bluuebunny/crossref_metadata_2025 huggingface dataset:
First Report of Root Rot and Stem Blight Caused by Phytophthora palmivora in Eustoma grandiflorum
Authors: Toppe B. , Aanonsen E. , Klemsdal S.
Published: May 2007

Eustoma grandiflorum (Raf.) Shinn., commonly referred to as Lisianthus or Texas bluebell, is grown on a limited but increasing scale in Norwegian greenhouses. In autumn 1999, E. grandiflorum plants with brown rotten roots and wilting foliage were collected from a cut-flower production facility in southeastern Norway. Symptoms were difficult to distinguish from those caused by Pythium spp. or early attack of Fusarium spp. For diagnosis, root and stem segments surface sterilized by dipping in alcohol and hypochlorite were plated on potato dextrose agar. Phytophthora sp. was isolated consistently from diseased roots and stems. Suspected Phytophthora sp. isolates were transferred to selective agar medium containing hymexazol and identified by morphological characteristics and DNA sequence homology (1). The fungus was characterized by stellate mycelium, lack of oogonia in single culture, sympodial sporangiophores, and production of numerous papillate, ellipsoid sporangia that were caduceus with small pedicels in water. Optimum temperature for mycelium growth was 25 to 30°C, with limited growth at 10 and 35°C. The DNA sequence of the polymerase chain reaction amplified internal transcribed spacer (ITS1 and ITS2) regions of rDNA, confirmed the identification as P. palmivora. Pathogenicity studies were conducted by inoculating nine, 12-week-old E. grandiflorum plants grown in 10-cm pots with peat substrate at 24°C with artificial light (120 W/m2) for 10 h per day, with a zoospore suspension or an agar piece toward the plant stem. The pathogenicity study was repeated once. In both experiments, all plants except uninoculated controls, died within 3 weeks after inoculation. P. palmivora was reisolated from diseased plants. In later greenhouse experiments, more than 50% of plants showed disease symptoms when adding 1,000 zoospores of P. palmivora per pot. ‘Ecco Yellow’ was more susceptible than ‘Flamenco Purple’. The pathogen was as aggressive as Fusarium avenaceum in pathogenicity studies. Since E. grandiflorum is grown on a limited scale in Norway, we lack experience with the economic impact of this disease in the cut-flower industry. To our knowledge, this is the first report of P. palmivora in E. grandiflorum.

Reference: (1) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996.
Identification of Magnaporthe oryzae Avirulence Genes to Three Rice Blast Resistance Genes
Authors: Luo C. X. , Fujita Y. , Yasuda N. , Hirayae K. , Nakajima T. , Hayashi N. , Kusaba M. , Yaegashi H.
Published: May 2007

The segregation of avirulence/virulence was studied in 115 F1 progeny isolates of Magnaporthe oryzae from a cross of two field isolates on three Japanese race-differential rice cultivars Kanto 51, Fukunishiki, and Toride 1. The χ2 tests of goodness-of-fit for a 1:1 ratio indicated that avirulence on cvs. Kanto 51, Fukunishiki, and Toride 1 was under monogenic control. The relationship between the avirulence (Avr) gene in the parental isolate and the Avr gene in the standard isolate was investigated by using 100 lines each of three F3 families from the crosses of the rice cultivars Norin 3/Kanto 51, AK61/Fukunishiki, and Norin 3/Toride 1, respectively. Based on the resistant reactions of the F3 rice lines to the parental isolates and the standard isolates harboring three known Avr genes, three genetically independent Avr genes, AvrPik, AvrPiz, and AvrPiz-t, were identified. The three identified Avr genes were mapped using random amplified polymorphic DNA (RAPD) analysis, and a partial linkage map was constructed with 17 RAPD markers closely linked to the Avr genes. Twelve markers and AvrPik, three markers and AvrPiz, and two markers and AvrPiz-t, as well as mating locus MAT1, constructed linkage groups A, B, and C, respectively.
First Report of the Root-Knot Nematode Meloidogyne marylandi on Turfgrasses in Israel
Authors: Oka Y. , Karssen G. , Mor M.
Published: May 2007

In a turfgrass nursery in Arava, Israel, a population of root-knot nematodes was isolated from poorly growing Zoysiagrass (Zoysia japonica Steud.) with symptoms of foliar chlorosis and roots with very small, smooth galls and protruding egg masses. The isolated population (genus Meloidogyne) included females and second-stage juveniles, whereas no males were observed. Measurements and morphological observations of 20 second-stage juveniles (body length = 423 ± 13 μm, dorsal gland orifice from stylet base = 2.6 ± 0.4 μm, tail length = 63 ± 3 μm, hyaline tail length = 12.4 ± 0.9 μm and hemizonid posterior to excretory pore) and 10 adult females (stylet length = 12.5 ± 0.7 μm, dorsal gland orifice from stylet base = 3.3 ± 0.5 μm, excretory pore to head end = 11.9 ± 1.3 μm and perineal patterns rounded to ovoid with coarse striae) conformed to the description of Meloidogyne marylandi Jepson and Golden (3). Additionally, the identification was confirmed when females and second-stage juveniles were compared with available paratype slides. The isozymes malate dehydrogenase (EC 1.1.1.37) and esterase (EC 3.1.1.1) of young, adult females were also different from those of other described root-knot nematode species, including M. graminis, a taxon closely related to M. marylandi (4). M. marylandi was discovered and described from Bermudagrass (Cynodon dactylon (L.) Pers) in Maryland in 1987. Outside the United States, it has only been isolated from Zoysia matrella in Japan (1,2,3). In host range tests with different turfgrasses, stolons with roots were inoculated after 1 week with 500 second-stage juveniles per plant and 6 weeks later, the produced egg-masses where counted. These tests showed that this root-knot nematode isolate reproduced on Z. japonica and Pennisetum clandestinum, while no egg masses were observed on the roots of Dactyloctenium australe, Paspalum vaginatum, and Stenotaphrum secundatum. Additionally, some cereals grown from seeds were tested. Wheat (Triticum aestivum), barley (Hordeum vulgare), and bristle oat (Avena strigosa) were infested with this nematode, while oat (A. sativa) was not. Although the origin of this root-knot nematode in Israel is unknown, it could have been distributed throughout the country with commercial turfgrass. To our knowledge, this is the first report of M. marylandi in Israel and outside the United States and Japan.

