bluuebunny/crossref_metadata_2025 huggingface dataset:
Cynoglossum officinale, a New Natural Host of Alfalfa mosaic virus
Authors: Bellardi M. G. , Rubies-Autonell C. , Pisi A.
Published: May 2007

Cynoglossum officinale L. (family Boraginaceae), hound's-tongue, is a medicinal plant whose roots are used for their astringent and healing properties and for their sedative, calming, and slightly narcotic effects. This species, originating from Europe where it grows wild in mountainous fields, is cultivated only for its medicinal properties. Epidemiological surveys performed in the Emilia Romagna Region of northern Italy in the spring and autumn of 2001 revealed the presence of virus-like symptoms on C. officinale cultivated in two different locations. In the Botanical Garden of the University of Bologna, the plants showed stunting, interveinal chlorotic spots, midrib necrosis, and scarce or no seed production. In the experimental field of the Agriculture Faculty of Bologna (Imola), the plants exhibited stunting, interveinal chlorotic spots, and reduction of leaf lamina. Mechanical inoculations of sap from symptomatic leaves caused typical symptoms of Alfalfa mosaic virus (AlMV) on Chenopodium amaranticolor Coste & Reyn. (local chlorotic, necrotic lesions and systemic chlorotic vein streaking), Vigna unguicolata (L.) Walp., and Phaseolus vulgaris L. (local necrotic lesions). Using an electron microscope, examination of leaf sap obtained from infected plants stained with uranyl acetate and phosphotungstic acid did not show the presence of elongated virus particles. Serological tests, such as immunoelectron microscopy, gold-labeled decoration, and protein A sandwich indirect enzyme-linked immunosorbent assay using antiserum to AMV (PVAS 92, American Type Culture Collection, Manassas, VA, and AlMV-Vinca minor L., from the DiSTA collection, Bologna, Italy as a control), gave positive reactions, indicating that the virus in question was AlMV. To our knowledge, this is the first report of virus infection on C. officinale, a new natural host of AlMV.
Association of a Monopartite Begomovirus Producing Subgenomic DNA and a Distinct DNA Beta on Croton bonplandianus Showing Yellow Vein Symptoms in Pakistan
Authors: Amin I. , Mansoor S. , Iram S. , Khan M. A. , Hussain M. , Zafar Y. , Bull S. E. , Briddon R. W. , Markham P. G.
Published: May 2007

The recent discovery that monopartite begomoviruses on ageratum and cotton essentially require a DNA satellite called DNA β (2,4) is leading to identification of several other hosts that have similar disease complexes. A weed species (Croton bonplandianus) belonging to the family Euphorbiaceae is one such example. C. bonplandianus is widely distributed on wastelands throughout the Punjab Province in Pakistan. It very often shows yellow vein symptoms indicating infection by a begomovirus. To detect a begomovirus, both symptomatic and asymptomatic plants were collected from several widely separated locations in the Punjab Province. Total DNA was isolated from these samples by the cetyltrimethylammoniumbromide (CTAB) method, resolved in an agarose gel, and blotted on a nylon membrane (2). A full-length clone of DNA A of Cotton leaf curl virus (CLCuV) labeled with 32PdCTP was used as a probe in Southern hybridization (2). The probe detected hybridizing bands only in symptomatic plants, confirming the presence of a begomovirus. In addition to hybridizing bands of the expected sizes, smaller bands were also detected, suggesting the presence of subgenomic molecules derived from DNA A. Universal polymerase chain reaction (PCR) primers for dicot-infecting geminiviruses (1) were used in PCR for amplification of DNA A of the begomovirus associated with the disease. The use of these primers in PCR was expected to result in amplification of full-length DNA A. In addition to a product of the expected size (2.7 to 2.8 kb), another product of approximately 1.4 kb was amplified. The presence of subgenomic DNAs that are derived from DNA A is an indicator of the monopartite nature of begomoviruses, because in bipartite begomoviruses subgenomic DNAs are derived solely from DNA B. The presence of a DNA β, a DNA satellite associated with certain monopartite begomoviruses, was suspected because of symptoms and the possible monopartite nature of the virus. Universal primers for amplification of DNA β (3) were used in PCR for amplification of a putative DNA β. The PCR reaction yielded a product of expected size (≈1.4 kb). A probe from the amplified product was made by the oligolabeling method. The probe detected hybridizing bands in all symptomatic samples collected from three locations, confirming the association of a DNA β with the disease. A duplicate blot when hybridized with a DNA β associated with ageratum yellow vein disease did not hybridize to these samples. These results confirm that yellow vein disease on this weed is associated with a monopartite begomovirus and a distinct DNA β.

References: (1) R. W. Briddon et al. Mol. Biotechnol. 1:202, 1994. (2) R. W. Briddon et al. Virology 285:234, 2001. (3) R. W. Briddon et al. Mol. Biotechnol. In press. (4) K. Saunders et al. Proc. Natl. Acad. Sci. U S A 97:6890, 2000.
Use of Fungicides and Biological Controls in the Suppression of Fusarium Crown and Root Rot of Asparagus Under Greenhouse and Growth Chamber Conditions
Authors: Reid T. C. , Hausbeck M. K. , Kizilkaya K.
Published: May 2007

