bluuebunny/crossref_metadata_2025 huggingface dataset:
Pathogenicity and Pyrenocine Production of Curvularia inaequalis Isolated from Zoysia Grass
Authors: Kim Jin-Cheol , Choi Gyung Ja , Kim Heung Tae , Kim Hyun-Ju , Cho Kwang Yun
Published: May 2007

Five isolates of Curvularia inaequalis were obtained from blighted leaves of zoysia grass. The optimal growth temperature of the pathogen was 30°C and all isolates caused foliar blighting symptoms on zoysia grass, bent grass, and bermuda grass. Phytotoxic substances were associated with pathogenicity. Two phytotoxins were isolated from liquid cultures of C. inaequalis by ethyl acetate extraction and repeated silica gel column chromatography. On the basis of mass and nuclear magnetic resonance spectral analyses, the compounds were identified as pyrenocines A and B, phytotoxins produced by Pyrenochaeta terrestris. Pyrenocine A caused leaf necrosis in a leaf-wounding bioassay and inhibited growth of all plants tested in a whole plant test. Large crab grass and fall panicum were most susceptible to pyrenocine A. Pyrenocines A and B also caused significant electrolyte leakage from leaf tissues of bermuda grass. Pyrenocine B exhibited much weaker phytotoxic activity than pyrenocine A in all bioassays performed. Both compounds caused leaf tip dieback symptoms in turf grass plants similar to symptoms observed in the field. Thus, pyrenocines A and B are thought to be involved in the development of Curvularia blight disease of turfgrasses caused by C. inaequalis.
First Report of Colletotrichum acutatum on Strawberry in Northwestern Argentina
Authors: Ramallo C. J. , Ploper L. D. , Ontivero M. , Filippone M. P. , Castagnaro A. , Ricci J. Díaz
Published: May 2007

Isolates were obtained from strawberry tissue with anthracnose symptoms from several locations near Tucumán, Argentina. Isolates were characterized using several criteria. Isolates produced fusiform conidia, tapered to a point at both ends, and averaged 13.5 × 4.9 μm. On potato dextrose agar, colonies produced a white cottony mycelial colony that turned orange in older cultures. Compared with Colletotrichum fragariae, the new isolates produced fewer appressoria. Pathogenicity tests were conducted on detached leaves and plants in the greenhouse and field. Detached immature leaves of cvs. Chandler, Fern, and Sweet Charlie were inoculated with a 20-μl droplet of an aqueous conidial suspension (106 conidia per ml) placed on the adaxial surface. Control leaves were inoculated with sterile distilled water. Leaves were maintained under white light (2,000 lux, 12 h/day) at 26°C, and 100% relative humidity. Necrotic spots were visible 4 days after inoculation. Greenhouse and field plants were spray-inoculated and covered for 48 h. Disease symptoms were mainly observed on petioles and runners 9 days after inoculation. No lesions were observed on control detached leaves or plants. Koch's postulates were confirmed in all cases. Based on morphological and cultural characteristics, isolates were identified as C. acutatum Simmonds (1). This is the first report of C. acutatum causing strawberry anthracnose in northwestern Argentina.

Reference: (1) B. Smith and L. L. Black. Plant Dis. 74:69, 1990.
Dothistroma Needle Blight, Caused by Dothistroma septospora, of Pinus spp. in Vermont
Authors: Pfister S. E. , Halik S. , Bergdahl D. R.
Published: May 2007

Dothistroma needle blight, caused by Dothistroma septospora (teleo-morph Mycosphaerella pini), is a serious foliage disease of pine species throughout the world. In the northeastern United States, the fungus has been reported from Pennsylvania, but not New York, New Jersey, or any of the New England states. It has been reported from the eastern provinces of Canada (Newfoundland, Quebec). During 1994 to 1998, stromatic conidomata consistent with descriptions of D. septospora were associated with needle blight symptoms on mature landscape pines at four locations (Jericho, Montpelier, Williamstown, Williston) and one Christmas tree farm (Barre) in Vermont. Pinus nigra was affected at four locations; P. mugo and P. ponderosa were affected at one location each. Severe foliar blight and defoliation occurred during successive years on P. nigra and P. mugo. Collections from each location and host were examined microscopically. Mean lengths and widths of 20 or more conidia from each of three collections of P. nigra (Barre, Montpelier, and Williston) were 2.3 × 25, 2.7 × 20, and 2.6 × 24 μm, respectively. Corresponding values for collections from P. mugo and P. ponderosa were 2.4 × 26 and 3.6 × 31 μm, respectively. All collections conformed to descriptions and illustrations of D. septospora (1). No ascigerous state was observed from 1994 to 1998. This is the first report of D. septospora in New England.

Reference: (1) H. C. Evans. 1984. The Genus Mycosphaerella and Its Anamorphs Cercoseptoria, Dothistroma and Lecanosticta on Pines. Commonwealth Mycological Institute, Kew, England.
First Detection of Faba bean necrotic yellow virus in Spain
Authors: Babin M. , Ortíz V. , Castro S. , Romero J.
Published: May 2007

Faba bean necrotic yellow virus (FBNYV) was not detected during 1994 to 1996 field surveys of faba beans (Vicia faba L.) in Spain (1). In 1997, however, one sample with symptoms of necrosis, collected in Baleares, was tested using ELISA (enzyme-linked immunosorbent assay) and was positive for both Tomato spotted wilt virus (TSWV) and FBNYV. FBNYV is a single-strand DNA virus that is transmitted by aphids and is the main virus disease of broad bean in North Africa and West Asia (2). During 1997 to 1999, faba bean plants with symptoms of necrosis, yellowing, small leaves, and stunting were collected from several fields in the Murcia Region (Spain) and were analyzed using ELISA. To detect FBNYV, we used monoclonal 2E9 supplied by H. J. Vetten (Institute of Plant Virology, Microbiology and Biosafety, BBA, Braunschweig, Germany). Of 700 samples analyzed, 34 were positive for FBNYV. Of the 34 positive samples, 12 tested positive, using commercial antiserum from Loewe, Inc. (Munich) for mixed infections with TSWV. FBNYV was transmitted to healthy faba bean plants by aphids (Acyrthosiphon pisum) in greenhouse experiments and was confirmed by ELISA. Preliminary epidemiological data showed a gradual increase in the number of plants infected with time in the same field. Aphid transmission of FBNYV to faba beans has established the disease in Spain and is a potential threat to other leguminous crops. This is the first report of a nanovirus in Europe.

