bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiplex Detection of Criniviruses Associated with Epidemics of a Yellowing Disease of Tomato in Greece
Authors: Dovas C. I. , Katis N. I. , Avgelis A. D.
Published: May 2007

Since 1997, a yellowing disease has been observed in greenhouse tomato (Lycopersicon escu-lentum). By 2001, the disease was widespread, including open field tomato crops, and in most cases its incidence was 80 to 90% or even 100%. Epidemics in glasshouses were mainly associated with high populations of the whitefly Trialeurodes vaporariorum and Bemisia tabaci, the major whitefly pests in vegetable crops in Greece. The main leaf symptoms were severe yellowing, rolling, and brittleness. Samples from symptomatic plants were analyzed by polymerase chain reaction (PCR) and shown to be infected with Tomato infectious chlorosis virus (TICV) and Tomato chlorosis virus (ToCV) (family Closteroviridae, genus Crinivirus). TICV was found in 164 of 183 symptomatic samples, while ToCV was less representative (25/183). Sequence comparisons of the amplified 229-bp and 466-bp products revealed 99 and 100% identity with the reported sequences of TICV and ToCV, respectively. A reverse transcription (RT) multiplex PCR assay using a simple sample preparation procedure was developed to allow rapid, specific, and simultaneous detection of both ToCV and TICV sequences in two steps. The method involves a one-tube RT-PCR step in which the combination of primers amplifies part of the heat shock protein to homologue gene of both ToCV and TICV, followed by a multiplex nested PCR amplification. This is the first report of TICV and ToCV in Greece and, as far as we know, the first report of TICV in Europe.
Pattern Analysis of Sorghum Genotype × Environment Interaction for Leaf, Panicle, and Grain Anthracnose in Mali
Authors: Hess D. E. , Bandyopadhyay R. , Sissoko I.
Published: May 2007

Resistance to anthracnose, caused by Colletotrichum graminicola, in sorghum was identified through field screening at two locations (Samanko and Longorola) in Mali. The occurrence and progress of anthracnose were monitored on 19 sorghum lines plus resistant and susceptible checks in the 1996 to 1998 rainy seasons. Foliar anthracnose severity was assessed at regular intervals throughout the season. Area under the disease progress curve (AUDPC) was calculated for each genotype. Anthracnose severity was also evaluated on the peduncle, rachis and glumes, panicle, and grain. For the characters under study, the site × year and site × year × line interactions accounted for the genotype × environment interactions. Pattern analysis was applied to the environment-standardized matrix of genotype × environment means to analyze these interactions and elucidate genotypic adaptation. None of the lines was completely (hypersensitive) resistant to the disease, but 12 showed high levels of stable resistance to both foliar and panicle anthracnose. Only one was moderately susceptible to both forms of the disease. In addition to identifying varieties that can be grown in zones to which they are adapted, additional genotypes were identified that can serve as sources of resistance in regional breeding programs.
Recent Outbreak of Soybean Stem Canker Caused by Diaporthe phaseolorum var. caulivora in the Main Soybean-Producing Region of Argentina
Authors: Pioli R. N. , Morandi E. N. , Luque A. , Gosparini C. O.
Published: May 2007

The first report of soybean stem canker (SSC) caused by Diaporthe phaseolorum var. caulivora in South America was published in 2001, and was based on an isolate obtained in 1999 at Oliveros, Santa Fe (32°33′S, 60°51′W), Argentina (2). During the 2001 to 2002 growing season, isolates of D. phaseolorum var. caulivora were obtained from stems of field-grown soybeans (Glycine max L.) exhibiting SSC symptoms. Isolates were collected in three localities of the main soybean-producing region of Argentina: Marcos Juárez, Córdoba (32°66′S, 62°10′W); Salto, Buenos Aires (34°20′S, 60°33′W); and Diego de Alvear, Santa Fe (34°21′S, 62°10′W), and disease incidence in the fields was 10 to 60%, 5 to 15%, and 10 to 20%, respectively. The pathogen was isolated on potato glucose agar acidified with 0.2% lactic acid cultured in the dark at 25 ± 1°C. White colonies with compact and tufted mycelium were produced and turned yellow and light tan after 6 days. Appressed and fluffy mycelia were observed in old cultures. Stromata (2 mm diameter) were produced but pycnidia were not detected. After 20 days in culture at 25 ± 1°C under a 12-h light and 12-h dark regime, clustered perithecia developed on stem segments. For each isolate, 10 perithecia, 90 asci, and 30 bicellular, biguttulate ascospores were measured. Averages of asci length and width were 28.3 ± 2.3 and 5.9 ± 0.7 μm, respectively. Averages of ascospores mean length and width were 8.4 ± 0.6 and 2.5 ± 0.4 μm, respectively. These measures were similar to the measures obtained previously (2). Based on these features, the new isolates were classified as D. phaseolorum var. caulivora (Athow & Caldwell). Clustered perithecia, smaller asci and ascospores, and the development of fluffy mycelia with age were the main characteristics that distinguished D. phaseolorum var. caulivora from D. phaseolorum var. meridionalis (1). Pathogenicity trials were performed on cvs. Tracy M, Crockett, Hutchenson, and RA 702 in the greenhouse by placing a small amount of mycelium in soybean seedling hypocotyls wounds made with a scalpel. The pathogen was reisolated from stem portions of the symptomatic plants. Control plants remained healthy. The results reported here show that D. phaseolorum var. caulivora is widely disseminated in the main soybean-producing region of Argentina, where it coexists with D. phaseolorum var. meridionalis (2). The coexistence of both varieties indicates pathogen variability in the region is higher than previously recognized.

