bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Concentration of Soda Ash, Temperature, and Immersion Period on the Control of Postharvest Green Mold of Oranges
Authors: Smilanick J. L. , Mackey B. E. , Reese R. , Usall J. , Margosan D. A.
Published: May 2007

Oranges were inoculated with spores of Penicillium digitatum, the citrus green mold pathogen, and immersed 24 h later in heated soda ash (Na2CO3, sodium carbonate) solutions to control postharvest citrus green mold. Oranges were immersed for 1 or 2 min in solutions containing 0, 2, 4, or 6% (wt/vol) soda ash heated to 35.0, 40.6, 43.3, or 46.1°C. After 3 weeks of storage at 10°C, the number of decayed oranges was determined. Soda ash significantly controlled green mold in every test. The most effective control of green mold was obtained at 40.6 or 43.3°C with 4 or 6% soda ash. The concentration of soda ash greatly influenced efficacy, whereas the influences of temperature or immersion period on soda ash efficacy were small. Solutions of 4 and 6% soda ash were similar in efficacy and provided superior control of green mold compared with 2% soda ash. The control of green mold by soda ash solutions heated to 40.6 or 43.3°C was slightly superior to control by solutions heated to 35.0 or 46.1°C. The control of green mold by 1-min immersion of inoculated oranges in heated soda ash solutions was inferior to immersion for 2 min, but the magnitude of the difference, particularly with 6% soda ash, was small. A second-order response surface model without interactions was developed that closely described the influence of soda ash concentration, temperature, and immersion period on efficacy. The efficacy of soda ash under commercial conditions was better than that predicted by the model, probably because under commercial conditions the fruit were rinsed less thoroughly with water after treatment than in laboratory tests. The primary finding of this work was that soda ash controlled 24-h-old green mold infections at commercially useful levels using shorter immersion periods and lower temperatures than those recommended by other workers for the use of soda ash on lemons. The oranges were not visibly injured in any test.
Detection of Virulence to Lr41 in a South African Pathotype of Puccinia recondita f. sp. tritici
Authors: Pretorius Z. A.
Published: May 2007

The Lr41 gene for resistance to leaf rust, caused by Puccinia recondita f. sp. tritici, was transferred from Triticum tauschii accession TA2460 to bread wheat (T. aestivum) at the Wheat Genetics Resource Center, Kansas State University (1). Due to the high degree of resistance (primary leaf infection types [ITs] 0; to ;1= [0 to 4 scale]) conferred to South African pathotypes of leaf rust, the gene was considered potentially valuable in local programs directed at wheat germ plasm improvement. During routine glasshouse tests for seedling resistance to the South African leaf rust pathotype UVPrt16, several sporulating pustules (IT 4) were observed among flecks on wheat line KS90WGRC10 (TAM107*3/TA2460). Rust cultures multiplied from these pustules were tested on seedlings of 31 wheat lines with different Lr genes in a growth cabinet at 20°C. Their avirulence/virulence characteristics suggested a single-step mutation for virulence to Lr41. According to North American nomenclature (2), the Lr41-virulent isolate is classified as race FDC-14b,20,23,25,33,41. Low ITs were recorded on additional testers with Lr3bg, 14a, 15, 18, 19, 27+31, 28, and 29, and intermediate ITs on lines with Lr2b, 10, 21, 32, and 36. Infection studies on adult plants showed that KS90WGRC10 and its recurrent parent TAM107 produced similar susceptible reactions (Its 3++C) to the mutant. T. tauschii accession TA2460, however, was moderately susceptible (IT 2+) to this culture. Virulence to Lr41 has not been recorded in field populations of the pathogen in South Africa. The occurrence of virulence to Lr41 emphasized the nondurability of monogenic resistance and thus the importance of conserving genetic diversity for leaf rust resistance. To protect Lr41 from becoming obsolete, it should be used only in combination with other effective resistance gene(s).