References: (1) M. Araki. Jpn. J. Nematol. 22:49, 1992. (2) A. M. Golden. J. Nematol. 21:453, 1989. (3) S. B. Jepson and A. M. Golden. Pages 263–265 in: Identification of Root-Knot Nematodes (Meloidogyne species). CAB International, Wallingford, U.K., 1987. (4) G. Karssen. The plant-parasitic nematode genus, Meloidogyne Göldi, 1892 (Tylenchida) in Europe. Brill, Leiden, the Netherlands, 2002.
First Report of Powdery Mildew Caused by Erysiphe cichoracearum on Creeping Thistle (Cirsium arvense) in North America
Authors: Newcombe G. , Nischwitz C.
Published: May 2007

Creeping or Canada thistle (Cirsium arvense (L.) Scop.) is a perennial weed of Eurasian origin that arrived in North America as early as the 1700s (3). Spreading by seeds and rhizomes, it is now widely distributed in Canada, Alaska, and 40 other states. It is apparently absent from Texas, Oklahoma, Louisiana, Mississippi, Alabama, Georgia, Florida, and South Carolina (1). Powdery mildew is common on C. arvense in Europe, but it has never been observed in North America (4). In Europe and Asia, powdery mildew of C. arvense is caused by any one of the following fungi: Leveillula taurica, two species of Sphaerotheca, and varieties of Erysiphe cichoracearum and E. mayorii. Specimens of C. arvense infected with powdery mildew (deposited in the U.S. National Fungus Collections as BPI 843471) were collected in the fall of 2003 near Moscow, ID and in two areas in Oregon (the canyon of the Grande Ronde River and near the base of the Wallowa Mountains). Mycelium and cleistothecia were observed on stems and upper and lower surfaces of leaves. The mean diameter of the cleistothecia was 122 (±11.6) μm. Basally inserted, mycelioid appendages were hyaline or brown and varied considerably in length, but most were in the range of 80 to 120 μm. Asci averaged 58 (±5.5) μm × 35 (±4.1) μm in length and width, respectively. Each ascus bore two ascospores averaging 23 (±1.4) μm × 14 (±1.7) μm. Conidia averaged 30 (±3.0) μm × 14 (±0.8) μm. The specimens fit the description of E. cichoracearum DC. (2). Because the length/breadth ratio of conidia is greater than 2, the specimens could be further diagnosed as E. cichoracearum var. cichoracearum (2). Also noteworthy was the presence of the hyperparasitic Ampelomyces quisqualis Ces. ex Schlechtend. E. cichoracearum is thought to be a cosmopolitan powdery mildew of broad host range, but this concept is difficult to reconcile with the absence of mildew on North American populations of C. arvense for more than 200 years.

References: (1) Anonymous. USDA Natural Resources Conservation Service Plants Profile for Cirsium arvense. On-line publication, 2003. (2) U. Braun. A monograph of the Erysiphales (powdery mildews), J. Cramer, Berlin-Stuttgart, 1987. (3) G. Cox. Alien Species in North America and Hawaii, Island Press, Washington, D.C., 1999. (4) D. F. Farr et al. Fungal Databases, Systematic Botany and Mycology Laboratory, ARS, USDA. On-line publication, 2003.
Isolation and Partial Nucleic Acid Characterization of a New Isolate ofPotato virus Vwith Distinct Biological and Serological Properties
Authors: Shiel P. J. , Miller L. , Slack S. A. , Berger P. H.
Published: May 2007

In vitro cultures of potato (Solanum tuberosum cv. Papa Amarillo) were imported into the United States and were subjected to routine pathogen screening for newly introduced varieties. These cultures indexed positive for several of the six viruses tested and thus were treated using standard methods for eliminating viruses in in vitro cultures. Although the therapy apparently freed the potato of the tested viruses, some of the cultures continued to exhibit mosaic symptoms when planted in the greenhouse. When examined by electron microscopy, these plants contained flexuous rods. Tested samples did not index positive with any potato virus-specific polyclonal antisera but reacted with the “universal” potyvirus monoclonal antibody. These results indicated that these samples were likely infected with an as yet undescribed potyvirus. Further investigation indicated that this virus is a new strain of Potato virus V (PVV) that is serologically distinct from the common strain. This is the first description of a distinct strain of PVV. This particular strain has diverged sufficiently from other isolates of PVV to no longer be detectable by some commonly used antisera, and therefore is a concern for the future restriction of PVV spread into regions of the world where it is not currently present.
Factors Affecting Pycnidium Production of Diaporthe citri on Detached Citrus Twigs
Authors: Mondal S. N. , Agostini J. P. , Zhang L. , Timmer L. W.
Published: May 2007

