bluuebunny/crossref_metadata_2025 huggingface dataset:
A PCR-based Technique for Identification of Fusicoccum sp. from Pistachio and Various Other Hosts in California
Authors: Ma Zhonghua , Michailides Themis J.
Published: May 2007

Botryosphaeria panicle and shoot blight of pistachio, caused by Fusicoccum sp. is a destructive disease in California. In this study, a pair of group-specific polymerase chain reaction (PCR) primers BDI and BDII, was developed for identification of Fusicoccum sp. from pistachio and other hosts in California based on the sequences of the rDNA internal transcribed spacer (ITS) region. The primers amplified a 356-bp DNA fragment for all 73 tested isolates of Fusicoccum sp. collected from pistachio and other hosts throughout California in different years, but not for the other 33 fungal species isolated from pistachio and the eight isolates of Fusicoccum sp. obtained from pistachio trees in Greece. The PCR assay using this pair of primers was sensitive enough to detect 5 pg of genomic DNA of Fusicoccum sp. A simple DNA extraction procedure was developed that led to the rapid identification of Fusicoccum sp. from pistachio and other host plants in California.
Limiting Populations and Spread of Clavibacter michiganensis subsp. michiganensis on Seedling Tomatoes in the Greenhouse
Authors: Werner N. A. , Fulbright D. W. , Podolsky R. , Bell J. , Hausbeck M. K.
Published: May 2007

Symptomless greenhouse tomato transplants may harbor high populations of Clavibacter michiganensis subsp. michiganensis, the causal agent of bacterial canker, leading to yield loss in the field. The objective of this study was to determine whether resistant cultivars, acibenzolar-S-methyl, avirulent strains of C. michiganensis subsp. michiganensis, or standard bactericides reduce pathogen populations and spread among greenhouse tomato seedlings. All treatments limited pathogen populations compared with the untreated inoculated susceptible cultivar in 1996 and 1998, but not in 1997. In 1996, copper hydroxide alone or mixed with mancozeb or streptomycin limited pathogen populations relative to acibenzolar-S-methyl, acibenzolar-S-methyl mixed with copper hydroxide, and avirulent strains. Copper hydroxide mixed with streptomycin limited pathogen populations compared with copper hydroxide mixed with mancozeb. Adding copper hydroxide to acibenzolar-S-methyl limited pathogen populations compared with acibenzolar-S-methyl alone. In 1998, treatments did not differ significantly from each other in limiting pathogen populations. The treatments limited spread of the bacterium only in 1997. Copper hydroxide mixed with mancozeb limited spread compared with copper hydroxide mixed with streptomycin. Pathogen spread was also reduced among resistant cultivars compared with the susceptible cultivar treated with streptomycin. In the field, the untreated inoculated susceptible cultivar produced yields that were 61% (1996) and 93% (1997) of those produced by the uninoculated susceptible cultivar. Fruit spotting occurred regardless of treatment. To prevent severe bacterial canker disease in the field, growers should initiate and sustain bactericide applications to tomato transplants while in the greenhouse to suppress pathogen populations. Cultivar resistance and acibenzolar-S-methyl may be helpful in disease management of bacterial canker on tomato.
Citrus psorosis virus Bark Scaling on Tarocco Sweet Orange
Authors: Tessitori M. , Rosa R. La , Catara A.
Published: May 2007

Despite the wide distribution of vein flecking of citrus leaves in Italy, psorosis bark scaling has been reported only on Navelina sweet orange (Citrus sinensis L.), and Thompson and Washington navel oranges (1). Infection has not been found on any local sweet orange cultivars. Among these is Tarocco, a sweet orange cultivar that originated in Sicily, is very common because of the high fruit quality, has an attractive fruit appearance, and has blood-red pigmented flesh. In April 2001, classic psorosis bark scaling symptoms were observed on the main limbs of 10-year-old Tarocco trees grafted on sour orange rootstock, originally obtained by topworking Clementine (C. reticulata Blanco) trees with scions collected from 19-year-old Tarocco trees with no bark scaling at that time. The symptomatic trees first displayed one or two isolated circular patches of scales with gumming on the main or secondary limbs. As the disease progressed, the number of patches increased and coalesced to form bigger scales, resulting in bark flaking. Approximately 15% of trees in the field showed different stages of the disease. All of the affected trees showed vein flecking of young leaves. A leaf pattern was also present in a few plants without bark symptoms. Bark symptoms were correlated with the presence of Citrus psorosis virus (CPsV). Samples (110 representing 10% of the total number of trees in a field located in the area of Catania, Sicily) were collected during the spring flush using a W-pattern sampling method and tested by double-antibody sandwich enzyme-linked immunoassay (DAS-ELISA) (monoclonal antibody [MAb] PS29) (2). Of trees tested, 14% showed bark scaling, and 86% were symptomless. All symptomatic plants were tested and 70% of symptomless trees were positive based on DAS-ELISA. To confirm DAS-ELISA results, 10 field samples were also tested by bioassay on indicator plants (Navelina sweet orange ISA 315 and Pineapple sweet orange), triple-antibody sandwich enzyme-linked immunoassay (TAS-ELISA), and immunosorbent electron microscopy (ISEM) with a different antiserum (MAb 13C5). DAS-ELISA-positive samples produced vein flecking on indicator plants, were positive based on TAS-ELISA, and contained typical CPsV particles based on ISEM (R. G. Milne, IFA, CNR, Turin). To our knowledge, this is the first demonstration of psorosis bark scaling reaction of Tarocco sweet orange due to CPsV infection.

