bluuebunny/crossref_metadata_2025 huggingface dataset:
Resistance of Botrytis cinerea Isolates from Vegetable Crops to Anilinopyrimidine, Phenylpyrrole, Hydroxyanilide, Benzimidazole, and Dicarboximide Fungicides
Authors: Myresiotis C. K. , Karaoglanidis G. S. , Tzavella-Klonari K.
Published: May 2007

During February 2005, 55 single-spore isolates of Botrytis cinerea were collected at the end of the season from vegetable crops grown in 18 greenhouses on the island of Crete, Greece. They were tested for sensitivity to the anilinopyrimidine fungicides pyrimethanil and cyprodinil, the hydroxyanilide fungicide fenhexamid, the phenylpyrrole fungicide fludioxonil, the dicarboximide fungicide iprodione, and the benzimidazole fungicide carbendazim. Results of the study showed the existence of benzimidazole- and dicarboximide-resistant strains at frequencies of 61.8 and 18%, respectively. Moreover, for first time, the development of resistance to anilinopyrimidine fungicides by B. cinerea was detected in greenhouse vegetable crops on the island of Crete. High resistance frequencies of 49.1 and 57.4% were observed for pyrimethanil and cyprodinil, respectively. In addition, one isolate was found to be resistant to the hydroxyanilide fungicide fenhexamid, while no strains resistant to the phenylpyrrole fungicide were detected. Among the 55 isolates tested, 13 were resistant only to carbendazim, 6 were resistant only to anilinopyrimidines, 3 were resistant to both benzimidazoles and dicarboximides, 17 were resistant to both benzimidazoles and anilinopyrimidines, 6 were resistant to both dicarboximides and anilinopyrimidines, 1 was simultaneously resistant to benzimidazoles, dicarboximides, and anilinopyrimidines, 1 was resistant to both anilinopyrimidines and hydroxyanilides, and 8 were sensitive to all fungicides tested. A strong cross-resistance relationship was found between the two anilinopyrimidine fungicides tested when log transformed EC50 values of the isolates were subjected to a linear regression analysis (r = 0.71). Despite the detection of several phenotypes with simultaneous resistance to chemically unrelated active ingredients, in none of the remaining possible fungicide pairs was there observed any kind of cross-resistance relationship.
Early Detection of Leifsonia xyli subsp. xyli in Sugarcane Leaves by Real-Time Polymerase Chain Reaction
Authors: Grisham M. P. , Pan Y.-B. , Richard E. P.
Published: May 2007

A real-time, polymerase chain reaction (PCR) assay was developed for detecting Leifsonia xyli subsp. xyli in sugarcane leaf tissue. Real-time PCR assays were conducted on the youngest, fully expanded leaf of three cultivars collected bi-weekly from field nurseries between 11 April and 19 July 2005. L. xyli subsp. xyli infection was detected in leaves collected at all sampling dates, including those from 1-month-old plants on 11 April. Assays conducted on older, more rapidly growing plants (28 July and 21 October 2005) indicated that leaf position affects assay efficiency. Conventional PCR was less efficient than real-time PCR for detecting L. xyli subsp. xyli in leaf tissue. Real-time PCR was used to rank cultivars for susceptibility to L. xyli subsp. xyli infection based on the relative titer of L. xyli subsp. xyli in leaves of inoculated, 3- and 4-month-old greenhouse-grown plants. The ranking of cultivars by real-time PCR was in close agreement with the ranking determined by tissue-blot enzyme immunoassay performed on tissue from 7- to 9-month-old stalks.
Susceptibility of Some Eastern Forest Species to Phytophthora ramorum
Authors: Tooley Paul W. , Kyde Kerrie L.
Published: May 2007

We tested some common Eastern forest species for their reaction to stem and leaf inoculation with Phytophthora ramorum, the pathogen that causes sudden oak death. Stem lesions were produced on inoculated seedlings of 12 Eastern forest species following 72 to 76 days of incubation in a containment greenhouse cubicle at 20°C. Chestnut oak (Quercus prinus) and white oak (Q. alba) were followed by northern red oak (Q. rubra) in susceptibility to stem inoculation. Sugar maple (Acer saccharum) and black walnut (Juglans nigra) were more resistant to stem inoculation than most of the oak species tested. P. ramorum was isolated on selective medium at distances of up to 8 mm from stem lesion margins. Foliar lesions were observed within 7 days when seedlings were inoculated with 5,000 sporangia/ml followed by incubation at 20°C in a dew chamber. Chestnut oak was followed by tanoak (Lithocarpus densiflorus) and coast live oak (Q. agrifolia) in susceptibility to P. ramorum by foliar inoculation. Chestnut oak, an ecologically important species in parts of the Eastern United States, emerged as the most susceptible host tested in both stem and foliar inoculations. The results indicate that, under controlled conditions, P. ramorum is able to infect some important Eastern forest species and cause lesions on stems and foliage. It remains to be determined whether infection of these species by P. ramorum would occur under natural conditions.
Variation for Resistance to Verticillium Wilt in Lettuce (Lactuca sativaL.)
Authors: Hayes Ryan J. , Vallad Gary E. , Qin Qing-Ming , Grube Rebecca C. , Subbarao Krishna V.
Published: May 2007

Host resistance offers the most cost-effective method of Verticillium wilt control in lettuce (Lactuca sativa). In 2004 and 2005, 107 and 22 lettuce cultivars, respectively, were screened for resistance in a field infested with Verticillium dahliae, and disease progress on resistant and susceptible cultivars was determined. Greenhouse experiments were conducted to evaluate 16 cultivars for resistance to a race 1 and a race 2 isolate. Significant differences for resistance were observed within cultivated lettuce. In susceptible cultivars, disease levels increased through the season, whereas disease in resistant cultivars remained constant. Resistance in greenhouse tests was dependant upon the race used. Seven cultivars were resistant to race 1, whereas all were susceptible to race 2. Cultivar reactions to race 1 in greenhouse and field experiments were correlated, indicating the utility of greenhouse evaluations. The identification of resistance in diverse lettuce types is beneficial to the breeding process. However, because of the existence of resistance-breaking race 2 isolates, this resistance may not be durable. Alternatively, targeted releases of race-1-resistant cultivars to fields with only race 1 pathogen genotypes may extend the life of these cultivars.
A Genetic Shift in the Virus Strains that Cause Mosaic in Louisiana Sugarcane
Authors: Grisham M. P. , Pan Y.-B.
Published: May 2007

