bluuebunny/crossref_metadata_2025 huggingface dataset:
First Report of Cherry virus A and Little cherry virus-1 in Poland
Authors: Komorowska B. , Cieślińska M.
Published: May 2007

Cherry virus A (CVA), a member of the genus Capillovirus, has been reported in sweet cherry in Germany, Canada, and Great Britain. No data are available on the effects of CVA on fruit quality and yield of infected trees. Little cherry disease (LChD) occurs in most cherry growing areas of the world. Symptoms on sensitive cultivars include discolored fruit that remain small, pointed in shape, and tasteless. Three Closterovirus spp. associated with LChD have been described (Little cherry virus-1 [LChV-1], LChV-2, and LChV-3). Diseased local and commercial cultivars of sour cherry trees were found in a Prunus sp. germplasm collection and orchards in Poland during the 2003 growing season. The foliar symptoms included irregular, chlorotic mottling, distortion, and premature falling of leaves. Some of the diseased trees developed rosette as a result of decreased growth and shortened internodes. Severely infected branches exhibited dieback symptoms. Because the symptoms were suggestive of a possible virus infection, leaf samples were collected from 38 trees and assayed for Prune dwarf virus and Prunus necrotic ringspot virus using double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). RNA extracted from leaves was used in a reverse transcription-polymerase chain reaction (RT-PCR) with the One-Step RT-PCR with Platinum Taq (Invitrogen Life Technologies) and primer sets specific for CVA (1), LChV-1 (3), and LChV-2 (3). The RNA samples were also tested using RT-PCR for detection of Cherry mottle leaf virus (CMLV), Cherry necrotic rusty mottle virus (CNRMV), and Cherry green ring mottle virus (CGRMV) with specific primer sets (2). Amplification of a 397-bp coat protein gene product confirmed infection of 15 trees with CVA. A 419-bp fragment corresponding to the coat protein gene of LChV-1 was amplified from cv. Gisela rootstock and local cv. WVIII/1. To confirm RT-PCR results, CVA amplification products from local cv. WX/5 and LChV-1 from cvs. Gisela and WVIII/1 were cloned in bacterial vector pCR 2.1-TOPO and then sequenced. The sequences were analyzed with the Lasergene (DNASTAR, Madison, WI) computer program. The alignment indicated that the nucleotide sequence of cv. WX/5 was closely related to the published sequences of CVA (Genbank Accession No. NC_003689) and had an 89% homology to the corresponding region. The nucleotide sequence similarity between the 419-bp fragment obtained from cvs. Gisela and WVIII/1 was 87% and 91%, respectively, compared with the reference isolate of LChV-1 (Genbank Accession No. NC_001836). The sampled trees tested negative for LChV-2, CGRMV, CMLV, and CNRMV using RT-PCR. Some trees tested positive for PNRSV and PDV. To our knowledge, this is the first report of CVA and LChV-1 in Poland.

References: (1) D. James and W. Jelkmann. Acta Hortic. 472:299, 1998. (2) M. E. Rott and W. Jelkmann. Eur. J. Plant Pathol. 107:411,2001. (3) M. E. Rott and W. Jelkmann. Phytopathology. 91:61, 2001.
First Report of Bacterial Leaf Blight of Coriander Caused by Xanthomonas campestris pv. coriandri in Taiwan
Authors: Lee Y.-A. , Liu Y.-H. , Liu H.-L.
Published: May 2007

Leaf blight symptoms on coriander (Coriandrum sativum) were observed during the summers of 2000 to 2002 in fields at the Beidou and Sijhou townships, Changhua County, Taiwan. Symptoms first appeared as small spots on the lower sides of leaves and stems. The centers of the spots quickly turned brown and were surrounded by whitish yellow halos. The brown spots and halos enlarged rapidly and coalesced into irregular, yellowish or brownish dry dead areas on the leaf. V-shaped and chlorotic blotch symptoms were also found at the margins of leaves. Isolations from diseased leaves consistently yielded bacterial colonies that were yellow and glistening on nutrient and potato dextrose agar media. Five representative strains were chosen for further characterization. All strains were gram-negative rods, aerobic, and produced yellow, nonwater soluble, xanthomonadin pigments identified by thin-layer chromatography (1). The strains were positive for catalase and β-galactosidase and negative for oxidase, nitrate reductase, urease, and tryptophanase (indole production) and hydrolyzed starch, gelatin, and esculin. Hydrogen sulfide was produced from cysteine. L-asparagine was not sufficient as a sole carbon source for growth. In Dye's medium C, acids were produced from metabolizing arabinose, glucose, and sucrose but not from rhamnose, cellobiose, lactose, dulcitol, mannitol, and sorbitol. The bacterium was identified as Xanthomonas campestris. Almost complete 16S rDNA sequence of strain TC3 (1,502 bp; GenBank Accession No. AY604178) was determined and compared with available 16S rDNA sequences in GenBank. The sequence was highly identical (99%) to those of Xanthomonas campestris pathovars. Coriander plants were inoculated by spraying bacterial suspensions (108 CFU/ml) on leaves, enclosed in a plastic bag to maintain high humidity for 2 days, and kept in a growth chamber at 28°C. Typical symptoms were observed in 2 to 6 days in all four inoculated plants and appeared to be identical to those observed in the fields. Control plants were inoculated with sterile distilled water and showed no symptoms. The bacterium was readily reisolated from diseased leaves. Bacterial leaf blight of coriander was first reported in India, and the pathogen was identified as X. campestris pv. coriandri (2). To our knowledge, this is the first occurrence of this bacterium on coriander in Taiwan.