References: (1) A. Catara et al. Proc. Int. Soc. Citri. 1:426, 1981. (2) M. Tessitori et al. Proc. 15th Conf. IOCV, IOCV, Riverside. In press.
Evaluation of a Reduced Copper Spraying Program to Control Bacterial Blight of Walnut
Authors: Ninot Antònia , Aletà Neus , Moragrega Concepció , Montesinos Emilio
Published: May 2007

Walnut blight, caused by Xanthomonas arboricola pv. juglandis, is currently controlled in western Europe through a standard schedule of seven applications of sprayed copper from bud break until harvest. A reduced spray schedule, with the last four applications omitted, was compared to the standard program in experimental plots for 3 years. Bacterial population levels in the spring were not significantly different between trees subjected to reduced sprays and those subjected to the standard schedule, but in summer they were higher in the trees that received fewer sprays compared with the standard program. However, disease control on nuts was similar or even better with the reduced spraying program than with the standard program, with the additional economic benefit of four fewer copper applications. After 3 years of using the reduced spray program, the amount of copper accumulated in the soil was significantly lower (about half) than that found in the soil where the standard spray program was implemented.
Oat Lines with Effective Adult Plant Resistance to Crown Rust
Authors: Leonard K. J.
Published: May 2007

Race-specific resistance in oat does not provide adequate protection against crown rust because new virulent races of the pathogen often arise within a few years after cultivars with race-specific resistance are released. This study assessed levels of partial resistance in a series of experimental oat lines that showed reduced crown rust severity over 30 years of exposure to a diverse crown rust population. Oat breeding lines with putative adult plant slow-rusting resistance to Puccinia coronata were evaluated in small isolated field plots for crown rust severity in natural epidemics and in controlled inoculations in the greenhouse for infection efficiency with a single virulent P. coronata isolate. Lines were also tested as seedlings against isolates from a local P. coronata population to detect race-specific resistance. In field tests, areas under the disease progress curves for all 14 experimental lines tested were significantly less than for cv. Starter, the susceptible check, and values for nine of the lines were significantly less than for Portage, a standard slow-rusting cultivar. Four lines with good field resistance were susceptible as seedlings to >85% of the local P. coronata population. One of the lines, MN841801, remained relatively free of rust in field plots over 7 years of tests, even in the 3 years when Starter was destroyed by crown rust. In greenhouse inoculations, adult plants of MN841801 developed only 7% as many uredinia as Starter. MN841801 can be an excellent source of effective, durable adult plant resistance to crown rust.
Involvement of Aureobasidium pullulans and Rhodotorula glutinis in Russet of d'Anjou Pear Fruit
Authors: Spotts R. A. , Cervantes L. A.
Published: May 2007

d'Anjou pear, the main cultivar grown in the Mid-Columbia Region of Oregon, is subject to russeting of the fruit surface, resulting in reduced quality and value. The role of Aureobasidium pullulans and Rhodotorula glutinis in russet of pear fruit was studied. Inoculations were done at full bloom in 1998 and 1999 and petal fall in 1999 with a log range of concentrations up to 108CFU/ml. Populations of A. pullulans on floral and fruit tissue were monitored during spring 1999 and 2000 in six orchards with a history of russet. Russet of fruit in both studies was evaluated at harvest. In 1998 neither fungus increased russet. In 1999, inoculation with two strains of each fungus at 108 CFU/ml increased russet. Inoculation with 104 or 106 CFU/ml did not increase russet in either year. In commercial orchards, there was no correlation between fruit russet and the populations of A. pullulans on floral and fruit tissue. Populations were less than 103 CFU/g of tissue. We conclude that A. pullulans and R. glutinis are not major contributors to russet of d'Anjou pear fruit in the Mid-Columbia Region.
Impact of Glucosinolate Content in Broccoli (Brassica oleracea (Italica Group)) on Growth of Pseudomonas marginalis, a Causal Agent of Bacterial Soft Rot
Authors: Charron Craig S. , Sams Carl E. , Canaday Craig H.
Published: May 2007

Glucosinolate degradation products are known to suppress microbes. Brassica species produce glucosinolates. Previous investigations determined that susceptibility to bacterial soft rot of broccoli (Brassica oleracea (Italica group)) varied significantly by cultivar. To evaluate the impact of glucosinolates on Pseudomonas marginalis, a causal agent of bacterial soft rot, glucosinolates were measured in lyophilized florets from broccoli ‘Arcadia’, ‘Emperor’, ‘Green Comet’, ‘Green Valiant’, ‘Marathon’, ‘Packman’, ‘Premium Crop’, and ‘Shogun’. Total glucosinolate content was highest in ‘Shogun’ (29.8 μmol/g) and lowest in ‘Emperor’ (0.5 μmol/g). In an in vitro assay, simple linear regression analysis showed that 48% of differences in suppression of P. marginalis growth could be explained by differences in total glucosinolate content (P ≤ 0.01). Plant breeding efforts should include glucosinolate levels as a factor in selecting for disease resistance.
The Use of Soil Solarization for the Management of Soilborne Plant Pathogens in Strawberry and Red Raspberry Production
Authors: Pinkerton J. N. , Ivors K. L. , Reeser P. W. , Bristow P. R. , Windom G. E.
Published: May 2007