References: (1) J. Fresno et al. Plant Dis. 81:112, 1997. (2) L. Katul et al. Ann. Appl. Biol. 123:629, 1993.
Petunia vein banding virus: Characterization of a New Tymovirus from Petunia × hybrida
Authors: Alexandre M. A. V. , Duarte L. M. L. , Rivas E. B. , Chagas C. M. , Barradas M. M. , Koenig R.
Published: May 2007

Petunia plants from a nursery in the State of Rio Grande do Sul, Brazil, showed pronounced vein banding and contained isometric particles with diameters of approximately 45 and 30 nm. The larger ones apparently represent a caulimovirus, while the smaller ones, which included both empty shells and full particles, were identified as those of a new tymovirus for which we propose the name Petunia vein banding virus (PetVBV). Originally, PetVBV was transmitted only with difficulty to healthy petunia plants. However, from an experimentally infected petu-nia, it was later readily transmitted also to Nicotiana benthamiana and Nicandra physalodes, but not to other species in the Solanaceae or other plant families. It produces cytopathic effects typical for tymovirus infections. Its coat protein shows approximately 65% amino acid sequence identity with those of Eggplant mosaic and Andean potato latent viruses, to which it is also serologically more closely related than to any other tymoviruses.
Reduced Sampling Frequency for Evaluating Fungicide Efficacy on Botrytis Fruit Rot of Strawberry
Authors: Legard D. E. , Martin F. G. , Xiao C. L. , Chandler C. K.
Published: May 2007

Evaluating fungicide efficacy in annual strawberry production systems can be labor intensive due to continuous harvesting over a relatively long season. The effect of reduced harvest number on the accuracy of least significant difference (LSD) separations for Botrytis fruit rot (Botrytis cinerea) incidence and marketable yield in fungicide efficacy studies was evaluated over three seasons. Fruit were harvested and graded twice a week for a total of 23 to 32 harvests each season. Data from each season were divided into different sample sets. Data from three different harvest periods (early, late, and whole season) and different harvesting frequencies (twice weekly, once weekly, every second, third, or fourth week) were compared with the complete data set (twice weekly for the whole season). Spearman's rank correlation and Pearson's product moment correlation coefficients were used to evaluate the correlation of the complete data sets with data sets from other sampling plans. Harvesting once a week for either the late- or whole-season periods accurately estimated LSD groupings for Botrytis fruit rot incidence among fungicide treatments. The precision of marketable yield estimates using once-a-week harvesting for the late or whole-season periods were relatively lower than for the incidence of Botrytis.
Preliminary Characterization of Fusarium oxysporum f. sp. gladioli Causing Fusarium Corm Rot of Saffron in Italy
Authors: Di Primo P. , Cappelli C.
Published: May 2007

Fusarium corm rot of saffron (Crocus sativus L.), incited by Fusarium oxysporum Schlecht. f. sp. gladioli, causes severe stigma yield losses in L'Aquila Province in Central Italy. Primary symptoms during flowering (October through November) include basal stem rot, yellowing and wilting of shoots, and corm rot. The rapid spread of the disease is apparently caused only by movement of contaminated and/or infected corms (2,3). Ten isolates of F. oxysporum f. sp. gladioli, obtained from infected saffron crops located in the principal areas of saffron production in L'Aquila Province (2,3), were characterized by vegetative compatibility tests. The isolates were placed into vegetative compatibility groups (VCGs) using heterokaryon tests with chlorate-resistant nitrate-nonutilizing (nit) mutants. Based on complementation among these isolates and with a representative isolate of VCG 0340 (4), the tested isolates were assigned to VCG 0340. The fact that all isolates examined in this study belong to a single VCG supports the hypothesis that a clonal population of F. oxysporum f. sp. gladioli is spreading in L'Aquila Province in planting stock. In previous studies, only two Italian isolates of the pathogen obtained from Gladiolus were tested for vegetative compatibility, and both were included in VCG 0343 (1,4). Acquisition of further information on a larger number of isolates obtained from other cropping sites and associated with other hosts may result in a better understanding of the origin and spread of the pathogen in Italy, leading to improved strategies for control of Fusarium corm rot of saffron.