References: (1) R. N. Pioli et al. Plant Dis. 83:1071, 1999. (2) R. N. Pioli et al. Plant Dis. 85:95, 2001.
First Report of Tulip band breaking virus in Mosaic Diseased Tulip in Japan
Authors: Se T. , Kanematsu S.
Published: May 2007

Tulip (Tulipa spp.) is an ornamental plant of major economic importance in Japan. Regions in Toyama Prefecture are some of the most productive for producing tulip bulbs, shipping approximately 50 million bulbs annually. However, mosaic diseases caused by viruses such as Tulip breaking virus (TBV) currently limit bulb production in these areas. Only the potyviruses TBV and Lily mottle virus (LMoV) have been reported infecting tulip in Japan. A virus isolate from tulip with flower-breaking symptom in Toyama Prefecture was tentatively named OE4 and was presumed to be LMoV after detection by LMoV-specific reverse transcription-polymerase chain reaction (RT-PCR) (4). When OE4 was mechanically inoculated on test plants (13 species from six families), RT-PCR confirmed that it infected plants in the Liliaceae (Tulipa spp., Lilium formosanum, and L. concolor) with mosaic symptoms but did not induce any symptoms in Chenopodium quinoa, Tetragonia tetragonoides, and Nicotiana benthamiana. According to Dekker et al. (2) LMoV and Tulip band breaking virus (TBBV) infected Tulipa spp. and TBBV did not infect C. quinoa, T. tetragonoides, N. clevelandii, and N. benthamiana, species that were local or systemic hosts for LMoV. To analyze the genomic sequence of OE4, a primer set was designed for amplifying the coat protein (CP) gene of LMoV, with 5′ -GCAAATGAGACACTCAATG-3′ as a forward primer and 5′-TTACATAGAAATTCCAAGTAAG-3′ as a reverse primer. The fragment obtained was cloned and sequenced (DDBJ/EMBL/GenBank Accession No. AB078007). The CP gene of OE4 consisted of 825 nucleotides and had 86.5% identity (90.6% identity in deduced amino acid sequence) with the CP gene of LMoV-Netherlands (S44147) (3). When it was compared with partial sequences (277 nucleotides) of LMoV (S60810) and TBBV (S60805) (2), the nucleotide sequence identities were 89.9 and 96.4%, respectively. Multiple alignment and a phylogenetic tree based on the 277 nt of the tulip potyviruses, including OE4, showed the close relationship between OE4 and TBBV. These results indicated that OE4 was an isolate of TBBV. However, the CP amino acid sequence identity between TBBV and LMoV was more than 80%, and it seemed logical that TBBV be assigned to a strain of LMoV, according to potyvirus species demarcating criteria (1). Another screening using RT-PCR based detection, and an inoculation test for 55 flower-breaking tulips collected from fields in Toyama Prefecture revealed that four tulip plants were infected with TBBV and 54 with TBV. This suggests that TBV is more prevalent than TBBV, and we need to produce an attenuated virus of TBV, which will be effective for managing tulip breaking disease in the prefecture.

References: (1) P. H. Berger et al. Family Potyviridae. Pages 703–724 in: Virus Taxonomy. Academic Press, San Diego, CA, 2000. (2) E. L. Dekker et al. J. Gen. Virol. 74:881, 1993. (3) S. A. Langeveld et al. J. Gen. Virol. 72:1531, 1991. (4) T. Se and S. Kanematsu. Ann. Phytopathol. Soc. Jpn. 64:420, 1998.
First Report of Peach latent mosaic viroid on Peach in Uruguay
Authors: Herranz M. C. , Maeso D. , Soria J. , Pallás V.
Published: May 2007

Peach latent mosaic viroid (PLMVd) (2) is widely distributed and causes yellow, chlorotic mosaics and delayed foliation, flowering, and ripening. Infected fruits display a cracked suture and are often dented, misshapen, frequently flattened, and discolored. In the greenhouse, PLMVd natural isolates are divided into severe or latent strains depending on whether they induce leaf symptoms on seedlings of the peach indicator GF-305. PLMVd was detected in 2001 during a survey in three locations in the Canelones Department, the main peach producing area in Uruguay. Fifty samples were tested for the presence of five viruses: Prunus necrotic ringspot virus (PNRSV), Prune dwarf virus (PDV), American plum line pattern virus (APLPV), Plum pox virus (PPV) and Apple chlorotic leaf spot virus (ACLSV); samples were also tested for the viroids affecting stone fruits, Hop stunt viroid (HSVd) and PLMVd. The analyses were completed with molecular hybridization using specific nonisotopic riboprobes for each virus (4). PLMVd, undescribed in Uruguay, was detected in 9 of 50 samples in three peach cultivars, Scarlet Pearl, EarliGrande, and Barcelo. The PLMVd-positive sample for ‘Scarlet Pearl’ showed mild mosaic symptoms on leaves whereas the two PLMVd-positives of ‘EarliGrande’ showed clear calico type symptoms. The remaining PLMVd-positive samples belonged to ‘Barcelo’ and showed no symptoms or mild chlorosis. The first two cultivars were imported from the United States, a source with a high percentage of PLMVd infections in peach germ plasm (1). In five of nine PLMVd-positive samples, the viroid occurred with PNRSV and in one with PDV and PNRSV. PLMVd has previously been reported in Brazil (3), but to our knowledge, this is the first report of PLMVd in Uruguay. These results reveal the importance of following strict sanitary practices with plant material used for propagation. Molecular tools are available to prescreen scion and rootstock sources for PLMVd.

