bluuebunny/crossref_metadata_2025 huggingface dataset:
Sugarcane Yellow Leaf Disease in Brazil: Evidence of Association with a Luteovirus
Authors: Vega Jorge , Scagliusi Sandra M. M. , Ulian Eugênio C.
Published: May 2007

Evidence of the viral etiology of sugarcane yellow leaf disease (SCYLD), occurring in southeast Brazil, was obtained by light and electron microscopy combined with serology. Light microscopy using epifluorescence illumination showed an abnormal yellow-green fluorescing material in the phloem of SCYLD-affected plants that was rarely observed in control plants. Immunolocalization in tissue-printed (or -blotted) nitrocellulose membranes, using barley yellow dwarf virus (BYDV) serotype PAV antiserum, showed a weak but clearly positive reaction in the phloem. Isometric viruslike particles of 24 to 26 nm in diameter were found by electron microscopy both in situ and in partially purified preparations. Examination of thin sections showed that phloem companion cells contained viruslike particles and presented cytological changes apparently related to the development of virus infection. Partially purified preparations produced UV absorption spectra typical of a nucleoprotein, with high absorbance at 260 nm, as expected for isometric virus particles. Virus particles were observed in extracts and partially purified preparations using immunosorbent electron microscopy with BYDV-PAV antiserum. Plate-trapped antigen enzyme-linked immunosorbent assays with the same antiserum indicate a weak serological relationship between BYDV-PAV and SCYLD-associated virus.
Effect of Some Host and Microclimate Factors on Infection of Tomato Stems byBotrytis cinerea
Authors: O'Neill T. M. , Shtienberg D. , Elad Y.
Published: May 2007

The susceptibility of tomato stems to infection by Botrytis cinerea and the influence of temperature and humidity on disease development were investigated with stem pieces and whole plants. Stem rotting resulted after inoculation of wounded stems with a conidial suspension in water or with dry conidia; no symptoms developed following inoculation of unwounded stems. The proportion of inoculated stems developing Botrytis rot increased as the inoculum concentration was increased from 10 to 10,000 conidia per stem. Stem susceptibility to infection declined from 60 to 8% as wound age increased from 0 to 24 h before inoculation. Wounded stem pieces maintained in a low vapor pressure deficit (VPD) environment (<0.2 kPa) remained susceptible for a longer period than those maintained at a high VPD. Infection and stem rotting occurred at temperatures of 5 to 26°C, with disease development most rapid at 15°C. Sporulation was optimal at 15°C and did not occur within 20 days of incubation at 5 or 26°C. Incubation at high humidity following inoculation of fresh wounds (VPD <0.2 kPa) did not increase infection incidence or tissue rotting, compared with incubation at a VPD >1.3 kPa; however, incubation at the lower VPD did increase the intensity of sporulation.
Cultivar and Spacing Effects on Transmission of Phytophthora parasitica in an Ebb-and-Flow Subirrigation System
Authors: Strong Stephen S. , Behe Bridget K. , Deneke C. Fred , Bowen Kira L. , Keever Gary J.
Published: May 2007

Phytophthora parasitica was transmitted within 6 weeks from vinca (Catharanthus roseus) plants growing in infested potting mix, on the drain end of ebb-and-flow benches, to plants in noninfested potting mix. Transmission of Phytophthora was very low when potting mix was not pasteurized. When potting mix was steam pasteurized, infection of plants, disease incidence, and severity increased with time and decreased with distance from plants in infested pots. The cultivar Pretty in Pink was more susceptible to infection by P. parasitica than cv. Peppermint Cooler, allowing more rapid and severe disease development as well as pathogen dissemination and transmission. Pot spacing did not significantly affect transmission of P. parasitica on an ebb-and-flow bench.
Identification of Resistance to Pseudocercosporella herpotrichoides in Triticum monococcum
Authors: Cadle M. M. , Murray T. D. , Jones S. S.
Published: May 2007

Eyespot is an important disease of wheat in the United States Pacific Northwest. Genes Pch1, located on chromosome 7D, and Pch2, located on chromosome 7A, are the only known sources of eyespot resistance in hexaploid wheat. A core collection of Triticum monococcum, a close relative of the A-genome donor of bread wheat, consisting of 118 accessions from 26 countries was screened for resistance using a β-glucuronidase-transformed strain of the pathogen. Fifty-two (44%) accessions from 15 different countries were resistant. More than half of the accessions collected in Turkey (26 of 42) were resistant. Two accessions were more resistant than resistant cultivars Cappelle Desprez (Pch2) and Madsen (Pch1). Screening these accessions for the isozyme marker Ep-A1b, which is linked with Pch2 in hexaploid wheat, revealed variation but no association with resistance. These results indicate T. monococcum is a new source of resistance to Pseudocercosporella herpotrichoides that potentially contains more effective resistance to P. herpotrichoides than that conferred by either Pch1 or Pch2.
Interaction of Temperature and Moisture on Infection of Wild Rice by Bipolaris oryzae in the Growth Chamber
Authors: Percich J. A. , Nyvall R. F. , Malvick D. K. , Kohls C. L.
Published: May 2007

Infection of wild rice (Zizania palustris) flag leaves by Bipolaris oryzae was studied at temperatures of 5 to 35°C and wet periods of 2 to 36 h after inoculation. Lesion densities (lesions/cm2) increased with increasing wet periods depending on optimum temperature. High rates of infection occurred at 25 and 30°C and generally increased with continuous wet periods of 16, 18, 24, and 28 h. There were no lesions at 5°C and few at 10 and 35°C. Lesion densities declined when wet periods of 2, 4, or 6 h were interrupted by dry periods of 4, 6, 8, 10, or 12 h followed by a final 14 h of wetness. Lesion densities decreased at all temperatures with increased dry periods regardless of the initial wet period. The interaction of dry period length × wet period length × temperature was significant at the 0.5% level. With continuous wet periods, lesion numbers were highest at 25 to 30°C.
Incidence of Colletotrichum coccodes in Certified Potato Seed Tubers Planted in Washington State
Authors: Johnson Dennis A. , Rowe Randall C. , Cummings Thomas F.
Published: May 2007

