bluuebunny/crossref_metadata_2025 huggingface dataset:
First Report of Ascochyta Blight of Chickpea in Latin America
Authors: Kaiser W. J. , Coca W. F. , Vega O. S.
Published: May 2007

Chickpea (Cicer arietinum L.) has been cultivated in different regions of Bolivia for hundreds of years. In the highlands (2,400 to 3,000 m above sea level) of the Department (state) of Chuquisaca in southern Bolivia, chickpea is an important cash crop for small farmers. During March through April 1999, a blight was observed infecting local chickpea landraces in Chamicle, Escana, Kullpa Ckasa, Presto, Q'ara Puncu, Santa Rosalia, Sucre, and Yotala in Chuquisaca, and its cause was tentatively identified as Ascochyta rabiei (Pass.) Labrousse (teleomorph Didymella rabiei (Kovachevski) v. Arx) based on disease symptomatology. Stems, leaflets, and pods of infected plants exhibited abundant necrotic lesions. Isolations were made from lesions on leaflets, stems, pods, and seeds of infected plants on 2% water agar and potato dextrose agar. The fungus was isolated from the foliar and reproductive tissues of infected plants. Koch's postulates were fulfilled by inoculating the foliage of 15-day-old seedlings of a local chickpea landrace with spore suspensions of three isolates of the pathogen from Escana, Santa Rosalia, and Sucre. Inoculated and control (sterile water) plants were incubated in moist chambers for 4 days in the laboratory at ambient temperatures and under natural daylight. The fungus was reisolated from lesions that developed on the leaflets, petioles, and stems of all inoculated seedlings but not from tissues on any of the noninoculated control plants. The fungus was identified as A. rabiei based on symptoms, cultural and morphological characteristics (2), and pathogenicity tests. Above average rainfall and cool weather during March and April favored development and spread of the disease in many chickpea-growing areas. Severe infection usually resulted in dieback and death of plants and reduced yields. Additionally, A. rabiei was isolated from chickpea seeds purchased in the markets of Sucre and Monteagudo and in seeds used by farmers in Escana to plant the 1999 crop (which had supplied the plants previously observed with blight). The teleomorph did not develop on naturally infested chickpea debris from five locations when incubated over the winter on the soil surface in Sucre. Based on farmers' reports, it appears that Ascochyta blight of chickpea has been present in the Department of Chuquisaca and possibly other Bolivian departments for many years. This is the first report of the disease in either Bolivia or other countries of Latin America (Mexico and Central and South America) (1).

References: (1) CAB. 1991. CAB Distribution Maps of Plant Diseases: Ascochyta rabiei. Map No. 151. CAB International Mycological Institute, Wallingford, England. (2) E. Punithalingham and P. Holliday. 1972. Ascochyta rabiei. Descriptions of Pathogenic Fungi and Bacteria No. 337. Commonwealth Mycological Institute, Kew, England.
Downy Mildew of Stock, Caused by Peronospora parasitica, in California
Authors: Koike S. T.
Published: May 2007

During the spring and fall of 1999, commercial plantings of the cut flower stock (Matthiola incana) in coastal regions of California developed a severe foliar disease. Abaxial leaf surfaces supported the extensive white fungal growth typical of a downy mildew. Adaxial surfaces of newly infected leaves did not show symptoms, but with time, leaves exhibited extensive, diffuse chlorotic areas and slight twisting. Infected plants were not acceptable for the cut flower market and, therefore, were not harvested. Sporangiophores had main trunks with dichotomous branches ending in slender curved tips that were 2.8 μm long. Sporangia were ovoid, measuring 22 to 25 μm long and 19 to 22 μm wide. The fungus was identified as Peronospora parasitica. Pathogenicity was established by gently pressing diseased leaves onto stock plants (cv. Avalanche), incubating plants in a humidity chamber (20 to 22°C, 100% relative humidity) for 48 h, and keeping plants in a greenhouse. Diffuse chlorotic leaf symptoms developed after 10 days, and the same fungus later developed on abaxial surfaces. Uninoculated plants did not develop downy mildew. Inoculations were conducted a second time, and the results were the same. This is the first documentation of P. parasitica on stock in California.
Evaluation of Dasypyrum villosum Populations for Resistance to Cereal Eyespot and Stripe Rust Pathogens
Authors: Yildirim A. , Jones S. S. , Murray T. D. , Line R. F.
Published: May 2007

Resistance to Pseudocercosporella herpotrichoides (cause of eyespot) and Puccinia striiformis(cause of stripe rust) was evaluated in a germ plasm collection of Dasypyrum villosum (syn. Haynaldia villosa) and a set of disomic addition lines, a substitution, and a translocation line of D. villosum chromosomes in a wheat background. Three races of P. striiformis and a β-glucuronidase-transformed strain of Pseudocercosporella herpotrichoides were used to inoculate plants and evaluate disease reactions. Of the 115 D. villosum accessions tested, 33 (28.6%) were resistant to one or more races of Puccinia striiformis and 8 accessions were resistant to all races. All 219 accessions of D. villosum tested were resistant to Pseudocercosporella herpotrichoides and 158 (72%) of the accessions had lower β-glucuronidase activity than the resistant wheat line VPM-1. Most of the accessions of D. villosum resistant to the stripe rust pathogen originated from Greece; however, there was no distinction among origins for resistance to the eyespot pathogen. Chromosome 4V was confirmed to carry the gene for resistance to P. herpotrichoides. At least one gene for resistance to Puccinia striiformis was located on the short arm of chromosome 6V of D. villosum in the 6VS/6AL-translocation line; this gene was named Yr26.
The Effect of Previous Crop Residues and Tillage on Fusarium Head Blight of Wheat
Authors: Dill-Macky R. , Jones R. K.
Published: May 2007

