bluuebunny/crossref_metadata_2025 huggingface dataset:
Canopy Wetness and Humidity Prediction Using Satellite and Synoptic-Scale Meteorological Observations
Authors: Anderson M. C. , Bland W. L. , Norman J. M. , Diak G. D.
Published: May 2007

A method for predicting canopy wetness and humidity from remotely-acquired meteorological and radiation data is described. This method employs a surface energy balance model to scale from the above-canopy macroclimate to in-canopy microclimate conditions. Above-canopy temperature, vapor pressure, and wind speed inputs were obtained from objective analyses of hourly measurements from the synoptic weather network, while downwelling long- and shortwave radiation forcings were estimated from standard satellite observations. Precipitation (irrigation + rainfall) was the only input acquired in-field. Model predictions compared well with measurements of nighttime dew accumulation and relative humidity made in irrigated potato crops grown in central Wisconsin. Maximum dew amount measured in full canopies over four nights was reproduced to within 0.05 to 0.1 mm. The practical utility of this method to disease management was assessed by processing modeled and measured canopy microclimate data from two weather stations over three growing seasons through the BLITECAST disease forecasting system. Given the uncertainties inherent in the measurement of humidity, the model reasonably reproduced disease severity values generated from in-situ measurements in all but one case, where the canopy had suffered partial defoliation. Because the model simulates the microclimate within a healthy, uniform canopy, it may in many cases produce more reliable regional forecasts for plant disease than would a single set of in-situ measurements.
First Report of Xylella fastidiosa Infecting Coffee in Costa Rica
Authors: Rodríguez C. M. , Obando J. J. , Villalobos W. , Moreira L. , Rivera C.
Published: May 2007

In 1995, severe symptoms were observed on ‘Caturra’ and ‘Catuaí’ coffee (Coffea arabica L.) varieties in farms in the southern part of the Central Valley in Costa Rica. Symptoms were reduced leaf size, malformation of leaves, curling of leaf edges, shortening of internodes, and severe leaf chlorotic mosaic, which sometimes became necrotic. Abortion of flowers and young beans was also observed, with a reduction in yield. Plants also showed irregular growth with an atypical curling appearance that gave rise to the Spanish name “crespera.” Ten and three healthy plants were inoculated by grafting in the greenhouse, using infected and healthy budwoods, respectively. Approximately 6 months after inoculation, 3 of 10 grafted plants with infected budwoods showed symptoms of leaf chlorosis, curling, and malformation of leaves and bunched new flushes. Samples of 39 symptomatic plants collected from the field and samples of 3 healthy plants maintained in the greenhouse were tested by enzyme-linked immunosorbent assay (ELISA). All (100%) analyzed symptomatic samples were positive for X. fastidiosa, and all healthy controls were negative. The symptoms observed in Costa Rica are different from those described for coffee leaf scorch in Brazil (1,2), but the climatological conditions and soil type present in Costa Rica are also very different from the areas where X. fastidiosa occurs in Brazil. Leafhoppers were collected randomly in one of the most affected regions. Graphocephala permagna and Erythrogonia sonora were the most frequent insect species found associated with coffee. In ELISA, 34.5% (10 of 29) and 23.8% (5 of 21) of the collected specimens belonging to G. permagna and E. sonora, respectively, tested positive for X. fastidiosa. These positive ELISAs do not necessarily mean that the insect is a vector. The results presented here extend the known geographic distribution of X. fastidiosa. To our knowledge, this is the first report of X. fastidiosa in coffee in Costa Rica.

References: (1) M. J. G. Beretta et al. Plant Dis. 80:821, 1996. (2) de Lima et al. Plant Dis. 82:94, 1998.
Field Survey ofCucumber mosaic virusSubgroups I and II in Crop Plants in Costa Rica
Authors: Hord M. J. , García A. , Villalobos H. , Rivera C. , Macaya G. , Roossinck M. J.
Published: May 2007

Leaf samples were collected from cucurbit and solanaceous crop plants and Musa spp. in 28 locations in five provinces of Costa Rica during the period from January to October 1996. Sampling sites were selected in dry, humid, and moist tropical regions ranging in altitude from 50 to 2,100 m above sea level. RNA-enriched total nucleic acid solutions were spotted onto nylon membranes and hybridized to RNA probes specific for Cucumber mosaic virus (CMV) subgroups I or II. The presence of CMV was confirmed in 13 crops in 23 of the 28 sampling sites. CMV subgroup I was found to predominate in Costa Rica. CMV subgroup II was detected in the Atlantic region only, and in only 1 out of 113 CMV-positive samples.
Current Virulence of Pyrenophora teres on Barley in Western Australia
Authors: Gupta Sanjiv , Loughman Robert
Published: May 2007

Studies on variation, occurrence, and distribution of virulence in Pyrenophora teres are helpful to identify effective sources of resistance that can be used for barley breeding in Western Australia. Seventy-nine isolates of Pyrenophora teres were collected from different barley fields of Western Australia in 1995-96. Seventy-four induced net type symptoms (P. teres f. teres) and five induced spot type symptoms (P. teres f. maculata). Net type isolate responses on 47 barley lines were similar to the range of responses induced by nine historical isolates collected in the region between 1975 and 1985. These net type isolates were classified into two distinct groups based on virulence to the cultivar Beecher. Isolates were further classified into eight groups based on minor pathogenic variation among the population. The virulence phenotype present in an eastern Australian isolate was not observed in any isolates collected from Western Australia. An analysis of variance on a subset of 12 net type isolates indicated a significant line × isolate interaction (P < 0.001), with the interaction term variance component four times larger than the error variance. Based on these studies, the virulence among net type isolates has remained stable in Western Australia for the last 19 years. Spot type isolates were collected from a wider geographic area than previously reported and varied in virulence based on response to barley line Herta. Variation in spot-type isolates is reported for the first time from the region. The results from this study are being used in the development of resistant varieties.
Relationship Among Seed Size, Planting Date, and Common Root Rot in Hard Red Winter Wheat
Authors: Piccinni G. , Shriver J. M. , Rush C. M.
Published: May 2007