Incidence of Colletotrichum coccodes in lots of certified seed tubers planted in Washington state, originating from nine western and midwestern states in the United State and two provinces in Canada, ranged from 0 to 90% in 1994 and 0 to 53% in 1995. In 1994, significant interactions between state/province and cultivar, and between seed grower and cultivar, were evident. In 1995, incidence of C. coccodes in seed lots did not vary significantly among states and cultivars. C. coccodes was not isolated from nuclear seed tubers and incidence of infected tubers was higher with higher seed generations. The fungus was isolated from the tuber periderm and outer medulla tissues and isolation frequency was greater from tuber stem ends than from either bud ends or lateral sections. Significantly greater stem infections developed in plants grown from seed tubers in which C. coccodes had been detected than in plants grown from seed tubers from which C. coccodes had not been isolated. This study confirms that C. coccodes is distributed among potato-production areas within seed tubers, and that seed tuber infection increases the incidence of early-season plant infection.
Wilt and Root Diseases ofAsclepias tuberosaL.
Authors: Tsror (Lahkim) L. , Hazanovski M. , Erlich O. , Dagityar N.
Published: May 2007

Chlorosis and wilting, followed by weak flowering or death, have been occurring in Asclepias tuberosa plants grown in Israel. Roots have been rotted and tuberous roots have shown dark lesions, sometimes with sclerotia. A binucleate Rhizoctonia sp. was detected on 39% and Pythium intermedium on 23% of diseased samples. Other organisms were less prevalent. Wilting began 7 days after seedlings were inoculated with P. intermedium or the binucleate Rhizoctonia sp. or both, with disease incidence ranging from 25 to 65% and disease severity index ranging from 0.30 to 0.85 (scale of 0 to 3). Healthy tuberous roots inoculated with the binucleate Rhizoctonia sp. exhibited dry rot within 4 to 7 days, and irregular black sclerotia of the pathogen were present 2 weeks later. This is the first report of either a binucleate Rhizoctonia sp. or P. intermedium occurring in A. tuberosa.
First Report of Alternaria Brown Spot of Minneola Tangelo in Turkey
Authors: Canihos Y. , Erkilic A. , Timmer L. W.
Published: May 2007

Minneola tangelo, a hybrid of Dancy tangerine and Duncan grapefruit, is widely grown in Turkey for export to Europe. In 1995, 2,000 ha of diseased Minneola tangelo trees were observed in the Cukurova region. Ninety percent of orchards in this region were diseased but disease severity depended upon the location and the disease control strategies employed in each orchard. Symptoms were typical of Alternaria brown spot (1). Fruit symptoms included light brown, slightly depressed spots to circular and dark brown areas on the external surface. On leaves, symptoms ranged from small brown circular spots to irregular blighted areas with characteristic yellow halos. The apices of some young shoots were defoliated. Infected young fruit and leaves often dropped from the tree and the mature fruit were unmarketable due to lesions on the fruit. Alternaria was consistently isolated from diseased leaves and fruit on potato dextrose agar and produced dark brown mycelia and pigmented septate conidia similar to those described previously (1). Detached immature Minneola leaves were inoculated with aqueous conidial suspensions of 15 isolates and maintained in a chamber at near 100% relative humidity for 3 days at 26°C. Thirteen of these isolates caused necrotic lesions on the leaves similar to those observed in the field, i.e., dark, necrotic spots with necrosis extending outward on some veins. Alternaria was reisolated from all infected leaves. This is the first report of Alternaria brown spot of Minneola tangelo in Turkey.

Reference: (1) Z. Solel. Plant Pathol. 40:145, 1991.
First Report of Monosporascus cannonballus on Melons in Saudi Arabia
Authors: Karlatti R. S. , Abdeen F. M. , Al-Fehaid M. S.
Published: May 2007

In the late summer of 1996, a root rot and vine decline was noticed on greenhouse grown melons (Cucumis melo L.) at the National Agriculture and Water Research Center, Riyadh, Saudi Arabia. Melons were grown on sandy clay soil and peat moss was spot applied as organic manure. The pH of the soil was 7.8. Disease symptoms first appeared at early stage of fruit maturity of the crop. Diseased vines exhibited stunting, yellowing, and, at a late stage, complete collapse of the leaf canopy. The roots showed discoloration, discrete lesions on all root systems, and loss of secondary and tertiary feeder roots. Numerous perithecia were observed on the secondary and tertiary roots only. Each ascus contained one large spherical ascospore. The fungus was isolated on potato dextrose agar and identified as a Monosporascus sp. (2). A pure culture was confirmed as Monosporascus cannonballus Pollack & Uecker. IMI (373485(01)) by IMI, Surrey, U.K. Pathogenicity was confirmed in a temperature-controlled growth chamber on the melon cv. Red Queen(F1). A medium that consisted of 3 liters of sand, 275 g of dried ground oat hulls, and 450 ml of distilled sterile water (1) was inoculated and incubated for 40 days. The colonized medium (100 ml) was mixed with a pasturized potting mix (sand/peat moss; 1:1) in 17-cm-diameter plastic pots. Five seeds were planted in each pot and, 15 days after germination, seedlings were thinned to one per pot. Noninfested pots were inoculated with sterile sand/oat hull medium. The pots were placed in chambers maintained at 30/20°C, day/night. At various intervals, the onset and severity of symptom expression were recorded. The isolate caused stunting and root necrosis. The fungus was reisolated from symptomatic plants. This report extends the known range of M. cannonballus to include Saudi Arabia. Other reports of this fungus are from India, Israel, Japan, Libya, Mexico, Spain, Taiwan, Tunisia, and the U.S.