Effects of previous crop residues and tillage practices on Fusarium head blight (FHB) of wheat were examined. Fusarium head blight was monitored in plots of the FHB-susceptible spring wheat cultivar Norm following crops of corn, wheat, and soybeans in 1995, 1996, and 1997. Moldboard plow, chisel plow, and no-till treatments were imposed perpendicular to crop strips to establish a range of residue levels in each of the previous crop residues. Fusarium head blight incidence and severity were greatest when wheat followed corn and least when wheat followed soybeans. Incidence and severity were lower in moldboard plowed plots than in either chisel plowed or no-till plots, although differences among chisel plow and no-till treatments were not apparent. Yields of wheat were approximately 15% lower in plots where wheat followed corn or wheat than in wheat following soybeans and were 10% greater in moldboard plowed plots than in either chisel plowed or no-till treatments. The deoxynivalenol (DON) content of harvested grain was significantly correlated with FHB incidence and severity. The DON level in wheat following soybeans, averaged across tillage treatments, was 25% lower than in wheat following wheat and 50% of the level in wheat following corn. These findings suggest that changes in regional tillage practices, principally the move toward conservation tillage and reduced-till systems, contributed to the recent FHB epidemics in the Upper Midwest. Because differences in the type and quantity of crop residues in small plots affected disease development, it is likely that local sources of inoculum, such as those within a grower's field, contribute directly to the inoculum load and disease potential. The implication of these findings is that selection of cultural practices aimed to reduce inoculum-borne residues will assist in the control of FHB.
Determination of Optimum Irrigation Regime and Water Use Efficiency of Sugar Beet Grown in Pathogen-Infested Soil
Authors: Piccinni G. , Rush C. M.
Published: May 2007

A field experiment was conducted to quantify the effects of different irrigation frequencies on sugar beet yield in pathogen-infested soils. Four irrigation regimes (every 2, 3, 4, and 5 weeks) and four inoculation treatments (beet necrotic yellow vein virus [BNYVV], beet soilborne mosaic virus [BSBMV], BNYVV+BSBMV, and a noninoculated control) were arranged in a split-plot design and replicated four times. Irrigation frequency and virus infection affected disease severity and yield. Sugar beets irrigated every 4 weeks had the lowest disease severity, and yield was not significantly different from the every 2 weeks frequency. Sucrose content was higher for beets in the 4-week irrigation treatment compared with the 2- and 3-week frequencies. Beets inoculated with BNYVV had higher disease severity and lower root yield than beets inoculated with BSBMV and BNYVV+BSBMV. A greenhouse experiment was conducted to evaluate the effect of water level on disease severity and water use in sugar beet. Four treatments (BNYVV, BSBMV, BNYVV+BSBMV, and a noninoculated control) and three water levels (pot capacity [PC], 75% PC, and 50% PC) were arranged in a split-plot design and replicated five times. Pots of each treatment were weighed every other day to determine evapotranspiration. Evaporation was determined from unplanted pots, and plant transpiration was calculated by the difference. Beets irrigated at 75% pot capacity showed minimal disease incidence and a root weight comparable to the fully irrigated healthy control. Plants in the BNYVV treatment had a significantly higher disease severity than beets infected by BSBMV or BNYVV+BSBMV. Root weights and plant water use were significantly affected by virus infection. Beets in the BNYVV+BSBMV treatment had a significantly higher root dry weight and water use than beets in the BNYVV treatment, suggesting that BSBMV reduced the impact of disease caused by BNYVV.
Factors Affecting Concentrations of Airborne Conidia of Oidium sp. Among Poinsettias in a Greenhouse
Authors: Byrne J. M. , Hausbeck M. K. , Shaw B. D.
Published: May 2007

Atmospheric concentrations of Oidium sp. conidia in two research greenhouses containing infected poinsettias were monitored to investigate the role of environment in prompting conidial release and dissemination. Hourly concentrations of conidia of Oidium sp. were estimated using a Burkard volumetric spore sampler. The influence of temperature on disease development was studied by placing healthy poinsettias in each greenhouse for 7-day periods, removing them, and recording the days to the appearance of the first colony. When averaged over 5 December to 1 June, atmospheric conidial concentrations in greenhouse (GH) 2 were greatest during 1000 to 1800 hours with a peak (325 conidia/m3/h) occurring at 1200 hours. In GH 11, peak concentrations occurred at 1300 hours (65 conidia/m3/h) and 1600 hours (75 conidia/m3/h). Large numbers of conidia were sampled (≥100/m3) within 1-h periods, indicating conidial release events (CREs). Fluctuations in relative humidity (RH) (either positive or negative) prompted CREs. In both greenhouses, the highest number of CREs (up to 23) occurred following RH fluctuations of 5 to 15%. Watering resulted in an immediate increase (≤25%) followed by a rapid decrease in RH (≤32%) beginning 1 to 2 h later. In GH 2 and GH 11, 89 and 48%, respectively, of the CREs occurred within 3 h following greenhouse watering. When greenhouse temperatures exceeded 25°C for 21 days in May (GH 2) and 19 days in March (GH 11), atmospheric conidial concentrations were reduced 80 and 75% from the previous months, respectively.
Maize necrotic streak virus, a New Maize Virus with Similarity to Species of the Family Tombusviridae
Authors: Louie Raymond , Redinbaugh M. G. , Gordon D. T. , Abt J. J. , Anderson R. J.
Published: May 2007

