bluuebunny/crossref_metadata_2025 huggingface dataset:
First Report of Fusarium solani Causing Stunt on Lisianthus
Authors: Wolcan S. , Lori G. , Ronco L.
Published: May 2007

Fusarium solani Mart. (Sacc.) is the causal agent of stem rot and damping-off of lisianthus (Eustoma grandiflorum (Raf.) Shinn.) (1). Since the end of the 1980s, when this flower crop was introduced in Argentina, it has been affected by a basal stem rot (2). A previously undescribed disease was observed in 100% of the greenhouses in the Buenos Aires Province that grow lisianthus. Symptoms that developed after seedlings were transplanted included stunting, shortened internodes with reduced stem diameter, and small narrow leaves that were a dull green color. Some affected plants turned yellow-brownish and died 2 to 3 months after transplanting. Other plants recovered but produced low quality flowers later than normal. A third group of plants remained stunted (5 to 10 cm high) until the last flower harvest (about 8 to 10 months). F. solani was consistently isolated from basal stems and roots of diseased plants. For pathogenicity tests, inoculum was produced by culturing the fungus for 10 days in petri dishes containing sterile moistened rice. Inoculum was air dried, crushed, and mixed with soil that had been autoclaved at 112°C for 40 min on each of two consecutive days. The propagules in the soil were estimated by soil plate dilutions on the Nash & Snyder-PCNB medium at a ratio of about 104 CFU/g soil. Twenty plants of each cultivar Echo White and Echo Blue, whose roots had been pruned, were planted in both infested and noninfested soil. After about 40 days, stunting was observed in 85% of the inoculated plants, while controls remained asymptomatic. F. solani was reisolated from symptomatic plants, thus fulfilling Koch's postulates. A test also was conducted in a commercial greenhouse that produced lisianthus for several years, in which healthy plants were planted in three plots fumigated with methyl bromide and in three nonfumigated plots. The mean cfu/g soil of F. solani in the methyl-bromide treated plots was 5 × 102 and 1.6 × 104 CFU/g in the nontreated plot. After 120 days, the incidence of stunting in the treated plots was 0.6 and about 88% in the control plots. F. solani was recovered from symptomatic plants. Because disinfestation of soil is generally practiced in flower production, stunted plants are limited and can be confused with root problems. This is the first report of F. solani causing stunt on lisianthus.

References: (1) J. J. Taubenhaus and W. N. Ezekiel. Phytopathology 24:19, 1934. (2) S. M. Wolcan and G. A. Lori. Invest. Agr. Prot. Veg. 11:465, 1996.
Geographic and Host Range of Meloidogyne spp. in North Central Mexico
Authors: Velásquez-Valle R.
Published: May 2007

A disease survey carried out in 1998, 1999, and 2000 in the states of Aguascalientes, San Luis Potosí, and Zacatecas revealed the dispersal of Meloidogyne spp in this region of Mexico. Pepper (Capsicum annuum L.) Mirasol type plants showing general chlorosis, root rot, and galls were observed in central Zacatecas and western San Luis Potosí. Dry bean (Phaseolus vulgaris L.) plants (Landrace Flor de Mayo) collected in western San Luis Potosí and Aguascalientes also showed root galls. Roots of squash (Cucurbita spp) and sunflower (Helianthus annuus L.) plants that showed galled roots were found under dryland conditions in northern Zacatecas. Nursery peach (Prunus persica L.) plantlets with no foliar symptoms but showing severe root galling were detected in Zacatecas. Perineal patterns of Meloidogyne females obtained from those galled roots were coincident with those of M. incognita according to pictoral keys (1). This is the first report of M. incognita affecting these hosts in that region of the country. Alfalfa (Medicago sativa) plants collected in Aguascalientes showed galls caused by Meloidogyne spp; this is the first report of this nematode affecting alfalfa in the state. Volunteer onion (Allium cepa L., ‘Grano Blanco’) plants growing in a squash field in eastern Zacatecas had galled roots; a few Meloidogyne spp. females were obtained from small galls. This is the first report of the root-knot nematode affecting onion plants in north central México. Onion is known to be a host for several species of this nematode (2). Stunted, chlorotic squash plants had roots severely galled by Meloidogyne spp, but pepper crops growing in the same field in previous years showed general chlorosis, reduced size, and poor yield did not have root galls.

References: (1) Eisenback, J. D., et al. 1983. Guia para la identificación de las cuatro especiales más comunes del nematodo agallador (Meloidogyne spp.) con una clave pictorica. International Meloidogyne Project, Raleigh, NC. (2) Schwartz, H. F., and Mohan, S. K. 1995. Compendium of onion and garlic diseases. American Phytopathological Society. St. Paul. MN.
First Report of Nectria haematococca Stem Girdling of Greenhouse Peppers in Florida
Authors: Lamb E. , Rosskopf E. , Sonoda R. M.
Published: May 2007

Nectria haematococca Berk. & Broome causing stem girdling of three cultivars of greenhouse pepper, Capsicum annuum (cvs. Kelvin, Cubico, and Grizzly), was found for the first time in a single greenhouse in south Florida in March 1999. Approximately 10% of the plants were affected at first report increasing to over 40% within 3 months. Black lesions occurred at nodes where the plant was pruned or where fruit had been harvested. No mycelium or perithecia were noted in association with the lesions. All tissue above a lesion appeared normal until the lesion girdled the stem, causing the tissue above the lesion to wilt and die. The plant appeared unaffected below the lesion. The pathogen was isolated on half-strength Difco potato-dextrose agar (½ DPDA). Reddish perithecia developed readily in culture. Two single spore isolates of the pathogen obtained from two naturally infected plants (cultivar Kelvin) were used to satisfy Koch's postulates. Five plants of Kelvin were inoculated with each isolate by inserting a 4-mm agar block of the pathogen grown for 5 days on ½ DPDA into the stem. Five plants of the same cultivar were similarly treated with fungus-free ½ DPDA. Plants were grown under greenhouse conditions after inoculation. In four plants, black lesions similar to those seen in the commercial greenhouse developed within 1 week. In one plant, the portions of the plants above the point of inoculation wilted after 5 days. The upper parts of the plants appeared healthy until lesions girdled the stems. The plants treated with fungus-free agar remained healthy. The fungus was re-isolated from the margins of lesions on the inoculated plants. The pathogen has been reported to cause stem lesions and fruit rot of pepper in greenhouses in England (1) and Canada (2). Fruit symptoms were not observed in the Florida greenhouse. Stem symptoms were again reported from the same greenhouse in the following season.

