:1, vol/vol; Compo Sana Universal, Barcelona, Spain) at 5-cm depth and inoculated by placing a 5-mm-diameter plug cut from 1-week-old cultures of each isolate adjacent to the sprouts. Potatoes were harvested 20 days after planting, and both emerged and nonemerged sprouts were examined for lesions and rated using a 0 to 4 scale. The AG-3 isolates caused major damage to roots and shoots (average disease rating 3.4). R. solani isolates were recovered from diseased plants and identified as AG-3. Preliminary field studies in Catalonia (Baix Llobregat and Maresme, unpublished) indicate that disease severity is not dependent on cultivar or related to yield reduction (10 to 65%), but is related to soil and seed contamination with sclerotia and mycelium. This is the first reported occurrence of R. solani AG-3 on potato in Catalonia.

References: (1) Cebolla et al. Actas del III Congreso de la SECH, 1989. (2) Parmeter et al. Phytopathology 59:1270, 1969. (3) Sneh et al. Identification of Rhitzoctonia species. American Phytopathological Society, St. Paul, MN, 1991.
Fusarium nygamai Associated with Fusarium Foot Rot of Rice in Sardinia
Authors: Balmas V. , Corda P. , Marcello A. , Bottalico A.
Published: May 2007

Fusarium nygamai Burgess & Trimboli was first described in 1986 in Australia (1) and subsequently reported in Africa, China, Malaysia, Thailand, Puerto Rico, and the United States. F. nygamai has been reported on sorghum, millet, bean, cotton, and in soil where it exists as a colonizer of living plants or plant debris. F. nygamai was also reported as a pathogen of the witch-weed Striga hermonthica (Del.) Benth. To our knowledge, no reports are available on its pathogenicity on crops of economic importance. In a survey of species of Fusarium causing seedling blight and foot rot of rice (Oryza sativa L.) carried out in Sardinia (Oristano, S. Lucia), F. nygamai was isolated in association with other Fusarium species—F. moniliforme, F. proliferatum, F. oxysporum, F. solani, F. compactum, and F. equiseti. Infected seedlings exhibited a reddish brown cortical discoloration, which was more intense in older plants. The identification of F. nygamai was based on monoconidial cultures grown on carnation leaf-piece agar (CLA) (2). The shape of macroconidia, the formation of microconidia in short chains and false heads, and the presence of chlamydospores were used as the criteria for identification. Two pathogenicity tests comparing one isolate of F. nygamai with one isolate of F. moniliforme were conducted on rice cv. Arborio sown in artificially infested soil in a greenhouse at 22 to 25°C. The inoculum was prepared by growing both Fusarium species in cornmeal sand (1:30 wt/wt) at 25°C for 3 weeks. This inoculum was added to soil at 20 g per 500 ml of soil. Pre- and post-emergence damping-off was assessed. Both F. nygamai and F. moniliforme reduced the emergence of seedlings (33 to 59% and 25 to 50%, respectively, compared to uninoculated control). After 25 days, the seedlings in infested soil exhibited a browning of the basal leaf sheaths, which progressed to a leaf and stem necrosis. Foot rot symptoms caused by F. nygamai and F. moniliforme were similar, but seedlings infected by F. nygamai exhibited a more intense browning on the stem base and a significant reduction of plant height at the end of the experiment. Either F. nygamai or F. moniliforme were consistently isolated from symptomatic tissue from the respective treatments.

References: (1) L. W. Burgess and D. Trimboli. Mycologia 78:223,1986. (2) N. L. Fisher et al. Phytopathology 72:151,1982.
First Report of a Bulb Decay of Onion by Enterobacter cloacae in Colorado
Authors: Schwartz H. F. , Otto K.
Published: May 2007

Sweet Spanish onion cultivars (Allium cepa L.) in northern Colorado displayed symptoms of postharvest bulb rot during September to November of 1999. This disease appears identical to that reported from infected onions in California in 1988 and is presumably associated with high temperature stress (1). Mature, firm bulbs harvested from scattered fields in Weld County exhibited a brownish discoloration and breakdown of inner scales. Gram negative, rod-shaped, cream-colored bacteria were consistently recovered from infected bulb tissue on nutrient agar. Physiological tests showed that the bacteria utilized glucose in an oxidative and fermentative manner and were catalase positive and oxidase negative. A representative strain was identified by Microbe Inotech Laboratories (St. Louis, MO) as Enterobacter cloacae (Jordan) Hormaeche & Edwards (2) using Biolog analysis, with a similarity index of 0.81. To confirm pathogenicity, a 0.5- to 1.0-ml suspension of bacteria (108 CFU/ml sdw) was injected into firm onion bulbs (7.5 to 10.0 cm diameter). After incubation for 14 days at 22°C in closed plastic bags in the dark, bulbs were cut in half and evaluated. Tan to brown discoloration and initial dry rot, similar to that observed postharvest, was observed in inoculated bulbs. The pathogen was reisolated from six of eight bulbs inoculated with the representative strain. No discoloration or disease developed on eight control bulbs injected with water. To our knowledge, this is the first report of E. cloacae from onion grown in Colorado.