Growth chamber, greenhouse, and field experiments were conducted with fungicides and biological control agents, including nonpathogenic isolates of Fusarium oxysporum, to test their ability to control disease caused by F. oxysporum f. sp. asparagi and F. proliferatum. In greenhouse studies with asparagus seedlings in soil, Trichoderma harzianum strain T-22, benomyl, and fludioxonil treatments increased root weight and decreased root disease compared with the infested control when a low level of F. oxysporum f. sp. asparagi and F. proliferatum was used. The fungicide fludioxonil limited plant death caused by Fusarium spp. at high inoculum levels, whereas T. harzianum strain T-22 was not effective. Nonpathogenic isolates of F. oxysporum were effective in limiting Fusarium disease on asparagus seedlings in culture tubes, although isolates differed in their ability to control disease caused by F. oxysporum f. sp. asparagi and F. proliferatum. In greenhouse studies, no significant differences in plant death were found between asparagus plants growing in media infested with F. oxysporum f. sp. asparagi and F. proliferatum and left untreated, and those treated with nonpathogenic F. oxysporum. The efficacy of fungicides and biological control products to control Fusarium crown and root rot under commercial field conditions could not be evaluated due to low disease pressure.
Quantification of the Toxicity of Aqueous Chlorine to Spores of Penicillium digitatum and Geotrichum citri-aurantii
Authors: Smilanick J. L. , Aiyabei J. , Gabler F. Mlikota , Doctor J. , Sorenson D. , Mackey B.
Published: May 2007

Chlorine toxicity to Penicillium digitatum and Geotrichum citri-aurantii, causes of green mold and sour rot of citrus, respectively, was quantified. In 3% wt/vol NaHCO3 containing 200 µg free chlorine per ml at pH 8.3, 95% of P. digitatum spores died (LT95) by 180 s at 5°C, while only 32 s were required at 24°C. The LT95 of G. citri-aurantii arthrospores was 108 and 31 s at 5 and 24°C, respectively. Mortality slowed 2- to 4-fold for each unit of increase from pH 7 to 10. The LT95 of P. digitatum spores in 200 µg free chlorine per ml at 24°C at pH 7, 8, 9, and 10 was 13.2, 19.1, 29.4, and 88.4 s, respectively. The LT95 of G. citri-aurantii at pH 7, 8, 9, and 10 was 3.0, 12.6, 56.6, and 114 s, respectively. Models were prepared describing mortality. Brief immersion in 200 µg free chlorine per ml reduced viable spores of P. digitatum and G. citri-aurantii from 106 to 103 spores per lemon, and naturally occurring yeast and molds from 106 to 104 CFU. In fruit wound-inoculated and immersed 24 h later in water, 4,000 µg free chlorine per ml, or 3% wt/vol NaHCO3, green mold occurrence after storage was 98.5, 68.3 and 7.5%, respectively.
Effects of Rootstock and Budding Height on Bacterial Canker in French Prune
Authors: Sayler R. J. , Southwick S. M. , Yeager J. T. , Glozer K. , Little E. L. , Kirkpatrick B. C.
Published: May 2007

Bacterial canker is one of the most economically important diseases of stone fruit trees, including ‘French’ prune (Prunus domestica). Field trials were conducted to evaluate the effect of rootstock selection and budding height on the incidence and severity of bacterial canker in four orchards with low to high disease pressure. Treatments included French prune scions low-grafted on ‘Lovell’ peach (Prunus persica) rootstocks as well as Myrobalan 29C (Prunus cerasifera) plum rootstocks grafted at 15, 50, and 90 cm above the rootstock crown. Another treatment consisted of growing Myrobalan 29C plum rootstocks in the field for one growing season, then field-grafting French prune buds onto rootstock scaffolds. Lovell peach rootstock provided the greatest protection from bacterial canker as measured by disease incidence and tree mortality in all orchards. Field-budded rootstocks and rootstocks grafted at the highest budding height provided moderate levels of resistance to bacterial canker. These treatments reduced the incidence but not the severity of disease.
A Model for Probabilistic Assessment of Phytosanitary Risk Reduction Measures
Authors: Powell Mark R.
Published: May 2007

Ideally, a phytosanitary performance standard would be defined as a probabilistic tolerance. For treatments such as solid wood pasteurization, this could be operationalized by stating with a specific degree of confidence that the treatment failure rate for a sentinel pest should be less than a defined level (e.g., X% confidence that the wood heat treatment failure rate for pest Y does not exceed Z%). This article illustrates a probabilistic approach to developing a phytosanitary performance standard, using heat treatment of the wood-inhabiting fungus Postia placenta as an example. The uncertainty about the proportion of wood blocks in which P. placenta survives after treatment is characterized by the Beta distribution, subject to the biological constraint that survival should decrease monotonically with increased time and temperature. Monte Carlo simulation techniques are then used to generate a probabilistic response surface relating proportion survival to treatment time and temperature. This modeling approach relaxes the parametric assumptions associated with traditional statistical methods for fitting response surfaces and is more flexible than conventional methods, resulting in a better fit to the observed data.
First Report of Dry Bean Anthracnose (Colletotrichum lindemuthianum) Race 73 in North Dakota
Authors: del Río L. E. , Lamppa R. S. , Gross P. L.
Published: May 2007