Leaf samples from 693 sugarcane plants showing mosaic symptoms were collected in 2001, 2002, and 2003 at 12 locations within the Louisiana sugarcane industry. Virus isolates associated with the diseased plants were identified using reverse-transcriptase polymerase chain reaction (RT-PCR) to distinguish between Sugarcane mosaic virus (SCMV) and Sorghum mosaic virus (SrMV). No SCMV strain was associated with any diseased plant collected during the survey. RT-PCR-based restriction fragment length polymorphism (RFLP) analysis showed that SrMV strains I, H, and M were associated with 67, 10, and 2% of the plants with mosaic symptoms, respectively. In previous surveys conducted between 1978 and 1995, over 90% of the plants sampled were infected with SrMV strain H. The remaining plants mostly were infected with SrMV strain I, except for an occasional sample with SrMV strain M. RT-PCR showed that approximately 13% of the samples collected between 2001 and 2003 were infected with SrMV, but the RFLP banding pattern did not match any described strain. Twelve plants were co-infected by two SrMV strains and two plants by three SrMV strains. No RT-PCR product was produced by either the SCMV- or the SrMV-specific RT-PCR primer set for 8% of the plants showing mosaic symptoms, suggesting that another virus may cause sugarcane mosaic in Louisiana.
First Report of Onion yellow dwarf virus, Leek yellow stripe virus, and Garlic common latent virus in Garlic in Oregon
Authors: Gieck S. L. , Pappu H. R. , Hamm P. B. , David N. L.
Published: May 2007

A general mosaic and yellowing of leaves of three cultivars of garlic (Allium sativum L., Late, Early, and Germinador) were observed in two seed-production fields in Morrow County, OR in June 2005. Approximately 50% of plants within the 50-ha fields were symptomatic. With recent findings of Onion yellow dwarf virus (OYDV), Leek yellow stripe virus (LYSV), and Garlic common latent virus (GCLV) in Washington (2), 45 composite samples of 10 leaves each from symptomatic (mosaic and yellowing) and nonsymptomatic plants were analyzed with a GCLV-specific antiserum (Agdia Inc., Elkhart, IN). All samples of ‘Germinador’ were infected regardless of symptoms, whereas 6.7% of all ‘Late’ and ‘Early’ samples were positive. GCLV infection was verified by reverse transcription (RT)-PCR using primers specific to the coat protein gene of GCLV followed by cloning and sequencing of the cloned amplicon. To determine the presence of a potyvirus, all composite samples were also tested with a general potyvirus antiserum (Agdia) and all samples from symptomatic plants were found to be positive. Representative positive samples from each cultivar were then tested by RT-PCR using degenerate, potyvirus group specific primers (3), and an amplicon of the expected size was obtained. To confirm which potyvirus was present, amplicons were cloned and sequenced, and sequence comparisons indicated that the representative samples were infected with OYDV. All symptomatic samples from the three cultivars were positive for OYDV when tested by RT-PCR using primers specific to its coat protein gene (1). Additionally, 53.3 and 6.7% of ‘Early’ and ‘Late’ samples, respectively, were also positive when tested with LYSV-specific primers (4). LYSV infection was further verified through cloning and sequencing of the cloned amplicon. Because this garlic is grown for seed, studies are being initiated to determine if current season spread occurs and yields are reduced. To our knowledge, this is the first report of OYDV, LYSV, and GCLV in garlic in Oregon.

References: (1) P. Lunello et al. J. Virol. Methods 118:15, 2004. (2) H. R. Pappu et al. Plant Dis. 89:205, 2005. (3) S. S. Pappu et al. J. Virol. Methods 41:9, 1993. (4) T. Tsuneyoshi et al. Phytopathology. 86:253, 1996.
First Report of White Mold Caused by Sclerotinia sclerotiorum on Iberis sempervirens in Italy
Authors: Garibaldi A. , Minuto A. , Gullino M. L.
Published: May 2007

Iberis sempervirens (candytuft) is an ornamental plant that thrives in cool conditions, and its growth as a potted plant has been increasing in Liguria (northern Italy). In the spring of 2004, extensive chlorosis was observed on 10-month-old potted plants of I. sempervirens grown in a plastichouse on a commercial farm near Albenga in northern Italy. Initial symptoms included stem necrosis at the soil level and darkening of leaves. As stem and foliar necrosis progressed, infected plants wilted and died. Wilt occurred within a few days on young plants, characterized by the presence of soft, watery tissues, particularly on affected leaves. Symptomatic plants were found on many farms, with an average disease incidence of 5 to 10%. Necrotic tissues became covered with a whitish mycelium that produced dark sclerotia. The diseased stem tissue was surface sterilized for 1 min in 1% NaOCl and plated on potato dextrose agar (PDA) amended with 100 ppm of streptomycin sulfate. Sclerotinia sclerotiorum (Lib.) de Bary (1) was consistently recovered from infected stem pieces. Sclerotia observed on infected plants measured 1.4 to 3.2 × 2.1 to 4.1 mm (average 2.1 to 2.7 mm). Sclerotia produced on PDA measured 1.2 to 4.2 × 1.4 to 6.1 mm (average 2.5 to 3.1 mm). Pathogenicity of three isolates obtained from infected plants and used in a mixture was confirmed by inoculating 10 single-potted 120-day-old plants grown in 18-cm diameter pots maintained outside under shade. Inoculum that consisted of 1 cm2 of mycelium excised from a 10-day-old PDA culture plate of each isolate was placed on the soil surface around the base of each plant. Ten noninoculated plants served as control. The inoculation trial was repeated once. All plants were kept at temperatures ranging between 8 and 17°C (average 12.5°C) and watered as needed. All inoculated plants developed symptoms of leaf yellowing within 18 days, soon followed by the appearance of white mycelium and sclerotia, and then eventual wilt. Control plants remained symptomless. S. sclerotiorum was reisolated from the stems of inoculated plants. S. sclerotiorum has been previously reported only on I. umbellata (2). To our knowledge, this is the first report of white mold on I. sempervirens in Italy as well as worldwide. The economic importance of this disease can be considered low at the moment in the case of field-grown plants.