References: (1) N. W. Schaad et al. Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. The American Phytopathological Society, St. Paul, MN, 2001. (2) M. C. Srinivasan et al. Proc. Indian Acad. Sci. Sect. B 53:298, 1961.
Soybean Root Systems and Sudden Death Syndrome Severity: Taproot and Lateral Root Infection
Authors: Ortiz-Ribbing Loretta M. , Eastburn Darin M.
Published: May 2007

Experiments were conducted in the greenhouse to evaluate the role that infection location (taproot versus lateral root) plays in disease development of sudden death syndrome (SDS) on soybean (Glycine max) caused by the fungus Fusarium solani f. sp. glycines. Root characteristics of 12 soybean cultivars, representing a range of SDS reactions, were evaluated and compared for disease responses. A method was developed to facilitate taproot or lateral root infection. Results show that this procedure may be useful for observing a continuum of foliar and root disease responses. Significant differences in root length, surface area, and average diameter were observed among cultivars when infection occurred at the taproot or on the lateral roots. A significant correlation existed between foliar symptoms (i.e., area under the disease progress curve [AUDPC]) and root length, surface area, and volume for inoculated plants. Root volume and percent root discoloration were significantly different among individual soybean cultivars, and percent root discoloration was associated with AUDPC values only when the initial site of infection was on the lateral roots of soybean plants. Useful information about root system responses to SDS may be obtained from infection of the entire root system as opposed to only taproot infection.
Evaluation of Adapted Wheat Cultivars for Tolerance to Pythium Root Rot
Authors: Higginbotham R. W. , Paulitz T. C. , Campbell K. G. , Kidwell K. K.
Published: May 2007

Genetic resistance in wheat (Triticum aestivum) against Pythium species would be an efficient means of control of this major root fungal pathogen, but so far no source has been identified. In addition, no long-term, sustainable options for controlling Pythium root rot are available; therefore, identifying and then incorporating genetic resistance into wheat cultivars would create an ideal method of control for this disease. The objective of this study was to examine the level of tolerance to Pythium root rot among a diverse set of wheat germ plasm collected from all major wheat production regions in the United States. Pythium debaryanum isolate 90136 and P. ultimum isolate 90038, previously identified as the most virulent Pythium isolates on wheat, were used to infest pasteurized soil, which was seeded with wheat genotypes and placed in a growth chamber maintained at a constant 16°C with a 12-h photoperiod and ambient humidity. Length of the first leaf and plant height measurements were recorded, and roots were digitally scanned to create computer files that were analyzed using WinRhizo software for length and number of tips. Significant (P < 0.05) differences in plant variables were detected among wheat genotypes in the presence of both Pythium species, and a significant (P < 0.0001) correlation between plant stunting and root loss was detected. Based on both shoot and root measurements, Caledonia, Chinese Spring, MN97695, and OR942504 appear to be highly susceptible to Pythium root rot, whereas genotypes KS93U161, OH708, and Sunco were the most tolerant to this disease.
First Report of White Mold Caused by Sclerotinia sclerotiorum on Common Sage (Salvia officinalis) in Italy
Authors: Garibaldi A. , Minuto A. , Gullino M. L.
Published: May 2007

Salvia officinalis L. is cultivated as an aromatic ornamental plant in Italy. In the spring of 2003, rooted cuttings grown in containers in commercial farms near Albenga (northern Italy) had soft and watery stem tissue covered with whitish mycelium at the soil level. Leaves and stems showed necrotic areas of irregular shape and size. As necrosis progressed, infected plants wilted and died. Wilt occurred within a few days on young plants. Because of high plant density, the pathogen spread rapidly within and across containers to infect many rooted cuttings. Sclerotinia sclerotiorum (Lib.) de Bary (2) was consistently recovered from infected stem pieces of Salvia officinalis that were disinfested for 1 min in 1% NaOCl and plated on potato dextrose agar (PDA) amended with 100 ppm of streptomycin sulfate. Sclerotia produced on PDA were ellipsoid and measured 1.4 to 4.2 × 1.1 to 2.1 (average 2.1 × 1.5) mm. Pathogenicity of three isolates obtained from infected plants was confirmed by inoculating 30-day-old plants grown in pots (14-cm diameter). Inoculum of each isolate was 14-day-old cultures of mycelium and sclerotia grown on sterile wheat kernels (300 g) and deionized water (320 ml) in a 1-liter flask at 20 to 25°C. Inoculum (10 g) of each isolate was placed on the soil surface around the base of 10 plants. Ten noninoculated plants served as controls. The inoculation trial was repeated once. All plants were kept in a screenhouse at temperatures ranging between 8 and 31°C and watered as needed. Inoculated plants developed symptoms of leaf yellowing, followed by the appearance of white mycelium within 7 days, and eventually wilted within 12 to 15 days. Control plants remained symptomless. White mycelium and sclerotia developed on infected tissues, and S. sclerotiorum was reisolated from inoculated plants on PDA amended with 100 ppm of streptomycin sulfate. To our knowledge, this is the first report of white mold of Salvia officinalis caused by S. sclerotiorum in Italy. The disease has been observed in Canada (1) as well as Tasmania and New Zealand.