Dry bean (Phaseolus vulgaris L. cv. Pintoba) plants showing typical anthracnose symptoms were observed in three commercial fields in North Dakota (Towner, Steele, and Pembina counties) in July 2001. Disease incidence in all fields ranged from 5 to 20%. The fungus was isolated from leaves and pods on potato dextrose agar and identified as Colletotrichum lindemuthianum (Sacc. & Magnus) Lams.-Scrib. (3). Pathogenicity and race identification were determined on a set of 12 standard differentials (2). Three isolates, one from each county, were grown for 7 days in Mathur's medium. Spores were suspended in water and Tween 80 (0.1% vol/vol) and adjusted to 106 spores per ml. Thirty 2-week-old seedlings of each differential were inoculated with each isolate on the adaxial side of the primary leaves using a Paasche airbrush. Inoculated plants were incubated in moist chambers for 5 days at 20°C under 14 h of fluorescent light and then moved back to the greenhouse. Disease reaction was assessed 3 days later. Isolates of C. lindemuthianum races 7 and 73 obtained from J. Kelly (Michigan State University) were used as positive controls. Inoculations were repeated once. All three North Dakota isolates and the positive control for race 73 produced sporulating lesions on the differentials ‘Michelite’, ‘Cornell 49242’, and ‘Mexico 222’. No lesions were observed in the other differentials. An unidentified anthracnose race retrieved from a single plant in 1982 constitutes the first report of the presence of anthracnose in North Dakota (4). In 1992, Michigan breeding materials infected with race 73 were planted in North Dakota (1); upon detection, the infected plants were destroyed and the fields quarantined. The epidemics observed in the 2001 season, developed in sites distant from the places where the Michigan materials were planted and have been associated with a single seed source. To our knowledge, the presence of anthracnose race 73 reported here constitutes the first report of anthracnose in commercial dry bean fields in North Dakota.

References: (1) J. D. Kelly et al. Plant Dis. 78:892, 1994. (2) M. A. Pastor-Corrales. Phytopathology 81:694, 1991. (3) B. C. Sutton, The Coelomycetes, CAB International, Wallingford, Oxon, UK, 1980. (4) J. R. Venette and P. A. Donald. Bean Improv. Coop. 26:24, 1983.
Occurrence and Etiology of Brown Apical Necrosis on Persian (English) Walnut Fruit
Authors: Belisario A. , Maccaroni M. , Corazza L. , Balmas V. , Valier A.
Published: May 2007

In 1998, a severe fruit drop was observed in Italy, principally on cv. Lara Persian (English) walnut (Juglans regia). Dropped fruit showed a brown patch at the blossom end and blackening and rot of inner tissues. The disease, called brown apical necrosis (BAN), was investigated on fruit collected in Italy and France in 1999. In 2000, studies were carried out in three walnut orchards located in Italy and in France to substantiate the etiology of BAN. Isolations performed from inner diseased fruit tissues yielded several fungi, in decreasing frequency of isolation: species of Fusarium and Alternaria, and one species each of Cladosporium, Colletotrichum, and Phomopsis. However, only Fusarium spp. were recovered from stigmas of BAN-affected fruit. The fungi associated with BAN-diseased fruit and species composition differed among locations and over time, confirming results obtained in previous investigations. The species of Fusarium used in pathogenicity tests reproduced BAN-disease symptoms when inoculated on fruit, whereas an Alternaria alternata isolate caused only limited necrosis of the style. However, the role of the other fungi commonly isolated from BAN-diseased fruit remains to be defined. The walnut blight pathogen, Xanthomonas arboricola pv. juglandis, occasionally was isolated from BAN-diseased fruit. No correlation was found between the extent of external brown patches and the size of inner lesions. Repeated isolations from and inoculations of fruit demonstrated that BAN can be considered a complex disease, and the inner infections originate from the style of the fruit.
Vegetative Compatibility Groups of Fusarium oxysporum f. sp. cepae from Onion in Colorado
Authors: Swift C. E. , Wickliffe E. R. , Schwartz H. F.
Published: May 2007

Nineteen isolates of Fusarium oxysporum f. sp. cepae recovered from diseased onions growing in the western, southern, and northern regions of Colorado were placed into vegetative compatibility groups (VCGs) based on pairing of complementary mutants. Pathogenic isolates from these regions were cultured on variations of potassium chlorate (1.5 or 3.0%) mutation media, potato dextrose agar (PDA), and minimal medium (MM) supplemented with L-asparagine and L-threonine. Chlorate PDA and 3% chlorate MM with L-threonine did not generate the nitrate nonutilizing (nit) mutants required, while MM with L-asparagine (1.5 and 3% chlorate) and MM with L-threonine (1.5% chlorate) generated complementary nit mutants required for compatibility pairings. Five VCGs of F. oxysporum cepae were identified. One VCG was present in all three regions of Colorado examined. Four VCGs were restricted to either western or eastern Colorado. Additional sampling and evaluation of a more diverse collection of F. oxysporum cepae isolates from other regions of onion production is needed to determine the diversity of this pathogen. Such information could assist in breeding for resistance to F. oxysporum cepae.
Characterization of Biofilm Formation by Xylella fastidiosa In Vitro
Authors: Marques L. L. R. , Ceri H. , Manfio G. P. , Reid D. M. , Olson M. E.
Published: May 2007

Xylella fastidiosa colonizes the xylem of various host plants, causing economically important diseases such as Pierce's disease in grapevine and citrus variegated chlorosis (CVC) in sweet oranges. The aggregative nature of this bacterium has been extensively documented in the plant xylem and the insect's foregut. Structured communities of microbial aggregates enclosed in a self-produced polymeric matrix and attached to a surface are defined as biofilms. In this study, we characterized biofilm formation by X. fastidiosa through the use of a novel in vitro assay for studying biofilm growth in a potential mimic system of what might occur in planta. We used wood, a xylem rich material, as a surface for bacterial attachment and biofilm formation, under shear force. We demonstrated that X. fastidiosa strains isolated from various hosts formed biofilm on wood in this in vitro assay. Different biofilm morphology was detected, which seems to vary according to the strain tested and microenvironmental conditions analyzed. We observed that strains from different hosts could be grouped according to three parameters: biofilm morphology, the ability to form clumps in liquid culture, and the ability to attach to glass surfaces. We hypothesize that biofilm formation is likely a major virulence factor in diseases related to X. fastidiosa, bringing a new perspective for disease treatment.
Biological Control Agents for Fire Blight of Apple Compared Under Conditions Limiting Natural Dispersal
Authors: Pusey P. L.
Published: May 2007

