bluuebunny/crossref_metadata_2025 huggingface dataset:
Sclerotinia Root Rot: A New Threat to Buckwheat Seedlings in India
Authors: Mondal K. K. , Rana S. S. , Sood P.
Published: May 2007

In the temperate regions of India, buckwheat (Fagopyrum esculentum Moench and F. tataricum Gaertn.) is produced extensively. During the first week of June in 2001 and 2002, a severe incidence of root rot (35% seedling mortality) was observed in the Sangla Valley of Himachal Pradesh when the crop was at the seedling stage. The disease was more severe on F. tataricum, resulting in a poor crop stand. The disease appeared as water-soaked areas on the upper portion of the root, which turned brown. The brown patches gradually proceeded downward covering the whole root system. The above ground foliage wilted and died. The disease spread rapidly with cloudy, humid weather and day temperatures ranging from 15 to 20°C. Mycelium of the causal fungus was inter- and intracellular type with hyaline, branched, and septate hyphae. Sclerotia were pink but later turned black, measuring 3.0 to 3.5 mm in diameter. The pathogenicity of the causal fungus was proved following Koch's postulates. The pathogen was identified as Sclerotinia sclerotiorum (Lib.) de Bary (2). In Japan, the association of S. libertiana on buckwheat has been reported (1). To our knowledge, this is the first report of Sclerotinia root rot on buckwheat from India.

References: (1) H. Singh and T. A. Thomas. Indian Counc. Agric. Res. New Delhi, India, 1978. (2) H. J. Willets and J. A. L. Wong, Bot. Rev. 46:101,1980.
First Report of Acidovorax avenae subsp. citrulli as a Pathogen of Gramma in Australia
Authors: Martin H. L. , Horlock C. M.
Published: May 2007

In March 2001, a foliar bacterial disease was observed on gramma seedlings (Cucurbita moschata L.) cv. Ken Special Hybrid 864 in a commercial nursery in Bowen, north Queensland, Australia. Symptoms included chlorosis of cotyledons and angular, water-soaked lesions from the tips of the cotyledons to the petioles. Brown, angular, water-soaked lesions that were delimited by the leaf veins were also present on newly emerged true leaves. Streaming of bacterial cells from the edges of cut lesions was seen in a droplet of water with ×100 magnification. Isolations attempted on King's medium B consistently yielded a slow-growing, cream to white, gram-negative bacterium. Bacterium was identified as Acidovorax avenae subsp. citrulli based on carbon source utilization profiles (Biolog, Hayward CA) and polymerase chain reaction (PCR) using a primer pair based on the 16S-23S internal transcribed spacer region. When tested in rep-PCR with the BoxA1R primer (2), the isolate produced a banding pattern similar to other Australian A. avenae subsp. citrulli isolates previously shown to be pathogenic to rockmelon (1). Koch's postulates were completed with 20 2-week-old glasshouse-grown gramma (cv. Ken Special Hybrid 864) seedlings. Seedlings were misted until runoff with a 3 × 108 CFU/ml bacterial suspension and enclosed in plastic bags for 48 h at 23°C. Water-soaked lesions developed on cotyledons of all seedlings 6 days after inoculation, and bacterium was reisolated from symptomatic tissue. To our knowledge, this is the first report of A. avenae subsp. citrulli as a pathogen of C. moschata

References: (1) R. G. O'Brien and H. L. Martin. Aust. J. Exp. Agric. 39:479, 1999 (2) J. Versalovic et al. Methods Mol. Cell Biol. 5:25, 1994.
Transmission of Erwinia stewartii from Plants to Kernels and Reactions of Corn Hybrids to Stewart's Wilt
Authors: Michener P. M. , Pataky J. K. , White D. G.
Published: May 2007

Stewart's wilt reactions of 98 food-grade, white corn hybrids, 3 yellow dent corn hybrids, and 23 sweet corn hybrids and infection of kernels by E. stewartii were evaluated in 1998, 1999, and 2000. Stewart's wilt symptoms were rated from 1 (no appreciable spread of symptoms) to 9 (dead plants) following inoculation. The mean Stewart's wilt ratings for the food-grade, white corn and yellow dent corn hybrids were 1.9, 2.4, and 2.9 in 1998, 1999, and 2000, respectively. The mean Stewart's wilt ratings for the sweet corn hybrids were 3.8, 4.2, and 4.6 in 1998, 1999, and 2000, respectively. Hybrids with ratings less than 3 were classified as resistant. Hybrids with ratings between 3 and 4.5 were classified as moderate. Hybrids with ratings greater than 4.5 were classified as susceptible. Ears harvested from each row in 1998 and 1999 were assayed for E. stewartii using an enzyme-linked immunosorbent assay (ELISA)-based seed health test. Kernels from 16 hybrids were positive for E. stewartii in 1998. Kernels from 11 hybrids were positive for E. stewartii in 1999. Kernel infection by E. stewartii was affected considerably by the level of host resistance (i.e., reactions of seed parent plants). For hybrids classified as resistant, estimates of kernel infection were 0.024 and 0.0007% in 1998 and 1999, respectively. For hybrids with moderate reactions to Stewart's wilt, estimates of kernel infection were 0.19 and 0.07% in 1998 and 1999, respectively. For hybrids with susceptible reactions to Stewart's wilt, estimates of kernel infection were 11.6 and 7.8% in 1998 and 1999, respectively. Based on high levels of Stewart's wilt resistance in food-grade, white corn hybrids, and low rates of kernel infection by E. stewartii in resistant and moderate hybrids, there is an exceedingly low probability of introducing E. stewartii to areas where it does not occur by transmitting the bacterium in grain of the food-grade, white corn hybrids evaluated in this study. Although all of the kernels harvested in these experiments were produced as grain on open-pollinated F1 hybrids, the rates of kernel infection observed for hybrids with resistant, moderate and susceptible reactions to Stewart's wilt are applicable to seed produced on inbred lines with equivalent Stewart's wilt reactions.
First Report of a Distinct Begomovirus Infecting Cassava from Zanzibar
Authors: Maruthi M. N. , Colvin J. , Seal S. , Thresh J. M.
Published: May 2007