A dryland field study was conducted to determine the effect of seed size and planting date of hard red winter wheat on the severity of common root rot caused by Bipolaris sorokiniana (Sacc.) Shoemaker. Seed of cvs. Hawk, TAM 200, TAM 107, Scout 66, and Siouxland 89 were separated into three size categories of small, mixed, and large and were planted in the first weeks of September and October 1994 and 1995. Disease ratings for incidence and severity of subcrown internode infections were made in March and at harvest. At harvest, grain yields were collected. In both years of the study, there was no interaction between seed size and cultivars for any of the measured variables. Overall, seed size had no effect on disease severity or grain yield for either year. However, when sorted by planting date, plants from small seed yielded less than plants from other seed. October plantings showed lower disease indices than September plantings at the March evaluation. At the harvest disease evaluation, there were no differences in disease severity between planting dates for the first year but, in the second year of the study, plants from the October planting had lower disease than those from the September planting. There was no significant correlation among seed size, final yield, and disease index. The results of this study suggest that the expense of planting higher-quality certified seed cannot be justified for producing hard red winter wheat in dryland conditions in the Texas Panhandle, considering the current price of wheat and the average dryland yield.
Host Range Differences Between Populations ofPuccinia graminissubsp.graminicolaObtained from Perennial Ryegrass and Tall Fescue
Authors: Pfender W. F.
Published: May 2007

In the Pacific Northwest region of the United States, cool-season grasses grown for seed can be severely damaged by Puccinia graminis subsp. graminicola, causal agent of stem rust. Urediniospores of the pathogen, collected either from perennial ryegrass (Lolium perenne) or tall fescue (Festuca arundinacea), were tested for host range among selected grasses and cereals. Under greenhouse conditions, the inoculum from L. perenne could produce pustules on this host, as well as on Dactylis glomerata, Lolium multiflorum, Poa pratensis, and F. rubra subsp. rubra and subsp. commutata; it caused only limited pustule development (low incidence or pustule type) on F. arundinacea, F. ovina subsp. hirtula, P. annua, Hordeum vulgare, and Secale cereale. No symptoms were produced on Triticum aestivum or Avena sativa. The inoculum from F. arundinacea had a host range that included itself, D. glomerata, L. perenne, L. multiflorum, and F. rubra subsp. rubra and subsp. commutata; there was no sign of pustule development on Poa spp. or the cereal grains tested (T. aestivum, A. sativa, S. cereale, and H. vulgare). The two urediniospore populations differed also in rate of symptom development on most of their common hosts. There was a small, but statistically significant, difference in spore size among the populations from different hosts. No recommendation is made for separate taxonomic status of populations from F. arundinacea and L. perenne, but the adaptation of each to its own host should be considered when devising disease management strategies and studying host genetic resistance.
Bacterial Blight and Dieback of Eucalyptus Species, Hybrids, and Clones in South Africa
Authors: Coutinho T. A. , Preisig O. , Mergaert J. , Cnockaert M. C. , Riedel K.-H. , Swings J. , Wingfield M. J.
Published: May 2007

During 1998, a new disease appeared on trees representing a Eucalyptus grandis × E. nitens (GN) hybrid in a nursery in KwaZulu/Natal. The disease has subsequently spread to other Eucalyptus species, hybrids, and clones in nurseries and plantations throughout South Africa. Typical symptoms of the disease include dieback of young shoots and leaf blight. This ultimately leads to stunting of trees. The objective of this study was to isolate and identify the causal agent of the disease. A bacterium was consistently isolated from infected tissue. Pathogenicity tests were undertaken with a range of bacterial strains. Four pathogenic strains were selected from different geographical regions and Eucalyptus hosts for further study. The bacterium causing Eucalyptus leaf and shoot blight is gram negative and rod-shaped, varying in size from 0.5 to 0.75 μm wide and 1.0 to 2.0 μm long. Colonies of this bacterium have a yellow pigment. The results from the Biolog tests identified the bacterium as Pantoea agglomerans with a similarity index of 0.315. The 16S rDNA sequences of the purported Pantoea sp. were compared with those of other related Enterobacteriaceae from GenBank/EMBL. Phylogenetic analysis using PAUP revealed that the isolates group together with P. agglomerans, P. ananatis, and P. stewartii subsp. stewartii. The fatty acid profiles and phenotypic characteristics of the new pathogen are similar to P. ananatis, and % G + C is within the range of this species. DNA:DNA hybridization between the four strains and the type strain of P. ananatis conclusively showed that the bacterium causing blight and dieback of Eucalyptus in South Africa belongs to this species. This is the first report in which P. ananatis has been found as a causal agent of a disease on Eucalyptus.
First Report of Sclerotinia sclerotiorum on Campanula carpatica and Schizanthus × wisetonensis in Italy
Authors: Garibaldi A. , Minuto A. , Gullino M. L.
Published: May 2007