The efficacy of Pantoea agglomerans strain E325 for control of fire blight of apple was determined in comparative field trials involving other bacterial antagonists. Concurrently, the importance of the natural dispersal of bacteria as a complicating factor was assessed. Tests were performed under two sets of conditions, those that allowed for the dispersal of bacteria via honeybee activity and those that minimized it through the use of translucent polyethylene enclosures around single trees. The enclosures also raised daytime temperatures and allowed for controlled wetting, two factors important to the development of blossom blight. Singleantagonist treatments with strain E325, Pseudomonas fluorescens strain A506, and P. agglomerans strain C9-1 were applied to open blossoms on each of 10 enclosed trees and 10 nonenclosed trees. During bloom, suspensions of antagonists (108CFU/ml) were applied twice with a brush, and a suspension of Erwinia amylovora (107CFU/ml) was subsequently applied once using the same method. Two days after inoculation with the pathogen, trees were misted to simulate precipitation. Flower-to-flower spread of antagonistic bacteria was less frequent on trees surrounded by plastic enclosures than on nonenclosed trees. The range and statistical separation of means for population size of E. amylovora and disease incidence among treatments were greater for enclosed trees than for nonenclosed trees. Based on these results, the natural spread of antagonists being compared may mask differences in their efficacy as biocontrol agents. Such distortions and resulting misinterpretations could be lessened by separating treatments widely in large orchard blocks and by monitoring microbial populations. Strain E325 from fresh or lyophilized cultures was consistently more effective than standard antagonists in suppressing E. amylovora and reducing disease incidence. To fully assess its potential use for fire blight, larger-scale trials under various conditions will be necessary.
First Report of Tomato infectious chlorosis virus in Spain
Authors: Font M. I. , Martínez-Culebras P. , Jorda M. C. , Louro D. , Vaira A. M. , Accotto G. P.
Published: May 2007

During the summer and autumn of 2001, symptoms of interveinal yellowing, bronzing, brittleness, and rolling of lower leaves were observed in greenhouse- and field-grown tomato (Lycopersicon esculentum) plants in Castellon Province in eastern Spain. Symptoms resembled those caused by the whitefly-transmitted criniviruses (1,2). Total RNA was extracted from 28 samples of symptomatic leaves collected in three greenhouses and one field and analyzed by reverse transcription-polymerase chain reaction using primers specific for Tomato chlorosis virus (ToCV) (1) and Tomato infectious chlorosis virus (TICV) (2). The 501-bp TICV-specific DNA fragment was amplified in four samples collected during the summer in three greenhouses and one field, and the 439-bp ToCV-specific DNA fragment was amplified in 15 samples collected during the autumn in the same three greenhouses; no mixed infections were found. The DNA fragments amplified from TICV were sequenced and showed 99 to 100% identity with the TICV isolates (GenBank Accession Nos. U67449 and AY048855) from the United States and Italy, respectively, confirming the diagnosis. One sequence was deposited as GenBank Accession No. AF479662. To our knowledge, this is the first report of TICV in Spain and the second in Europe.

References: (1) D. Louro et al. Eur. J. Plant Pathol. 106:539, 2000. (2) A. M. Vaira et al. Phytoparasitica. In Press.
Races of Isolates of Plasmopara halstedii from Spain and Studies on Their Virulence
Authors: Molinero-Ruiz M. L. , Domínguez J. , Melero-Vara J. M.
Published: May 2007

Plants infected with downy mildew were collected from 1994 to 2000 in sunflower fields in Spain. The race of 102 bulk isolates of Plasmopara halstedii obtained from them was determined by inoculation of sunflower lines traditionally used as differentials for characterization of the pathogen. Nine different races of the fungus were determined. Although race 1 was most common and was the only one found in central Spain, races 4, 6, and 7 were widespread in southern Spain. The results allowed the identification of a new race of the pathogen, race 10, and of a race not previously reported in Europe, race 8. According to the proposal of a new system for characterization of the isolates of P. halstedii in the late 1990s, Coded Virulence Formulae (CVF) were assigned to bulk isolates and single-sporangium (ss) isolates obtained from them. The CVF of the bulk isolates (CVFi) did not always fit with the previous designation. Similarly, ss isolates from the same bulk isolate exhibited different CVF, not only among themselves, but also compared with the CVF of the source isolate. Although a revision of the differential lines used to perform the racial characterization of fungal isolates seems to be needed, the occurrence of a diversity of genotypes in field populations of P. halstedii and a high frequency of recombination and/or mutation of the fungal genome is also suggested.
First Report of Tomato yellow leaf curl virus Associated with Beans, Phaseolus vulgaris, in Cuba
Authors: Martínez Zubiaur Y. , Quiñones M. , Fonseca D. , Potter J. L. , Maxwell D. P.
Published: May 2007