In 1998, cassava plants exhibiting extremely mild mosaic disease symptoms were collected from Uguja Island, Zanzibar. Total DNAs extracted from symptomatic leaves did not produce diagnostic PCR bands using primers specific to known Cassava mosaic viruses (genus Begomovirus, family Geminiviridae) (2). Degenerate primer pair A/B (1), however, produced a 564-nucleotide (nt) band in the common region of DNA-A to the conserved amino acid sequence CEGPCKYG within the coat protein gene for begomoviruses. Virus-specific primers were designed and the begomoviral genome was amplified and cloned to obtain the full-length DNA-A (2,785 nt) (AF422174) and the partial DNA-B (2,403 nt) (AF422175) component comprising the 5′ end of the BV1 open reading frame (ORF) to eight (A) of the conserved nanonucleotide TAATATTAC in the common region. Phylogenetic comparisons of DNA-A and -B sequences of the cassava begomivirus showed they were most closely related to East African cassava mosaic virus (EACMV) from Tanzania (Z83256, 83% identity) and Uganda (AF126805, 87% identity). Based on DNA-A and -B components, its closest relatives among African cassava mosaic virus strains were the Nigerian (X17095, 67% identity) and Ugandan (AF126800, 38% identity) isolates respectively. The number and arrangement of the viral ORF was identical to other bipartite begomoviruses from the Old World. Work is in progress to determine whether this begomovirus is a new strain of an existing EACMV or a new species.

References: (1) D. Deng et al. Ann. App. Biol. 125:327, 1994. (2) X. Zhou et al. J. Gen. Virol. 78:2101, 1997.
First Report of Puccinia polysora on Corn in Argentina
Authors: Hernández J. R. , Romero M. Yasem de , Díaz C. G. , Ramallo J. C.
Published: May 2007

Corn (Zea mays L.) is an important crop in northwest Argentina but acreage has declined over the last several years due to disease problems. During the 2000 to 2001 growing season, leaf diseases were observed on corn growing in northeastern Tucumán Province (Departamiento Leales), which resulted in yield losses. One of the most prevalent diseases was caused by a rust fungus that produced both uredinial and telial stages. At the time of flowering 32% of the leaf area was infected, and 3 weeks later 69% was infected. Three rust fungi are known from corn (2), and this fungus was identified as Puccinia polysora Underw. based on the morphology of the two types of sori and spores (1). Although known from most tropical and subtropical regions, to our knowledge, this is the first report of P. polysora in Argentina (voucher BPI 841342). Tucumán Province, where the disease was observed, is a subtropical region with temperatures during the growing season >24°C and a relative humidity >90%. P. polysora has not been observed in the Pampas Humedas, the corn belt of Argentina, possibly because the area is more temperate than northwest Argentina and therefore the environment is not conducive to disease development or perhaps P. polysora has not been introduced into the region.

References: (1) G. B. Cummins. The Rust Fungi of Cereals, Grasses and Bamboos. Springer-Verlag, New York, 1971. (2) J. K. Pataky. Rusts. Pages 35–38 in: Compendium of Corn Diseases, 3rd ed. The American Phytopathological Society, St. Paul, MN, 1999.
Calopogonium golden mosaic virus Identified in Phaseolus vulgaris from Western and Northern Regions of Costa Rica
Authors: Diaz M. , Maxwell D. P. , Karkashian J. P. , Ramírez P.
Published: May 2007

Bean golden yellow mosaic virus (BGYMV, GenBank Accession No. M91604) is reported to be the main bean-infecting (Phaseolus vulgaris) begomovirus in Central America (1,2). Another begomovirus, Bean calico mosaic virus (BCaMV, GenBank Accession No. AF110189), is known to infect P. vulgaris in central Mexico. Bean samples with the viral symptom of foliar chlorosis were collected in different regions of Costa Rica from 1994 to 2001. Total nucleic acids were extracted and tested using polymerase chain reaction (PCR) with degenerate primer pair PBL1v2039/PCRc2 for DNA-B, which can give a different fragment size for some begomoviruses (4). PCR fragments were obtained from 119 bean samples. Fifty samples from the central valley produced 600-bp PCR fragments, which is typical for BGYMV (4), and one sample produced two fragments (500 and 600 bp). One sample from western Costa Rica had a 550-bp fragment, and 69 samples from the western and northern regions produced 500-bp fragments. One of the latter samples (No. 01-1152) was selected for PCR with degenerate primer pairs PAL1v1978/PAR1c715 for DNA-A and PBL1v2039/PBR1v800 for DNA-B (4). The amplified PCR fragments were 1.35 and 1.4 kb for DNA-A and DNA-B, respectively. These are expected sizes for a Western Hemisphere begomovirus. The DNA-A fragment was cloned and sequenced (GenBank Accession No. AF439402). Sequence comparisons indicated that this uncharacterized begomovirus (No. 01-1152) had 98, 97, and 93% nucleotide identities with the rep gene, common region, and coat protein gene promoter of Calopogonium golden mosaic virus (CalGMV, GenBank Accession Nos. AF439748 and AF439749, respectively) (3). CalGMV had been isolated from a weed, Calopogonium sp., collected in 1991 near Quepos in the west and Tilaran in the north of Costa Rica (3). Phylogenetic analysis of the viral sequence of the begomovirus associated with No. 01-1152 placed it in the Squash leaf curl virus clade (1). BCaMV is also in this phylogenetic clade, but sequence comparisons between CalGMV and BCaMV had <90% nucleotide identity, and so are distinct species. CalGMV is the begomovirus associated with No. 01-1152, and this is an example of the movement of a weed-infecting begomovirus into an agricultural crop. Since this Calopogonium sp. is widespread in Central America, it is important to determine if CalGMV is present in beans in other regions. The data also indicate that BGYMV and CalGMV infect beans in two geographically distinct regions of Costa Rica.

