bluuebunny/crossref_metadata_2025 huggingface dataset:
First Report of a Group 16SrII Phytoplasma Infecting Chickpea in Oman
Authors: Al-Saady N. A. , Al-Subhi A. M. , Al-Nabhani A. , Khan A. J.
Published: May 2007

Chickpea (Cicer arietinum), locally known as “Dungo”, is grown for legume and animal feed mainly in the interior region of Oman. During February 2006, survey samples of chickpea leaves from plants showing yellows disease symptoms that included phyllody and little leaf were collected from the Nizwa Region (175 km south of Muscat). Total nucleic acid was extracted from asymptomatic and symptomatic chickpea leaves using a cetyltrimethylammoniumbromide method with modifications (3). All leaf samples from eight symptomatic plants consistently tested positive using a polymerase chain reaction assay (PCR) with phytoplasma universal primers (P1/P7) that amplify a 1.8-kb phytoplasma rDNA product and followed by nested PCR with R16F2n/R16R2 primers yielding a product of 1.2 kb (2). No PCR products were evident when DNA extracted from healthy plants was used as template. Restriction fragment length polymorphism analysis of nested PCR products by separate digestion with Tru9I, HaeIII, HpaII, AluI, TaqI, HhaI, and RsaI restriction enzymes revealed that a phytoplasma belonging to group 16SrII peanut witches'-broom group (2) was associated with chickpea phyllody and little leaf disease in Oman. Restriction profiles of chickpea phytoplasma were identical with those of alfalfa witches'-broom phytoplasma, a known subgroup 16SrII-B strain (3). To our knowledge, this is the first report of phytoplasma infecting chickpea crops in Oman.

References: (1) A. J. Khan et al. Phytopathology, 92:1038, 2002. (2). I.-M. Lee et al. Int. J. Syst. Bacteriol. 48:1153, 1998 (3) M. A. Saghai-Maroof et al. Proc. Natl. Acad. Sci. USA. 81:8014, 1984.
Increased Occurrence of Target Spot of Soybean Caused by Corynespora cassiicola in the Southeastern United States
Authors: Koenning S. R. , Creswell T. C. , Dunphy E. J. , Sikora E. J. , Mueller J. D.
Published: May 2007

Target spot of soybean (Glycine max (L.) Merr.) caused by Corynespora cassiicola (Berk. & Curt.), although found in most soybean-growing countries, is considered to be a disease of limited importance (1) and has never been reported to cause soybean yield loss in the southeastern United States (2,3). Soybean plants submitted to the North Carolina Plant Disease and Insect Clinic (NCPDIC) in August 2004 from Beaufort, Robeson, Wilson, and Johnston counties, NC had symptoms consistent with target spot. Symptoms consisted of roughly circular, necrotic leaf lesions from minute to 11 mm in diameter, though typically approximately 4 to 5 mm in diameter, and with a yellow margin. Large lesions occasionally exhibited a zonate pattern often associated with this disease. Microscopic examination of the lesions revealed the presence of spores (conidia) typical of C. cassiicola (1). Conidia were mostly three to five septate with a central hilum at the base and ranged in size from 7 to 22 wide × 39 to 520 μm long. Three commercial soybean fields near Blackville, SC (Barnwell County) were severely affected by this disease and it caused premature defoliation. Nineteen of twenty-seven maturity group VII and VIII genotypes in the 2004 Clemson University soybean variety trial near Blackville, SC had visible symptoms of target spot. Heavy rainfall associated with hurricanes during September 2004 probably enhanced the incidence of this disease, and yield suppression due to target spot was estimated at 20 to 40% in some fields. In 2005, 20 of 161 soybean samples submitted to the NCPDIC or collected in surveys from 16 counties were positive for target spot on the basis of microscopic examination. Target spot also was diagnosed in six counties (Baldwin, DeKalb, Elmore, Fayette, Macon, and Pickens) in Alabama and in four additional counties (Bamberg, Hampton, Orange-burg, and Calhoun) in South Carolina in 2005. Records from the NCPDIC indicate that target spot had not been diagnosed on soybean in North Carolina since 1981. The large increase in incidence of target spot in the southeast may be related to changes in weather patterns, changes in pathogen virulence, and/or the introduction of more susceptible host genotypes.

References: (1) J. B. Sinclair. Target spot. Page 27 in: Compendium of Soybean Diseases. G. L. Hartman et al. eds. The American Phytopathological Society, St. Paul, MN, 1999. (2) J. A. Wrather et al. Plant Dis. 79:1076. 1995. (3) J. A. Wrather et al. On-line publication. doi:10.1094/PHP-2003-0325-01-RV. Plant Health Progress, 2003.
Endophyte-Mediated Suppression of Dollar Spot Disease in Fine Fescues
Authors: Clarke Bruce B. , White James F. , Hurley Richard H. , Torres Mónica S. , Sun S. , Huff David R.
Published: May 2007

In 1989, a close association was found between single-plant progenies of strong creeping red fescue infected with the endophyte Epichloë festucae and enhanced suppression of dollar spot, a widespread foliar disease of turfgrass caused by Sclerotinia homoeocarpa. From this limited observation, extensive field evaluations were conducted on a wide range of fine fescue germplasm obtained throughout the United States and Europe to determine the frequency and magnitude of this association. In five field trials established between 1985 and 1991, endophyte-infected Chewings, hard, blue, and strong creeping red fescue cultivars, selections, and crosses consistently exhibited endophyte-mediated suppression of dollar spot, when compared with closely related endophyte-free entries. Endophyte-infected Chewings and hard fescue cultivars and selections also had greater turf density and supported less foliar mycelium of S. homoeocarpa than endophyte-free entries.
Distribution of Papaya ringspot virus and Papaya mosaic virus in Papaya Plants (Carica papaya) in Mexico
Authors: Noa-Carrazana J. C. , González-de-León D. , Ruiz-Castro B. S. , Piñero D. , Silva-Rosales L.
Published: May 2007