Beans with yellow mosaic and/or leaf crumple symptoms were collected in three fields in the southern area of the province of Havana, Cuba in December 2001 and February 2002. DNA was extracted from the fresh bean leaves of 25 samples (1). Dot blot hybridization was performed at high stringency with a specific probe for Tomato yellow leaf curl virus (TYLCV). The specific probe was prepared by alkaline phosphatase labeling of the polymerase chain reaction (PCR) fragment amplified with primer pair, PTYIRv21/PTYIRc287, containing the intergenic region (IR) of TYLCV, and chemiluminescent hybridization was completed as described by the manufacturer (AlkPhos Direct Labeling and Detection Systems, Amersham Pharmacia Biotech Inc., Piscataway, NJ). Four of the samples had positive hybridization signals. PCR was performed with overlapping primers for TYLCV (2) with the DNA extract from sample 01–44, which gave a positive hybridization signal with the TYLCV probe, and a 2.8-kb fragment was obtained. This fragment was cloned in pGem T-Easy (pBeTY44) and partially sequenced. Greater than 96% nt identity was obtained for the 591 nt of the IR and 504 nt of the N-terminus of the Rep gene with TYLCV (GenBank Accession No. AF260331). Also, PCR was completed on 11 of the 25 samples with the degenerate primer pair PAL1v1978/PAR1c715 for DNA-A (3). Eight samples gave fragment sizes of 1.4 kb and one sample gave a fragment of 1.3 kb. The 1.3-kb fragment from sample number 01–50 was cloned in pGem T-Easy (pBeBG50) and partially sequenced. Pairwise nucleotide comparisons with Bean golden yellow mosaic virus (BGYMV, GenBank Accession No. M91604) were 95% for 719 nt of the N-terminus of the Rep gene. These results are consistent with the association of both TYLCV and BGYMV in beans and have important implications for future disease management strategies.

References: (1) G. P. Accotto et al. Eur. J. Plant. Pathol. 106:179, 2000. (2) M. K. Nakhla et al. Plant Dis. 78:926, 1994. (3) M. Rojas et al. Plant Dis. 77:340, 1993.
Distribution of Mating Type Alleles and Fertility Status of Magnaporthe grisea Causing Gray Leaf Spot of Perennial Ryegrass and St. Augustinegrass Turf
Authors: Viji G. , Uddin W.
Published: May 2007

Isolates of Magnaporthe grisea causing gray leaf spot of perennial ryegrass (PR) (Lolium perenne) and St. Augustinegrass (SA) (Stenotaphrum secundatum) were analyzed for mating compatibility and fertility. A total of 312 isolates of M. grisea from PR and 62 isolates from SA were paired with hermaphroditic tester strains from finger millet (Eleusine coracana), rice (Oryza sativa), and wheat (Triticum aestivum). All the PR isolates belonged to a single mating type, MAT1-2. Male fertility was observed in all these isolates. Asci and ascospores were not produced regardless of their developmental stage. Of the 139 (44.6%) isolates from PR that formed perithecia with the fertile tester strains, 83 (59.7%) were highly fertile, 33 (23.7%) were intermediately fertile, and 23 (16.5%) were low in fertility. Both mating types were observed among the isolates of SA, where MAT1-1 predominated the MAT1-2 type. An equal number of male and female fertile isolates were detected among these isolates obtained from a single location; however, none of the isolates behaved as hermaphrodites. Few ascospores were produced in crosses between two isolates of SA and a finger millet tester. Of the 62 monoconidial isolates of SA tested, 19 (30.6%) isolates formed perithecia, of which 5 (26.3%) were highly fertile, 7 (36.8%) were intermediately fertile, 7 (36.8%) were low in fertility, and 43 (69.4%) were infertile. The results of this study indicate that the sexual stage may not be a significant factor contributing to the genetic variation the gray leaf spot pathogen population.
Characterization of Root-Knot Nematode Populations Associated with Vegetables in New York State
Authors: Mitkowski N. A. , Van der Beek J. G. , Abawi G. S.
Published: May 2007

The northern root-knot nematode (Meloidogyne hapla) causes significant damage on vegetables in New York State. This study was conducted to determine if other species of Meloidogyne are also present in New York vegetable fields and to better characterize the root-knot populations in order to facilitate the development of effective rotations for nematode management. Populations of Meloidogyne were collected from 18 vegetable fields across New York and maintained in the greenhouse on tomato cv. Rutgers as both field populations and single-female populations. For the purposes of species identification, nematodes from each population were examined using perineal pattern analysis, scanning electron microscopy, and cytological analysis. All techniques identified the presence of only Meloidogyne hapla in the collected samples. The host range of the populations of Meloidogyne that were collected was investigated using a modified form of the North Carolina Differential Host Test. While host ranges were variable among the collected populations, the host range of all populations closely corresponded to that of M. hapla. The internal transcribed spacer region (ITS1) of the collected populations was amplified and sequenced. All sequences from the collected populations corresponded to the published sequence of M. hapla. Based on these results, it was concluded that M. hapla is the only root-knot nematode species present in New York vegetable fields. Crop rotational strategies for management of the root-knot nematode on vegetables in New York should be devised to reflect this fact.
Assessment of the Effects of Fertilizer Applications on Gray Leaf Spot and Yield in Maize
Authors: Caldwell P. M. , Ward J. M. J. , Miles N. , Laing M. D.
Published: May 2007