The production of potted ornamental plants is very important in the Albenga Region of northern Italy, where plants are grown for export to central and northern Europe. During fall 2000 and spring 2001, sudden wilt of tussock bellflower (Campanula carpatica Jacq.) and butterfly flower (Schizanthus × wisetonensis Hort.) was observed on potted plants in a commercial greenhouse. Initial symptoms included stem necrosis at the soil line and yellowing and tan discoloration of the lower leaves. As stem necrosis progressed, infected plants growing in a peat, bark compost, and clay mixture (70-20-10) wilted and died. Necrotic tissues were covered with whitish mycelia that produced dark, spherical (2 to 6 mm diameter) sclerotia. Sclerotinia sclerotiorum was consistently recovered from symptomatic stem pieces of both plants disinfested for 1 min in 1% NaOCl and plated on potato dextrose agar amended with streptomycin sulphate at 100 ppm. Pathogenicity of three isolates obtained from each crop was confirmed by inoculating 45- to 60-day-old C. carpatica and Schizanthus × wisetonensis plants grown in containers (14 cm diameter). Inoculum that consisted of wheat kernels infested with mycelia and sclerotia of each isolate was placed on the soil surface around the base of previously artificially wounded or nonwounded plants. Noninoculated plants served as controls. All plants were maintained outdoors where temperatures ranged between 8 and 15°C. Inoculated plants developed symptoms of leaf yellowing, followed by wilt, within 7 to 10 days, while control plants remained symptomless. White mycelia and sclerotia developed on infected tissues and S. sclerotiorum was reisolated from inoculated plants. To our knowledge, this is the first report of stem blight of C. carpatica and Schizanthus × wisetonensis caused by S. sclerotiorum in Italy. The disease was previously observed on C. carpatica in Great Britain (2) and on Schizanthus sp. in the United States (1).

References: (1) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN, 1989. (2) J. Rees. Welsh J. Agric. 1:188, 1925.
First Report of Septoria Spot on Bergamot
Authors: Agosteo G. E.
Published: May 2007

More than 95% of bergamot (Citrus bergamia Risso & Poit) essence production utilized in the international perfume industry comes from the coastal growing area in the Province of Reggio di Calabria in the Calabria Region of southern Italy. Fruit and leaf spots were observed on bergamot cv. Fantastico in some orchards during February and March 2001. Symptoms affected ≈20% of the fruits and resembled those caused by Septoria citri Pass. on lemon in the nearby Sicily Region (2). Symptoms on fruits were characterized by reddish-brown pits, 1 to 2 mm in diameter, often in proximity, and extending no deeper than the flavedo; or characterized by larger confluent brown spots, sunken and extending into the albedo. Leaf symptoms occurred on both sides of the blade and were characterized by irregular brown spots surrounded by a yellow halo. Spherical, dark-walled pycnidia were observed on brown spots on fruits. Pycnidia contained hyaline, nonseptate, or 1 to 3 septate, cylindrical conidia, rounded at the apex, measuring 8 to 18 × 1.5 to 2.0 μm (8 to 29 × 1.5 to 2.0 μm in pure culture), differing from the tapered conidia of S. citri. The fungus was subsequently identified as S. limonum Pass., a species first described in the 19th century on lemon in unheated glasshouses in northern Italy and later reported from other countries (3). It is still an open question whether S. limonum is distinct from S. citri. Previously, in fact, different species of Septoria from citrus have been considered synonyms of S. citri on the basis of isozyme electrophoretic phenotype (1). The fungus was isolated on artificial media from infected leaf and fruit tissues (pits and larger spots). Brown spot symptoms were reproduced by artificial inoculation of detached bergamot fruits. A spore suspension (1 × 106 spores per ml) of the fungus was sprayed on fruit wounded by a needle (1 mm in diameter) to a depth of 2 mm and washed in sterile water. After inoculation, the fruits were incubated 10 days at 22°C and 100% relative humidity. The fungus was reisolated from inoculated tissues. The damage caused by this disease appears to be more important on bergamot than on other citrus fruits since it affects oil-bearing tissue and consequently the production of essential oil.

References: (1) M. R. Bonde et al. Phytopathology 81:517, 1991. (2) S. Grasso and R. La Rosa. Riv. Patol. Veg. 19:15, 1983. (3) L. J. Klotz. Color Handbook of Citrus Diseases, 4th ed. University of California, Division of Agricultural Sciences, Berkeley, 1973.
First Report of Arceuthobium hondurense in Oaxaca, Mexico
Authors: Mathiasen R. , Nickrent D. , Daugherty C.
Published: May 2007

Honduran dwarf mistletoe (Arceuthobium hondurense Hawksw. & Wiens) has only been found in four locations in Honduras: west of Zamorano, east of Lepaterique, Cusuco National Park, and Celaque National Park (1,2). At one time it was believed that this mistletoe could be in danger of extinction (1). However, it has also been reported in two locations in Chiapas, Mexico (3). In December 2000, ≈1 km north of Suchixtepec, Oaxaca, Mexico, near Route 175 (elevation 2,770 m), we collected a dwarf mistletoe parasitizing Pinus tecunumanii (Schw.) Eguiluz et Perry that was morphologically similar to A. hondurense (1). This population initially had been classified as A. nigrum Hawksw. & Wiens (1), but is now classified as A. hondurense based on morphology (male flower color and stigma length) (1) and analysis of nuclear rDNA internal transcribed spacer (ITS) sequences from Honduras (GenBank Accession No. AF325969) and Oaxaca (GenBank Accession No. AY055215). A comparison of these two A. hondurense ITS sequences indicated they are very closely related to each other, whereas both are distinct from A. nigrum (GenBank Accession No. L25693). Specimens of A. hondurense from Oaxaca were deposited at the Deaver Herbarium, Northern Arizona University, Flagstaff. To our knowledge, this is the first report of A. hondurense in Oaxaca, Mexico, and extends its known distribution west across the Isthmus of Tehuantepec from central Chiapas by ≈400 km.