Root rot caused by Phytophthora fragariae var. fragariae and P. fragariae var. rubi are major concerns in strawberry and raspberry production in the Pacific Northwest. Of lesser importance is black root rot of strawberry, caused by a complex of fungi and nematodes. Soil solarization was evaluated in 1997 in a strawberry planting and in 1998 in a raspberry planting for: (i) enhancing plant health and growth, and (ii) reducing population densities of root-destroying pathogens. Plots were solarized from mid-July to mid-September. Maximum and mean soil temperatures in solarized plots recorded at 10 cm depth were 48 and 33°C in the strawberry plots and 46 and 29°C in the raspberry plots. These temperatures were 7 to 17°C higher than temperatures recorded in nonsolarized plots. Soil collected after solarization was assayed by growing bait plants, cv. Totem strawberry or cv. Qualicum raspberry, at 15°C for 6 weeks in saturated soil to promote infections. Root health and plant growth were evaluated after 6 weeks. Solarization significantly reduced (P < 0.05) root necrosis and increased root weight of bait plants compared to plants grown in soil from nonsolarized plots. Infection of strawberry roots by P. fragariae, Pythium, Rhizoctonia, and Cylindrocarpon spp. was reduced (P < 0.05) by solarization in sampled soil. Disease was reduced in cv. Hood strawberries and Qualicum and Skeena red raspberries planted in solarized field plots. In the second growing season, total number and number of healthy primocanes of Qualicum plants were greater (P < 0.05) in solarized plots compared to nonsolarized plots. Solarization combined with applications of mefenoxam was no more effective in controlling diseases than solarization alone, but better than mefenoxam alone. Skeena plants responded similarly, but the differences were not significant. Red raspberry plants growing in solarized soil yielded more fruit than plants growing in nonsolarized soil in the third year after solarization. Solarization has potential as a component in an integrated pest management program of root diseases in raspberry and strawberry production, particularly within the first 2 years following planting.
Detection and Characterization of a Lethal Yellowing (16SrIV) Group Phytoplasma in Canary Island Date Palms Affected by Lethal Decline in Texas
Authors: Harrison N. A. , Womack M. , Carpio M. L.
Published: May 2007

Polymerase chain reaction (PCR) assays were used to detect phytoplasmas in Canary Island date (Phoenix canariensis) palms displaying symptoms similar to lethal yellowing (LY) disease in Corpus Christi, TX. An rDNA product (1.8 kb) was amplified consistently from 10 of 11 palms by PCR employing phytoplasma universal rRNA primer pair P1/P7. Also, AluI endonu-clease digests and sequencing of P1/P7 products revealed that nontarget Bacillus megaterium-related rDNA sequences of similar size were co-amplified along with phytoplasma rDNA from 10 palms. A 1,402-bp product was obtained from all 11 symptomatic palms when initial P1/P7 products were reamplified by PCR employing nested LY phytoplasma group-specific 16S rRNA primer pair LY16Sf/LY16Sr. Restriction fragment length polymorphism (RFLP) analysis of nested PCR products revealed that palm-infecting phytoplasmas were uniform and most similar to strains composing the coconut lethal yellowing phytoplasma (16SrIV) group. Sequence analysis of 16S rDNA determined the Texas Phoenix palm decline (TPD) phytoplasma to be phylogenetically closest to the Carludovica palmata leaf yellowing (CPY) phytoplasma. rDNA profiles of strains TPD and CPY obtained with AluI were co-identical and distinct from other known 16SrIV group phytoplasmas. On this basis, both strains were classified as members of a new subgroup, 16SrIV-D.
PCR Detection and RFLP Differentiation of Botrytis Species Associated with Neck Rot of Onion
Authors: Nielsen Karsten , Yohalem David S. , Jensen Dan Funck
Published: May 2007

Botrytis aclada and other Botrytis spp. can cause neck rot on onions, a storage disease that normally is very difficult to detect at harvest using traditional isolation techniques. Sequence characterized amplified region primers (BA2f/BA1r) were designed based on a previously cloned and amplified DNA fragment for direct amplification of isolates of Botrytis spp. associated with neck rot of onions. Digestion of the polymerase chain reaction (PCR) amplification product with the restriction enzyme ApoI makes it possible to distinguish the five groups: Botrytis aclada types AI and AII (B. allii); B. byssoidea; B. squamosa; and B. cinerea. The detection limit was 1 to 10 pg of pure fungal DNA. It was possible to detect B. aclada with the PCR method in artificially inoculated onion bulb tissue and in mature onion leaves showing no symptoms of the disease. The availability of a sensitive and specific PCR detection and identification method for Botrytis onion neck rot pathogens should facilitate ecological studies of this group of onion pathogens.
Occurrence of Impatiens necrotic spot virus in Ornamentals in Mahallat and Tehran Provinces in Iran
Authors: Shahraeen N. , Ghotbi T. , Mehraban A. H.
Published: May 2007

Impatiens necrotic spot virus (INSV) (genus Tospovirus, family Bunyaviridae) has been detected in commercial nurseries and field-grown ornamentals in Mahallat (Markazi) and Tehran provinces of Iran. INSV on ornamentals was first reported in 1990 (2). Ornamental plants with small necrotic spots, leaf yellowing, ring spots, necrotic vein clearing, wilting, and dwarf symptoms were collected. For mechanical inoculation on selected host species, leaf samples were triturated in chilled 0.01 phosphate buffer, pH 7.2, containing 0.02% sodium sulfite. Cowpea (cv. Mashad local), Chenopodium amaranticolor, Datura mete, Nicotiana rustica, N. tabacum (cv. White Burly), and Lycopersicon sp. produced local necrotic symptoms 5 days postinoculation. N. rustica, N. tabacum cv. White Burley, and D. metel also developed systemic mosaic symptoms that were followed by total wilting and death of the plant. The severity of the disease was higher in warm weather (July and August in greenhouses). Thrips tabaci and Frankliniella intonsa were often present at the site of INSV infection. Triple-antibody sandwich enzyme-linked immunosorbent assay (TAS-ELISA) was applied using a commerical polyclonal antibody kit (As-0115) in combination with monoclonal antibody 5E4 (As-0117) prepared against nucleoprotein of INSV isolate Pv-0280 (antibody kits and positive control were a gift from DSMZ, Braunschweig, Germany). Samples were tested for the presence of TSWV and INSV. The ornamental species found infected with INSV were Rosa sp., Gazania sp., Chrysanthemum sp., Leucanthemum sp., Matricaria camomila, Pelargonium roseum, Salvia sp., and Dianthus caryophyllus, which were collected from the Mahallat area; and Gazania sp. and Bougainvillea spectabilis collected from the Tehran Province. ELISA values of field-infected samples (OD405, read after 1h) diluted at 1:10 (wt/vol) were 0.317 (minimum) and 0.914 (maximum), and 0.312 for the positive control. None of the samples reacted in TAS-ELISA with Tomato spotted wilt virus (TSWV) (antibody kits, As-0105, As-0106, and As-01106, gift from DSMZ). A few samples of Chrysanthemum sp. and Leucanthemum sp. (collected from the Mahallat area) reacted in TAS-ELISA with TSWV, indicating they were doubly infected with TSWV and INSV. Within the genus Tospovirus the TSWV peanut isolate has been reported from Iran (1). To our knowledge, this is the first report of the occurrence of INSV on ornamentals in Iran.