References: (1) T. S. Cox et al. Crop Sci. 32:506, 1992. (2) D. L. Long and J. A. Kol-mer. Phytopathology 79:525, 1989.
Purple Coneflower Is a Host of the Aster Yellows Phytoplasma
Authors: Stanosz G. R. , Heimann M. F. , Lee I.-M.
Published: May 2007

The perennial plant purple coneflower (Echinacea purpurea (L.) Moench, Asteraceae) is native to open woods and prairies of the eastern U.S. and is gaining popularity as a garden and roadside ornamental. It is propagated both by seed and by division of established plant crowns. During late summer 1996, three of seven purple coneflower plants located in a residential garden in Dane County, WI, exhibited symptoms associated with diseases caused by phytoplasmas. These plants had been established from seed in spring 1995. Stems were thickened and brittle. Leaves were slightly twisted and drooped, and flower parts lacked normal pigmentation. Petals of ligulate flowers were narrow. Clusters of short, thin stems bearing sterile, dwarfed, distorted, green heads had grown from the receptacles of severely affected flower heads. A presumptive fluorescence test with 4′,6-diamidino-2-phenylindole staining was positive for phytoplasmalike bodies in phloem sieve elements in the midveins of leaves from a symptomatic plant. Nested polymerase chain reaction (PCR) amplification of extracted DNA with phytoplasma-specific oligo-nucleotide primer pairs (1,2) confirmed the presence of phytoplasmas in this plant. Based on restriction fragment length polymorphism analysis of the PCR products, the associated phytoplasma was identified as phytoplasma 16S rRNA group I (aster yellows [AY] and related phytoplasmas), subgroup A. This is the first report of a host of the AY phytoplasma in the genus Echinacea. Because no attempt was made to transfer the phytoplasma via leafhoppers, the potential for purple coneflower to be a source of inoculum is unknown.

References: (1) D. E. Gunderson and I.-M. Lee. Phytopathol. Mediterr. 35:144, 1996. (2) I.-M. Lee et al. Phytopathology 84:559, 1994.
First Report of Puccinia striiformis f. sp. tritici on Wheat in South Africa
Authors: Pretorius Z. A. , Boshoff W. H. P. , Kema G. H. J.
Published: May 2007

During August 1996, stripe (yellow) rust, caused by Puccinia striiformis f. sp. tritici, was observed for the first time on bread wheat (Triticum aestivum) in the Western Cape, South Africa. Ensuing surveys during the growing season indicated that stripe rust occurred throughout most of the wheat-producing areas in the winter rainfall regions of the Northern, Western, and Eastern Cape provinces. The disease was also observed on irrigated wheat in the summer rainfall area south of Kimberley. Stripe rust was most severe in the Western Cape, where prolonged cool and wet conditions favored epidemic development and necessitated extensive and often repeated applications of triazole fungicides. Due to spike infection and destruction of foliage, significant losses in grain quantity and quality occurred in certain fields. Avirulence/virulence characteristics of 32 stripe rust isolates, collected from commercial wheat fields, trap nurseries, and triticale, were determined on 17 standard differential wheat lines and seven supplementary testers supplied by C. R. Wellings, Plant Breeding Institute, Cobbitty, Australia. All isolates were representative of one pathotype, characterized by avirulence to Chinese 166 (Yr1), Vilmorin 23 (Yr3), Moro (Yr10), Strubes Dickkopf, Suwon 92/Omar, Clement (Yr2,9), Triticum aestivum subsp. spelta var. album (Yr5), Hybrid 46 (Yr4), Reichersberg 42 (Yr7), Heines Peko (Yr2,6), Nord Desprez (Yr3), Carstens V, Spaldings Prolific, Heines VII (Yr2), Federation*4/Kavkaz (Yr9), and Avocet-S/Yr15, and by virulence to Kalyansona (Yr2), Heines Kolben (Yr2,6), Lee (Yr7), Compair (Yr8), and Federation 1221. Cultivars Trident (Yr17), Avocet-R (YrA), and Selkirk (YrSk) appeared heterogeneous for stripe rust reaction. The pathotype resembled race 6E16, previously detected in East and North Africa, the Middle East, and western Asia. Pathotype identity was confirmed at IPO-DLO, Wageningen, using one South African isolate of P. striiformis f. sp. tritici. In view of the rapid dispersal of the pathogen during 1996, susceptibility of several high-yielding cultivars, and favorable climatic conditions in many wheat-growing areas, stripe rust is considered potentially damaging to South African wheat production. Field observations and seedling tests have shown, however, that certain cultivars are resistant to the introduced pathotype. At present the genetic basis of this resistance is largely unknown.
Reduced Dosage of Methyl Bromide for Controlling Verticillium Wilt of Potato in Experimental and Commercial Plots
Authors: Gamliel A. , Grinstein A. , Peretz Y. , Klein L. , Nachmias A. , Tsror L. , Livescu L. , Katan J.
Published: May 2007