References: (1) F. G. Hawksworth and D. Wiens. Dwarf Mistletoes: Biology, Pathology, and Systematics. USDA Agric. Handb. 709, 1996. (2) R. Mathiasen et al. Phytologia 85:268, 1998. (3) R. Mathiasen et al. Plant Dis. 85:444, 2001.
First Report of Puccinia vincae on Vinca spp. in California
Authors: Hernández J. R. , Palm Hernández M. E. , Tidwell T.
Published: May 2007

In 2000, chlorotic leaves with inconspicuous leaf spots were observed on several Vinca major L. and V. minor L. plants in a 0.8-ha area in Woodside, CA. In August 2001, 80 to 90% of the plants were symptomatic. Uredinia measuring 2 to 3 × 1 mm were present on the lower surface of leaves. Urediniospores were ellipsoidal to oblong, 27 to 36 × 17 to 27 μm, with cinnamon-brown walls 1 to 2 μm thick, echinulate, and with three or four equatorial or slightly supraequatorial germ pores. Telia were produced in the uredinia. Teliospores were 1-septate, ellipsoidal to clavate, slightly constricted at the septum, and 34 to 45 × 19 to 30 μm. Teliospore walls were chestnut brown, 1.5 to 2.5 μm thick, and verrucose, with the verrucae sometimes in longitudinal lines. One germ pore covered by a hyaline papilla was present in each cell, at the apex in the upper cell and adjacent to the short, hyaline pedicel in the lower cell. The rust was identified as Puccinia vincae Berk. (1). P. vincae is widespread in Europe on Vinca species and is common on V. major in the eastern United States, Washington, and Idaho (2). To our knowledge, this is the first report of P. vincae on V. major in California (vouchers BPI 841363, 841364) and on V. minor in the United States (voucher BPI 841365).

References: (1) J. C. Arthur. Page 324 in: Manual of Rusts in the United States and Canada. Purdue Research Foundation, Lafayette, IN, 1934. (2) D. F. Farr et al. Pages 35 and 916 in: Fungi on Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN, 1989.
Origin of the Black Shank Resistance Gene, Ph, in Tobacco Cultivar Coker 371-Gold
Authors: Johnson E. S. , Wolff M. F. , Wernsman E. A. , Atchley W. R. , Shew H. D.
Published: May 2007

Flue-cured tobacco (Nicotiana tabacum) cultivar Coker 371-Gold (C 371-G) possesses a dominant gene, Ph, that confers high resistance to black shank disease, caused by race 0 of the soil-borne pathogen Phytophthora parasitica var. nicotianae. The origin of this gene is unknown. Breeding lines homozygous for the Ph gene were hybridized with NC 1071 and L8, flue-cured and burley genotypes known to possess qualitative resistance genes from Nicotiana plumbaginifolia and N. longiflora, respectively. The F1 hybrids were out-crossed to susceptible testers and the progenies evaluated in field black shank nurseries and in greenhouse disease tests with P. parasitica var. nicotianae race 0. Results showed that Ph was allelic to Php from N. plumbaginifolia in NC 1071. Testcross populations of hybrids between burley lines homozygous for Ph and L8, possessing Phl from N. longiflora, showed that Ph and Phl integrated into the same tobacco chromosome during interspecific transfer. Nevertheless, the two loci were estimated to be 3 cM apart. Random amplified polymorphic DNA (RAPD) analyses of the testcross progenies confirmed that recombination between the two loci was occurring. Forty-eight RAPD markers linked to Ph in doubled haploid lines were used in cluster analyses with multiple accessions of N. longiflora and N. plumbaginifolia, breeding lines L8, NC 1071, and DH92-2770-40, and cultivars K 326, Hicks, and C 371-G. A cladogram or region tree confirmed the data obtained from field and greenhouse trials, that Ph, transferred from C 371-G to DH92-2770-40, and Php in NC 1071 were allelic and originated from N. plumbaginifolia.
A Comparison of Maize Stalk Rot Occurrence in Bt and Non-Bt Hybrids
Authors: Gatch E. W. , Hellmich R. L. , Munkvold G. P.
Published: May 2007

Stalk rots, caused by a complex of fungal species, are among the most widespread and destructive diseases of maize. Larvae of the European corn borer (ECB) (Ostrinia nubilalis) promote stalk rot development by creating entry points for fungi, serving as vectors of pathogens, and causing physiological stress that may predispose plants to stalk decay. Field experiments were conducted in 1998, 1999, and 2000 to determine whether the use of transgenic Bt hybrids expressing insecticidal proteins would influence stalk rot symptoms (pith disintegration, pith discoloration, and lodging). Five hybrids representing different Bt types (or “Bt events”) (176, BT11, MON810, DBT418, and CBH351) were paired with their near-isogenic, non-Bt counterparts and subjected to treatments of manual and natural infestation with ECB larvae. Manual infestation resulted in significantly more ECB tunneling than natural infestation in 1998 and 1999 and significantly more lodging in 1998. There were significant linear correlations between ECB injury and stalk rot symptoms in non-Bt hybrids in 1998 and 1999, but not in 2000. A standard foliar insecticide treatment for ECB did not significantly affect stalk rot symptoms. In 1998, Bt hybrids had significantly less ECB tunneling, stalk discoloration, pith disintegration, and lodging compared with non-Bt hybrids, but these effects depended upon the Bt event and the infestation treatment. Similar but less pronounced effects of Bt events were observed in 1999. The 2000 results were more variable; the amount of pith disintegration was significantly lower but discoloration was significantly higher in the BT11 hybrid compared with its non-Bt counterpart, and the amount of lodging was significantly higher in the event 176 hybrid compared with its non-Bt counterpart. The ratio of stalk strength to grain weight did not consistently differ between Bt and non-Bt hybrids. These results indicate that, although specific Bt events in some years may cause reductions in stalk rot, the overall effect of Bt transformation on stalk rot occurrence is highly variable.
Potato Late Blight Management in the Toluca Valley: Field Validation of SimCast Modified for Cultivars with High Field Resistance
Authors: Grünwald Niklaus J. , Montes Gaspar Romero , Saldaña H. Lozoya , Covarrubias O. A. Rubio , Fry William E.
Published: May 2007