We report the results of a survey for the presence of Papaya ringspot virus (PRSV) along the coasts of the Gulf of Mexico and the Pacific Ocean, in 15 federal states of Mexico that account for over 98% of the national papaya production. More than 80 locations were visited in 58 counties. Out of a total of 267 papaya leaf samples, 157 tested positive for PRSV. We tested for the presence of three other viruses because of the occurrence of severe, atypical symptoms in plantations. Only Papaya mosaic virus (PapMV) was detected. PRSV was present in every county. PapMV was less frequent, but its overall distribution was almost identical. PRSV and PapMV occurred in single or mixed infections of papaya and other host species that could function as virus reservoirs. We investigated the diversity of the coat protein (CP) sequences of 36 PRSV isolates. The amino acid sequence divergence among all isolates ranged from 0.4 to 9.9%, and was comparable to that found in other regions of the world. In contrast to most of these world regions, there is a clear correlation between CP sequence variation and the geographical origins of the virus isolates.
Effect of Lesion Age, Humidity, and Fungicide Application on Sporulation of Alternaria alternata, the Cause of Brown Spot of Tangerine
Authors: Reis R. F. , de Goes A. , Mondal S. N. , Shilts T. , Brentu F. C. , Timmer L. W.
Published: May 2007

Alternaria brown spot, caused by Alternaria alternata, causes yield losses and fruit blemishes on many tangerines and their hybrids in most citrus areas of the world where susceptible cultivars are grown. Although the conditions affecting infection and disease severity are known, little information is available on inoculum production on infected tissue. We found that sporulation on leaves began about 10 days after symptoms developed, was abundant from 20 to 40 days, and declined thereafter. Conidial production was far greater on leaf than on fruit or twig lesions. Spore production per unit area of leaf lesion was greater on the more susceptible hybrids, Minneola and Orlando tangelos, than on the less susceptible Murcott tangor. At 74% relative humidity, conidial production on leaf lesions was low, but it was abundant at 85, 92.5, 96, and 100%. Application of QoI or copper fungicides, but not ferbam, suppressed sporulation on leaf lesions for about 14 to 21 days after application. Additional applications did not appear to be more effective than a single spray in reducing inoculum production.
Effect of Leaf Rust on Grain Yield and Yield Traits of Durum Wheats with Race-Specific and Slow-Rusting Resistance to Leaf Rust
Authors: Herrera-Foessel S. A. , Singh R. P. , Huerta-Espino J. , Crossa J. , Yuen J. , Djurle A.
Published: May 2007

Leaf rust, caused by Puccinia triticina, is an important disease of durum wheat (Triticum turgidum) in many countries. We compared the effectiveness of different types of resistance in International Maize and Wheat Improvement Center-derived durum wheat germ plasm for protecting grain yield and yield traits. In all, 10 durum wheat lines with race-specific resistance, 18 with slow-rusting resistance, and 2 susceptible were included in two yield loss trials sown on different planting dates in Mexico with and without fungicide protection under high disease pressure. Eight genotypes with race-specific resistance were immune to leaf rust. Durum wheat lines with slow-rusting resistance displayed a range of severity responses indicating phenotypic diversity. Mean yield losses for susceptible, race-specific, and slow-rusting genotypes were 51, 5, and 26%, respectively, in the normal sowing date trial and 71, 11, and 44% when sown late. Yield losses were associated mainly with a reduction in biomass, harvest index, and kernels per square meter. Slow-rusting durum wheat lines with low disease levels and low yield losses, as well as genotypes with low yield losses despite moderate disease levels, were identified. Such genotypes can be used for breeding durum wheat genotypes with higher levels of resistance and negligible yield losses by using strategies that previously have been shown to be successful in bread wheat.
First Report of Tobacco mild green mosaic virus in Capsicum chinense in Venezuela
Authors: Córdoba C. , García-Rández A. , Montaño N. , Jordá C.
Published: May 2007

In July 2003, noticeable deformations of leaves were observed on a local variety of Capsicum chinense, also called ‘Aji dulce’, from a pepper plantation located in Venezuela, (Monagas State). ‘Aji dulce’ is a basic ingredient of the Venezuelan gastronomy with an estimated cultivated area of 2,000 ha. The seeds of this local pepper are obtained by the growers who reproduce and multiply their own seeds every year. Seeds of affected plants were sent to our laboratory, and a group of approximately 100 seeds was sown in a controlled greenhouse that belongs to the Polytechnic University of Valencia, Spain. Three months later, obvious curling and bubbling developed on the leaves of the plants. Extracts of symptomatic plants tested negative for Tomato mosaic virus (ToMV), Tobacco mosaic virus (TMV), Pepper mild mottle virus (PMMV), and Tobacco etch virus (TEV) by double-antibody sandwich enzyme-linked immunosorbent assays (DAS-ELISA) with policlonal antibodies specific to each virus (Loewe Biochemica GMBH, Sauerlach, Germany; Phyto-Diagnostics, INRA, France). Total RNA was isolated from 0.5 g of original seed sent from Venezuela and from 25 samples of leaves of plants grown in the greenhouse with an RNeasy Plant Mini Kit (Qiagen Sciences, Germantown, Maryland). The RNA isolated was used in reverse transcription-polymerase chain reaction (RT-PCR) with specific primers for Tobacco mild green mosaic virus (TMGMV) (1) predicted to amplify a 530 bp of the coat protein region. From all samples, a RT-PCR product of the expected size was obtained and then sequenced. BLAST analysis of one sequence (GenBank Accession No. DQ460731) showed high levels of identity with TMGMV isolates, with more than 99% nucleotide identity with the DSMZ PV-112 isolate (GenBank Accession No. AJ429096). The symptomatology observed on pepper plants, the TMGMV RT-PCR assay, and the consensus of sequenced regions with TMGMV lead us to conclude that TMGMV was the causal agent of the diseased C. chinense plants. Although TMGMV has a wide plant host range occurring worldwide (1), to our knowledge, this is not only the first time TMGMV has been detected in Venezuela, but also the first report of TMGMV in C. chinense in Venezuela and the first reliable probe of the TMGMV seed transmission.