References: (1) N. F. Buchwald. Den. Kgl. Veterin.er-og Landbohojskoles Aarsskrift 75, 1949. (2) J. M. Waterston. Report of the Plant Pathologist, 1946. Dep. Agric. Bermuda, 1947.
First Report of Yucca Phyllody Associated with 16SrI-A Phytoplasmas in Texas
Authors: Lee I.-M. , Bottner K. D. , Black M. C.
Published: May 2007

Buckley's yucca (Yucca constricta Buckl.) is a native flowering perennial plant widely distributed in Texas and northeast Mexico. It is also grown as an ornamental plant in its native range as well as in other dry regions in the United States and Mexico. In 2006, during an extended drought, Buckley's yucca plants sporadically exhibited phyllody and abnormal bud proliferation on the inflorescence in Uvalde County in southwestern Texas. Symptoms resembled those caused by phytoplasmal infection. Samples from four symptomatic and two asymptomatic yucca plants were collected. Total nucleic acid was extracted from abnormal bud tissue. To assess the etiological aspect of the disease nested PCR using phytoplasma specific primer pair P1/16S-SR or P1/P7 followed by R16F2n/R16R2n was employed for the detection of putative phytoplasmas (2). An amplicon of approximately 1.2 kb was amplified from all four symptomatic yucca plants but not from asymptomatic plants. Restriction fragment length polymorphism (RFLP) patterns of 16S rDNA digested singly with AluI, KpnI, HpaII, MseI, HhaI, and RsaI endonucleases indicated that affected yucca plants were infected by a phytoplasma belonging to aster yellows group 16SrI (‘Candidatus Phytoplasma asteris’), subgroup 16SrI-A (1). Nucleotide sequence analysis of cloned 16S rDNA (GenBank Accession No. EF190067) confirmed the results on the basis of RFLP analyses. Yucca phyllody has not been reported elsewhere. This disease appears to be newly emerging in Texas with only a few affected plants. To our knowledge, this is the first report of 16SrI-A phytoplasma infecting a Yucca sp.

References: (1) I.-M. Lee et al. Int. J. Syst. Bacteriol. 48:1153, 1998. (2) I.-M. Lee et al. Int. J. Syst. Evol. Microbiol. 54:337, 2004.
First Report of Gummy Stem Blight Caused by Didymella bryoniae on Grafted Watermelon in Tunisia
Authors: Boughalleb N. , El Mahjoub M. , Abad-Campos P. , Pérez-Sierra A. , García-Jiménez J. , Armengol J.
Published: May 2007

During the summer of 2006, severe losses were observed in grafted watermelons in the Testour Region in northern Tunisia. Disease symptoms included stem cankers and necrosis and rot of the grafting area that extended a few centimeters along watermelon vines with the production of a brown gummy exudation. Lesions were not observed on leaves or nongrafted plants. Affected plants wilted and eventually died. The presence of small pseudothecia as black specks was observed embedded in the cankers. Isolations from the stems and crown of symptomatic plants onto potato dextrose agar (PDA) supplemented with 0.5 mg/ml of streptomycin sulfate consistently yielded cultures of a fungal agent. These isolates were transferred to PDA and V8 juice agar and incubated at 23°C for 1 month with a 12-h photoperiod. On PDA, they produced numerous pycnidia with hyaline, cylindrical, one-septate conidia, with mean dimensions of 6.7 × 2.5 μm. On V8 juice agar, they produced sparse ostiolate pseudothecia with bitunicate asci and hyaline, oval, one-septate ascospores, with mean dimensions of 13.7 × 5.1 μm. On the basis of these characters, the isolates were identified as Didymella bryoniae (anamorph Phoma cucurbitacearum) (1,2). To further confirm this identification, the complete internal transcribed spacer regions 1 and 2, including the 5.8S ribosomal DNA, of isolates Di-3 and Di-4 were sequenced (GenBank Accession Nos. EF107641 and EF 107642). These sequences were identical to sequences in GenBank from isolates of D. bryoniae (Accession Nos. AF297228 and AF495850). Pathogenicity tests were conducted on watermelon seedlings cv. Giza and Cucurbita hybrid rootstock seedlings cv. Strong Toza using two isolates, Di-3 and Di-4. Seedlings were inoculated at the two- to three-leaf stage. A 5-mm diameter agar disc, cut from the margin of an 8-day-old culture growing on PDA, was inserted in a basal stem wound made with a sterile scalpel at 2 cm above ground level and sealed with Parafilm. Controls were inoculated with sterile PDA discs. There were 10 replicates for each isolate and host with an equal number of uninoculated plants. Seedlings were maintained in a greenhouse at 23 to 25°C. Within 10 to 15 days after inoculation, symptoms developed as water-soaked lesions followed by necrosis and finally wilting. The fungus was reisolated from the stems of all inoculated plants, completing Koch's postulates. To our knowledge, this is the first report of D. bryoniae in Tunisia.

