bluuebunny/crossref_metadata_2025 huggingface dataset:
First Report of Impatiens necrotic spot virus in Ornamental Plants in Hungary
Authors: Tóth E. K. , Kriston É. , Takács A. , Bajtek M. , Kazinczi G. , Horváth J.
Published: May 2007

Economically important viruses such as Tomato spotted wilt virus, genus Tospovirus, are transmissible mechanically and mainly by two thrips species (Thrips tabaci and Frankliniella occidentalis) in Hungary (1). Samples (31) of eight ornamental plant species (Catharanthus roseus, Cyclamen persicum, Dendranthema × grandiflorum, Eustoma grandiflorum, Gerbera sp., Impatiens walleriana, Ocimum basilicum, and Verbena hybrida) were studied. Symptoms including color breaking on flowers and necrotic symptoms on leaves were observed on four samples (C. persicum, I. walleriana, O. basilicum, and E. grandiflorum). Infection by Impatiens necrotic spot virus (INSV) was determined by double-antibody sandwich-ELISA and triple-antibody sandwich-ELISA using antisera obtained from Loewe (Sauerlach, Germany) and the DSMZ. Back inoculation with the F. occidentalis vector was also carried out to Lycopersicon esculentum as indicator plants. Back inoculation was also positive for INSV by symptoms and ELISA. The high amount of ornamental plant production together with the use of virus-infected propagation material and the increasing thrips vector populations may result in significantly increased establishment and distribution of INSV in Hungary.

References: (1) M. L. Daughtrey et al. Plant Dis. 81:1220, 1997.
A New Strain of Streptomyces Causing Common Scab in Potato
Authors: Wanner Leslie A.
Published: May 2007

Common scab is a serious disease of potatoes (Solanum tuberosum) and other root and tuber crops, affecting the quality and market value of these crops. The disease is caused by gram-positive soil bacteria in the genus Streptomyces. A new common scab-causing streptomycete was isolated from scabby potatoes originating in southeastern Idaho. Research has supported a model of horizontal transfer of pathogenicity determinants among streptomycetes, and the new strain has hallmarks of the recently characterized Streptomyces pathogenicity island (PAI); it has genes encoding the synthetase for the pathogenicity determinant thaxtomin and for a second pathogenicity factor, tomatinase, although it lacks a third gene characteristic of the Streptomyces PAI, the nec1 gene. The new strain has a unique 16s rDNA gene sequence closely related to those of other pathogenic Streptomyces species. This 16s rDNA sequence was also found in isolates lacking a PAI, suggesting that the new pathogenic strain arose by horizontal transfer of a PAI into a saprophytic streptomycete. Isolates of the new strain are pathogenic on radish and potato, and are more virulent than the S. scabies type strain. In addition to scab lesions on potato tubers, lesions were also seen on underground stems and stolons. This new strain represents additional complexity in the pathogenic strains causing plant disease in the United States.
Saprophytic Colonization of Citrus Twigs by Diaporthe citri and Factors Affecting Pycnidial Production and Conidial Survival
Authors: Mondal S. N. , Vicent A. , Reis R. F. , Timmer L. W.
Published: May 2007

Melanose, caused by Diaporthe citri, produces reddish brown lesions on the fruit, leaves, and twigs of citrus trees, and greatly reduces the marketability of fresh fruit. Most of the inoculum is produced in pycnidia on dead twigs in the tree canopy, which exude large numbers of conidia in slimy masses. In this study, detached twigs inoculated with conidia were readily colonized and produced large numbers of pycnidia within 30 to 40 days when they were soaked 3 to 4 h on alternate days. Conidial production was measured by wetting twigs in a rain tower periodically and collecting the conidia in the runoff water. Production began after 80 days and continued for nearly 300 days. In other experiments, production of mature pycnidia on detached twigs was greatest at 94 to 100% relative humidity (RH) and at 28°C. Low RH and temperature, however, favored survival of conidia in exuded masses on twigs. In the field, colonization of detached twigs by D. citri was high in rainy season, moderate in spring and early fall, and minimal in late fall and winter. Twig colonization was positively related to the number of rain days and average temperature, but not to total rainfall. In another experiment, inoculated twigs placed in the tree canopy developed pycnidia and then produced conidial masses for about 200 days. D. citri is a serious pathogen, but a weak parasite, that survives primarily by colonization and reproduction on dead twigs.
Biological Control of Grape Powdery Mildew Using Mycophagous Mites
Authors: English-Loeb Greg , Norton Andrew P. , Gadoury David , Seem Robert , Wilcox Wayne
Published: May 2007

We evaluated the efficacy of a mycophagous tydeid mite, Orthotydeus lambi, in controlling grape powdery mildew on mature vines of nine different grape cultivars and one unnamed hybrid grown in an experimental vineyard over a 3-year period. O. lambi became well established on all vines where they were released. However, some cultivars supported higher densities than others, depending on, among other factors, the presence and abundance of leaf trichomes in vein axils (domatia). The establishment of O. lambi substantially reduced powdery mildew on foliage and fruit, although the magnitude of disease suppression was greater on some grape genotypes than others, depending on mite density and innate susceptibility to grape powdery mildew. Treatments where O. lambi was used alone were as effective as fungicide. Significantly better disease control was found in treatments with both mites and fungicides. The mass of pruning material and leaf photosynthetic rates were significantly greater for vines with O. lambi, fungicide, or a combination of mites and fungicide compared with untreated vines. The combination of mites and fungicide resulted in significantly greater yield than mites or fungicide alone. Our results illustrate the potential of O. lambi for biological control of grape powdery mildew but also highlight limitations related to differences among grape genotypes in innate susceptibility to mildew and suitability for mites.
Verticillium Wilt Incited by Verticillium dahliae in Lupinus polyphyllus in Italy
Authors: Garibaldi A. , Bertetti D. , Gullino M. L.
Published: May 2007