A new virus was isolated from maize (Zea mays L.) leaves showing mild mosaic symptoms and coinfected with Maize dwarf mosaic virus. The virus was readily transmitted by vascular puncture inoculation (VPI) but not leaf-rub inoculation. Virus symptoms on susceptible maize included pale green, yellow, or cream-colored spots and streaks measuring 1 to 2 mm on emerging leaves 5 to 7 days post-VPI. As leaves developed, the spots and streaks became spindle-shaped, then coalesced into long, chlorotic bands. These bands became translucent and necrotic around the edges. There was a distinctive chlorosis on the stalks that became necrotic. Based on these distinctive symptoms, the new virus was named Maize necrotic streak virus (MNeSV). The virus was not transmitted by Aphis maidis-radicus, Myzus persicae, Macrosiphum euphorbiae, Rhopalosiphum padi, Dalbulus maidis, Graminella nigrifrons, Perigrinus maidis, or Diabrotica virgifera virgifera under persistent or nonpersistent conditions. Both susceptible and resistant maize genotypes were identified following VPI with MNeSV. The isolated virus had isometric (32 nm) virions and a single 29.5-kDa coat protein. MNeSV was serologically distinct from morphologically similar maize viruses. The 4.3-kb single-stranded RNA genome had 25 to 53% sequence identity with species in the family Tombusviridae.
First Report of Oidium sp. Powdery Mildew and Tomato spotted wilt virus on Melampodium divaricatum
Authors: Holcomb G. E. , Valverde R. A.
Published: May 2007

Melampodium divaricatum (Rich. ex Pers.) DC. (=M. paludosum H.B.K.), a member of the family Asteraceae and native to South America, is a recent introduction for use as a summer bedding ornamental. In September 1999, melampodium plants in multiple Baton Rouge landscapes were observed with signs of powdery mildew and symptoms of a virus-like disease. Powdery mildew spread throughout one of the plantings by late November and infected flowers and leaves. An Oidium species sporulated on both leaf surfaces but was more common on the adaxial surface. Ellipsoid conidia were produced in chains, lacked fibrosin bodies, and averaged 31 × 19 µm. No sexual stage was observed. Eight of 63 plants (cv. Derby) in one of the plantings showed virus disease symptoms that included severe leaf mosaic, leaf malformation, and stunting. Leaves from infected plants were used to sap inoculate seedling plants of melampodium and Nicotiana benthamiana. Melampodium seedlings developed typical mosaic symptoms after 48 to 56 days. N. benthamiana developed severe chlorosis and mosaic, then wilted and died after 14 days. Noninoculated plants of both species remained healthy. The virus in both plant species was identified as Tomato spotted wilt virus (TSWV) by enzyme-linked immunosorbent assay (ELISA) (Agdia, Elkhart, IN). ELISA tests for presence of Impatiens necrotic spot virus were negative. This is the first report of powdery mildew and TSWV on M. divaricatum.
A Severe Outbreak of Fire Blight in Woody Ornamental Rosaceae Plants in North Florida and South Georgia
Authors: Momol M. T. , Momol E. A. , Dankers W.
Published: May 2007

Woody ornamentals including ‘Bradford’ and ‘Aristocrat’ pears (Pyrus calleryana), Indian hawthorn (Rhaphiolepis sp.), and cotoneaster (Cotoneaster spp.) developed blossom and shoot blight symptoms suggestive of fire blight caused by Erwinia amylovora. Disease was observed in several counties in north Florida and south Georgia and samples were sent to Florida Extension Plant Diagnostic Clinic-Quincy (FEPDC-Q). The incidences in individual ‘Bradford’ pear were as high as 30 to 40 strikes per tree. This level of severe E. amylovora infections on ‘Bradford’ pear has not been seen in Florida for the last 10 years based on FEPDC-Q data. Symptomatic plants first appeared in the landscape and nurseries around the first week of April 2000 in the following counties: Bay, Holmes, Washington, Gadsden, Leon, Jefferson (north Florida), and Decatur (south Georgia). Severely infected ‘Bradford’ pear trees were also observed in Georgia cities of Cairo, Thomasville, Moultrie, and Tifton. The presence of E. amylovora in samples was verified by pEA29-polymerase chain reaction (PCR) (2,4), fatty acid methyl ester analysis (MIDI, Newark, DE), and colony type on semi-selective modified Miller-Schroth (MMS) medium (3). Of the 16 samples tested by PCR, E. amylovora was present in all. Actively growing shoots of Cotoneaster salicifolius (a susceptible host) were inoculated with a bacterium isolated from ‘Bradford’ pears that was identified as E. amylovora by PCR. Dark brown necrotic tissues with typical fire blight appearance developed within 10 days. E. amylovora was reisolated on MMS medium from inoculated shoot tissues of C. salicifolius and confirmed by PCR. The presence of E. amylovora from ornamental pears, Indian hawthorn, and cotoneasters was previously reported in Florida (1). Cool spring temperatures in the Florida panhandle and several rain events during the bloom period may have stimulated the severe outbreak of fire blight. This severe outbreak highlights the importance of using a forecasting model such as Maryblyt 4.3 to predict unexpected infection periods so that preventive control measures can be taken.

References: (1) S. A. Alfieri, Jr. et al. Florida Department of Agriculture and Consumer Services, Bulletin No. 14, 1994. (2) S. Bereswill et al. Appl. Environ. Microbiol. 58:3522, 1992. (3) W. Brulez and W. Zeller. Acta Hortic. 117:37, 1981. (4) M. T. Momol et al. Plant Dis. 82:646, 1998.
Cyclanthera pedata var. edulis: New Host of Papaya ringspot virus-type W in Brazil
Authors: Rezende J. A. M.
Published: May 2007