Reference: (1) J. Cohen et al. Ann. Appl. Biol. 138:153, 2001.
First Report of Sweet potato leaf curl virus in China
Authors: Luan Y. S. , Zhang J. , An L. J.
Published: May 2007

During the 2004 growing season in the Liaoning Province in China, where there was large population of whiteflies, several sweet potato (Ipomoea batatas) breeding lines showed leaf curl symptoms. A survey was conducted to determine the incidence of Sweet potato leaf curl virus (SPLCV) in China. Sixteen plants were collected and stem scions from those plants were graft inoculated to Ipomoea nil. Three weeks later, the indicator developed symptoms of leaf curling, interveinal chlorosis, and stunting. Total nucleic acid was extracted from young leaves of sweet potato and then evaluated using polymerase chain reaction (PCR). Primers, developed by Briddon and Markham (1) and used as universal primers for amplification of the geminivirus DNA fragment, were BM-V (5′-KSG GGT CGA CGT CAT CAA TGA CGT TRT AC-3′) and BM-C (5′-AAR GAA TTC ATK GGG GCC CAR ARR GAC TGG C-3′). Amplified fragments with BM primers theoretically should have sizes almost equal to the full length of the DNA A component of the bipartite genome (2). Expected DNA fragments of 2.8 kb that contained the AV1, AV2, AC1, AC2, AC3, and AC4 open reading frames were obtained from symptomatic, but not from symptomless (uninfected) plants. The 2.8-kb fragments obtained by amplification were purified and cloned into the PMD18-T vector. Recombinant plasmids were then transformed into competent cells of Escherichia coli strain DH5(. The fragment was sequenced (GenBank Accession No. DQ512731), and nucleotide sequence of corresponding regions were compared with a published sequence of SPLCV available in GenBank (Accession No. AF104036). The AC4 and AC2 genes showed the highest (92%) and the lowest (83%) identity, respectively. This virus has been reported in the United States, Taiwan, Japan, and Peru. To our knowledge, this is the first report of the natural occurrence of SPLCV in China.

References: (1) R. W. Briddon and P. G. Markham. Mol. Biotechnol. 1:202, 1994. (2) M. Onuki and K. Hanada. Ann. Phytopathol. Soc. Jpn. 64:116, 1998.
First Report of Leaf Spot Caused by Phoma exigua on Hydrangea macrophylla in Italy
Authors: Garibaldi A. , Gilardi G. , Minerdi D. , Gullino M. L.
Published: May 2007

Hydrangea macrophylla is grown in Italy as a potted plant and also for landscaping. During the fall of 2005 in a nursery located in Lazio (central Italy), a severe foliar disease was observed on 12-month-old potted plants of cv. Hanabi. Small necrotic spots surrounded by chlorotic haloes were observed on the upper side of infected leaves. At temperatures near 20°C and relative humidity ranging between 80 to 90%, spots enlarged to form round areas 2 to 7 cm in diameter that were well defined by a brown margin. Severely infected leaves became chlorotic and abscised. Heavily affected plants were defoliated. Infected plants rarely died, but the presence of lesions on mature plants decreased aesthetic quality and subsequent market value. The disease occurred on 30% of the plants in one nursery. Stems and flowers were not affected by the disease. From infected leaves, a fungus was consistently isolated on potato dextrose agar with 25 mg/liter of streptomycin added. The fungus was grown on leaf extract agar, 30 g of leaves per liter, and maintained at 22°C (12 h of light and 12 h of dark). After 30 days, black pycnidia 275 to 255 μm in diameter developed, releasing conidia that were hyaline, elliptical, nonseptate, and measuring 4.6 to 7.6 (average 6.0) × 1.4 to 4.2 (average 2.6) μm. On oatmeal agar, the addition of a drop of concentrated NaOH caused a positive reaction, turning the medium red (2). On the basis of its morphological characteristics, the fungus was identified as a Phoma sp. The ITS (internal transcribed spacer) region of rDNA was amplified using the primers ITS4/ITS6 (3) and sequenced. BLASTn analysis (1) of the 560 bp obtained showing an E-value of 0.0 with Phoma exigua. The nucleotide sequence has been assigned GenBank Accession No. DQ384612. Pathogenicity tests were performed by spraying leaves of healthy 6-month-old potted H. macrophylla (cvs. Hanabi and Zaffiro) plants with a spore and mycelial suspension (105 CFU/ml). Plants without inoculation served as controls. Five plants were used for each treatment. Plants were covered with plastic bags for 5 days after inoculation and kept in a growth chamber at 20°C with relative humidity at 80 to 90%. The first lesions developed on leaves of cv. Hanabi 12 days after inoculation, while control plants remained healthy. Lesions did not develop on inoculated cv. Zaffiro plants. The fungus was consistently reisolated from the lesions of cv. Hanabi. The pathogenicity test was carried out twice. The presence of P. exigua on H. macrophylla has been reported in the United States (4). In Italy, the disease can be found in a limited area.