References: (1) J. C. Mertely et al. Plant Dis. 77:667, 1993. (2) F. G. Pollack and F. A. Uecker. Mycologia 66:346, 1974.
Comparison of Techniques for Detection of Barley Yellow Dwarf Virus-PAV-IL
Authors: Figueira Antonia R. , Domier Leslie L. , D'Arcy Cleora J.
Published: May 2007

Detection of barley yellow dwarf virus (BYDV)-PAV-IL by an improved nucleic acid hybridization technique, using a nonradioactive probe with chromogenic and chemiluminescent substrates, was compared with detection by polymerase chain reaction (PCR), double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) with polyclonal antibodies, and triple antibody sandwich ELISA with polyclonal and monoclonal antibodies. Each method was used to detect purified virus and virus in sap extracts from infected oat leaves. The detection limits for both ELISA procedures were 1 ng of purified BYDV-PAV-IL and the equivalent of 78 ng of infected tissue. Nucleic acid hybridization with either chemiluminescent or chromogenic substrates also detected as little as 1 ng of purified BYDV-PAV-IL, but it was slightly more sensitive at detecting virus in tissue extracts (25 ng of infected tissue). The most sensitive detection technique was PCR amplification, which could detect as little as 0.1 pg of RNA extracted from purified virus and detected viral RNA in the equivalent of 0.5 pg of infected leaf tissue.
Ultrastructural Studies of the Effects of Allium sativum on Phytopathogenic Fungi in vitro
Authors: Bianchi Alberto , Zambonelli Alessandra , D'Aulerio Aldo Zechini , Bellesia Franco
Published: May 2007

A study was made of the effects of garlic on the development of mycelium in the following phytopathogenic fungi: Fusarium solani (Mart.) Sacc., Rhizoctonia solani Kühn, Pythium ultimum Trow var. ultimum, and Colletotrichum lindemuthianum (Sacc. and Magnus) Briosi and Cav. A suspension of micronized garlic powder, which has volatile organic compounds mainly consisting of linear chain aldehydes, allyl sulfides and disulfides, was used for the trials. Mycelial development of the fungi was strongly inhibited at the maximum concentration of the aqueous extract tested (100 ml/liter); however only the growth of P. ultimum var. ultimum was entirely blocked. Transmission and scanning electron microscopy revealed cytomorphological alterations of the hyphae treated with garlic. R. solani and C. lindemuthianum hyphae appeared especially collapsed, while those of F. solani were less damaged, although thinner than the control hyphae. A general increase in vacuolization was also observed, with consequent reduction in the cytoplasm of the treated fungal cells. R. solani also revealed a thickening of the cell wall, whereas C. lindemuthianum revealed a singular accumulation of osmiophil bodies immediately under the cell membrane.
Distribution of Mating Types and the Teleomorph of Ascochyta rabiei on Chickpea in Turkey
Authors: Kaiser W. J. , Küsmenoglu I.
Published: May 2007

One hundred forty-five isolates of Ascochyta rabiei, the cause of Ascochyta blight of chickpea, were collected from chickpea (Cicer arietinum) in 23 provinces of Turkey. Each isolate was tested for mating type with compatible MAT1-1 and MAT1-2 tester isolates. Both mating types were found in 18 provinces. Of the isolates tested, 59% were MAT1-1 and 41% were MAT1-2. A great deal of variation in cultural characteristics was observed among the Turkish isolates in mycelial growth, sporulation, and colony appearance. Mature pseudothecia of Didymella rabiei, the teleomorph (sexual state) of A. rabiei, developed on naturally infested chickpea debris collected in 15 of 20 provinces when incubated under favorable conditions. This is a new geographic record for D. rabiei. The teleomorph may play an important role in long-distance dissemination of the pathogen and in increasing genetic diversity in the pathogen population in Turkey.
Bacterial Leaf Blight on shrunken-2 Sweet Corn
Authors: Pataky J. K. , du Toit L. J. , Kerns M. R.
Published: May 2007

Severity of bacterial leaf blight (BLB, caused by Acidovorax avenae subsp. avenae) on shrunken-2 (sh2) sweet corn hybrids grown in BLB-conducive environments and sporadic outbreaks of BLB in recent years warranted evaluations of the potential for this disease to cause economic losses. BLB symptoms on 122 sh2 hybrids, 30 sh2 inbred lines, and 29 crosses of the inbreds and the effects of BLB on yield (ear weight and marketable ears) were evaluated in 1994 and 1996. BLB severity ratings for 122 hybrids averaged 3.3 and 3.7 (on a scale of 1 to 9) in 1994 and 1996, respectively. Hybrid means ranged from 1.8 to 5.5 in 1994 and from 1.9 to 5.7 in 1996, with Bayesian LSD values of 1.20 and 1.22, respectively. There were no differences in BLB ratings among hybrids with yellow, white, or bicolored kernels. Severity of symptoms on 30 sh2 inbreds ranged from 1.5 to 5.7, whereas the reactions of 29 crosses of the inbreds ranged from 1.9 to 5. The slope coefficient of the regression of crosses on mid-parent values was not different from 1. Thus, mid-parent values gave a good indication of severity of BLB symptoms on crosses, with the exception of a few crosses that tended to be more severely infected than expected based on mid-parent values. Ear weights and number of marketable ears differed among hybrids in the 1994 trial, but there was no significant effect of BLB treatments on either of these measures of yield. In 1996, ear weights in inoculated plots were 10 and 15% lower than those from noninoculated plots for 2 of 12 hybrids. Despite moderately severe foliar symptoms, BLB did not affect yield substantially in these trials even among hybrids with the most susceptible reactions.
Improved Control of Green Mold of Citrus with Imazalil in Warm Water Compared with Its Use in Wax
Authors: Smilanick J. L. , Michael I. F. , Mansour M. F. , Mackey B. E. , Margosan D. A. , Flores D. , Weist C. F.
Published: May 2007