The effects of the application of 0, 60, and 120 kg N ha-1 and of 0, 25, 50, and 150 kg K ha-1 on final disease severity, standardized area under disease progress curve, and grain yield were investigated at Cedara, South Africa, on a maize (Zea mays) hybrid susceptible to gray leaf spot (GLS), caused by Cercospora zeae-maydis. The trial was a randomized 3 × 4 factor design, split for fungicide treatments, and replicated three times. With increased N and K levels, final percent leaf blighting and the standardized area under disease progress curve were higher. In fungicide-treated maize, grain yields increased with increasing levels of N and K, as expected. In non-fungicide-treated maize, grain yield increased significantly with increased levels of N, despite increased disease severity. This was in contrast to small increases in grain yields from non-fungicide-treated maize with increased K levels, which were not significant. This was probably because grain yield response, which should have occurred at higher K applications, was reduced by increased disease severity. The effect of N, P, and K on GLS wasinvestigated at Ahrens. Maize was grown in a 4 × 4 × 4 N-P-K factorial, in a randomized complete block design. Fertilizer was applied at 0, 60, 120, and 180 kg N ha-1, 0, 30, 60, and 120 kg P ha-1, and 0, 50, 100, and 150 kg K ha-1. No fungicides were applied. A single disease assessment at physiological maturity showed that final disease severity increased with increasing levels of N, P, and K. These results have implications for small-scale farmers who are encouraged to fertilize for increased grain yields but may not have the resources to apply fungicide sprays to control fungal diseases.
Differential Resistance toBotryosphaeria ribisAmongCercisTaxa
Authors: Pooler M. R. , Jacobs K. A. , Kramer M.
Published: May 2007

The redbud (Cercis sp.) is a popular ornamental small tree or shrub, valued commercially for its early spring bloom and adaptability to diverse environmental conditions. Despite these characteristics, large-scale production of redbud has been limited, due in part to their susceptibility to a fungal canker caused by Botryosphaeria ribis. We screened 711 plants in 11 Cercis taxa for response to inoculation with B. ribis. The taxa native to North America, C. canadensis and C. occidentalis, were more susceptible than Asian species. A logistic regression of the number of symptomatic plants 10 weeks postinoculation with taxa and size (stem diameter) as independent variables explained 41% of the variation. Sixteen percent was attributable to taxon effects and 36% was attributable to taxon-independent size effects. Size and taxon effects were not completely orthogonal, and taxa with larger mean stem diameters generally had higher percentages of symptomless plants. A high level of unexplained variation (59%) was found, and is likely due to intraspecific variation among seed lots. Comparisons of 11 seed lots of C. canadensis revealed significantly different proportions of diseased plants ranging from 52 to 92% after 10 weeks, but all plants eventually became diseased.
Detection, Survival, and Sources of Inoculum for Bacterial Diseases of Leafy Crucifers in Oklahoma
Authors: Zhao Youfu , Damicone John P. , Bender Carol L.
Published: May 2007

Xanthomonas campestris pv. campestris, X. campestris pv. armoraciae, and Pseudomonas syringae pv. maculicola are bacterial pathogens that cause leaf spot diseases on leafy crucifers in Oklahoma. Polymerase chain reaction (PCR) amplification of the cfl gene from the gene cluster encoding the phytotoxin coronatine was used to identify coronatine-producing strains of P. syringae, and the expected 0.65-kb PCR product was detected in 19 strains of P. syringae pv. maculicola originating from diseased crucifers in Oklahoma. A simple, rapid PCR method based on primers from the cfl gene was developed to detect coronatine-producing strains of P. syringae in planta. Pathogenicity tests confirmed the cfl-positive strains to be P. syringae pv. maculicola. To monitor the survival of X. campestris pv. armoraciae and P. syringae pv. maculicola in the field, turnip and collards were inoculated with rifampicin-resistant strains and were buried beneath the soil or left on the soil surface. Both pathogens were recovered from turnip and collard debris up to 2 months following burial, but neither pathogen was recovered from soil after the debris had decomposed. However, both pathogens were recovered from plant debris left on the soil surface for up to 5 months. Four production fields were surveyed for sources of inoculum of the bacterial pathogens from October 1999 to May 2000. X. campestris pv. campestris was isolated from the weed shepherd's purse (Capsella bursa-pastoris) in all fields, and from volunteer turnip and kale in three fields. X. campestris pv. campestris and P. syringae pv. maculicola were isolated from surface debris and regrowth from crop stubble left in one field after harvest in the fall. X. campestris pv. campestris was detected in 6 of 51 lots of crucifer seed assayed. X. campestris pv. armoraciae and P. syringae pv. maculicola were not recovered from weeds, volunteer plants, or seed lots.
Resistance to Fusarium oxysporum f. sp. melonis Race 1,2 in Muskmelon Lines Nad-1 and Nad-2
Authors: Ficcadenti N. , Sestili S. , Annibali S. , Campanelli G. , Belisario A. , Maccaroni M. , Corazza L.
Published: May 2007

Of seven doubled-haploid melon lines parthenogenetically originated using irradiated pollen, two lines, Nad-1 and Nad-2, were selected for resistance to Fusarium wilt after successive inoculations with F. oxysporum f. sp. melonis race 1,2w virulent isolate. Nad-1 and Nad-2 were compared with the commercial hybrids and with the parent cvs. Isabelle and Giallo di Paceco. Evaluation of germplasm extended over a 2-year period showed a higher resistance of Nad-1 and Nad-2 plants to Fusarium oxysporum f. sp. melonis race 1,2 than other genotypes tested in this study. The resistance expressed in the two doubled-haploid lines could be due to their homozygous state that maximizes the expression of the genes for resistance already present in the parental line Isabelle. The use of this source of resistance may be exploited commercially either in rootstocks or to facilitate breeding for F1 hybrids. Future research will concentrate on the identification of genetic markers associated with resistance to race 1,2 using these doubledhaploid lines.
First Report of Cross-Infectivity of Plasmopara halstedii from Marshelder to Sunflower
Authors: Gulya T. J.
Published: May 2007