References: (1) J. C. Faria et al. Phytopathology 84:321, 1994. (2) W. McLaughlin et al. Plant Dis. 78:1220, 1994. (3) M. R. Rojas et al. Annu. Rep. Bean Improv. Coop. 35:150, 1992. (4) M. R. Rojas et al. Plant Dis. 77:340, 1993.
Xanthomonas Leaf Spot and Stem Canker on Blueberry in Nurseries in Florida
Authors: Roberts P. D. , Saunders B. , Urs R. R. , Dickstein E. , Jones J. B.
Published: May 2007

In June and July 1998, in nurseries in south Florida, lesions were observed on the foliage and stems of three southern high-bush cultivars of blueberry hybrids (Vaccinium coryumbosum). Plants were approximately 1.5 to 2 years of age (0.6 to 1 m high). Disease incidence ranged from 95 to 50%, depending on cultivar. Lesions on leaves were roughly round, 5 to 20 mm in diameter, reddish brown surrounded by a yellow halo, and frequently coalesced to form large blighted areas. Stem cankers were soft, dark brown-to-black, and often resulted in the death of the entire branch. Microscopic examination of free-hand sections through lesion margins revealed bacterial streaming. Isolation of bacteria on nutrient agar consistently recovered mucoid, yellow bacteria typical of a xanthomonad. A pure culture of the bacteria was gram negative, oxidase negative, nonfluorescent, and proteolytic and produced a hypersensitive reaction on tobacco. Strains had fatty acid profiles with 88.5% similarity to Xanthomonas campestris pv. maniotis and 84.6% similarity to X. campestris pv. fici. Koch's postulates were fulfilled by spray-inoculation of 18-month-old blueberry cv. Sharpblue with a bacterial suspension (1 × 108 CFU/ml) in sterile water. Control plants were sprayed with sterile distilled water. Plants were covered with plastic for 24 h and kept in a growth chamber at 25°C with a 12-h photoperiod. Symptoms were reproduced on inoculated plants, and bacteria were reisolated from lesions. Control plants were asymptomatic. The disease was controlled by applications of copper compounds, increased plant spacing, rouging of infected plants, reduction of leaf wetness, and elimination of overhead irrigation.
Association of Mycotoxin and Sclerotia Production with Compatibility Groups in Aspergillus flavus from Peanut in Argentina
Authors: Novas M. Victoria , Cabral Daniel
Published: May 2007

Vegetative compatibility (VC) of Aspergillus flavus isolates from peanut seed was studied to evaluate preliminary diversity and its association with mycotoxin production and sclerotia production and number. A. parasiticus isolates also were included as a comparative group. Isolates were divided into five categories based on mycotoxin production combination. Five of the A. flavus isolates were considered atypical because they simultaneously produced aflatoxins B, G, and cyclopiazonic acid (CPA). Vegetative compatibility groups (VCGs) were determined through complementation tests between nitrate-nonutilizing mutants. Sclerotia diameters and the number of sclerotia produced per square centimeter were determined for each isolate. Out of 32 isolates of A. flavus, 25 combined in 13 VCGs, whereas the remaining could not be assigned to any particular group. Each VCG included isolates of the same mycotoxin category, with only one exception. Also, all isolates within the same VCG were characterized by their ability to produce or not produce sclerotia. Isolates between VCGs showed significant differences in number of sclerotia per square centimeter, but differences in sclerotia size were not evident. Atypical isolates simultaneously producing aflatoxins B, G, and CPA formed a single and exclusive VCG.
DNA Fingerprinting Analysis of Vegetative Compatibility Groups in Aspergillus flavus from a Peanut Field in Georgia
Authors: McAlpin C. E. , Wicklow D. T. , Horn B. W.
Published: May 2007

The ability of species-specific DNA probe pAF28 to correctly match 75 strains of Aspergillus flavus isolated from a peanut field in Georgia with 1 of 44 distinct vegetative compatibility groupings (VCGs) was assessed. Multiple strains belonging to the same VCG typically produced identical DNA fingerprints, with the exception of VCG 17 and VCG 24, which contained strains that showed 83 and 87% similarity, respectively. A. flavus isolates sharing more than 80% of the fragments are recognized as belonging to the same DNA fingerprint group. Each VCG represented by a single isolate produced unique DNA fingerprints. The results provide further evidence that the pAF28 probe is able to distinguish A. flavus VCGs based on DNA fingerprints and can be used to predict the approximate number of VCGs in a sample population. The DNA probe also hybridized strongly and displayed multiple and distinct bands with other species in Aspergillus section Flavi: A. bombycis, A. caelatus, A. nomius, A. pseudotamarii, and A. tamarii. Although individual strains representing Aspergillus spp. in section Flavi produced DNA fingerprints with multiple bands, the banding patterns could not be used to classify these strains according to species.
In Vitro Fungicidal Activity of Acidic Electrolyzed Oxidizing Water
Authors: Buck J. W. , van Iersel M. W. , Oetting R. D. , Hung Y.-C.
Published: May 2007

Acidic electrolyzed oxidizing (EO) water, generated by electrolysis of a dilute salt solution, recently gained attention in the food industry as a nonthermal method for microbial inactivation. Our objective was to determine if EO water has potential to control foliar diseases in greenhouses. Test fungi suspended in distilled water were combined with EO water (1:9 water:EO water) for various time periods, the EO water was neutralized, and germination was assessed after 24 h. Germination of all 22 fungal species tested was significantly reduced or prevented by EO water. All relatively thin-walled species (e.g., Botrytis, Monilinia) were killed by incubation times of 30 s or less. Thicker-walled, pigmented fungi (e.g., Curvularia, Helminthosporium) required 2 min or longer for germination to be reduced significantly. Dilution of EO water with tap water at ratios of 1:4 and 1:9 (EO:tap water) decreased efficacy against Botrytis cinerea. The presence of Triton X-100 (all concentrations) and Tween 20 (1 and 10%) eliminated the activity of EO water against B. cinerea. EO water did not damage geranium leaf tissue and inhibited lesion development by B. cinerea when applied up to 24 h postinoculation. EO water has a wide fungicidal activity which could facilitate its use as a contact fungicide on aerial plant surfaces and for general sanitation in the greenhouse.
First Report of Nectria haematococca Causing Wilt of Olive Plants in Argentina
Authors: Babbitt S. , Gally M. , Pérez B. A. , Barreto D.
Published: May 2007