References: (1) J. T. Fletcher. Plant Pathol. 43:225–222, 1994. (2) W. R. Jarvis. Can. Plant Dis. Surv. 74:131–134, 1994.
First Report of a Member of Aster Yellows Phytoplasma Group and of Clover Proliferation Phytoplasma Group Associated with Onion in Texas
Authors: Lee I.-M. , Dane R. A. , Black M. C.
Published: May 2007

An unknown disease(s) emerged this spring (2000) in an onion field in southwestern Texas. Infected onion plants exhibited two symptom types, one with shoot proliferation, moderate stunting of plants, and light yellowish discoloration on leaves (A) and the other with only severe stunting of the plants (B). The bulbs of the infected plants collected from both symptom types were smaller than normal. When the aerial shoots were trimmed, the infected (but not asymptomatic or the severely stunted) bulbs produced multiple slender sprouts after storage in room temperature for about a month. These symptoms are characteristic of yellows diseases caused by phytoplasmas. Ten symptomatic (six with symptom type A and four with symptom type B) and ten symptomless onion plants were collected in early May from an onion field about 1 to 2 weeks prior to blooming. Total nucleic acid was extracted from 0.5 g of shoot tissues from each sample. Nested polymerase chain reaction (PCR) using universal primer pairs (P1/P7 followed by R16F2n/R16R2) previously designed based on 16S and 23S rRNA gene sequence (1,2) was employed for the detection of phytoplasma(s) present in the samples. Specific PCR products (all were about 1.2 kb) were heavily amplified from five samples with symptom type A and one with symptom type B. Three of the symptomatic plants showing symptom type B and five of the symptomless samples were scored as weak positives. Restriction fragment length polymorphism (RFLP) analyses of the PCR products obtained from all five symptomatic samples with symptom type A using restriction enzymes including MseI, HhaI, and HpaII revealed that the associated phytoplasmas detected belonged to aster yellows phytoplasma group (16SrI), subgroup A. RFLP analyses of PCR product from the sample with symptom type B indicated that the associated phytoplasma belonged to clover proliferation group (16SrVI), subgroup A (1). Since symptom type A resembles onion yellows reported elsewhere, we propose to adopt “onion yellows” to refer to the new onion disease occurring in Texas. However, correlation between a member of clover proliferation phytoplasma group and onion plants showing severe stunting could not be firmly established. A phytoplasma belonging to 16SrI-B is associated with onion yellows disease reported in Japan (1). This is the first report that onion yellows occurs in the United States.

References: (1) I.-M. Lee et al. Int. J. Syst. Bacteriol. 48:1153, 1998. (2) B. Schneider et al. 1995. Molecular and Diagnostic Procedures in Mycoplasmology, Vol. I, Academic Press, San Diego, CA.
Spathiphyllum sp.: A New Natural Host of Impatiens necrotic spot virus
Authors: Materazzi A. , Triolo E.
Published: May 2007

In September 1999, several Spathiphyllum plants grown in a greenhouse in Tuscany (Italy) showed leaf symptoms in the form of concentric chlorotic ringspots, line patterns, and irregular chlorotic blotches. These symptoms developed into localized necrosis. Crude sap of tissues showing symptoms was mechanically inoculated to young symptomless Spathiphyllum plants and to Nicotiana benthamiana and N. clevelandii. Samples drawn from symptomatic and symptomless tissues of naturally or artificially infected Spathiphyllum and Nicotiana plants were tested for the presence of Alfalfa mosaic virus (AMV), Arabis mosaic virus (ArMV), Cucumber mosaic virus (CMV), Dasheen mosaic virus (DsMV), Impatiens necrotic spot virus (INSV), Potato X virus (PVX), Potato Y virus (PVY), Tobacco mosaic virus (TMV), and Tomato spotted wilt virus (TSWV) by double-antibody sandwich enzyme-linked immunosorbent assay carried out with commercial antisera. The symptomatic tissues obtained from Spathiphyllum and Nicotiana plants gave a positive reaction only for INSV. The symptomless samples obtained from various parts of the infected Spathiphyllum plants gave a negative reaction, even after 1 year from the appearance of localized necrosis, suggesting a non-systemic infection in this new host. This is the first report of infection of Spathiphyllum sp. by INSV.
First Report of a Root and Crown Rot Disease of Myrtle in California Caused by Cylindrocladium pauciramosum
Authors: Koike S. T. , Crous P. W.
Published: May 2007