Management of potato late blight in the highland tropics is very costly and remains difficult. Reducing the impact of late blight through the use of resistant cultivars in combination with a fungicide forecasting system could lower the number of costly fungicide applications. Previously, we evaluated the fungicide advisory SimCast for use with Mexican cultivars of high levels of field resistance for use in the central highlands of Mexico and found that it predicted too many fungicide applications for cultivars of moderate to high levels of resistance. We adapted SimCast for cultivars with higher levels of resistance, and field validations conducted in 1999 and 2000 show that SimCast resulted in good disease control on cultivars ranging from susceptible to highly resistant. The number of fungicide applications forecast for cultivars with moderate to high levels of resistance was reduced. Precipitation was the environmental variable responsible for most of the forecasts made. Our work demonstrates that a predictive system can be portable from the temperate climate to a tropical highland climate. A user-friendly decision support system consisting of just a rain-gauge and the exclusive use of SimCast's fungicide units could be a valuable and affordable tool in managing potato late blight in the highland tropics.
First Report of Downy Mildew of Quinoa Caused by Peronospora farinosa f. sp. chenopodii in Denmark
Authors: Danielsen S. , Jacobsen S.-E. , Hockenhull J.
Published: May 2007

Downy mildew, caused by Peronospora farinosa (Fr.) Fr. f. sp. chenopodii Byford, is the most important disease of quinoa (Chenopodium quinoa Willd.) in the high mountainous areas of the Andes in South America (1), where the crop originated. While quinoa is not well known outside its traditional growing area, interest in this crop is increasing rapidly due to its high nutrient quality, many uses for human consumption, and agronomic characteristics of the plant; it is one of the most drought, salt, and frost tolerant crops known (2). From 1990 to 2001, several field trials were conducted in Denmark to study the performance of quinoa germ plasm of different origin under Danish conditions. Natural infection by downy mildew was observed each year on a range of cultivars, as well as on the common weed species, C. album L., which was observed growing near the quinoa. In 2001, 25 isolates of P. farinosa were collected from a field trial at the experimental station of the Royal Veterinary and Agricultural University in Taastrup, Denmark, from two Dutch quinoa cultivars (Carmen and Atlas) and one Danish breeding line (G205). Plants showed typical downy mildew symptoms: chlorotic lesions on the upper leaf surface and grayish spore masses on the lower leaf surface. Microscopic examination of the material showed the presence of dichotomously branched sporangiophores (200 to 400 μm long), which tapered to a blunt point and produced ellipsoidal, light brown sporangia with mean dimensions of 22 × 18 μm. The isolates were propagated and maintained by inoculation of detached quinoa leaves of two highly susceptible Peruvian cultivars (Toledo and Pandela) with a sporangium suspension (105 sporangia per ml), followed by incubation on water agar plates (10 to 15 leaves per plate) at 15°C and 12 h light/dark for 9 to 11 days. All isolates grew readily on these cultivars, and microscopic examination of the pathogen showed the same morphology as the original isolate. When the isolates were tested for their virulence on a range of quinoa cultivars with different geographic origin, specific interactions between host genotype and pathogen isolate were observed, measured as the degree of sporulation in the detached leaf assay, suggesting the presence of several pathotypes. To our knowledge, this is the first report of P. farinosa on quinoa in Denmark. Downy mildew should be considered as a potential problem for future large-scale quinoa production in Europe.

References: (1) S. Danielsen. (Abstr.) Phytopathology 90(suppl):S17, 2000. (2) N. W. Galwey. Biologist 36:267, 1989.
First Report of the Necrotic Strain of Potato virus Y (PVYN) on Potatoes in the Northwestern United States
Authors: Crosslin J. M. , Hamm P. B. , Eastwell K. C. , Thornton R. E. , Brown C. R. , Corsini D. , Shiel P. J. , Berger P. H.
Published: May 2007