Death of 8- to 12-month-old olive plants (Olea europaea L. ‘Arbequina’, ‘Arauco’, and ‘Picual’) has been observed since 1998 in northwestern Argentina. No mycelium or perithecium was observed when examining rotting roots of greenhouse-collected plants. Root segments of diseased plants were plated on potato dextrose agar. Cultures developed a white mycelium after 2 to 3 days, producing microconidia, macroconidia, and chlamydospores identified as Fusarium solani (1). After 15 days of incubation at 23 ± 2°C, reddish perithecia developed infrequently on root segments and adjacent substratum. Single-septate ascospores were hyaline and turned light brown with longitudinal striations at maturity. Microscopic measurements agreed with Nectria haematococca (1). To conduct Koch's postulates (two experiments, two treatments including inoculated and controls, 10 replicates per treatment), young rooted cuttings (6- to 12-month-old) were transferred to pots with a soilless mix and F. solani-colonized oat grains (10:1 vol/vol) and placed in growth chamber (25 to 28°C). First symptoms of the disease were leaf drooping and apex bending after 5 days. At approximately 9 days, leaves turned brownish, developed wilting from the tip downward, and plant death. Controls remained healthy. The fungus was reisolated, and perithecia of N. haematococca developed. F. solani has been reported causing wilt and sudden death in olive previously (2,3). To our knowledge, this is the first report of perithecial development associated with F. solani on olive.

References: (1) C. Booth. The Genus Fusarium. CAB International, Wallingford, UK, 1971. (2) R. L. Munjal et al. Studies on diseases of olive in himachal pradesh. Pages 437–440 In: Improvement of Forest Biomass. Symposium Proceedings. Indian Society of Tree Scientists. P. K. Kosla, ed. Sdan, India, 1982. (3) B. A. Pérez et al. (Abstr.) Phytopathology 91 (suppl):S71, 2001.
First Report of Phytophthora cryptogea in Walnut Stands in Italy
Authors: Vettraino A. M. , Belisario A. , Maccaroni M. , Anselmi N. , Vannini A.
Published: May 2007

English (Persian) walnut (Juglans regia L.) is among the most widely cultivated species in pure and mixed plantations of broadleaved trees in Italy. A decline of walnut of increasing occurrence has been reported recently in new plantations in central and northern Italy. Symptoms of the decline were typically characterized by yellowing of the foliage, defoliation, and plant death. Dark, flame-shaped necroses were often present at the collar. Phytophthora cactorum, P. cambivora, and P. cinnamomi were among the species associated with necrotic tissues of the collar and main roots (1). Furthermore, a Phytophthora sp. was isolated from soil removed from the lateral root zone of 6 of 15 declining trees in 3 walnut plantations, 2 in northern Italy and 1 in central Italy. Isolations were made by baiting with Rhododendron leaves and plating on PARBhy selective medium (3). The species isolated was identified as P. cryptogea on the basis of morphological and cultural characteristics (2). All isolates produced oval to obpyriform, nonpapillate sporangia and were mating type A2. Identification of the isolates was confirmed by comparing the restriction fragment length polymorphism patterns of the internal transcribed spacer region of ribosomal DNA with those obtained from previously identified Phytophthora species. Pathogenicity tests on potted 2-year-old walnut seedlings were conducted using two isolates of P. cryptogea. Inoculum was prepared by growing isolates on sterilized millet seeds added to soil at 2.5% (wt/vol). Sporulation was induced by 24-h flooding of the soil. Symptoms were assessed 1 month after inoculation. Ten uninoculated seedlings were used as controls. Inoculated seedlings showed no symptoms on the tap root, but there were extensive necroses of lateral roots ranging from 14 to 75% (average 38.6 ± 6.7 SE) of total lateral root (dry weight) compared with values of 0 to 11% (average 3 ± 1.5 SE) for uninoculated seedlings. P. cryptogea was easily reisolated from infected lateral roots and from the soil of inoculated pots. The inoculation trials confirmed P. cryptogea as a feeder-root pathogen of walnut in Italy. To our knowledge, this is the first report of P. cryptogea on English walnut in Italy. This species often has been associated with walnut decline in the United States (2) and on other woody plants in Italy (3).

References: (1) A. Belisario et al. Petria 11:127, 2001. (2) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Association, St. Paul, MN, 1996. (3) A. M. Vettraino et al. Plant Pathol. 50:90, 2001.
First Report of Citrus tristeza virus in Greece
Authors: Dimou D. , Drossopoulou J. , Moschos E. , Varveri C. , Bem F.
Published: May 2007

Large-scale surveys of Citrus spp. for the presence of Citrus tristeza virus (CTV) by the Ministry of Agriculture in Greece began in 1995. Over 26,000 trees have been tested by enzyme-linked immunosorbent assay and immunoprinting (2). In summer 2000, the first CTV-infected sweet orange cv. Lane Late tree grafted on CTV-tolerant Carrizo citrange was found in Argolis County, Peloponnese. This tree belonged to a batch of CAC propagation material (20 trees) illegally introduced from Spain in 1994, which was subsequently traced and found to be infected (45%). A follow-up search of trees grafted with the above material was undertaken in the two concerned regions (Argolis and Chania-Crete), and more than 3,500 trees have been removed. Extensive surveys continue to identify and destroy new infections. Few cases (15 of 16,800) of natural transmission to cultivars other than cv. Lane Late have been found. All of these have been close to the initially infected trees in the Argolis area. Surveys in spring 2001 were extended to certified propagation material of Clemenpons mandarin on Carrizo citrange imported from Spain, and 7 of 1,038 plants were infected (0.64%). The virus was successfully graft-transmitted to sweet orange cv. Madame Vinous and sweet lime seedlings, where it was identified by immunoprinting and reverse transcription-polymerase chain reaction (1). Mild vein clearing symptoms appeared on both indicators. Vein clearing on sweet lime was also accompanied by leaf cupping. To our knowledge, this is the first report of CTV in Greece.

