bluuebunny/crossref_metadata_2025 huggingface dataset:
First Report of Guignardia psidii, an Ascigerous State of Phyllosticta psidiicola, Causing Fruit Rot on Guava in Venezuela
Authors: González M. S. , Rondón A.
Published: May 2007

During August 2003, guava fruit (Psidium guajava L.) cv. Red Dominicana from Cojedes state in Venezuela showed circular, purple-to-brown lesions (0.5 to 1.0 cm) that spread over all surfaces and became black and shrunken on severely affected fruit. Symptomatic tissues were plated aseptically on potato dextrose agar (PDA). Colonies that were initially gray and turned black with age were consistently isolated. The fungus was characterized by dense, submerged, brown-to-black mycelium with septate hyphae. Ascocarps were perithecial, abundant, granulose, subglobose to cylindric obpyriform, solitary or aggregated, mostly unilocular with prominent long necks; ascocarp walls were stromatic, composed of several layers of cells, thick walled, and deeply pigmented on the outside. Asci were subclavate to cylindrical, stipitate, 44 to 84 × 7 to 9 μm, and eight-spored; asci walls were thick and bitunicate. Ascospores were unicellular, hyaline, guttulate, fusiform ellipsoid, widest in the mid-region with rounded ends and gelatinous plugs, and 12 to 17 × 4.5 μm. Conidiomata were pycnidial, intermixed among ascocarps, variable in shape, dark brown, solitary or aggregated, ostiolate, and with long necks up to 1 mm. Pycnidial walls were pseudoparenchymatic, multicellular, and composed of many layers of brown compressed cells. Conidiogenous cells were hyaline, subglobose to cylindrical, and smooth, and holoblastic. Conidia were hyaline, unicellular, obovate, 6 to 12 (7.5) × 5 to 8 μm, slightly truncate at the bases, rounded at apices, guttulate, and provided a gelatinous envelope and apical appendage. Appendages were hyaline, tubular, smooth, and 3.0 to 4.5 × 0.5 μm. The fungus is homothallic because single ascospores and single conidia developed ascigerous states. The ascigerous state was identified as Guignardia psidii (1) and the anamorph as Phyllosticta psidiicola (1,2). Pathogenicity tests were conducted on detached fruits inoculated with monosporic cultures. Pathogenesis and symptom development only occurred when a mixture of mycelium, ascospores, and conidia was used as inoculum. The fungus was reisolated from symptomatic fruit tissues. To our knowledge, this is the first report of Guignardia psidii, an ascigerous state of Phyllosticta psidiicola from guava fruits in Venezuela.

References: (1) B. A. Ullasa and R. D. Rawal. Curr. Sci. 53:435, 1984. (2) H. A. van der Aa. Page 95 in: No. 5, Stud. Mycol., 1973.
First Report of Sclerotinia minor on Allium vineale in North Carolina
Authors: Hollowell J. E. , Shew B. B.
Published: May 2007

Allium vineale L. (wild garlic) is a bulbous perennial that emerges in early spring in many agricultural fields. The soilborne fungus Sclerotinia minor Jagger is a major pathogen found in many peanut (Arachis hypogaea L.) production areas of northeastern North Carolina. During September 2002, symptoms of bleached, water-soaked foliage and wilting were observed on several wild garlic plants growing in a 0.8-ha (2-acre) peanut research plot in Perquimans County, NC. We had previously observed similar symptoms on wild garlic at another location. Two symptomatic wild garlic plants were collected from the field. In the laboratory, symptomatic tissues were excised into 1- to 2-cm sections, rinsed in tap water, towel dried, and placed on potato dextrose agar (PDA) for fungal isolation and identification. Pure cultures with small, black, irregular-shaped sclerotia (<2 mm) scattered abundantly over the culture surface were distinctive of S. minor. Pathogenicity of isolates was tested by inoculating leaf blades near the leaf axils of two symptom-free wild garlic plants (vegetative stage, 4 cm high) with fungal mycelium from 2-day-old cultures. Mycelial agar plugs (4 mm in diameter) were held in place with self-sticking bandaging gauze. Plants were misted, enclosed in plastic bags, and incubated at an ambient temperature (24°C) on the laboratory countertop. Fluffy mycelium developed on leaves within 2 days. Plants wilted and bleached water-soaked lesions formed within 6 days after inoculation. Sclerotia were produced on leaf blades after approximately 14 days. Following the incubation period, S. minor was reisolated from the inoculated plants. Two plants treated similarly with plugs of pure PDA remained healthy over the incubation period. The performance of Koch's postulates confirmed that wild garlic is a host of S. minor. Although few monocots have been reported as hosts of S. minor, the fungus has been reported on two other species of Allium (A. cepa and A. satium), Gladiolus spp., and Cyperus esculentus (1,2). Weed hosts may support populations of S. minor during rotations to nonhosts, serve as reservoirs of inoculum, or act as infection bridges in peanut fields.

References: (1) D. F. Farr et al. Fungal Databases. Systematic Botany and Mycology Laboratory. On-line publication. ARS, USDA, 2005. (2) M. S. Melzer et al. Can. J. Plant Pathol. 19:272, 1997.
First Report of Botrytis Blight of Peanut Caused by Botrytis cinerea in Georgia
Authors: Woodward J. E. , Brenneman T. B. , Kemerait R. C. , Culbreath A. K. , Clark J. R.
Published: May 2007