References: (1) M. L. Badenes and G. Llácer. Acta Hortic. 309:565, 1998. (2) R. Flores et al. Res. Virol. 141:109, 1990. (3) A. Hadidi et al. Plant Dis. 81:154, 1997. (4) V. Pallás et al. Detection of plant RNA viruses by non-isotopic dot-blot hybridization. Pages 461–468 in: Plant Virus Protocols: From Virus Isolation to Transgenic Resistance. G. Foster and S. Taylor, eds. Humana Press, Totowa, NJ. 1998.
Virus Coat Protein Transgenic Papaya Provides Practical Control of Papaya ringspot virus in Hawaii
Authors: Ferreira S. A. , Pitz K. Y. , Manshardt R. , Zee F. , Fitch M. , Gonsalves D.
Published: May 2007

Since 1992, Papaya ringspot virus (PRSV) destroyed nearly all of the papaya hectarage in the Puna district of Hawaii, where 95% of Hawaii's papayas are grown. Two field trials to evaluate transgenic resistance (TR) were established in Puna in October 1995. One trial included the following: SunUp, a newly named homozygous transformant of Sunset; Rainbow, a hybrid of SunUp, the nontransgenic Kapoho cultivar widely grown in Puna, and 63-1, another segregating transgenic line of Sunset. The second trial was a 0.4-ha block of Rainbow, simulating a near-commercial planting. Both trials were installed within a matrix of Sunrise, a PRSV-susceptible sibling line of Sunset. The matrix served to contain and trace pollen flow from TR plants, and as a secondary inoculum source. Virus infection was first observed 3.5 months after planting. At a year, 100% of the non-TR control and 91% of the matrix plants were infected, while PRSV infection was not observed on any of the TR plants. Fruit production data of SunUp and Rainbow show that yields were at least three times higher than the industry average, while maintaining percent soluble solids above the minimum of 11% required for commercial fruit. These data suggest that transgenic SunUp and Rainbow, homozygous and hemizygous for the coat protein transgene, respectively, offer a good solution to the PRSV problem in Hawaii.
An Algorithm for Predicting Outbreaks of Sclerotinia Blight of Peanut and Improving the Timing of Fungicide Sprays
Authors: Langston D. B. , Phipps P. M. , Stipes R. J.
Published: May 2007

Algorithms were evaluated for computing disease risk and improving the timing of fungicide applications for control of Sclerotinia blight of peanut. Disease risk was calculated by multiplying indices of moisture, soil temperature, vine growth, and canopy density each day, and summing values for the previous 5 days to obtain a 5-day risk index (FDI). After fungicide application, the FDI was reset to zero for 3 weeks. Fluazinam at 0.58 kg a.i./ha applied at FDI 24 or 32 in 1994 and 1995 suppressed disease and increased yield as much as or more than programs of weekly scouting and applying fungicide at the initial onset of disease with additional sprays at 3- to 4-week intervals. The FDI algorithm was also more efficient than calendar sprays at 60, 90, and 120 days after planting (DAP). Environmental and host parameters were expanded in 1996 and 1997 by adding new temperature and new vine growth indices. These parameters along with DAP-dependent thresholds consistently improved the timing of fungicide sprays and disease management when using the FDI algorithm in comparison to weekly scouting or calendar sprays at 60, 90, and 120 DAP.
Characterization ofAgrobacterium vitisStrains Isolated from Turkish Grape Cultivars in the Central Anatolia Region
Authors: Argun N. , Momol M. T. , Maden S. , Momol E. A. , Reid C. L. , Çelek H. , Burr T. J.
Published: May 2007

Crown gall was detected in several vineyards in the Central Anatolia region of Turkey. Vineyards were planted to cultivars of grape that originated in Turkey and that were not grafted. The predominant species isolated from galls consisted of tumorigenic strains of Agrobacterium vitis. They were identified based on reactions to standard biochemical and physiological tests, by polymerase chain reaction amplification of specific Ti plasmid and chromosomal sequences, and by reaction to a species-specific monoclonal antibody. All strains utilized octopine, suggesting that they may carry similar types of Ti plasmids. Some of the strains exhibited a differential host range compared with others and were less virulent based on the numbers of galls that they induced on grape. When grapevines were treated with nontumorigenic A. vitis strain F2/5 prior to inoculation with the Turkish A. vitis strains, crown gall was effectively controlled. The genetic diversity of strains was evaluated by comparing DNA fingerprints that were generated by restriction enzyme digestion of the intergenic spacer region that lies between 16S and 23S rRNA genes. They segregated into two main groups, one that is similar to previously identified A. vitis strains carrying octopine type Ti plasmids and one that was more similar to strains carrying nopaline and vitopine Ti plasmids. The strains of A. vitis from Turkey may represent ancestral forms of the pathogen that will provide insight into the evolution of the bacterium.
Occurrence of Tobacco streak virus on Peanut (Arachis hypogaea) in India
Authors: Reddy A. S. , Rao R. D. V. J. Prasada , Thirumala-Devi K. , Reddy S. V. , Mayo M. A. , Roberts I. , Satyanarayana T. , Subramaniam K. , Reddy D. V. R.
Published: May 2007

A virus disease of peanut (groundnut, Arachis hypogaea L.), characterized by necrosis of the stem and terminal leaflets followed by death, caused severe crop losses in Andhra Pradesh, India during the rainy season of the year 2000. The disease was referred to as peanut stem necrosis disease (PSND). Cowpea (Vigna unguiculata, cv. C-152) and Phaseolus vulgaris (cv. Topcrop) were found to be suitable for propagating the virus. In laboratory inoculation tests, the virus was found to infect a large number of plants. In laboratory tests, the virus was transmitted by the thrips Frankliniella schultzei. Virus particles were purified by differential centrifugation and sucrose density gradient centrifugation from infected cowpea plants and were used to elicit the production of a rabbit polyclonal antiserum with high titer. Extracts of infected plants reacted with antiserum to Tobacco streak virus (TSV). Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of proteins extracted from purified virus particles showed them to contain a major protein of 28 kDa and a minor, though prominent, protein of 57 kDa. Gel electrophoresis of RNA extracted from virus particles resolved it into four species with estimated sizes of 3.7, 3.1, 2.2, and 0.9 kb. Complementary DNA (cDNA) was made using as template a sample of the 2.2-kb RNA 3 and as primer an oligonucleotide complementary to sequence in RNA 3 of TSV. Following second strand synthesis, the cDNA was cloned in pBluescript and the nucleotide sequence was obtained for 868 nt of the cDNA. The sequence was 88.4% identical to the sequence in RNA 3 of TSV (strain WC). The results indicate that the causal agent of PSND is TSV. The same virus also was found to cause sunflower necrosis, an economically important disease in India. Studies on the epidemiology of PSND and the identification of virus-resistant peanut genotypes have been initiated to devise strategies to control PSND.
First Report of Leaf Blight Caused by Alternaria longipes on Carrots in Israel
Authors: Vintal H. , Shtienberg D. , Shlevin E. , Ben-Noon E.
Published: May 2007