References: (1) A. P. Keinath et al. Phytopathology 85:364, 1995. (2) E. Punithalingam and P. Holliday. No. 332 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1972.
First Report of Chrysanthemum stem necrosis virus on Chrysanthemums in Japan
Authors: Matsuura S. , Kubota K. , Okuda M.
Published: May 2007

The chrysanthemum (Dendranthema grandiflorum), whose planted area comprises more than 6,000 ha in Japan, is one of the most important ornamental cut flower crops. In August 2006, necrotic streaks on stems, chlorotic and necrotic spots and rings on leaves, and leaf distortions were observed on chrysanthemum cvs. Jimba and Seinotama, with a disease incidence of more than 70% (approximately 30,000 plants), which represents approximately 1,000 m2 of greenhouses of one grower in Hiroshima Prefecture, western Japan. Symptoms were similar to those caused by Tomato spotted wilt virus (TSWV) (genus Tospovirus, family Bunyaviridae). Frankliniella occidentalis was the major thrips species observed on symptomatic plants, followed by F. intonsa. Tospovirus-like spherical particles that were 80 to 100 nm in diameter were found in the infected leaves. After mechanical inoculation, a single lesion isolate reproduced the original symptoms observed in nature on healthy chrysanthemum plants (cv. Jimba). As determined by mechanical inoculation, host range and symptomatology of the isolate were similar to those described previously for Chrysanthemum stem necrosis virus (CSNV), including necrotic spots on Petunia hybrida (1). The isolate caused stunting, severe necrotic lesions on stems, necrotic spots, rings, and vein necrosis on systemically infected leaves of Lycopersicon esculentum (cv. House-momotaro). This virus reacted strongly with CSNV antiserum (DSMZ, Braunschweig, Germany) by indirect dot immuno-binding assay, and cross-reacted weakly with a monoclonal antibody to N protein of TSWV (3) using double-antibody sandwich-ELISA. Reverse transcription (RT)-PCR was conducted to verify virus infection. No amplification was observed from extracts of symptomatic plants (n = 10) by multiplex RT-PCR using TSWV and Impatiens necrotic spot virus specific primer sets (4), indicating that the diseased chrysanthemums were not doubly infected with these viruses. However, a DNA fragment of approximately 450 bp was amplified in samples by RT-PCR using tospovirus universal primers, BR60/65 (2). The nucleotide sequence of the amplified fragment had 98.1% identity with the corresponding region of the CSNV nucleocapsid protein gene (GenBank Accession No. AF067068). The above results indicate that the virus associated with a stem necrosis disease of chrysanthemums in Hiroshima is an isolate of CSNV. To our knowledge, this is the first report of CSNV in Japan.

References: (1) I. C. Bezerra et al. Phytopathology 89:823, 1999. (2) M. Eiras et al. Fitopatol. Bras. 26:170, 2001. (3) S. Tsuda et al. Ann. Phytopathol. Soc. Jpn. 60:216, 1994. (4) H. Uga and S. Tsuda. Phytopathology 95:166, 2005.
First Report of Arceuthobium aureum subsp. aureum in Mexico
Authors: Mathiasen R. , Howell B. , Garnett G.
Published: May 2007

The golden dwarf mistletoe (Arceuthobium aureum Hawksw. & Wiens subsp. aureum, Viscaceae) parasitizes several pines (Pinus spp., Pinaceae) in central Guatemala (1). In September 2006, we observed golden dwarf mistletoe parasitizing Pinus maximinoi H.E. Moore in southern Chiapas, Mexico; 1 km west of El Rosario along Mexico Route 211 (15°19′23″N, 92°17′45″W, elevation 1,720m). Golden dwarf mistletoe can be distinguished from the closely related Peterson's dwarf mistletoe (A. aureum Hawksw. & Wiens subsp. petersonii Hawksw. & Wiens) by its smaller shoots, occurrence below 2,200 m in elevation, and flowering period (1). The shoots of the dwarf mistletoe at the El Rosario location were less than 20 cm high and male plants were not flowering. Male plants of Peterson's dwarf mistletoe observed at the type locality and other locations in Chiapas during September were in full flower. Although only 29 trees were infected at this location, infection was severe on 11 trees, but no mortality associated with dwarf mistletoe infection was observed. Mistletoe infection did not induce the formation of witches'-brooms near El Rosario, but infection by golden dwarf mistletoe on P. maximinoi does induce witches'-brooms on older trees in Guatemala (2). The golden dwarf mistletoe population near El Rosario is approximately 150 km west of the nearest known population of this species in Guatemala (1). To our knowledge, this is the first report of golden dwarf mistletoe in Mexico. Specimens of golden dwarf mistletoe from Chiapas, Mexico were deposited at the Deaver Herbarium, Northern Arizona University, Flagstaff (Accession No. 83122).

References: (1) F. Hawksworth and D. Wiens. Dwarf Mistletoes: Biology, Systematics, and Pathology. USDA For. Serv. Agric. Handb. 709, 1996. 2) R. Mathiasen et al. Madrono 23:122, 2004.
Comparative Genetic Analysis of Magnaporthe oryzae Isolates Causing Gray Leaf Spot of Perennial Ryegrass Turf in the United States and Japan
Authors: Tosa Y. , Uddin W. , Viji G. , Kang S. , Mayama S.
Published: May 2007