The effectiveness of imazalil for the control of citrus green mold (caused by Penicillium digitatum) improved significantly when fruit were treated with heated aqueous solutions of the fungicide as compared with the current commercial practice of spraying wax containing imazalil on fruit. When applied at less than 500 μg·ml-1in solutions heated to 37.8°C, control of postharvest green mold of citrus was significantly superior to applications of 4,200 μg·ml-1imazalil in wax sprayed on fruit at ambient temperatures. The improvement in imazalil efficacy was obtained with a decrease in fungicide residues on the fruit. Residues of about 3.5 μg·g-1imazalil deposited by the application of imazalil in wax reduced the incidence of green mold on lemons from 94.4% among untreated controls to 15.1%, whereas an equal residue deposited by passing fruit through heated aqueous imazalil reduced green mold incidence to 1.3%. Similar differences were found in tests with oranges. Residues of 2 and 3.5 μg·g-1imazalil were needed to control the sporulation of P. digitatum on oranges and lemons, respectively. The mode of application of imazalil did not influence control of sporulation. The influence of immersion time, imazalil concentration, and solution temperature on imazalil residues on oranges and lemons was determined in tests using commercial packing equipment, and a model that describes residue deposition was developed. Residues after a 30- or 60-s treatment in heated aqueous imazalil were sufficient to control sporulation, but residues after 15-s treatments were too low and required an additional application of 1,070 μg·ml-1imazalil in wax to deposit an amount of imazalil sufficient to control sporulation. An imazalil-resistant isolate of P. digitatum was significantly controlled by heated aqueous imazalil. The incidence of green mold of navel oranges was reduced from 98.8 to 17.4% by treatment in 410 μg·ml-1imazalil at 40.6°C for 90 s. However, control of the resistant isolate required imazalil residues on the fruit of 7.9 μg·g-1, which is within the U.S. tolerance of 10 μg·g-1but above the 5 μg·g-1tolerance of some countries that import citrus fruit from the United States.
First Report of Cucurbit Aphid-borne Yellows Luteovirus in Lebanon
Authors: Abou-Jawdah Y. , Sobh H. , Fayyad A.
Published: May 2007

Recently, Lecoq et al (1992) reported a new yellowing disease of cucurbits in France caused by cucurbit aphid-borne yellows luteovirus (CABYV) (1). Yellowing of older leaves of cucurbits has been observed in Lebanon for the past few years. Transmission tests showed that the disease incitant could be transmitted by Aphis gossypii in a persistent, circulative manner from muskmelon plants (Cucumis melo) to cucumber (C. sativus), muskmelon (C. melo), and squash (Cucurbita pepo) plants. Extracts from these plants reacted positively in enzyme-linked immunosorbent assays (ELISAs) with an antiserum prepared to a French isolate of CABYV. Surveys conducted in 1995 and 1996 showed that CABYV was widely distributed in the major cucurbit-growing areas along the Lebanese coast from north to south, and in the Beqaa plain. It was detected year round, alone or in mixed infections with mosaic-inducing viruses. The highest frequencies were recorded between May and October. CABYV and zucchini yellow mosaic potyvirus (ZYMV) were the most commonly detected viruses in outdoor cucurbits, including squash, cucumber, and melon. However, in protected cultivations (plastic tunnels), only a small proportion of cucumber plants showing similar yellowing symptoms reacted positively with CABYV antiserum in ELISAs, suggesting another cause to account for these symptoms.

Reference: (1) H. Lecoq et al. Plant Pathol. 41:479, 1992.
A Vascular Wilt of Fragrant Sumac Caused by Fusarium oxysporum
Authors: O'Mara J. , Tisserat N.
Published: May 2007

A branch from a wilting fragrant sumac tree (Rhus aromatica Aiton) in an established ornamental planting was submitted to the Plant Disease Diagnostic Laboratory in 1994. The branch exhibited dark brown streaks in the sapwood. Fusarium oxysporum Schlechtend.:Fr. was subsequently isolated from the discolored wood. To confirm pathogenicity, 2-year-old potted sumacs (0.5 to 1 m high)—fragrant, skunkbrush (R. trilobata Nutt. ex Torr. & A. Gray), smooth (R. glabra L.), and staghorn (R. typhina L.) species—were inoculated with the isolate by cutting into the bark to the xylem with a scalpel and applying approximately 0.1 ml of a 106 conidia/ml suspension into the wound. Inoculated trees were then placed on a greenhouse bench. Three trees of each species were inoculated and the experiment was repeated once. All inoculated skunkbrush and fragrant sumacs wilted and died within 3 months, whereas none of the smooth and staghorn sumacs were affected. F. oxysporum was consistently reisolated from wilted, but not healthy, trees. The host range of this isolate (FRC 0-1916) is different from that of F. oxysporum f. sp. rhois W. C. Synder, Toole, & Hepting, which was reported to be pathogenic to staghorn but not other sumac species (1). This is the first report of F. oxysporum causing wilt of fragrant and skunkbrush sumacs.