Stuffing cucumber (Cyclanthera pedata var. edulis Schrad.) is native to the Americas, where it often occurs as an escape. The species is monoecious, with small flowers and large and deeply palmately lobed leaves. Fruits are puffy, partially hollow, and measure 5 × 15 cm long. The plant has soft spines, a tapered neck, and black seeds. The species has long been cultivated in Asia, where fruits are eaten raw as a substitute for cucumber or cooked (1). One plant showing intense mosaic, without leaf malformation, was found near a squash crop (Cucurbita moschata) in Anhembi County, State of São Paulo. Electron microscopic examination of a negatively stained sap preparation from leaves of this plant showed that it contained numerous flexuous rod-shaped particles, approximately 700 × 760 nm long, similar to those of potyviruses. Extracts from symptomatic leaves were rub-inoculated to zucchini squash (Cucurbita pepo), Carica papaya, Chenopodium amaranticolor, C. quinoa, Gomphrena globosa, and Phaseolus vulgaris cv. Black Turtle 2. Only zucchini squash was infected and developed severe mosaic with intense leaf malformation. Extracts from field infected stuffing cucumber and experimentally inoculated zucchini squash were tested by plate-trapped antigen enzyme linked immunosorbent assay (PTA-ELISA) with antisera against the following potyviruses: Papaya ringspot virus-type W (PRSV-W), Zucchini yellow mosaic virus (ZYMV), and Watermelon mosaic virus-2 (WMV-2). Samples were also tested with antisera against a tospovirus (Zucchini lethal chlorosis virus) and a cucumovirus (Cucumber mosaic virus). Both samples were positive in PTA-ELISA only with PRSV-W antiserum. This is the first report of C. pedata var. edulis as a natural host for PRSV-W in Brazil.

References: (1) R. W. Robinson and D. S. Decker-Walters. 1997. Cucurbits. CAB International, UK.
Cucurbit yellow stunting disorder virus (Genus Crinivirus) Associated with the Yellowing Disease of Cucurbit Crops in Portugal
Authors: Louro D. , Vicente M. , Vaira A. M. , Accotto G. P. , Nolasco G.
Published: May 2007

During autumn 1998, chlorotic mottling, yellowing, and stunting symptoms were observed on cucumber (Cucumis sativus L.) plants in an experimental plot, in Algarve, southern Portugal. The first symptoms appeared 3 weeks after planting, associated with a heavy infestation of Bemisia tabaci (Gennadius). Plants affected early produced few and small fruits. Analysis of double-stranded RNA (dsRNA) extracted from symptomatic cucumber leaves revealed the presence of two dsRNAs of about 8 and 9 kbp, not present in healthy cucumber plants. Reverse-transcription polymerase chain reaction (RT-PCR) using dsRNA or total RNA extracts as template and the oligonucleotide primers 410L and 410U (1), specifically amplified a fragment of expected size of the HSP70-homolog gene of Cucurbit yellow stunting disorder virus (CYSDV). The RT-PCR-amplified fragment was sequenced (Acc. No. AF287474) and showed 99% sequence identities with the corresponding sequences (GenBank accessions AJ223619 and U67170) from two CYSDV isolates belonging to group I (2), confirming CYSDV detection. CYSDV was also detected in samples of cucumber, melon (Cucumis melo L.) and watermelon (Citrullus lanatus [Thunb.] Matsun.) collected during the summer of 1999 in commercial greenhouses. CYSDV is an emerging and important virus of cucurbits in the Middle East and Mediterranean Europe (2). This is the first report of CYSDV infecting cucurbit crops in Portugal.

References: (1) A. Célix et al. Phytopathology 86:1370, 1996. (2) L. Rubio et al. Phytopathology 89:707, 1999.
Cuticular Fractures Promote Postharvest Fruit Rot in Sweet Cherries
Authors: Børve Jorunn , Sekse Lars , Stensvand Arne
Published: May 2007

Preharvest cuticular fractures in sweet cherry fruit have been suggested to facilitate pathogen invasion, and a method to classify the mount of cuticular fracturing into five categories (from 1 = no visible fractures to 5 = severe fracturing) has previously been proposed. Sweet cherry fruit of the four cultivars Early Burlat, Lapins, Van, and Vista were sorted into these five categories of cuticular fracturing and inoculated with conidial suspensions of either Botrytis cinerea or Monilinia laxa. After incubating the fruit at 20°C and 100% relative humidity for 4 to 7 days, they were assessed for visible fungal growth. Due to quiescent infections of M. laxa, fruit treated with B. cinerea developed more brown rot than gray mold. However, a significant linear relation (P < 0.05) between the amount of cuticular fracturing and fungal infections was obtained in five of seven trials with B. cinerea and in two of four trials with M. laxa, indicating that fungal infections in sweet cherry fruit may be facilitated by cuticular fractures. Independent of cultivar and year, a significant linear relation was found between the category of cuticular fracturing and percentage of infected fruit after inoculation with both B. cinerea and M. laxa, and in control fruit (P = 0.0001, 0.0183, and 0.0182, respectively). This is the first report quantifying an increase in fungal infection with increasing amount of cuticular fracturing. The mean difference in fruit rot (%) ± standard deviation among fruit in fracturing categories 1 and 5, expressed as the linear contrast of amount of fruit rot in category 5 minus amount of fruit rot in category 1, was 37.2 ± 7.4 (P = 0.0001), 35.4 ± 11.0 (P = 0.0022), 17.0 ± 6.7 (P = 0.0135), and 29.8 ± 4.7 (P = 0.0001), after treatments with B. cinerea, M. laxa, water control, and for all data pooled, respectively.
Rational Use of Fungicide Applications to Maximize Peanut Yield Under Foliar Disease Pressure in West Africa
Authors: Waliyar F. , Adamou Moustapha , Traoré Aoua
Published: May 2007

Foliar diseases caused by Cercospora arachidicola, Cercosporium personatum, and Puccinia arachidis are major constraints to peanut production in the world. Fungicides are among the most efficient available control methods. Field trials were conducted in 1991 and 1992 in Benin and Niger, West Africa, to evaluate the cost effectiveness of fungicide application timings and frequencies on four peanut cultivars. A combination of four timings (40, 55, 70, and 85 days after sowing) was scheduled. Early (causal organism, C. arachidicola) and late (caused by C. personatum) leaf spot were prevalent in both years, but late leaf spot was the more economically important disease as shown by high values of area under the disease progress curve. Application of fungicide reduced late leaf spot incidence and increased pod yield. Pod yield responded to an interaction of number and timing of fungicide applications. With appropriate timing two or three fungicide applications were enough to significantly increase pod yield. Properly timed fungicide sprays can result in substantial monetary gains for peanut farmers in West Africa.
Comparison of Plastic Mulch and Nitrogen Form on the Incidence of Verticillium Wilt of Eggplant
Authors: Elmer Wade H.
Published: May 2007