Gray leaf spot caused by Magnaporthe oryzae is a serious disease of perennial ryegrass (Lolium perenne) turf in golf course fairways in the United States and Japan. Genetic relationships among M. oryzae isolates from perennial ryegrass (prg) isolates within and between the two countries were examined using the repetitive DNA elements MGR586, Pot2, and MAGGY as DNA fingerprinting probes. In all, 82 isolates of M. oryzae, including 57 prg isolates from the United States collected from 1995 to 2001, 1 annual ryegrass (Lolium multiflorum) isolate from the United States collected in 1972, and 24 prg isolates from Japan collected from 1996 to 1999 were analyzed in this study. Hybridization with the MGR586 probe resulted in approximately 30 DNA fragments in 75 isolates (designated major MGR586 group) and less than 15 fragments in the remaining 7 isolates (designated minor MGR586 group). Both groups were represented among the 24 isolates from Japan. All isolates from the United States, with the exception of one isolate from Maryland, belonged to the major MGR586 group. Some isolates from Japan exhibited MGR586 fingerprints that were identical to several isolates collected in Pennsylvania. Similarly, fingerprinting analysis with the Pot2 probe also indicated the presence of two distinct groups: isolates in the major MGR586 group showed fingerprinting profiles comprising 20 to 25 bands, whereas the isolates in the minor MGR586 group had less than 10 fragments. When MAGGY was used as a probe, two distinct fingerprint types, one exhibiting more than 30 hybridizing bands (type I) and the other with only 2 to 4 bands (type II), were identified. Although isolates of both types were present in the major MGR586 group, only the type II isolates were identified in the minor MGR586 group. The parsimony tree obtained from combined MGR586 and Pot2 data showed that 71 of the 82 isolates belonged to a single lineage, 5 isolates formed four different lineages, and the remaining 6 (from Japan) formed a separate lineage. This study indicates that the predominant groups of M. oryzae associated with the recent outbreaks of gray leaf spot in Japan and the United States belong to the same genetic lineage.
Comparison of Molecular Procedures for Detection and Identification of Guignardia citricarpa and G. mangiferae
Authors: Peres N. A. , Harakava R. , Carroll G. C. , Adaskaveg J. E. , Timmer L. W.
Published: May 2007

Citrus black spot, caused by Guignardia citricarpa, is a serious fruit spot disease and is widely distributed in Asia, southern Africa, and South America, but does not occur in North America or the Mediterranean region. A nonpathogenic species, G. mangiferae, is cosmopolitan with a wide host range and can colonize citrus fruit and leaves saprophytically. Detection and identification of Guignardia spp. on citrus fruit is necessary for epidemiological, management, and regulatory purposes. In this study, we compared published and unpublished polymerase chain reaction primer sets for their specificity and sensitivity in the detection and differentiation of the two Guignardia spp. All primers evaluated successfully identified the two species using purified DNA from fungal cultures or mycelia as source materials. However, some primer sets were not highly effective in detecting G. citricarpa when DNA was extracted directly from single characteristic black spot lesions on fruit. Thus, new primer pairs for both species were designed from the internal transcribed spacer region that were highly sensitive and specific for detection of G. citricarpa using DNA recovered from single lesions on fruit by a rapid DNA extraction procedure.
Distribution of Phoma sclerotioides on Alfalfa and Winter Wheat Crops in the North Central United States
Authors: Larsen J. E. , Hollingsworth C. R. , Flor J. , Dornbusch M. R. , Simpson N. L. , Samac D. A.
Published: May 2007

Brown root rot of alfalfa (Medicago sativa), caused by Phoma sclerotioides, has been reported in several states in the northern United States and in western Canada. A survey was conducted to determine the distribution of the fungus in Minnesota and Wisconsin. Isolates of the pathogen were recovered from roots of alfalfa, winter wheat, and perennial ryegrass plants. The internal transcribed spacer (ITS) 1, 5.8S, and ITS2 of the rDNA of the isolates from alfalfa and wheat were identical and matched the sequences of a P. sclerotioides isolate from Wyoming. The fungus was found to be widespread in both states and was detected in roots of alfalfa plants from 17 counties in Minnesota and 14 counties in Wisconsin using polymerase chain reaction (PCR)-based assays. A real-time PCR assay was developed that increased sensitivity of detecting the pathogen from plant tissues and soil. The isolates from alfalfa caused disease on inoculated winter wheat plants. Although the fungus was previously found associated with roots of diseased cereal and turfgrass plants, this is the first demonstration of pathogenicity of P. sclerotioides on wheat.
Rose Dieback Caused by Trichothecium roseum in Argentina
Authors: Wright E. R. , Pizzingrilli P. , Caligaris M. V. , Cabral D.
Published: May 2007

Rose (Rosa sp.) is one of the most important ornamentals in Argentina. Since 2002, a severe disease has been observed on crops cultivated for cut flowers and garden plants in Escobar, San Pedro, Río Negro, and the surrounding area of Buenos Aires and La Plata. Symptoms consisted of a stem dieback progressing to plant death. In some cases, stem cankers were observed on the dieback limits. Mean incidence of stem dieback was 8% regardless of location. The disease was associated with pruning or harvest wounds. The objective of this study was to identify the causal agent of the described symptoms. Small pieces of diseased tissues from cvs. Rafaela, Merlise, Confeti, Mini rosal, Exótica, Macarena, and Peckowo were surfaced sterilized with a 2-min immersion in 0.2% NaOCl, washed with sterile distilled water, the tissue blotted dry, placed on 2% potato dextrose agar (PDA), and incubated at 22°C. Pure salmon-colored fungal colonies developed within 72 h. Hyaline, two-celled (the upper cell slightly larger), ovoid to ellipsoid conidia formed in chains at the apex of simple, long, slender, septate conidiophores. These characteristics are consistent with the description of Trichothecium roseum (Pers.) Link ex Gray (1) The pathogenicity tests were carried out on 10 plants of cv. Rafaela and 10 plants of cv. Mini Rosal using a conidial suspension (2.4 × 105 spores/ml). All plants were pruned just before inoculation. Another 10 pruned plants (five from each cultivar) were sprayed with sterile water and served as controls. Inoculated and noninoculated plants were placed in a climatic chamber at 20°C and covered with polyethylene bags for 3 days to achieve a humid environment. Stem dieback was evident 7 days after inoculation on both cultivars and cankers appeared in 14 days. A dense, white mold that turned salmon-pink covered all the stems within 25 days. Inoculated plants died after 40 days. Symptoms did not develop on the control plants. The pathogen was recovered from inoculated stems, thus fulfilling Koch's postulates. To our knowledge, this is the first report of T. roseum causing a disease on rose in Argentina.