References: (1) S. F. Altschud et al. Nucleic Acids Res. 25:3389, 1997. (2) G. H. Boerema and L. H. Howeler. Persoonia 5:15, 1967. (3) D. E. L. Cooke and J. M. Duncan. Mycol. Res. 101:667, 1997. (4) M. L. Daughtrey et al. Page 26 in: Compendium of Flowering Potted Plant Diseases. The American Phytopathological Society. St. Paul, MN, 1995.
Inheritance of White Mold Resistance in Phaseolus vulgaris × P. coccineus Crosses
Authors: Schwartz Howard F. , Otto Kristen , Terán Henry , Lema Margarita , Singh Shree P.
Published: May 2007

The fungus Sclerotinia sclerotiorum, cause of white mold, is known to attack >400 plant species. It is a widespread problem in dry bean (Phaseolus vulgaris) in the United States, causing >30% average yield losses. Low to moderate levels of resistance are found in dry bean. However, some accessions of P. coccineus (commonly known as scarlet runner bean) possess a relatively higher level of resistance. Our objective was to verify the reaction of 13 known white mold-resistant P. coccineus germ plasms and determine inheritance of resistance in accessions PI 433246 and PI 439534. Pinto Othello was crossed with PI 433246, and the resulting interspecific F1 was back-crossed onto Othello and allowed to produce F2 seed. Similarly, pinto UI 320 was crossed with PI 439534. The F1 was backcrossed onto UI 320 and allowed to produce F2 seed. The two parents, F1, F2, and backcross to dry bean of each set were evaluated in the greenhouse using the straw test at Fort Collins, CO in 2004. All 13 P. coccineus accessions and the two F2 also were evaluated using the modified petiole test at Kimberly, ID in 2005. All 13 P. coccineus accessions were variable in a 2002 straw test when rated for white mold reaction on a 1-to-9 scale, because the mean disease score ranged from 1.9 for PI 433246 to 4.4 for PI 189023 and 8.8 for the susceptible check Bill Z. For the petiole test, when rated on a 1-to-9 scale, the accessions exhibited an intermediate white mold score of 4 or 5 in 2005. In 2004, the susceptible check Othello exhibited a mean score of 7.9 compared with 3.4, 3.2, and 2.1 for PI 433246, UI 320, and PI 439534, respectively. The white mold reaction of PI 433246 and PI 439534 was dominant in their respective F1. The F2 segregation further indicated that white mold resistance in PI 433246 and PI 439534 was controlled by a single dominant gene. These two and other white mold-resistant P. coccineus accessions and selected breeding lines from the interspecific crosses should be useful for future improvement of white mold resistance of pinto and other market classes of dry and green or snap bean.
Identification of Sources of Multiple Disease Resistance in Mini-core Collection of Chickpea
Authors: Pande S. , Kishore G. Krishna , Upadhyaya H. D. , Rao J. Narayana
Published: May 2007

Host plant resistance is the major component in the management of fungal diseases in chickpea (Cicer arietinum). We screened a chickpea mini-core collection composed of 211 germ plasm accessions representing the diversity of the global chickpea germ plasm collection of 16,991, maintained at the International Crops Research Institute for the Semi-Arid Tropics to identify sources of multiple disease resistance. The accessions were screened for resistance against As-cochyta blight (Ascochyta rabiei), Botrytis gray mold (Botrytis cinerea), Fusarium wilt (Fusarium oxysporum f. sp. ciceris), and dry root rot (Rhizoctonia bataticola) under a controlled environment. High levels of resistance were observed to Fusarium wilt (FW), where 21 accessions were asymptomatic and 25 resistant. In all, 3, 55, and 6 accessions were moderately resistant to Ascochyta blight (AB), Botrytis gray mold (BGM), and dry root rot (DRR) respectively. ICC 11284 was the only accession moderately resistant to both AB and BGM. Combined resistance also was identified for DRR and FW in 4 accessions, and for BGM and FW in 11 accessions. Through this study, chickpea germ plasm accessions were identified that possess high levels of resistance to more than one fungal disease and would be useful in chickpea multiple disease resistance breeding programs.
Characterization of a Novel Adhesin-like Gene and Design of a Real-Time PCR for Rapid, Sensitive, and Specific Detection of Spiroplasma kunkelii
Authors: Wei Wei , Opgenorth Dan C. , Davis Robert E. , Chang Chung-Jan , Summers Charles G. , Zhao Yan
Published: May 2007

Spiroplasma kunkelii, a cell wall-less bacterium, is the causal agent of corn stunt disease. The pathogen is restricted to phloem sieve cells of infected plants and is transmitted by phloem-feeding leafhoppers. Since symptoms of corn stunt disease may not appear until close to flowering time, early detection of the pathogen in disease-transmitting leafhoppers and in symptomless foliar tissues of host plants is critical to disease forecasting and outbreak management. In this study, a field-deployable real-time polymerase chain reaction (PCR) assay was developed for sensitive and specific detection of S. kunkelii. Nucleotide sequence from a previously unreported adhesin-like gene was used to design primers and a fluorogenic probe. The assay was able to detect the presence of S. kunkelii DNA as low as 5 fg, a sensitivity 100 times more than that of conventional PCR. The assay was found to be highly specific to S. kunkelii, as it did not cross-react with one of the most closely related plant pathogenic spiroplasma species, S. citri. The assay was successfully applied to rapid field detection of S. kunkelii in its plant host and insect vectors.
Introduction of Asian Soybean Rust Urediniospores into the Midwestern United States—A Case Study
Authors: Krupa Sagar , Bowersox Van , Claybrooke Roger , Barnes Charles W. , Szabo Les , Harlin Karen , Kurle James
Published: May 2007