Lupinus polyphyllus Lindl., a perennial ornamental belonging to the Leguminosae family, is grown in gardens for flower beds and borders. During the summer of 2006, in several gardens located in the Biella Province (northern Italy), a new wilt of Lupine was observed in 20 to 30% of the plants. The vascular tissue in stems of affected plants appeared brown. These plants were stunted and developed yellow leaves with brown or black streaks in the vascular tissue. Verticillium dahliae was consistently isolated from symptomatic vascular tissue and leaves when cultured on potato dextrose agar (PDA) (3). Microscopic observations revealed hyaline hyphae, with many irregular, dark microsclerotia, ranging from 17 to 61 μm. Conidiophores showed two verticils of three elements. Conidia were hyaline, elliptical, single-celled, measuring 3.4 to 6.0 × 1.8 to 3.1 μm (average 4.5 × 2.4 μm). The ITS region (internal transcribed spacer) of rDNA was amplified using the primers ITS4/ITS6 (2) and sequenced. BLASTn analysis (1) of the 521 bp obtained showed an E-value of 0.0 with V. dahliae. The nucleotide sequence has been assigned GenBank Accession No. EF015891. Healthy 30-day-old plants (10 per treatment) of L. polyphyllus were inoculated by root dip with a conidial suspension (0.5 × 106 CFU/ml) of V. dahliae isolated from infected plants. Ten noninoculated plants served as control treatments. All plants were transplanted into pots filled with a mix of sphagnum peat/pomix/pine bark/clay (50:20:20:10) and grown outdoors at temperatures ranging from 15 to 25°C. First wilt symptoms and vascular discoloration in the roots, crown, and veins developed within 20 days on each inoculated plant and become evident after 50 days. V. dahliae was consistently reisolated from infected plants. Noninoculated plants remained healthy. The pathogenicity test was conducted twice. To our knowledge, this is the first report of V. dahliae on L. polyphyllus in Italy. A wilt caused by V. dahliae on L. polyphyllus was observed in the Netherlands in 1925 (4).

References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) D. E. L. Cooke and J. M. Duncan. Mycol. Res. 101:667, 1997. (3) G. F. Pegg and B. L. Brady. Verticillium Wilts. CABI Publishing, Wallingford, UK, 2002. (4) J. H. H. Van der Meer. Meded. Landbouwhogesch. Wagening. 28, 1925.
First Report of Root Rot of American Ginseng (Panax quinquefolium) Caused by Ditylenchus destructor in China
Authors: Zhang G. Z. , Zhang H. W.
Published: May 2007

During the summer of 2004, a root rot was observed on 3- and 4-year-old American ginseng cultivated in the Beijing area, and in 2006, the root rot was also found in the Hebei Province. The root epidermis appeared light brown with irregular lesions in the early stage. Sometimes the lesions had defined edges and were striped. In the later stages of the disease, the roots had splits in the epidermis and a rotted cortex causing them to lose commercial value. Plants wilted when the roots were severely damaged. The diseased roots were assayed for plant parasitic nematodes. A plant parasitic nematode was identified as Ditylenchus destructor on the basis of the following characteristics (1): stylet length ranged from 9.2 to 13.3 μm with rounded knobs; a single anterior outstretched ovary extended toward the base of the esophagus; the developing oocytes existed in two rows, changing to one near the middle of the ovary, and the vulva was thick and elevated, with the posterior uterus extending approximately three-quarters of the distance to the anus; the bursa extended from opposite the anterior end of the spicules approximately three-fourths of the tail length; and the tail was rounded and the lateral field had six incisures. Pathogenicity was tested by inoculating with a 2-ml suspension (approximately 2,000 nematodes) extracted from diseased roots to each of seven intact American ginseng roots. The roots were in a polyethylene bag surrounded by sterile soil and incubated at 25 ± 2°C. On five roots after 60 days, symptoms were similar to those observed in the field, and D. destructor was isolated from the infected parts. The control, inoculated only with sterile water, remained healthy. To our knowledge, this is the first report of D. destructor causing root rot of American ginseng.

Reference: (1) G. Thorne. Proc. Helminthol. Soc. Wash. 12:27, 1945.
First Report of a Natural Infection of Opuntia sp. by a ‘Candidatus Phytoplasma asteris’-Related Phytoplasma in China
Authors: Wei W. , Cai H. , Chen H. , Davis R. E. , Zhao Y.
Published: May 2007