References: (1) A. Sambade et al. J. Virol. Methods 87:25, 2000. (2) C. Vela et al. J. Gen. Virol. 67:91, 1986.
First Report of an Aster Yellows Subgroup 16SrI-B Phytoplasma Infecting Chayote in Costa Rica
Authors: Villalobos W. , Moreira L. , Rivera C. , Bottner K. D. , Lee I.-M.
Published: May 2007

An outbreak of a witches' broom disease affected approximately 20% of plants in several chayote (Sechium edule (Jacq.) Schwartz) fields in the commercial production area of the Ujarrás Valley, Cartago Province, Costa Rica during 2000 and 2001. Affected chayote plants exhibited symptoms, including basal proliferation with severe foliage reduction, aborted flowers, and deformed fruits, suggestive of phytoplasmal infection. Two other symptomatic cucurbit species growing near the chayote fields were also identified. These species were tacaco plants (S. tacaco (Pitt.) C. Jeffrey), an edible cucurbit for domestic marketing in Costa Rica, showing severe size reduction of leaves and fruits, and Rytidostylis carthaginensis (Jacq.) Kuntze, a weed in chayote and tacaco fields, exhibiting abnormal tendril proliferation. Plants were analyzed for phytoplasma infection by a nested polymerase chain reaction (PCR) assay, using the universal rRNA primer pair P1/P7 followed by R16F2n/R16R2 (2). Phytoplasmas were detected in all symptomatic samples (18 chayote, 6 tacaco, and 3 weed) tested but were undetectable in all asymptomatic samples (10 chayote, 6 tacaco, and 2 weed). Restriction fragment length polymorphism (RFLP) analysis of PCR products (16S rDNA sequences) by separate digestion with eight restriction enzymes (RsaI, HhaI, KpnI, BfaI, HaeIII, HpaII, AluI, MseI) revealed that a phytoplasma belonging to subgroup 16SrI-B in the aster yellows phytoplasma group (16SrI) was associated with chayote witches' broom (CWB). The same or very similar phytoplasmas were found in both symptomatic tacaco and R. carthaginensis plants. Phylogenetic analysis of 16SrDNA sequences also confirmed the CWB phytoplasma to be most similar to members of subgroup 16SrI-B. Similar diseases in chayote and other cucurbits have been reported in Brazil (3), Taiwan (1), and Mexico (4). The CWB phytoplasma differs from the phytoplasma (16SrIII-J subgroup) associated with chayote in Brazil. The identities of phytoplasmas associated with cucurbits in Taiwan and Mexico are unknown. The occurrence of an aster yellows group phytoplasma in chayote may pose a potential threat to continued production and exportation of this cash crop. To our knowledge, this is the first report of 16SrI-B subgroup phytoplasmas in naturally infected cucurbits in Costa Rica.

References: (1) T. G. Chou et al. Plant Dis. Rep. 60:378, 1976. (2) I.-M. Lee et al. Int. J. Syst. Bacteriol. 48:1153, 1998. (3) H. G. Montano et al. Plant Dis. 84:429, 2000. (4) E. Olivas. Rev. Fitopatol. (Lima) 13:14, 1978.
First Report of Phytoplasmas Infecting Watercress in Hawaii
Authors: Borth W. B. , Hamasaki R. T. , Ogata D. , Fukuda S. K. , Hu J. S.
Published: May 2007

Symptoms of leaf yellowing, reduced leaf size, and witches'-brooms have recently been observed affecting watercress (Nasturtium microphyllum Boen. × Rcbh.) in Hawaii. These symptoms are followed by the collapse of affected plants. This condition has led to 80 to 90% losses for one of the largest watercress farms on Oahu and is now affecting other watercress farms in the area. Nutritional deficiencies or toxicities, water salinity, and insect or mite feeding damage were investigated but could not be implicated in the etiology of this syndrome. Eighteen watercress plants with early yellowing or advanced symptoms and nine symptomless plants were analyzed for phytoplasma infection using polymerase chain reaction (PCR) assays with primer pairs P1/Tint or P1/P7 (4). Amplicons of the expected sizes were produced from all symptomatic plants, whereas no products were amplified from symptomless plants. Sequence analysis of the cloned PCR products confirmed their phytoplasma origin and indicated that the watercress was infected with a phytoplasma most similar to SAY (2), a severe strain of western aster yellows phytoplasma previously classified as a 16SrI-B group member (3). Leafhoppers collected from an affected watercress planting have been identified as the aster leafhopper (Macrosteles quadrilineatus Fbs.) This species is the most efficient vector of the aster yellows phytoplasma and had not been previously recorded in Hawaii. The only other phytoplasma disease known in Hawaii prior to this report is Dodonaea yellows (1), which affects one of the most common native plants (Dodonaea viscosa (L.) Jacq.) in dry upland forests on all the islands. Dodonaea yellows, however, has been attributed to an X-disease (16SrIII) group phytoplasma. The occurrence of an aster yellows group phytoplasma in watercress, a previously unrecorded host, and the presence of a very efficient vector, M. quadrilineatus, poses a serious threat to the production of other vegetable and floral crops in Hawaii.