Myrtle (Myrtus communis) is a woody, evergreen plant used in California as a landscape shrub or potted plant. In 2000, a new root and crown disease was found in commercial nursery myrtle being grown as potted plants. Roots were necrotic and crown tissue was brown. Affected plants became gray-green in color, withered, and died. A Cylindrocladium sp. was consistently isolated from roots, crowns, and lower stems of symptomatic plants. Isolates were characterized by having penicillate conidiophores terminating in obpyriform to broadly ellipsoidal vesicles. Conidia were hyaline, 1-septate, straight with rounded ends, (50-) 53 to 56 (-58) × (3.5-) 4 to 6 μm, placing it in the Cylindrocladium candelabrum Viégas species complex. Single-conidial isolates (STE-U 4012 to 4018) produced perithecia with viable progeny of Calonectria pauciramosa C.L. Schoch & Crous when mated on carnation leaf agar with tester strains of Cylindrocladium pauciramosum C.L. Schoch & Crous (2). Matings with tester strains of all other species in this complex proved unsuccessful. Only one mating type of C. pauciramosum has thus far been found in the United States. Pathogenicity of representative isolates was confirmed by applying 5 ml of a conidial suspension (1.0 × 106 conidia/ml) to the crowns of potted, 5-month-old, rooted mytle cuttings that were subsequently maintained in a greenhouse (23 to 25°C). After 4 weeks, plant crowns and roots developed symptoms similar to those observed in the nursery, and plants later wilted and died. C. pauciramosum was re-isolated from all plants. Control plants, which were treated with water, did not develop any symptoms. The tests were repeated and the results were similar. This is the first report of C. pauciramosum as a pathogen of myrtle in California. The disease has been reported on myrtle in Europe (1).

References: (1) G. Polizzi and P. W. Crous. Eur. J. Plant Pathol. 105:407, 1999. (2) C. L. Schoch et al. Mycologia 91:286, 1999.
Association of “Candidatus Phytoplasma australiense” with Sudden Decline of Cabbage Tree in New Zealand
Authors: Andersen Mark T. , Beever Ross E. , Sutherland Paul W. , Forster Richard L. S.
Published: May 2007

Sudden decline of the New Zealand cabbage tree (Cordyline australis) results in the rapid death of affected plants within months of first external symptoms becoming apparent. Symptoms, which have been observed in saplings and mature trees, include vascular discoloration and leaf yellowing followed by leaf desiccation and eventual plant collapse. Previous work failed to link the disease with any causal agent. A phytoplasma has now been detected in all symptomatic saplings and some symptomatic trees tested, using one-step and nested polymerase chain reaction (PCR) to amplify portions of the 16S rRNA gene. This phytoplasma was not detected in nonsymptomatic plants. Phytoplasma DNA was found in shoot and rhizome apices, leaves and wood tissue of saplings, and in the rhizome apex and trunk tissues of adult trees. Sequencing of the PCR products from selected samples indicated that the phytoplasma is “Candidatus Phytoplasma australiense.” Phytoplasma cells were detected by transmission electron microscopy in phloem sieve tubes of the rhizomes of affected saplings. One sapling with early symptoms recovered after injection with tetracycline antibiotic, but two saplings with advanced symptoms did not recover. It is concluded that “Candidatus Phytoplasma australiense” is present in symptomatic plants and is the cause of sudden decline.
Aggressiveness to Pumpkin Cultivars of Isolates of Phytophthora capsici from Pumpkin and Pepper
Authors: Lee Byung Kook , Kim Beom Seok , Chang Seog Won , Hwang Byung Kook
Published: May 2007

Nine isolates of Phytophthora capsici obtained from pumpkin and pepper in diverse geographic areas, including Korea, France, Italy, and the United States, were evaluated for their ability to cause disease on nine Korean and Japanese pumpkin cultivars under controlled environmental conditions. No hypersensitive type of resistance was observed in any of the pumpkin cultivars inoculated with P. capsici. Disease incidence ranged from low to high, indicating varying levels of partial (quantitative) resistance. In addition, a significant cultivar-isolate interaction was observed, indicating that host specialization was present in some cultivars. Disease severity increased with inoculum density of P. capsici. The Korean cultivar Danmatmaetdol was highly resistant to the P. capsici isolates tested, suggesting that economic levels of resistance exist in pumpkin. The pumpkin isolates from all locations caused more disease than the pepper isolates to all the pumpkin cultivars tested. Soil-drench and stem-wound inoculation methods were more reliable than a foliar-inoculation method for evaluating pumpkin cultivar resistance.
Coffee Leaf Scorch Caused by a Strain of Xylella fastidiosa from Citrus
Authors: Li W.-B. , Pria W. D. , Teixeira D. C. , Miranda V. S. , Ayres A. J. , Franco C. F. , Costa M. G. , He C.-X. , Costa P. I. , Hartung J. S.
Published: May 2007

Citrus variegated chlorosis (CVC) and coffee leaf scorch (CLS) are two economically important diseases in Brazil caused by the bacterium Xylella fastidiosa. Strains of the bacterium isolated from the two plant hosts are very closely related, and the two diseases share sharpshooter insect vectors. In order to determine if citrus strains of X. fastidiosa could infect coffee and induce CLS disease, plant inoculations were performed. Plants of coffee, Coffea arabica ‘Mundo Novo’, grafted on Coffea canephora var. robusta ‘Apuatão 2258’ were mechanically inoculated with triply cloned strains of X. fastidiosa isolated from diseased coffee and citrus. Three months postinoculation, 5 of the 10 plants inoculated with CLS-X. fastidiosa and 1 of the 10 plants inoculated with CVC-X. fastidiosa gave positive enzyme-linked immunosorbent assay (ELISA) and/or polymerase chain reaction (PCR). Eight months postinoculation, another six plants inoculated with CVC-X. fastidiosa gave positive PCR results. The two X. fastidiosa strains were isolated from the inoculated plants and showed the same characteristics as the original clones by microscopy, ELISA, and PCR. None of the plants inoculated with sterile periwinkle wilt (PW) medium as controls gave positive reactions in diagnostic tests, and none developed disease symptoms. Six months postinoculation, seven plants inoculated with CLS-X. fastidiosa and eight inoculated with CVC-X. fastidiosa began to develop characteristic CLS symptoms, including apical and marginal leaf scorch, defoliation, and reductions of internode length, leaf size, and plant height, terminal clusters of small chlorotic and deformed leaves, and lateral shoot dieback. We have demonstrated that X. fastidiosa from citrus plants is pathogenic for coffee plants. This has important consequences for the management of CLS disease and has implications for the origin of citrus variegated chlorosis disease.
Effect of Growth Stage on Susceptibility of Grape Berry and Rachis Tissues to Infection by Phomopsis viticola
Authors: Erincik O. , Madden L. V. , Ferree D. C. , Ellis M. A.
Published: May 2007