Because of the importance of spotted wilt caused by Tomato spotted wilt virus (TSWV), most peanut (Arachis hypogaea L.) breeding programs in the southeastern United States are focusing on developing resistance to TSWV. Many of the cultivars with improved resistance to TSWV are late maturing, requiring 150 days to reach optimum maturity. This factor could greatly impact disease problems at harvest. During November of 2004, an unknown disease was observed on peanut cvs. Georgia 02-C and Hull in a commercial field in Appling County. Symptoms included wilting stems with water-soaked lesions and a dense, gray mold growing on infected tissues. Final disease incidence was less than 5%. For isolation, diseased tissue was surface sterilized by soaking in 0.5% sodium hypochlorite for 1 min, air dried, plated on potato dextrose agar (PDA), and incubated at 20°C. Botrytis cinerea Pers.:Fr., causal agent of Botrytis blight, was isolated from the margins of infected tissue. Mycelia were initially white but became gray after 72 h at which time tall, branched, septate conidiophores formed. Mature, unicellular, ellipsoid, hyaline conidia (8.9 × 10.4 μm) formed in botryose heads (1). Hard, black, irregular-shaped sclerotia formed after 2 weeks. Stems of greenhouse-grown peanut plants (cv. Georgia Green) were inoculated with PDA plugs colonized with either B. cinerea or B. allii Munn. Inoculations were made 3 cm below the last fully expanded leaf on wounded and nonwounded tissue. Noncolonized PDA plugs served as controls (n = 9). Plants were arranged in a dew chamber at 20°C in a randomized complete block design. Lesions and spore masses identical to those observed in the field appeared 3 to 5 days after being inoculated with B. cinerea. The B. allii inoculations caused only superficial lesions. After 5 days, mean lesion lengths for B. cinerea were 59 and 37 mm for wounded and nonwounded inoculations, respectively. B. cinerea was recovered from 100% of the symptomatic tissues. Botrytis blight is considered a late-season disease that occurs in cool, wet weather (3). Symptoms similar to those of Botrytis blight were observed on mature and over-mature peanut in Georgia and have been cited as “unpublished observations” (2); however, to our knowledge, this is the first report of the disease in Georgia. Although Botrytis blight is not considered a major peanut disease, it may become more prevalent at harvest as producers utilize late-maturing cultivars to manage spotted wilt.

References: (1) H. L. Barnett and B. B. Hunter. Illustrated Guide of Imperfect Fungi. 4th ed. The American Phytopathological Society, St. Paul, MN, 1998. (2) K. H. Garren and C. Wilson. Peanut Diseases. Pages 262–333 in: The Peanut, the Unpredictable Legume. The National Fertilizer Assoc. Washington D.C. 1951. (3) D. M. Porter. Botrytis blight. Pages 10–11 in: Compendium of Peanut Diseases. 2nd ed. N. Kokalis-Burelle et al., eds. The American Phytopathological Society, St. Paul, MN. 1997.
First Report of Brown Stripe of Saltgrass Caused by Bipolaris heveae in Colorado
Authors: Lang J. , Tisserat N. , Koski A. , Christensen D. , Qian Y.
Published: May 2007

Inland saltgrass (Distichlis spicata var. stricta (L.) Greene) is indigenous to western North America and Australia and is a dioecious, rhizomatous, perennial, warm-season grass. It is commonly found in areas where salinity, alkalinity, and drought have eliminated many other types of vegetation (1). It has potential for revegetation of mine spoils or use along roadsides (2). During September 2004, multiple lenticular, brown lesions were observed on leaves of saltgrass accession no. 1023 at the Horticulture Field Research Center, Colorado State University, Fort Collins. Segments of symptomatic leaf tissue were surface sterilized in 0.5% sodium hypochlorite and placed on one-quarter-strength potato dextrose agar and incubated at 25°C in the dark. Dark green fungal colonies with aerial mycelium consistently grew on the medium. Slightly curved, ellipsoidal, pale-to-golden brown, smooth conidia 46 to 80 μm long and 13 to 17 μm wide (average 64.5 × 14.7 μm) with 6 to 9 septations formed after 7 days in cultures grown on V8 juice agar. The morphology and bipolar germination of conidia was consistent with the genus Bipolaris, however, conidia were often shorter than previously reported (3). The rDNA internal transcribed spacer (ITS) regions of one isolate were amplified using polymerase chain reaction (PCR) with universal fungal rDNA primers ITS1 and ITS4. PCR products were sequenced (555 bp) and exhibited 99% nucleotide identity to Bipolaris heveae isolates collected from zoysiagrass and bermudagrass in Japan (3) and rubber in Nigeria (4). To confirm pathogenicity, a suspension of 104 conidia per ml of water containing 0.1% Tween 20 was sprayed on saltgrass leaves to runoff. Plants were covered with transparent plastic bags and incubated at 25°C in the dark. After 72 h, the bags were removed and plants were placed in the greenhouse. Brown stripe symptoms were observed on all plants after 7 days, and B. heveae was consistently isolated from symptomatic tissue. To our knowledge, this is the first report of brown stripe on inland saltgrass caused by B. heveae.

References: (1) D. J. Hansen et al. Am. J. Bot. 63:635, 1976. (2) K. A. Pavlicek et al. J. Range Manag. 30:377, 1977. (3) T. Tsukiboshi et al. Mycoscience 46:17, 2005. (4) G. Zhang and M. L. Berbee. Mycologia 93:1048, 2001.
Morphologic and Pathometric Characterization of the Asian Soybean Rust (Phakopsora pachyrhizi) on Kudzu (Pueraria lobata) in Argentina
Authors: Carmona M. A. , Fortugno C. , Achával P. L.
Published: May 2007

Asian soybean rust (ASR) is a very important disease caused by Phakopsora pachyrhizi. The disease has emerged as a major threat to soybean production in South America since 2001. During the 2003-2004 growing season, P. pachyrhizi spread rapidly throughout most soybean-growing areas of northwestern and northeastern Argentina (1). One widespread naturalized host in the northeastern part of the country is kudzu (Pueraria lobata). Plants of severely infected kudzu were sampled during January 2005 in Cerro Azul (29°29′S Misiones Province) to quantify P. pachyrhizi infection and morphologically characterize the fungus in leaves. The number of lesions, uredinia per cm2, and uredinia per lesion were recorded from the undersides of 50 leaflets that were visually showing rust symptoms. The average number of lesions and uredinia per cm2 was 14 (4 to 22), and 24 (5 to 78), respectively. The number of uredinia per lesion was 3 (1 to 10). Twenty leaflets from the lower canopy averaged 55 (42 to 78) uredinia per cm2. The average size of urediniospores was 18.4 μm wide (12.5 to 22.5) and 22.7 μm long (17.5 to 26.3). Although important epidemics of ASR have not been registered on soybean crops in January (2) because of adverse conditions, the fungus was observed on kudzu plants. To our knowledge, this is the first report of morphologic and pathometric characterization of P. pachyrhizi on kudzu in Argentina.