Cacti (Opuntia spp.) are perennial, evergreen, succulent plants native to arid areas of the Americas. Because of their aesthetic appearance, many cacti have been cultivated and introduced to other parts of the world as ornamentals. Cacti are susceptible to phytoplasma infections and develop witches'-broom (WB) disease. Currently, all reported cactus WB cases are associated with infections by phytoplasmas in the peanut witches'-broom group (16SrII) (1,2,4). During a phytoplasma diversity survey carried out during 2004 in Yunnan, China, we collected 29 malformed and 14 healthy-looking naturally occurring cactus plants from 14 locations representing five geographical regions. Each of the 29 malformed plants exhibited stunted growth and possessed clusters of highly proliferating cladodia, typical symptoms of cactus WB disease. Nested-PCR was carried out on the DNA samples extracted from young cladodia of these plants using phytoplasma-universal 16S rDNA primers P1A/P7A and R16F2n/R16R2 (3). Results revealed that all 29 diseased plants that were examined were infected by phytoplasmas, whereas all 14 healthy-looking plants were negative for phytoplasmas. Subsequent restriction fragment length polymorphism (RFLP) analysis of the PCR-amplified 1.25-kb 16S rDNA fragments indicated that 28 diseased plants were infected by a phytoplasma of group 16SrII, whereas one plant (from Suan Village) was infected by a ‘Candidatus Phytoplasma asteris’-related (group 16SrI) phytoplasma designated as strain YN26. Nucleotide sequence analysis of the strain YN26 partial rRNA operon (GenBank Accession No. EF190970), covering a near full-length 16S rRNA gene, a 16S-23S rRNA intergenic spacer, a tRNA-Ile gene, and a partial 23S rRNA gene, suggested that this phytoplasma is most closely related to an ash witches'-broom phytoplasma (GenBank Accession No. AY566302, 99.7% identity) and an epilobium phyllody phytoplasma (GenBank Accession No. AY101386, 99.7% identity), both members of subgroup16SrI-B. This YN26-infected cactus plant was transferred to a greenhouse and maintained for more than 2 years, during which time DNA samples were extracted and tested two additional times. The same 16S rDNA RFLP pattern type was consistently obtained in these tests, confirming that the plant remained infected by the 16SrI phytoplasma. To our knowledge, this is the first report of a natural infection of a cactus species by a group 16SrI phytoplasma. Since this 16SrI-cactus WB phytoplasma was found in the same geographical location where 16SrII-cactus WB phytoplasma was detected both in this and a previous study (1), the findings raised the question whether 16SrI- and 16SrII-cactus WB phytoplasmas have overlapping geo- and bioecological niches.

References: (1) H. Cai et al. Plant Pathol. 51:394, 2002. (2) E. Choueiri et al. Plant Dis. 89:1129, 2005. (3) I. M. Lee et al. Int. J. Syst. Evol. Microbiol 54:337, 2004. (4) N. Leyva-Lopez et al. Phytopathology (Abstr.) 89(suppl):S45, 1999.
First Detection of Grapevine leafroll associated virus-7 in California Vineyards
Authors: Morales R. Z. , Monis J.
Published: May 2007

Grapevine leafroll is one of the most important viral diseases in grapevine and occurs wherever grapevines are grown. At least nine different Grapevine leafroll associated viruses (GLRaVs) belonging to different genera within the Closteroviridae family have been reported. Typical leafroll symptoms include downward rolling and interveinal reddening or yellowing of leaves, reduced fruit size, sugar content, and yield. Our laboratory has detected the presence of GLRaV-7 in many grapevine cuttings collected in California vineyards. During the 2005-2006 fall/winter testing season, symptomatic and asymptomatic grapevine varieties collected from different vineyards in California were tested for the detection of economically important viruses and processed for reverse transcription (RT)-PCR and ELISA. The RT-PCR assays using primers specifically designed for the detection of GLRaV-7 (C. Turturo et al., 13th ICVG [Abstr.], 2000) amplified a single band of approximately 200 bp in samples from selections of Chardonnay, Merlot, Pinot Noir, and Sauvignon Blanc cultivars. The same samples showed low or no reactivity to GLRaV-7 specific antibodies (BIOREBA AG, Reinach, Switzerland). The variability of detection by ELISA can be due to the lower sensitivity of ELISA as compared with RT-PCR and the uneven distribution of GLRaVs in grapevines (1). To confirm that the amplified DNA was GLRaV-7 specific, different isolates were sequenced and compared with the nucleotide and derived amino acid sequences obtained by Turturo et al. (13th ICVG [Abstr.], 2000). The California isolates showed 81 to 98% similarity with the Italian isolates. To our knowledge, this is the first report of GLRaV-7 in California and the United States. Our initial testing data indicates that GLRaV-7 is wide spread in California vineyards. Further studies will allow us to determine the potential effect of this virus in grapevines grown in California.

Reference: (1) J. Monis, and R. K. Bestwick. Am. J. Enol. Vitic. 47:199, 1996.
Lack of Seed Coat Contamination withCucumber mosaic virusin Lupin Permits Reliable, Large-Scale Detection of Seed Transmission in Seed Samples
Authors: O'Keefe Donna C. , Berryman David I. , Coutts Brenda A. , Jones Roger A. C.
Published: May 2007

Sowing seed stocks with minimal virus content provides a key control measure in preventing damaging epidemics of Cucumber mosaic virus (CMV) in crops of narrow-leafed lupin (Lupinus angustifolius). A seed testing service provides an estimate of percent CMV infection based on a dry seed test in which bulked subsamples of ungerminated seed are ground to a fine powder for testing. When enzyme-linked immunosorbent assay (ELISA) was used, CMV antiserum that gave low background optical density (A405) values with extracts of powder from subsamples of healthy seed provided greatest accuracy, readily detecting one infected seed in subsamples of 100 seeds. In comparative ELISAs on duplicate subsamples from eight different seed stocks, germination and dry seed tests always gave similar percent infection values. When seed coats were separated from the embryos of CMV-infected and healthy lupin seeds before testing by ELISA, the virus was only detected in embryos from infected seeds and never in their seed coats. Treatment with trisodium phosphate did not alter the low ELISA optical density (A405) values obtained with seed coats separated from infected seeds. Therefore, seed coat contamination with CMV is lacking in lupin, justifying large-scale routine use of a dry seed test to estimate percent virus infection in commercial seed samples.
Effects of Border Crops and Intercrops on Control of Cucurbit Virus Diseases
Authors: Damicone J. P. , Edelson J. V. , Sherwood J. L. , Myers L. D. , Motes J. E.
Published: May 2007