Reference: (1) E. R. Toole. Phytopathology 39:754, 1949.
Expanded Range of Cylindrocladium colhounii in the United States
Authors: El-Gholl N. E. , Schubert T. S. , Walker S. E. , Stone J. K.
Published: May 2007

Plant pathologists in Florida and Oregon have recently found Cylindrocladium colhounii for the first time on two new ornamental plant species. Brown, pinpoint leaf spots were observed on Callistemon rigidus (stiff bottlebrush) in a Florida nursery. C. colhounii was isolated consistently from these lesions. To confirm Koch's postulates, 25 ml of aconidial suspension at 96,000 conidia per ml was used to spray a 38.1-cm branch of C. rigidus. Plants were maintained in a moist chamber at room temperature (25 ± 2°C). Symptoms appeared within 3 days, and included brown, pinpoint spots (1 mm or less) occurring on both leaf surfaces, sunken blotches, and blight. The fungus was consistently reisolated from symptomatic tissue. In Oregon, the first detection of C. colhounii was from leaf spots on Gaultheria procumbens (wintergreen) in a nursery. No proof of pathogenicity was done in Oregon on G. procumbens. C. colhounii has now been reported on 14 host genera in 10 families from Australia, India, Mauritius, South Africa, and the U.S. (FL, HI, LA, NC, OR, SC) (1–4).

References: (1) P. W. Crous and M. J. Wingfield. Mycopathologia 122:45, 1993. (2) A. Peerally. Mycotaxon 40:323, 1991. (3) A. Y. Rossman. Mycol. Pap. No. 150, Commonw. Mycol. Inst., Kew, Surrey, England, 1983. (4) J. Y. Uchida and M. Aragaki. Plant Dis. 81:298, 1997.
Detection of a Severe Isolate of Impatiens Necrotic Spot Virus Infecting Lisianthus in Florida
Authors: McGovern R. J. , Polston J. E. , Harbaugh B. K.
Published: May 2007

In May 1997, inclusions typical of a tospovirus were visualized by light microscopy in leaf tissue of lisianthus (Eustoma grandiflorum) exhibiting stunting, necrotic ringspots, leaf distortion, and systemic necrosis. Wilting and plant death were the final symptoms observed. Affected plants occurred at low incidence (<0.1%) in greenhouse-grown lisianthus in Manatee County, FL. Symptomatic tissue tested positive for impatiens necrotic spot virus (INSV) and negative for tomato spotted wilt virus (TSWV) with enzyme-linked immunosorbent assay (ELISA; Agdia, Elkhart, IN). Mechanical transmission of the virus to lisianthus and tomato was attempted by triturating 1 g of symptomatic leaf tissue in 7 ml of a buffer consisting of 0.01 M Tris and 0.01 M sodium sulfite, pH 7.3. Six plants of lisianthus cv. Maurine Blue and three of tomato (Lycopersicon esculentum) cv. Lanai at the second true-leaf stage were inoculated following abrasion of leaves with Carborundum. An equal number of controls were inoculated with buffer alone. Plants were maintained in a controlled environment chamber with a 12-h photoperiod, day/night temperatures of 21/16°C, and light intensity of 120 μE · s-l · m-2. Transmission rates were 100 and 0% to lisianthus and tomato, respectively. Chlorotic local lesions followed by chlorotic ringspots were observed in inoculated lisianthus leaves 4 days after inoculation. Stunting, leaf distortion, and necrotic ringspots appeared in noninoculated leaves of lisianthus plants within 3 to 4 weeks after inoculation. Buffer-inoculated lisianthus and all tomato plants remained symptomless and tested negative for INSV by ELISA. All symptomatic lisianthus tested positive for INSV by ELISA. The symptoms we observed in lisianthus due to infection by INSV were more severe than those previously reported in this host (1,2). The occurrence of such strains of INSV at high incidences could pose a significant threat for commercial lisianthus production.

References: (1) M. K. Hausbeck et al. Plant Dis. 76:795, 1992. (2) H. T. Hsu and R. H. Lawson. Plant Dis. 75:292,1991.
A New Pathotype of Xanthomonas campestris pv. armoraciae That Causes Bacterial Leaf Spot of Radish
Authors: Sahin F. , Miller S. A.
Published: May 2007

A previously undescribed pathotype of Xanthomonas campestris pv. armoraciae was found in 1995 on radish plants grown on organic soil in north central Ohio. Radish foliage developed numerous small, circular, water-soaked black spots, eventually with yellow halos, on the underside of the leaves, giving the foliage a yellowish, ragged appearance. Spots were also visible on the upper surface of leaves and on petioles. Yellow xanthomonad-like bacteria were consistently isolated from the lesions and confirmed as the causal agent of the disease by fulfilling Koch's postulates. All five strains purified were gram negative, rod shaped, motile, aerobic, oxidase negative, catalase positive, amylolytic, and pectolytic. They were identified as X. campestris pv. armoraciae by fatty acid methyl ester (FAME) analysis (similarity indices [SI] range = 0.21 to 0.39), the Biolog 95 GN reaction (SI range = 0.31 to 0.36), and serological reactions with X. campestris pv. campestris/X. campestris pv. armoraciae-specific monoclonal antibodies X9, X11, X21, A11, and B35 (1). All strains caused bacterial leaf spot on collard, kale, radish, horseradish, and cabbage but not on tomato or pepper. These strains were different from X. campestris pv. raphani, which is pathogenic on kale, radish, cabbage, tomato, and pepper, but not on horseradish. These strains also differed from other previously reported strains of X. campestris pv. armoraciae that do not cause infection on kale and radish (1,2). This is the first report on the existence of a different pathogenic group within X. campestris pv. armoraciae that can cause bacterial spot on kale and radish.