More than 50 isolates of Potato virus Y (PVY) with characteristics of strains that cause tobacco veinal necrosis (PVYN) were obtained from potatoes (Solanum tuberosum L.) grown in the northwestern United States. These isolates are being characterized at the biological and molecular levels. Isolate RR1 was obtained from leaves of potato cv. Ranger Russet showing distinct mottling and leaf deformity, which is in contrast to the leaf-drop and necrosis usually observed with ordinary strains of PVY (PVYO) in this variety. Isolate AL1 was obtained from tubers of potato cv. Alturas showing distinct internal light brown rings and blotches. When RR1 and AL1 were transmitted to tobacco (Nicotiana tabacum L. cvs. Samsun NN and 423), they caused systemic veinal necrosis, including stem and petiole lesions typical of PVYN strains (2). Symptoms induced by RR1 and AL1 on tobacco appeared 9 to 11 days after inoculation, whereas some other isolates caused delayed veinal necrosis. All isolates that produced veinal necrosis on tobacco were detectable with PVY polyclonal antisera. Potato virus X was not detected by enzyme-linked immunosorbent assay in tobacco plants showing veinal necrosis. Some isolates, including AL1, failed to react in serological tests using PVYN-specific monoclonal antibodies obtained from three commercial sources. Other isolates, including RR1, were detectable with these monoclonal antibodies. Reverse transcription-polymerase chain reaction (RT-PCR) products obtained with primers specific for the coat protein (CP) open reading frame (ORF) were cloned and sequenced. AL1 possesses a CP more closely related to PVYO type isolates, which would account for its failure to react with PVYN monoclonal antibodies. In this regard, AL1 is similar to the PVYN-Wilga isolate (1). Other isolates that are detectable with the PVYN monoclonal antibodies possess a CP more consistent with N strains of the virus. Results of RT-PCR tests using primers derived from the P1 ORF sequence (3), and the restriction enzyme analysis and sequencing of the RT-PCR products, all suggest that AL1 and RR1 are related to European-type members of PVY tuber necrotic (NTN) or N strains. However, other isolates under investigation appear to be more closely related to previously reported North American NTN types (3). The symptomatology of these viruses on tobacco and potato, and the serological and molecular data clearly show that at least two distinct variants of PVYN have been found for the first time in a major potato production area of the United States, and pose a potential threat to the potato industry.

References: (1) B. Blanco-Urgoiti et al. Eur. J. Plant Pathol. 104:811, 1998. (2) J. A. de Bokx and H. Huttinga. Potato virus Y. Descriptions of Plant Viruses. No. 242, CMI/AAB, Surrey, England, 1981. (3) R. P. Singh et al. Can J. Plant Pathol. 20:227, 1998.
First Report of Colletotrichum acutatum on Strawberry in Bulgaria
Authors: Bobev S. G. , Zveibil A. , Freeman S.
Published: May 2007

Recently, there has been increasing interest in growing strawberries (Fragaria × ananassa) in Bulgaria. During the spring seasons of 2001 and 2002, progressive fruit damage in some producers' plots was observed in the Plovdiv Region. Appearance and development of symptoms were typical of anthracnose on aboveground plant structures. On immature fruits, lesions were single or in groups of two or three, circular, small (1 to 3 mm), sunken, and dark brown to black. Lesions on ripe fruits were similar in shape and color, larger (10 to 15 mm), and when coalesced, they covered most or the entire surface. Elliptical, sunken lesions with lighter centers were also found on petioles and stolons, and blighted flowers and infected immature fruits became dark in color. Under wet conditions, salmon-colored masses of conidia were produced mainly on mature but also on unripe fruits, and on petioles and stolons. Conidia were hyaline, cylindrical, and attenuated at both ends measuring 11.5 (9.2 to 13.3) × 4.5 (4.2 to 5.0) μm (2). Colonies of the isolated fungus growing on potato dextrose agar were white with mycelium becoming gray and aerial. Symptoms were reproduced by artificial inoculation of healthy, ripe strawberry fruits. Fruits were wounded with a sterile scalpel, and 5-mm plugs of agar cultures of two isolates were placed on each wound (12 fruits per isolate). An equal number of wounded and noninoculated fruits were used as a control. Fruits were kept in a humidity chamber at 25°C, and 3 to 5 days later, necrotic sunken zones containing acervuli were observed around the wounds of inoculated fruits, and the pathogen was subsequently reisolated. Identical symptoms were obtained after inoculation of raspberry fruits. Intact strawberry stolons and stalks were also successfully inoculated in the lab with two additional isolates using the same technique and tightly covering wounds with adhesive tape. No symptoms were found in the controls of all tests. On the basis of symptoms and pathogen characteristics, the disease was confirmed as anthracnose (black spot) caused by Colletotrichum acutatum. Additionally, the identity of six isolates was confirmed as C. acutatum by species-specific polymerase chain reaction amplification resulting in a single fragment of 490 bp using primers ITS4 and CaInt2 (1). To our knowledge this is the first report of C. acutatum on strawberry in Bulgaria.

References: (1) S. Freeman et al. Pathogenic and non-pathogenic lifestyles in Colletotrichum acutatum from strawberry and other plants. Phytopathology 91:986, 2001. (2) P. S. Gunnell, and W. D. Gubler. Taxonomy and morphology of Colletotrichum species pathogenic to strawberry. Mycologia 84:157, 1992.
First Report of Zonate Leaf Spot of Artocarpus altilis Caused by Cristulariella moricola in Taiwan
Authors: Hu B. Y. , Hsiao W. W. , Fu C. H.
Published: May 2007