Alternaria leaf blight, caused by Alternaria dauci (Köhn) Groves & Skolko, is one of the most devastating foliar pathogens of carrots (Daucus carota L.). Lesions appear as minute, necrotic, dark brown spots often initiated on the edge of the leaflet blade. They later enlarge in size and may merge into a large necrotic area, causing shriveling of the entire leaflet (1). In summer 2000, observations made in several carrot fields in the northwestern part of the Negev Region in Israel revealed infections that were atypical for A. dauci because they were initiated primarily in the middle section of the leaflet blade and were surrounded by a large yellowish area. A. longipes (Ellis & Everh.) E. Mason was consistently isolated from the lesions. Occasionally both A. longipes and A. dauci developed on the same leaves. The two pathogens differed in conidial morphology (size and shape of spore and beak) when cultured on potato dextrose agar medium. One hundred conidia of each species were measured. A. dauci conidia were 100 to 450 μm long and 6 to 15 μm wide, with a beak of up to 3 times the length of the conidium; A. longipes conidia were 35 to 110 μm long and 11 to 21 μm wide, and the beak measured one-third to one-half the length of the conidium. These measurements corresponded to the sizes listed previously (2). Inoculation of greenhouse-grown plants and completion of Koch's postulates confirmed that A. longipes is pathogenic to carrots. Conidia of both species germinated at temperatures from 5 to 36°C. In vitro tests revealed that A. longipes was less sensitive than A. dauci to fungicides commonly used in Israel in carrot fields. A fifty percent effective dose of chlorothalonil and difenoconazole was 3.0 and 0.2 μg a.i./ml, respectively, for mycelia growth of A. dauci, whereas the corresponding values for A. longipes were 10.5 and 3.0 μg a.i./ml, respectively. The prevalence of A. longipes in carrot fields and the influence of this pathogen on yields are currently not known.

References: (1) I. Barash et al. Physiol. Plant Pathol. 19:7, 1981. (2) M. B. Ellis. Dematiaceous Hyphomycetes. CMI. Kew, Surrey, England, 1971.
Identification of Pantoea stewartii subsp. stewartii by PCR and Strain Differentiation by PFGE
Authors: Coplin David L. , Majerczak Doris R. , Zhang Yongxiang , Kim Won-Sik , Jock Susanne , Geider Klaus
Published: May 2007

Stewart's bacterial wilt and leaf blight of sweet corn and maize is caused by Pantoea stewartii subsp. stewartii. This bacterium can be seed transmitted at a low frequency, so it is subject to quarantine restrictions by many countries. To develop a polymerase chain reaction assay for the identification of this pathogen from field samples and for use in seed health tests, four primer pairs were tested. These were selected from the sequences of hrpS, cpsDE, and the 16S rRNA intergenic transcribed spacer (ITS) region. Under optimal reaction conditions, about 20 and 200 cells of P. stewartii could be detected in pure cultures and leaf lesions, respectively. Other plant-associated enteric bacteria (e.g., P. agglomerans pv. herbicola, P. ananas, Erwinia amylovora, and E. carotovora) either did not produce amplicons or they were not the correct size for P. stewartii. To test further for possible false positives, 29 yellow-pigmented bacteria, mainly other Pantoea spp., were isolated from lesions on old corn leaves and assayed with the ITS primer sets. Except for weak, variable reactions with three P. ananas strains, the bacteria did not test positive. Pulsed field gel electrophoresis (PFGE) was evaluated as an additional test to confirm the identity of P. stewartii. After digestion with SpeI and XbaI, P. stewartii strains could be easily distinguished from related Erwinia and Pantoea spp. and each other.
Reactions of Accessions in the Annual Medicago Core Germ Plasm Collection to Erysiphe pisi
Authors: Yaege J. R. , Stuteville D. L.
Published: May 2007

Reaction to Erysiphe pisi was evaluated in the annual Medicago core germ plasm collection of 199 USDA Plant Introduction accessions from 33 species. Seedlings at the first trifoliolate leaf stage were inoculated with conidia and maintained in growth chambers for 21 days at 20°C, 70 to 90% relative humidity, and a 12-h photoperiod. Beginning 4 days after inoculation, plants with the first sign of powdery mildew were recorded and removed daily. Results for each accession were presented as the percentage of plants mildew-free 21 days after inoculation and also as area under the disease progress curve (AUDPC) values expressed as standardized proportion/days. AUDPC values were useful to account for length of latent period (number of days from inoculation until first sign of mildew). Thirty-two accessions from 14 species included plants mildew-free 21 days after inoculation. Mildew-free plants in those 32 accessions ranged from 100% in M. heyniana PI 537136 and M. truncatula PI 292436 down to 1% in six accessions. All plants in 87 accessions, which included all accessions of 11 species, had powdery mildew 4 days after inoculation and thus expressed no resistance. The remaining 80 accessions included slow-mildewing plants with latent periods of 5 to 14 days. This slow-mildewing trait may be a useful source of resistance to E. pisi.
First Report of Botryosphaeria dothidea and B. obtusa on Apple in Bolivia
Authors: Kaiser W. J. , Rivero V. G. M. , B. E. Valverde , Yerkes L.
Published: May 2007