References: (1) A. M. Alvarez et al. Phytopathology 84:1449, 1994; (2) H. E. White. Phytopathology 20:653, 1930.
Occurrence of Stem and Crown Rot of Gaillardia grandiflora, Caused by Sclerotinia sclerotiorum, in California
Authors: Koike S. T.
Published: May 2007

Gaillardia grandiflora, or blanket flower, is a perennial, herbaceous composite used as an ornamental plant. Following a series of rains in January, 1997, landscape plantings of G. grandiflora in Monterey County, CA, exhibited symptoms of a previously undescribed disease. Affected stems turned gray to tan and became dry and brittle. Large branches often developed cracks. Attached leaves and flowers wilted and turned tan. Infections on the smaller stems and branches sometimes spread to the main stem and crown of the plant, resulting in plant death. White mycelia and large, irregular, black sclerotia (3 to 6 mm in diameter) were occasionally observed on external surfaces of infected stems and crowns. However, the internal pith cavity of diseased stems often contained abundant mycelia and sclerotia. Isolations from symptomatic stems, mycelia, and sclerotia produced colonies of Sclerotinia sclerotiorum. Pathogenicity was confirmed by culturing representative isolates on potato dextrose agar and allowing the fungus to colonize sterilized toothpicks placed on the surface of the agar (1). The pointed tips of the toothpicks were inserted approximately 3 mm deep into stems of potted G. grandiflora cv. Goblin plants, which were incubated in plastic bags for 48 h and then kept in a greenhouse. After 10 to 14 days, symptoms and mycelia similar to those originally observed developed on inoculated plants and S. sclerotiorum was reisolated. Stems on plants left for 21 or more days contained abundant sclerotia. Plants inoculated with sterile, uncolonized toothpicks did not develop disease. This pathogenicity test was repeated and the results were similar. This is the first report of G. grandiflora as a host of S. sclerotiorum.

Reference: (1) Y. Yanar et al. Plant Dis. 80:342, 1996.
Field Response of New Peanut Cultivar UF 91108 to Tomato Spotted Wilt Virus
Authors: Culbreath A. K. , Todd J. W. , Gorbet D. W. , Shokes F. M. , Pappu H. R.
Published: May 2007

Epidemics of spotted wilt, caused by tomato spotted wilt tospovirus (TSWV), were monitored in field plots of the new runner-type peanut (Arachis hypogaea) cv. UF 91108, in advanced breeding line F 84 × 9B-4-2-1-1-2-b2-B, in runner-type peanut cvs. Southern Runner and Florunner, and in Virginia-type cv. NC-V11 at two locations in 1994 and 1995. Epidemics of spotted wilt were suppressed in UF 91108 compared to the standard runner-type cv. Florunner. Final disease incidence, standardized area under the disease progress curve values, and final disease intensity ratings were lower in UF 91108 than in Florunner and were similar to those in the moderately resistant cv. Southern Runner. Results indicate that new cv. UF 91108 represents a new potential tool for management of spotted wilt in peanut production areas of the southeastern United States. UF 91108 is the first peanut cultivar in which an oil composition of approximately 65% oleic acid is combined with a moderate level of field resistance to TSWV. Epidemics of spotted wilt also were suppressed in breeding line F 84 × 9B-4-2-1-1-2-b2-B. Across the four tests, the effects of NC-V11 on epidemic development, final incidence, and spotted wilt intensity ratings were not consistent relative to the other genotypes. Use of final disease intensity ratings provided separation of the genotypes similar to use of final incidence of spotted wilt. Assessment values by these two methods were highly correlated. In three of four experiments, final disease intensity ratings were more closely correlated with pod yield than was final incidence. The new intensity rating method described in this paper requires much less time and effort than determining disease incidence and may be a practical alternative to individual plant assessment for characterization of genotype responses to TSWV.
Reduced Field Spread of Potato Leafroll Virus in Potatoes Transformed with the Potato Leafroll Virus Coat Protein Gene
Authors: Thomas P. E. , Kaniewski W. K. , Lawson E. C.
Published: May 2007

Russet Burbank potato was transformed with plant expression vectors containing the potato leafroll luteovirus (PLRV) coat protein (CP) gene. Transgenic potato lines contained a gene expression cassette with two copies of a PLRV CP gene in which the nucleotide sequence was modified to improve expression of the gene. In addition, the two copies of the PLRV CP gene were each driven by a different promoter. Field test screening for PLRV resistance identified 15 lines which showed moderate resistance to PLRV infection and virus titer build-up and a longer incubation period for systemic infection. By conducting field resistance assays during a period when the vector of PLRV was not present, it was possible to test whether the observed resistance was sufficient to restrict aphid transmission of PLRV in a field test. Two years of field testing demonstrated that PLRV-spread from an infected plant to adjacent healthy plants of the same line was severely restricted in nearly all the transgenic lines in the field. These lines have useful resistance to PLRV and could aid in managing PLRV disease in Russet Burbank potato.
Effect of Storage on Viability of Fusarium Head Blight-Affected Spring Wheat Seed
Authors: Gilbert J. , Tekauz A. , Woods S. M.
Published: May 2007