Breadfruit (Artocarpus altilis (Parkinson) Fosberg) is an important landscape and garden tree in Taiwan. During the spring of 2002, zonate leaf spots of breadfruit were observed at a Taipei nursery in northern Taiwan. Initially, several small, brown, zonate lesions developed on leaves. As lesions enlarged, they coalesced, leading to blighting of leaves and premature defoliation. Sporophores on the host were generally hypophyllous but sometimes amphigenous, solitary, erect, easily detachable, and as much as 850 μm long. The upper portion of the sporophore is considered an individual conidium and consisted of a pyramidal head that was fusiform to ventricose and cristulate, 495 to 534 μm long and 210 to 290 μm wide at the broadest point. Branches within the pyramidal head were short and compact, and dichotomously or trichotomously branched. The conidia were hyaline, broad, septate, tapering toward an acute apex, and sometimes constricted at the basal septum. Conidiophores were 400 to 680 × 20 to 100 μm. The fungus was isolated from infected tissue and maintained on potato dextrose agar (PDA). Sclerotia were produced on PDA after 4 to 5 weeks at 20°C without light, but conidia were not observed in culture. The fungus was identified as Cristulariella moricola (Hino) Redhead based on morphological characteristics (1,2). To complete Koch's postulates, three sporophores from infected leaves or three sclerotia from cultures were placed individually on each of 10 breadfruit leaves. The plants were placed in plastic bags and incubated at 16 to 20°C. Symptoms were observed after 2 to 3 days on 100% of plants inoculated with sporophores and after 6 days on 50% of plants inoculated with sclerotia. The pathogen was reisolated from lesions on plants inoculated with sporophores and sclerotia. No symptoms were observed on the control plants. C. moricola has been known to cause a bull's eye or zonate leaf spot and defoliation on woody and annual plants, including at least 51 host species and 36 families distributed in the central and eastern United States (1). To our knowledge, this is the first report of zonate leaf spot and defoliation of breadfruit caused by C. moricola.

References: (1) T. T. Chang. Bull. Taiwan For. Res. Inst. New Ser. 10 (2):235, 1995. (2) S. A. Redhead. Can. J. Bot. 53:700, 1975.
Comparison of Drip and Sprinkler Irrigation Systems for Applying Metam Sodium and Managing Stem Rot on Potato
Authors: Browne G. T. , DeTar W. R. , Sanden B. L. , Phene C. J.
Published: May 2007

Drip and sprinkler systems were compared for effectiveness as preplant metam sodium chemigation systems and conduciveness to late-season development of stem rot disease on potato. Sclerotia of Sclerotium rolfsii were used in a bioassay to test efficacy of metam sodium treatments. Drip application of metam sodium (532 liters/ha, 32.8% a.i.) through lines at 7 cm of depth in preformed beds (depths from bed top unless stated otherwise) killed all test sclerotia at 15-, 30-, or 46-cm depths. Drip application of the metam sodium through drip lines at 41 or 46 cm of depth resulted in 0 to 17 or 68 to 80% survival, respectively, of test sclerotia at 15 cm of depth; but all the sclerotia at 30 or 46 cm of depth were killed. Compared with the drip applications, sprinkler chemigation with metam sodium generally treated beds less effectively (8 to 100% of sclerotia survived at 15 cm, 62 to 100% at 30 or 46 cm). On flat ground, drip and sprinkler chemigation (metam sodium, 560 liters/ha) performed equally (4, 37, and 77% survival at 15-, 45-, and 75-cm depths, respectively). After potato planting and artificial soil infestation with S. rolfsii (5 to 6 weeks before harvest), subsurface drip-irrigated plots (line depth of 41 or 46 cm) had lower incidence of stem rot disease at harvest (13 to 23% on tubers) than that in sprinkler plots (56 to 62%). The low incidence of disease was associated with relatively dry surface soil. Subsurface drip chemigation with metam sodium in preformed plant beds does not consistently eradicate S. rolfsii sclerotia near the upper bed surface but, in an arid climate, it is less conducive than sprinkler irrigation to development of stem rot disease of potato.
Reactivation of Bentgrass Dead Spot and Growth, Pseudothecia Production, and Ascospore Germination of Ophiosphaerella agrostis
Authors: Kaminski J. E. , Dernoeden P. H. , O'Neill N. R. , Momen B.
Published: May 2007

Ophiosphaerella agrostis incites bentgrass dead spot (BDS) of creeping bentgrass. Little is known about the biology of O. agrostis; hence the primary goal of this study was to determine some basic biological properties of the pathogen and epidemiological components of the disease. Winter-dormant creeping bentgrass field samples showing symptoms of BDS were incubated at temperatures ranging from 15 to 30°C. Between 12 and 28 days of incubation, reactivation of BDS symptoms occurred at temperatures ≥20°C, but the greatest expansion in BDS patch diameter occurred at 25 and 30°C. The optimum temperatures for growth of hyphae among 10 O. agrostis isolates ranged from 25 to 30°C, and growth was suppressed at 35°C. Pseudothecia of O. agrostis were produced in vitro on a mixture of tall fescue seed and wheat bran. Pseudothecia developed under constant fluorescent light at 13 to 28°C, but no pseudothecia developed in darkness at any temperature. Pseudothecia developed in as few as 4 days, but the highest numbers appeared about 30 days after incubation began. Ascospores incubated at 25°C germinated in as little as 2 h, with germ tubes generally emerging from the terminal rather than interior cells of ascospores. Germination during the first 4 h of incubation was enhanced by both light and the presence of bentgrass leaves or roots. After 18 h of incubation, however, there were few differences in the percentage of ascospores germinated regardless of light treatment or presence of plant tissue.
Evaluation of Postharvest Removal of Sooty Blotch and Flyspeck on Apples Using Sodium Hypochlorite, Hydrogen Peroxide with Peroxyacetic Acid, and Soap
Authors: Batzer J. C. , Gleason M. L. , Weldon B. , Dixon P. M. , Nutter F. W.
Published: May 2007