Eggplants (cv. Midnite) were grown during 1996 to 1998 in soils naturally infested with Verti-cillium dahliae. Experimental plots were either mulched with black plastic or grown on bare ground and fertilized with either (NH4)2SO4or Ca(NO3)2at 224 kg of N per hectare each season. Compared to bare ground, mulch resulted in a 42 and 68% increase in 1996 and 1997, respectively. Compared to Ca(NO3)2, (NH4)2SO4fertilization increased yield by 22 and 18% in 1996 and 1997, respectively. In both years, there were no significant interactions between the mulch and fertilizer treatments on yield or on integrated estimates of the plant canopy growth curve or disease severity. However, the treatment effects were additive. When compared to bare ground, mulching increased the plant canopy 3 weeks after planting and reduced the percentage of symptomatic foliage 8 weeks after planting. Compared to Ca(NO3)2, fertilization with (NH4)2SO4increased the plant canopy after 6 weeks, but did not affect the percentage of symptomatic foliage. Mulching or (NH4)2SO4fertilization increased the number of flowers compared to no mulching or Ca(NO3)2fertilization, respectively. The rate of nitrogen fertilizer at planting or as a side-dress application did not affect growth or disease, but plants treated with (NH4)2SO4were larger and had less symptoms than Ca(NO3)2-treated plants. The use of black plastic mulch with (NH4)2SO4fertilization complements one another and may reduce damage from Verticillium wilt on eggplant.
Postharvest Decay Risk Associated with Hydrocooling Tomatoes
Authors: Vigneault Clément , Bartz Jerry A. , Sargent Steven A.
Published: May 2007

Tomatoes (breaker stage) hydrocooled with a cell suspension of Erwinia carotovora subsp. carotovora containing 50 to 200 mg of free chlorine per liter (ppm) (10°C, pH 7) remained decay free during a 10-day storage at 20°C. Sporadic disease appeared during storage of tomatoes similarly cooled with chlorinated water containing spores of Rhizopus stolonifer. In contrast, when chlorine was omitted from the pathogen suspensions, 50 to 100% of the fruit became diseased. A laboratory-scale shower hydrocooler reduced fruit temperatures from 35 to 15°C within 13.3 min, whereas a flume cooler produced the same temperature reduction in 10.5 min. In both systems, tomatoes increased in weight during cooling, evidence for water uptake. Larger weight increases occurred among tomatoes cooled in the shower than in the flume. An upward instead of downward orientation of stem scars under the shower streams led to significantly larger weight increases, presumably because pores in the stem scar were continuously flooded with water. Tomatoes intermittently submerged in cold water (10 2-min immersions followed by 30-s pauses) absorbed significantly less water than those continuously submerged for 20 min. Hydrocooling appears to be a viable method for rapid cooling of tomatoes. Technical refinements in the hydrocooling process that prevent continuous coverage of fruit surfaces by water should reduce water uptake and the associated risk of pathogen internalization. Maintenance of free chlorine at up to 200 ppm in the cooling water and prevention of direct water pressure on fruit should minimize decay risks. No evidence of phytotoxicity was observed among fruit infiltrated with 200 ppm of chlorine. These tomatoes ripened similarly to those that were not cooled or were cooled in tap water.
Occurrence of Stem Rot of Basil, Caused by Sclerotinia sclerotiorum, in Coastal California
Authors: Koike S. T.
Published: May 2007

In January and February 1999, extensive dieback was observed on commercial basil (Ocimum basilicum) being grown in shadecloth greenhouses in coastal California's Salinas Valley. Symptoms were associated with stems that were high in the plant canopy and had cut ends resulting from multiple harvests of the foliage. Stems had brown discoloration extending from the cut ends toward the crown of the plant. Attached petioles and leaves turned brown and wilted. Profuse white mycelia were generally present externally on symptomatic stems, and occasionally large (>5 mm long) black sclerotia were found inside affected stems. In some shade houses approximately 20 to 25% of the plants were diseased. Isolations from mycelia, sclerotia, and symptomatic stems produced colonies of Sclerotinia sclerotiorum. Inocula for pathogenicity tests were produced by growing isolates on potato-dextrose agar, removing the resulting sclerotia, air drying them for 12 h, and placing them onto sterilized sand saturated with sterile distilled water. Sand cultures were incubated at 24 to 26°C in the light. After 4 to 6 weeks, apothecia containing asci with eight uniform ascospores developed from the sclerotia. Apothecial cultures were placed at the base of potted basil plants that had been trimmed to simulate harvest and placed in a humidity chamber. After 4 weeks, stem dieback was observed on test plants and S. sclerotiorum was recovered from symptomatic tissue. This pathogenicity test was repeated and the results were similar. Though this disease has occurred in the state prior to 1999, this is the first report of S. sclerotiorum on basil in California. This disease has been reported in North America from Canada and Louisiana (2,3). In contrast with reports from Europe (1), basal infections were not observed in the California greenhouses.