In five field trials over 3 years, control of aphid-transmitted, nonpersistent virus diseases on pumpkin, caused mostly by the potyviruses Watermelon mosaic virus (WMV) and Papaya ringspot virus type-W (PRSV-W), was achieved by intercropping with grain sorghum, as opposed to clean tillage. Reductions in disease incidence ranged from 43 to 96% (P ≤ 0.05). Surrounding pumpkin plots with borders of peanut, soybean, or corn was not effective. Borders of grain sorghum were effective, but disease control was generally less than for the intercrop treatment. Intercropping soybean and peanut with pumpkin reduced disease incidence by 27 to 60% (P ≤ 0.05), but disease control generally was less than for grain sorghum. Peak periods of alate aphid immigration generally preceded virus disease outbreaks by 7 to 14 days. However, alate landing rates, as measured in green tile traps, did not differ among treatments. Marketable yield was not increased by the intercrop treatments, and yield was reduced by up to 50% for the intercrop treatment with grain sorghum in two trials. The use of grass-selective herbicide applied along pumpkin rows, reduced seeding rates of the intercrops, or mowing did not alleviate the adverse effects of competition between pumpkin and the grain sorghum intercrop on yield.
Genotypes A and B of Cadophora gregata Differ in Ability to Colonize Susceptible Soybean
Authors: Tabor G. M. , Tylka G. L. , Bronson C. R.
Published: May 2007

Growth chamber experiments were conducted to determine if extent of colonization of soybean stems by genotypes A and B of Cadophora gregata (Phialophora gregata), the causal agent of brown stem rot (BSR) of soybean, is similar in soybean plants resistant or susceptible to genotype A. Upon introduction of the two genotypes separately into the base of stems of 2-week-old seedlings, genotype A advanced with the growing tips of susceptible but not resistant genotypes. In contrast, genotype B did not advance with the growing tips of either resistant or susceptible soybean. In similar experiments, 5 weeks after introduction of genotype A, both mean percent stem length colonized by C. gregata and mean percentage of symptomatic trifoliate leaflets were significantly less for resistant than for susceptible genotypes. For genotype B, there was no or a slight difference between resistant and susceptible soybean genotypes in mean percent stem length colonized and no difference in mean percentage of symptomatic trifoliate leaflets 5 weeks after introduction of the pathogen. These results indicate that genotype A and genotype B differ not only in the severity of foliar symptoms they cause on genotype A-susceptible soybean plants, but also in how severely they colonize the stems of these soybean plants. In our experiments, genotype A and genotype B did not differ consistently in their ability to cause internal stem discoloration. The two genotypes of C. gregata can be distinguished based on how severely they colonize stems of genotype A-susceptible soybean. Thus, a BSR resistance screening method, which relies on assessment of stem colonization by C. gregata, works only for screening soybean lines resistance to genotype A. In light of these results, it is important to distinguish soybean resistance to genotype A versus genotype B of C. gregata. Whether genotype B causes yield loss and whether soybean plants can be distinguished as resistant or susceptible to genotype B needs to be investigated.
Natural and Experimental Host Range of Sirococcus clavigignenti-juglandacearum
Authors: Ostry M. E. , Moore M.
Published: May 2007

The fungus Sirococcus clavigignenti-juglandacearum causes butternut canker in North America and is not known to kill or seriously affect tree species other than butternut (Juglans cinerea). However, this putative exotic pathogen has been found on branches of black walnut (J. nigra) and heartnut (J. ailantifolia var. cordiformis), raising questions regarding the potential host range of the pathogen and its spread to new areas on tree hosts other than butternut. Results of artificial inoculations of several hardwood species indicated that the pathogen, although not causing lethal cankers, has the ability to colonize and survive in the wood of several genera, including Quercus, Carya, Corylus, Prunus, and Castanea. Several commercially important Persian walnut (J. regia) cultivars tested were moderately or highly susceptible, underscoring the importance of preventing the movement of the pathogen into commercial Juglans plantations in California, where its ability to cause disease and damage trees is unknown. Evidence for the presence of variation in aggressiveness among isolates of S. clavigignenti-juglandacearum was detected based on differences in canker lengths resulting from inoculations with two isolates of the pathogen. In a field test of several previously named butternut cultivars, all were found to be highly susceptible to the disease, calling into question the value of these selections for nut production or future restoration uses.
A Real-Time, Quantitative PCR Seed Assay for Botrytis spp. that Cause Neck Rot of Onion
Authors: Chilvers Martin I. , du Toit Lindsey J. , Akamatsu Hajime , Peever Tobin L.
Published: May 2007

A real-time fluorescent polymerase chain reaction (PCR) assay was developed using SYBR Green chemistry to quantify the Botrytis spp. associated with onion (Allium cepa) seed that are also able to induce neck rot of onion bulbs, i.e., B. aclada, B. allii, and B. byssoidea. The nuclear ribosomal intergenic spacer (IGS) regions of target and nontarget Botrytis spp. were sequenced, aligned, and used to design a primer pair specific to B. aclada, B. allii, and B. byssoidea. Primers and amplification parameters were optimized to avoid amplifying the related species B. cinerea, B. porri, and B. squamosa, as well as Sclerotinia sclerotiorum and isolates of 15 other fungal species commonly found associated with onion seed. The primers reliably detected 10 fg of genomic DNA per PCR reaction extracted from pure cultures of B. aclada and B. allii. Conventional assays of surface-disinfested and nondisinfested seed on an agar medium were used to determine the incidence of neck rot Botrytis spp. associated with each of 23 commercial onion seed lots, and the real-time PCR assay was used to determine the quantity of DNA of neck rot Botrytis spp. in each seed lot. A linear relationship could not be found between the incidence of seed infected with the neck rot Botrytis spp. using the conventional agar seed assays and the quantity of DNA of the neck rot Botrytis spp. detected by the real-time PCR assay. However, the real-time PCR assay appeared to be more sensitive than the conventional agar assay, allowing detection of neck rot Botrytis spp. in 5 of the 23 seed lots that tested negative using the conventional agar seed assay.
Incidence and Distribution of Important Viral Pathogens in Some Iranian Potato Fields
Authors: Pourrahim R. , Farzadfar Sh. , Golnaraghi A. R. , Ahoonmanesh A.
Published: May 2007