The use of gas-impermeable films to reduce the dosage of methyl bromide (MB) required to control Verticillium wilt in potatoes was examined in field experiments, conducted in soils naturally infested with Verticillium dahliae. The incidence and severity of Verticillium wilt were significantly reduced (by 74 to 94%) by fumigation with MB at 50 g/m2 under standard low density polyethylene (LDPE) or at 25 g/m2 under gas-impermeable films. Fumigation at 25 g/m2 under LDPE was less effective. Disease severity was inversely correlated (r2 = 0.89 to 0.91) with chlorophyll content in the leaves. Fumigation also reduced (by 89 to 100%) stem colonization by the pathogen. Potato yield in the fumigated plots was significantly higher (26 to 69%), than in their nonfumigated counterparts, and was inversely correlated with disease index (r2 = 0.69 to 0.9). The percentage of high-value tubers (above 45 g) was 52 to 56% of total yield in the fumigated plots as compared with 32 to 40% in the nonfumigated controls. Thus, fumigation also improved the commercial quality of tuber yield. Effective control of V. dahliae and yield increases following MB fumigation at the recommended dosage or at a reduced dosage with gas-impermeable films was also observed in a consecutive crop. These results were verified in a large-scale field experiment using commercial applications, further demonstrating the feasibility of reducing MB dosages under farm conditions, without reducing its effectiveness in terms of disease control and yield improvement.
First Report of Mucor Rot in Commercially Sold Cherries Caused by Mucor piriformis
Authors: Sholberg P. L. , Michailides T. J.
Published: May 2007

In August 1996, a commercial retailer of high quality cherries from the Okanagan Valley of British Columbia, Canada, reported severe losses in at least 150 boxes (11.3 kg per box) of packed cherries cv. Stella. Upon examination of a representative box of these cherries, it was found that approximately 80% of the fruit was affected by what appeared to be Mucor spp. The decayed cherries were concentrated below the surface layer and small pockets of cherries had prominent salt-and-pepper-colored whiskers emanating from individual cherries. Counting the exact number of rotten cherries was difficult because they disintegrated on handling. Several infected cherries were surface sterilized by immersing in a 0.5% NaClO solution for 1 min and rinsing with sterile, distilled water. Pieces of the surface-sterilized cherries were plated onto dishes containing potato dextrose agar and incubated at 6°C for 10 days. Ten typical isolates derived from single spores from these dishes were all identified as Mucor piriformis A. Fischer (1). Samples of 200 g of cherries cv. Sweetheart (20 ± 1 cherries) were sprayed with a water suspension containing 1 × 106 sporangiospores per ml with one of the isolates identified as M. piriformis and incubated at 1, 6, 10, 15, and 20°C for up to 25 days. This same procedure was repeated for two other isolates of M. piriformis isolated from infected cherries. As a control, cherries were misted with sterile water and incubated at 20°C for 6 days. At 6°C, a temperature at which cherries are often stored, the three isolates decayed, respectively, 100, 60, and 60% of the cherries in 18 days. In general, all three isolates caused greater than 50% decay at 20, 15, 10, and 1°C in 6, 6, 11, and 25 days, respectively. Decay did not occur in cherries misted only with sterile water. Careful visual examination of decayed cherries revealed similar whiskerlike growth of Mucor as seen in the commercial cherries. Microscopic examination of sporangiophores infecting the fruit found them to be the same as the original M. piriformis isolate, successfully completing Koch's postulates. Previous to this report, M. piriformis, M. hiemalis, and M. plumbeus were isolated from Lambert cherries stored for 4 weeks at 4.5°C in Oregon (2); however, it is unclear if all or any of these isolates were pathogenic because pathogenicity tests were not conducted.