Reference: (1) K. H. Domsch et al. Compendium of Soil Fungi. Academic Press. London, 1980.
First Report of Powdery Mildew Caused by Golovinomyces orontii (Erysiphe orontii) on Petunia × hybrida in Italy
Authors: Garibaldi A. , Bertetti D. , Gullino M. L.
Published: May 2007

Petunia × hybrida (Solanaceae) includes several hybrids that are grown as ornamental plants and are very much appreciated for their long-lasting flowering period. Among those, the variety pendula is often selected because of its hanging growth habit that is favorable for balcony decoration. During the summer of 2005, severe outbreaks of a previously unknown powdery mildew were observed on all petunia plants in several gardens near Biella and Torino (northern Italy). Both surfaces of the leaves of affected plants were covered with white, dense mycelia and conidia. As the disease progressed, infected leaves turned yellow and died. Mycelia also were observed on stems and flowers. Conidia were hyaline, ellipsoid, borne in short chains (with a maximum of four conidia per chain), and measured 27 to 36 × 17 to 21 μm (average 31 × 19 μm). Conidiophores, 130 to 154 μm (average 140 μm) long, showed the foot cell (measuring 42 to 65 × 10 to 12 μm, average 52 × 11 μm) followed by three shorter cells measuring 27 to 30 × 13 to 17 μm (average 29 to 14 μm). Fibrosin bodies were absent. Chasmothecia were not observed in the collected samples. The internal transcribed spacer (ITS) region of rDNA was amplified using primers ITS4/ITS6 (3) and sequenced. BLASTn analysis (1) of the 588 bp obtained showed an E-value of 0.0 with Golovinomyces orontii (Erysiphe orontii) (2). The nucleotide sequence has been assigned GenBank Accession No. DQ 987491. Inoculations were made by gently pressing diseased leaves onto leaves of five healthy Petunia × hybrida var. pendula plants, belonging to cv. Surfinia. Five noninoculated plants served as controls. Inoculated and noninoculated plants were maintained in a greenhouse at temperatures between 14 and 30°C. After 10 days, typical powdery mildew symptoms developed on inoculated plants. Noninoculated plants did not show symptoms. The pathogenicity test was carried out twice. To our knowledge, this is the first report of the presence of powdery mildew on P. × hybrida caused by G. orontii in Italy. A powdery mildew of P. × hybrida reported in 1966 in Romania has been attributed to E. cichoracearum (4), while Braun (2) reported P. × hybrida as a possible host of E. orontii. Specimens of this disease are available at AGROINNOVA Collection, University of Torino, Italy.

References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) U. Braun. A Monograph of the Erysiphaceae (Powdery Mildews). Cramer, Berlin, GDR, 1987. (3) D. E. L. Cooke and J. M. Duncan. Mycol. Res. 101:667, 1997. (4) E. Eliade. Reprium nov. Spec. Regni veg.73:43, 1966.
First Report of Pelargonium zonate spot virus from Tomato in the United States
Authors: Liu H.-Y. , Sears J. L.
Published: May 2007

Pelargonium zonate spot virus (PZSV) was first isolated from tomato in southern Italy in 1982 (1) and later was also reported from Spain (3) and France (2). Infected tomato plants showed stunting, malformation, yellow rings and line patterns on the leaves, and concentric chlorotic ringspots on the stems. In June of 2006, more than 100 tomato (Lycopersicon esculentum Mill.) plants exhibiting symptoms similar to PZSV were observed in seven acres of tomato fields in Yolo County, California. The causal agent was mechanically transmitted to several indicator species. Symptoms on infected plants included local lesions on Beta macrocarpa, Chenopodium amaranticolor, C. capitatum, C. quinoa, Cucumis melo, Cucurbita pepo, and Tetragonia expansa, and systemic infection on Capsicum annuum, Chenopodium murale, L. esculentum, Nicotiana benthamiana, N. clevelandii, N. glutinosa, N. tabacum, Physalis floridana, and P. wrightii. Two field-infected tomato plants and one each of the mechanically inoculated host plant were positive with double-antibody sandwich (DAS)-ELISA using a commercial PZSV IdentiKit (Neogen Europe Ltd., Ayr, Scotland, UK). Partially purified virions stained with 2% uranyl acetate contained spherical to ovate particles. The particle diameters ranged between 25 and 35 nm. Published sequences of PZSV (GenBank Accession Nos. NC_003649 for RNA1, NC_003650 for RNA2, and NC_003651 for RNA3) were used to design three sets of primer pairs specific for PZSV RNA1 (R1-F: 5′ TGGCTGGCTTTTTCCGAACG 3′ and R1-R: 5′ CCTAATCTGTTGGTCCGAACTGTC 3′), RNA2 (R2-F: 5′ GCGTGCGTATCATCAGAAATGG 3′ and R2-R: 5′ ATCGGGAGCAG AGAAACACCTTCC 3′), and RNA3 (R3-F: 5′ CTCACCAACTGAAT GCTCTGGAC 3′ and R3-R: 5′ TGGATGCGTCTTTCCGAACC 3′) for reverse transcription (RT)-PCR tests. Total nucleic acids were extracted from field-infected tomato plants and partially purified virions for RT-PCR. RT-PCR gave DNA amplicons of the expected sizes. The DNA amplicons were gel purified and sequenced. The sequenced amplicons had 92, 94, and 96% nt sequence identity to PZSV RNA1, RNA2, and RNA3, respectively. The symptomatology, serology, particle morphology, and nucleotide sequences confirm the presence of PZSV in a tomato field in California. To our knowledge, this is the first report of the occurrence of PZSV in the United States.