Melanose, caused by Diaporthe citri, produces black-to-reddish brown lesions on twigs, leaves, and fruit of citrus and reduces the external quality of fruit destined for the fresh market. Inoculum for infection is produced primarily in pycnidia formed on dead twigs, and conidia are dispersed by rainwater. In laboratory studies, the effect of moisture, temperature, twig size, and melanose severity on pycnidium production on detached twigs was investigated. Pycnidium production was greatest when twigs were soaked for 3 to 4 h on alternate days three times per week and the temperature was 28°C. Production was greatest on twigs 3 to 5 mm in diameter and less on thinner or thicker twigs. Pycnidium production was related linearly to melanose severity on the twigs, and almost no pycnidia were produced on asymptomatic twigs. In the field, pycnidium production was greatest on detached, melanose-affected twigs placed in the canopy monthly during January to April than it was on twigs placed in the canopy during other months. The largest number of pycnidia was produced from May to August when fruit is most susceptible. The number of pycnidia produced was related significantly to degree-days above 20°C and weakly related to cumulative rainfall. Knowledge of inoculum production peaks may assist in timing of pruning and fungicide sprays.
Genetic Variation Among Colletotrichum graminicola Isolates from Four Hosts Using Isozyme Analysis
Authors: Horvath B. J. , Vargas J. M.
Published: May 2007

Anthracnose basal rot (ABR) is a serious disease of turfgrasses that is caused by the pathogen Colletotrichum graminicola. The relationships of isolates causing ABR on turfgrasses to those causing disease on important crop hosts (maize, sorghum) remain unresolved. Genetic variation among isolates from annual bluegrass, creeping bentgrass, maize, and sorghum was evaluated based on host origin and geographic origin. Isozymes were used to estimate the genetic variation of the isolates. Five enzyme systems comprising 16 alleles from 5 loci were used. Allele frequencies, genetic distance, and linkage disequilibrium values were calculated for isolates based on both host and geographic origin. Isolates from creeping bentgrass and annual bluegrass were the most closely related based on Nei's genetic distance, while isolates from maize and sorghum were the most distantly related, consistent with their known species-level relationship. Isolates from annual bluegrass and creeping bentgrass had different genetic distances to isolates from both maize and sorghum. Annual bluegrass isolates from different geographic regions had the smallest genetic distance values observed in this study, indicating a very close relationship regardless of geographic origin. Based on these data, it appears that host origin, not geographic origin, plays a more important role in the genetic diversity of these fungi.
Occurrence of Arabis mosaic virus and Grapevine leaf roll associated virus-3 on Grapevines in Iran
Authors: Pourrahim R. , Ahoonmanesh A. , Farzadfar Sh. , Rakhshandehro F. , Golnaraghi A. R.
Published: May 2007

During 2001, a survey was conducted in vineyards in northwestern Iran and the eastern and western provinces of Azarbaijan, Zanjan, and Qazvin to detect the presence of Arabis mosaic virus (ArMV) and Grapevine leaf roll associated virus-3 (GLRaV-3). From December 2001 through March 2002, 5,352 dormant stem cuttings were collected. A portion of all stem cuttings was callused, rooted, potted, and grown in a greenhouse. Each sample was tested for the presence of ArMV and GLRaV-3 with specific antisera (Bioreba, Basel, Switzerland). Extracts of bark scrapings were prepared from the remaining portion of the dormant cuttings. After bud break of rooted cuttings, leaf extracts were prepared by the method used by Rowhani et al. (2). Dormant bark and leaf extracts were used with double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). Among the samples tested, ArMV and GLRaV-3 were found in 4.7 and 2.3% of the collection, respectively. Leaf extracts that had tested positive for ArMV using ELISA, were mechanically inoculated on the indicator host plants of Chenopodium amaranticolor, Cucumis sativus, and Petunia × hybrida. All plants developed local lesions that subsequently developed systemic chlorosis that is reported for ArMV. Biological assays confirmed the results of ArMV using ELISA. To confirm testing, a number of the samples that were found positive for GLRaV-3 in ELISA tests were tested by reverse transcription-polymerase chain reaction (RT-PCR) technique using previously described specific primers (1). The PCR reaction resulted in the specifically amplification of a 300-bp fragment of GLRaV-3 RNA. In cvs. White Keshmesh, Ghezel Ozum, Red Lal, Askari, and Red Kehsmesh, symptoms associated with GLRaV-3 were reduced growth with smaller leaves and shoots. By late summer, the leaves rolled downward and the interveinal areas of the leaves turned to red, while the principal veins remained green in cvs. Red Lal and Red Keshmesh. Symptoms associated with ArMV were reduced growth, shoots with short internodes, and leaf chlorosis and distortion. To our knowledge, this is the first report of ArMV and GLRaV-3 from grapevines in Iran.

References: (1) A. Nassuth et al. J. Virol. Methods 90:37, 2000. (2) A. Rowhani et al. Plant Dis. 81:799, 1997.
First Report of Sclerotium rolfsii on Common Chickweed in North Carolina
Authors: Hollowell J. E. , Shew B. B.
Published: May 2007