References: (1) R. P. Baayen et al. Eur. J. Plant Pathol. 104:887, 1998. (2) C. Cappelli and G. Di Minco. Infitore Fitopatol. 49:27, 1999. (3) C. Cappelli and G. Di Minco. J. Plant Pathol. 80:253, 1998. (4) J. J. Mes et al. Plant Pathol. 43:362, 1994.
First Report of Natural Infection of Greenhouse-Grown Tomato and Weed Species by Pelargonium zonate spot virus in Spain
Authors: Luis-Arteaga M. , Cambra M. A.
Published: May 2007

Tomato (Lycopersicon esculentum Mill.) plants showing severe chlorotic and necrotic ringspots, line patterns on leaves, and concentric chlorotic ringspots on stems and fruits were observed in plastic greenhouse-grown tomato crops cv. Royesta during the spring of 1996 in Zaragoza province, Northeast Spain. Symptoms were similar to those associated with Pelargonium zonate spot virus (PZSV) infection on tomato in Italy (1,2). The causal agent was mechanically transmitted from leaf, fruit, and stem samples to several indicator species. The following host reactions were recorded: chlorotic local lesions on Chenopodium amaranticolor, C. quinoa, Cucumis sativus, and Cucurbita pepo, and systemic reactions, sometimes associated with localized reactions, on Capsicum annuum ‘Doux des Landes’ and ‘Yolo Wonder’, Datura stramonium, Gomphrena globosa, Nicotiana clevelandii, N. glutinosa, N. megalosiphon, N. rustica, N. sylvestris, N. tabacum ‘Paraguay’, ‘Samsun’, and ‘Xanthi nc’, Ocimum basilicum, Petunia hybrida, Physalis floridana, Solanum melongena, and Vigna unguiculata. Symptoms obtained in indicator species were erratic. During the spring of 1999, naturally occurring symptoms appeared again on tomato plants, cultivars Royesta and Bond, growing in greenhouses in the same area. Positive serological reactions with the enzyme-linked immunosorbent assay (ELISA) using a commercial PZSV antiserum (Agdia Inc.), developed against an Italian isolate of PZSV, were obtained with extracts from leaves, stems, and fruits of tomato plants naturally infected (1999) and from systemically infected indicator species mechanically inoculated with sap from tomato samples (1996 and 1999). Serological results were confirmed by molecular hybridization analysis using a PZSV-specific riboprobe (D. Gallitelli, personal communication). Some of the weeds growing around the greenhouses (Capsella bursa-pastoris, Diplotaxis erucoides, Picris echioides, and Sonchus oleraceus) also tested positive for PZSV (A405nm values greater than three times that of healthy plants). However, other weed species such as Anacyclus tomentosus, Beta maritima, Cardaria draba, Malva sylvestris, Medicago sp., Polygonum aviculare, Rumex sp., and Sisymbrium irio tested negative, while results from tests on Borago officinalis, Bromus rigidus, and Convolvulus arvensis were inconclusive. Symptoms like those of naturally infected tomato plants were reproduced by mechanically inoculating tomato seedlings with sap from PZSV-infected tobacco (Nicotiana glutinosa and N. tabacum ‘Paraguay’) or from Physalis floridana plants.

References: (1) D. Gallitelli. Ann. Appl. Biol. 100:457, 1982. (2) C. Vovlas et al. Inform. Fitopatol. 2:39, 1986.
First Report of Psittacanthus angustifolius on Pines in Mexico and Guatemala
Authors: Mathiasen R. , Parks C. , Beatty J. , Sesnie S.
Published: May 2007

The mistletoe Psittacanthus angustifolius Kuijt (Loranthaceae) is a common parasite of pines in Honduras (2). In March we observed this mistletoe parasitizing a pine that Farjon and Styles (1) have classified as Pinus tecunumanii Eguiluz & J. P. Perry 4 km south of Jitotol, Chiapas, Mexico. The taxonomy of this host in Chiapas is controversial as Perry (3) classifies the Chiapas populations of this pine as Pinus oocarpa var. ochoterenai Martinez. We also observed P. angustifolius on P. oocarpa Schiede 4 km north of Jitotol. In addition, we found this mistletoe parasitizing Pinus maximinoi H. E. Moore approximately 15 km west of Ocosingo, Chiapas. In Guatemala, we observed P. angustifolius on P. oocarpa at several locations north and south of La Cumbre, Department Baja Verapaz. This mistletoe appears to be less common in Chiapas and Guatemala than it is in Honduras. We did not observe this mistletoe damaging its pine hosts in Mexico or Guatemala. This is the first report of P. angustifolius in both Mexico and Guatemala and the first report of this mistletoe on Pinus tecunumanii (or Pinus oocarpa var. ochoterenai). Specimens of P. angustifolius from the above pine hosts have been deposited at the Deaver Herbarium, Northern Arizona University, Flagstaff.

References: (1) A. Farjon and B. Styles. Pinus (Pinaceae), Flora Neotropica, Monogr. 75, New York Botanical Garden, 1997. (2) Mathiasen et al. Plant Dis. 84:203, 2000. (3) J. Perry. The Pines of Mexico and Central America, Timber Press, Portland, Oregon, 1991
Identification of a New, Monopartite Begomovirus Associated with Leaf Curl Disease of Cotton in Gezira, Sudan
Authors: Idris A. M. , Brown J. K.
Published: May 2007

Cotton leaf curl disease (CLCuD) was first reported in Sudan in 1931. Disease symptoms in cotton were characterized by vein thickening and leaf curling, and the suspect causal agent was shown to be transmitted by the whitefly Bemisia tabaci (Genn.) among cotton, okra, and several weed species (2). Although begomovirus etiology was suspected based on symptomatology and vector transmission, no evidence was available that confirmed or disputed this hypothesis. During 1994 to 1996, four cotton samples exhibiting typical CLCuD symptoms were collected from different fields in the Gezira region in Central Sudan and examined for presence of begomovirus DNA. Total nucleic acids were isolated from cotton plants and subjected to polymerase chain reaction (PCR) using degenerate primers (pAV 2644 and pAC 1154) to amplify begomovirus coat protein (Cp) gene and its flanking sequences (1). An amplicon of the expected size (1,300 bp) was obtained by PCR from each sample, and their nucleotide (nt) sequences were determined. Virus-specific primers designed around the Cp sequence were used to amplify an apparent full-length DNA component. Amplicons were cloned and their sequences were determined, yielding a begomoviral component of approximately 2,761 nt (AF260241). Despite exhaustive attempts to amplify a putative viral B-component using degenerate primers based on the intergenic region sequence of the putative “A-component,” or sequences that are highly conserved for other begomoviruses, no B component was detected. The four cotton isolates shared 99.9 to 100% nt sequence identity, and the number and arrangement of predicted open reading frames were similar to those known for other monopartite begomoviruses. Phylogenetic analysis of the putative CLCuV genome with other begomoviruses indicated that its closest relative was Althea rosea enation virus (AREV) from Egypt (AF014881) with which it shares 79% sequence identity, indicating that CLCuV is a unique begomovirus species with a probable origin in the Eastern Hemisphere. CLCuV shared 66% identity with its second closest relative, Cotton leaf curl virus-Pakistan (CLCuV-PK) (AJ002448). These data provide the first direct evidence for the association of a monopartite begomovirus with the leaf curl disease of cotton in Gezira, Sudan, that is distinct from all other begomoviral species described to date. Herein, we provisionally designate this unique begomoviral species as Cotton leaf curl virus from Sudan (CLCuV-SD).