Intact ‘Seyval’ grape clusters in the greenhouse and ‘Catawba’ clusters in the field were inoculated with conidia of Phomopsis viticola at seven Eichorn-Lorenz growth stages between 12 (prebloom) and 35 (véraison) in 1998. Five pots (10 clusters) were used per inoculation, and the experiment was repeated three times. Also, 10 to 20 randomly selected Catawba clusters were inoculated in the field for each of three replications at each growth stage. Studies were repeated in 1999. In addition, Chambourcin clusters were also inoculated at four growth stages in the greenhouse in 1999. Results obtained in the greenhouse and field during both years and for all cultivars indicate that berry and rachis infections can occur at all growth stages between 12 and 35 with no evidence of decreasing susceptibility over time. Results disagree with some literature reports that indicate that berry infection occurs primarily during bloom and shortly after bloom, and susceptibility decreases as fruit matures.
First Report of Colletotrichum acutatum in Strawberry in Norway
Authors: Stensvand A. , Strømeng G. M. , Langnes R. , Hjeljord L. G. , Tronsmo A.
Published: May 2007

Anthracnose caused by Colletotrichum acutatum J. H. Simmonds was detected in strawberry (Fragaria × ananassa Duch.) for the first time in Norway in 1999. Symptoms were found in greenhouse grown strawberries in the cultivar Korona. Symptoms were typical of strawberry anthracnose: sunken, brown, and firm lesions appeared on maturing fruits. Masses of conidia were produced in acervuli in the center of lesions. The fungus was isolated on acidified potato dextrose agar. Colonies grown on potato dextrose agar (PDA) were pale to mouse gray and became dark greenish to blackish in reverse. Conidia were formed in orange to salmon pink masses in the center of the culture. Conidia in cultures were 16.5 (13.8 to 18.8) × 4.5 (3.8 to 5) μm, and were hyaline, cylindrical, with pointed ends, and aseptate. Setae were never observed in culture or on fruits. The fungus did not form an ascigerous stage in culture. Mycelial growth rate at 25 to 26°C on PDA was 8.1 to 8.4 mm per day. Morphological characters and growth rate were in accordance with previous reports on C. acutatum (1,2). The isolated fungus was confirmed to be C. acutatum by both the International Mycological Institute, Egham, England, and Centraalbureau voor Schimmelcultures, Baarn, the Netherlands. Koch's postulates were fulfilled by inoculating ripe and unripe fruits on strawberry plants with the isolated fungus. Fruits were either sprayed with a conidial suspension (106 conidia per ml) or slightly wounded with a needle that had been dipped in a conidial mass from a pure culture of C. acutatum. Symptoms appeared after 4 days at 20°C, and after 5 days, brown, sunken, circular lesions reached a size of 1 cm in diameter on wounded, ripe fruits. In unripe fruits the lesions developed more slowly, and in unwounded fruits sprayed with a conidial suspension, large, irregular spots developed. Leaves were inoculated by placing a small block of agar at the base of petioles on intact strawberry plants. The tissue underneath the agar was either unwounded or slightly wounded with a needle. After 20 days (at 20 to 25°C) some necrosis developed on both unwounded and wounded petioles. No symptoms were observed in the crown tissue where the inoculated petioles were attached. The fungus was readily reisolated from both fruits and petioles, after which typical morphological characters developed in culture as described above.

References: (1) P. S. Gunnell and W. D. Gubler. Mycologia 84:157, 1992. (2) B. J. Smith and L. L. Black. Plant Dis. 74:69, 1990.
Evidence that Cercospora carotae Causes Leaf Spot on Carrot in Western Washington
Authors: Inglis D. A. , Derie M. L. , Volker K. C.
Published: May 2007

During 1999, a leaf spot on carrot (Daucus carota L. subsp. sativus [Hoffm.] Arcang.) was observed on nearly every plant in a 20-ha field of carrots (cv. Red Chantenay) grown for processing in western Washington. Circular to elongate, light brown lesions surrounded by chlorosis were present on leaflet margins and petioles of affected plants. Conidia of Cercospora carotae (Pass.) Solheim were present in the lesions. Small pieces of surface-sterilized leaf tissue were placed onto potato dextrose agar plates and incubated at room temperature to obtain fungal isolates. Koch's postulates were completed by atomizing the upper and lower leaves of carrot seedlings at the three to four leaf stage with sterile water or C. carotae at 1.0 × 104 conidia/ml in sterile 0.01% Tween 80. Treatments were replicated five times using single plants. The plants were bagged in clear plastic and placed in a greenhouse at 25°C for 72 h. Disease symptoms developed within 10 days as light brown lesions on leaflet margins and petioles, and were similar to those found in the field. The fungus was reisolated as described above. Symptoms did not develop in control plants sprayed with water. Farr et al. (1) report that C. carotae occurs in several states but not Washington, and Shaw (2) lists C. carotae only from British Columbia and Oregon. To our knowledge, this is the first report of Cercospora leaf spot on carrot in Washington.