References: (1) W. Borth et al. Plant Dis. 79:1094, 1995. (2) C. Kuske and B. Kirkpatrick. Int. J. Syst. Bacteriol. 42:226, 1992. (3) I.-M. Lee et al. Int. J. Syst. Bacteriol. 48:1153, 1998. (4) C. Smart et al. Appl. Environ. Microbiol. 62:2988, 1996.
Virulence of Blumeria graminis f. sp. tritici Populations in Morocco
Authors: Imani Yasmina , Ouassou Abdallah , Griffey Carl A.
Published: May 2007

The incidence and severity of powdery mildew, caused by Blumeria graminis f. sp. tritici, have increased in Morocco during the past decade as a result of the introduction and intensive production of a few semidwarf cultivars of bread wheat (Triticum aestivum) and durum wheat (Triticum turgidum) that are genetically uniform, and the increased utilization of nitrogen fertilizers and irrigation. The virulence of the pathogen population has not been characterized in Morocco, and little is known about the spectra and distribution of virulence in B. graminis populations. Such knowledge will facilitate the identification and utilization of effective resistance genes in cultivar development and deployment. Isolates of B. graminis collected in 1999 and 2000 from three Moroccan wheat production areas were analyzed for virulence using a host differential series comprised of 13 known genes conferring resistance to powdery mildew. Segments of primary leaves from 12-day-old seedlings of the wheat differentials were inoculated with isolates of B. graminis derived from a single pustule. Powdery mildew reactions were assessed on a 0 to 9 scale 12 days after inoculation. Virulence frequencies, complexity, and racial composition of the pathogen population were determined. Data were analyzed for associations among pairs and triplets of virulence genes and for distribution of virulence genes among pathotypes. High frequencies of virulence to genes Pm1, Pm3c, Pm3f, Pm4a, pm5, and Pm7 were found over both years and across all three regions. Frequencies of virulence for Pm17 and Pm2 were intermediate, while virulence frequencies for Pm3a, Pm3b, Pm3d, and Pm4b were low. Virulence to Pm8 increased to high levels, while virulence to Pm4a decreased across the area surveyed from 1999 to 2000. The random distribution of virulence genes among patho-types indicates that sexual reproduction contributes to the variability of the pathogen. The Moroccan population of Blumeria graminis f. sp. tritici is composed of complex and highly variable pathotypes (87% of the isolates had five or more virulence genes), and strategies for deployment of resistance genes should take into account this complexity.
Phlyctema vagabunda Isolated from Coin Canker of Ash Trees in Michigan
Authors: Rossman A. Y. , Castlebury L. A. , Adams G. C. , Putnam M. L.
Published: May 2007

The coelomycetous fungus Phlyctema vagabunda Desm. (teleomorph Neofabraea alba (E.J. Guthrie) Verkley, synonym Pezicula alba E.J. Guthrie) is associated with a serious canker disease of cultivated ash trees in Michigan. Four- to five-year-old trees of Fraxinus americana cv. Autumn Purple and F. pennsylvanica cvs. Champ Tree, Cimmaron, and Urbanite had cankers that were smooth, round, brownish yellow, approximately 2 to 4 cm in diameter with distinct reddish, cracked margins. Immersed, eventually erumpent, unilocular acervuli developed in the central portions of these cankers. The same fungus was isolated both from the conidia as well as from the margin of the canker. The internal transcribed spacer (ITS) (AY064704) and beta-tubulin (AY064702) sequences were identical to sequences identified in GenBank as Pezicula alba from apple (1), and the morphology was consistent with Phlyctema vagabunda as well (2). P. vagabunda has been studied primarily as the cause of Bull's eye canker of apple (1). P. vagabunda under its numerous synonyms has been reported on various hardwood and herbaceous hosts from temperate regions around the world, including the United States. However, it has not been reported previously on species of Fraxinus. A specimen and culture from the ash cankers in Michigan have been deposited (BPI 841384 and CBS 109875).

References: (1) S. N. De Jong et al. Mycol. Res. 105:658, 2001. (2) B. C. Sutton. The Coelomycetes. CMI, Kew, Surrey, UK, 1980.
First Report of Bacterial Fruit Blotch of Watermelon Caused by Acidovorax avenae subsp. citrulli in Illinois
Authors: Babadoost M. , Pataky N.
Published: May 2007

In August 2001, symptomatic mature fruit of watermelon (Citrullus lanatus) cvs. Crimson Sweet and Royal Sweet were collected from six fields (48 ha) in Iroquois, Kankakee, and Mason counties in Illinois. The fruit surface had dark green, water-soaked lesions, and the rind's epidermis was cracked. Sections of infected rind were examined with a light microscope, and bacterial streaming was observed. Rind tissue was disinfested by rubbing the fruit surface with a paper towel moistened with 70% ethanol. Pieces of rind from the margins of lesions were placed in a test tube containing sterile-distilled water. The tube was shaken, and the suspension was streaked on King's medium B agar in petri plates. The plates were incubated at 26°C for 3 days. A nonfluorescent, gramnegative, anaerobic, oxidase-positive, rod-shaped bacterium was isolated that produced creamy white colonies on nutrient agar. The bacterium was identified as Acidovorax avenae subsp. citrulli based on an enzyme-linked immunosorbent assay test specific for A. avenae subsp. citrulli (kit PSA 14,800; Agdia Inc., Elkhart, IN). The disease was diagnosed as bacterial fruit blotch (1,2). The occurrence of bacterial fruit blotch of watermelon in Illinois is important because (i) watermelon is widely grown in Illinois, (ii) the pathogen also infects melons and pumpkins, and (iii) Illinois grows approximately 1,000 ha of melons and 8,000 ha of pumpkins.