References: (1) G. J. Bolland and R. Hall. Can. J. Plant Pathol. 16:93, 1994. (2) N. F. Buchwald. Den. Kgl. Veterin.er-og Landbohojskoles Aarsskrift, 1949.
First Report of Powdery Mildew Caused by Oidium Subgenus Pseudoidium on Lonicera caprifolium in Italy
Authors: Garibaldi A. , Bertetti D. , Gullino M. L.
Published: May 2007

Honeysuckle (Lonicera caprifolium L., family Caprifoliaceae) is a climbing shrub used in gardens to cover walls and supports. During the summer of 2003, severe outbreaks of a previously unknown powdery mildew were observed on this species in some gardens near Biella (northern Italy). The first symptoms included extensive chlorosis on leaves, followed by the appearance of white mycelium on the adaxial and abaxial leaf surfaces. As the disease progressed, infected leaves turned yellow and died. Conidia were hyaline, ellipsoidal, and measured 27.6 to 43.2 × 12.2 to 21.6 μm (average 35.7 × 17.6 μm). Foot cells were cylindric and appressoria lobed. Fibrosin bodies were not present. Cleistothecia were not observed during the growing season. The pathogen was identified as Oidium subgenus Pseudoidium (2). The inoculation procedure involved gently pressing diseased leaves onto leaves of healthy L. caprifolium plants. Three plants of L. caprifolium were used as replicates. Noninoculated plants served as control. Inoculated and noninoculated plants were maintained in a garden at temperatures ranging from 15 to 25°C. After 10 days, typical symptoms of powdery mildew developed on inoculated plants. Noninoculated plants did not show symptoms. To our knowledge, this is the first report of powdery mildew on L. caprifolium in Italy. The presence of powdery mildew on different species of Lonicera has been reported in several countries, particularly, Microsphaera miurae U. Braun on L. morowii A. Gray in Germany (1), M. lonicerae (DC.) Winter on L. peryclimenum L. in England (3), and M. lonicerae-ramosissimae on L. ramosissima Fr. & Sav. in Japan (4). The conidia of M. lonicerae are smaller than those of the Oidium sp. reported on L. caprifolium. Voucher specimens are available at DIVAPRA Collection at the University of Torino.

References: (1) U. Braun. Mycotaxon 16:417, 1983. (2) U. Braun and S. Takamatsu. Schlechtendalia 4:1, 2000. (3) J. Robbins. Cecidology 15:15, 2000. (4) S. Tanda. Mycoscience 41:155, 2000.
First Report of Powdery Mildew Caused by an Oidium sp. on Spiraea japonica in Italy
Authors: Garibaldi A. , Gilardi G. , Gullino M. L.
Published: May 2007

Spiraea japonica is an old-fashioned shrub widely grown in Italy in parks and gardens. In the summer of 2003, severe outbreaks of a previously unknown powdery mildew were observed in some parks and gardens in the city of Torino (northern Italy). Infected leaves became covered on both sides with a white mycelium. As the disease progressed, infected leaves turned reddish and eventually dropped prematurely. The presence of powdery mildew infections on leaves sometimes caused their distortion and growth reduction. Frequently, mycelium was observed also on the stem. Conidia were hyaline, ellipsoid, cylindrical, or dol iform, born in chains, measured 21.0 to 38.4 × 10.8 to 14.4 mm, and showed fibrosin bodies. Cleistothecia were not observed. The pathogen was identified as Oidium subgenus Fibroidium (1,2). Pathogenicity was confirmed by spraying leaves of healthy potted S. japonica plants with a conidial suspension (105 conidia per ml) prepared in sterile water from diseased leaves. Three plants were inoculated and three noninoculated plants served as control. The artificial inoculation was carried out twice. After artificial inoculation, plants were maintained in a growth chamber at 25°C. After 20 days, powdery mildew symptoms developed. Microsphaera alni and Podosphaera oxyacanthae were described as causal agents of powdery mildew on S. japonica in the United States (3), while Sphaerotheca spiraeae was considered the causal agent of a powdery mildew observed in Japan (4) and more recently in Poland.

References: (1) U. Braun and S. Takamatsu. Schlechtendalia 4:1, 2000. (2) R. T. A. Cook et al. Mycol. Res. 101:975, 1997. (3) P. Pirone. Diseases and Pests of Ornamental Plants. John Wiley and Sons, NY, 1978. (4) K. Sawada. Rev. Appl. Mycol. 31:577, 1952.
Identification of a Potyvirus Causing Latent Infection in Calla Lilies
Authors: Chen C. C. , Chang C. A. , Tsai H. T. , Hsu H. T.
Published: May 2007

A new potyvirus designated as Calla lily latent virus (CLLV) was isolated from apparently healthy calla lilies (Zantedeschia spp.) collected from nurseries in Taichung County, Taiwan. Different from most calla lily-infecting potyviruses, CLLV infects Chenopodium quinoa and develops local lesions on inoculated leaves (3). Typical potyvirus particles approximately 780 nm long were detected from CLLV-induced C. quinoa local lesions. CLLV was transmitted readily to and established in C. quinoa. Attempts to establish CLLV infection in calla lilies from extracts of C. quinoa lesions were not successful. The virus was transmitted from infected to healthy calla lilies with difficulty. A 1.3-kb cDNA product was amplified by reverse transcription-polymerase chain reaction (RT-PCR) from CLLV-infected calla lilies and C. quinoa using potyvirus degenerate primers (2). The PCR product was cloned and sequenced. It was found to consist of 1,339 nucleotides (nt) (GenBank Accession No. AF469171) corresponding to the genome organization of the 3′terminal region of potyviruses. The deduced amino acid sequence contains 362 residues encoding the 3′terminal region of the nuclear inclusion b gene (80 residues) and the complete coat protein (CP) gene (282 residues). A 253-nt noncoding region (NCR) was found at the 3′terminal region of the cDNA. By comparing with known sequences of potyviruses, CLLV was identified as a new species of Potyvirus based on the uniqueness in the CP gene and 3′ NCR. Soybean mosaic virus and Watermelon mosaic virus 2 are the potyviruses most similar to CLLV, but they share only approximately 80% nucleotide identity with CLLV in the CP and NCR regions. Attempts to purify sufficient CLLV from C. quinoa for antiserum preparation were not successful. Alternatively, polyclonal antibodies were produced using E. coli-expressed CLLV CP (1). The antibodies were useful for detection of CLLV and its CP in calla lilies using enzyme-linked immunosorbent assay, sodium dodecyl sulfate-immunodiffusion, immuno-specific electron microscopy, and western blot. Field surveys showed that calla lily plants found positive for CLLV by serological methods always remained symptomless throughout the six-month growing season. Occasionally, CLLV was detected in symptomatic calla lilies, but these plants were consistently confirmed dually infected by other viruses (Dasheen mosaic virus and Konjak mosaic virus found most commonly). Infection of CLLV alone in calla lilies may not have a direct impact on the production and marketing of the crop. Synergism is not currently known when calla lilies are coinfected with other viruses. CLLV is spread by vegetative propagation through infected rhizomes or tubers.