References: (1) T. J. Michailides and R. A. Spotts. Plant Dis. 74:537, 1990. (2) P. G. Sanderson and R. A. Spotts. Fungic. Nematic. Tests 47:43, 1992.
Wood Decay Associated with Pileated Woodpecker Roosts in Western Redcedar
Authors: Parks C. G. , Raley C. M. , Aubry K. B. , Gilbertson R. L.
Published: May 2007

The pileated woodpecker (Dryocopus pileatus) is a species of concern to forest managers because it uses cavities in large snags and decadent trees for nesting and roosting. A radio-telemetry study of pileated woodpeckers on the Olympic Peninsula of western Washington (1) found that large western redcedar (Thuja plicata Donn ex D. Don) were frequently used for roosting. These roost trees were partially hollow or softened by internal decay. Western redcedar is thought to be less susceptible to most fungal pathogens than are other conifers. This misconception probably arose because of the high resistance to decay of cedar heartwood under service conditions. Many heartwood fungi do, however, attack living redcedar during their lifespan (often over 1,000 years), and large western redcedar have a high incidence of heartwood decay (2). Two to four wood cores were removed below openings used by radio-tagged woodpeckers at heights of 7.5 to 10.5 m on each of 10 large (200 to 300 cm diameter at 1.4 m above ground), living western redcedars. Wood samples were cultured on malt extract agar. No pure cultures of wood-decay fungi were obtained from two trees, although the samples were visually decayed. Oligoporus sericeomollis (Romell) Bondartzeva (= Poria asiatica (Pilát) Overh.) was the only wood-decay fungus isolated from the remaining eight trees. O. sericeomollis causes a brown, cubical heartrot in living western redcedar. In late stages of decay, the rot column typically forms a piped or tubular shape, can extend 25 or more meters up the bole of the tree, and can spread out into large branches (2). Pileated woodpeckers often roost in large, longitudinal tree cavities having multiple openings that provide a means of escape from potential predators. The decay columns produced by O. sericeomollis may create optimal roosting conditions in western redcedar for pileateds. During the telemetry study, woodpeckers were observed entering redcedars at one opening, but exiting from another opening some distance away. Large western redcedars that contain heartrot before they die may be particularly important to pileated woodpeckers because these trees persist in the landscape and provide potential roost sites far longer than other tree species in western Washington, perhaps even for centuries. Information from this and similar studies may be useful for developing inoculation techniques that use fungi with specific decay characteristics to create habitat for woodpeckers.

References: (1) K. B. Aubry and C. M. Raley. Northwest Env. J. 6:432, 1990. (2) D. C. Buckland. Can. J. Res. C. 24:158, 1946.
Clonal Variations and Virus Regulation by Aphids in Transmission of a French PAV-Type Isolate of Barley Yellow Dwarf Virus
Authors: Guo J.-Q. , Lapierre H. , Moreau J.-P.
Published: May 2007

Twenty-one aphid clones of Rhopalosiphum padi and 21 clones of Sitobion avenae were evaluated for vector efficiency in transmitting a French PAV-type isolate (PAV-RG) of barley yellow dwarf virus (BYDV). All aphid clones transmitted the isolate, but vector efficiency was variable. The most efficient R. padi clone transmitted PAV-RG about twice as often as the least efficient one, Rp-CH (93 versus 38%). The most efficient S. avenae clone, however, transmitted PAV-RG eight times more often than the least efficient one, Sa-R5 (76 versus 8%). All aphid clones acquired virus as determined by triple antibody sandwich-enzyme-linked immunosorbent assay (TAS-ELISA), but the amount of virus acquired differed among the clones. After a 5-day inoculation access period on healthy plants, virus titer in some aphid clones was not detectable by TAS-ELISA in samples of 10 aphids, but immunocapture-polymerase chain reaction (IC-PCR) could detect the virus in the extract of single aphids of all the clones. In most cases, a rapid reduction of PAV-RG titer in the aphids was associated with lower transmission efficiency. In a serial transmission test of 11 days, clonal variations in vector efficiency were consistently observed. After a 5-day transfer, vector efficiency of the six clones tested declined. Vector efficiency was significantly correlated with the level of virus titer in the aphids. Following the serial transfer, decline of virus titer in feeding aphids was triphasic, with an initial decrease occurring rapidly after the first transfer, then decreasing slowly. A second rapid reduction in virus titer often occurred after 7 days of transfer. In the serial transmission test, all three R. padi clones tested transmitted and retained virus until the last transfer at 11 days. The Sa-Chat1 and Sa-V clones of S. avenae successively transmitted and retained PAV-RG for 11 and 9 days, respectively. The Sa-R5 clone transmitted PAV-RG until the 9-day transfer, but retained the virus for 11 days. Thus, the clonal variations in vector efficiency were not ascribed to poor ability to acquire the virus, but were associated with a possible transmission barrier of virions, as well as a more rapid reduction of virus titer in aphids.
Waste Corn as a Point Source of Inoculum for Aspergillus flavus in the Corn Agroecosystem
Authors: Olanya O. M. , Hoyos G. M. , Tiffany L. H. , McGee D. C.
Published: May 2007