References: (1) R. X. Latin. Bacterial fruit blotch. Pages 34-35 in: Compendium of Cucurbit Diseases. The American Phytopathological Society, St. Paul, MN,1996. (2) G. S. Somodi et al. Plant Dis. 75:1053, 1991.
Potential Beetle Vectors of Sirococcus clavigignenti-juglandacearum on Butternut
Authors: Halik S. , Bergdahl D. R.
Published: May 2007

To identify potential beetle (Coleoptera) vectors of the butternut canker fungus (Sirococcus clavigignenti-juglandacearum), beetles were collected from butternut (Juglans cinerea) trees and freshly cut logs and branches in Vermont from 1997 through 1999. At least 17 species of beetles, representing eight families, were found to carry conidia of the pathogen. Species most commonly collected and most frequently carrying the fungus were Acoptus suturalis (Curculionidae), Astylopsis macula (Cerambycidae), Eubulus parochus (Curculionidae), and Hyperplatys maculata (Cerambycidae). In 1999, 64, 74, 37, and 52% of these species, respectively, were carrying conidia. These beetles were often collected from dead butternut stems and branches upon which the fungus was fruiting and were less frequently found in crowns of living butternut trees. The butternut curculio (Conotrachelus juglandis) (Curculionidae) was found creating feeding and oviposition wounds on new shoots in crowns of butternut trees. Six to eleven percent of curculios collected carried the fungus. Species of Nitidulidae were observed crawling on logs or burrowing into cankers and curculio wounds. Six to seven percent of the nitidulids, Cryptarcha ampla and Glischrochilus sanguinolentus, carried conidia in 1999, and 31% of G. vittatus carried the fungus in 1998. Additional study is necessary to learn how consistently any of these beetles move from diseased to healthy tissue of butternut and vector conidia of S. clavigignenti-juglandacearum.
Tomato yellow leaf curl virus Resistant Tomatoes Show Resistance to Tomato curly stunt virus
Authors: Pietersen Gerhard , Smith Marie F.
Published: May 2007

A new disease of tomatoes (Lycopersicon esculentum) in South Africa has caused severe yield losses. The causative virus, Tomato curly stunt virus (ToCSV) is distantly related to Tomato yellow leaf curl virus (TYLCV). Thirty-two tomato accessions resistant to TYLCV and 8 local cultivars were assessed for their responses to ToCSV infection. Natural infection in a field trial and a screen-house trial with controlled ToCSV-inoculation were conducted. Symptoms were rated using a severity index (SI). Yield parameters were determined in the screenhouse trial to support SI evaluations. Average SI's obtained demonstrate that TYLCV-tolerant tomato accessions, with a few exceptions, have milder symptoms of ToCSV infection than TYLCV-susceptible, sensitive accessions. None of the accessions were immune, with some virus detected in all plants. Yield losses due to ToCSV infection of TYLCV-tolerant tomato accessions were not significant (P > 0.10) with some exceptions. However, TYLCV-sensitive accessions and 8 local cultivars had significant (P < 0.10) yield losses of 49 to 100%. TYLCV-tolerant cultivars may be useful for control of ToCSV, but require evaluation prior to release or use in breeding programs in South Africa.
First Report of Black Branch Dieback of Cashew Caused by Lasiodiplodia theobromae in Brazil
Authors: Cardoso J. E. , Vidal J. C. , Santos A. A. dos , Freire F. C. O. , Viana F. M. P.
Published: May 2007

Cashew nut (Anacardium occidentale) is one of the most important cash crops of northeastern Brazil. A new disease, named here as black branch dieback, caused by Lasiodiplodia theobromae, was observed causing serious damage on as many as 30% of the trees in some orchards in both coastal and inland semiarid cashew-growing areas of Ceará and Piauí states of Brazil, respectively. The disease symptoms are first observed as darkened, elongated lesions on stems near the branch apexes of herbaceous tissues. Gum exudation is common from lesions, which expand rapidly to affect the entire branch, leading to branch death. Diseased plants were collected, and L. theobromae was consistently isolated from canker tissues. Fresh mycelial disks of the fungus were used for artificial inoculation of healthy plants. Shoots of young cashew plants were inoculated on the apex by inserting a 3-mm plug taken from actively growing colonies on potato dextrose agar into an incision made with a sterile scalpel. Agar plugs with no mycelium were placed into incised plant shoots to serve as controls. Plants were incubated in a greenhouse at 28°C. Symptoms developed within 15 days after inoculation. Artificially inoculated plants showed symptoms similar to those that were naturally infected. L. theobromae was consistently reisolated from inoculated plants. The disease seems to occur throughout the year, but it spreads faster during the rainy season. A contagious disease pattern within the orchard was observed with a decreasing gradient from the orchard perimeter to the interior of the field, suggesting an external source of primary inoculum. All improved dwarf cashew clones were susceptible, but the newly released clone END-189 was the most susceptible. Black branch dieback may reduce tree growth, nut yield, and eventually cause plant death. Plant susceptibility is not related to its age however; only herbaceous tissues are vulnerable to natural infection. A similar disease on floral shoots of cashew caused by L. theobromae was reported by Olunloyo and Esuruoso in Nigeria (1). To our knowledge, this is the first report of L. theobromae causing branch dieback in cashew orchards in Brazil.

Reference: (1) O. A. Olunloyo and O. F. Esuruoso. Plant Dis. 59:176, 1975.
Aphanomyces euteiches Race 2 in Central Illinois Alfalfa Fields
Authors: Malvick D.
Published: May 2007