Common chickweed (Stellaria media (L.) Cyrillo) is a common weed species found in agricultural fields of northeastern North Carolina. Symptomatic plants of common chickweed were observed during a March 2001 survey of winter annual weed species in Perquimans County, NC. The plants were growing in a harvested peanut field with a known history of southern stem rot caused by Sclerotium rolfsii Sacc. Water-soaked, bleached stems and chlorotic leaves were collected from plants and brought to the laboratory for isolation. Small portions (1 to 2 cm) of symptomatic stems and entire leaves were rinsed with tap water and placed on potato dextrose agar (PDA). Developing colonies were transferred to obtain pure cultures. The rapidly growing cultures had coarse, white mycelium typical of S. rolfsii and produced abundant, small, round, brown sclerotia approximately 2.0 mm in diameter on the surface of the culture. Clamp connections were observed with microscopic examination of mycelia. Pathogenicity of isolates was tested by placing 4-mm-diameter agar plugs of 2-day-old fungal mycelium on stems of three mature, nonsymptomatic chickweed plants. Agar plugs without fungal mycelium were used for the control treatment. Plugs were held in place with self-sticking bandage gauze. Plants were misted with water, enclosed in plastic bags, and incubated on a laboratory counter top at ambient temperature (24°C). Abundant mycelia developed, and water-soaked lesions and necrotic stems were observed. Noninoculated plants remained healthy and free of signs and symptoms during the incubation period. The fungus was reisolated on PDA, and pure cultures of S. rolfsii were obtained. Koch's postulates confirmed common chickweed was a host of S. rolfsii. To our knowledge, this is the first report of common chickweed as a host of S. rolfsii. Crop species commonly used in peanut rotations (corn, small grains, sorghum, and cotton) do not support populations of S. rolfsii. Many dicotyledonous weed species have been reported as hosts of S. rolfsii, but our observation of active disease on a winter weed species was unexpected. Colonization of winter weed, if prevalent, may enhance survival of S. rolfsii between crops of susceptible hosts such as peanut.
First Report of Blueberry scorch virus in Cranberry in Canada and the United States
Authors: Wegener L. A. , Punja Z. K. , Martin R. R.
Published: May 2007

Blueberry scorch disease, caused by the carlavirus Blueberry scorch virus(BlScV), is a serious disease of highbush blueberry (Vaccinium corymbosum L.) in North America and Europe. Symptoms of BlScV infection in highbush blueberry include necrosis of flower blossoms and young leaves, shoot blight, and chlorosis. In June 2003, BlScV was detected for the first time in cranberry (Vaccinium macrocarpon L.) in Abbotsford, British Columbia, Canada using double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). Ten uprights were sampled from different locations in the bog, seven of which tested positive using DAS-ELISA. To confirm infection, total nucleic acid was extracted from infected cranberry leaf tissue according to an established protocol (2). Primers were developed against the published NJ-2 sequence of BlScV (GenBank Accession No. NC_003499). The forward primer, BS4586F (5′-CTTCAGGATGAGTGGTGCAA-3′), and the reverse primer, BS5164R (5′-CGCGTGCTGGAAGCATACAA-3′), were used in reverse-transcription polymerase chain reaction (RT-PCR) to amplify a portion of the RNA-dependent RNA polymerase gene of BlScV. The amplicons of the expected size were sequenced and the nucleotide sequence of the product showed 82% homology, and the predicted amino acid sequence had 91% homology with the published NJ-2 sequence. A random survey for BlScV in cranberry bogs in the Pacific Northwest Region of North America was conducted. Testing revealed the presence of BlScV in 7 of 42 bogs in British Columbia, Canada, 2 of 12 bogs in Oregon, and 3 of 18 bogs in Washington. Nucleotide sequencing of RT-PCR products of BlScV from a Washington bog showed 87 and 96% homology at the nucleotide and predicted amino acid level, respectively, in the methyltransferase of the NJ-2 strain using forward primer, BS276F (5′-CCGTCTGCAAGACATTAGAG-3′), and reverse primer, BS743R (5′-TCTTCTTCACCTCGTACTCG-3′). Several bogs had a high incidence of BlScV infection, with over 70% of the sampled uprights testing positive. Some infected cranberry bogs were adjacent to infected blueberry fields, while others were isolated. Transmission of the virus is likely to have occurred by aphids, which are known to be vectors of BlScV (1). Presently, BlScV appears to be asymptomatic in cranberry. To our knowledge, this is the first report of BlScV infecting cranberry. The potential for infection of other Vaccinium spp., such as lowbush blueberry (V. angustifolium Aiton), rabbiteye blueberry (V. ashei Reade), native Pacific Northwest species (V. membranaceum Douglas ex Torrey, V. ovatum Pursh, and V. parvifolium Smith), and ornamental Vaccinium spp. needs to be investigated.

References: (1) P. R. Bristow et al. Phytopathology 90:474, 2000. (2) D. W. Hughes and G. Galau. Plant Mol. Biol. Rep. 6:253, 1988.
First Report of the Association of a Nanovirus with Foorkey Disease of Large Cardamom in India
Authors: Mandal B. , Mandal S. , Pun K. B. , Varma A.
Published: May 2007

Large cardamom (Amomum subulatum Roxb.) is affected by the serious disease ‘foorkey’, which is of unknown etiology (1). Excessive sprouting and formation of bushy dwarf clumps at the base of mother plants that gradually die, characterize the disease. In surveys in the Sikkim-Darjeeling Hill area during 2002 and 2003, as much as 27% of plants were found to be affected. Electron microscopy of negatively stained, partially purified preparations from field-infected large cardamom plants showed the presence of isometric particles measuring 17 to 20 nm. The causal agent was successfully transmitted by the aphid Micromyzus kalimpongensis Basu, in a persistent manner. Ten randomly selected field samples gave A405 0.1 to 0.23 compared with 0.57 with positive control with enzyme-linked immunosorbent assay using antiserum to an Indian isolate of Banana bunchy top virus (BBTV). A fragment of approximately 850 bp was amplified from the diseased plants using polymerase chain reaction (PCR) with primers 5′-ATGGCGCGATATGTGGTATGC-3′ and 5′-TCAGCAAGAAAACCAACTTTATTC-3′, designed to amplify the putative Rep gene based on the sequences of DNA1 of BBTV. The PCR product was cloned and sequenced (GenBank Accession No. AY 485960) and showed 80 to 82% identity with the corresponding region of DNA1 of BBTV and 47.6 to 48.5% with other recognized nanoviruses. These findings indicate that a nanovirus is associated with ‘foorkey’ disease of large cardamom, which is tentatively named as Cardamom bushy dwarf virus.