Gala and Winter Banana apples are important commercial crops in Azurduy and Lima Bamba, which are located in the Department (state) of Chuquisaca, Bolivia. White or bot rot (causal agent Botryosphaeria dothidea (Moug.:Fr.) Ces. De. Not. [anamorph Fusicoccum aesculi Corda]) and black rot (causal agent B. obtusa (Schwein.) Shoemaker [anamorph Sphaeropsis malorum Berk.]) have not been reported previously from Bolivia. Both fungi were isolated from apple fruit and branch cankers in Azurduy, but only B. dothidea was isolated from rotted fruit and limb cankers in Lima Bamba. Both fungi also were isolated from rotted Gala and Winter Banana fruit purchased in the markets in Sucre, Bolivia. Symptoms on fruit consisted of light-to-dark brown lesions that ranged from 3- to 8-cm in diameter. Cankers on limbs were sunken and reddish brown and ranged from 2 to 25+ cm in length and 0.5 to 3 cm in diameter. Neither pathogen produced pycnidia in lesions on rotted fruit, but they often developed in branch cankers. Pseudothecia of B. dothidea and B. obtusa were not observed. Identification of both pathogens was based on descriptions of their anamorphic stages (1). To fulfill Koch's postulates, four healthy Gala apple fruit were inoculated with two isolates of each pathogen by wounding the opposite faces of surface-disinfected fruit with a 5-mm-diameter cork borer and inserting mycelial plugs of the pathogens. Plugs were obtained from the margins of cultures growing on potato dextrose agar (PDA). Wounds were made on the opposite sides of each fruit, a mycelial plug of one of the pathogens was inserted in one wound, and on the opposite side, a plug of sterile PDA was inserted as a control. Each plug containing fungal mycelium or sterile PDA was covered with a plug of trimmed apple tissue, and the apple fruit were incubated in a moist chamber at 17 to 20°C for 10 days. Six branches on two young apple trees growing outdoors in a nursery were inoculated in a similar manner with one isolate of each pathogen: bark was wounded with a 5-mm-diameter cork borer, and the wounded area was inoculated with a plug of PDA containing the pathogen or a plug of sterile PDA for the control. The inoculated sites were wrapped with masking tape to prevent dehydration. Within 10 days, all fruit wounds inoculated with isolates of each pathogen developed brown lesions up to 5 cm in diameter. Each pathogen was reisolated from tissues in which it had been inoculated, but not from any of the noninoculated control sites. Within 6 to 8 weeks, all but one wound on branches inoculated with each pathogen developed depressed canker lesions up to 2 cm in length. Each pathogen was reisolated from the canker produced by inoculation with that pathogen, but not from any of the control sites.

Reference: (1) T. B. Sutton. White rot and black rot. Pages 16–20 in: Compendium of Apple and Pear Diseases, A. L. Jones and H. S. Aldwinckle, eds. The American Phytopathological Society, St. Paul, MN, 1991.
The Association of Begomovirus with Bitter Melon in India
Authors: Khan J. A. , Siddiqui M. K. , Singh B. P.
Published: May 2007

Bitter melon, Momordica charantia (Cucurbitaceae), is a vegetable of nutritive and medicinal value that is cultivated throughout India and other tropical countries. In September 2001, a severe disease of bitter melon with virus-like symptoms was observed at Lucknow, India. Symptoms consisted of upward curling, shortening, and distortion of leaves. Diseased melon fruits were stunted and deformed. Disease incidence was as high as 100%. Whitefly (Bemicia tabaci) can transmit the associated virus from diseased bitter melon to Nicotiana tabacum cv. White burley. The development of leaf curl symptoms in N. tabacum indicated the pathogen could be a begomovirus. Total nucleic acids were extracted from diseased bitter melon leaves, and polymerase chain reaction (PCR) tests were performed. Three pairs of primers, AV494 and AC1048 (1), CL-CR/F2 and CL-CR/R2, CL/11F and CL10/R (2), specific to DNA-A of begomoviruses were used in PCR. Virus-specific DNA-A fragments of expected sizes were identified (≈0.5, 0.7 and 1.2 kb, respectively). The presence of a begomovirus in all PCR-amplified DNA fragments was confirmed by Southern hybridization. Cloned DNA-A fragments of Tomato leaf curl virus and Cotton leaf curl virus (both begomoviruses) cross-hybridized with the PCR products gave strong signals under high stringency conditions. These data suggest that a begomovirus is associated with this bitter melon disease. Watermelon mosaic 1 virus is the only virus previously reported to naturally infect bitter melon; however, this virus has not been identified in India. Bitter melon is also an experimental host of Ribgrass mosaic virus (genus Tobamovirus) and Trichosanthes mottle virus (genus Potyvirus). To our knowledge, this is the first report of the occurrence of begomovirus infecting bitter melon.

References: (1) S. D. Wyatt and J. K. Brown. Phytopathology 86:1288, 1996. (2). X. Zhou et al. J. Gen. Virol. 79:915, 1998.
Occurrence of Lily mottle virus in Escarole
Authors: Lisa V. , Vetten H. J. , Lesemann D.-E. , Gotta P.
Published: May 2007