Postharvest dips of apples (Malus × domestica) in commercial disinfestants were used to remove signs of the flyspeck (FS) pathogen, Schizothyrium pomi, and the sooty blotch (SB) complex (Peltaster fructicola, Leptodontium elatius, and Geastrumia polystigmatis). Apples were dipped for 7 or 15 min in buffered sodium hypochlorite (Agclor 310 plus Decco 312 Buffer) at 200, 400, 500, 600, or 800 ppm chlorine, a mixture of hydrogen peroxide and peroxyacetic acid (Tsunami 100) at 60 ppm/80 ppm, 120 ppm/160 ppm, or 360 ppm/480 ppm, respectively, or soap (Kleen 440), then brushed and rinsed for 30 s on a commercial grading line. Disease severity was assessed as percent diseased area using a quantitative rating system, and by counting the number of colonies of three mycelial types of SB and FS. Percent diseased area on apples was converted to USDA apple grade ratings and retail values. Both assessment methods provided similar results, but the percent-diseased-area method was less labor intensive. A 7-min dip in 800 ppm chlorine resulted in a mean increase from 25 and 55% to 100% Extra Fancy grade for ‘Jonathan’ and ‘Golden Delicious’ apples, respectively, and increased market value by 31 and 14%, respectively. The 7-min, 200-ppm chlorine dip resulted in an increase from 28 and 45% to 92.5 and 96.5% Extra Fancy after treatment for ‘Jonathan’ and ‘Golden Delicious’, respectively. Blemishes were removed more effectively from ‘Jonathan’ and ‘McIntosh’ apples than from ‘Golden Delicious’. Mycelial types of the sooty blotch and flyspeck fungi were removed differentially by the disinfestant dip treatments.
Sources of Resistance to Colletotrichum lindemuthianum in the Secondary Gene Pool of Phaseolus vulgaris and in Crosses of Primary and Secondary Gene Pools
Authors: Mahuku George S. , Jara Carlos E. , Cajiao César , Beebe S.
Published: May 2007

Use of genetic resistance is the most practical and economic way to manage anthracnose of common bean. Colletotrichum lindemuthianum, the causal agent of bean anthracnose, is a highly variabile pathogen, and there are no host resistance genes that are effective against all known races of the pathogen. To diversify sources of resistance, we screened the core collection of the secondary gene pool of Phaseolus spp. and interspecific lines derived from simple and complex crosses of primary and secondary genotypes for their resistance to anthracnose. High levels of resistance were observed in the secondary gene pool. None of the 162 accessions tested was susceptible to C. lindemuthianum. Of the two species composing the secondary gene pool, P. polyanthus displayed higher levels of resistance than P. coccineus, and all accessions tested were resistant. The response of P. coccineus was more variable, with six genotypes showing an intermediate reaction. Among the 75 lines from interspecific crosses, 49 were resistant to the three races (races 6, 15, and 3481) used in this study, and higher levels of resistance were found in lines that had P. polyanthus as one of the parents in the crosses than in the lines derived from P. coccineus. These lines constitute a valuable source of resistance and may aid in the development of stable resistance to anthracnose.
A Twig Canker on English Hawthorn Caused by Coniothyrium sporulosum in Italy
Authors: Montecchio L. , Causin R. , Vettorazzo M.
Published: May 2007

Large, open, irregularly shaped cankers on trunks and twigs of 4- to 12-year-old Crataegus monogyna Jacq. in a mixed oak forest in northern Italy were observed in 2001. Radial sections through the cankers, which often occurred at sites of hail damage from the previous year, showed a brown discoloration in the xylem. Foliage distal to the cankers became chlorotic, wilted, and finally died. When the disease was severe, the entire top of the plant died, and epicormic shoots developed below the cankers. Fruiting bodies were not present on the canker surface, and symptoms were not observed on root collars or roots. Microscopic examination of cankers showed that vessels frequently contained mycelium. Five symptomatic plants were selected, and from each of these plants isolations were made from one canker. Two chips, 3 mm wide, were cut from the necrotic margin of each canker, superficially sterilized with sodium hypochlorite, rinsed, plated on potato dextrose agar (PDA), and incubated at 20 ± 1°C for 8 days in the dark. Among a variety of microorganisms isolated from the necrotic tissues, Fusarium solani (Mart) Sacc. and Coniothyrium sporulosum (Gams & Domsch) van der Aa (1,2) were isolated from 70 and 100% of the chips, respectively. Artificial inoculations were made on 3-year-old, container-grown Crataegus monogyna seedlings obtained from the same seed stock using two isolates each of the two fungi. Where the stems measured 5 mm in diameter, the bark was surface sterilized with sodium hypochlorite, rinsed, wounded with a 2-mm-diameter cork borer, inoculated with a PDA disk containing mycelium and spores, and the wound sealed with Parafilm. Controls were treated the same but using sterile discs of PDA. Each treatment was replicated on five seedlings, incubated in the greenhouse (20 ± 2°C, 80% relative humidity, and 12-h natural light per day) for 60 days. After 20 days, the 10 plants treated with C. sporulosum showed small necrotic lesions, which developed into small patches of dead bark that cracked and formed spindle-shaped cankers. Radial sections through the stem at the canker site from four of the inoculated plants showed the presence of mycelium in the vessels, and C. sporulosum was reisolated from the infected tissue. After 60 days, the cankers measured as much as 22 mm, and the microscopic observations on the remaining six plants confirmed the presence of the fungus. No disease symptoms or mycelium in the inner tissues were observed for control plants, or plants inoculated with Fusarium spp. The present work adds the genus Crataegus to the wide list of hosts (e.g., Rubus, Malus, Quercus, Picea, Taxus, Juniperus, Chamaecyparis, Cupressocyparis, and Mahonia) susceptible to C. sporulosum, which may act as an important pathogen under forest conditions, in orchards, and in breeding programs.

References: 1) W. Gams and K. H. Domsch. Nova Hedwigia, 18:1, 1969. 2) I. Vegh and A. Le Berre. Pepinieristes Hort. Maraich. Rev. Hortic. 331:11, 1992.