Approximately 260,000 ha of alfalfa is grown in Illinois. Two soil samples were collected randomly from slowly drained thin patches in each of four established alfalfa fields near Urbana in 2001. Plants in the thin patches were asymptomatic. Aphanomyces euteiches Drechs. was baited from the soil with cv. Saranac alfalfa seedlings and was isolated from 3- to 4-week-old infected seedlings using a medium containing metalaxyl and benomyl (1,2). It is difficult to isolate A. euteiches from field-grown roots. One to seven isolates were obtained per field, and all were identified as A. euteiches based on morphology (1,2). A. euteiches (races R1 and R2) causes root rot of alfalfa in slowly drained fields in Iowa, Kentucky, and Wisconsin (1,2). The race of 13 isolates was determined in tests repeated once with alfalfa populations Saranac (susceptible to R1 and R2), WAPH-1 (resistant only to R1), and WAPH-5 (resistant to R1 and R2) (1). Twelve 7-day-old seedlings in each of three pots per population were inoculated with 103 zoospores per seedling in a growth chamber (25°C). A disease index (DI) was determined 12 days later by scoring plants on a 1 to 5 scale, where 5 is a dead plant (1). Race was based on DI, R1: DI ≥3 for Saranac and <3 for WAPH-1, and R2: DI > 3 for Saranac and WAPH-1. The DI was 1.0 for noninoculated plants. All isolates were R2; the DI was >3.0 for inoculated Saranac and WAPH-1 and <3.0 for WAPH-5. To our knowledge, this is the first report of A. euteiches races in Illinois, and this pathogen was reported previously only from northwest Illinois. Control of Aphanomyces root rot is based on resistance; however, few alfalfa cultivars are resistant to R2.

References: (1) D. Malvick and C. Grau. Plant Dis. 85:740, 2001. (2) G. Munkvold and W. Carlton. Plant Dis. 79:1251,1995.
First Report of Pycnostysanus azaleae on Rhododendron in Italy
Authors: Garibaldi A. , Gilardi G. , Bertetti D. , Gullino M. L.
Published: May 2007

Rhododendron species cultivation has a long history in northern Italy, where a wide selection of cultivars and hybrids is grown. In spring 2001, a previously unknown bud blast was observed on several rhododendron cultivars growing in gardens and parks in the Province of Biella, Italy. Flower petioles and twigs, but not leaves, showed extensive necrosis, and flower production was reduced. The first symptoms on infected flower buds are brown necrotic areas near the base, which increase in size until the whole bud appears brown and water-soaked. Infected buds shrink, but do not rot or disintegrate, and remain on the bush. Coremia (2.0 mm high and 0.5 mm wide), which appeared as black specks on outer bud scales, produced large numbers of spherical spores apically that measured 3.6 to 5.5 μm in diameter. The fungus Pycnostysanus azaleae (1) was consistently isolated after disinfested infected buds (1 min in 5.15% commercial NaOCl solution) were cultured on potato dextrose agar amended with streptomycin sulfate at 100 mg/liter. Pathogenicity of three isolates of P. azaleae was confirmed by inoculating with a spore suspension 30 buds of 2 rhododendron plants (cv. Rosso scuro grande tardiva) grown in containers (14 cm diameter). Buds were punctured with a sterile needle before inoculation. Noninoculated plants served as controls. Wounded buds were covered with plastic bags to maintain high relative humidity, and all plants were maintained in growth chambers at 20°C for 9 days, and then transferred outdoors where temperatures were 20 to 25°C. Inoculated plants developed typical bud symptoms 20 days after inoculation, with 80% of inoculated buds showing symptoms. Control plants remained symptomless. The pathogen was consistently reisolated from artificially inoculated plants. In garden observations, different cultivars showed a wide range of susceptibility to the pathogen, mainly related to their flowering period. To our knowledge, this is the first report of the presence of P. azaleae in Italy. Outbreaks of P. azaleae were previously reported in the United States (1), United Kingdom (2), and Germany (3).

References: (1) W. H. Davis. Phytopathology 29:517, 1939. (2) P. J. Howell and R. K. S. Wood. Ann. Appl. Biol. 50:723, 1962. (3) W. Schmalscheidt. Immergrune Blater 26:35, 1985.
First Report of Xanthomonas axonopodis Infecting Agapanthus in Florida
Authors: Norman D. J. , Henny R. J. , Yuen J. M. F. , Dickstein E. R.
Published: May 2007

Agapanthus praecox subsp. orientalis, commonly called African lily or lily-of-the-Nile, bears large, round, blue or white flowers above attractive dark green foliage. Because of these horticultural features, this member of the family Liliaceae, has become a popular perennial bedding plant. For the past 2 years during warm wet periods, symptoms of chlorotic, water-soaked, leaf-streaks have been observed on agapanthus production in Florida. Round butyrus, bright yellow colonies were consistently isolated on nutrient agar. Bacteria were characterized as gram negative, catalase positive, motile, strictly aerobic, and not hydrolytic on starch. Using fatty acid analysis (FAME) and the MIDI Microbial Identification System with software version TSBA 3.90 (Microbial ID, Inc., Newark DE), three strains were further characterized and identified as Xanthomonas axonopodis with similarity coefficients to X. axonopodis pv. dieffenbachiae (0.907, 0.915, and 0.944) and to X. axonopodis pv. poinsetticola (0.912, 0.922, and 0.916). The three isolates were each inoculated on three plants each of agapanthus cv. Blue African lily, Dieffenbachiae maculata cv. Camille, and poinsettia, Euphorbia pulcherrima cv. PeterStar Red. Plants were sprayed with a suspension of each isolate at 1 × 108 CFU/ml, bagged for 24 h to raise humidity, and placed in a glasshouse for symptom development. Strains of X. axonopodis pv. poinsetticola (NZTCC 5779) and X. axonopodis pv. dieffenbachiae (X1718) were used as positive controls. Within 3 weeks, isolates from agapanthus produced leaf streaks on agapanthus plants, small, scattered, water-soaked lesions on dieffenbachia leaves, and no symptoms on poinsettia. No symptoms developed on the agapanthus plants when inoculated with either control strain. Both control strains formed lesions on leaves of their original host species. Xanthomonas was reisolated from treatments with symptomatic leaves. Plant inoculations were repeated with similar results. Although the agapanthus isolates were highly similar in FAME profiles to X. axonopodis pv. dieffenbachiae, symptoms produced on dieffenbachia were mild as compared with those produced by the dieffenbachia isolate. Therefore, these isolates may represent a distinct pathovar.