References: (1) C. C. Chen et al. Plant Dis. 87:901–905, 2003. (2) S. S. Pappu et al. Plant Dis. 82:1121–1125, 1998. (3) F. W. Zettler and R. D. Hartman. Pages 464–470 in: Virus and Virus-like Diseases of Bulb and Flower Crops. G. Loebenstein et al., eds. John Wiley and Sons Inc., UK, 1995.
Rubber Tree (Hevea brasiliensis) Bark Necrosis Syndrome II: First Comprehensive Report on Causal Stresses
Authors: Nandris D. , Moreau R. , Pellegrin F. , Chrestin H. , Abina J. , Angui P.
Published: May 2007

Bark necrosis (BN), described and first studied in Côte d'Ivoire in the 1980s (2), affects most modern rubber plantations (i.e., grafted trees with high-yielding clones, intensive exploitation due to tapping frequency, and use of Ethrel as a yield stimulant) worldwide with a wide range of severity across sites. While previous (3) and recent (4) etiological analyses remain inconclusive, environmental factors were shown associated with BN. Numerous epidemiological surveys conducted in various African and Asian plantations on recently tapped blocks (less than 10-year-old trees) revealed the nonrandom location of the earliest single diseased trees. These risky areas are mainly characterized by the proximity of a swamp, plantation road, windrow, old bulldozer track, residual forest stump, or slope break. In BN emergence areas, while no significant correlation was found with chemical soil parameters, physical soil analyses (e.g., penetrometer) revealed higher soil compaction often associated with poorer rhizogenesis in BN trees (comparative root counts made in pits close to healthy or BN trees). Furthermore, initial BN symptoms were preferentially observed near the grafted bud at the rootstock/scion junction (RS/S). Numerous comparative ecophysiological measurements of leaf water potential, stem water potential, and predawn base potential using a plant moisture stress (PMS) pressure chamber indicated water stress in BN trees. These results and preliminary dye transfer studies at the RS/S junction suggested a nonoptimal vascular relation between the root system and the trunk of BN trees. In conclusion, compaction-associated reduced water availability of the soil and poor root capacity to meet the water demand during drier dry seasons combined with disturbed sap flows and recurrent local water drainage (latex flows) are now suspected to jointly act as the main exogenous causal stresses that induce the BN process at the RS/S bud zone before spreading upward to the tapping cut. This multidisciplinary approach gives a new comprehensive scenario for the emergence of this multifactorial physiological disease, now suspected to involve cyanide release (1) into the inner phloem of the rubber tree.

References: (1) H. Chrestin. Plant Dis. 88:1047, 2004. (2) D. Nandris et al. Eur. J. For. Pathol. 21:325, 1991. (3) D. Nandris et al. Eur. J. For Pathol. 21:340, 1991. (4) F. Pellegrin et al. Plant Dis. 88:1046, 2004.
Incidence of Viruses Infecting Sweetpotato in Tanzania
Authors: Tairo Fred , Kullaya Alois , Valkonen Jari P. T.
Published: May 2007

A survey for incidence of sweetpotato viruses was carried out in the three sweetpotato-producing districts (Bukoba, Misungwi, and Tarime) in the Lake Victoria basin and in the Indian Ocean coastal zone (Bagamoya on the mainland and Unguja on Zanzibar Island) in Tanzania in March and April 2003. A total of 170 plants from 43 sweetpotato fields were collected, established in an insect-proof screenhouse, and tested for viruses by nitrocellulose membrane enzyme-linked immunosorbent assay (NCM-ELISA). Scions from symptomless plants were grafted onto Ipomoea setosa, a nearly universal indicator plant for sweetpotato viruses, and leaves were tested by NCM-ELISA. Results were confirmed in several seropositive plants by cloning and partial sequencing of the viruses. Sweet potato feathery mottle virus (SPMFV), Sweet potato mild mottle virus, Sweet potato chlorotic stunt virus (SPCSV), and Sweet potato chlorotic fleck virus were detected serologically in single or mixed infections. Frequencies of occurrence of these viruses as determined by serological detection showed SPMFV to be the most prevalent virus in all the surveyed districts. Our study revealed a higher incidence and diversity of viruses in the Lake Victoria basin compared with the Indian Ocean coastal area. These results represent the first survey for sweetpotato viruses in Tanzania using accurate detection methods.
Identification of Eutypa lata by PCR-RFLP
Authors: Rolshausen P. E. , Trouillas F. , Gubler W. D.
Published: May 2007