References: (1) M. A. Carmona et al Plant Dis. 89:109, 2005. (2) SINAVIMO, Sistema Nacional Argentino de Vigilancia y Monitoreo de plagas. Roya de la soja: Resultados de la campaña 2004-2005. On-line publication. SENASA, 2005.
Leaf Spot Caused by Alternaria sp. on Iberis sempervirens in Italy
Authors: Garibaldi A. , Minuto A. , Gullino M. L.
Published: May 2007

Iberis sempervirens (candytuft) is increasingly grown in Liguria (northern Italy) as a potted plant for ornamental purposes, particularly under cool-weather conditions. At the end of the summer of 2003, extensive necrosis was observed on leaves and young stems of 4-month-old plants grown in 14-cm diameter pots outdoors at a commercial farm. In many cases, on the upper side of the leaves, necrotic spots were surrounded by a chlorotic halo that turned progressively black. The necrotic areas often coalesced, generating larger and irregularly shaped spots. On the lower side of the leaves, no chlorotic areas were observed. Severely affected plants were defoliated. Infected plants rarely died, but the presence of lesions on mature plants decreased aesthetic quality and subsequently market value. The disease occurred on 40% of plants at each of the two farms. Leaf spots contained dark brown, multicellular pear-shaped conidia. Conidia were 22.5 to 50.0 μm (average 32.8 μm) long and 7.5 to 15.0 μm (average 12.3 μm) wide, with 5 to 7 longitudinal cross walls and an average of 6 to 7 single cells. From infected leaves, a fungus identified on the basis of its morphological characteristics as Alternaria sp. was consistently isolated on potato dextrose agar. Pathogenicity tests were performed by spraying leaves of healthy 12-month-old potted I. sempervirens plants with a spore and mycelial suspension (105 CFU/ml). Plants without inoculation served as control. Ten plants were used for each treatment. Plants were covered with plastic bags for 10 days after inoculation and kept outdoors for 60 days at temperatures ranging from 0 to 32°C (average 12°C). The first lesions developed on leaves 45 days after inoculation, while control plants remained healthy. From such lesions, Alternaria sp. was consistently reisolated. The pathogenicity test was carried out twice. The presence of A. brassicae was reported in Tanganica on Iberis sp., I. umbellata in Denmark (2), and I. amara in the United States (4); A. matthiolae was observed on seeds of I. amara and I. umbellata (3). A leaf spot incited by Alternaria sp. on I. amara was observed in Florida (1). This is, to our knowledge, the first report of Alternaria sp. on I. sempervirens in Italy as well as worldwide.

References: (1) S. A. Alfieri et al. Index of Plant Diseases in Florida. Bull. 11, 1984. (2) P. Neergaard. Rev. Appl. Micol. 18:572, 1939. (3) P. Neergaard. Rev. Appl. Micol. 25:382, 1946). (4) R. D. Raabe. Comb. Proc. Int. Plant Propagators Soc. 40:160, 1991.
First Report of Beet virus Q in Spain
Authors: Rubies Autonell C. , Ratti C. , Resca R. , De Biaggi M. , Ayala García J.
Published: May 2007

Beet virus Q (BVQ) is a member of the genus Pomovirus that is transmitted by Polymyxa betae Keskin. Initially described as the Wierthe serotype of Beet soilborne virus (BSBV), BVQ is now considered a distinct virus species based on its genomic properties (1). BVQ is commonly found in fields where BSBV and the causal agent of rhizomania disease, Beet necrotic yellow vein virus (BNYVV), are also present. Simultaneous infection of sugar beet plants with multiple virus species could affect disease symptom expression (4). For this reason, the pathogenicity of BVQ and its role in the epidemiology of rhizomania disease remain a subject of study. During 2004, six soil samples were collected from different sites in the Castilla-La Mancha Region in Spain (Albacete and Ciudad Real provinces) where rhizomania symptoms were observed in BNYVV-tolerant sugar beet cultivars. Soil from the Hainaut Region of Belgium, infected with BNYVV, BSBV, and BVQ and supplied by Prof. C. Bragard (Unité de Phytopathologie, Université Catholique de Louvain, Belgium) was used as a positive control. Sugar beet plants (cv. Asso) were grown in the soil samples for 45 days at 24°C and then root tissue was harvested. All samples were analyzed using enzyme-linked immunosorbent assay (ELISA) with commercial BNYVV antiserum (BIOREBA AG, Reinach, Switzerland) and BSBV/BVQ antisera (IC10 and 6G2) supplied by R. Koenig (Federal Biological Research Centre for Agriculture and Forestry, Braunschweig, Germany). Total RNA extracted from sugar beet roots as previously described (3) was tested using reverse transcription-polymerase chain reaction (RT-PCR). Primers BVQ3F (5′-GTT TTC AAA CTT GCC ATC CT-3′) and BVQ3R2 (5′-CCA CAA TGG GCC AAT AGA-3′), which amplify a 690-bp fragment of the triple gene block region of BVQ RNA 3, were designed based on the published sequence (GenBank Accession No. AJ223598). The presence of BSBV and BNYVV was assayed using RT-PCR with previously described primers (2,3). BVQ was detected from plants grown in soil collected from La Roda (Albacete) in Spain and from Hainaut in Belgium. The fragments amplified from Spanish sample with BVQ3F and BVQ3R2 (GenBank Accession No. AY849375) showed 95.9% nucleotide sequence identity with the previously published sequence of BVQ (1). The La Roda BVQ isolate was mechanically transmitted to Chenopodium quinoa from infected sugar beet root tissue. BVQ was detected using RT-PCR in local lesions that appeared approximately 5 days after inoculation and subsequently spread along veins. To our knowledge, this is the first report of BVQ in soil from Spain, although it has been previously reported in Belgium, Bulgaria, France, Germany, Hungary, and the Netherlands (2). BSBV and BNYVV (type A) were detected in all six Spanish samples, as well as in the Belgian soil.