In 2005, weekly rain samples collected at 124 National Atmospheric Deposition Program/National Trends Network (NADP/NTN) sites in the eastern and central United States were screened for Asian soybean rust (ASR; Phakopsora pachyrhizi) urediniospores. Application of a quantitative polymerase chain reaction method detected P. pachyrhizi DNA in the filter residue of rain samples collected during the week of 19 to 26 July 2005 in Minnesota, Missouri, and South Dakota. To determine the geographic origin of ASR urediniospores in those weekly composite samples, back air trajectories of the lifted condensation and mixed boundary layers were calculated for each rain event within the week, by sampling site. The calculations, based on the hybrid single-particle lagrangian integrated trajectory model, pointed to source areas in eastern and southern Texas. In a separate case, DNA of P. pachyrhizi was detected in a 28 June to 5 July 2005 rain sample from an eastern Texas site. Back trajectories pointed to southern Texas and the Yucatan Peninsula in Mexico as potential source areas of ASR urediniospores. Vertical motions of those back trajectories indicated a ventilation of the boundary layer in the upwind areas, suggesting the possible injection of urediniospores into the free troposphere where they can be transported for long distances before wet deposition.
First Report of Ramularia carthami, Causal Agent of Ramularia Leaf Spot of Safflower, in California
Authors: Hostert N. D. , Blomquist C. L. , Thomas S. L. , Fogle D. G. , Davis R. M.
Published: May 2007

Ramularia leaf spot was identified in several fields of safflower (Carthamus tinctorius) near Gridley, CA in June 2005. Numerous circular to irregularly shaped brown lesions, 3 to 10 mm in diameter, on both sides of leaves and flower bracts resulted in stunted plants and reduced seed production. In two of the fields, nearly all plants were affected, yields were severely reduced, and the crops were abandoned. Ramularia carthami Zaprom. was identified on the basis of morphology of reproductive structures on colonized leaves (1). Hyaline, thin-walled, aseptate conidiophores (2.6 to 4.3 × 28.8 to 72.0 μm) were produced in fan-like fascicles borne on hemispherical stromata (21.6 to 31.2 × 24.0 to 36.0 μm). Hyaline, smooth, cylindrical to fusiform conidia (7.2 to 12.0 × 19.2 to 40.8 μm), 1 to 3 septate or rarely aseptate were produced singly or in short chains. The fungus was isolated from symptomatic leaves and bracts surface disinfected for 1 min in 0.5% sodium hypochlorite and incubated at 25°C on acidified potato dextrose agar (APDA). Colonies of the fungus were white with irregular margins and were slow growing. After 3 weeks, colonies were approximately 3 cm in diameter. Conidia were not produced in culture. To conduct pathogenicity tests, three 3-week-old safflower plants grown in the greenhouse were sprayed with an aqueous suspension of mycelial fragments of the fungus. Inoculum was produced by macerating a 3-cm-diameter APDA culture of the fungus in 30 ml of water. Noninoculated control plants were sprayed with water. All plants were covered with plastic bags for 48 h on a greenhouse bench. Greenhouse temperatures ranged from a minimum of 20°C to a maximum of 27°C. After 7 days, all inoculated plants developed symptoms, and the fungus was reisolated from lesions. Conidia from lesions were suspended in water and diluted to a concentration of 1 × 105 conidia/ml and used as inoculum for additional pathogenicity tests. Three plants were sprayed with the conidial suspension or water as above. Lesions developed on the inoculated plants in 7 days, and the fungus was reisolated. No symptoms developed on plants sprayed with water. Both pathogenicity tests were repeated once. Sequence of the internal transcribed spacer region of rDNA of the fungus was deposited in GenBank (Accession No. DQ466083). To our knowledge, this is the first confirmed report of Ramularia leaf spot of safflower caused by R. carthami in California.

Reference: (1) Morbi Plant. Script. Sect. Phytopath. Hort. Bot. Prince. USSR 15:142, 1926.
Population Biology of Pseudoperonospora humuli in Oregon and Washington
Authors: Chee Hee Youn , Nelson Mark E. , Grove Gary G. , Eastwell Kenneth C. , Kenny Stephen T. , Klein Robert E.
Published: May 2007

Pseudoperonospora humuli populations from Oregon and Washington were analyzed for genetic variation using random amplified polymorphic DNA (RAPD) and DNA amplification fingerprinting (DAF) markers. The genetic structure of the Oregon and Washington populations differed considerably. There was little genetic diversity in Washington, with only five RAPD and six DAF groups detected among 40 isolates tested. One genotype was predominant in Washing-ton. In contrast, 18 RAPD and 34 DAF groups were found among the 40 isolates tested from Oregon. No unique band profile associated with host cultivar was observed. It is suggested that the distinct difference in population structure between the two geographic regions might be due to climatic differences resulting in a higher frequency of sexual reproduction of P. humuli in Oregon than in Washington.
Rates of Epiphytic Growth of Erwinia amylovora on Flowers Common in the Landscape
Authors: Johnson K. B. , Sawyer T. L. , Temple T. N.
Published: May 2007

We evaluated epiphytic growth of the fire blight bacterium, Erwinia amylovora, on flowers of plant species common to landscapes where pears and apples are grown. The plants were from genera regarded as important nectar and pollen sources for pollinating insects: Acer, Amelanchier, Brassica, Cytisus, Populus, Prunus, Rubus, Salix, Taraxacum, Trifolium, and Symphoricarpos. Floral bouquets were inoculated with E. amylovora and incubated in growth chambers at 15°C for 96 h. Regardless of their susceptibility to fire blight, all species from the rose family except Prunus domestica (European plum) supported epiphytic populations of E. amylovora that exceeded 1 × 106 CFU/flower with relative growth rates for the populations that averaged 7% per hour. Nonrosaceous plants were generally poor supporters of epiphytic growth of the fire blight pathogen with relative growth rates averaging <4% per hour. In two seasons of field inoculations, the rosaceous non-disease-host plants, Prunus avium (sweet cherry) and Rubus armeniacus (Himalayan blackberry), yielded mean population sizes of E. amylovora that exceeded 1 × 106 CFU/flower; in contrast, at 8 days after inoculation, mean population sizes of the pathogen were in the range of 5 × 103 to 5 × 104 CFU/flower on Cytisus scoparius (Scotch broom) and <1 × 102 CFU on Acer macrophylum (big leaf maple). Because vectors of E. amylovora, principally bees, visit many kinds of flowers in landscape areas between pear and apple orchards, flowers of rosaceous, non-disease-host species could serve as potential sites of inoculum increase during their periods of bloom.
Comparison of Models for Forecasting of Stewart's Disease of Corn in Iowa
Authors: Esker P. D. , Harri J. , Dixon P. M. , Nutter F. W.
Published: May 2007