Eutypa lata is a vascular canker pathogen of woody plants commonly diagnosed by isolating the pathogen from infected tissue. Related fungi from the same family, the Diatrypaceae, also have been found in association with grapevine in Californian vineyards. An in situ polymerase chain reaction (PCR) method has been developed for detection of E. lata in infected wood tissue. However, our results indicate that this method also would amplify other Diatrypaceous fungi, which could potentially lead to an incorrect diagnosis. Therefore, we developed a PCR-restriction fragment length polymorphism (PCR-RFLP) assay. The internal transcribed spacer (ITS)1/5.8S/ITS2 ribosomal DNA region was amplified by PCR using universal primers, and RFLP patterns were determined after digestion with AluI. The restriction profiles obtained served to distinguish E. lata from wood trunk pathogens of grapevine (Phomopsis viticola, Botryodiplodia sp., Phaeoacremonium aleophilum, and Phaeomoniella chlamydospora), Diatrypaceous fungi (Diatrype sp., Diatrypella sp., Eutypella vitis, and Eutypa leptoplaca), and Cryptovalsa sp. found on dead wood of grapevine, and other Eutypa spp. (E.petrakii var. hederae, E. astroidea, E. crustata, and E. lejoplaca), with the exception of E. armeniacae, which we regard as a synonym for E. lata, and E. laevata, which has not been found on grapevine.
The Generation and Quantification of Resistance to Dimethomorph in Phytophthora infestans
Authors: Stein J. M. , Kirk W. W.
Published: May 2007

The generation of dimethomorph resistance in Phytophthora infestans was attempted using ethidium bromide/UV light mutagenesis and repeated culturing on dimethomorph-amended medium. Ethidium bromide/UV mutagenesis created two isolates of P. infestans with resistance factors for dimethomorph >20, i.e., the ratio of the 50% effective concentration (EC50) of the mutant to that of the wild-type. With repeated culturing on dimethomorph-amended medium, the rate of growth (mm diameter/day) increased until the tenth subculture for most P. infestans isolates. Resistance factors generated from repeated culturing were <8 for all isolates. For most isolates, the generation of dimethomorph resistance resulted in reduced growth rates on nonamended medium, regardless of the level of resistance or induction treatment. Additionally, the frequency of infection of leaf disks and whole tubers was significantly reduced in >20% of the isolates repeatedly subcultured on dimethomorph-amended medium. Regardless of the induction treatment, reduced fitness was common for all P. infestans isolates, indicating a potential biological cost associated with dimethomorph resistance. Based on these results, the development of field resistance to dimethomorph in P. infestans is unlikely with the currently employed resistance management strategies.
RAPD-PCR Fingerprinting and Southern Analysis of Xanthomonas axonopodis pv. dieffenbachiae Strains Isolated from Different Aroid Hosts and Locations
Authors: Khoodoo M. H. R. , Jaufeerally-Fakim Y.
Published: May 2007

Anthurium blight, caused by Xanthomonas axonopodis pv. dieffenbachiae, is a systemic disease of Anthurium and other aroids. The aims of this work were to study the genetic diversity among X. axonopodis pv. dieffenbachiae strains and to identify, from the polymerase chain reaction (PCR) profiles, DNA probes that would be specific for the pathovar dieffenbachiae. Twenty-five X. axonopodis pv. dieffenbachiae strains, isolated from different hosts and geographical locations including Mauritius, were fingerprinted using the random amplified polymorphic DNA (RAPD)-PCR technique. The fingerprints were analyzed by the National Taxonomy System Software (NTSYS). The specificity of some of the RAPD fragments selected from PCR profiles was tested by Southern analyses of the PCR products. Ten arbitrary primers were chosen from an initial set of 111 decamers. Two hundred and nine RAPD markers were generated in eight individual DNA profiles. A correlation was found between the serotypes and the RAPD profiles for some groups of isolates. A possible link was also observed between the host range of the isolates tested and their RAPD profiles for strains isolated from Dieffenbachia and Philodendron. These results were confirmed by Southern analysis. Cluster analysis by the unweighted pair group method, arithmetic average (UPGMA) confirmed that the pathovar is genetically diverse with some strains that were clustered together showing similar host preferences. DNA probes with a potential use in molecular diagnostics of Anthurium blight were identified. This preliminary work could be used to develop PCR primers that will enable the sensitive detection of the pathogen in latently infected plants.
Liquid Swine Manure Can Kill Verticillium dahliae Microsclerotia in Soil by Volatile Fatty Acid, Nitrous Acid, and Ammonia Toxicity
Authors: Conn Kenneth L. , Tenuta Mario , Lazarovits George
Published: May 2007

In previous studies, liquid swine manure (LSM) was sometimes shown to reduce Verticillium wilt of potato caused by Verticillium dahliae. We also observed that microsclerotia of this fungus died within 1 day, or between 3 and 6 weeks, after addition of LSM to some acid soils and within 1 week in some alkaline soils. In this study, we demonstrated that a volatile fatty acid (VFA) mixture with an identical concentration of VFAs as that found in an effective LSM reduced germination in an acid soil (pH 5.1) to the same extent as the LSM after 1 day of exposure. Germination was reduced by 45, 75, and 90% in the 10, 20, and 40% ([wt/wt] soil moisture) treatments, respectively, with the latter being equivalent to an application of 80 hl/ha. Addition to this acid soil of 19 LSMs (30% [wt/wt] soil moisture) collected from different producers resulted in complete kill of microsclerotia with 12 manures. Effective manures had a total concentration of nonionized forms of VFAs in soil solution of 2.7 mM or higher. In some acid soils (pH 5.8), addition of LSM (40% [wt/wt] soil moisture) did not kill microsclerotia until 3 to 6 weeks later. Here, a reduction in viability of microsclerotia was attributed to the accumulation of 0.06 mM nitrous acid in the soil solution at 4 weeks. When an LSM was added (40% [wt/wt] soil moisture) to an alkaline soil (pH 7.9) where VFAs are not toxic, microsclerotia germination was reduced by 80% after 1 week. Here the pH increased to 8.9 and the concentration of ammonia reached 30 mM in the soil solution. An ammonium chloride solution having an equivalent concentration of ammonium as the manure was shown to have the same spectrum of toxicity as the manure in assays ranging from pH 7 to 9, both in solutions and above the solutions. At pH 9, the concentration of ammonia reached 18 mM and 100% mortality of microsclerotia occurred. Thus, in acid soils, LSM can kill microsclerotia of V. dahliae by VFA and/or nitrous acid toxicity and in alkaline soils by ammonia toxicity. In order to take advantage of these mechanisms for disease reduction, the manure chemical composition, rate of addition, and soil characteristics need to be determined for each instance of use.
VitisResistance to Pierce's Disease Is Characterized by DifferentialXylella fastidiosaPopulations in Stems and Leaves
Authors: Krivanek A. F. , Walker M. A.
Published: May 2007