References: (1) A. M. Idris and J. K. Brown. Phytopathology 88:648, 1998. (2) A. M. Nour and J. J. Nour. Emp. Cott. Gr. Rev. 41:27, 1964.
Puccinia sorghi in Sinaloa, Mexico Virulent on Corn with the Rp1-D Gene
Authors: Pataky J. K. , Natti T. A. , Snyder E. B. , Kurowski C. J.
Published: May 2007

Several different Rp genes in corn condition chlorotic fleck resistant reactions to Puccinia sorghi. Rp-resistance has been used successfully for the past 15 years to control common rust on sweet corn in North America. Most, but not all, Rp-resistant sweet corn hybrids carry the Rp1-D gene. In August and September 1999, isolates of P. sorghi were collected from Rp-resistant sweet corn grown in Illinois, Wisconsin, Minnesota, Michigan, and New York. This was the first widespread occurrence in North America of P. sorghi virulent on corn with Rp1-D (2). The origin of this population of P. sorghi with a virulence phenotype new to North America is not known. Since many believe Mexico is the source of common rust inocula for the midwestern United States, it is important to discover if this virulence occurs in Mexico. Forty-one Rp-resistant and nine susceptible sweet corn hybrids were planted 8 December 1999 in a nursery near Los Mochis, Mexico, in the state of Sinalao. Rp-resistant hybrids had been effective against common rust in Los Mochis nurseries prior to 1999. Each hybrid was in a single row of about 30 plants. The Los Mochis nursery also included two replicate rows of sweet corn or field corn inbred lines with one of 17 different single Rp-genes or one of 11 different compound genes for rust resistance (1). Plants were exposed to local populations of P. sorghi. Reactions were rated in March 2000. Sporulating uredinia (susceptible reactions) were abundant on all sweet corn hybrids and on inbreds with Rp1-D. Susceptible reactions also were observed on other inbred lines with Rp-genes except for lines with the single genes: Rp1-E, Rp-G, Rp1-I, Rp1-K, and Rp1-L or lines with the compound rust genes: Rp1-GI, Rp1-G5, Rp1-GDJ, Rp1-GFJ, Rp1-G5JC, Rp1-G5JD, and Rp1-JFC. This pattern of virulence is similar to that of P. sorghi isolates collected in the midwestern United States in 1999. Rp-resistance currently available in most sweet corn hybrids grown in the Midwest will not be effective when this population of P. sorghi spreads from Mexico to the United States. Therefore, other sources of rust resistance need to be incorporated into sweet corn hybrids.

References: (1) S. H. Hulbert, Annu. Rev. Phytopathol. 35:292, 1997. (2) J. K. Pataky and W. F. Tracy. Plant Dis. 83:1177, 1999.
Nicotiana tabacum as an Experimental Host for the Study of Plant-Xylella fastidiosa Interactions
Authors: Lopes S. A. , Ribeiro D. M. , Roberto P. G. , França S. C. , Santos J. M.
Published: May 2007

Xylella fastidiosa causes citrus variegated chlorosis (CVC). Information generated from the X. fastidiosa genome project is being used to study the underlying mechanisms responsible for pathogenicity. However, the lack of an experimental host other than citrus to study plant-X. fastidiosa interaction has been an obstacle to accelerated progress in this area. We present here results of three experiments that demonstrated that tobacco could be an important experimental host for X. fastidiosa. All tobacco plants inoculated with a citrus strain of X. fastidiosa expressed unequivocal symptoms, consisting of orange leaf lesions, approximately 2 months after injection of the pathogen. CVC symptoms were observed in citrus 3 to 6 months after inoculation. The pathogen was readily detected in symptomatic tobacco plants by polymerase chain reaction (PCR) and phase contrast microscopy. In addition, X. fastidiosa was reisolated on agar plates in 4 of 10 plants. Scanning electron microscopy analysis of cross sections of stems and petioles revealed the presence of rod shaped bacteria restricted to the xylem of inoculated plants. The cell size was within the limit typical of X. fastidiosa.
Development of Monoclonal Antibodies Reactive to a New Grapevine Leafroll-Associated Closterovirus
Authors: Monis Judit
Published: May 2007