References: (1) A. R. Golnaraghi et al. Plant Dis. 85:1286, 2001 (2) M. D. Law and J. W. Moyer. J. Gen.Virol.71:933, 1990.
First Report of Geotrichum candidum as a Pathogen of Sweetpotato Storage Roots from Flooded Fields in North Carolina and Louisiana
Authors: Holmes G. J. , Clark C. A.
Published: May 2007

In October 1997, samples of diseased sweetpotato (Ipomoea batatas (L.) Lam.) roots from storage were submitted for diagnosis to the Plant Disease and Insect Clinic at North Carolina State University. Two organisms were detected from soft rotted roots: Rhizopus stolonifer (Ehrenb.:Fr.) Vuill. (cause of Rhizopus soft rot) and Geotrichum candidum Link. Attempts to duplicate a soft rot by stab-inoculation of sweetpotato roots with a pure culture of G. candidum were unsuccessful. In Louisiana, following heavy rains due to Tropical Storm Frances in 1998, sweetpotato roots exhibiting a cortical tissue collapse at time of harvest were submitted to Louisiana State University for disease identification. Isolations from lesion margins consistently yielded G. candidum. Attempts to reproduce the disease by stab-inoculation produced only a few restricted lesions 5 to 15 mm in diameter. In 1999, rains from hurricanes Dennis, Floyd, and Irene caused extensive flooding in sweetpotato-growing areas of the North Carolina Coastal Plain. Extensive losses occurred in many fields due to a condition known as “souring,” and G. candidum was frequently detected sporulating on the surface of soured roots. This provided a clue for reproducing the disease artificially (1). In 2000, the disease was successfully reproduced. Sterile, wood toothpicks were dragged across a pure culture of G. candidum and inserted (1.5 cm deep) into the mid-section of sweetpotato (cv. Beauregard) roots. Roots were submerged in water at room temperature (23°C) for 24 to 48 h. Each of four roots was inoculated four times, and sterile toothpicks were stabbed into the controls. Additional controls consisted of an inoculated root that was not submerged in water, and a root that was not wounded or inoculated but submerged in water. Following submersion, roots were incubated at room temperature for 5 days. The experiment was repeated. Isolations from diseased tissues consistently yielded G. candidum. Symptoms consisted of slightly sunken, circular lesions, typically 15 to 50 mm in diameter. In cross-section, diseased tissue surrounding the wound was darkened, soft (but not watery), and extended 1 to 20 mm on either side of the wound. None of the controls showed signs of decay. These symptoms are consistent with but do not represent the full range of symptoms observed in the field. Souring of sweetpotato is likely the result of a complex of factors including predisposition of roots by water-saturated soil and the pathogenic effects of G. candidum. To our knowledge, this is the first known report of rot caused by G. candidum on sweetpotato in the United States. G. candidum was reported on sweetpotato in India, but no pathogenicity tests were reported (2).

References: (1) E. Cohen and J. W. Eckert. Plant Dis. 75:166, 1991. (2) N. C. Mandal and M. K. Dasgupta. Indian J. Mycol. Plant Pathol. 10:31, 1980.
First Report of Grapevine “Bois Noir” Disease and a New Phytoplasma Infecting Solanaceous Plants in Lebanon
Authors: Choueiri E. , Jreijiri F. , El Zammar S. , Verdin E. , Salar P. , Danet J. L. , Bové J. , Garnier M.
Published: May 2007

During a 2001 survey to evaluate the incidence of phytoplasma diseases in Lebanon, samples were collected from plants showing symptoms suggestive of phytoplasmal infections. Samples were also collected from symptomless plants. Sampled hosts from the Bekaa Valley included: 3 samples of tomato (Lycopersicum esculentum), 4 samples of pepper (Capsicum annuum), 10 samples of grapevine (Vitis vinifera) cvs. Chardonnay and Alicante Bouschet; 7 samples of ornamental periwinkle (Catharantus roseus) from the Tyr area; and 4 samples of weeds (Lactucca serratia). DNA was extracted from leaf midveins of diseased and symptomless plants, and from healthy periwinkle, grapevine, tomato, and pepper plants grown in a greenhouse in France. Polymerase chain reaction (PCR) with universal primers for the amplification of phytoplasma ribosomal RNA genes (3) only produced a 1.8-kbp rDNA fragment from symptomatic samples. The amplified DNAs were analyzed by restriction fragment length polymorphism (RFLP) with several restriction enzymes and sequenced. The analysis showed extracts of diseased grapevines, and two periwinkle plants had identical rDNA sequences and restriction profiles of the stolbur cluster (4). The sequences had 98% identity with two European stolbur isolates from grapevine and periwinkle (GenBank Accession Nos. X76428 and AF248959, respectively). In grapevine, the disease induced by the stolbur phytoplasma is “bois noir.” Bois noir is present in Europe where its incidence is predominant in northern vineyards and has been reported in Israel (2). To our knowledge, this is the first report of the stolbur/bois noir disease in Lebanon. In tomato and pepper, the restriction profiles and sequences of the phytoplasma rDNAs were identical. Sequencing and phylogenetic analysis indicated that the phytoplasma belonged to the clover proliferation (CP) cluster, as does the eggplant little leaf phytoplasma of solanaceous plants in Asia. They differed from the stolbur phytoplasma, known to infect solanaceaous plants in Europe. Lastly, a phytoplasma belonging to the pigeon pea witches' broom (PPWB) cluster was found in L. serratia and in some periwinkle plants. A phytoplasma of the PPWB cluster was recently shown to be responsible for an emerging lethal disease of almond trees in Lebanon (1).