References: (1) R. Koenig et al. J. Gen. Virol. 79:2027, 1998. (2) A. Meunier et al. Appl. Environ Microbiol. 69:2356, 2003. (3) C. Ratti et al. J. Virol. Methods 124:41, 2005. (4) C. Rush Annu. Rev Phytopathol 41:567, 2003.
Molecular Characterization of a Begomovirus Associated with Tomato Leaf Curl Disease in Uganda
Authors: Shih S. L. , Green S. K. , Tsai W. S. , Ssekyewa C.
Published: May 2007

During the summer of 2003, leaf curl symptoms were observed in tomato (Lycopersicon esculentum) plantings in the Iganga District of Uganda. Begomoviral infection was suspected. Twelve symptomatic samples were collected. Begomoviral DNA was extracted and amplified using polymerase chain reaction (PCR) with the begomovirus-specific degenerate primer pair PAL1v1978/PAR1c715 (4). The expected 1.4-kb PCR products were obtained from 11 of 12 samples. The 1.4-kb PCR product of one of the samples was cloned and sequenced. Based on the sequence of the 1.4-kb DNA product, specific primers were designed to complete the DNA-A sequence. The DNA-A consisted of 2,747 nucleotides (GenBank Accession No. DQ127170) and was found to contain seven predicted open reading frames (ORFs V1, V2, C1, C2, C3, C4, and C5). A BLAST analysis was conducted with geminivirus sequences available in the GenBank database at the National Center for Biotechnology Information (Bethesda, MD), and MegAlign (DNASTAR, Inc, Madison, WI) software was used for further comparisons. The DNA-A sequence of the virus associated with leaf curl of tomato from Uganda showed less than 79% sequence identity with cassava mosaic viruses from Uganda (GenBank/EMBL Accession Nos. AF126800, AF126802, AF126804, AF126806, and Z83257), the only begomoviruses from the country so far in the public domain. Highest sequence identity (83%) was with Tomato leaf curl Mayotte virus from Dembeni, Mayotte, Comoros Islands (ToLCYTV-[Dem], EMBL Accession No. AJ865341). Pairwise comparison with ToLCYTV-[Dem] showed 60, 88, 91, 82, 84, 86, and 80% sequence identities in the intergenic region, V2, V1, C1, C2, C3, and C4 ORFs, respectively. Only low sequence identities (ranging from 71 to 82%) were obtained with other tomato bego-moviruses reported from Africa (GenBank/EMBL Accession Nos. AF261885, AJ865337-AJ865340, AY044137-AY044139, AY502934, AY502936, AY594174, AY736854, and U73498). There was no evidence for the presence of DNA-B or DNA-beta using PCR with the DNA-B specific primer pairs DNABLC1/DNABLV2 and DNABLC2/DNABLV2 (2) and the DNA-beta primer pair Beta01/Beta02 (1), respectively. Detection of possible recombination was by RDP2 software (3) using DNA-A sequences of begomoviruses from Uganda and tomato begomoviruses from Africa. The DNA-A was found to contain a small recombinant fragment from ToLCYTV-[Dem] in the 411 to 969 nucleotide position with 92% sequence identity. Based on DNA-A sequence comparisons, the tomato leaf curl virus from Uganda most likely constitutes a distinct new begomovirus.

References: (1) R. W. Briddon et al. Mol. Biotechnol. 20:315, 2002. (2) S. K. Green et al. Plant Dis. 85:1286, 2001. (3) D. P. Martin et al. Bioinformatics 21:260, 2005. (4) M. R. Rojas et al. Plant Dis.77:340, 1993.
First Report of Damping-Off of Wild Rice in California Caused by Pythium torulosum
Authors: Marcum D. B. , Davis R. M.
Published: May 2007

During 1994, damping-off of wild rice (Zizania palustris L.) in a single field in eastern Shasta County, CA resulted in near total stand failure. Since then, the disease was observed in at least 11 other fields with varying levels of stand loss. In all cases, the affected wild rice was grown as a volunteer crop following one or more years of wild rice production. Symptoms included a dark red discoloration and necrosis of the primary root followed by seedling death. When the red discoloration was limited to secondary roots, the plants often survived. Pythium torulosum, readily recovered from symptomatic roots by isolation on PARP media, was identified by morphological structures produced on grass blades in water (homothallic with smooth-walled oogonia, plerotic oospores, monoclinous antheridia, and inflated filamentous sporangia) and a 99.2% internal transcribed spacer sequence similarity of the rDNA (1). To complete Koch's postulates, inoculum of two isolates of P. torulosum grown on moistened cornmeal/sand (2%/98% [v/v]) for 3 weeks at 25°C were combined and mixed into sterilized sandy loam soil at a rate of 30 cm3 inoculum per liter of soil. Sterilized noninfested soil was used as a control treatment. Twenty wild rice seeds (cv. Franklin) were sown in each of four replicate 20-cm-diameter pots in each treatment. Plants were submerged in water and maintained in a greenhouse at 18 to 25°C. After 8 weeks, plants stands were reduced 50% in infested pots; dry weights of infected plants were reduced by 45% relative to the controls. The fungus was reisolated from symptomatic plants but not from the plants grown in noninfested soil. The experiment was repeated with similar results. To our knowledge, this is the first report of damping-off of wild rice caused by P. torulosum.