Monoclonal antibodies reactive to a previously uncharacterized grapevine leafroll-associated virus (GLRaV) coat protein were developed. A novel 37-kDa protein was found associated with grapevine leafroll disease in a mixed virus infection. The polypeptide was separated from the 38-kDa polypeptide associated with GLRaV-1 using a Tricine sodium dodecyl sulfate-polyacrylamide gel electrophoresis system. Concentrated p37 preparations were used to immunize mice for the production of monoclonal antibodies (MAb). Serum collected from the immunized mice showed reactivity with the 37-kDa polypeptide but no reactivity with the 38-kDa polypeptide associated with GLRaV-1 using the Western blot assay. The polyclonal antiserum reacted to both native and heat-denatured virus preparations. Two sets of anti-p37 MAbs were developed. One set binds p37 and also cross reacts with other GLRaV proteins, such as p36 of GLRaV-4 and -5, while the second set recognizes p37 specifically. We obtained the partial nucleotide sequence of the putative p37 viral protein. The predicted amino acid sequence revealed the presence of three out of the five conserved amino acids present in closterovirus capsid and diverged duplicate capsid proteins. We propose the name grapevine leafroll-associated virus-8 for the new virus with a 37-kDa capsid protein.
New Source of Resistance to Cucumber mosaic virus in Capsicum frutescens
Authors: Grube Rebecca C. , Zhang Yiping , Murphy John F. , Loaiza-Figueroa Fernando , Lackney Vincent K. , Provvidenti Rosario , Jahn Molly K.
Published: May 2007

A small-fruited pungent pepper accession, Capsicum frutescens ‘BG2814-6’, is resistant to several isolates of Cucumber mosaic virus (CMV). Resistance in BG2814-6 is incompletely penetrant and is controlled by at least two major recessive genes. The accession BG2814-6 and C. annuum ‘Perennial’, the leading source of CMV tolerance, appear to share one or more CMV resistance genes. CMV was detected in uninoculated leaves in a small percentage of both BG2814-6 and Perennial plants, indicating that resistance is not absolute in either genotype. Enzyme-linked immunosorbent assay absorbance values of samples taken from inoculated leaves corresponded well with visible viral symptoms for parental genotypes. While Perennial plants accumulated CMV antigen in inoculated leaves, CMV antigen was not detected in inoculated leaves of 73% of BG2814-6 plants, suggesting that there may be a mechanistic difference in resistance between the two genotypes.
Assessments of Fusarium Head Blight of Wheat and Barley in Response to Fungicide Treatment
Authors: Jones R. K.
Published: May 2007

Benomyl and tebuconazole reduced head blight incidence, head blight severity, and the percentage of visually scabby kernels (VSK) in harvested grain when applied to the susceptible spring wheat cv. Norm at anthesis. Deoxynivalenol (DON) concentration was also reduced. Fungicide treatment increased head weight, test weight, thousand kernel weight, and yield. Fludioxonil reduced certain parameters associated with the disease in barley, including incidence, severity, and deoxynivalenol concentration, while increasing the percentage of plump kernels and yield. In vitro, isolates of Fusarium graminearum were sensitive to fludioxonil, benomyl, tebuconazole, and mancozeb (concentrations that give 50% growth inhibition of 7.4 × 10-3, 3.5 × 10-1,9.9 × 10-1, and 7.3 mg a.i./liter, respectively). No evidence for insensitivity (resistance) was found. Prospects for chemical control of Fusarium head blight (FHB), however, remain limited. The repeatability of assessment methods used in evaluating host response to fungicides and to the damage caused by F. graminearum is discussed. Disease incidence, disease severity, VSK, and DON were identified as key variables that best measure the effects of FHB.
First Report of Tomato yellow leaf curl virus-Is (TYLCV-Is) in the Canary Islands
Authors: Font I. , Martínez-Culebras P. , Jordá C.
Published: May 2007

In autumn of 1999 and winter-spring 2000, tomato (Lycopersicon) crops grown in the Regions of Las Palmas de Gran Canaria and Tenerife (Canary Islands) showed upward curling of leaves, yellowing of leaf margins, crumpling of new leaves, reduction of leaflet area, and stunting of shoots. These symptoms were similar to those described for tomato yellow leaf curl disease. Symptomatic samples were collected from Las Palmas de Gran Canaria (33 samples) and Tenerife (45 samples) for polymerase chain reaction (PCR) identification analysis. The degenerate primers pair of Begomovirus (AV494/AC1048) (3) was used to amplify the “core” region of the capsid protein gene. Two tomato plants experimentally infected with Tomato yellow leaf curl virus-Is (TYLCVIs) or TYLCV-Sar served as positive controls. Electrophoretic analysis of all samples showed a single fragment of the expected size (550 bp). To identify the type of TYLCV (TYLCV-Sar or TYLCV-Is), the PCR products were digested by endonucleases (AluI, HaeIII, HpaII, RsaI, Sau3A, TaqI, DdeI, and ScrFI). Twenty-six samples from Las Palmas de Gran Canaria showed the same restriction pattern of TYLCV-Sar, and seven samples from Las Palmas de Gran Canaria and all 45 samples from Tenerife showed the same restriction pattern of TYLCV-Is. These results confirm that TYLCV-Sar and TYLCV-Is are present in Las Palmas de Gran Canaria and TYLCV-Is is present in Tenerife. The presence of TYLCV-Is in Morocco (2) and TYLCV-Sar in the Canary Islands and Morocco has been recently described (1). However, this is the first report of TYLCV-Is in the Canary Islands.