From a total of 8,135 potato leaves collected from 132 fields in 11 provinces of Iran, the incidence and distribution of Alfalfa mosaic virus (AlMV), Eggplant mottled dwarf virus (EMDV), Potato leafroll virus (PLRV), Potato virus A (PVA), Potato virus M (PVM), Potato virus S(PVS), Potato virus X (PVX), Potato virus Y (PVY), and Tomato yellow fruit ring virus (TYFRV) were assessed using serological and biological methods. Based on enzyme-linked immunosorbent assay (ELISA) results, viruses in decreasing order of incidence in potato were PVS (35.9%), PVY (34.4%), PVA (27.0%), PVX (20.8%), PLRV (13.9%), PVM (9.0%), AlMV (7.0%), TYFRV (5.9%), and EMDV (5.1%). All 132 fields surveyed had some degree of virus infection, ranging from 28.8 to 98.6%, with an overall incidence of 75.2%. The highest and lowest incidence of virus infections among the surveyed provinces occurred in Kerman (93.2%) and Ardabil (56.7%), respectively. Overall, 25.0 and 50.2% of the collected potato samples had single or mixed infections, respectively. High levels of mixed infections were found between PVX and PVS (8.6%), and PVX and PVY (7.6%). Moreover, co-infection of samples with PVS and PVY, PVA and PVS, and PVA and PVY, the aphid-vectored virus/virus combinations, occurred at the highest incidence in almost all provinces surveyed, 15.3, 13.8, and 12.8%, respectively. In this study, Beet curly top virus was detected in symptomatic potato samples collected from some fields in the Kermanshah province.
First Occurrence of Anthracnose Caused by Colletotrichum gloeosporioides on Pitahaya
Authors: Palmateer A. J. , Ploetz R. C. , van Santen E. , Correll J. C.
Published: May 2007

Pitahaya, Hylocereus undatus Britt. & Rose, is a columnar, climbing cactus that produces a commercially important fruit. In December 2004, a new disease was found on the crop in Miami-Dade County, FL. Reddish brown lesions with conspicuous chlorotic haloes developed concentrically on the edges of vine ribs. Lesion centers became white and coalesced to rot much of the vine column, and in severe cases, only the vascular column in the vine center was not diseased. Salmon-colored spores and waxy, subepidermal acervuli, typically with setae and simple, short, erect conidiophores, were observed in lesion centers. Tissue from lesion margins was surface disinfested and plated on potato dextrose agar (PDA; Difco Laboratories, Detroit, MI). Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. was isolated from all samples. Colonies produced abundant conidia that were hyaline, one celled, straight, cylindrical, and averaged 14.7 × 5.0 μm with ranges of 12.5 to 17.5 × 3.8 to 7.5 μm (1). Cultural and morphological characteristics of isolates matched those for C. gloeosporioides except for appressoria and hyphopodia (1,2); pitahaya isolates had a spherical rather than lobed hyphopodia reported for C. gloeosporioides and averaged 10.9 (8.5 to 12.7) × 9.1 (7.1 to 10.3) μm. Internal transcribed spacer sequences for the pitahaya isolates were nearly identical (98% homology) to those for C. gloeosporioides isolates occurring on Euphatorium thymifolia in Thailand (GenBank Accession No. AY266393). Koch's postulates were examined in greenhouse trials at the Tropical Research and Education Center, Homestead, FL. Treatments consisted of a noninoculated control, four C. gloeosporioides isolates, and an Alternaria sp. All isolates came from symptomatic pitahaya tissue collected in Miami-Dade County. Fungi were grown on PDA for 7 days at 27°C. A sterile dissecting needle was used to gently pinprick the epidermis of the stem and 2-mm-diameter plugs of C. gloeosporioides, an Alternaria sp., or clean PDA were placed over wounds. Plants were placed in a plastic tent in a greenhouse where the temperature was held at 25°C, and free moisture was maintained on plant surfaces with a household humidifier for 48 h following inoculation. Two isolates of C. gloeosporioides were shown, in repeated greenhouse experiments, to cause reddish brown lesions with conspicuous chlorotic haloes that coalesced to rot much of the vine column, and Koch's postulates were completed with the reisolation of isolates that were used to inoculate plants. The age of vine segments had no significant effect on lesion development. To our knowledge, this is the first report of C. gloeosporioides as a pathogen of pitahaya.

References: (1) J. A. Bailey and M. J. Jeger. Colletotrichum: Biology, Pathology and Control. CAB International, Wallingford, UK, 1992. (2) M. Du et al. Mycologia 97:641, 2005.
Phytophthora Species in Soils Associated with Declining and Nondeclining Oaks in Missouri Forests
Authors: Schwingle B. W. , Juzwik J. , Eggers J. , Moltzan B.
Published: May 2007