References: (1) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN. (2) C. G. Shaw. W.S.U. Agric. Exp. Sta. Bull. 765, 1969.
First Record of Beet necrotic yellow vein virus in Denmark
Authors: Nielsen S. L. , Nicolaisen M. , Scheel C. , Dinesen I. G.
Published: May 2007

Beet necrotic yellow vein virus (BNYVV) causes rhizomania in beets. BNYVV is widespread in Europe and can be divided into an A and B group based on reverse transcription-polymerase chain reaction (RT-PCR) restriction fragment length polymorphism (RFLP) analysis (1). The vector of BNYVV, Polymyxa betae, is widespread in Denmark. However, surveys for BNYVV have regularly been carried out in Denmark since 1985, but it has not been detected until now. In the autumn of 2000, attention was drawn to a sugar beet field in the southeastern part of Denmark containing plants with unusually low sugar content. Typical BNYVV symptoms of bearded roots were observed on all plants sampled in the field. Root samples of 12 plants all tested positive for the presence of BNYVV by ELISA using antiserum from Adgen, Loewe, and Aschersleben, respectively. Immunosorbent electron microscopy with antiserum to BNYVV coat protein revealed decorated rod-shaped particles of lengths typical for BNYVV. Pulverized infected root tissue was used to mechanically inoculate Chenopodium quinoa and resulted in formation of few local chlorotic lesions. RNA was extracted from symptomatic C. quinoa and subjected to RT-PCR analysis using two primer sets specific for RNA 2 of BNYVV (1) and bands of the expected sizes were observed with both. The nucleotide sequence of a part of the PCR products corresponding to the N-terminus of the coat protein was determined and showed 99.5% identity to sequences derived from A group isolates (1). Finally, a bait-plant test was carried out, where sugar beet seeds were sown in 20 soil samples collected from different locations within the infested field. After 8 weeks of growth, all samples tested positive for the presence of BNYVV by ELISA, indicating that the entire field is infested and that viruliferous P. betae must have been present in several years. To our knowledge, this is the first record of BNYVV in Denmark.

Reference: (1) M. Kruse et al. J. Gen. Virol. 75:1835, 1994.
First Report of Arceuthobium globosum subsp. grandicaule in Honduras
Authors: Melgar J. , Mathiasen R. , Howell B.
Published: May 2007

Large-stemmed dwarf mistletoe (Arceuthobium globosum Hawksw. & Wiens subsp. grandicaule Hawksw. & Wiens-Viscaceae) parasitizes several Pinus spp. in central Mexico and western Guatemala (1). In November 2000 several trees of Pinus hartwegii Lindley were discovered being parasitized by this dwarf mistletoe near the summit of Cerro las Minas, Montana de Celaque (2850 m elevation) approximately 12 km southwest of Gracias, Department Lempira, Honduras. Species identification was based on the size of the plants, which were greater than 50 cm in height, and the dark brown color and size (2.1 to 4.5 cm) of the stem base (1). There was no apparent infection of nearby Pinus ayacahuite Ehrenb., which is known to be immune to the pathogen. Specimens of A. globosum subsp. grandicaule were collected and deposited at the Herbario, Escuela Nacional de Ciencias Forestales, Siguatepeque, Honduras and at the Deaver Herbarium, Northern Arizona University, Flagstaff. To our knowledge, this is the first report of this dwarf mistletoe in Honduras and extends its eastern distribution from west-central Guatemala by approximately 300 km.

Reference: (1) F. G. Hawksworth and D. Wiens. 1996. Dwarf Mistletoes: Biology, Pathology, and Systematics. USDA Agric. Handb. 709.
Characterization and Control of Garlic Rust in California
Authors: Koike Steven T. , Smith Richard F. , Davis R. Michael , Nunez J. Joe , Voss Ron E.
Published: May 2007

In 1998, a devastating outbreak of rust disease severely damaged the garlic crop in California, resulting in yield losses of 51% and an economic loss of 27% to the industry. The disease also occurred in 1999 and 2000, indicating that rust may have become an annual problem in some parts of the state. The presence of urediniospores, two-celled teliospores, and telial paraphyses indicated that the pathogen was Puccinia allii. Isolates from garlic infected onion and chives, but not leek, elephant garlic, or shallot in inoculation experiments. Garlic cloves obtained from diseased plants were planted under controlled conditions, but the resulting plants did not develop rust. Fungicide trials were conducted for 3 years and showed that none of the currently registered materials gave satisfactory control. However, tebuconazole and azoxystrobin provided good protection against rust if sprayed at 10-day intervals. A variety trial of 34 garlic cultivars and selections was planted, inoculated, and evaluated for resistance to rust. Although there was variability in rust severity among the selections, acceptable levels of resistance were not observed in any cultivar.
Infectivity Titration for Assessing Resistance to Leaf Scald Among Sugarcane Cultivars
Authors: Lopes S. A. , Damann K. E. , Hoy J. W. , Grisham M. P.
Published: May 2007

Greenhouse experiments were conducted to determine potential of infectivity titration to evaluate resistance of sugarcane to leaf scald disease caused by Xanthomonas albilineans. In two experiments, single-bud cuttings were inoculated with suspensions containing 101, 105, or 108 CFU/ml of X. albilineans. The occurrence of symptoms was recorded every 15 days from 45 to 210 days after inoculation. At the final evaluation date, leaf vascular sap was plated onto selective medium to detect latent infections. ED50 (log10 of the bacterial concentration required to infect 50% of inoculated plants) was estimated for each cultivar based on probit analysis of cumulative infection frequency. Frequency of infected plants varied among inoculum doses and cultivars and resulted in ED50 values ranging from 3.0 to 12.3 and 3.1 to 9.8 in the first and second experiments, respectively. Good agreement between experiments was observed for ED50 values of individual cultivars. Differences in ED50 among cultivars agreed with field observations of natural disease incidence. Cultivar responses to leaf scald were compared based on the cumulative frequencies of death and recovery in symptomatic plants, and the frequencies of symptomatic plants observed at different evaluation dates for plants inoculated with 108 CFU/ml of X. albilineans. Good agreement between ED50 values and these responses was observed. Greenhouse inoculation tests using infectivity titration or just one inoculum concentration could provide an alternative to field tests for the assessment of sugarcane resistance to leaf scald.
RT-PCR Based Detection ofRupestris stem pitting associated virusWithin Field-Grown Grapevines Throughout the Year
Authors: Stewart Sandra , Nassuth Annette
Published: May 2007