References: (1) F. Monci et al. Plant Dis. 84:490, 2000. (2) M. Peterschmitt et al. Plant Dis. 83:1074, 1999. (3) S. D. Wyatt et al. Phytopathology 86:1288, 1996.
First Report of Powdery Mildew Caused by Podosphaera (Sphaerotheca) fusca on Euryops pectinatus in North America
Authors: Saenz G. S. , Koike S. T. , Shishkoff N.
Published: May 2007

Gray-leaved Euryops (Euryops pectinatus Cass., Asteraceae) is an evergreen shrub that is widely planted in landscapes in the United States. In the fall of 1999, powdery mildew was observed on E. pectinatus planted in landscapes in Redlands (San Bernardino County), CA. Symptoms consisted only of slight cupping of leaves. Fungal growth was observed on stems, leaves, petioles, and pedicels and was ectophytic and amphigenous. The white mycelium was patchy to effuse. Hyphal appressoria were indistinct (1). Conidiophore foot cells were cylindric and sometimes were tapered toward or constricted at the base. Foot cells measured 30 to 50 by 10 to 12 μm and were followed by one to two shorter cells. Conidia were cylindric to slightly doliform, borne in chains of two to three, and measured 26 to 38 by 14 to 18 μm. Conidial length to width ratios ranged from 1.7 to 2.4. Catenate conidia had crenate edge lines (3). Conidia possessed conspicuous fibrosin bodies and from their sides produced short germ tubes without appressoria. Cleistothecia were not observed. Based on these characters, the fungus was identified as Podosphaera fusca (Fr.) U. Braun & N. Shishkoff (Podosphaera sect. Sphaerotheca) (1,2). Pathogenicity was confirmed by gently pressing diseased leaves onto leaves of healthy E. pectinatus plants. Plants were incubated in a humidity chamber at 22 to 24°C and after 12 to 14 days powdery mildew colonies developed. E. pectinatus cv. Viridis, a cultivar that lacks the extensive pubescence of E. pectinatus, also developed disease when inoculated. This appears to be the first report of powdery mildew on E. pectinatus in North America. A voucher specimen has been deposited into the University of California Herbarium (accession # UC1738635). P. fusca was also observed on cv. Viridis in a nursery in New York in 1999. It is unclear where this pathogen originated. P. fusca parasitizes a large number of asteraceous species including dandelion (Taraxacum officinalis) and sowthistle (Sonchus spp.) weeds, which occur in the area and sometimes are infected with powdery mildew. The Euryops powdery mildew pathogen may be a race that is different than those found on other composites in the United States. The fungus was observed on plants in shaded areas but not on plants in full sun.

References: (1) U. Braun. Nova Hedwigia 89:1, 1987. (2) U. Braun and S. Takamatsu. Schlechtendalia 4:1, 2000. (3) H. D. Shin and Y. J. La. Mycotaxon 46:445, 1993.
In Situ Immunoassay for Detection of Citrus tristeza virus
Authors: Lin Youjian , Rundell Phyllis A. , Xie Lianhui , Powell Charles A.
Published: May 2007

An in situ immunoassay (ISIA) is described for detection of Citrus tristeza virus (CTV). Sections from stems, petioles, or leaf veins of citrus plants that were healthy or infected with CTV were fixed with 70% ethanol and incubated with specific polyclonal antiserum (PCA) 1212 or with monoclonal antibodies (MAbs) MCA13 or 17G11. Bound antibodies were labeled with enzyme-conjugated species-specific secondary antibodies and exposed to a substrate mixture (nitroblue tetrazolium and 5-bromo-4-chloro-3-indolyl phosphate). Presence of CTV antigens was indicated by the development of a purple color, which could be visualized by light microscopy, in the phloem tissues of infected citrus plants. No purple color was observed in the phloem tissues of healthy plants. All isolates used in this study, both severe and mild, were detected by ISIA with the PCA 1212 and the broad spectrum MAb 17G11, but only severe isolates were detected by the strain selective MAb MCA13. Location of CTV antigens could be determined directly and accurately by ISIA in both fresh tissues and samples stored in plastic bags at 4°C or frozen for 4 weeks. Sensitivity of ISIA for detecting CTV in infected plants compared favorably with that of direct tissue blot immunoassay (DTBIA). ISIA is a simple, rapid, specific, and practical procedure for CTV identification applicable to both research and diagnostic needs.
Oospore Germination of Aphanomyces euteiches in Root Exudates and on the Rhizoplanes of Crop Plants
Authors: Shang H. , Grau C. R. , Peters R. D.
Published: May 2007

A technique was developed that allows prolific production, easy collection, and increased germination frequency of single oospores of Aphanomyces euteiches. The influence of root exudates and roots of various plant species, including pea, bean, alfalfa, oat, soybean, corn, and tomato, on germination of A. euteiches oospores also was studied. Compared with a sterile, deionized water control, root exudates from several hosts were only slightly effective in stimulating oospore germination, since only 0 to 11.1% of oospores exposed to various exudates germinated. By contrast, oospores placed directly on plant roots germinated at higher frequencies. Oospores of pea pathotype isolates P30 and P46 germinated at a greater frequency (30.6 to 61.1%) on pea, bean, and oat roots than on roots of any of the other plant species tested. Oospores of bean pathotype isolates GB33 and GB71 had a higher germination frequency (47.2 to 52.8%) on bean roots than on the roots of the other plant species tested. A higher percentage of oospores germinated if placed on lateral roots as opposed to taproots of pea and bean. A higher percentage of oospores of bean pathotype isolates and one pea pathotype isolate germinated on 10-day-old rather than on 20-day-old roots of bean. Therefore, pea and bean roots can be used effectively to germinate oospores of pea and bean isolates of A. euteiches, respectively. This technique will be valuable for studies of sexual reproduction and genetics of A. euteiches.
Size-Selective Sieving for Detecting Teliospores of Tilletia indica in Wheat Seed Samples
Authors: Peterson G. L. , Bonde M. R. , Phillips J. G.
Published: May 2007