The effects of storage temperature and duration on germination, emergence, and vigor of Fusarium head blight-affected seed were studied in the spring wheat cvs. Glenlea and Roblin. Seed was stored at -10, 2.5, 10, or 20°C. Germination was assessed at cold (5°C) and moderate 20/15°C for 16/8 h daily) temperatures following 0, 8, 16, and 24 weeks of storage. Emergence from a soilless mix was counted 10 days after planting. Vigor was assessed following germination by measuring root and shoot lengths and in emerged plants by determining dry shoot weights. Germination after storage at the three colder temperatures decreased with length of storage, but storage at 20°C did not affect germination. Overall, germination of Fusarium-affected seed at moderate temperatures was significantly lower than for healthy seed. Germination of infected seed at 5°C was better than at moderate temperatures, probably due to lack of fungal activity at low temperatures. Seed treatment with Vitaflo 280 improved germination, but not emergence, of infected seed. However, roots from treated infected seed were shorter than from untreated seed. Emergence of infected seeds was better after storage at 10 and 20°C than at -10 and 2.5°C. Storage temperature did not significantly affect vigor. Dry shoot weight at 14 days was lower after storage at -10 than at 20°C.
Sensitivity of Cladosporium caryigenum to Propiconazole and Fenbuconazole
Authors: Reynolds Katherine L. , Brenneman Timothy B. , Bertrand Paul F.
Published: May 2007

Monoconidial isolates of the pecan scab fungus, Cladosporium caryigenum, were obtained in 1993 and 1994 from one pecan orchard each in Jeff Davis and Troup counties in Georgia, counties with no previous history of exposure to demethylation-inhibiting (DMI) fungicides. Isolates were grown on potato dextrose agar (PDA) amended with propiconazole or fenbuconazole at 0,0.0001, 0.0005, 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1.0, or 5.0 µg ml-1. After 4 to 5 weeks at 25°C, the diameter of each colony was measured. Relative growth was expressed as the colony diameter for each fungicide concentration as a percentage of the diameter on unamended PDA. (ED)50 values for both fungicides in all years and locations were lognormally distributed. Mean (ED)50 values ranged from 0.19 to 0.30 µg ml-1 for fenbuconazole and 0.12 to 0.17 µg ml-1 for propiconazole. There were highly significant positive correlations between sensitivity to propiconazole and sensitivity to fenbuconazole at all locations and years, indicating significant potential for development of cross-resistance to these compounds. A discriminatory concentration of 0.2 µg ml-1 propiconazole was selected for further monitoring of DMI sensitivity. With this discriminatory concentration, a sample size of 50 isolates was estimated to be sufficient to detect a difference of 8.3% in mean relative growth between two populations.
Detection of Cymbidium Mosaic Potexvirus and Odontoglossum Ringspot Tobamovirus from Thai Orchids by Rapid Immunofilter Paper Assay
Authors: Tanaka S. , Nishii H. , Ito S. , Kameya-Iwaki M. , Sommartya P.
Published: May 2007

During 1992 to 1994, 442 orchid plants from 24 genera in 43 nurseries and locations in eight provinces of northern, central, and southern regions of Thailand were examined for Cymbidium mosaic potexvirus (CyMV) and Odontoglossum ringspot tobamovirus (ORSV) with rapid immunofilter paper assay (RIPA). Both viruses were confirmed in all three regions. However, CyMV was detected in 17 genera in 93% nurseries, while ORSV was detected in only four genera (Arachnis, Cattleya, Oncidium, and Vanda) in 40% of nurseries tested. These results indicate that CyMV is more prevalent than ORSV in Thailand. Mixed infections of ORSV and CyMV were often found, and double infections were observed in 95% of ORSV-infected plants. The virus infections were divided into two categories: infection by CyMV alone and double infection by both viruses in Cattleya and Oncidium. CyMV was often detected alone from symptomatic or asymptomatic plants of certain orchid genera. In Oncidium, however, CyMV was detected alone from 79% of plants without symptoms, while both viruses were detected from 90% of plants with mosaic and necrotic spot symptoms on leaves. Expression of symptoms may be promoted by the double infection of CyMV and ORSV in Oncidium.
Prevalence and Pathogenicity of Foot and Root Rot Pathogens of Pea in Southern Scandinavia
Authors: Persson L. , Bødker L. , Larsson-Wikström M.
Published: May 2007

The occurrence of root pathogens of vining pea was determined in field surveys in Sweden and Denmark from 1989 to 1994. The most serious yield-reducing root pathogen, Aphanomyces euteiches, was found in approximately one-third of the sampled fields in both Sweden and Denmark. In a few fields severely infested with this pathogen, there was a total crop failure. The most frequently isolated pathogens were Phoma medicaginis var. pinodella and Fusarium solani; the latter also was isolated from vascular tissue up to the seventh node level. Other pathogens isolated from roots were F. avenaceum, F. oxysporum, F. culmorum, Chalara elegans, Pythium irregulare, and Mycosphaerella pinodes. In greenhouse pathogenicity tests, A. euteiches caused the most severe root damage and plant death of pea, followed by F. avenaceum and P. irregulare. There was an inverse relationship between field disease severity index and yield for fields infested with A. euteiches.
Evaluation of an Aeroponics System to Screen Maize Genotypes for Resistance toFusarium graminearumSeedling Blight
Authors: du Toit Lindsey J. , Kirby H. Walker , Pedersen Wayne L.
Published: May 2007

A noncirculating aeroponics system was evaluated as a method for rapid screening of maize genotypes for resistance to Fusarium graminearum seedling blight/root rot. The system allows for nondestructive, repetitive sampling of seedlings for assessing disease progress and seedling growth. Shoot growth and root rot were assessed at 3-day intervals, and final shoot and root dry weight were determined 15 days after inoculation. The nine hybrids screened differed in severity of root rot as early as 6 days after inoculation, indicating differences in resistance to F. graminearum. Inoculation did not always significantly affect shoot growth, root dry weight, or shoot dry weight, but differences in these agronomic traits were observed among hybrids.LH119 × LH51 and Pioneer Brand 3379 showed the greatest resistance to root rot. Area under-disease progress curve and a critical stage of disease assessment (9 days after inoculation) gave similar rankings of hybrids for root rot resistance, indicating that a single disease assessment (versus multiple assessments) may be adequate in screening for resistance with this aeroponics system.
Rapid Evaluation of Plant Extracts and Essential Oils for Antifungal Activity Against Botrytis cinerea
Authors: Wilson C. L. , Solar J. M. , El Ghaouth A. , Wisniewski M. E.
Published: May 2007