The presence of Rupestris stem pitting associated virus (RSPaV) can go unnoticed since symptoms appear only if additional viruses are present. Detection by reverse transcription-polymerase chain reaction (RT-PCR) is possible; however, this assay could be unreliable if the tissue that is being tested has detection-interfering compounds, or if the virus has a low titer. This paper reports on (i) use of a recently developed extraction method and internal control to determine which tissues from field-grown grapevines yield extracts that are reliable for virus detection by RT-PCR, and (ii) a survey for RSPaV of different tissues from the Vitis vinifera varieties Riesling, Chardonnay, Cabernet Franc, Merlot, Sauvignon Blanc, Pinot Noir, and Gamay, as well as from the rootstocks 3309 and Riparia, which were harvested in Ontario, Canada, at different times of the year. Amplifiable extracts were obtained from virtually all bud, shoot tip, seed, and cane samples tested. Detectable amounts of RSPaV were generally found in all tissues of infected plants except young buds collected in the summer. A combination of three single buds from dormant canes, less time-consuming than the preparation of cane shavings, was a reliable source for RSPaV detection.
Effect of Gaseous Ozone Exposure on the Development of Green and Blue Molds on Cold Stored Citrus Fruit
Authors: Palou Lluís , Smilanick Joseph L. , Crisosto Carlos H. , Mansour Monir
Published: May 2007

The effects of gaseous ozone exposure on in vitro growth of Penicillium digitatum and Penicillium italicum and development of postharvest green and blue molds on artificially inoculated citrus fruit were evaluated. Valencia oranges were continuously exposed to 0.3 ± 0.05 ppm(vol/vol) ozone at 5°C for 4 weeks. Eureka lemons were exposed to an intermittent day-night ozone cycle (0.3 ± 0.01 ppm ozone only at night) in a commercial cold storage room at 4.5°C for 9 weeks. Both oranges and lemons were continuously exposed to 1.0 ± 0.05 ppm ozone at 10°C in an export container for 2 weeks. Exposure to ozone did not reduce final incidence of green or blue mold, although incidence of both diseases was delayed about 1 week and infections developed more slowly under ozone. Sporulation was prevented or reduced by gaseous ozone without noticeable ozone phytotoxicity to the fruit. A synergistic effect between ozone exposure and low temperature was observed for prevention of sporulation. The proliferation of spores of fungicide-resistant strains of these pathogens, which often develop during storage, may be delayed, presumably prolonging the useful life of postharvest fungicides. In vitro radial growth of P. italicum, but not of P. digitatum, during a 5-day incubation period at 20°C was significantly reduced by a previous 0.3 ± 0.05 ppm ozone exposure at 5°C for 4 days. Inoculum density did not influence the effect of gaseous ozone on decay incidence or severity on oranges exposed to 0.3 ± 0.05 ppm ozone at 20°C for 1 week. Susceptibility of oranges to decay was not affected by a previous continuous exposure to 0.3 ± 0.05 ppm ozone at 20°C for 1 week. A corona discharge ozone generator was effective in abating ethylene in an empty export container.
First Report of Peanut stripe virus (Family Potyviridae) in South Korea
Authors: Choi H. S. , Kim Jeong-Soo , Cheon Jeong-Uk , Choi Jang- Kyung , Pappu S. S. , Pappu H. R.
Published: May 2007

Severe mosaic symptoms resembling those reported for a blotch isolate of Peanut stripe virus (PStV) (1) were observed in the year 1998 in Suwon, South Korea, on several peanut cultivars. The incidence of the virus was as high as 100% in cv. Daekwang. The virus was seed transmitted to varying degrees depending on the cultivar and a maximum seed transmission of 15.7% was observed in cv. Aul. Electron microscopic examination of leaf dip preparations showed filamentous rods having modal length of 720 nm. Viral inclusion bodies in infected cells were of pinwheel, scroll, and laminated aggregates. The 3' terminal region of the viral genome was amplified using degenerate primers (2) and the resulting approximately 700 bp fragment was cloned and sequenced. GenBank searches using the 709 nucleotides consisting of the complete 3'-untranslated region and a part of the coat protein gene showed that the virus shared 98% sequence identity with the currently known PStV isolates. To our knowledge, this is the first report of PStV in the Republic of Korea.

References: (1) J. W. Demski et al. Ann. Appl. Biol. 105:495, 1984. (2) S. S. Pappu et al. J. Virol. Methods 41:9, 1993.
Yield Comparison of Hybrid Agaricus Mushroom Strains as a Measure of Resistance to Trichoderma Green Mold
Authors: Anderson M. G. , Beyer D. M. , Wuest P. J.
Published: May 2007

Commercially available strains of hybrid white, hybrid off-white, and brown Agaricus bisporus mushrooms were compared for resistance to green mold caused by Trichoderma harzianum biotype 4 (Th4). Seven mushroom spawn strains were assessed for total weight of mushrooms (grams per 0.1 m2) with or without the addition of an aqueous Th4 spore suspension added at spawning time. Cropping studies were conducted at the Mushroom Research Center (Pennsylvania State University) to emulate commercial growing operations. Excessive spawn handling had no significant effect on development of green mold. Severity of green mold was related to time between infestation and green mold appearance, with more significant yield losses occurring when green sporulation was detected early in production. Significant differences in yield were measured among mushroom strains in response to Th4 infestation. Hybrid white strains were extremely susceptible, with a mean yield loss of 96%. Hybrid off-white strains exhibited intermediate susceptibility, with mean yield losses of 56 to 73%. Brown strains were highly resistant, with mean yield losses of 9 to 16%. From these findings, we report the existence of green mold resistance, with a continuum of resistance among spawn strains. The findings suggest use of brown strains to manage green mold outbreaks, particularly where benomyl resistance in Trichoderma spp. is a threat.
Role of the ShrubTamarix niloticain Dissemination ofFusarium oxysporumf. sp.radicis-lycopersici
Authors: Rekah Y. , Shtienberg D. , Katan J.
Published: May 2007