Three forecasting models for Stewart's disease (Pantoea stewartii subsp. stewartii) of corn (Zea mays) were examined for their ability to accurately predict the prevalence of Stewart's disease in Iowa at the county level. The Stevens Model, which is used as a predictor of the early wilt phase of Stewart's disease, the Stevens-Boewe Model, which predicts the late leaf blight phase of Stewart's disease, and the Iowa State Model that is used to predict the prevalence of Stewart's disease, all use mean air temperatures for December, January, and February for a preplant prediction of Stewart's disease risk in a subsequent season. Models were fitted using weighted binary logistic regression with Stewart's disease prevalence data and air temperature data for 1972 to 2003. For each model, the years 1972 to 1999 (n = 786 county-years) were used for model development to obtain parameter coefficients. All three models indicated an increased likelihood for Stewart's disease occurring in growing seasons preceded by warmer winters. Using internal bootstrap validation, the Stevens Model had a maximum error between predicted and calibrated probabilities of 10%, whereas the Stevens-Boewe and Iowa State models had maximum errors of 1% or less. External validation for each model, using air temperature and seed corn inspection data between 2000 and 2003 (n = 154 county-years), indicated that overall accuracy to predict Stewart's disease at the county level was between 62 and 66%. However, both the Stevens and Stevens-Boewe models were overly optimistic in predicting that Stewart's disease would not occur within specific counties, as the sensitivity for these two models was quite low (18 and 43%, respectively). The Iowa State Model was substantially more sensitive (67%). The results of this study suggest that the Iowa State Model has increased predictive ability beyond statewide predictions for estimating the risk of Stewart's disease at the county level in Iowa.
First Report of Aglaonema Bacterial Blight Caused by Erwinia chrysanthemi in Taiwan
Authors: Chao Y. C. , Feng C. T. , Ho W. C.
Published: May 2007

Aglaonema (Aglaonema spp.) is a popular ornamental potted plant in Taiwan. In 2003, leaves showing soft rot symptoms were found on a number of Sithiporn aglaonema (A. marantifoloum var. tricolor × A. rotundum) plants in a nursery in southern Taiwan. The disease usually started from leaf tips or wounded sites and the affected areas appeared water soaked. The diseased tissue subsequently turned dark brown and became fragile. More than 50% of Sithiporn aglaonema plants were destroyed in the affected nursery. Bacteria isolated from the symptomatic leaves grew at 39°C, degraded pectate, caused soft rot on slices of potato tuber and petioles of Chinese cabbage, produced phosphatase and lecithinase, and utilized malonate, but did not grow in 5% NaCl or produce acid from trehalose. These characteristics were similar to those of Erwinia chrysanthemi Burkholder et al. (1,2) and the reference strain OS2 from Phalaenopsis sp. provided by K. C. Tzeng of National Chung Hsing University, Taichung, Taiwan. Polymerase chain reaction (PCR) analysis using the primer pair 5A (5′ GCGGTTGTTCACCAGGTGTTTT 3′) and 5B (5′ ATGCACGCTACCTGGAAGTAT 3′) specific for E. chrysanthemi (4) confirmed the identity of all seven isolates tested as E. chrysanthemi. The primer pair 5A/5B was designed from the sequences of pT8-1, idg (a gene for blue-pigment synthesis), and pecS (a gene for regulation of pectinase, cellulose, and pigment production). PCR products amplified from E. chrysanthemi DNA with the 5A/5B primer were 500 bp (4). Pathogenicity of isolates was confirmed by rubbing the leaf surface of Sithiporn aglaonema plants with Carborundum and spraying the wounded surface with a bacterial suspension at 1 × 108 CFU/ml in the greenhouse. Plant leaves sprayed with distilled water were used as the control. Three leaves were inoculated for each isolate, and the experiment was conducted twice. Symptoms appeared within 24 h after inoculation. All seven isolates tested were pathogenic, causing an average of 86 to 95% of inoculated leaves to show water-soaked symptoms similar to these observed in nature. Symptoms did not occur on control leaves. E. chrysanthemi was reisolated from diseased tissues of inoculated leaves. To our knowledge, this is the first report of bacterial blight caused by E. chrysanthemi on aglaonema in Taiwan and the first report of the disease on the Sithiporn cultivar of aglaonema. This disease on aglaonema was previously reported in the United States (3).

References: (1) R. S. Dickey and A. Kelman. Page 44 in: Laboratory Guide for Identification of Plant Pathogenic Bacteria. N. W. Schaad, ed. The American Phytopathological Society, St. Paul, MN, 1988. (2) M. Goto and K. Matsumoto. Int. J. Syst. Bacteriol. 37:130, 1987. (3) L. A. McFadden. Plant Dis. Rep. 53:253. 1969. (4) M. G. Zhu. Ph.D. diss, National Chung Hsing University, Taichung, Taiwan, 1995.
A Postharvest Fruit Rot in Apple Caused by Phacidiopycnis washingtonensis
Authors: Kim Y. K. , Xiao C. L.
Published: May 2007