Lily mottle virus (LMoV), genus Potyvirus, an important virus of lily that also causes flower-breaking in tulip (1), is considered to have a natural host range restricted to the family Liliaceae. In 1996, escarole (Cichorium endivia L. var. latifolium LAM) plants growing in fields close to Torino, Italy, and showing mosaic and necrotic spots on outer leaves were infected by a potyvirus related to LMoV. The virus was identified by immunoelectron microscopy (IEM) done on experimentally infected Nicotiana benthamiana and Chenopodium quinoa. The virus isolated from escarole (LMoV-E) had an experimental host range similar to that of lily isolates of LMoV, although species within the Liliaceae were not tested. LMoV-E systemically infected all nine escarole cultivars and six of seven endive cultivars (C. endivia L. var. crispum LAM) but did not infect any of six lettuce and two chicory cultivars (C. intybus L. var. foliosum HEGI). Symptoms ranged from mild to severe mosaic and were generally more severe on escarole than on endive. Some of the same escarole, endive, and lettuce cultivars were inoculated with a typical LMoV isolate from lily (Le97/49, from A. F. L. M. Derks, the Netherlands), which induced mild systemic infections in only one escarole and one endive cultivar. Both cultivars were also susceptible to LMoV-E. LMoV-E was purified from N. benthamiana, and an antiserum was prepared. IEM decoration titer experiments were done with LMoV-E and four other LMoV isolates from Liliaceae and their homologous antisera. Heterologous titers ranging from identity to serological differentiation index values of 2 to 4 were obtained, confirming the identity of the escarole isolate as a LMoV strain and indicating considerable serological variability among LMoV isolates. In a field survey of endive and escarole crops in 1998, in the area where LMoV-E was first identified, the virus was again detected by enzyme-linked immunosorbent assay in 4 of 80 escarole plants tested. LMoV-E appears to be a LMoV strain particularly adapted to escarole. To our knowledge, this is the first report of LMoV identified in a naturally infected host outside monocotyledonous plants.

Reference: (1) E. L. Dekker et al. J. Gen. Virol. 74:881, 1993.
Evaluation of Composts for Suppression of Dollar Spot (Sclerotinia homoeocarpa) of Turfgrass
Authors: Boulter Jeanine I. , Boland Greg J. , Trevors Jack T.
Published: May 2007

The use of composts in turfgrass disease management allows for a reduction in pesticide use in chemical control practices. Disease suppressive properties of composts rely on a number of factors including microbial activity, microbial population dynamics, nutrient concentrations, and other associated chemical and physical factors. Five composts were evaluated for suppression of dollar spot caused by Sclerotinia homoeocarpa. The dollar spot disease suppressive properties of selected compost formulations prepared in different years was evaluated. A third objective was to examine the effects of storage of compost (1 year) on the suppression of dollar spot. Field experiments were conducted in 1998 with compost prepared in 1997 to 1998. Applications of compost every 3 weeks throughout the season suppressed dollar spot of turf to levels not significantly different than applications of chlorothalonil fungicide applied at the manufacturer's lowest recommended preventative rate of 38.4 ml a.i./100 m2 every 2 weeks (P = 0.05). Single applications of composts at the start of the 1998 season were not effective in reducing disease. Field experiments in 1999 evaluated batches of two selected compost formulations, one batch produced in 1998 to 1999, another stored since production in 1997 to 1998. Composts were effective in suppressing disease to levels not significantly different than the fungicide controls, which showed up to 33% disease in 1998 and up to 31% disease in 1999 (P = 0.05). Storage of composts for up to 1 year did not affect their ability to reduce dollar spot severity (P = 0.05). The use of composts as plant disease suppressants is not likely to replace the use of commercial fungicides in dollar spot management. However, multiple applications of compost may reduce incidence and severity of dollar spot to levels at which chemical control may be reduced or eliminated for a significant portion of the season.
Etiology and Host Range of a Closterovirus Associated with Plum Bark Necrosis-Stem Pitting Disease
Authors: Marini Diana B. , Zhang Y.-P. , Rowhani A. , Uyemoto J. K.
Published: May 2007

Diseased plum (Prunus salicina) cv. Black Beaut trees developed stem gumming, severe bark necrosis, and stem pitting symptoms on the woody cylinder of the main trunk and scaffold branches. The sucker shoots of the peach (Prunus persica) cv. Nemaguard understocks exhibited oak-leaf patterns, but lacked the wood or bark markings. Other susceptible hosts included almond (Prunus dulcis), sweet (Prunus avium) and Japanese flowering (Prunus serrulata) cherries, and several plum (Prunus salicina) and prune (Prunus domestica) varieties. A purified preparation containing high molecular size dsRNAs was obtained initially from diseased cherry (P. avium × Prunus pseudocerasus) cv. Colt tissues. Healthy preparations were devoid of similar sized dsRNAs. Reverse transcriptase-polymerase chain reaction (RT-PCR) assays with degenerate oligonucleotide Closterovirus primers, designed from the HSP70 gene, were used to amplify two DNA fragments of 0.67 and 0.56 kbp. The larger cDNA product was cloned, sequenced (AF195501), and compared with other viral sequences. Depending on the number of nucleotides used in the comparisons, identities ranged from 77% for Grapevine leafroll associated virus to 3 to 44% for Little cherry virus-1. Specific primers from the 0.67 kbp cDNA sequence were designed and used in subsequent RT-PCR assays. The associated 0.67 kbp HSP70 amplicon of Plum bark necrosis-stem pitting associated virus was detected in all graft-inoculated Prunus species and varieties except prune (P. domestica var. French Improved).
Species Delimitation and Host Specialization of Ceratocystis laricicola and C. polonica to Larch and Spruce
Authors: Harrington T. C. , Pashenova N. V. , McNew D. L. , Steimel J. , Konstantinov M. Yu.
Published: May 2007