In May 1999, marshelder (Iva xanthifolia Nutt.) plants with chlorotic upper leaves and abundant white sporulation on abaxial surfaces were observed in roadside ditches near Fargo, ND. Ovoid to elliptical zoosporangia (20 to 30 μm × 15 to 20 μm) that were borne on sporangiophores 400 to 500 μm long and branched monopodially at right angles were recovered from infected marshelder leaves. Dimensions of the zoosporangia and sporangiophores fall within those reported for Plasmopara halstedii (Farl.) Berl. & de Toni (1). Zoosporangia rinsed from marshelder plants were used to inoculate 3-day-old sunflower seedlings. The seedlings were immersed in a suspension of 2 × 104 zoosporangia per ml for 3 h, and planted in a greenhouse maintained at 18 to 24°C with a 16-h photoperiod. Systemic chlorosis, stunting, and sporulation were observed on sunflower plants 12 days after inoculation. Isolates from two individual marshelder plants were inoculated on a standard set of nine sunflower downy mildew differential lines, and were identified as race 3 (virulence pattern 700) and race 4 (virulence pattern 730). The marshelder isolates were evaluated for metalaxyl sensitivity by a soil drench inoculation method. Seed of an oilseed sunflower hybrid commercially treated with metalaxyl (138 g a.i./100 kg of seed) were planted in flats filled with sand and perlite (1:1, vol/vol). Three days after planting, the flats were drenched with a zoosporangial suspension (2 × 104 zoosporangia per ml) for four consecutive days. Both isolates produced 100% infection on plants grown from metalaxyl-treated seed, indicating the isolates were metalaxyl-insensitive. While over 80 species within 35 Compositae genera are reported to be hosts for P. halstedii, this is the fourth report of pathogenicity on sunflower by zoospores originating from other genera, the other three being Ambrosia (ragweed) (4), Dimorphotheca (cape marigold) (2) and Xanthium (cocklebur) (3). The cross-infectivity of the P. halstedii from Ambrosia, Iva, and Xanthium indicates that Compositae weeds may serve as a reservoir of P. halstedii to infect cultivated sunflower, and these weeds may help to perpetuate the metalaxyl-insensitive strain of P. halstedii.

References: (1) G. Hall, Mycopathologia 106:205, 1989. (2) E. E. Leppik, Plant Dis. Rep. 49:940, 1965. (3) F. Viranyi, Helia 7:35, 1985. (4) I. Walcz et al. Helia 33:19, 2000.
First Report of Rupestris stem pitting associated virus in Argentina
Authors: Tarnowski C. G. , Worlock P. A. , Ulanovsky S. , Gómez Talquenca S.
Published: May 2007

Rupestris stem pitting associated virus (RSPaV), a component of the rugose wood complex (RWC), is a worldwide graft transmissible disease of grapevines (Vitis vinifera L.). RSPaV has a single-stranded 8,726-nt RNA genome, belongs to the genus Foveavirus, and is often associated with Rupestris stem pitting (RSP) disease (2). In 1995, a grapevine sanitary selection program was implemented in Mendoza to investigate this and other grapevine viral diseases. RSP can be diagnosed when V. rupestris cv. St. George is used as a woody indicator for biological indexing. Chip-bud inoculated St. George plants developed a row of small pits and grooves on the wood cylinder below the graft or around and below the inoculated point (1,2). After three seasons in the field, 15 accessions with RSP wood markings were observed. Mature leaves and bark shavings were extracted, partially purified, and analyzed by a onestep reverse transcription polymerase chain reaction method. The expected 339-bp band was found in only six of the positively indexed samples using the specific 13/14 primer pair (2). Other viruses associated with RWC have been detected in Argentina, but to our knowledge, this is the first report of RSPaV.

References: (1) A. C. Goheen. Page 53 in: Compendium of Grape Diseases, R. C. Pearson and A. C. Goheen, eds. American Phytopatological Society, St. Paul, MN, 1988. (2) B. Meng. Rupestris stem pitting: Insights on etiology and development of reverse transcription-polymerase chain reaction and immunoassays for diagnosis. Ph.D. Diss. Cornell University, Ithaca, NY, 1999.
First Report of Inonotus rickii Causing Canker Rot on Boxelder in Europe
Authors: Intini M.
Published: May 2007

In November 2001, during an examination of ornamental trees in Seville, Spain, several boxelders (Acer negundo L.) were observed with symptoms and signs of canker rot disease. Symptoms and signs occurred mainly 2 to 4 m above ground and included bulges of the stem and bark necrosis. Golden brown masses of fungal tissue up to 20 cm wide and 15 cm thick occurred over the affected areas, but were sometimes hidden behind bark scales. Cultures were obtained from decayed wood and hyphal strands. On potato dextrose agar (PDA), mycelium was initially white and cottony, later changing to cream color, ochre, and finally dark brown. In 4-week-old cultures, abundant brown chlamydospores of varying shape, but usually globose and 5 to 14 μm in diameter, were often formed in chains. Also present on PDA and diseased trees were dark brown setal hyphae, 80 to 250 μm long and 5 to 15 μm in diameter. Based on morphological characteristics, the fungus was identified as Ptychogaster cubensis Pat., the anamorph of Inonotus rickii (Pat.) Reid. I. rickii is a white rot fungus found in living trees in tropical and subtropical areas. In Europe, it has been previously reported only from Sicily, Italy, where it was found sporadically on living Parkinsonia sp. and Schinus molle L. (1,2). In Seville,I. rickii is widespread and appears to be well adapted to the area. Classified as a canker rot pathogen, this introduced fungus not only has the ability to cause decay of heartwood, resulting in structural damage to the tree, but it also can parasitize the sapwood and cambium resulting in a progressive crown dieback. To our knowledge, this is the first record of I. rickii in Spain and on boxelders in Europe.