Sporulation of Aspergillus flavus was detected on kernels in deposits of waste corn close to corn storage cribs and bins at 18 locations throughout Iowa in 1991 and 1992. A. flavus was detected in spore traps located 3 m from the deposits and was isolated from nitidulid beetles within the deposits or in insect traps within 3 m of the deposits. A. flavus also was isolated from asymptomatic corn kernels in the deposits and from soil beneath the deposits. Linear dispersal gradients of airborne conidia of A. flavus, sampled at distances of 2, 6, 10, and 14 m from waste corn deposits into adjacent cornfields, were detected at three sampling times between 28 July and 1 September 1992 at Cedar Rapids and Williamsburg, Iowa. Linear dispersal gradients from the deposits also were detected for A. flavus-infested nitidulid beetle species Carpophilus lugubris and Glischrochilus quadrisignatus. The incidence of A. flavus infection on corn leaves, silks, and kernels in the fields adjacent to the deposits were correlated to numbers of airborne conidia at each sampling time at both locations. In a field experiment in Ames in which waste corn was placed in the center of individual corn plots, linear dispersal of conidia of A. flavus and plant infection gradients similar to those found from natural deposits were detected at distances of 1.7 to 8.5 m from the deposits at four sampling times from 6 August to 26 September 1992. Few airborne conidia of A. flavus were detected, and no infection of leaves, silks, and kernels by A. flavus occurred in the corresponding noninfested control plots. This study showed that deposits of waste corn infested with A. flavus found in the vicinity of corn storage cribs and bins are point sources of inoculum for A. flavus in the corn agroecosystem.
Performance of Four New Leaf Rust Resistance Genes Transferred to Common Wheat from Aegilops tauschii and Triticum monococcum
Authors: Hussien T. , Bowden R. L. , Gill B. S. , Cox T. S. , Marshall D. S.
Published: May 2007

The objective of this study was to test the performance of four new wheat leaf rust resistance genes previously transferred from wild relatives of common wheat. Leaf rust resistance gene Lr43, in wheat germplasm line KS92WGRC16, was originally from Aegilops tauschii. A second resistance gene, in line KS92WGRC23, was transferred from Triticum monococcum var. monococcum. Two other genes, in lines KS93U3 and KS96WGRC34, were obtained from T. monococcum var. boeoticum. In greenhouse tests, the typical low infection types produced by these lines were fleck (;), immune (0), fleck with chlorosis (;C), and heterogeneous (X-) for KS92WGRC16, KS92WGRC23, KS96WGRC34, and KS93U3, respectively. In field tests in Kansas and Texas, KS92WGRC23 and KS92WGRC16 were highly resistant. KS93U3 was moderately resistant in Kansas but moderately resistant to moderately susceptible in Texas. KS96WGRC34 was moderately resistant in Kansas but moderately resistant to susceptible in Texas. Greenhouse adult-plant tests with race PBJL of Puccinia recondita f. sp. tritici indicated that KS92WGRC16, KS92WGRC23, and KS96WGRC34 were highly resistant, but KS93U3 gave a moderately resistant reaction. Growth-chamber studies in different environments (12, 16, 20, and 24°C) showed slight temperature effects on the expression of resistance in KS96WGRC34 but not in the other lines. Tests with nine races of P. recondita f. sp. tritici indicated that only KS92WGRC16 was resistant to all the races. Races PNML and PNMQ were virulent on KS92WGRC23, and race TFGL was virulent on both KS93U3 and KS96WGRC34. The genes in the four germplasm lines should be used in combination with other resistance genes to prolong their usefulness.
Effects of Container Bases on the Spread of Meloidogyne incognita in a Hawaiian Ornamental Nursery
Authors: Ko M. P. , Schmitt D. P. , Saxby M.
Published: May 2007