References: (1) A. Garibaldi et al. Plant Dis. 81:124, 1997. (2) G. E. Holcomb and M. J. Reed. Plant Dis. 78:924, 1994. (3) T. C. Paulitz. Plant Dis. 81:229, 1997.
Natural and Augmented Spread of Rose Rosette Disease of Multiflora Rose in Maryland
Authors: Tipping P. W. , Sindermann A. B.
Published: May 2007

Rose rosette disease (RRD), a mite-vectored agent of unknown etiology, was first recorded on multiflora rose, Rosa multiflora Thunb. in central Maryland in 1996. This uncharacterized agent is transmitted to some members of rose family by the eriophyid mite Phyllocoptes fructiphilus Keifer, which is common on multiflora rose in Maryland (1). It is also graft-transmissible (2). In 1996, a farmer near Middletown in Frederick County observed one plant with witches'-broom and reddened shoots along a fence row and sent a sample to J. W. Amrine, Jr. at West Virginia University, for confirmation of the disease (J. W. Amrine, personal communication). During 1997, delimiting surveys around this farm failed to detect any other plant with noticeable symptoms in an area heavily infested with multiflora rose. In an attempt to augment the disease, we grafted shield buds from this plant into 10 nearby apparently helathy plants in May and again in June 1997. None of these grafts were successful. More diseased buds were removed from the original infected plant during May 1998 and grafted into another 12 plants. By June of 1999, only the graft-inoculated plants from 1998 had symptomatic shoots arising from the graft sites. During this interval, RRD was observed in sites in western Maryland near Cumberland in Allegany County (May 1997) and Hagerstown in Washington County (May 1998). Initially, the percentage of symptomatic plants at these sites was less than 10%. Surveys 12 months later indicated that approximately 50% of the plants showed symptoms of RRD. At one site, the majority of the larger multiflora rose plants had at least one dead cane and a few were completely dead. Further augmentation of RRD by grafting was conducted in May 1998 at the University of Maryland Research and Education Center in Keedysville in southern Washington County, and by June 1999 only treated plants were symptomatic. In August 1998, one multiflora rose and one ornamental rose, Rosa hybrida ‘Scarlet Meidiland’ Meikrotal, exhibited RRD symptoms on a farm in northern Washington County near the Pennsylvania border. We found numerous symptomatic multiflora roses in May 1999, at a farm in northern Frederick County, also near the Pennsylvania border. Symptomatic plants have been observed during 2000 in Montgomery, Carroll, and Baltimore Counties as RRD continues to spread rapidly east and north through the state. This is the first documentation of the occurrence and rate of spread of RRD in Maryland.

References: (1) W. B. Allington et al. J. Econ. Entomol. 61:1137, 1968. (2) E. A. Thomas and C. E. Scott. Phytopathology 43:218, 1953.
Elaboration of an Early Quantification Method of Quiescent Infections ofColletotrichum musaeon Bananas
Authors: de Bellaire L. de Lapeyre , Chillet M. , Mourichon X.
Published: May 2007

Colletotrichum musae, the causal agent of banana anthracnose, forms quiescent infections on the surface of the fruit that lead to necrosis at maturity. This work was conducted to determine a practical way to quantify the inoculum level that is economically practicable for routine use and applicable to immature fruit, so that it can be used as a method of early prediction and subsequent decision support. The method that has been developed is based on treating the fruit with 1,200 μl of ethylene per liter for 24 h at 25°C. The fruit are then kept at 32°C for 5 days, maintaining the ethylene concentration, so that conditions are optimal for revealing the disease. The technique can be used on fruit whose age is 5 to 6 weeks after inflorescence emergence. A high CO2concentration has an inhibitory effect on the development of lesions. The importance of the ethylene treatment on fruit maturation and breaking of appressorium dormancy is discussed, together with potential applications.
Characterization of Sphaeropsis sapinea Isolates from South Africa, Mexico, and Indonesia
Authors: de Wet Juanita , Wingfield Michael J. , Coutinho Teresa A. , Wingfield Brenda D.
Published: May 2007

Post-hail-associated dieback of Pinus patula and P. radiata trees, induced by Sphaeropsis sapinea (=Diplodia pinea), is a common and important disease in commercial pine plantations. Two morphotypes, A and B, have been described for this fungus based on differences in cultural characteristics, conidial morphology, and virulence among isolates from the north central United States. The existence of the two described morphotypes was later verified through the use of random amplified polymorphic DNA (RAPD) analyses, and the morphotypes were designated as the A and B RAPD marker groups. The objective of this study was to characterize a set of S. sapinea isolates from South Africa, Indonesia, and Mexico using RAPD analysis and DNA sequencing of the internal transcribed spacer (ITS) region of the ribosomal DNA operon. Sizes of conidia and culture morphology were, furthermore, used to compare the three groups of S. sapinea isolates that emerged from the RAPD analysis. Two of the RAPD groups included isolates from the United States, representing the A and B morphotypes, while the third RAPD group accommodated Indonesian and one Mexican isolate. ITS sequences of all the S. sapinea isolates were highly homologous and resolved only the A and B RAPD groups. The ITS sequences of the isolates in the third RAPD group were the same as those of the A RAPD group. Conidia of isolates representing the A and B morphotypes were approximately the same size, but those of the third RAPD group were significantly longer. RAPD analysis enabled us to identify a third group of S. sapinea that is different from the well-recognized A and B groups. Isolates in this third RAPD group also have a distinct morphological characteristic and thus represent a third discrete morphological group, which we refer to as the C morphotype of S. sapinea.
First Report of Fusarium Wilt of Babaco (Carica × heilbornii var. pentagona) in Ecuador
Authors: Ochoa J. , Fonseca G. , Ellis M. A.
Published: May 2007