Reference: (1) C. A. Levesque and W. A. M. DeCock. Mycol. Res. 108:1363, 2004.
Development of a Real-Time, Quantitative PCR for Detection of the Columbia Basin Potato Purple Top Phytoplasma in Plants and Beet Leafhoppers
Authors: Crosslin J. M. , Vandemark G. J. , Munyaneza J. E.
Published: May 2007

A quantitative, real-time “TaqMan” polymerase chain reaction assay (real-time PCR) was developed which was capable of detecting and quantifying a group 16SrVI phytoplasma in DNA extracts prepared from infected tomatoes, potatoes, and beet leafhoppers (Circulifer tenellus). Primers and probe were designed from the 16S rRNA gene of the Columbia Basin potato purple top phytoplasma, which is closely related to the beet leafhopper transmitted virescence agent. The detection limit in phytoplasma-infected tomato DNA was approximately 50 pg. The concentration of phytoplasma varied considerably among potato plants showing symptoms of purple top. The pathogen was readily detected in extracts from single or groups of five beet leafhoppers. As with infected potatoes, the concentration of phytoplasma in individual leafhoppers was variable. The assay also detected aster yellows (group 16SrI) and pigeon pea witches'-broom (group 16SrIX) phytoplasmas in infected periwinkle plants. The real-time PCR was at least as sensitive as the commonly used and more labor-intensive nested PCR for detection of the pathogen.
Optimizing Soil Disinfestation Procedures for Fresh Market Tomato and Pepper Production
Authors: Chellemi D. O. , Mirusso J.
Published: May 2007

Combinations of soil fumigation with a mixture of 1,3-dichloropropene (1,3-D) plus chloropicrin (Pic) and soil solarization for 7 days were evaluated under different plastic films and sequences of application for their effects on soilborne pests and marketable yield of fresh market tomato (Lycopersicon esculentum) and pepper (Capsicum annuum). Shank injection of fumigants under a virtually impermeable film (VIF) using a novel application apparatus dramatically improved their retention in the soil. Survival of Fusarium oxysporum f. sp. lycopersici in soil declined significantly when fumigation or solarization was combined with VIF compared with either soil disinfestation treatment applied under low-density polyethylene. When compared with an untreated control, significant reductions in yellow nutsedge (Cyperus esculentus), purple nutsedge (C. rotundus), and root-knot nematodes (Meloidogyne spp.) were achieved with a reduced dosage of fumigant when applications were made 7 days after planting beds were covered with VIF. A 7-day delay in fumigant application in beds covered by low-density polyethylene significantly increased marketable yield of pepper when compared with an untreated control. The results demonstrate that chemical and nonchemical soil disinfestation methods can be combined with novel application technology and procedures to improve their spectrum of pest control and reduce fumigant application rates.
First Report of Arceuthobium hondurense in Department El Paraiso, Honduras
Authors: Mathiasen R. , Melgar J.
Published: May 2007

The Honduran dwarf mistletoe, Arceuthobium hondurense Hawksw. & Wiens (Viscaceae), has only been reported from three general areas in Honduras (2). During September 2005, we found a fourth location for this rare dwarf mistletoe south of San Lucas in Department El Paraiso (13°52′58″N, 86°58′04″W; elevation 1,350 m). The mistletoe was parasitizing Pinus oocarpa Schiede, and many trees were severely infected in this area. Several dead trees were also observed with evidence of past dwarf mistletoe infection (witches' brooms). Although this report only extends the distribution approximately 40 km to the southeast of populations of this mistletoe in Department Francisco Morazan, to our knowledge, this is the first report of A. hondurense in Department El Paraiso. At one time, A. hondurense was thought to be in danger of extinction (1), but it is now known from four separate locations in Honduras and has been discovered in a few locations in southern Mexico (2). Nevertheless, this dwarf mistletoe remains one of the rarest mistletoes known. Specimens of A. hondurense from El Paraiso have been deposited at the Deaver Herbarium, Northern Arizona University, Flagstaff (Accession No. 80338).

References: (1) F. Hawksworth and D. Wiens. Dwarf mistletoes: Biology, pathology, and systematics. USDA For. Serv. Agric. Handb. 709, 1996. (2) R. Mathiasen et al. Madrono 50:115, 2003.
First Report of “Candidatus Phytoplasma asteris”-Related Strains in Brassica rapa in Saskatchewan, Canada
Authors: Olivier C. Y. , Séguin-Swartz G. , Hegedus D. , Barasubiye T.
Published: May 2007