Ceratocystis laricicola and C. polonica are fungal symbionts of bark beetle species of the genus Ips that attack species of Larix and Picea, respectively, across Eurasia. Earlier studies found that these fungal species were morphologically identical, had similar isozymes patterns, and had identical internal transcribed spacer (ITS) sequences of the rDNA operon. We analyzed 27 isolates from Europe, southwestern Siberia (Russia) and Japan, representing the known geographic ranges of the two species. Phylogenetic analysis of the DNA sequences of a portion of the MAT-2 idiomorph showed these species to be distinct, with the Japanese isolates of C. laricicola having a sequence slightly different (5 bp) from those of the Russian and European isolates of C. laricicola. Sexual compatibility tests showed full interfertility among isolates of C. polonica from Europe, Russia and Japan, but isolates of C. polonica were not fully interfertile with isolates of C. laricicola. A Russian and a European isolate of C. laricicola mated with each other but not with the Japanese isolates of C. laricicola. Mature L. sibirica and P. obovata were inoculated with isolates of C. laricicola and C. polonica from Europe, Russia, and Japan, and measurement of lesions in the inner bark/cambium region demonstrated strong host specialization. The data suggest that the two fungal species are very closely related and are distinguished primarily by their physiological specialization to the hosts of their bark beetle vectors.
Distribution of Aspergillus Section Flavi among Field Soils from the Four Agroecological Zones of the Republic of Bénin, West Africa
Authors: Cardwell K. F. , Cotty P. J.
Published: May 2007

Certain members of Aspergillus section Flavi produce carcinogenic and immunotoxic metabo-lites called aflatoxins. These fungi perennate in soils and infect maize grain in the field and in storage. The distribution of Aspergillus section Flavi across the four different agroecologies of Bénin Republic was determined. The four agroecological zones range from humid equatorial tropics in the south to the dry savanna near the Sahara desert in the north. Soil samples collected in 1994 to 1996 from 44 different maize fields in Bénin were assayed over 3 years (88 samples total) for fungi in Aspergillus section Flavi. All soils tested contained A. flavus. Isolates (1,454 total) were collected by dilution plate from the soils and existed in populations ranging from <10 to >200 CFU/g of soil. CFU counts did not differ from year to year or change significantly with cropping systems within a zone, but differed significantly among zones. Incidence of A. flavus strain isolations varied from south to north, with greater number of CFU of L strain isolates in southern latitudes and higher numbers of CFU of S strain isolates found in the north. The L strain isolates occurred in 81 of 88 samples, whereas S strain isolates were in only 41 of 88 soil samples. Of 96 L strain isolates tested, 44% produced aflatoxins. Only B toxins were produced, and toxigenic isolates averaged over 100 μg of aflatoxin B1 per 70 ml of fermentation medium (~1.4 ppm). All S strain isolates produced both B and G aflatoxins, averaging over 557 μg of aflatoxin B1 per 70 ml (8 ppm) and 197 μg of aflatoxin G1 per 70 ml of fermentation me- dium (2.8 ppm). A. parasiticus and A. tamarii were present in less than 10% of the fields and were not associated with any particular agroecological zone.
First Report of Phytophthora cinnamomi on Quercus laurifolia
Authors: Wood A. K. , Tainter F. H.
Published: May 2007

In May 2001, bleeding cankers were observed on several laurel oak (Quercus laurifolia) trees in central Florida. Affected trees had chlorotic leaves, sparse canopies, and little new growth. Multiple cankers were present on the trunk and extended from the soil line up to approximately 5 m. Each canker had a reddish to dark brown or black exudate. From two of the infected trees, tissue samples were taken from beneath the bark around the edge of an actively growing lesion and transferred directly to Phytophthora-selective medium (1), and three soil cores (2 cm in diameter, 20 cm deep) were collected from the base of each tree. A baiting bioassay (with camellia leaf disks and shore juniper and eastern hemlock needles as baits) was used to assay fresh composite soil samples for Phytophthora species (1). P. cinnamomi was recovered from both tissue and soil samples (2). Mycelia were coralloid with abundant hyphal swellings. Sporangia were produced in 1.5% nonsterilized soil extract solution. Sporangia were ovoid to ellipsoid in shape and nonpapillate. Average sporangium size was 72 × 45 μm (length × width). To our knowledge, this is the first report of P. cinnamomi on laurel oak trees.

References: (1) A. J. Ferguson and S. N. Jeffers. Plant Dis. 83:1129, 1999. (2) G. M. Waterhouse. Key to the species of Phytophthora de Bary. Mycol. Pap. 92. CMI. Kew, UK, 1963.
First Report of Rhizoctonia oryzae on Pea
Authors: Paulitz T. C.
Published: May 2007

In May 2001, severe stunting, lateral rot, and brown discoloration of taproots were observed in a field of direct-seed (no-till) pea cv. Columbia southeast of Lewiston, ID. The field had been previously cropped with direct-seeded spring barley. Roots were washed, plated on water agar containing benomyl at 1 μ/ml and chloramphenicol at 100 μg/ml, and incubated at 22°C. Fungal colonies were identified as Rhizoctonia oryzae (teleomorph Waitea circinata Warcup & Talbot) based on hyphal and colony morphology (3) and anastamosis reaction with known tester isolates. Two isolates were grown on autoclaved oat seeds for 3 weeks to produce inoculum for pathogenicity testing. One colonized oat seed was placed below a seed of Pisum sativum ‘Little Marvel’ planted in pasteurized sandy loam soil. There were five pea seeds per 10-cm-diameter pot and three replicate pots per isolate. Both isolates caused severe damping-off and stunting. Both isolates were also tested in nonpasteurized (natural) sandy loam in 4 cm × 20 cm plastic pine seedling tubes. Eight colonized oat seeds were placed in a band 1 cm below a single pea seed planted in each tube. Tubes were watered with metalaxyl (0.1g/liter, technical grade) to inhibit Pythium. Control treatments consisted of soil amended with either autoclaved oat seeds or nothing. Two isolates of R. oryzae were tested with two pea cultivars (B160 and Marjorette), with five replicates per treatment. R. oryzae did not significantly reduce emergence but did cause necrosis and browning of root tips and reduction in lateral root formation. R. oryzae was reisolated from infected roots. To our knowledge, this is the first report of R. oryzae causing disease on a dicot in North America. In Australia, a Waitea sp. was weakly virulent to subterranean clover producing constrictions of the taproot but did not affect plant survival and growth (4). W. circinata also caused damping-off of tobacco seedlings in India (2). In the Pacific Northwest, peas are often grown in rotation with wheat and barley, and R. oryzae can be virulent on these cereal crops (1). This finding may have important implications for disease management in wheat and legumes in crop rotation systems.