References: (1) D. Gallitelli. Ann. Appl. Biol. 100:457, 1982. (2) K. Gebre-Selassie et al. Plant Dis. 86:1052, 2002. (3) M. Luis-Arteaga et al. Plant Dis. 84:807, 2000.
A Polish Isolate of Zucchini yellow mosaic virus from Zucchini is Distinct from Other European Isolates
Authors: Pospieszny H. , Hasiów B. , Borodynko N.
Published: May 2007

Zucchini yellow mosaic virus (ZYMV) is a member of the Potyvirus genus in the Potyviridae family, the largest group of plant viruses. Different isolates of this virus have been found in infected cucurbits throughout the world, including localities in Europe, America, Australia, and Asia. In August 2005, mosaic and yellowing of leaves, as well as yellow spots on green fruits, were observed on zucchini (Cucurbita pepo cv. giromontiina) growing in commercial fields in the Kujawsko-Pomorskie Region of Poland. Flexuous virus particles (~750 nm long), typical of potyviruses, were observed in leaf-dip preparations from symptomatic zucchini plants. The virus in the sap from symptomatic plants was mechanically transmitted and systemic infections were produced on Citrullus lanatus, Cucumis melo, Cucumis sativus, C. pepo cvs. giromontiina and patissoniana, C. maxima, and Nicotiana benthamiana. Severe symptoms such as severe malformation of leaves and stunting of plants were observed on zucchini plants (cv. giromontiina) infected mechanically with the virus and grown in the greenhouse. Double-antibody sandwich (DAS)-ELISA using an anti-ZYMV polyclonal antiserum (AS-0234; DSMZ, Braunschweig, Germany) identified the presence of ZYMV in mechanically infected C. pepo cv. giromontiina and N. benthamiana plants. Subsequently, a reverse transcription (RT)-PCR using a universal primer, Sprimer, designed from the consensus sequences that code for the conserved sequence GNNSGQP in the NIb region of Potyviridae family members and the M4 primer was performed (1). The 1740-bp PCR fragments were cloned into the pGEM-T vector (Promega, Madison, WI) and three randomly selected clones were sequenced on an ABI automatic sequencer. An 837-bp sequence representing the full length coat protein gene (GenBank Accession No. EF178505) was compared with homologous sequences from other ZYMV isolates using BioEdit and Mega 3.1 softwares. Genetic distances were calculated by Kimura's two-parameter method (2). Surprisingly, the Polish ZYMV isolate (ZYMV-Zug) was more closely related to ZYMV isolates from Asia than those from Europe. Pairwise comparisons of ZYMV-Zug with several other European ZYMV isolates (GenBank Accession Nos. DQ645729, AJ420020, AJ459956, AJ420014, AJ420019, DQ124239, and AJ420018) indicated an 81 to 82% nucleotide and 91 to 92% amino acid identity, while there was a 94% nucleotide and 99% amino acid identity with the Shanxi (GenBank Accession No. AY074808) and Shandong isolates (GenBank Accession No. AF513552) from China.

References: (1) J. Chen et al. Arch. Virol. 146:757, 2001. (2) S. Kumar et al. Brie. Bioinform. 5:150, 2004.
Soybean Disease Loss Estimates for the Top 10 Soybean Producing Countries in 1994
Authors: Wrather J. A. , Anderson T. R. , Arsyad D. M. , Gai J. , Ploper L. D. , Porta-Puglia A. , Ram H. H. , Yorinori J. T.
Published: May 2007

Soybean disease loss estimates were compiled for the 1994 harvested crop from the 10 countries with the greatest soybean production. The objective was to document the major soybean disease problems in these countries and any recent changes in the severity of individual soybean diseases. Total yield losses caused by Heterodera glycines in these 10 countries were greater than those caused by any other disease. Next in order of importance were stem canker, brown spot, and charcoal rot. The total yield loss due to disease during 1994 in these countries was 14.99 million metric tons, valued at $3.31 billion. Methods used to estimate soybean disease losses were field surveys, plant disease diagnostic clinic samples, variety trial data, information from field workers and university extension staff, research plots, grower demonstrations, and private crop consultant reports. Yield loss estimates due to a particular disease varied by country. For example, yield losses due to rust were reported from China and Indonesia, but no losses due to this disease were reported from any of the remaining eight countries. Soybean disease control research and extension efforts are needed to provide more effective preventive and therapeutic disease management strategies and systems to producers.
A New Geminivirus Associated with a Leaf Curl Disease of Tomato in Tanzania
Authors: Chiang B.-T. , Nakhla M. K. , Maxwell D. P. , Schoenfelder M. , Green S. K.
Published: May 2007

Leaf samples of tomato exhibiting yellow mottle, severe leaf curl, stunting, and upright stems were collected from Makutupora, Tanzania, in October 1994 by L. L. Black (AVRDC). Leaf tissue squashes on nylon membranes did not hybridize with DNA-A probes from tomato yellow leaf curl geminiviruses (TYLCVs) from Thailand (Thai) or Egypt (EG), an isolate of TYLCV-Isr (Israel). Polymerase chain reaction (PCR) with primer pair PAC1v1978/PAV1c715 (2), which specifically amplifies part of the rep (AC1) open reading frame (ORF), the intergenic region, and the cp (AV1) ORF of whitefly-transmitted geminiviruses, yielded a 1.5-kb fragment from a DNA extract of symptomatic tomato leaves. No virus-specific fragments were amplified from symptomless tomato leaves. The nucleotide sequence (GenBank accession no. U73478) of the PCR fragment (recombinant plasmid pAF1) was compared with the sequences of seven distinct subgroup III geminiviruses that infect tomato (1)—TYLCV-Isr, TYLCV-Sar (Sardinia), TYLCV-Thai, tomato leaf curl virus (TLCV)-;Aus (Australia), IndTLCV (India), TLCV-Ind (Bangalore I), and TLCV-Tai (Taiwan)—as well as three other subgroup III geminiviruses from the Old World: Indian cassava mosaic virus, African cassava mosaic virus, and mung bean yellow mosaic virus. Nucleotide sequence identities for the pairwise comparisons of the rep ORF (692 nucleotides) and the intergenic region (169 nucleotides) of this Tanzanian geminivirus with those of the 10 Old World geminiviruses showed low nucleotide identities, which were <79% for the rep ORF and <67% for the intergenic region. Since isolates of the same geminivirus usually have nucleotide sequence identities >90% (1), this Tanzanian geminivirus is considered to be different from all previously characterized Old World geminiviruses and is given the name TLCV-Tan. Further, tissue squash blots of samples previously collected from other areas in Tanzania gave strong positive reactions with the TYLCV-EG probe, so yet another geminivirus closely related to TYLCV-Isr may be present.