Reference: (1) P. M. Varma and S. P. Capoor. Indian J. Agric. Sci. 34:56, 1964.
Distribution and Incidence ofIris yellow spot virusin Colorado and Its Relation to Onion Plant Population and Yield
Authors: Gent David H. , Schwartz Howard F. , Khosla Rajiv
Published: May 2007

Iris yellow spot virus (IYSV) is an emerging and potentially devastating disease of onion that was recently detected in Colorado and other onion producing regions in the western United States. In annual surveys, IYSV was confirmed in one of 18 fields (5.6%) in 2001, four of 24 (16.7%) in 2002, and 41 of 56 (73.2%) in 2003. IYSV was confirmed on volunteer onions in 2003 at all four locations where IYSV was observed in the onion crop the previous year. The disease was detected in six of seven western Colorado onion fields surveyed in 2003, but was not observed any year in southern or northeastern Colorado. The spatial variability of disease incidence, yield, and plant population also was mapped in two fields in 2003 using the global positioning system and a geographic information system. Disease incidence varied among cultivars, plant population, fields, and location in the field. Distinct disease gradients were observed in both fields with susceptible cultivars Teton and Granero, but not in the moderately resistant cultivar Sterling. In fields planted to the susceptible cultivars, disease incidence was highest on the field edges and lowest near the field centers. Plant population was negatively correlated with IYSV incidence in cultivar Sterling (R2= 0.56, P = 0.003), but not with the susceptible cultivars. Yield of jumbo market class onions, but not total yield, was negatively correlated with increasing IYSV incidence (R2= 0.37, P = 0.012) in cultivar Teton. Colossal market class yield, but not other yield components, was negatively correlated with IYSV incidence in cultivar Sterling (R2= 0.28, P = 0.061). The results of these studies indicate the distribution of IYSV is rapidly expanding in Colorado and is associated with a general reduction in bulb size.
Incidence of Postharvest Decay of ‘d'Anjou’ Pear and Control with a Thiabendazole Drench
Authors: Lennox Cheryl L. , Spotts Robert A. , Booyse Mardé
Published: May 2007

Postharvest decay causes losses to commercial pear industries. The incidence of decay in air and controlled-atmosphere (CA)-stored ‘d'Anjou’ pear fruit was investigated, and the effect of a prestorage thiabendazole drench on decay in CA-stored fruit was determined. In air storage, bull's-eye rot (31.37%) was most prevalent in 1996, whereas incidence of gray and blue mold (1996 and 1997) and bull's-eye rot (1997) were similar. Mucor, Alternaria, and Coprinus rot levels were low. Incidence of stem-end gray mold (2.58%) was significantly higher than calyx-end (0.73%) and puncture gray mold (0.61%). Incidence of gray mold (2.26%) was higher than all other decay in nondrenched CA-storage, and incidence of other decay types were similar. Incidence of puncture gray mold (1.13%) was higher than stem-end gray mold (0.84%), which in turn was higher than calyx-end gray mold (0.36%) in nondrenched CA-storage. Incidence of gray mold (1.04%) in CA-stored fruit was reduced by a prestorage thiabendazole drench. Drenching reduced stem-end (0.34%) and puncture gray mold (0.40%) but had no effect on all other decay or the total decay incidence. These results support the current recommendations of a single postharvest application of thiabendazole to control gray mold in ‘d'Anjou’ pear fruit.
Assessment of the Potential Year-Round Establishment of Soybean Rust Throughout the World
Authors: Pivonia S. , Yang X. B.
Published: May 2007

Soybean rust (Phakopsora pachyrhizi Sydow) has been known to occur in eastern Asia and Aus-tralia for decades. In recent years, the disease entered Africa and South America and has spread rapidly in these continents. It has become a concern to the U.S. soybean industry. To assess the threat of soybean rust, we used a modeling approach to determine the potential geographical zones where the fungus might overwinter and serve as source areas for seasonal epidemics. Long-term meteorological averages were used to assess the temperature stresses by using CLIMEX, and the dry stress with an algorithm developed in this study. Integration of stresses was used to predict the likelihood of survival of the rust in a defined location. Our results suggest that the new soybean rust invasions in Africa and South America occurred in the areas where the fungus might persist year-round. The main regions where rust has not been reported but might overwinter are located in the western hemisphere, including northern South America, Central America, the Caribbean, Mexico, southern Texas, and Florida. Southeastern China and neighboring areas are suggested as the primary regions where initial spores for soybean rust epidemics in central China are produced. If the disease is to establish in the United States, it is likely to be restricted to parts of Florida and southern Texas during the winter in the frost-free areas or areas where the fungus could overcome short periods of below-freezing temperatures. Occurrence of rust epidemics within the U.S. soybean belt would depend on south-to-north dispersal of uredospores.
Presence of Colletotrichum acutatum Causing Leaf Spot on Azalea japonica in Italy
Authors: Garibaldi A. , Bertetti D. , Vinnere O. , Gullino M. L.
Published: May 2007