References: (1). M. Mazzola et al. Phytopathology 86:354, 1996. (2) C. A. Raju. Tob. Res. 19:92, 1993. (3) B. Sneh et al. Identification of Rhizoctonia Species. The American Phytopathological Society, St. Paul, MN, 1991. (4) D. H. Wong et al. Trans. Br. Mycol. Soc. 85:156, 1985.
Reaction of Rice (Oryza sativa) Cultivars to Penetration and Infection by Curvularia tuberculata and C. oryzae
Authors: de Luna Lilian Z. , Watson Alan K. , Paulitz Timothy C.
Published: May 2007

Isolates of Curvularia species were collected from weedy Cyperaceae species and are being evaluated as possible biocontrol agents of sedge weeds in rice (Oryza sativa). Curvularia species have been reported from rice; thus cultivars of rice were tested to determine rice seedling responses to these potential biocontrol agents. All 13 rice cultivars were resistant to Curvularia tuberculata isolate 93-022, 12 were resistant to C. tuberculata isolate 93-020, and 7 were resistant to C. oryzae isolate 93-061. In the resistant cultivars, lesions on the leaf laminae were small, light to dark brown, with a dry appearance. Spots on the leaf margins and leaf tips were light brown to cream and dry. In the susceptible cultivars, the brown lesions coalesced with necrotic centers. Sporulation was observed in the lesions on susceptible cultivars but not on the resistant cultivars. The histopathology of C. tuberculata and C. oryzae was studied in two resistant rice cultivars, IR 64 (IRRI Acc. no. 66970) and Norin 21 (IRRI Acc. no. 7686), by light microscopy. C. tuberculata exhibited polar germination beginning at 4 h postinoculation (HPI); whereas C. oryzae was characterized by bipolar germination starting at 2 HPI. Simple terminal or intercalary appressoria were initiated at 24 HPI over stomatal apertures, or rarely, on the epidermal cell walls and bulliform cells. No infection cushions were formed. Penetration occurred by the formation of a fine penetration peg beneath the appressorium. A chlorotic reaction was observed in areas beneath and adjacent to the appressoria and germ tubes and in the infected cells. Resistance of IR 64 and Norin 21 to C. tuberculata and C. oryzae infection was mainly expressed after penetration as a slow and restricted mycelial growth and no sporulation. C. tuberculata isolate 93-022 is the preferred isolate for further study as a biological control agent against Cyperus difformis, C. iria, and Fimbristylis miliacea.
Establishment, Distribution, and Pathogenicity of Puccinia striiformis f. sp. tritici in South Africa
Authors: Boshoff W. H. P. , Pretorius Z. A. , van Niekerk B. D.
Published: May 2007

Stripe rust, caused by Puccinia striiformis Westend. f. sp. tritici Eriks., has become an endemic disease of wheat (Triticum aestivum L.) in South Africa since it was first observed near Moorreesburg, Western Cape during August 1996. The main objectives of this study were to monitor the occurrence, spread, and the possible development of new variants of the stripe rust pathogen and the susceptibility of grass species to the pathogen. Results of surveys conducted during 1996 to 1999 revealed that rainfed wheat produced in the Western Cape, Eastern Cape, and the eastern Free State, as well as irrigated wheat produced in KwaZulu-Natal and the Free State, are most likely to be affected by stripe rust epidemics. Pathotype 6E16A- with virulence to Yr2, Yr6, Yr7, Yr8, Yr11, Yr14, Yr17, and Yr19 and pathotype 6E22A- with added virulence to Yr25 were detected. The occurrence of pathotype 6E22A- is currently restricted to KwaZulu-Natal and the Free State. Stripe rust isolates found on Hordeum murinum L. in the Western Cape were identified as pathotype 6E16A-, and both pathotypes 6E16A- and 6E22A- were collected from Bromus catharticus Vahl (= B. unioloides H.B.K.) in the eastern Free Sate. Urediospores from infections similar to stripe rust found on the grass species Dactylis glomerata L. (Eastern Cape), Poa pratensis L. (= P. bidentata Stapf; Western Cape), and P. annua and P. triviales L. (eastern Free State) failed to infect wheat cv. Morocco seedlings in the glasshouse. The possible role of grasses in the over-summering of the stripe rust pathogen has not yet been established. Stripe rust infections, however, have been found on summer-sown wheat in the south Western Cape during 1998, volunteer wheat growing in the summer and autumn months in the eastern Free State from 1998 to 2000, and on summer-sown wheat in Lesotho.
Effects of Selected Marigold Varieties on Root-knot Nematodes and Tomato and Melon Yields
Authors: Ploeg Antoon T.
Published: May 2007

Field experiments were conducted at two sites in California to evaluate the effects of marigold genotypes Tagetes patula var. Single Gold and Tagetes hybrid var. Polynema on Meloidogyne incognita infestation, root-galling, and yields of tomato grown immediately after marigold. Marigold cultivars were compared with a fallow control and with methyl iodide fumigation of soil prior to cultivation of M. incognita-susceptible and M. incognita-resistant tomato. Tomato yields after marigold were ca. 50% higher than after fallow. Marigold Single Gold consistently reduced nematode infestation and galling of tomato roots. Results were not significantly different between methyl iodide fumigation or marigold Single Gold at one site, but methyl iodide outperformed both marigold varieties at the other site. At one site, where melon var. Durango was grown during spring and summer of the year following cultivation of marigolds Single Gold and Polynema, melon yield increases of 95 and 45%, respectively, were still obtained.