The saltcedar shrub Tamarix nilotica grows as a weed in the Arava region of Israel. This weed is commonly found in cultivated fields naturally infested with Fusarium oxysporum f. sp. radicis-lycopersici, the causal agent of tomato crown and root rot. Young bushes, 20 to 40 cm tall, were randomly uprooted from different fields. The roots were cut into segments which were placed on Fusarium-selective medium. Although the plants did not show any symptoms of disease, the roots of the shrub were colonized by the pathogen. The incidence of infected saltcedar plants and level of root colonization by F. oxysporum f. sp. radicis-lycopersici decreased with increasing distance of the sampling location from a tomato field infected with crown and root rot. F. oxysporum f. sp. radicis-lycopersici was also isolated from chaff of inflorescence samples taken from mature T. nilotica shrubs. Identity of the pathogen isolates obtained from T. nilotica roots and chaff samples was verified by pathogenicity and vegetative compatibility tests. Roots of T. nilotica plants sown under greenhouse conditions in soil naturally infested with F. oxysporum f. sp. radicis-lycopersici became colonized by the pathogen. Uprooting and removing saltcedar plants throughout the season from fields not cultivated with tomatoes lowered the inoculum density of F. oxysporum f. sp. radicis-lycopersici in the soil from 611 to 6 and from 176 to 10 CFU/g of soil in the 1998-99 and 1999-2000 growing seasons, respectively. These results demonstrate that T. nilotica may contribute to the buildup of the pathogen populations in the absence of a susceptible host. Colonization of saltcedar by F. oxysporum f. sp. radicis-lycopersici is an additional mechanism for survival of this pathogen in the fields and for dissemination through the spread of infested seed or chaff of T. nilotica.
Effects of Water Stress on Botryosphaeria Blight of Pistachio Caused by Botryosphaeria dothidea
Authors: Ma Zhonghua , Morgan David P. , Michailides Themis J.
Published: May 2007

The effects of water potential (Ψ) on spore germination, germ tube elongation, mycelial growth of Botryosphaeria dothidea, and development of Botryosphaeria blight of pistachio caused by this fungus were studied in the laboratory and greenhouse. In laboratory tests, spore germination, germ tube elongation, and mycelial growth of B. dothidea increased as Ψ decreased from 0 to -2.0 MPa and declined as Ψ decreased below -2.0 MPa. Water stress (Ψ < -0.260 MPa) increased the severity of Botryosphaeria blight on young detached pistachio leaves. In greenhouse inoculation experiments, drought-stressed 2-year-old pistachio trees (leaf Ψ < -0.635 MPa) developed more severe Botryosphaeria blight disease than the nonstressed trees (Ψ > -0.485 MPa) in both 1999 and 2000 experiments. In a similar experiment using 1-year-old potted pistachio trees in 2000, withholding water treatments did not cause enough drought stress in pistachio leaves (Ψ > -0.584 MPa) and did not result in higher disease than the nonstressed trees (Ψ = -0.466 MPa). The correlation coefficient between Ψ and disease index for 1999 experiments was 0.954, and for 2000 experiments I and II was 0.981 and 0.939, respectively. These results indicate that drought stress can be a major predisposing factor of pistachio to infection by B. dothidea. Results from this study can be used to better understand the disease outbreaks in California pistachio orchards and to develop integrated management strategies by adjusting irrigation.
Oversummer Survival of Inoculum for Colletotrichum Crown Rot in Buried Strawberry Crown Tissue
Authors: Ureña-Padilla A. R. , Mitchell D. J. , Legard D. E.
Published: May 2007

The oversummer survival of Colletotrichum gloeosporioides in strawberry crown tissue under field conditions was investigated in 1998 and 1999. Strawberry crowns infected naturally with C. gloeosporioides were placed inside cloth bags containing field soil, buried in the field at 5 or 13 cm, then recovered over 6 months of each year. The recovered crowns were plated onto a Colletotrichum spp. semiselective medium and speciated by colony, spore morphology, and molecular markers with species-specific DNA primers. Pathogenicity of selected isolates was confirmed by greenhouse bioassays on strawberry. Of the 428 isolates of Colletotrichum spp. recovered from buried crowns, 96% were C. gloeosporioides and 4% Colletotrichum acutatum. Following an initial increase in the detection of the fungus, survival of C. gloeosporioides was stable for 2 to 3 weeks, then declined. No Colletotrichum spp. were detected after burial for 56 days in 1998 and 98 days in 1999. Because the time between crop seasons is typically more than 170 days, these data support the hypothesis that inoculum of C. gloeosporioides does not survive in buried plant debris between seasons in Florida and, therefore, oversummering crop debris does not contribute inoculum for epidemics of Colletotrichum crown rot in Florida.
Field Response of Glyphosate-Tolerant Soybean to Herbicides and Sudden Death Syndrome
Authors: Sanogo S. , Yang X. B. , Lundeen P.
Published: May 2007