During a survey of postharvest diseases in Red Delicious apples (Malus domestica) conducted in 2003, a previously undescribed postharvest fruit rot was discovered in Washington State. The causal agent has been described as a new species, Phacidiopycnis washingtonensis. In this study, we described the symptomatology of this disease, determined its occurrence and prevalence in Washington State, tested pathogenicity, and determined infection courts on fruit of three apple varieties. Decayed fruit were sampled from 26, 72, and 81 grower lots during March to August in 2003, 2004, and 2005, respectively, during packing operations from commercial packinghouses. Symptoms of decayed fruit were recorded and isolations were made from decayed fruit to correlate causal agents with the disease symptoms observed. Fruit of Red Delicious, Golden Delicious, and Fuji apples were inoculated in the orchards with conidial suspensions of the fungus at 1 and 2 weeks before harvest. All fruit were harvested and stored at 0°C, and decay development on the fruit was monitored monthly for up to 9 months. The symptoms were primarily stem-end rot and calyx-end rot. Infection also occurred at lenticels on fruit skin, particularly on Golden Delicious. The decayed area was spongy to firm and appeared light brown to brown. On Red Delicious, brown to black specks at lenticels often appeared at the decayed area as the disease advanced. This disease occurred in 23, 26, and 17% of the total grower lots, accounting for approximately 1, 4, and 3% of the total decay in 2003, 2004, and 2005, respectively. In 2004 and 2005, severe losses of fruit were observed in three grower lots of Red Delicious, and their losses were as high as 24%. After 9 months in storage, 48, 48, and 24% of Red Delicious, Golden Delicious, and Fuji that were inoculated in the orchards, respectively, developed symptoms of this disease, and the fungus was reisolated from decayed fruit. Stem-end rot was common on Red Delicious and Golden Delicious, whereas calyx-end rot was common on Fuji. We propose “speck rot” as the name of this disease.
First Report of Beet pseudo-yellows virus and Strawberry pallidosis associated virus in Strawberry in Peru
Authors: Wintermantel W. M. , Fuentes S. , Chuquillanqui C. , Salazar L. F.
Published: May 2007

During a 2006 survey for the presence of criniviruses in Peru, large numbers of greenhouse whitefly (Trialeurodes vaporariorum) were observed infesting strawberry (Fragaria × ananassa) fields near Huaral on the central coast of Peru. Plants exhibited a wide range of symptoms including stunting and reddening of leaves. These symptoms are characteristic of those induced by the presence of the criniviruses Beet pseudo-yellows virus (BPYV) and/or Strawberry pallidosis associated virus (SPaV) together with any of a number of different strawberry-infecting viruses (1,3). The virus complex causes older leaves to develop a red color, vein and petiole reddening, roots become stunted, and plants fail to develop. Leaf samples with varying symptoms were collected from 22 plants from 2 fields, each planted with a different cultivar. Total nucleic acid was extracted, spotted onto positively charged nylon membranes, and tested by hybridization with probes specific to the minor coat protein (CPm) gene of BPYV (2) and coat protein (CP) gene of SPaV (4). Results identified the presence of BPYV, SPaV, or both viruses in mixed infections in symptomatic strawberry, while control plants were infected with each virus individually. No signal was detected in virus-free strawberry. Secondary confirmation was obtained using probes specific to the RNA-dependent RNA polymerase (RdRp) genes of SPaV and BPYV. The SPaV probe corresponded to nucleotides 6116–6599 of SPaV RNA1 (GenBank Accession No. NC_005895), whereas the BPYV probe corresponded to nucleotides 6076–6447 of BPYV RNA1 (GenBank Accession No. NC_005209). All probes were generated by reverse-transcription polymerase chain reaction (RT-PCR) amplification using sequence-specific primers, cloning of RT-PCR products into pGEM-T Easy (Promega, Madison, WI), confirmation by sequencing, and expression as digoxygenin-labeled transcript probes (Roche, Indianapolis, IN). Field 1, containing cv. Fern Sancho, had the largest number of symptomatic and infected plants (5 of 12 BPYV, 6 of 12 SPaV, and 4 of 12 with both). Only 1 of 10 plants from field 2 containing cv. Tajo Holandesa was infected, but with both SPaV and BPYV. BPYV and SPaV are transmitted by the greenhouse whitefly (T. vaporariorum), although BPYV is transmitted much more efficiently and has a broader host range than SPaV (4). Movement of these viruses in Peru is likely a result of both propagation by runners and vector transmission. To our knowledge, this is the first report of either virus in Peru.

References: R. R Martin and I. E. Tzanetakis. Plant Dis. 90:384, 2006. (2) I. E. Tzanetakis and R. R. Martin. Plant Dis. 88:223, 2004. (3) I. E. Tzanetakis et al. Plant Dis. 87:1398, 2003. (4) I. E. Tzanetakis et al. Plant Dis. 90:1343, 2006.
First Report of Psittacanthus macrantherus on Pinus devoniana and Quercus castanea in Mexico
Authors: Howell B. , Kenaley S. , Mathiasen R.
Published: May 2007

The mistletoe Psittacanthus macrantherus Eichl. (Loranthaceae) is an important parasite of pines (Pinus spp., Pinaceae) in Mexico (1). It has been reported to parasitize Pinus engelmannii Carr., P. herrerai Mart., P. lawsonii Roezl ex Gord. & Glend., P. lumholtzii Robins & Fern., P. oocarpa Schiede, and P. pseudostrobus Lindl. (1). During July 2005, we found this mistletoe parasitizing P. devoniana Lindl. and Quercus castanea Nee near Route 40 in Sinaloa, Mexico approximately 12 km west of El Palmito (23°30′N, 105°07′W, elevation 1,900 m). The mistletoe was common in P. devoniana, and some trees were severely infected (>10 plants per tree). However, no mortality associated with mistletoe infection in P. devoniana was observed. Only one infected tree of Q. castanea was observed in this area and it was not severely infected. We also observed this mistletoe on P. douglasiana Mart. along Route 40 west and east of El Palmito, but no specimens were collected because plants were very high in the crowns of the infected trees. To our knowledge, this is the first report of this mistletoe parasitizing P. devoniana, P. douglasiana, and Q. castanea (1). Specimens of Psittacanthus macrantherus from P. devoniana and Q. castenea have been deposited at the Deaver Herbarium (ASC), Northern Arizona University, Flagstaff (Accession Nos. 79534 and 79535).