References: (1) E. Choueiri et al. Plant Dis. 85:802, 2001. (2) X. Daire et al. Vitis 36:53, 1997. (3) B. Schneider et al. Pages 369–380 in: Molecular and Diagnostic Procedures in Mycoplasmology. Academic Press, NY, 1995. (4) E. Seemüller et al. J. Plant Pathol. 80:3, 1998.
First Record of Turnip mosaic virus Infecting Watercress in Venezuela
Authors: Marys E. , Carballo O.
Published: May 2007

During 2001, watercress (Rorippa nasturtium-aquaticum) plants displayed in vegetable markets located in the district capital, Caracas, showed severe leaf distortion, chlorosis, and mosaic. Viral etiology was suspected, and several plants were brought to the lab for further analyses. Electron microscopic studies of leaf-dip preparations from symptomatic samples revealed flexuous viral particles 750 nm long. Infected cells contained pinwheel inclusions and scrolls typical of those associated with infection by a potyvirus. The virus was sap-transmitted back to watercress, which developed symptoms identical to those first observed. Disease symptoms were also reproduced on Nicotiana benthamiana using mechanical inoculation with watercress-infected sap. All samples were tested by enzyme-linked immunosorbent assay, using polyclonal antibodies (Agdia, Elkhart, IN) to Turnip mosaic virus (TuMV), the only potyvirus that has been found infecting watercress plants (1). TuMV was detected in 88% of 100 samples taken from 18 markets on a single day. Symptoms were noted in every market when visited once a month during a 6-month period. The high percentage of TuMV-infected watercress in the 18 local markets (all 10 to 11 km from watercress fields) makes further epidemiological studies desirable. To our knowledge, this is the first report of TuMV infection of watercress in Venezuela.

References: (1) A. Brunt et al. Viruses of Plants. CAB International, Wallingford, Oxon, UK. 1996.
First Report of Stem Rot and Wilt of Sunflower Caused by Sclerotinia minor in Spain
Authors: Molinero-Ruiz M. L. , Melero-Vara J. M.
Published: May 2007

In 2001, sunflower (Helianthus annuus L.) plants with symptoms of stem and root rot and wilt were observed in Soria, Spain. Light brown, water-soaked lesions developed on the collar of infected plants and extended along the stem, affecting the pith and causing early and sudden wilt. White mycelium and sclerotia (0.5 to 2 mm long) formed in the pith of stems. The sclerotia were disinfested in NaClO (10% vol/vol) for 1 min, transferred to potato dextrose agar (PDA), and incubated at 20°C. The fungus consistently obtained was identified as Sclerotinia minor Jagger (1). Pathogenicity was confirmed in a greenhouse experiment (15 to 25°C, 13 h light). Seven-week-old plants of six genotypes of sunflower (‘Peredovik’, HA89, HA821, HA61, RHA274, and HA337) were inoculated by placing one PDA disk with active mycelial growth adjacent to each basal stem just below the soil line and covering it with peat/sand/silt (2:2:1, vol/vol). Six plants of each genotype were inoculated without wounding, and another six were inoculated immediately after stem base wounding with a scalpel; six wounded and uninoculated plants were used as controls. First symptoms (wilting) appeared 4 days after inoculation in all genotypes. Two weeks after inoculation, the percentage of dead plants ranged from 33 to 92% (depending on cultivar), white mycelium was observed at the base of affected plants, and sclerotia were present in the pith of diseased plants. There was no effect of plant wounding on disease incidence or severity, and the fungus was reisolated from inoculated plants. To our knowledge, this is the first report of S. minor in Spain.

Reference: (1) L. M. Kohn. Mycotaxon IX 2:365, 1979.
Natural Infection of Field-Grown Borage (Borago officinalis) by Alfalfa mosaic virus in Spain
Authors: Mallor C. , Luis-Arteaga M. , Cambra M. A. , Fernández-Cavada S.
Published: May 2007

Alfalfa mosaic virus (AMV) has a wide host range and is distributed throughout the world. It causes disease in several vegetable crops, including bean, celery, lettuce, pea, pepper, and tomato (1). In Spain, it has been found naturally infecting alfalfa, pepper, and tomato. During the autumn of 1999, in the area of Zaragoza (northeastern Spain), several plants expressing foliar yellow mosaic symptoms were observed in borage grown for human consumption in open field plots. The commercial value of the symptomatic plants was greatly reduced. The symptoms were similar to those previously obtained in greenhouse-grown borage plants mechanically inoculated with three tomato isolates of AMV (2). The following indicator species, including virus-free borage plants, were mechanically inoculated with sap from leaves of symptomatic borage plants, and reactions were recorded: chlorotic and necrotic local lesions on Tetragonia expansa and Vigna unguiculata; chlorotic local lesions and systemic mosaic on Chenopodium quinoa, C. amaranticolor, Cucumis sativus ‘Marketmore’, Gomphrena globosa, and Nicotiana glutinosa; systemic mosaic, sometimes associated with localized reactions, on Ocimum basilicum, Capsicum annuum ‘Doux des Landes’ and ‘Yolo Wonder’, N. benthamiana, N. clevelandii, N. rustica, N. sylvestris, N. tabacum ‘Paraguay’ and ‘Xanthi nc’, Petunia hybrida, Physalis floridana, and Solanum melongena ‘Cerna krazavitska’. The reactions are in agreement with the indicator host reactions described for AMV (1). Symptoms on virus-free borage plants mechanically inoculated with sap from symptomatic borage and from inoculated C. amaranticolor and O. basilicum experimental hosts were similar to those observed in naturally infected borage. Positive serological reactions (A405 values more than three times greater than those of the negative controls) in double-antibody sandwich enzyme-linked immunosorbent assay using commercially prepared antiserum against AMV (Agdia, Inc., Elkhart, IN) were obtained with extracts of naturally infected borage leaves and with systemically infected indicator species. Alfalfa plots located in the vicinity of the symptomatic borage plants could be the source of virus for borage infections. To our knowledge, this is the first report of natural AMV infection in Borago spp.