Rhododendron cultivation has a long history in northern Italy where a wide selection of varieties and hybrids are grown. In the fall of 2002, a previously unknown disease was observed on Azalea japonica cv. Palestrina in several commercial farms in the Province of Verbania. Leaves showed irregular necrotic areas that were 1 mm in diameter. Lesions were dark brown to black and were surrounded by a chlorotic halo. Eventually, lesions coalesced, forming large irregular spots. Heavily infected leaves fell prematurely, resulting in severe defoliation. On the infected leaves, acervuli were present from which cylindrical tapered conidia measuring 4.8 to 7.2 × 11.0 to 22.8 μm at one end were released. Fifty conidia per isolate were measured. Fungus identified as Colletotrichum acutatum was consistently recovered from infected leaves, disinfested in 1% NaOCl for 1 min, and plated on potato dextrose agar amended with 100 mg/l of streptomycin sulfate. Pathogenicity of three fungal isolates was confirmed by inoculating healthy A. japonica (cvs. Palestrina and Snow) plants grown in plastic pots (18-cm diameter, 3 liters). Plants (five per treatment) were sprayed with a conidial suspension (1 × 106 conidia per ml) of the three isolates of C. acutatum. Noninoculated plants served as a control. Inoculated and control plants were covered with plastic bags to maintain high relative humidity conditions. All plants were maintained in growth chambers at 20 ± 1°C (12 h per day of fluorescent light). Six days after the artificial inoculation, plants developed typical symptoms on the leaves. C. acutatum was consistently reisolated from infected plants. The pathogenicity test was carried out twice. Sequencing of the internal transcribed spacer region of the rDNA and a portion of the β-tubulin gene were performed, and the obtained sequences were compared with those available in GenBank. Identification of the fungus as C. acutatum, therefore was confirmed. To our knowledge, this is the first report of the presence of C. acutatum on A. japonica in Italy. Although observed presently only in a few nurseries, the disease has the potential to spread, becoming more relevant in an area where rhododendron cultivation is economically important. Anthracnose on rhododendron has already been described in several countries (1,2).

References: (1) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St Paul, MN, 1989. (2) O. Vinnere et al. Mycol. Res. 106:60, 2002.
First Report of the Root-Knot Nematode Meloidogyne javanica on Buchu (Agathosma betulina) in South Africa
Authors: Malan A. P. , Knoetze R. , Hugo H. J.
Published: May 2007

Agathosma betulina, commonly known as buchu, has been used for centuries by the indigenous people of South Africa for medicinal purposes. Currently, the essential oils from buchu are used in medicine, food flavorings, and aromatic oils. Increased exploitation of natural growing buchu in the Fynbos biome and a worldwide shortage of buchu oil encouraged commercial cultivation in South Africa. The root-knot nematode (Meloidogyne spp.) is one of the most common plant-parasitic nematodes found on commercial crops grown in the Western Cape. It has also been isolated from the soil and roots of plants in the natural Fynbos vegetation (2). In June 2003, a nursery propagating buchu plants experienced problems with poor growth. Examination of the buchu roots under a stereo microscope showed extensive galling with large numbers of female root-knot nematodes with eggsacs. Nematode extractions of the soil were also done. Only second-stage juveniles of Meloidogyne spp. (311 per 250 ml of soil) were recovered. A polymerase chain reaction (PCR)-based diagnostic method (1) was used for the identification of the root-knot nematode species. Ten intact females were dissected from the roots and individually placed directly in 5 μl drops of 1× PCR reaction buffer (16 mM [NH4]2SO4, 67 mM tris-HCL, pH 8.8, 0.1% vol/vol Tween 20) ontaining 60 μg/ml of proteinase K. The tube was kept at -80°C for a minimum of 10 min. The tube was incubated at 60°C for 15 min and 5 min at 95°C. The PCR amplifications were then prepared directly in the same tube. Amplified DNA fragments were digested with HinfI and DraI. The digested DNA was loaded on a 2% agarose gel, separated by electrophoresis, and detected by ethidium bromide staining. The digested amplified DNA fragments correspond to those of Meloidogyne javanica. Morphological characteristics were used to verify the PCR-based identification of the nematode. To our knowledge, this is the first report of M. javanica causing extensive galling on the roots of Agathosma betulina. Visual damage to the roots indicates the root-knot nematode to be an important threat to the commercial cultivation of buchu.

References: (1) R. Knoetze. Potential of the polymerase chain reaction for the identification of plant-parasitic nematodes. M.Sc. thesis. University of Stellenbosch, Stellenbosch, South Africa, 1999. (2) A. J. Meyer, S. Afr. J. Enol. Vitic., 20:75, 1999.
Barley Yellow Dwarf Disease in Natural Populations of Dominant Tallgrass Prairie Species in Kansas
Authors: Garrett K. A. , Dendy S. P. , Power A. G. , Blaisdell G. K. , Alexander H. M. , McCarron J. K.
Published: May 2007

The grasses Sorghastrum nutans (Indian grass), Schizachyrium scoparium (little bluestem), Panicum virgatum (switchgrass), and Andropogon gerardii (big bluestem) are four of the most common plant species present in a tallgrass prairie (1). Infection with barley yellow dwarf virus (BYDV, family Luteoviridae) is of interest in these species because of the potential effects of the virus on tallgrass prairie plant communities and the potential for tallgrass prairie to function as a reservoir of the virus for infection in wheat or barley fields. In a previous inoculation experiment, an unidentified strain of BYDV transmitted by the aphid species Rhopalosiphum padi was reported to infect S. scoparium but none of the other three grass species (2). We sampled for the presence of five virus strains in at least 50 blooming plants of each grass species in a natural tallgrass prairie stand in August 2000. Samples were collected in watersheds that were designated 1B, 1D, K1A, 20B, and 20C at Konza Prairie Biological Station in the Flint Hills near Manhattan, KS. To detect the virus, we used enzyme-linked immunosorbent assay (ELISA) with antibodies purchased from Agdia (Elkhart, IN). For the PAV, MAV, RMV, and SGV strains, we used double-antibody sandwich ELISA with alkaline phosphatase label. For Cereal yellow dwarf virus (RPV), we used compound direct ELISA with alkaline phosphatase label. The scoring of ELISA results was based on comparison with infected and uninfected control plants of the same species. Symptoms of infection in the field were difficult to interpret visually, since plants in this natural environment often showed multiple symptoms of stress. None of the five strains were detected in 51 individuals of S. nutans. For 50 individuals of S. scoparium, the incidence of infection by the different strains was 4% for MAV, 0% for PAV, 2% for RMV, 0% for RPV, and 58% for SGV. For 51 individuals of P. virgatum, the incidence of infection was 31% for MAV, 0% for PAV, 0% for RMV, 0% for RPV, and 4% for SGV. For 64 individuals of A. gerardii, the incidence of infection was 59% for MAV, 0% for PAV, 0% for RMV, 0% for RPV, and 3% for SGV. The impact of BYDV on these tallgrass prairie species remains to be determined. The PAV strain is the most commonly reported strain in wheat in Kansas but was not recovered from these grass species.