A rapid assay to determine antifungal activity in plant extracts and essential oils is described. Wells in microtiter plates were loaded with Botrytis cinerea spores and plant extracts or essential oils. Subsequent changes in optical density following spore germination in the wells was measured after 24 h using an automatic microtiter plate reader driven by a software program developed for this purpose. Extracts from 345 plants and 49 essential oils were evaluated for their antifungal activity against B. cinerea. Among 345 plant extracts analyzed, 13 showed high levels of antifungal activity, with species of Allium and Capsicum predominating. Among the 49 essential oils tested, palmarosa (Cymbopogon martini), red thyme (Thymus zygis), cinnamon leaf (Cinnamomum zeylanicum), and clove buds (Eugenia caryophyllata) demonstrated the most antifungal activity against B. cinerea. The most frequently occurring constituents in essential oils showing high antifungal activity were: D-limonene, cineole; β-myrcene; α-pinene, β-pinene; and camphor.
Influence of Inoculation Method on Systemic Fusarium moniliforme Infection of Maize Plants Grown from Infected Seeds
Authors: Munkvold G. P. , Carlton W. M.
Published: May 2007

Two greenhouse and two field experiments were conducted in 1994 and 1995 to quantify the incidence of maize kernel infection resulting from systemic infection of maize plants by Fusarium moniliforme. Seeds were infected by two methods: (i) spray-inoculation of maize silks during seed development (field-infected), and (ii) soak-inoculation of mature seeds in a spore suspension (laboratory-infected). Plants were grown from infected seeds and assayed for systemic infection by the seed-inoculated strain, determined by vegetative compatibility of recovered isolates with the original strain. The seed-inoculated strain was recovered from stalks and kernels of plants grown from both types of infected seed. Mature plants grown from field-infected seeds had a higher percentage of their kernels infected with the seed-inoculated strain compared with plants from laboratory-infected seed. Mean incidence of infection by the seed-inoculated strain was 9.9 to 29.4% of all kernels (33.0 to 55.9% of F. moniliforme-infected kernels) in the plants grown from field-infected seed. Some plants from infected seed were subsequently silk-inoculated, and the silk-inoculated strain was recovered from a much higher percentage of kernels (26.5 to 37.5% of all kernels or 77.9 to 78.4% of F. moniliforme-infected kernels) than was the seed-inoculated strain; furthermore, silk inoculation significantly reduced incidence of kernel infection by the seed-inoculated strain. Seed infection by F. moniliforme resulted in systemic infection of plants and kernels. However, local infection (via silks) was a more important pathway to kernels than was systemic infection, and strains infecting the silks competed successfully against those entering the kernels through systemic development.
A Search for Resistance in Lycopersicon spp. to Nacobbus aberrans
Authors: Veremis J. C. , Cap G. B. , Roberts P. A.
Published: May 2007

Accessions of Lycopersicon cheesmanii, L. chmielewskii, L. esculentum var. cerasiforme, L.hirsutum, L. parviflorum, L. peruvianum, L. pennellii, L. pimpinellifolium, and three interspecific hybrids of L. peruvianum with L. esculentum, were screened for resistance to the false root-knot nematode (Nacobbus aberrans) in greenhouse tests. Variability in nematode reproduction levels was observed within L. chmielewskii accessions LA 2695 and LA 2663 in initial tests with N. aberrans from Argentina; however, interspecific hybrids of L. esculentum cv. UC-82 × L. chmielewskii LA 2695, L. esculentum cv. UC-82 × L. chmielewskii LA 2663, and all the parent plants were susceptible in subsequent tests to the isolate of N. aberrans from Argentina and to an isolate from Mexico. The interspecific hybrids that possess the gene Mi and additional novel resistance to Meloidogyne spp. (root-knot nematodes) and all other exotic tomato accessions tested were susceptible to N. aberrans in our tests. Thus, we have been unable to identify or confirm resistance to two N. aberrans isolates in a range of Lycopersicon germ plasm accessions, including those that possess genes for resistance to root-knot nematodes.
Improved RNA Extraction from Woody Plants for the Detection of Viral Pathogens by Reverse Transcription-Polymerase Chain Reaction
Authors: MacKenzie Donald J. , McLean Morven A. , Mukerji Srima , Green Margaret
Published: May 2007

An efficient procedure for the extraction of high-quality RNA from woody plants without the use of phenol, organic solvents, or alcohol precipitation is described. The method employs commercially available spin-column matrices and mitigates the inhibitory effects of plant polysaccharides and polyphenolic compounds commonly observed on subsequent polymerase chain reaction amplification when conventional extraction methods are applied to woody plant species. The method described has been successfully used in the development of highly sensitive reverse transcription-polymerase chain reaction (RT-PCR) techniques for the detection of a number of viruses in their woody hosts. The viruses detected included apple stem grooving capillovirus (ASGV), apple stem pitting virus, Prunus necrotic ringspot ilarvirus (PNRSV), grapevine fanleaf and Arabis mosaic nepoviruses, and grapevine leafroll-associated closterovirus type 3. The method described was equally effective for the extraction of viral RNA from either budwood, leaves, or flower blossoms as determined by the equivalent RT-PCR detection of ASGV and PNRSV from these tissues. Detection of viral RNA in samples of total plant RNA prepared using this method was found to be as sensitive as was previously described for the immunocapture RT-PCR technique.