A method was developed to isolate teliospores of Tilletia indica from infested grain. The technique was evaluated to determine its sensitivity for detection and quantification of teliospores, the time required to conduct an individual test, and its utility for the detection and identification of the pathogen for phytosanitary regulation and seed certification. A seed wash of a 50-g grain sample was washed through 53-μm and 20-μm pore size nylon screens to remove unwanted debris and to concentrate and isolate teliospores. The material retained in the 20-μm screen was suspended for direct microscopic examination or plated on water agar for teliospore germination and identification by polymerase chain reaction (PCR) utilizing two pairs of T. indica-specific primers. The reliability of detection for both light microscopy and PCR are 100% at an infestation of five teliospores per 50-g sample. The proportion of teliospores recovered from grain samples artificially infested with T. indica was 0, 82, 88, 81, and 82%, respectively, at infestation levels of 0, 1, 2, 5, and 10 teliospores per 50-g wheat sample. Extraction efficiency was comparable to the centrifuge seed-wash method currently used by most seed health laboratories. Sample analysis using size-selective sieving was more than 83% faster than the standard centrifuge seed wash.
Molecular Evidence of the Relationship Between a Virus Associated with Flat Apple Disease and Cherry rasp leaf virus as Determined by RT-PCR
Authors: James D. , Howell W. E. , Mink G. I.
Published: May 2007

Flat apple disease-associated virus (FAV) was mechanically transmitted to the propagation host Chenopodium quinoa and double-stranded (ds)RNA recovered using CFII chromatography. Purified dsRNA was used to generate cDNA clones which were sequenced and the information used to design oligonucleotide primers for reverse transcription-polymerase chain reaction (RT-PCR) and tube capture (TC)/RT-PCR analyses. Oligonucleotide primers for RT-PCR analysis and dot blot hybridization using digoxigenin-labeled cDNA clones were used for the detection of FAV and Cherry rasp leaf virus (CRLV) in C. quinoa, in leaf and bud wood tissue of apple, or both. Primers JQ3D33FF/FR amplified a virus-specific 429-bp fragment and reliably detected all isolates of FAV and CRLV tested by RT-PCR and TC/RT-PCR. Primers JQ2C1FF/FR amplified a 370-bp fragment and detected FAV and some isolates of CRLV. Comparison of amino acid residues derived from the 429-bp fragments of FAV and CRLV gave 95% identity. The RT-PCR assays provided strong evidence of a relationship between FAV and CRLV. These assays were also used to confirm virus elimination in apple plants after heat therapy. Western blot analysis of FAV revealed capsid protein subunits of approximately 22 and 24 kDa. Our data support biological and serological evidence that FAV and CRLV are isolates of the same virus. Searches of the database produced sequence matches only with RNA2 of Apple latent spherical virus (ALSV), a new member of the family Comoviridae. This suggests that both primer pairs presumably target regions on RNA2 of FAV/CRLV and that these viruses may be more closely related to ALSV than to other members of this family.
First Report of Occurrence of Sclerotinia Blight on Petunia in Louisiana
Authors: Holcomb G. E.
Published: May 2007

Petunia × hybrida Wave series cultivars were observed with symptoms of tan to brown stem lesions, wilt, and branch death in a demonstration/trial planting at Burden Research Center in Baton Rouge, LA, during January and February 2000. Disease signs included the presence of white, cottony mycelia on infected stems and the presence of black sclerotia. Seventeen of 131 plants were infected on 20 February and included individuals of cvs. Wave Purple, Wave Rose, Wave Misty Lilac, Wave Pink, Tidal Wave Hot Pink, and Tidal Wave Cherry. Isolations were made by placing diseased stem sections on acidified potato-dextrose agar. A fungus that produced white mycelia and black sclerotia was consistently isolated from infected stems and identified as Sclerotinia sclerotiorum. Pathogenicity tests were done by pipetting 1 to 2 ml of blended mycelia and sclerotia (one plate culture blended in 100 ml distilled water) at the base of flowering-age Wave series plants. Plants were held for 3 days in a dew chamber maintained at 22°C and then moved to a greenhouse held at 25°C. Wilt and branch death developed on inoculated plants after 5 days and S. sclerotiorum was reisolated. Uninoculated plants remained healthy. Wave series cultivars have a prostrate growth habit that is conducive to disease development. No plants in the trial planting were killed and infected plants had recovered by 1 May and had uniformly covered the plant bed. Sclerotinia blight was previously reported on Petunia × hybrida from Bermuda (2) and Florida (1).

References: (1) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN. (2) J. M. Waterston. Dept. Agric. Bermuda Rep., 1947.
Occurrence of a Reovirus Infecting Maize in India
Authors: Lenardon S. L. , Giolitti F. , Welz H. G. , Verma P.
Published: May 2007

During the 1998-99 season, maize plants showing viruslike symptoms were observed at two locations in the Andhra Pradesh state in Southern India. Several hybrids were evaluated at Hyderabad in a replicated yield trial and most were affected, with disease incidence ranging from 4.4 to 61.8% of the plants among plots. Hybrid 4642 (Proagro 3-way hybrid, late maturity) and the pre-commercial hybrid YLY102 were the most susceptible, whereas the popular hybrid 4640 was among the least susceptible entries. In seed production fields near Eluru, incidence ranged from 10 to 15% among plots, with the female parent of hybrid 4210 (Proagro 3-way hybrid, early maturity) being especially affected. Symptoms observed in hybrids varied, presumably, according to the infection time and included severe plant dwarfing, dark-green leaves, enations on the lower leaf surface, and small malformed ears with few or no kernels. Symptomatic and asymptomatic field plants (root and leaf tissues) were tested by ds-RNA polyacrylamide gel electrophoresis and by double-antibody sandwich enzyme linked immunosorbent assay (DAS-ELISA) with antiserum to Mal de río cuarto virus (MRCV), a Reoviridae-Fijivirus member. MRCV and Maize rough dwarf virus (MRDV) were selected as controls because the symptoms were similar to those caused by these maize viruses (1,2). ds-RNA gels from symptomatic plants showed 10 bands with banding patterns different from those of MRCV or MRDV. DAS-ELISA indicated a distant relationship to MRCV. These results provide evidence of a reovirus infection to maize hybrids in India and suggest that a virus belonging to the family Reoviridae, genus Fijivirus is causing this new disease. The high disease incidence and the severity of symptoms should alert breeders and pathologists in southern Asia about potential yield losses.