References: (1) C. C. Freeman. The flora of Konza Prairie: A historical review and contemporary patterns. Pages 69–80 in: Grassland Dynamics. A. K. Knapp et al., eds. Oxford, 1998. (2) W. N. Stoner. Plant Dis. Rep. 60:593, 1976.
First Report of Black Soft Rot of Indian Gooseberry Caused by Syncephalastrum racemosum
Authors: Garg Neelima , Prakash Om , Pandey B. K. , Singh B. P. , Pandey G.
Published: May 2007

Indian gooseberry (Emblica officinalis Gaertn.) is a medicinal plant with high nutraceutical value. During November and December 2003, soft rot was noticed on harvested and stored (20 ± 5°C and 65 ± 5% relative humidity) fruits at the experimental farm in Rehmanhera, Lucknow, India (26°50′N, 80°54′E). These fruits had numerous, minute brown necrotic lesions showing white mycelial growth. A pronounced halo of water-soaked, faded tissue surrounded the lesion between the fringe of mycelium and healthy tissues. The rotted surface was covered with a black, powdery layer of spores. On Czapek yeast extract agar, fungal colonies were blackish grey, moderately dense, and covered the entire petri dish. The fungus produced aseptate mycelium. The sporangial heads were 30 to 50 μm in diameter with sporangiospores found linearly within cylindrical sacs (merosporangia) borne on spicules around the columella. Sporangiospores, spherical to cylindrical in shape and borne in chains, measured 3.0 to 5.0 μm long. The fungus was morphologically and physiologically identified as Syncephalastrum racemosum Schr. (2). For pathogenicity tests, healthy fruits (10 replicates) were surface sterilized and punctured inoculated aseptically with 1.0 × 106 conidia and incubated at 20 ± 5°C Typical symptoms of the disease appeared after 4 days. The fungus exhibited a strong level of cellulolytic activity as indicated by prolific growth on Indian gooseberry fiber waste under solid-state fermentation conditions. The level of cellulase activity (1) was 21 filter paper activity unit per ml at 72 hr in culture supernatant of basal medium having carboxymethyl cellulose as the carbon source. The fungus showed resistance to tannins (as much as 2%), since it could grow well in liquid growth medium (Czapek Dox broth) with 2% tannins and aonla juice with 1.8% tannins. Since Indian gooseberry is rich in fiber (2.5 to 3.4%) and tannins (1.5 to 2.0%), this may be an important pathogen. To our knowledge, this is the first report of the occurrence of Syncephalastrum racemosum on Indian gooseberry fruits.

References: (1) T. K. Ghose. Pure Appl. Chem. 59(2):257, 1987. (2) J. I. Pitt and A. D. Hocking. Fungi and Food Spoilage. Academic Press. North Ryde, Australia, 1985.
Double-Cropping Cucumbers and Squash After Resistant Bell Pepper for Root-Knot Nematode Management
Authors: Thies Judy A. , Davis Richard F. , Mueller John D. , Fery Richard L. , Langston David B. , Miller Gilbert
Published: May 2007

‘Charleston Belle’, a root-knot nematode-resistant pepper (Capsicum annuum var. annuum [Grossum Group]), and its susceptible recurrent parent, ‘Keystone Resistant Giant’, were compared as spring crops for managing the southern root-knot nematode (Meloidogyne incognita) in fall-cropped cucumber (Cucumis sativus) and squash (Cucurbita pepo) at Blackville, SC and Tifton, GA. ‘Charleston Belle’ exhibited minimal root galling and nematode reproduction, and ‘Keystone Resistant Giant’ exhibited severe root galling and high nematode reproduction. Cucumber grown in plots following ‘Charleston Belle’ had lower (P ≤ 0.001) root gall severity indices than following ‘Keystone Resistant Giant’ (4.2 versus 4.9, respectively). Cucumber yields were 87% heavier (P ≤ 0.0001) and numbers of fruit were 85% higher (P ≤ 0.0001) in plots previously planted to ‘Charleston Belle’ than to ‘Keystone Resistant Giant’. Squash grown in plots following ‘Charleston Belle’ had lower (P ≤ 0.001) root gall severity indices than following ‘Keystone Resistant Giant’ (4.0 versus 4.8, respectively). Squash yields were 55% heavier (P ≤ 0.01) and numbers of fruit were 50% higher (P ≤ 0.001) in plots previously planted to ‘Charleston Belle’ than to ‘Keystone Resistant Giant’. These results demonstrate that root-knot nematode-resistant bell pepper cultivars such as ‘Charleston Belle’ are useful tools for managing M. incognita in double-cropping systems with cucurbit crops.
Comparison of Whole-Tissue and Xylem Fluid Collection Techniques to Detect Xylella fastidiosa in Grapevine and Oleander
Authors: Bextine Blake R. , Miller Thomas A.
Published: May 2007