“Candidatus phytoplasma asteris” and related strains (i.e., aster yellows group 16SrI) have been associated with diseases of numerous plant species worldwide. Symptoms of aster yellows (AY) have been reported on rapeseed/canola (Brassica napus and B. rapa) crops in Saskatchewan (SK) and Manitoba, Canada since 1953 (2). Symptoms generally include stunting, virescence, leaf yellowing or purpling, phyllody, and formation of bladder-like siliques. A total of 120 mature B. rapa cv. AC Sunbeam plants exhibiting AY symptoms were collected in commercial fields near Medstead, SK during 2003 and 2004 (one field per year). As described previously (4), total genomic DNA was extracted from leaf, stem, roots, and seeds collected from the 120 plants, from seeds from the seed lots sown in 2003 and 2004, and from leaf and stem tissue of 20 greenhouse-grown plants from each seed lot. The latter DNA samples were assayed for phytoplasma DNA by a nested polymerase chain reaction (PCR) assay incorporating phytoplasma universal 16S rRNA primer pairs P1/P6 (1) followed by R16R2/R16F2 (4). Seed samples analyzed from the 2003 and 2004 seed lots and tissues of the 40 greenhouse-grown plants all tested negative for phytoplasma DNA using this assay. Leaf, stem, and/or root tissues of all plants collected in the field in 2003 (60 plants) and 2004 (60 plants) and 71.1% (315 of 443) of seed samples (five seeds per sample) tested positive for the presence of phytoplasma DNA, as evidenced by the presence of an expected band of 1.2 kb on the gels after the second amplification with primers R16R2/R16F2. Nested PCR products from plant samples collected in 2003 were cloned, sequenced, and compared with phytoplasma sequences archived in the GenBank nucleotide database. On this basis, phytoplasmas detected in plants or their seeds collected in 2003 were found to be most similar (98.8%) to CHRY (Accession No. AY180956), a 16SrI-A subgroup strain, or were most similar (98.9%) to isolate 99UW89 (Accession no. AF268407), a known 16SrI-B subgroup strain. Sequences of phytoplasmas detected in plants or their seeds in 2004 were obtained by direct sequencing of rRNA products amplified from samples using PCR incorporating primer pairs P1/P6 and P4/P7 (3). Analysis of sequence data revealed that phytoplasmas in these plants were all most similar (99.5%) to AY-WB (Accession no. AY389828), a 16SrI-A subgroup member. The nucleotide sequences have been deposited with GenBank under Accession nos. DQ404346, DQ404347, and DQ411470. To our knowledge, this is the first report of 16SrI-A and 16SrI-B subgroup phytoplasmas infecting plants and seed of B. rapa in Saskatchewan.

References: (1) I.-M. Lee et al. Phytopathology, 83:834, 1993. (2) W. E. Sackston. Can. Plant Dis. Surv. 33:41, 1953. (3) L. B. Sharmila et al. J. Plant Biochem. Biotech. 13:1, 2004. (4) E. Tanne et al. Phytopathology, 91:741, 2001.
First Report of Leaf Spot Caused by a Cercosporella sp. on Acroptilon repens in the United States
Authors: Eskandari F. M. , McMahon M. B. , Bruckart W. L. , Littlefield J.
Published: May 2007

In August 2005, leaf spots were observed on a sample of Acroptilon repens (L.) DC. (Russian knapweed [RK]) collected at the Charles M. Russell National Wildlife Refuge in Montana. Symptoms included circular to subcircular brown spots, 1 to 18 mm in diameter, with indefinite margins that sometimes had a thin, purple-to-rose border. Leaves placed in moist chambers developed conidiophores and conidia within 48 h. Stroma were subcuticular, pale yellowish; conidiophores were hyaline, zero to two septate, thin walled, smooth, unbranched, 31 to 91 × 2.8 to 5.6 μm; and conidia were solitary or in secondary short chains, ovoid to subclavate, 13 to 52 × 3.2 to 6.8 μm, zero to three septate, hyaline, and thin walled. Conidial scars and hyla were umbronate, somewhat thickened, refractive, and not darkened. In three tests, 50 RK plants spray inoculated with 106 conidia/ml developed symptoms similar to those on the sample and the fungus was reisolated each time. Fungal identification, Cercosporella acroptili (Bremer) U. Braun, was based on morphology (1) and comparisons with the type specimen and a Turkish isolate (FDWSRU 98-001). ITS 1 and 2 sequences (GenBank Accession No. 779164) also were identical to a known isolate of C. acroptili. A specimen (BPI No. 871029) has been submitted to the USDA-ARS-SBML. RK is a major weed pest in the western United States and has been target of biological control research in recent years.

Reference: (1) U. Braun. A Monograph of Cercosporella, Ramularia, and Allied Genera (Phytopathogenic Hyphomycetes) Vol. 1. IHW-Verlage, Eching-by-Munich, 1995.
First Report of Botrytis Gray Mold on Common Calla Lily in Buenos Aires, Argentina
Authors: Rivera M. C. , Lopez S. E.
Published: May 2007

Common calla lily (Zantedeschia aethiopica (L.) Spreng., family Araceae) is an evergreen herbaceous South African ornamental plant that forms a tuft of fleshy-stalked, glossy, dark green leaves. At bloom during the summertime, large, funnel-shaped, waxy-white spaths that surround a bright yellow spadix form at the end of high stalks. In August 2003, large, irregular brown spots with a 3- to 4-mm yellow halo were observed on leaves of 10 plants growing near Japanese quince shrubs (Chaenomeles lagenaria (Loisel.) Koidz.) in Escobar, Buenos Aires. Debris of Japanese quince petals were attached to the center of the lesions with profuse sporulation of Botrytis cinerea Pers. (1). Pathogen spores were disposed on potato dextrose agar (PDA) and incubated at 22°C. Mycelium was initially whitish and turned gray with age. Black conidiophores bore botryose heads of hyaline, ellipsoid, unicellular conidia, gray in mass, 7.5 to 10.5 μm × 6.8 to 7.5 (average 9.2 to 7 μm). Black, irregular sclerotia formed at random in culture. Inoculum was prepared from 7-day-old cultures on PDA. Six flowering common calla lilies planted in 5-liter plastic pots were inoculated by spraying a suspension of 2.5 × 106 conidia per ml of sterile distilled water. Six healthy plants were sprayed with sterile distilled water. Each plant was covered with a transparent polyethylene bag for 3 days and kept at 21°C under a 12-h photoperiod. After a 12-day incubation period, leaves showed elliptic to irregular brown spots surrounded by yellow halos. Tiny round to irregular brown spots developed on flower spaths that finally blighted. Water-treated plants remained symptomless. Koch's postulates were fulfilled by pathogen reisolation from diseased organs. To our knowledge, this is the first report of B. cinerea on Z. aethiopica in Argentina. Infection efficiency of B. cinerea increases when inoculated petals are positioned on leaves (2), which has epidemiological importance in landscapes with association of plant species that are potential hosts of this pathogen.