Periodic episodes of oak decline have occurred in the Missouri Ozark forests since the early 1900s and the disease is currently severe (2). Several Phytophthora spp. contribute to oak decline in Europe (1), but the role of Phytophthora spp. in oak decline in the eastern United States is not known. Mineral soils collected around the bases of declining and nondeclining oaks in paired sites in central Missouri forests were assayed for the presence of these taxa by baiting flooded soil with Quercus robur leaves. Q. rubra and Q. velutina were the oak species on three sites and Q. alba was on the fourth. Isolates from symptomatic baits plated on PARPNH selective medium were identified tentatively on classical taxonomic characteristics. Five isolates of P. cambivora, two of P. quercina, and eight of P. cinnamomi were obtained from soils around one, one, and three trees, respectively, on decline sites. The internal transcribed spacer sequences for each isolate were compared to those in GenBank; BLAST searches for all isolates had nucleotide identities of 99% and E values of 0, which confirmed the identifications. Greenhouse pot trials were conducted to assess pathogenicity of isolates on stems of 2-year-old Q. alba and Q. rubra. A mycelial agar plug was inserted into a 1-cm long slit cut into the cambium 5 cm above the root collar and covered with sterile, moist cotton and wrapped with laboratory film. The treatments included two isolates of P. cambivora, one of P. quercina, three of P. cinnamomi, and a sterile agar plug. Each host × isolate combination was replicated four times, and the experiment was conducted twice in the greenhouse (natural lighting; temperature ≤32°C in summer and ≥7°C in winter). Stem lesions were produced commonly by P. cambivora (28 of 32 seedlings) and P. cinnamomi (46 of 48 seedlings) within 3 months; none was found on control seedlings or those inoculated with P. quercina. Mean lengths (cm) of lesions caused by P. cinnamomi were greater for Q. rubra (5.6) than for Q. alba (4.3) and lesion lengths for P. cambivora were greater for Q. alba (5.2) than for Q. rubra (4.4). Seven Q. alba seedlings inoculated with P. cambivora and one Q. alba inoculated with P. cinnamomi died before 3 months. All Phytophthora species were recovered from inoculated stems at 3 months except that P. quercina was not recovered in one trial. To our knowledge, this is the first report of Phytophthora species in soils of Missouri oak forests, of P. quercina in the United States, and of the ability of P. cambivora to cause stem lesions on Q. alba. P. cinnamomi and P. cambivora should be investigated in situ as possible contributing factors of oak decline in Missouri.

References: (1) T. Jung et al. Plant Pathol. 49:706, 2000. (2) R. Lawrence et al. MO. Conserv. 63:11, 2002.
First Report of Powdery Mildew Caused by Golovinomyces orontii (Erysiphe orontii) on Lamium galeobdolon in Italy
Authors: Garibaldi A. , Bertetti D. , Minerdi D. , Gullino M. L.
Published: May 2007

Lamium galeobdolon L. (Labiatae) is a common ornamental species that grows in shade areas and often used as a ground cover in gardens. During the summer of 2006, severe outbreaks of a previously unknown powdery mildew were observed on all Lamium spp. plants in some gardens near Biella (northern Italy). Both surfaces of the leaves of affected plants were covered with dense, white mycelia and conidia. As the disease progressed, infected leaves turned yellow and died. Mycelia and conidia also were observed on stems and flowers. Conidia were hyaline, ellipsoid, borne in short chains (with a maximum of five conidia per chain), and measured 29 to 37 × 16 to 20 μm (average 33 × 18 μm). Conidiophores, 91 to 104 μm (average 96 μm) long, showed the foot cell measuring 28 to 49 × 9 to 11 μm (average 38 × 10 μm), followed by three shorter cells measuring 14 to 26 × 9 to 15 μm (average 21 × 11 μm). Fibrosin bodies were absent. Chasmothecia were not observed in the collected samples. The internal transcribed spacer region (ITS) of rDNA was amplified using the primers ITS4/ITS6 (4) and sequenced. BLASTn analysis (1) of the 436 bp obtained showed an E-value of 0.0 with Golovinomyces orontii (Erysiphe orontii.) (3). The nucleotide sequence has been assigned GenBank Accession No. EF 121871. Inoculations were made by gently pressing diseased leaves onto leaves of five healthy L. galeobdolon plants. Five noninoculated plants served as controls. Inoculated and noninoculated plants were maintained in a greenhouse at temperatures between 15 and 28°C. After 10 days, typical powdery mildew colonies developed on inoculated plants. Noninoculated plants did not show symptoms. The pathogenicity test was carried out twice. To our knowledge, this is the first report of the presence of powdery mildew on L. galeobdolon caused by G. orontii in Italy. Blumer (2) was able to reproduce powdery mildew symptoms on L. galeobdolon using populations from cucumber, while Braun (3) reported L. galeobdolon as a possible host of E. orontii. Herbarium specimens of this disease are available at AGROINNOVA Collection, University of Torino, Italy.

References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) S. Blumer. Ber. Schweiz. Bot. Ges. 62:384, 1952. (3) U. Braun. A Monograph of the Erysiphaceae (Powdery Mildews). Cramer, Berlin, GDR, 1987. (4) D. E. L. Cooke and J. M. Duncan. Mycol. Res. 101:667, 1997.
First Report of the Foliar Nematode Aphelenchoides ritzemabosi Infecting Chrysanthemum in Iran
Authors: Deimi A. Mohammad , Barouti S. , Rius J. E. Palomares , Castillo P.
Published: May 2007