Xylella fastidiosa is the xylem-limited bacterium that causes Pierce's disease of grapevine and oleander leaf scorch. Detection of this pathogen prior to symptom development is critical for improved management of the disease. Enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) currently are used for routine detection of the pathogen; however, both detection methods are limited by low titer or patchy distribution of the bacterium within a host plant. In the study reported here, we directly compared X. fastidiosa detection in whole-tissue samples with xylem fluid samples from grapevine and oleander. Collection of xylem fluid samples improved sensitivity of pathogen detection by ELISA (41.0%) compared with whole-tissue samples (20.5%) in asymptomatic grapevine. Additionally, pathogen detection in asymptomatic grapevine by PCR also was improved when xylem samples were tested (66.7%) compared with whole-tissue samples (23.1%). There were no differences in frequency of detection of X. fastidiosa in symptomatic grapevines by ELISA or PCR dependent upon sample collection method. Assays of xylem fluid samples did not improve detection of X. fastidiosa in symptomatic or asymptomatic oleander compared with assays of whole tissue. Finally, in a direct comparison of ELISA and PCR, we found no significant differences in frequencies of positive grapevine or oleander samples detected.
Efficacy of Plant Growth-Promoting Rhizobacteria, Acibenzolar-S-Methyl, and Soil Amendment for Integrated Management of Bacterial Wilt on Tomato
Authors: Anith K. N. , Momol M. T. , Kloepper J. W. , Marois J. J. , Olson S. M. , Jones J. B.
Published: May 2007

Greenhouse experiments were conducted to study the effect of plant growth promoting rhizobacteria (PGPR; Bacillus pumilus SE 34, Pseudomonas putida 89B61, BioYield, and Equity), acibenzolar-S-methyl (Actigard), and a soil amendment with S-H mixture (contains agricultural and industrial wastes such as bagasse, rice husk, oyster shell powder, urea, potassium nitrate, calcium super phosphate, and mineral ash) on bacterial wilt incidence caused by Ralstonia solanacearum (race 1, biovar 1) in susceptible tomato (Lycopersicon esculentum cv. Solar Set). In experiments with PGPR, Pseudomonas putida 89B61 significantly reduced bacterial wilt incidence when applied to the transplants at the time of seeding and 1 week prior to inoculation with Ralstonia solanacearum. BioYield, a formulated PGPR that contained two Bacillus strains, decreased disease significantly in three experiments. Equity, a formulation containing more than 40 different microbial strains, did not reduced wilt incidence compared with the untreated control. With inoculum at low pathogen densities of 1 × 105 and 1 × 106 CFU/ml, disease incidence of Actigard-treated plants was significantly less than with nontreated plants. This is the first report of Actigard-mediated reduction of bacterial wilt incidence in a susceptible tomato cultivar. When PGPR and Actigard applications were combined, Actigard plus P. putida 89B61 or BioYield reduced bacterial wilt incidence compared with the untreated control. Incorporation of S-H mixture into infested soil 2 weeks before transplanting reduced bacterial wilt incidence in one experiment. Combination of Actigard with the S-H mixture significantly reduced bacterial wilt incidence in tomato in two experiments.
First Report of Plant-Parasitic Nematodes on Seashore Paspalum (Paspalum vaginatum) in Florida
Authors: Hixson A. C. , Crow W. T.
Published: May 2007

Seashore paspalum (Paspalum vaginatum Swartz) is a warm-season grass capable of growing in the saline environments present in coastal areas of Florida (2). A major limitation of cultivating turfgrasses in the sandy soils of Florida is the destruction of roots by plant-parasitic nematodes (3). A survey was performed to determine the plant-parasitic nematodes associated with seashore paspalum. Sampling locations ranged from Daytona Beach to Miami Beach on the eastern coast and from Tampa to Naples on the western coast. Soil samples were taken during the spring and summer months of 2002 and 2003 from different golf courses and home lawns. In 2002, soil samples were taken from five golf courses (37 samples) and seven home lawns (17 samples). In the next year, three golf courses (23 samples) and 13 home lawns (34 samples) were sampled. Nematodes were extracted from 100 cm3 soil samples using a modified centrifugal-sugar flotation technique (1). Ten genera of plant-parasitic nematodes were present from the samples obtained from golf courses. In addition, two more plant-parasitic nematode genera were present in samples from home lawns. The genera most frequently detected were Hoplolaimus, Mesocriconema, Hemicriconemoides, and Helicotylenchus, which were found at 100, 100, 88, and 88% of the golf courses surveyed and at 75, 95, 70, and 85% of the home lawns sampled, respectively. Genera Xiphinema, Pratylenchus, and Tylenchorhynchus, were found in less than 30% of the golf courses and less than 45% of the home lawns sampled. Genera Peltamigratus and Hemicycliophora were associated with a low percentage of the home lawns. A moderately high frequency of the genus Belonolaimus present in soil samples from golf courses (50%) and home lawns (40%) was consistent for other grasses grown in sandy soils associated with coastal areas in Florida (4). Populations of the genera Belonolaimus, Hoplolaimus, Helicotylenchus, Trichodorus, Hemicriconemoides, and Mesocriconema were above the action threshold levels for bermudagrass used by the University of Florida Nematode Assay Laboratory. Genera Hoplolaimus, Belonolaimus, and Trichodorus were associated with irregular-shaped yellowing and declining turfgrass areas sampled in this survey. Large populations of Helicotylenchus spp. (>500 nematodes per 100 cm3 of soil) were often found associated with seashore paspalum. To our knowledge, this is the first report of plant-parasitic nematodes associated with seashore paspalum in Florida.

References: (1) W. R. Jenkins. Plant Dis. Rep. 48:692, 1964. (2) J. Morton. Proc. Fla. State Hortic. Soc. 86:482, 1973. (3) V. G. Perry and H. Rhoades. Pages 144–149 in: Nematology in the Southern Region of the United States. Southern Cooperative Series Bull. 276, University of Arkansas Agric. Pub., Fayetteville, 1982. (4) R. T. Robbins and K. R. Barker. J. Nematol. 6:1, 1974.