Reference: (1) M. V. Ellis and J. M. Waller. No. 431 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1974. (2) C. Sirjusingh et al. Plant Dis. 80:154, 1996.
First Report of Soybean Rust Caused by Phakopsora pachyrhizi on Phaseolus spp. in the United States
Authors: Lynch T. N. , Marois J. J. , Wright D. L. , Harmon P. F. , Harmon C. L. , Miles M. R. , Hartman G. L.
Published: May 2007

Phakopsora pachyrhizi Syd. & P. Syd., the cause of soybean rust, was first observed in the continental United States in November 2004 (2). During the growing season of 2005, P. pachyrhizi was confirmed on soybean (Glycine max) and/or kudzu (Pueraria montana) in nine states in the southern United States. It is known that P. pachyrhizi has a much larger host range within the Fabaceae family. On 29 September 2005 in Quincy, FL, 45 entries of mostly large-seeded legumes were planted next to soybeans that were infected with P. pachyrhizi. Several seeds of each entry were planted on one hill. Soybean plants growing adjacent to these potential hosts had 15 to 25% of the leaf area affected, 95% incidence, and 73% defoliation on 16 November. On 7 December 2005, all the plants of Phaseolus coccineus L. (scarlet runner bean, PI311827), Phaseolus lunatus L. (lima bean, PI583558), and two Phaseolus vulgaris L. (kidney bean) cvs. Red Hawk and California Early Light Red Kidney (CELRK) were found to have leaves with suspected rust lesions. These plants were at physiological maturity but had not senesced. None of the hosts had been inoculated other than from spores produced by the adjacent rust-infected soybean plants or from unknown locations. On the basis of microscopic examination, suspected infected leaves from plants of the Phaseolus spp. had rust pustules characteristic of P. pachyrhizi uredinia. Uredinia were counted within a randomly selected 2-cm2 area of one leaf of each sample. The mean and range of uredinia per lesion for Phaseolus coccineus was 29 uredinia with a range of 0 to 3 uredinia per lesion, Phaseolus lunatus had 2 uredinia with 0 to 1 uredinium per lesion, Phaseolus vulgaris cv. Red Hawk had 22 uredinia with 0 to 5 uredinia per lesion, and Phaseolus vulgaris cv. CELRK had 43 uredinia with 0 to 4 uredinia per lesion. Polymerase chain reactions using two sets of primers (Ppa1/Ppa2 and Pme1/Pme2) were performed on DNA extracted from leaves of the three species with sporulating rust pustules (1). The results of these tests and further tests conducted by the USDA/APHIS confirmed that P. pachyrhizi was the causal organism for the observed rust.

References: (1) P. F. Harmon et al. On-line publication. doi:10.1094/PHP-2005-0613-01-RS. Plant Health Progress, 2005. (2) R. W. Schneider et al. Plant Dis. 89:774, 2005.
Puccinia acroptili on Russian Knapweed in Colorado, Montana, and Wyoming
Authors: Bruckart W. L. , Eskandari F. M. , Becktell M. C. , Bean D. , Littlefield J. , Pilgeram A. L. , Sands D. C. , Aime M. C.
Published: May 2007

Acroptilon repens (L.) DC. (Russian knapweed) is a long-lived perennial weed from central Asia that is widely distributed in the western United States (U.S.). Recently, accessions of a rust disease were collected from Colorado (CO), Montana (MT), and Wyoming (WY) for comparison with Eurasian isolates. U.S. accessions had two-celled teliospores with slight constrictions in the middle and urediniospores with three germ pores ± equatorial in location. Urediniospores were (state, width × length, [n = 100]): CO, 16.4 to 25.7 × 19.2 to 27.0 μm; MT, 18.4 to 23.1 × 17.4 to 24.6 μm; and WY, 18.0 to 26.2 × 20.2 to 26.7 μm. These were similar to those of 16.6 to 25.7 × 21.2 to 28.0 μm from two New Mexican (NM) herbarium specimens (BPI Nos. 1107952 and 1110177) (1). Teliospores measured 19.9 to 27.7 × 29.8 to 47.4 μm, 17.4 to 26.0 × 32.4 to 44.2 μm, 16.5 to 27.5 × 29.4 to 45.7 μm, and 18.7 to 27.6 × 31.0 to 46.4 μm for CO, MT, WY, and NM accessions, respectively. These rust isolates have been identified as Puccinia acroptili Syd. on the basis of host plant record and spore morphology (2). To our knowledge, this is the first record of P. acroptili in CO, MT, and WY. Besides NM, P. acroptili has been reported in North America from California, British Columbia, and Saskatchewan.

References: (1) M. E. Palm and S. G. Vesper. Plant Dis. 75:1075, 1991. (2) D. B. O. Savile. Can. J. Bot. 48:1567, 1970.
First Report of Soybean Rust Caused by Phakopsora pachyrhizi in North Carolina
Authors: Koenning S. R. , Moore A. D. , Creswell T. C. , Abad G. Z. , Palm M. E. , McKemy J. M. , Hernández J. R. , Levy L. , DeVries-Paterson R.
Published: May 2007