References: (1) E. M. J. Jaspars and L. Bos. CMI/AAB. No. 229, 1980. (2) M. Luis-Arteaga and J. M. Alvarez. Inf. Téc. Econ. Agr. 92:70, 1996.
First Report of Broad bean wilt virus 1 in Spain
Authors: Rubio L. , Luis-Arteaga M. , Cambra M. , Serra J. , Moreno P. , Guerri J.
Published: May 2007

In late summer 2001, field-grown pepper (Capsicum annuum) plants showing chlorotic blotching in leaves and fruits were observed in Benicarló, Castellón, Spain. Enzyme-linked immunosorbent assays of extracts of these plants with a collection of plant virus antisera showed a positive reaction only with Broad bean wilt virus serotype 1 (BBWV-1) antiserum. To confirm BBWV-1 infection, primers B1 (GCTCTTCCCCATATAACTTTC) and B2 (GTCTCTATCTTCTCTTCTTCC) were designed based on the nucleotide sequence of BBWV-1 isolate PV132 (GenBank Accession No. AB018702), and were used for reverse-transcription polymerase chain reaction analysis. RNAs extracted from symptomatic plants yielded a cDNA product of ~500 bp that was not obtained using RNA extracts from healthy plants. The sequence of this cDNA fragment was determined, and it showed ~80% nucleotide identity with a BBWV-1 genomic region, encompassing part of the two coat proteins genes. Amino acid identities were ~94% with BBWV-1 isolates and ~60% with BBWV-2 isolates. BBWV-1 and BBWV-2 are considered different species of the genus Fabavirus. BBWV-1 and BBWV-2 are distributed worldwide and infect a wide range of plants. In the Mediterranean Basin, BBWV-1 has been serologically identified in Jordan, Lebanon, Syria, Egypt, Tunisia, Morocco (2), and Italy (1), but no nucleotide sequence data is available. To our knowledge, this is the first report of BBWV-1 in Spain.

References: (1) M. G. Bellardi et al. Plant Dis. 81:959, 1997. (2) K. M. Makkouk et al. Neth. J. Plant Pathol. 96:291, 1990.
First Report of Stigmina lautii in the United States
Authors: Hodges C. S.
Published: May 2007

In June 1999, a specimen of blue spruce (Picea pungens) from Avery County, North Carolina, exhibiting symptoms of needle blight was submitted to the Plant Disease and Insect Clinic at North Carolina State University. A fungus sporulating profusely on symptomatic needles was identified as Stigmina lautii. Since then, three additional specimens have been received—on blue spruce from Ashe County, on Norway spruce (P. abies) from Avery County, and on Picea sp. from Cherokee County. These counties are all in western North Carolina but are not contiguous, indicating that the fungus is probably widespread in the western part of the state. S. lautii was described by Sutton (2) in 1973 on black spruce (P. mariana) and white spruce (P. glauca) collected from various locations in Manitoba and Saskatchewan, Canada. The only other reference found to the fungus is a specimen collected in British Columbia, Canada, on P. glauca in 1972 (2). The morphology of the North Carolina specimens of S. lautii is essentially as described by Sutton. The dark brown, superficial, flattened sporodochia are developed only through stomata. Sporodochia are found both on symptomatic needles as well as on adjacent green needles. Conidiophores arise only laterally from the lower, outer cells of the sporodochium, and are macronematous, mononematous, brown, smooth, unbranched, 1 to 2 septate, and 10 to 20 × 4 to 6 μm. Conidiogenous cells are brown, monoblastic, integrated, terminal, percurrent with 3 to 4 annelations, and 6 to 12 × 4 to 5 μm. Conidia are pale brown, cylindrical to fusiform, often curved, thick walled, verrucose, 5 to 8 distoseptate, and 25 to 45 × 5 to 6 μm. Superficially, the sporodochia of S. lautii might be confused with pycnidia of Rhizosphaera kalkhoffii, which also arise through stomata. The latter fungus also is associated with a needle blight of Picea spp. in western North Carolina. Both fungi were present on one specimen examined. Currently, no information is available on the pathogenicity of S. lautii, but its association with typical needle blight symptoms and the known pathogenicity of other Stigmina spp. on conifers make it likely that the fungus is pathogenic to spruce. To my knowledge, this is the first report of S. lautii in the United States, and P. pungens and P. abies represent new host records for the fungus. Specimens BPI 747910 and 840959, have been deposited in the herbarium of the National Fungus Collections, Beltsville, MD.