References: (1) B. Geils et al. Mistletoes of North American conifers. USDA For. Serv. Gen. Tech. Rep. RMRS-GTR-98, 2002.
Resistance of Four Inbred Maize Lines to Inoculation with 20 Isolates of Maize streak virus from Zimbabwe
Authors: Mawere S. , Vincent V. , De Meyer J. , Pixley K. V.
Published: May 2007

Maize streak is the most widespread and important disease of maize in sub-Saharan Africa. Maize streak virus (MSV)-resistant maize germ plasm is available in several countries, but little is known about the stability of its resistance to MSV strains that may differ from one region to another. We used four maize inbred lines (CML312, CML206, CML216, and MSR) known to differ widely for their resistance to MSV in Harare, and evaluated their resistance to 20 MSV isolates collected from the wild during 2 years at locations across Zimbabwe. Maize streak development and symptom severity were evaluated in replicated greenhouse experiments using artificial inoculation via viruliferous leafhoppers. All 20 MSV isolates induced maize streak symptoms on moderately and highly susceptible genotypes by about 1 week after inoculation (WAI). Differences among isolates for severity of early maize streak symptoms were ephemeral, and resistance was accurately differentiated by all isolates by 3 to 4 WAI. Differences in final maize streak symptom scores induced by the isolates were statistically significant, but differed only by a maximum of 7% in 1999 and 19% in 2000. Although genotype, isolate, and genotype by isolate effects for maize streak symptom scores were significant (P < 0.01), relative MSV resistance of the genotypes was consistently ranked by all 20 MSV isolates.
Identification and Distribution ofBotryosphaeriaspp. Associated with Grapevine Cankers in California
Authors: Úrbez-Torres J. R. , Leavitt G. M. , Voegel T. M. , Gubler W. D.
Published: May 2007

Botryosphaeria spp. recently have been identified as important grapevine pathogens worldwide. To date, Botryosphaeria rhodina has been the only species associated with cankers on Vitis vinifera in California. A field survey of 166 vineyards in 21 counties was conducted in order to determine the occurrence of other Botryosphaeria spp. in California. In all, 1,735 samples of cankered trunks, cordons, and spurs were collected. Botryosphaeria spp. were the most common fungi isolated from grapevine cankers in California. Morphological identification along with phylogenetic analysis of the internal transcribed spacer region (ITS1-5.8S-ITS2) of the nuclear ribosomal DNA (rDNA) and a partial sequence of the β-tubulin gene showed that at least seven Botryosphaeria spp. occur on grapevines in California: B. australis, B. dothidea, B. lutea, B. obtusa, B. parva, B. rhodina, and B. stevensii. Botryosphaeria spp. were found in grapevine cankers in all grape-growing regions surveyed in California, whereas incidence and distribution varied with location. Grapevine cankers in California have been associated mainly with Eutypa dieback. However, the frequent recovery of Botryosphaeria spp. from cankers in this study indicates that the role of these fungi in grapevine health needs to be more carefully considered.
Influence of Host Resistance and Insecticide Seed Treatments on Curly Top in Sugar Beets
Authors: Strausbaugh Carl A. , Gillen Anne M. , Gallian John J. , Camp Stacey , Stander J. R.
Published: May 2007

Curly top on sugar beets (Beta vulgaris) caused by Beet severe curly top virus or closely related species is a considerable problem in arid growing regions of the western United States. Two insecticide seed treatments, Poncho Beta (60 g a.i. clothianidin + 8 g a.i. beta-cyfluthrin/100,000 seed) and Gaucho (45 g a.i. imidacloprid/100,000 seed), and four sugar beet hybrids varying in curly top resistance were evaluated for their influence on the control of curly top in comparison with untreated checks. Plots were established at two locations in southern Idaho in 2005 and evaluated for curly top. Moderate to severe curly top due to natural inoculum and leafhopper infestations occurred at both locations. Untreated, the four hybrids performed as expected with the fewest curly top symptoms on PM21 and the most on Monohikari. Both insecticide treatments lowered curly top ratings compared with the untreated check, but Poncho Beta reduced symptoms more than Gaucho as the season progressed. Poncho Beta led to increased yield and estimated recoverable sugar across all hybrids at harvest, particularly on the more susceptible hybrids. When considering the yield parameters for only the most resistant hybrids individually, Poncho Beta did not always outperform Gaucho. Poncho Beta provided a level of control that would justify its application as a supplement to host resistance under Idaho conditions.
Deletion of a Chromosome Arm Altered Wheat Resistance to Fusarium Head Blight and Deoxynivalenol Accumulation in Chinese Spring
Authors: Ma Hong-Xiang , Bai Gui-Hua , Gill Bikram S. , Hart L. Patrick
Published: May 2007

Fusarium head blight (FHB), caused by Fusarium graminearum Schwabe, is an important disease of wheat worldwide. Production of deoxynivalenol (DON) in infected wheat grain by F. graminearum is a major safety concern when considering use of the grain as feed for livestock or for human consumption. Determining chromosome locations of FHB-related genes may facilitate enhancement of wheat resistance to FHB and DON accumulation. In this study, a set of 30 ditelosomic lines derived from Chinese Spring, a moderately FHB-resistant landrace from China, were evaluated for proportion of scabbed spikelets per inoculated spike in the greenhouse and for DON contamination in harvested grain over 2 years. Significant variation in the proportion of scabbed spikelets was observed among ditelosomic lines, ranging from 13 to 95%. Seven ditelosomic lines exhibited a greater proportion of scabbed spikelets and three of these also had greater DON content than Chinese Spring (P = 0.01), suggesting that those missing chromosome arms may carry genes that contribute to resistance to FHB. Six ditelosomic lines had a reduction in proportion of scabbed spikelets, suggesting that susceptibility factors or resistance suppressors may be on these missing chromosomal arms. Selection for low proportion of scabbed spikelets in general will select for low DON content.