Babaco, Carica × heilbornii V.M. Badillo var. pentagona (Heilborn) V.M. Badillo, is a fruit native to Ecuador that has great potential as a cultivated crop. Local market demand and strong potential as an export crop have greatly increased interest in babaco production in Ecuador. Although the crop can be produced in open fields, the majority of crop production is in plastic greenhouses. In 1996, a serious wilt disease developed on babaco in several greenhouses, resulting in up to 100% loss of plants. Symptoms first appeared as chlorosis of the lower leaves, followed by defoliation progressing up the stem until the entire plant was defoliated. When cut in cross section, vascular discoloration was observed in the stem. Eventually necrosis and soft rot of the stem occurred and entire plants collapsed. Fungal isolations were conducted from fine feeder roots of diseased plants by soaking root pieces (2 cm long) in a 0.5% solution of sodium hypochlorite for 3 min. Root pieces were cut into smaller sections and placed on potato dextrose (PDA) or corn meal (CMA) agar in petri dishes. Isolations from larger roots, crowns, stems and fruits were made by soaking tissue sections of each plant part in a 2.87% solution of sodium hypochlorite for 3 min. Tissue sections were rinsed three times in sterile distilled water. Smaller tissue sections (≈0.125 cm3) were cut from surface-disinfested pieces and placed on PDA and CMA in petri dishes. Cultures were incubated at 20°C. A fungus resembling Fusarium sp. was isolated consistently from infected tissues from all infected plant parts. Based on the morphology of the fungal colony and conidia from monosporic isolations, the fungus was identified as Fusarium oxysporum Schlechtend:Fr. (1). Pathogenicity tests were conducted by growing babaco plants in pots containing an equal mixture of sterilized soil, compost, and sand in the greenhouse. Eight 7-month-old plants were inoculated by placing 40 ml of a suspension (106 conidia per ml) of F. oxysporum in four plastic straws placed in the soil (5 cm depth) at equal distances (5 cm) from the base of each plant. Straws around noninoculated control plants received sterile water. Plants were watered with 400 ml of sterile water daily. Pathogenicity tests were repeated once as described. All inoculated plants developed typical wilt symptoms within 45 days after inoculation. No symptoms developed on uninoculated control plants. F. oxysporum was successfully reisolated from infected stem tissues of inoculated plants. Incidence of Fusarium vascular wilt of babaco has continued to increase since 1996 and is currently the major constraint to production.

References: (1) P. E. Nelson et al. 1981. Fusarium: Diseases, Biology, and Taxonomy. The Pennsylvania State University Press, University Park.
First Report and Molecular Characterization of Yam mild mosaic virus in Dioscorea alata on the Island of Martinique
Authors: Bousalem M. , Dallot S.
Published: May 2007

Naturally infected Dioscorea alata plants showing mild mosaic were collected in 1998 on the island of Martinique in the Caribbean. Isolates were first screened by double-antibody sandwich enzyme-linked immunosorbent assay (ELISA) with monoclonal antibodies raised against Yam mosaic virus (YMV) and antigen-coated plate ELISA with universal potyvirus monoclonal antibodies (Agdia, Elkhart, IN). A positive reaction was obtained only with the universal potyvirus antiserum. Immunocapture reverse-transcriptase polymerase chain reaction was performed for specific detection of Yam mild mosaic virus (YMMV [3]) and YMV. A product with the predicted size of 249 bp was obtained with YMMV primers. YMMV is a recently recognized distinct potyvirus infecting D. alata in West Africa and the South Pacific (2–4). It was originally described as Yam virus I and is synonymous with Dioscorea alata virus (4). To characterize the YMMV Martinique isolate, total RNA was extracted, and universal potyvirus degenerate primers (1) were used to amplify a 700-bp fragment that included the core and C-terminal region of the coat protein (CP) and 3′ untranslated region (3′UTR). Sequence information generated (EMBL AJ250336) from the cloned fragment was compared with sequences of other yam potyviruses. Sequence comparisons of the partial CP (453 nt) showed a similarity of 94.6% (amino acids [aa]) with the YMMV isolate from Papua New Guinea (EMBL AB022424 [2]); 72.2% (aa) with the Japanese yam mosaic virus (JYMV) isolate (EMBL AB016500); and 67 to 73% (aa) with 27 YMV isolates. These sequences are most diverse in the 3′UTR, which showed a similarity of 72.8% with the YMMV Papua New Guinea isolate, 30% with the JYMV isolate, and 26% with the YMV isolates. These results confirm, as previously shown by S. Fuji et al. (2), that YMMV should be classified as a new potyvirus of yam. This is the first report of the natural occurrence of YMMV in the Caribbean.

References: (1) Colinet et al. Phytopathology 84:65, 1994. (2) S. Fuji et al. Arch Virol. 144:1415, 1999. (3) R. A. Munford and S. E. Seal. J. Virol. Methods 69:73, 1997. (4) B. O. Odu et al. Ann. Appl. Biol. 134:65, 1999.
Yellow Leaf Disease of Cantaloupe and Wax Gourd from Thailand Caused by Tomato leaf curl virus
Authors: Samretwanich K. , Chiemsombat P. , Kittipakorn K. , Ikegami M.
Published: May 2007

Cantaloupe (Cucumis melo var. reliculatus) and wax gourd (Benincasa hispida Cogn.) plants showing a yellow leaf disease have been observed in central Thailand since 1993. The disease has been transmitted to cantaloupe and wax gourd plants by grafting and whiteflies (Bemisia tabaci Genn.) (K. Kittipakorn, unpublished data). Because of the leaf yellowing symptoms and transmission by whiteflies, a geminivirus was suspected. Three naturally infected cantaloupe and four naturally infected wax gourd plants showing leaf yellowing were collected from fields at Kamphaengsaen, Nakorn Pathom, Thailand. Virus cultures were maintained in cantaloupe and wax gourd plants. Inoculations were done with a whitefly vector. Symptoms in cantaloupe and wax gourd plants were the same as those observed in the field. Virus DNA associated with yellow leaf disease of cantaloupe and wax gourd plants was amplified by polymerase chain reaction with geminivirus-specific degenerate primers, described by Rojas et al. (2), that anneal within the AC1 open reading frame (ORF; replication associated protein gene) and the AV1 ORF (coat protein gene) of bipartite geminiviruses and the C1 and V2 ORFs of monopartite geminiviruses (2). Fragments (1.2 kbp) were amplified and cloned from affected cantaloupe and wax gourd plants. Three independent clones were sequenced and analyzed, and identical 32-base stem loop regions were found in the amplified fragments from both isolates, including the conserved nonanucleotide sequence TAATATTAC, which is present in all geminiviruses. The iterative sequence GGCGTC also was found in the intergenic region (IR) (434 bp) of the amplified fragments from both isolates. The B component could not be detected. The nucleotide sequences of the IR and V1 were compared with 28 well-studied whitefly-transmitted geminiviruses and revealed ≈96% sequence identity with DNA A of Tomato leaf curl virus of the genus Geminivirus from India (ToLCV-In 2) (1) for both isolates. The iterative sequence GGCGTC in the IR also was identical to the sequence in ToLCV-In 2. These results establish the provisional identity of the pathogen causing yellow leaf disease on cantaloupe and wax gourds in Thailand as ToLCV or closely related strains.