The pattern of Xylella fastidiosa infection in resistant and susceptible grapevines representing a diverse selection of Vitis spp. was characterized through measurements of X. fastidiosa bacterial movement and accumulation in artificially inoculated greenhouse-grown grapevines. A double-antibody sandwich enzyme-linked immunosorbent assay (ELISA) was optimized for quantification of X. fastidiosa populations and tested on known amounts of X. fastidiosa added to grape tissue extracts. Predicted versus known X. fastidiosa concentrations proved to be highly correlated (R2= 0.99). Populations of X. fastidiosa in stem internode, stem node, petiole, and leaf blade samples from the genotypes in this study were measured at 12 weeks postinoculation using the optimized ELISA procedure. Samples from each plant part were taken at eight positions along the inoculated shoots. Systemic infection was detected in both susceptible and resistant genotypes. Resistant genotypes were characterized by significant differences in X. fastidiosa populations between stem internodes and leaves (1.0 × 106and 1.1 × 107cells/g of sample, respectively). In contrast, the susceptible genotypes were characterized by high mean X. fastidiosa populations in both stems and leaves (5.6 × 107and 4.8 × 107cells/g, respectively) the latter of which were not significantly different from the resistant genotypes. A high correlation (R2= 0.97) between stem X. fastidiosa numbers to previously characterized field Pierce's disease (PD) performance indicates that the quantitative ELISA measurements of X. fastidiosa in greenhouse-grown grapevines should be a useful tool for predicting PD resistance under field conditions.
Different Resistance Mechanisms of Medicago truncatula Ecotypes Against the Rust Fungus Uromyces striatus
Authors: Kemen Eric , Hahn Matthias , Mendgen Kurt , Struck Christine
Published: May 2007

A pathosystem consisting of the model plant Medicago truncatula and the rust fungus Uromyces striatus was characterized. From a collection of 113 mostly European accessions of M. truncatula, the vast majority were found to be susceptible to U. striatus, whereas 5 accessions showed strong resistance reactions. Stomatal surface characteristics, even if partly occluded, did not interfere with the ability of U. striatus germ tubes to infect. After penetration, the resistant ecotypes reacted with various degrees of cell death during different stages of haustorial establishment. Whereas four ecotypes showed a typical hypersensitive reaction by developing necrotic lesions, one ecotype (F11.008) exhibited a prehaustorial type of defense without hypersensitive response. This ecotype may be used as a source of nonhost-type of resistance against U. striatus.
A One-Step Reverse Transcription-Polymerase Chain Reaction System for the Simultaneous Detection and Identification of Multiple Tospovirus Infections
Authors: Uga Hiroyuki , Tsuda Shinya
Published: May 2007

A one-step reverse transcription-polymerase chain reaction (RT-PCR) method has been developed for the simultaneous detection and identification of multiple tospoviruses that infect plants. The RT-PCR system is composed of six primers in a single tube: a universal degenerate primer and five virus species-specific primers. Amplifications resulted in an 848-bp PCR product for Watermelon silver mottle virus, 709-bp for Tomato spotted wilt virus, 589-bp for Impatiens necrotic spot virus, 511-bp for Melon yellow spot virus, and a 459-bp amplicon for Iris yellow spot virus. This system enables the simultaneous detection of at least three types of tospovirus infections, in addition to their species identities, from five possible tospoviruses studied, on the basis of their S RNA combinations. This multiplex RT-PCR system was applied to the detection of tospovirus in ornamental crops cultivated in fields and shows potential for epidemiological studies.
Genetic Control of Resistance to Tan Necrosis Induced by Pyrenophora tritici-repentis, Races 1 and 2, in Spring and Winter Wheat Genotypes
Authors: Singh P. K. , Hughes G. R.
Published: May 2007

The symptoms of tan spot of wheat, caused by Pyrenophora triticirepentis, include a tan necrosis component and an extensive chlorosis component. Since tan spot has become the major component of the leafspotting disease complex of wheat in western Canada, the need for resistant cultivars has increased. This study was conducted to determine whether the resistance to tan spot found in a diverse set of spring and winter wheat genotypes was due to resistance genes not previously reported. The genetic control of resistance to necrosis induced by P. triticirepentis race 1 and race 2 was determined, under controlled environmental conditions, for spring wheat genotypes Erik and 86ISMN 2137 and winter wheat genotypes Hadden, Red Chief, and 6B-365. Plants were inoculated at the two-leaf stage and disease reaction was assessed based on lesion type. Tests of the F1 and F2 generations, and of F2:3 and F2:8 families, indicated that one recessive gene controlled resistance to the necrosis component of tan spot caused by both race 1 and race 2 in each cross studied. Lack of segregation in crosses between the resistant cultivars indicated that the resistance gene was the same in all of the cultivars.
Relationship Among Genes Conferring Partial Resistance to Leaf Rust (Puccinia triticina) in Wheat Lines CI 13227 and L-574-1
Authors: Lehman Jeffrey S. , Hanson Karin A. , Shaner Gregory
Published: May 2007