References: (1) M. Padidam et al. J. Gen. Virol. 76:249, 1995. (2) M. R. Rojas et al. Plant Dis. 77:340, 1993.
First Report of Curvularia lunata Associated with Stem Disease of Cassava
Authors: Msikita W. , Yaninek J. S. , Ahounou M. , Baimey H. , Fagbemissi R.
Published: May 2007

During surveys covering 60 cassava (Manihot esculenta Crantz) fields, randomly selected (between latitude 4°55′N and 8°16′N) in south Ghana, and 27 fields in southeast (between 4°50′N and 7°56′N) Nigeria, 8-month-old or older stems of some cassava genotypes were found to be covered by grayish brown lesions, predominantly on lignified portions of stems. Field disease incidence ranged from 0 to 80%, and severity from no disease to highly affected (>15 lesions per stem). To identify the pathogen, infected stem portions were cut out, surface disinfected, and cultured on potato dextrose agar (PDA) acidified with 0.4% (vol/vol) lactic acid. After 1 week, mycelia, conidiophores, and conidia were observed under a microscope, and the pathogen was identified as Curvularia lunata (Wakk.) Boedijn (confirmed also by the International My-cological Institute, Surrey, U.K.). To complete Koch's postulates, stem pieces of four cassava cultivars (Agric, Tchukunochi, TMS 30572, and Ben 86052), were disinfected in hot water (52°C for 5 min), transplanted in sterilized sand, and maintained in a greenhouse under natural light at 28 to 30°C. Before planting, five stems were wound inoculated (sliced with an epidermal scalpel) just above nodes, and a 5-mm-diameter PDA mycelial plug of C. lunata was applied to each wound or directly to unwounded nodes. Stems were then kept in a plastic bag for 24 h before planting. For each cultivar, five control stem pieces were similarly wounded but not treated with PDA plugs. All plants were maintained under >90% relative humidity. Control plants remained symptom-free whereas lesions and bud necrosis similar to field symptoms were observed on all inoculated plants within 1 month. Symptom development was quicker (2 to 3 weeks) on wound-inoculated than on nonwounded stems. Mortality of artificially wound-inoculated buds ranged between 30 and 100%, depending on genotype and manner of inoculation. Artificially infected stem and bud portions plated on PDA consistently yielded C. lunata. Bud sprouting of naturally infected cuttings was monitored over a period of 4 weeks after stem planting. When buds were completely colonized, sprouting was completely inhibited. However, partially colonized buds sprouted, but growth was reduced by 20 to 50% (depending on genotype), compared with healthy stems. This is the first report of C. lunata pathogenic on cassava.
Virus Diseases of Broad Bean in Spain
Authors: Fresno J. , Castro S. , Babin M. , Carazo G. , Molina A. , De Blas C. , Romero J.
Published: May 2007

Broad bean (Vicia faba L.) plants showing symptoms suggestive of viral infection, such as stunting, leaf roll, mosaic, chlorosis, necrosis, and yellowing, were observed in the Andalucia, Baleares, Cataluna, and Murcia regions of Spain. A 4-year field survey showed the presence of five viruses: bean leaf roll luteovirus (BLRV), beet western yellows luteovirus (BWYV), bean yellow mosaic potyvirus (BYMV), tomato spotted wilt tospovirus (TSWV), and cucumber mosaic cucumovirus (CMV). Identity of viruses was first determined by enzyme-linked immunosorbent assay and confirmed by at least one other method, such as inoculation to plant hosts, electron microscopy, molecular hybridization, or immunocapture-reverse transcriptase-polymerase chain reaction. Of the 250 samples assayed, 93 were positive for BYMV, 21 for BLRV, 10 for BWYV, 30 for TSWV, and 2 for CMV. Faba bean necrotic yellow virus (a single-strand DNA virus) and broad bean mottle bromovirus, which are widely distributed in the Mediterranean basin, were not detected in the samples analyzed. BYMV was distributed in all regions, whereas TSWV was restricted only to Mediterranean areas. To our knowledge, this is the first report of viruses infecting broad bean in Spain.
Patch Canker of Durio zibethinus Caused by Phytophthora palmivora in Brunei Darussalam
Authors: Sivapalan A. , Hj Hamdan F. , Junaidy M. A. H. M.
Published: May 2007

Durian (Durio zibethinus Murr.) is a popular fruit tree grown extensively in Southeast Asia for its highly valued fruits. A stem canker was found on many durian trees in an orchard in Sungai Liang, Brunei Darussalam. This disease, commonly known as patch canker, is widespread in other countries in this region. Although symptoms were found in the main trunk near the base and on lower branches, they were prominent at the point of branching between the main trunk and lateral branches. The symptoms were characterized by a reddish brown discoloration of the outer bark, areas of necrosis on the bark, and a reddish brown discoloration in the outer sapwood. Disease symptoms of the tree canopy ranged from gradual defoliation to dieback of twigs from the top of trees. Cultures of a single fungus derived from infected bark from canker margins were grown on potato dextrose agar and tap water agar. Abundant sporangial production by the fungus occurred on these media and the fungus was identified as Phytophthora palmivora (E. J. Butler) E. J. Butler. This is the first published report of patch canker of durian caused by P. palmivora in Brunei Darussalam. The disease could pose a threat to the durian industry in this country.