References: (1) M. Padidam et al. J. Gen. Virol. 76:249, 1995. (2) M. R. Rojas et al. Plant Dis. 77:340, 1993.
Outbreak of Potato Y potyvirus and Tobacco mosaic tobamovirus in Georgia's Flue-Cured Tobacco
Authors: Pappu H. R. , Bertrand P. F.
Published: May 2007

Flue-cured tobacco is an economically important crop in Georgia. During the 1999 growing season, tobacco plants showing various degrees of mottling (mild to severe), mosaic, and vein clearing were observed in most counties in Georgia. In most cases, symptoms were not clearly those associated with Potato Y potyvirus (PVY) or Tobacco mosaic tobamovirus (TMV). The incidence of symptomatic plants in individual fields ranged from 0 to 90%. A survey was conducted in several tobacco-growing counties to ascertain the causal agent(s) of the disease. Symptomatic plants were collected from 11 counties: Appling, Atkinson, Bacon, Berrien, Coffee, Colquitt, Echols, Grady, Lowndes, Tattnall, and Ware. Leaf samples were tested by enzyme-linked immunosorbent assay (ELISA) for Cucumber mosaic cucumovirus (CMV), PVY, TMV, Tobacco etch potyvirus (TEV) and Tobacco vein mottling potyvirus. On the basis of ELISA, TMV and PVY were the most prevalent viruses, followed by CMV. From a total of 50 samples tested, 28 were doubly infected with TMV and PVY, 3 were positive for only TMV, and 5 were positive for only PVY. Eight samples were infected only with CMV, and one sample was doubly infected with PVY and TEV. The causal agent(s) in the remaining five samples could not be determined. Although PVY, TMV, TEV, and CMV occur to some degree every year, they have not been economically important in the past few years. It is interesting that the recent epidemic on tobacco and pepper in northern Florida was associated with CMV (1). Considering the predominance of double infections observed, diagnosis of virus-like symptoms in tobacco may require use of ELISA or other specific detection methods.

Reference: (1) T. A. Kucharek et al. Plant Dis. 82:1172, 1998.
Distribution of Baseline Sensitivities to Azoxystrobin Among Isolates of Plasmopara viticola
Authors: Wong Francis P. , Wilcox Wayne F.
Published: May 2007

An excised leaf disc assay was developed for determining the sensitivity of isolates of Plasmopara viticola (causal agent of grapevine downy mildew) to the strobilurin fungicide azoxystrobin. Five repeated assays with the same five single-sporangiophore isolates showed that the technique yielded reproducible results; that is, coefficients of variation ranged from 4.0 to 20% (mean 12%) for effective doses for 50% control (ED50 values) based on disease incidence and from 4.4 to 14% (mean 8.1%) for ED50 values based on disease severity. Then, the assay was applied to 81 single-sporangiophore isolates of P. viticola collected from 10 geographically distinct vineyards in western New York, providing a baseline distribution of sensitivities within this population. For disease incidence, individual ED50 values ranged from 0.05 to 0.94 μg/ml (mean 0.40 μg/ml), whereas for disease severity they ranged from 0.04 to 0.78 μg/ml (mean 0.24 μg/ml). When 61 of these isolates were similarly tested at a single discriminatory dose of 0.50 μg/ml, azoxystrobin provided 61% control of disease incidence versus 41 and 1.1% control for trifloxystrobin and kresoximmethyl, respectively; for disease severity (colony diameter), azoxystrobin provided 80% control versus 57 and 1.1% control for trifloxystrobin and kresoximmethyl, respectively. These results provide information that can be utilized in future monitoring of P. viticola resistance to azoxystrobin and indicate differences in the intrinsic activities of the three strobilurin fungicides against this pathogen.
Nutrient Solution Temperature Affects Pythium Root Rot of Tobacco in Greenhouse Float Systems
Authors: Fortnum B. A. , Rideout J. , Martin S. B. , Gooden D.
Published: May 2007

Float nutrient solution, soilless media, and ambient temperatures were monitored in two tobacco greenhouses with different heating regimes. Water temperatures at seeding were 11°C in an unheated greenhouse and 17°C in a heated greenhouse. Water temperature differences between greenhouses continued over the duration of seedling production. Media and air temperatures varied diurnally, but not float solution. In a greenhouse float system where water temperatures were constant at 15, 20, 25, or 30°C, seedling disease caused by Pythium myriotylum was correlated with float-water temperature and could be described by quadratic equations (R2 = 0.99) with the lowest level of root necrosis at 15°C. Pythium spp.-infected and noninfected seedlings grown in controlled-temperature water baths were transplanted to the field and evaluated for disease development. Previous infection with P. myriotylum, regardless of float-temperature regime, failed to alter yield, leaf quality, or root necrosis (P = 0.05) in field-grown tobacco.