This study describes the segregation of genes for resistance to the fungus Puccinia triticina in a cross between partially resistant wheat lines L-574-1 and CI 13227 with two and four genes for resistance, respectively. The objectives of this study were to use parental, F1, F2, and backcross populations to quantify maternal effects, degree of dominance, and transgressive segregation, and to determine whether CI 13227 and L-574-1 share any resistance genes for long latent period or small uredinia. In two experiments conducted in the greenhouse, the uppermost leaf of adult wheat plants was inoculated prior to heading with P. triticina. On days 6 to 21 after inoculation, the number of uredinia that erupted from the leaf surface was counted and used to calculate the mean latent period (MLP). The length and width of five arbitrarily selected uredinia were measured and used to calculate uredinium area. Midparent values, degree of dominance, and broad-sense heritability were calculated for MLP and uredinium area. For experiment A, MLP values for CI 13227, L-574-1, F1, and F2generations were 12.2, 10.5, 10.2, and 10.6 days, respectively. For experiment B, MLP values for CI 13227, L-574-1, F1, F2, backcross to CI 13227, and backcross to L-574-1 were 12.3, 10.0, 10.6, 10.8, 11.1, and 10.0 days, respectively. The inheritance of long latent period was partially recessive, and no maternal effect was present (P = 0.62 to 0.87 for the comparison of means in reciprocal crosses). Broad-sense heritability for MLP ranged from 0.72 to 0.74, and there was transgressive segregation in the F2and backcross populations. Uredinia of the F1generation were slightly larger than uredinia for CI 13227. The inheritance of uredinium size was partially dominant, and no maternal effect was present (P = 0.5 to 0.63). Broad-sense heritability for uredinium area ranged from 0.36 to 0.73 and transgressive segregation was present in the F2and backcross populations. The results for MLP indicate that lines CI 13227 and L-574 likely share one gene for resistance (based on F1values) but not two genes (based on the presence of transgressive segregation). CI 13227 and L 574-1 appear to have at least one gene difference for uredinium area. The linear relationship between uredinium area regressed onto MLP was significant (P < 0.001) and r2values ranged from 0.14 to 0.26. These results indicate that the resistance in CI 13227 and L-574-1 could be combined to create wheat cultivars with greater partial resistance than that possessed by either parent based on MLP or uredinium size.
Isolate-Specific Detection of Grapevine fanleaf virus from Xiphinema index Through DNA-Based Molecular Probes
Authors: Finetti-Sialer M. M. , Ciancio A.
Published: May 2007

Tests with a real-time reverse transcription-polymerase chain reaction (RT-PCR) were performed on specimens of Xiphinema index collected from the rhizosphere of Grapevine fanleaf virus (GFLV)-infected grapevines at Palagiano, Italy. A 1,157-bp fragment of the GFLV RNA-2 coat protein (CP) gene was amplified and sequenced. A fluorescent Scorpion probe was designed to detect a highly conserved CP region. A second region with isolate-specific multiple nucleotide polymorphisms was used to detect GFLV isolates using molecular beacons (MB). The Scorpion probe allowed quantitative estimation of GFLV RNA-2 in single nematodes, using a dilution series of a 692-nucleotide transcript of the CP gene. The assay allowed detection of GFLV RNA-2 in individual X. index, with a minimum template threshold of 800 fg or 2.8 × 106 RNA-2 molecules per nematode. The CP fragment used for GFLV detection with the Scorpion probe appeared highly conserved among isolates. The probes were tested against other GFLV isolates, which were recognized by the species-specific Scorpion probe and by the corresponding MB specific to the particular isolate. Both tests appeared useful as diagnostic tools or for studies on GFLV in acquisition, retention, and transmission experiments.
Toxicity, Pathogenicity, and Genetic Differentiation of Five Species of Fusarium from Sorghum and Millet
Authors: Leslie John F. , Zeller Kurt A. , Lamprecht Sandra C. , Rheeder John P. , Marasas Walter F. O.
Published: May 2007

Fusarium isolates recovered from sorghum and millet are commonly identified as F. moniliforme, but with the recognition of new species in this group, the strains given this name are being re-evaluated. We analyzed five strains each from five Fusarium species (F. andiyazi, F. nygamai, F. pseudonygamai, F. thapsinum, and F. verticillioides) often associated with sorghum and millet for their ability to produce fumonisin and moniliformin, their toxicity to ducklings, and their ability to cause disease on sorghum seedlings in vitro. These species can be distinguished with isozymes (fumarase, NADP-dependent isocitrate dehydrogenase, and malate dehydrogenase) and with banding patterns resulting from amplified fragment length polymorphisms. Two species, F. pseudonygamai and F. thapsinum, produced high levels of moniliformin, but little or no fumonisins, and were consistently highly toxigenic in the duckling tests. Two species, F. verticillioides and F. nygamai, produced high levels of fumonisins, but little or no moniliformin, and also were toxigenic in the duckling tests. F. andiyazi produced little or no toxin and was the least toxigenic in the duckling tests. In sorghum seedling pathogenicity tests, F. thapsinum was the most virulent followed by F. andiyazi, then F. verticillioides, and finally F. nygamai and F. pseudonygamai, which were similar to each other. Thus, these five species, which would once have all been called F. moniliforme, differ sufficiently in terms of plant pathogenicity and toxin production profile, that their previous misidentification could explain inconsistencies in the literature and differences observed by researchers who thought they were all working with the same fungal species.
Influence of Host Diversity on Development of Epidemics: An Evaluation and Elaboration of Mixture Theory
Authors: Skelsey P. , Rossing W. A. H. , Kessel G. J. T. , Powell J. , van der Werf W.
Published: May 2007