References: (1) A. L. Bishop and R. M. Davis. Plant Dis. 74:692, 1990. (2) Hormaeche and Edwards. Int. J. System. Bacteriol. 30:293, 1960.
Widespread Occurrence of Cotton leaf curl virus on Radish in Pakistan
Authors: Mansoor S. , Mukhtar S. , Hussain M. , Amin I. , Zafar Y. , Malik K. A. , Markham P. G.
Published: May 2007

The current epidemic of cotton leaf curl disease (CLCuD) in Pakistan started in 1988 with the natural host range limited to a few plant species in the family Malvaceae. However, we have observed expansion in the host range of the virus, and several non-Malvaceous plants were found to be infected with the virus. Characteristic symptoms of CLCuD such as leaf curl and enations have been observed on radish plants, primarily in kitchen gardens. However, in 1999, levels of infection of 10 to 90% were observed both in commercial fields and kitchen gardens in the Punjab province of Pakistan. Both symptomatic and nonsymptomatic samples were collected from five different locations. Total DNA was isolated, dot-blotted on nylon membrane, and a full-length clone corresponding to DNA A of cotton leaf curl virus was labeled with 32P dCTP and used as a probe for the detection of a begomovirus. Strong signals were observed in symptomatic plants while no signals were observed in nonsymptomatic plants. Infection with a begomovirus was further confirmed by polymerase chain reaction (PCR) using degenerate primers for DNA A (1). Primers specific for the two distinct begomoviruses associated with CLCuD were also used in PCR reactions (2), and products of the expected size were obtained from all symptomatic samples, confirming infection with begomoviruses similar to those associated with CLCuD. A full-length probe of a nanovirus-like molecule associated with cotton leaf disease (3), called DNA 1 was labeled with 32P dCTP and detected the virus only in symptomatic plants. Similarly, primers specific for DNA 1 (3) amplified a product of expected size when used in PCR. On the basis of symptomatology and the detection of specific viral components associated with the disease, we confirmed that radish plants are infected with Cotton leaf curl virus (CLCuV). Since radish is a short duration crop, infection of CLCuV in radish may not serve as a direct source of infection for the next cotton crop. However, it is a potential threat to tomato crops which overlap with radish in the Punjab province. The detection of CLCuD in radish is another example of the mobilization of begomoviruses to previously unknown hosts.

References: (1) M. R. Rojas et al. Plant Dis. 77:340, 1993. (2) S. Mansoor et al. Pak. J. Bot. 31:115, 1999. (3) Mansoor et al. Virology 259:190, 1999.
Effect of Silicon Rate and Host Resistance on Blast, Scald, and Yield of Upland Rice
Authors: Seebold K. W. , Datnoff L. E. , Correa-Victoria F. J. , Kucharek T. A. , Snyder G. H.
Published: May 2007

Blast-resistant, partially resistant, and susceptible cultivars of rice were planted in soil amended with Si at 0, 500, or 1,000 kg/ha at two locations in eastern Colombia to assess differential responses to leaf blast, neck blast, and leaf scald, and to examine the quantity and quality of grains harvested. Leaf and neck blast on partially resistant and susceptible cultivars were reduced by Si as the rate of Si was increased. Depending on the location, the level of severity of leaf and neck blast on partially resistant cultivars, when fertilized with Si at 500 or 1,000 kg/ha, was lowered to that of resistant cultivars without Si. At both locations, yields were increased by as much as 42%, depending on the cultivar, by Si applied at 1,000 kg/ha. In general, high rates of Si reduced the number of broken grains harvested. Grain discoloration, regardless of cultivar or location, was reduced by as much as 70% at the high rate of Si. The application of Si to complement host resistance to blast and scald appears to be an effective strategy for disease management in rice and provides the added benefit of improving the quantity and quality of rice yields.
Black Point Reaction of Durum and Common Wheat Cultivars Grown Under Irrigation in Southern Saskatchewan
Authors: Fernandez M. R. , Clarke J. M. , DePauw R. M. , Irvine R. B. , Knox R. E.
Published: May 2007

Six durum (Triticum turgidum L. var. durum) and six common (T. aestivum L.) wheat cultivars were compared for reaction to black point under irrigation at two locations in southern Saskatchewan in 1990 to 1992 and 1994. There were individual varietal differences in black point levels within each of the species. The Canada Western Soft White Spring wheat Fielder was the most susceptible and the Canada Western Red Spring wheat Katepwa was the most resistant to black point. The location-cultivar-year interaction was a significant source of variation and a crossover cultivar-environment interaction was significant, suggesting that rank order of cultivars differed with environment. The durum wheat had significantly higher black point levels than the common wheat cultivars in three of the seven environments conducive to black point, two of which were in 1992, and had high overall black point levels. This greater black point severity on the durum wheat cultivars might have been due to cool, wet weather conditions and frosts during seed development that delayed ripening.