References: (1) J. H. Ginns. Page 158 in: Compendium of Plant Disease and Decay Fungi in Canada 1960-1980. Agric. Can. Publ. 1813, 1986. (2) B. C. Sutton. Mycol. Pap. 132:113, 1973.
Development of PCR-ELISA for Detection and Differentiation ofDidymella bryoniaefrom RelatedPhomaspecies
Authors: Somai B. M. , Keinath A. P. , Dean R. A.
Published: May 2007

The causal agent of gummy stem blight, Didymella bryoniae, often is isolated from infected cucurbits together with other Phoma spp. Polymerase chain reaction (PCR) primers specific to D. bryoniae and Phoma were used to develop and evaluate a microtiter-based PCR-enzyme-linked immunosorbent assay (ELISA) technique. Primers were modified by addition of a fluorescein and a biotin label to the 5′ ends of the forward and reverse primers, respectively. After amplification, PCR products were detected in an ELISA using horseradish peroxidase-conjugated antifluorescein antibody and three substrates that yielded three colored products, one for each fungal group. The most sensitive substrate (highest signal:noise ratio) was 2,2′ -azino-bis[3-ethylbenz-thiazoline-6-sulfonic acid]. PCR-ELISA successfully detected 45 of 46 D. bryoniae and all 13 Phoma isolates that were used. Results were comparable to those obtained with gel electrophoresis. Only one D. bryoniae isolate could not be detected with PCR-ELISA; this isolate also produced a fragment larger than other D. bryoniae isolates on agarose gels. PCR-ELISA was used successfully on crude extracts of “blind” fungal samples and identified seven of seven isolates as D. bryoniae or Phoma. Although less sensitive than gel electrophoresis, PCR-ELISA was a highly specific, yet simple, rapid and convenient assay for detection of D. bryoniae and Phoma sp.
Effect of Fungicides, Application Timing, and Canker Removal on Incidence and Severity of Constriction Canker of Peach
Authors: Lalancette Norman , Robison Dawn M.
Published: May 2007

The fungal plant pathogen Phomopsis amygdali, causal agent of constriction canker, initiates infections of peach twigs through petiole scars in fall and bud scale scars and flowers in spring. Fall fungicide treatments, consisting of seven to eight sprays during leaf abscission, reduced canker incidence by 45 to 63%. In contrast, spring applications consisting of four to five sprays from bud-break through bloom, provided only 10 to 28% control. When applied during both fall and spring, chlorothalonil (46 to 71% control) and captan (46 to 69% control) provided the lowest canker incidence and severity, followed by azoxystrobin (41% control) and myclobutanil (28 to 44% control). Removing cankers by pruning significantly reduced disease incidence by 42% 1 year but had no effect in another year. Possible causes for the inability of any treatment to achieve >90% disease control include: (i) none of the fungicides tested were highly effective against the pathogen, (ii) additional infections may have occurred outside the time period during which fungicides were applied, or (iii) use of single-tree plots surrounded by heavily infected nonsprayed trees. Also, the relationship between disease incidence and severity was quantified and observed to be the same for the two cultivars examined. When modeled using the power and quadratic functions, incidence explained 89% of the variation in severity.
Evaluation of Glycine max Germ Plasm for Resistance to Fusarium solani f. sp. glycines
Authors: Mueller D. S. , Hartman G. L. , Nelson R. L. , Pedersen W. L.
Published: May 2007

Sudden death syndrome, caused by Fusarium solani f. sp. glycines, has caused increased losses in soybean production in recent years. This study was done to identify potential sources of resistance to sudden death syndrome. Using a greenhouse screening procedure, 6,037 soybean plant introductions (PIs) were compared with a susceptible check, Great Lakes 3302, and two moderately resistant checks, PI 520.733 and PI 567.374, for resistance to sudden death syndrome. Only 57 PIs had foliar disease ratings that were not significantly different from PI 567.374 (P ≤ 0.05) 3 weeks after inoculation. Six PIs had lower ratings than PI 567.374 at 4 weeks after inoculation, while none had lower area under the disease progress curve (AUDPC) values. When comparing the PIs to PI 520.733, 209 PIs had foliar disease ratings not significantly different from PI 520.733 (P ≤ 0.05) 3 weeks after inoculation. Eight PIs had significantly lower disease severity ratings 4 weeks after inoculation, and 38 PIs had significantly lower AUDPC values than PI 520.733. Additionally, root lesion lengths were measured 4 weeks after inoculation and ranged from 25.2 to 41.5 mm for all the PIs; none of the entries had smaller lesion lengths than the susceptible check Great Lakes 3302. The correlation between lesion length and disease foliar severity rating was not significant. There also were no plant morphological characteristics (i.e., flower color or seed coat color) associated with higher sudden death syndrome foliar symptoms. Eighteen PIs previously identified as moderately resistant with differing agronomic traits were inoculated with five different isolates of Fusarium solani f. sp. glycines. Results indicated that resistance in these 18 PIs was effective against all five isolates of Fusarium solani f. sp. glycines. Isolate Mont-1 caused the greatest disease severity ratings. These PIs that exhibited low foliar severity ratings may provide new sources of resistance for the development of new sudden death syndrome-resistant lines and cultivars.
Identification of Phytoplasma Taxa and Insect Vectors of Peach Yellow Leaf Roll Disease in California
Authors: Blomquist C. L. , Kirkpatrick B. C.
Published: May 2007

Two peach diseases in California, western X-disease (WX) and peach yellow leaf roll (PYLR) are caused by two genetically distinct phytoplasmas. Based on symptoms alone, WX and PYLR cannot be reliably distinguished. The objectives of this study were to determine which phytoplasma was causing PYLR disease in peach orchards planted near pear orchards and which phytoplasmas were present in potential insect vectors captured in both peach and pear orchards. Leafhoppers and pear psylla were collected from yellow sticky traps placed in three pear orchards and four peach orchards located in the Sacramento Valley from 1994 to 1996. DNA was extracted from potential vectors and suspect diseased trees, and analyzed for the presence of the WX and PYLR phytoplasmas using strain-specific DNA hybridization or polymerase chain reaction (PCR) assays. The most abundant phytoplasma detected in diseased peach trees was the PYLR phytoplasma. In 1994 and 1995, 10 to 25% of groups of pear psylla tested positive for the PYLR phytoplasma, while no psylla groups tested positive for the WX phytoplasma. Only one captured leafhopper tested positive for the WX phytoplasma. These results indicate the pear psylla is the primary vector of PYLR in northern California.
Yield Responses of Direct-Seeded Wheat to Rhizobacteria and Fungicide Seed Treatments
Authors: Cook R. James , Weller David M. , El-Banna Adel Youssef , Vakoch Dan , Zhang Hao
Published: May 2007