Asian soybean rust, caused by Phakopsora pachyrhizi Sydow, has been known to occur in the eastern hemisphere for nearly a century. More recently, it was reported from South America in 2002 and the continental United States in Louisiana in November 2004 (1,2). Subsequently, P. pachyrhizi was confirmed in Alabama, Arkansas, Georgia, Florida, Missouri, Mississippi, South Carolina, and Tennessee in 2004. Surveys conducted in North Carolina in late November 2004 failed to detect this pathogen. Symptoms of the disease were first observed on soybean (Glycine max (L.) Merr.) in North Carolina on 25 October 2005 in farmers' fields in the counties of Brunswick, Columbus, and Robeson. Typical pustules and urediniospores were readily apparent on infected leaves when viewed with a dissecting microscope. Urediniospores were obovoid to broadly ellipsoidal, hyaline to pale yellowish brown with a minutely echinulate thin wall, and measured 18 to 37 × 15 to 24 μm. This morphology is typical of soybean rust caused by P. pachyrhizi or P. meibomiae, the latter is a less aggressive species causing soybean rust in the western hemisphere (1). DNA was extracted from leaves containing sori using the Qiagen DNeasy Plant Mini kit (Valencia, CA). P. pachyrhizi was detected using a real-time polymerase chain reaction (PCR) protocol that differentiates between P. pachyrhizi and P. meibomiae in a Cepheid thermocycler (Sunnyvale, CA) with appropriate positive and negative controls. The PCR master mix was modified to include OmniMix beads (Cepheid). Field diagnosis of P. pachyrhizi was confirmed by the USDA/APHIS on 28 October 2005. Soybean rust was identified in subsequent surveys of soybean fields and leaf samples submitted by North Carolina Cooperative Extension Agents in an additional 15 counties. These samples also were assayed using a traditional PCR protocol and by the enzyme-linked immunosorbent assay protocol included in the EnviroLogix QualiPlate kit (Portland, ME) for soybean rust. Ten soybean specimens from 10 sites were confirmed positive by these methods. Disease was not found on three kudzu samples, although one kudzu sample was adjacent to a soybean field that was positive for P. pachyrhizi. Although soybean rust was eventually detected in 18 North Carolina counties in 2005, no soybean yield loss occurred since the pathogen was detected when more than 80% of the soybean crop was mature. To our knowledge, this is the first report of P. pachyrhizi in North Carolina and the northern most find on soybean in the continental United States in 2005.

References: (1) R. D. Frederick et al. Phytopathology 92:217, 2002. (2) R. W. Schneider et al. Plant Dis. 89:774 2005.
First Report of a Begomovirus Associated with Tomato Yellow Leaf Curl Disease in Ethiopia
Authors: Shih S. L. , Green S. K. , Tsai W. S. , Lee L. M. , Wang J. T. , Tesfaye A.
Published: May 2007

During December 2003, severe leaf yellowing, leaf curling, and stunting symptoms were observed in tomato (Lycopersicon esculentum) plantings in Melkassa (1,550 m above sea level), Ethiopia. Eleven symptomatic samples were collected and tested for the presence of a begomovirus using polymerase chain reaction (PCR) with the begomovirus-specific degenerate primer pair PAL1v1978/PAR1c715 (3). Samples were also tested for Cucumber mosaic virus (CMV), Potato virus Y (PVY), Tobacco etch virus (TEV), Pepper veinal mottle virus (PVMV), and Tomato mosaic virus (ToMV) using enzyme-linked immunosorbent assay (ELISA). All samples were negative for CMV, PVY, TEV, PVMV, and ToMV. However, the expected 1.4-kb PCR product for begomoviruses was obtained from all samples. DNA-B and DNA-beta were not detectable using PCR with the DNA-B specific primer pairs DNABLC1/DNABLV2 and DNABLC2/ DNABLV2 (2) and the DNA-beta primer pair Beta01/Beta02 (1), respectively. The 1.4-kb PCR product of one sample was cloned and sequenced. On the basis of the sequence of the 1.4-kb DNA product, specific primers were designed to complete the DNA-A sequence. The DNA-A consisted of 2,785 nucleotides (GenBank Accession No. DQ358913) and was found to contain the six predicted open reading frames (ORFs V1, V2, C1, C2, C3, and C4). A BLAST analysis was conducted with geminivirus sequences available in the GenBank database at the National Center for Biotechnology Information (Bethesda, MD), and DNAMAN software (Lynnon Corporation, Quebec, Canada) was used for further comparisons. The DNA-A sequence of the virus associated with yellow leaf curl disease of tomato from Ethiopia showed highest sequence identity (92%) with Tomato yellow leaf curl Mali virus (TYLCMLV; GenBank Accession No. AY502934). On the basis of the DNA-A sequence comparison and the ICTV demarcation of species at 89% sequence identity, the Ethiopian virus is a provisional strain of TYLCMLV described from Mali. To our knowledge, this is the first report of a begomovirus associated with tomato yellow leaf curl disease in Ethiopia.

References: (1) R. W. Briddon et al. Mol. Biotechnol. 20:315, 2002. (2) S. K. Green et al. Plant Dis. 85:1286, 2001. (3) M. R. Rojas et al. Plant Dis. 77:340, 1993.
Azoxystrobin Rate and Timing Effects on Rice Head Blast Incidence and Rice Grain and Milling Yields
Authors: Groth D. E.
Published: May 2007

Growing blast susceptible rice (Oryza sativa) cultivars often requires farmers to use fungicides to prevent significant reductions in rice grain and milling yields. Studies were conducted to determine the optimum rate and rice growth stage for single or multiple applications of azoxystrobin to control blast (Pyricularia grisea). Azoxystrobin was applied foliarly to naturally infected field plots in 2001 to 2005 at rates of 0.11, 0.17, and 0.22 kg a.i. ha-1 at boot (B) and heading (H) or only at H growth stages, and at 0.17 kg a.i. ha-1 at 5 (H+5), 10 (H+10), and 15 (H+15) days after H and B with low or high blast pressure. Head blast incidence (percent heads infected) was assessed 1 to 2 weeks before harvest. A fungicide application made at H, H+5, and B+H significantly reduced blast incidence with high and low disease pressure, resulting in significantly higher grain and head rice milling yields compared with unsprayed plots with high blast pressure. There were no significant effects of fungicide rate on blast development or yield following the H, B+H, and H+5 applications. With fungicide applications made at B, H+10, and H+15 days postheading, rice had higher disease incidence, resulting in lower grain and milling yields compared with rice receiving a heading application.