During a nematode survey on cut flowers in the Pakdasht Region, Tehran Province, Iran, a species of foliar nematode belonging to the genus Aphelenchoides Fischer was detected in leaves of 10- to 11-month-old, greenhouse-grown (26 to 28°C) chrysanthemum (Dendranthema grandiflorum Kitam., cv. Puja) plants. Chrysanthemum leaves appeared discolored and slightly deformed. Diseased plants comprised approximately 40% of all plants in the greenhouse and occurred in scattered clumps along irrigation paths. Spots and blackish brown, irregular, necrotic areas occupied 5 to 50% of the leaf surface. Symptomatic tissue contained females, males, juveniles, and embryonated eggs of the nematode. All life stages of the nematode were detected in the mesophyll of younger and older infected leaves. The nematode population was extracted and quantified from symptomatic samples of 5 g of leaf tissues by modified Baermann funnel extraction and from 250 g of soil with a modification of the sugar centrifugal flotation method (1), counted, and identified. Morphological observations showed four incisures in the lateral field, excretory pore posterior to nerve ring, ovary single with oocytes in multiple rows, post-vulval uterine sac extending more than one-half of the vulva-anus distance, often containing sperm, tail elongate-conoid bearing a terminal peg with 2 to 4 minute processes. Males common (40% of females) posteriorly curved through 180° upon relaxation, tail conoid bearing a terminal peg with 2 to 3 processes. Measurements of 14 females and 11 males (body length = 987 ± 48 μm, a = 49.2 ± 4.4, b = 12.3 ± 1.1, c = 20.6 ± 2.8, V = 71 ± 1.7, T = 49 ± 2.3, stylet length = 12.6 ± 0.6 μm, tail length = 47.9 ± 5.2 μm; position of vulva = 70.8 ± 1.7%; spicules length = 22.8 ± 1.4 μm) conformed to the description of the chrysanthemum foliar nematode Aphelenchoides ritzemabosi (Schwartz) Steiner & Buhrer, (2). Voucher specimens have been deposited in the University of California Davis Collection. An average of 1,064 A. ritzemabosi per gram were found in the leaves of chrysanthemum, while only 48 nematodes were detected in the soil. To our knowledge, this is the first report of A. ritzemabosi infecting chrysanthemum plants in Iran.

References: (1) W. A. Coolen. Page 317 in: Root-Knot Nematodes (Meloidogyne Species) Systematics, Biology, and Control. F. Lamberti and C. E. Taylor, eds., Academic Press, New York, 1979. (2) N. Vovlas et al. Nematology 7:301, 2005.
First Report of Rust Caused by Tranzschelia discolor on Peach in Oman
Authors: Deadman M. L. , Al Maqbali Y. , Al Subhi A. , Al Yahyai R. , Al Sa'di A. , Aime M. C.
Published: May 2007

Peach (Prunus persica L.) is the primary fruit crop in parts of the northern mountainous regions of Oman. Local cultivars, propagated by seedling, are used to produce fruit for local markets and shade fodder crops planted underneath the peach canopy. In February of 2006, leaf samples showing rust signs and symptoms were collected from Balad Seet, 120 km southwest of Muscat. Angular, yellow spots were observed on leaf upper surfaces with orange sori on the undersides. The disease was observed to be affecting almost 100% of trees, with many leaves having more than 10 sori per leaf. Lesions producing urediniospores were also observed on twigs where spring growth had cracked. Urediniospores typical of Tranzschelia discolor (Fuckel) Tranzschel & M.A. Litv. were obovoid, echinulate, orange-brown, and measured on average 13 to 17 × 26 to 37 μm, with the cell wall 1.3 to 1.8 μm thick at the sides and as much as 5.8 μm thick at the apex. Golden capitate paraphyses were also present, measuring on average 35 to 57 μm long, head 13 to 16 μm in diameter, and tail 4.9 to 6.7 μm wide. Teliospores were not observed because of the time of year of collection. Pathogen identity was confirmed by analysis of a nuclear rDNA sequence spanning from the 5.8S through the ITS-2 into the first 1,000 bp of the 28S gene (1). A voucher specimen was deposited in the U.S. National Fungus Collection (BPI 875341). The voucher's rDNA sequence deposited in GenBank (Accession No. DQ995341) shared 100% sequence similarity with T. discolor (Accession No. DQ354542). Although T. discolor has a worldwide distribution (2), it has not previously been reported from Oman. Improving the quality of peach production in Oman is an agricultural priority because it boosts the economy of smallscale farms in the mountainous regions. This work will facilitate the current research aimed at evaluating cultivar response to rust disease.

References: (1) M. C. Aime. Mycoscience 47:112, 2006. (2) P. F. Bertrand. Rust. Page 23 in: Compendium of Stone Fruit Diseases. J. M. Ogawa et al., eds. The American Phytopathological Society, St Paul, MN, 1995.
Fusarium Wilt of Gerbera in Spain in Soilless Crops
Authors: Garibaldi A. , Minuto A. , Prados-Ligero A. M. , Melero-Vara J. M. , Gullino M. L.
Published: May 2007

In 2004, gerbera (Gerbera jamesonii cv. Excellence) plants, grown for cut flowers, were observed in a soilless cultivation system (coconut fiber substrate) in one farm in the Cadiz area (southwestern Spain) exhibiting symptoms of a wilt disease. Gerbera represents a relevant crop for the industry in the region, after rose and carnation. Affected plants were stunted and developed yellow leaves with initially brown and eventually black streaks in the vascular system. The vascular streaks in the yellow leaves were continuous with a brown discoloration in the vascular system of the crown and upper taproot. In some cases, the leaves of affected plants turned red. Fusarium spp. was consistently and readily isolated from symptomatic vascular tissue of infected plants onto a Fusarium-selective medium (3). Colonies were identified as F. oxysporum after subculturing on potato dextrose agar on the basis of morphological observations. Pathogenicity tests were carried out by using two monoconidial isolates, compared with an Italian one, obtained from wilted gerbera plants. Each isolate of F. oxysporum was grown in shake culture (90 rpm) for 10 days on casein hydrolysate at 25°C with 12 h of fluorescent light per day. Healthy rooted 30-day-old plants (cv. Jaska), were inoculated by dipping roots into a conidial suspension (5 × 107 conidia/ml) in one of the three test isolates of F. oxysporum. Plants were transplanted (1 plant per pot) into pots (3.5 liter vol.) containing rockwool-based substrate. Noninoculated plants served as control treatments. Plants (15 per treatment) were grown in a glasshouse at an average day temperature of 30°C and night temperature of 24°C (minimum of 22°C and maximum of 41°C). Wilt symptoms and vascular discoloration in the roots, crown, and veins developed within 30 days on each inoculated plant, while noninoculated plants remained healthy. F. oxysporum was consistently reisolated from infected plants. The pathogenicity test was conducted twice. A wilt of gerbera was described in the Netherlands in 1952 (1) but its presence was not confirmed in further observations (4). Gerbera wilt was recently reported in Italy (2) and identified as F. oxysporum f. sp. chrysanthemi (A. Garibaldi, personal communication). Currently, the wilt of gerbera in Spain is limited to a few farms and a very limited percent (2 to 3%) of plants.