References: (1) M. Intini, Contributo alla conoscenza dei funghi lignicoli italiani: Inonotus rickii (Pat.) Reid. Micol. Ital. 1:49, 1988. (2) L. Ryvarden and R. L. Gilbertson. European Polypores. Fungiflora, ed. Oslo, Norway, 1993.
First Report of Charcoal Rot (Macrophomina phaseolina) on Sunflower in North and South Dakota
Authors: Gulya T. J. , Krupinsky J. , Draper M. , Charlet L. D.
Published: May 2007

In September 1998, symptoms suggestive of charcoal rot were observed on oilseed sunflower (Helianthus annuus L.) plants in western North and South Dakota. Symptoms first observed on plants approaching physiological maturity consisted of silver-gray lesions girdling the stem at the soil line, premature plant death, and reduced head diameter. The pith in the lower stem was completely absent or compressed into horizontal layers. Black, spherical microsclerotia were observed in the pith of the lower stem, underneath the epidermis, and on the exterior of the taproot. Confirmation of Macrophomina phaseolina (Tossi) Goid. as the causal agent was based on the size of the microsclerotia, which ranged from 80 to 90 μm in diameter, from both infected sunflowers and pure cultures (1). The only other sunflower pathogen known to form microsclerotia is Verticillium dahliae Kleb., whose microsclerotia are irregular in shape and are 15 to 50 μm in diameter. Some prematurely dead sunflower plants lacked typical charcoal rot stem lesions, but contained Macrophomina microsclerotia. Plants with atypical symptoms were colonized by the sunflower stem weevil (Cylindrocopturus adspersus (LeConte)) and the black sunflower stem weevil (Apion occidentale Fall). This agrees with observations in Texas, where Macrophomina-infected sunflower plants parasitized by stem-feeding insects often displayed atypical charcoal rot symptoms (3). Charcoal rot incidence in 1998 in western North Dakota was 25%, compared with 0% in eastern North Dakota. Charcoal rot was not observed in 1999, the fourth wettest growing season on record, but was observed again in 2000 and 2001. The recent increase in sunflower production in western North and South Dakota, areas typically hotter and drier than the eastern portions of both states, and the potential involvement of stem weevils as vectors of Macrophomina (2) may lead to an increased incidence of charcoal rot in sunflower.

References: (1) P. Holliday and E. Punithalingam. Macrophomina phaseolina. No. 275 in: Description of Pathogenic Fungi and Bacteria, CMI, Kew, Surrey, UK, 1970. (2) S. M. Yang et al. Phytopathology 73:1467, 1983. (3) S. M. Yang and D. F. Owen. Phytopathology 72:819, 1982.
Use of Optical Sorting to Detect Wheat Kernels Infected with Tilletia indica
Authors: Dowell Floyd E. , Boratynski Theodore N. , Ykema Ronald E. , Dowdy Alan K. , Staten Robert T.
Published: May 2007

Wheat infected with Tilletia indica is subject to international regulation by 78 countries, and U.S. economic losses could exceed $1 billion if T. indica was found throughout major wheat-producing regions and caused wheat exports to be halted. Samples are currently manually inspected for the presence of kernels with Karnal bunt as part of routine survey methods. This visual inspection of all seed in a sample can result in harvest delays due to long inspection times and missed kernels due to inspector fatigue. A high-speed sorter was tested to determine if infected kernels could be rapidly removed from 1,800-g wheat samples. When the sorter removed about 8% or more of the sample, the reject portion contained 100% of the bunted kernels. Concentrating the bunted kernels in a smaller sample size will reduce sample inspection time and should reduce inspection errors. One high-speed sorter can process up to 8,800 kg/h; thus, bunted kernels can be rapidly removed from samples or large lots. Each sample was sorted in less than 1 min. This technology provides the wheat industry with a tool to rapidly inspect samples to aid in regulating Karnal bunt, and to remove bunted grains from seed wheat and wheat destined for food or feed use.
Differential Response of Selected Peanut (Arachis hypogaea) Genotypes to Mechanical Inoculation by Tomato spotted wilt virus
Authors: Mandal B. , Pappu H. R. , Culbreath A. K. , Holbrook C. C. , Gorbet D. W. , Todd J. W.
Published: May 2007

Screening of peanut germ plasm for resistance to Tomato spotted wilt virus (TSWV) has been largely inefficient due to the lack of a screening technique based on mechanical transmission of the virus under controlled environmental conditions. We have studied the reaction of three peanut cultivars (Georgia Green, Georgia Runner, C-99R) and one breeding line (C11-2-39) using a highly efficient mechanical inoculation procedure. The disease response was studied at two temperature regimes, 25 to 30°C (low temperature) and 30 to 37°C (high temperature). Based on percent transmission, symptomatology, distribution of TSWV, and relative levels of TSWV nucleocapsid (N) protein, Georgia Runner and Georgia Green were found to be susceptible, whereas C-99R and C11-2-39 were resistant. Of the four genotypes tested, C11-2-39 had the highest level of resistance to TSWV. The results correlated with the field performance of the genotypes except in the case of Georgia Green, which could not be distinguished from TSWV-susceptible Georgia Runner. Exposure of the inoculated plants to higher temperature (30 to 37°C) resulted in a better resistant response as reflected by reduced systemic infection, localized symptom expression, restricted viral movement, and reduced levels of TSWV antigen. To our knowledge, this is the first report of differential response of peanut genotypes to TSWV using mechanical inoculation. The four peanut genotypes should be useful as reference standards for the initial screening and identification of sources of TSWV resistance in peanut germ plasm.