Field trials were conducted with winter and spring wheat in eastern Washington and northern Idaho over several years to determine the benefit, as measured by grain yield, of seed treatments with rhizobacteria and formulated fungicides in cropping systems favorable to root diseases. The trials were conducted with wheat direct-seeded (no-till) in fields with a history of intensive cereals and one or more of the root diseases: take-all caused by Gaeumannomyces graminis var. tritici, Rhizoctonia root rot caused by Rhizoctonia solani AG8 and R. oryzae, and Pythium root rot caused mainly by Pythium irregulare and P. ultimum. The seed treatments included Bacillus sp. L324-92, Pseudomonas fluorescens Q69c-80, Pseudomonas fluorescens Q8r1-96, difenoconazole + metalaxyl (Dividend + Apron), difenoconazole + mefenoxam (Dividend + Apron XL = Dividend XL), tebuconazole + metalaxyl (Raxil XT), and tebuconazole + thiram (Raxil-thiram). Controls were nontreated seed planted into both nontreated (natural) soil and soil fumigated with methyl bromide just prior to planting. Although the data indicate a trend in higher wheat yields with two rhizobacteria treatments over the nontreated control (171 and 264 kg/ha, respectively), these higher yields were not significantly different from the nontreated control (P = 0.06). Fungicide seed treatments alone similarly resulted in yields that were 100 to 300 kg/ha higher than the nontreated control, but only the yield responses to Dividend on winter wheat (289 kg/ha) and Dividend + Apron on spring wheat (263 kg/ha) were significant (P ≤ 0.05). The greatest yield increases over the nontreated control occurred with certain rhizobacteria-fungicide combinations, with three treatments in the range of 312 to 486 kg/ha (6.1 to 17.7%; P ≤ 0.05). Some rhizobacteria-fungicide combinations brought average yields to within 85 to 90% of those obtained with soil fumigation. Only soil fumigation produced a measurable reduction in the incidence of take-all and Rhizoctonia root rot, as assessed on washed roots. No reliable method exists for visual quantification of Pythium root rot on wheat.
The Association of a Longidorus Species with Stunting and Root Damage of Loblolly Pine (Pinus taeda L.) Seedlings
Authors: Fraedrich Stephen W. , Cram Michelle M.
Published: May 2007

A Longidorus species was consistently associated with patches of stunted and chlorotic loblolly pine seedlings at a forest-tree nursery in Georgia. Seedlings from affected areas had poorly developed root systems that lacked lateral and feeder roots. Longidorus population densities in composite soil samples from the margins of patches ranged from 9 to 67 nematodes per 100 cm3 of soil. In a growth chamber experiment, seedling root dry weight decreased with respect to the initial Longidorus dose as well as the final Longidorus populations in containers. The dry root weight of seedlings were 0.117, 0.090, 0.066, and 0.065 g in containers initially infested with 0, 50, 100, and 200 Longidorus, respectively. Lateral and fine roots were lacking on seedlings at the highest doses. Populations of Longidorus increased in all containers during the experiment. Damage to loblolly pine seedlings caused by Longidorus is a previously undescribed problem in southern pine nurseries. Proper diagnosis of the problem by nematode testing laboratories may require the use of extraction techniques specific for larger nematodes such as Longidorus.
Two New Races of Phytophthora phaseoli from Lima Bean in Delaware
Authors: Evans T. A. , Davidson C. R. , Dominiak J. D. , Mulrooney R. P. , Carroll R. B. , Antonius S. H.
Published: May 2007

Downy mildew, incited by Phytophthora phaseoli Thaxt., is the most important disease of lima bean (Phaseolus lunatus L.) on the east coast of the United States. It has been a serious threat to commercial lima bean production in Delaware, Maryland, and New Jersey for the past 5 years. Growers have attempted to manage this disease using resistant cultivars and copper hydroxide fungicides. In August and September 1995, a new pathogenic race of P. phaseoli was isolated from infected pods of the lima bean cv. Packer in a production field near Milton, DE. Races of P. phaseoli are determined using a modification of a cultivar differential developed by Wester (3). The cv. 184–85, which is resistant to races A, B, C, and D (1), is susceptible to the new race, designated as E. In August 2000, another new pathogenic race of P. phaseoli was isolated from infected pods of cv. 184–85 near Middletown, DE. The lima bean line BG2-408, which is resistant to races A, B, C, D, and E, is susceptible to the new race, designated as F. Symptoms produced on lima bean plants infected by races E and F are similar to each other, and to those produced by all other races. All races of P. phaseoli have the same cultural characteristics on lima bean pod agar. Evaluations of in field weather station data and disease occurrence indicate that races E and F may have temperature maxima greater than 32°C, whereas race D has a maximum of less than 32°C (2). During the 2000 growing season, 118 isolates of P. phaseoli were collected from 44 production fields in Delaware and the eastern shore of Maryland, with 86% characterized as race E and 5% as race F.

References: (1) C. R. Davidson et al. Biol. Cult. Tests 2001:V80. (2) R. A. Hyre and R. S. Cox. Phytopathology 43:419, 1953. (3) R. E. Wester. Phytopathology 60:1856, 1970.