Three-year field experiments were conducted to assess the development of sudden death syndrome (caused by Fusarium solani f. sp. glycines) in three soybean cultivars, tolerant (P9344 and A3071) and nontolerant (BSR101), to glyphosate following foliar application of four herbicides (acifluorfen, glyphosate, imazethapyr, and lactofen) commonly applied to soybeans in the north-central region of the United States. Cultivar A3071 is resistant to sudden death syndrome, whereas cultivars P9344 and BSR101 are susceptible to this disease. There was no statistically significant cultivar-herbicide interaction with respect to the severity of foliar symptoms of the disease and the frequency of isolation of F. solani f. sp. glycines from roots of soybean plants. Across all herbicide treatments, the level of sudden death syndrome was lower in the disease-resistant cultivar than in the susceptible ones. There was an increase in the disease levels under application of acifluorfen, glyphosate, and imazethapyr compared with nontreated or lactofen-treated plants. The results obtained indicate that the response of glyphosate-tolerant soybeans to sudden death syndrome is not different from the response of conventional soybeans to this disease following application of the selected herbicides, and the resistance of soybean to sudden death syndrome was not changed with application of glyphosate.
Leaf Spot Diseases on Winter Wheat Influenced by Nitrogen, Tillage, and Haying after a Grass-Alfalfa Mixture in the Conservation Reserve Program
Authors: Krupinsky J. M. , Tanaka D. L.
Published: May 2007

When contracts for the Conservation Reserve Program (CRP) expire, highly erodible land that had a long-term vegetative cover composed of grasses or grass-legume mixtures may be converted back to cropland. Considering that some of the same leaf spot pathogens found on grasses can cause diseases on wheat, the management practices used to convert these lands were evaluated for their effect on winter wheat leaf spot diseases. In a 3-year spring wheat-winter wheat-pea crop rotation, the major leaf spot diseases on winter wheat were tan spot and Stagonospora nodorum blotch. Removal of hay or leaving hay in the plots when converting grassland to cropland had no significant effect on leaf spot diseases, indicating that the residue from the grass-alfalfa crop did not influence leaf spot diseases on winter wheat. Tillage treatments did not influence the amount of disease in 1996, but with higher precipitation levels in 1999, higher disease severities were associated with the no tillage treatment. Higher levels of crop residue associated with the no tillage treatment could potentially carry over plant pathogens from one crop to the next. The severity of leaf spot diseases was consistently lower when nitrogen was applied, indicating the importance of nitrogen application when converting grassland to cropland.
Revised Subgroup Classification of Group 16SrV Phytoplasmas and Placement of Flavescence Dorée-Associated Phytoplasmas in Two Distinct Subgroups
Authors: Davis Robert E. , Dally Ellen L.
Published: May 2007

The subgroup classification of phytoplasmas in 16S rRNA group 16SrV (elm yellows phytoplasma group) was revised and extended on the basis of enzymatic restriction fragment length polymorphism (RFLP) analysis of ribosomal (r) DNA and analysis of putative restriction sites in nucleotide sequences. A 1.85 kbp fragment of the rRNA operon from flavescence dorée (FD) phytoplasma strain FD70 from France was amplified and cloned, and its nucleotide sequence determined (GenBank acc. no. AF176319). Placement of FD70 in subgroup V-C was verified by analysis of amplified DNA and of the cloned sequence. Hemp dogbane phytoplasma HD1 (AF122912), a member of subgroup V-C, was distinguished from other subgroup V-C phytoplasmas by putative restriction site differences in the 16S-23S rRNA spacer region. A previously published FD phytoplasma sequence (GenBank accession no. X76560) differed from FD70 sequence AF176319 by at least eight nucleotide substitutions and differences in putative restriction sites. The X76560 FD phytoplasma was classified in a new subgroup (V-D). Based on analyses of 16S rDNA GenBank sequence Y16395, Rubus stunt phytoplasma was classified in new subgroup V-E. The revised classification was supported by sequence similarities, group 16SrV-characteristic sequences, and a phylogenetic tree constructed on the basis of 16S rDNA sequences.
Differentiation, Distribution, and Elimination of Two Different Pineapple mealybug wilt-associated viruses Found in Pineapple
Authors: Sether D. M. , Karasev A. V. , Okumura C. , Arakawa C. , Zee F. , Kislan M. M. , Busto J. L. , Hu J. S.
Published: May 2007

Surveys for Pineapple mealybug wilt-associated virus-1 (PMWaV-1) and PMWaV-2 were conducted on pineapple samples from Hawaii and around the world. Tissue blot immunoassays (TBIAs) with two different monoclonal antibodies (MAb) specific to either PMWaV-1 or PMWaV-2 indicated that both closteroviruses are widely distributed throughout the pineapple-growing areas of the world. In the worldwide survey, PMWaV-1 was found in 80% of the mea-lybug wilt of pineapple (MWP)-symptomatic and 78% of the asymptomatic pineapple plants tested. A subset of plants was tested for PMWaV-2; 100% of the symptomatic plants and 12% of the asymptomatic plants were positive for this virus. A reverse transcription-polymerase chain reaction (RT-PCR) assay was developed to differentiate between PMWaV-1 and PMWaV-2. Oligonucleotide primers were designed using distinct regions of the HSP 70 homolog genes of the two viruses. PMWaV-specific RT-PCR assays and TBIAs were used to screen the pineapple accessions maintained at the United States Department of Agriculture-Agricultural Research Service National Clonal Germplasm Repository for PMWaV infection; 73% of the accessions were found infected with at least one PMWaV. Pineapple accessions found PMWaV-free were challenged with viruliferous mealybugs to test for immunity to PMWaV-1. No immune germ plasm was identified. Potential alternative virus hosts were screened for infection with virus-specific RT-PCR assays and TBIAs and were also challenged with viruliferous mealybugs. No alternate hosts of PMWaV-1 or PMWaV-2 were identified. PMWaV-1 infection was eliminated through axillary and apical bud propagation from infected crowns. Strategies to manage MWP are discussed.