References: (1) G. Boccardo and R. G. Milne. 1984. Descriptions of Plant Viruses 294. Inst. Hortic. Res., Wellesbourne. (2) C. Marzachi et al. J. Plant Dis. Prot. 106:431–436, 1999.
First Report of Broad bean wilt virus on Thyme (Thymus vulgaris L.)
Authors: Bellardi M. G. , Rubies-Autonell C.
Published: May 2007

In the spring and summer of 1998, a severe virus-like disease consisting of chlorotic mottle on leaves, yellowing, and stunting was observed at the Giardino delle Erbe of Casola-Valsenio (Emila-Romagna region, northern Italy). Most of the symptomatic plants were infected with a filamentous virus that was not identified. Moreover, one thyme plant showing yellow leaves was also found infected by an isometric virus, the identity of which was established by the following host reactions and serological assay. It was mechanically transmitted to 33 species belonging to 11 botanical families. All the Chenopodiaceae (Chenopodium amaranticolor Coste et Reyn., C. murale L., C. foliosum Ash., and C. quinoa Willd.) tested showed local and systemic symptoms in 3 to 4 days; among Leguminosae, broad bean (Vicia faba L.) showed necrotic local lesions and wilt. Virus particles reacted in protein A sandwich-enzyme-linked immunosorbent assay with the antiserum to Broad bean wilt virus (BBWV), serotype I (supplied from the Istituto di Fitovirologia Applicata, CNR, Turin, Italy). BBWV in the field was in all probability transmitted to thyme by aphids from weeds and/or other medicinal and aromatic species cultivated in the same herb garden, all recently shown to be hosts for BBWV: Polygonum fagopyrum L., Hedisarum coronarium L., Borago officinalis L., Phytolacca Americana L., Digitalis lanata Ehrh., and D. purpurea L. (1). This is the first report of BBWV in T. vulgaris and demonstrates that it is more prevalent in Italy than previously reported.

References: (1) C. Rubies-Autonell and M. G. Bellardi. 1999. 7th International Plant Virus Epidemiology Symposium, Aguadulce, Spain.
Detection and Characterization of an Elm Yellows (16SrV) Group Phytoplasma Infecting Virginia Creeper Plants in Southern Florida
Authors: Harrison N. A. , Griffiths H. M. , Carpio M. L. , Richardson P. A..
Published: May 2007

The polymerase chain reaction (PCR) employing phytoplasma-specific ribosomal RNA primer pair P1/P7 consistently amplified a product of expected size (1.8 kb) from 29 of 36 symptom-less Virginia creeper (Parthenocissus quinquefolia) plants growing in southern Florida. Restriction fragment length polymorphism analysis of P1/P7-primed PCR products indicated that most phytoplasmas detected in Virginia creeper were similar to phytoplasmas composing the elm yellows (16SrV) group. This relationship was verified by reamplification of P1/P7 products using an elm yellows (EY) group-specific rRNA primer pair fB1/rULWS1. rDNA products (1,571 bp) were generated by group-specific PCR from 28 phytoplasma-positive plants and 1 negatively testing plant identified by earlier P1/P7-primed PCR. Analysis of 16S rDNA sequences determined the Virginia creeper (VC) phytoplasma to be phylogenetically closest to the European alder yellows (ALY) agent, an established 16SrV-C subgroup strain. However, presence or absence of restriction sites for endonucleases AluI, BfaI, MspI, RsaI, and TaqI in the 16S rRNA and 16-23S rRNA intergenic spacer region of the VC phytoplasma collectively differentiated this strain from ALY and other 16SrV group phytoplasmas. Failure to detect the VC phytoplasma by PCR employing nonribosomal primer pair FD9f/FD9r suggests that this newly characterized agent varies from known European grapevine yellows (flavescence dorée) phyto-plasmas previously classified as 16SrV subgroup C or D strains.
Beneficial Effects of Fungicide Seed Treatments for Soybean Cultivars with Partial Resistance to Phytophthora sojae
Authors: Dorrance A. E. , McClure S. A.
Published: May 2007

Phytophthora sojae is a yield-limiting soybean pathogen in areas where soils remain saturated for long periods of time. P. sojae has been successfully managed with single dominant resistance genes (Rps genes). The proportion of fields with populations of P. sojae capable of causing susceptible interactions with many of the Rps genes has increased in number. The fungicides metalaxyl and mefenoxam have been used both as in-furrow and seed treatments to provide protection against damping-off caused by P. sojae. To determine the plant age when partial resistance and Rps genes are effective against P. sojae, we evaluated a greenhouse assay in which soybean seeds were planted and inoculated with a zoospore suspension to compare the disease reaction of soybean seeds and seedlings. Efficacy of different fungicide rates also was evaluated using the cultivar with partial resistance with this inoculation technique. Seeds and seedlings of a cultivar with high levels of partial resistance were susceptible to infection by P. sojae while those of a cultivar with an Rps gene were resistant. For the cultivar with partial resistance, reductions in percent emergence and the number of damped-off seedlings were significantly higher for plants inoculated at the day of planting compared to inoculations of plants with unifoliates present (5 days after planting). Results also indicate that fungicide seed treatment on cultivars with partial resistance may be beneficial when the environmental conditions that favor P. sojae infections occur prior to soybean emergence. This greenhouse assay appears to be useful in examining overall fungicide efficacy; however, it did not detect consistent and quantifiable differences in rates of seed treatment fungicides.