A spatiotemporal/integro-difference equation model was developed and utilized to study the progress of epidemics in spatially heterogeneous mixtures of susceptible and resistant host plants. The effects of different scales and patterns of host genotypes on the development of focal and general epidemics were investigated using potato late blight as a case study. Two different radial Laplace kernels and a two-dimensional Gaussian kernel were used for modeling the dispersal of spores. An analytical expression for the apparent infection rate, r, in general epidemics was tested by comparison with dynamic simulations. A genotype connectivity parameter, q, was introduced into the formula for r. This parameter quantifies the probability of pathogen inoculum produced on a certain host genotype unit reaching the same or another unit of the same genotype. The analytical expression for the apparent infection rate provided accurate predictions of realized r in the simulations of general epidemics. The relationship between r and the radial velocity of focus expansion, c, in focal epidemics, was linear in accordance with theory for homogeneous genotype mixtures. The findings suggest that genotype mixtures that are effective in reducing general epidemics of Phytophthora infestans will likewise curtail focal epidemics and vice versa.
Effect of Water, Soil Temperatures, and Exposure Times on the Survival of the Sugar Beet Cyst Nematode, Heterodera Schachtii
Authors: D'Addabbo Trifone , Sasanelli Nicola , Greco Nicola , Stea Vincenzo , Brandonisio Antonio
Published: May 2007

The effect of different combinations of temperatures and exposure times on the mortality of Heterodera schachtii eggs was assessed in two different experiments under laboratory conditions. In the first experiment, cysts in water were exposed to 25, 35, 37.5, 40, 42.5, 45, 47.5, 50, or 52.5°C for a maximum period of 2 h. In the second experiment, cysts in naturally infested soil were exposed to 25, 32.5, 35, 37.5, 40, 42.5, or 45°C for a minimum period of 2 h to a maximum of 2,048 h. Viability of eggs in cysts was assessed by a hatching test in 3 mM zinc chloride solution. Viability in water was suppressed after 2-h exposure at 50°C and inhibited after 1 to 2 h at 52.5°C. Emergence of juveniles from cysts in soil was greater at the lower temperature × exposure time combinations and suppressed at higher combinations. Egg mortality started after exposure for 256 h at 40°C, 32 h at 42.5°C, and 16 h at 45°C, and 81, 31, and 7 h of exposure were necessary to kill 50% of the nematode egg population at 40, 42.5, and 45°C, respectively. The data fitted the models Pt = P010-δt/ (q + mT) and PT1 = PT010-δT/(z - pt) for m = -0.0111, q = 0.8238, z = 2.444, and p = -0.23.
Differences in Feeding Sites Induced by Root-Knot Nematodes, Meloidogyne spp., in Chickpea
Authors: Vovlas Nicola , Rapoport Hava F. , Jiménez Díaz Rafael M. , Castillo Pablo
Published: May 2007

Root-knot nematodes (Meloidogyne spp.) are sedentary, obligate endoparasites in plants, where they induce specialized feeding sites. The feeding sites act as strong metabolic sinks to which photosynthates are mobilized. The histopathological modifications in the nematode-induced feeding sites of artificially inoculated chickpea cv. UC 27 were qualitatively and quantitatively compared using five isolates of M. artiellia and one isolate each of M. arenaria, M. incognita, and M. javanica. All Meloidogyne isolates infected chickpea plants, but root gall thickening was significantly less for M. artiellia isolates than for the other Meloidogyne species. Nevertheless, neither the number of giant cells in the feeding site (averaging four to six) nor the area of individual giant cells was influenced by nematode species or isolate. However, the number of nuclei per giant cell was significantly smaller, and the maximum diameters of nuclei and nucleoli were significantly greater, in giant cells induced by M. artiellia isolates than in those induced by M. arenaria, M. incognita, or M. javanica. In a second experiment, M. artiellia-induced giant cells in faba bean and rapeseed also contained a small number of large nuclei.
Identification of Transcripts Involved in Resistance Responses to Leaf Spot Disease Caused by Cercosporidium personatum in Peanut (Arachis hypogaea)
Authors: Luo M. , Dang P. , Bausher M. G. , Holbrook C. C. , Lee R. D. , Lynch R. E. , Guo B. Z.
Published: May 2007

Late leaf spot disease caused by Cercosporidium personatum is one of the most destructive foliar diseases of peanut (Arachis hypogaea) worldwide. The objective of this research was to identify resistance genes in response to leaf spot disease using microarray and real-time polymerase chain reaction (PCR). To identify transcripts involved in disease resistance, we studied the gene expression profiles in two peanut genotypes, resistant or susceptible to leaf spot disease, using cDNA microarray containing 384 unigenes selected from two expressed sequenced tag (EST) cDNA libraries challenged by abiotic and biotic stresses. A total of 112 spots representing 56 genes in several functional categories were detected as up-regulated genes (log2 ratio > 1). Seventeen of the top 20 genes, each matching gene with known function in GenBank, were selected for validation of their expression levels using real-time PCR. The two peanut genotypes were also used to study the functional analysis of these genes and the possible link of these genes to the disease resistance trait. Microarray technology and real-time PCR were used for comparison of gene expression. The selected genes identified by microarray analysis were validated by real-time PCR. These genes were more greatly expressed in the resistant genotype as a result of response to the challenge of C. personatum than in the susceptible genotype. Further investigations are needed to characterize each of these genes in disease resistance. Gene probes could then be developed for application in breeding programs for marker-assisted selection.