References: (1) J. Arx and J. A. von Tijdschr. PlZiekt. 58:5, 1952. (2) A. Garibaldi et al. Plant Dis. 88:311, 2004. (3) H. Komada. Rev. Plant Prot. Res. 8:114, 1975. (4) G. Scholten. Neth. J. Plant Pathol. 76:212, 1970.
Potato Late Blight in the Columbia Basin: An Economic Analysis of the 1995 Epidemic
Authors: Johnson D. A. , Cummings T. F. , Hamm P. B. , Rowe R. C. , Miller J. S. , Thornton R. E. , Pelter G. Q. , Sorensen E. J.
Published: May 2007

The cost of managing late blight in potatoes during a severe epidemic caused by new, aggressive strains of Phytophthora infestans in the Columbia Basin of Washington and Oregon in 1995 was documented. The mean number of fungicide applications per field varied from 5.1 to 6.3 for early- and midseason potatoes, and from 8.2 to 12.3 for late-season potatoes in the northern and southern Columbia Basin, respectively. In 1994, a year when late blight was not severe, the mean number of fungicide applications per field made to early- and midseason potatoes was 2.0; whereas late-season potatoes received a mean of 2.5 applications. The mean per acre cost of individual fungicides applied varied from $4.90 for copper hydroxide to $36.00 for propamocarb + chlorothalonil. Total per acre expenses (application costs plus fungicide material) for protecting the crop from late blight during 1995 ranged from $106.77 to $110.08 for early and midseason potatoes in different regions of the Columbia Basin and from $149.30 to $226.75 for lateseason potatoes in the northern and southern Columbia Basin, respectively. Approximately 28% of the crop was chemically desiccated before harvest as a disease management practice for the first time in 1995, resulting in an additional mean cost of $34.48/acre or $1.3 million for the region. Harvested yields were 4 to 6% less than in 1994. The total cost of managing late blight in the Columbia Basin in 1995 is estimated to have approached $30 million.
Sensitivity of Venturia inaequalis Isolates to Fungicides Used in Lebanon
Authors: Al-Arab H. G. Diab , Abou-Jawdah Y.
Published: May 2007

Apple scab, caused by Venturia inaequalis (Cooke) G. Wint. is one of the major apple diseases worldwide. In 1994, the disease caused severe losses particularly in apple orchards of the Akkar mountainous areas of Lebanon, although more than 10 fungicide sprays were applied. A total of 230 isolates of V. inaequalis were collected from 23 orchards and single-spore colonies were prepared. The orchards were selected to represent the major apple-growing areas in Lebanon: Akkar in the north, Kfardibian in northeast Beirut, and Barouk in southeast Beirut. In vitro tests were conducted to evaluate the level of resistance to benzimidazoles and sterol biosynthesis inhibitors (SBI). All isolates tested except one were resistant to benomyl and thiophanate-methyl at 1 μg/ml. The majority of isolates were not inhibited at concentrations as high as 50 μg/ml in mycelial growth. Similarly, the majority of the isolates were not inhibited by benomyl at 1, 5, and 50 μg/ml in spore germination tests. Preliminary in vivo tests with benomyl concerning resistance to benzimidazoles correlated well with in vitro results. All the isolates were inhibited by fenari-mol at 0.25 μg/ml (1) indicating that all the isolates can be considered sensitive to this fungicide. However, the sensitivity levels varied among the various isolates with the ED50 for fenarimol ranging between 0.002 and 0.052 μg/ml. Two new SBIs, bromocunazol and fenbuconazol, not registered for use in Lebanon at the time this study was performed, were also tested. Their ED50 ranged from 0.0089 to 0.025 μg/ml for bromocunazol and from 0.008 to 0.039 μg/ml for fenbuconazol, both indicating a good level of in vitro activity. These results indicate that resistance to benzimidazol is widespread in Lebanon while resistance to SBIs has not yet been detected.

Reference: (1) W. Köller et al. Plant Dis. 75:726, 1991.
Restriction Fragment Length Polymorphism Analyses of Iranian Strains of Xanthomonas campestris from Cereals and Grasses
Authors: Alizadeh A. , Arlat M. , Sarrafi A. , Boucher C. A. , Barrault G.
Published: May 2007

Restriction fragment length polymorphism (RFLP) analyses of the genomic DNA of 45 Xanthomonas campestris strains from cereals and grasses in Iran, and of 17 reference strains, were performed using two probes originating from X. campestris and including hrp genes. The Iranian strains studied belonged to three clearly distinct RFLP groups related to the grouping previously established on the basis of biochemical and physiological characters and host range. RFLP group 1 encompassed all the strains pathogenic to barley but not to the other plants tested (i.e., wheat, rye, Bromus inermis, Lolium multiflorum, Agropyron elongatum, and oat). RFLP group 2 contained strains that are pathogenic to all the above mentioned plants except oat. One strain, which has the same host range as group 2, was classified as RFLP group 3. Reference strains were distributed over these three groups, independently of their geographical origin. Strains in groups 1 and 3 had highly conserved RFLP patterns. In contrast, group 2 strains were easily split into two RFLP subgroups, although they did not differ significantly for other characters. The data suggest that RFLP analysis is a useful tool to distinguish among X. campestris strains causing bacterial leaf streak of cereals.