The influence of container bases on nematode spread from infested pots or ground in an ornamental foliage nursery was investigated with Meloidogyne incognita as the test nematode and cowpea as the indicator plant. The container bases examined were black cloth, concrete masonry blocks, gravel, crushed cinders, and bare ground. Masonry blocks raised 46 cm above ground (raised bench) served as the control treatment. Under the standard nursery practice of irrigation by rainfall and supplemental overhead sprinkler, nematodes spread from contaminated pots or ground to adjacent nematode-free pots on all tested container bases. Incidence of spread, measured as the percentage of nematode-free pots that became contaminated, increased over time and occurred more extensively from ground to pot than from pot to pot. Ground to pot spread increased rapidly following heavy rains, indicating rain was an important contributing factor. On the M. incognita-infested nursery ground, the nematode was found more frequently associated with weeds than with bare soil, suggesting that weeds were important reservoirs of nematode inoculum for rain-splash dispersal. Placement of containers on a raised bench was more effective than on any of the unraised container bases in preventing the ground to pot spread.
Selection of Microorganisms for Biological Control of Silver Scurf (Helminthosporium solani) of Potato Tubers
Authors: Elson M. K. , Schisler D. A. , Bothast R. J.
Published: May 2007

Few management strategies exist for silver scurf, an important postharvest disease of potatoes. In this study, the microbiota of 47 agricultural soils and 7 tuber samples was screened for biological control agents of silver scurf. Soil or periderm samples were transferred to separate samples of γ irradiation-sterilized field soil enriched with potato periderm. After incubation, the samples were assayed for biological suppressiveness to silver scurf using a whole-tuber/infested soil assay. Over 430 isolates of bacteria, yeasts, and actinomycetes were recovered from tubers and soil associated with the 12 most suppressive soil samples. Thirteen strains were selected for further study on three different strains of Helminthosporium solani, including one that was resistant to thiabendazole. Microbial strains that significantly inhibited H. solani (P ≤ 0.05) in at least one experiment were identified as Pseudomonas putida (PM1), Nocardia globerula (S244), and Xanthomonas campestris (P76). Colonization studies with rifampicin-resistant strains of putative biological control agents revealed that long-term colonization of the tuber surface was not necessary to reduce disease symptoms. Highly variable levels of conidiophore production prevented selection of the single most suppressive strain. Possible sources of variability in biological control are discussed, including physiological age of the tuber, tuber infection in the field, and uneven free moisture in the storage.
First Report of Infection of Honeydew with Acidovorax avenae subsp. citrulli
Authors: Isakeit T. , Black M. C. , Barnes L. W. , Jones J. B.
Published: May 2007

Honeydew fruits (Cucumis melo var. inodorus Jacq. ‘Morning Ice,’ ‘Honeybrew,’ and ‘Green Flesh’) with circular, 3- to 10-mm-diameter lesions that did not extend into the flesh of the fruit were collected from a field in Frio County, TX, in October 1996. Lesions were either water-soaked or had a scabby center with a water-soaked edge. Non-fluorescent, gram-negative bacteria were consistently isolated from lesions. Eleven representative bacterial strains had 0.835 to 0.950 similarity to Acidovorax avenae subsp. citrulli, using Biolog GN Microplates and the MicroLog data base release 3.50 (Biolog, Hayward, CA). Strains were tested for pathogenicity on watermelon (C. lanatus (Thunb.) Matsum. & Nakai ‘Royal Sweet’) and honeydew seedlings (cv. Morning Ice) by daubing suspensions (approximately 108 CFU/ml) of bacteria onto cotyledons of 1-week-old transplants. Water soaking, followed by necrosis, occurred after 3 to 5 days. A. avenae subsp. citrulli, the causal agent of bacterial fruit blotch of watermelon, was reisolated from lesions. Detached fruit of honeydew (various cultivars) and watermelon (cv. Emperor) were surface disinfested with 70% ethanol, injected sub-epidermally with bacterial suspensions in blemish-free areas, and incubated at 24°C. Water-soaked lesions developed on fruit 10 to 14 days later and the bacteria were reisolated from inoculated fruit. Fruit inoculated with sterile water did not develop symptoms. Female flowers of honeydew plants (cv. Honeybrew) were inoculated at the time of pollination with a suspension of bacteria daubed on the fruit surface. Pollinated fruits were sealed in a moist chamber for 48 h. Circular, water-soaked spots developed 10 to 14 days later. A. avenae subsp. citrulli was reisolated from these lesions. The affected 44-ha field utilized center pivot irrigation and the incidence of diseased fruit exceeded 50%. The source of the pathogen is unknown. Bacterial fruit blotch was identified in watermelon grown under overhead irrigation 0.8 km from this honeydew field 9 weeks earlier. In past years, bacterial fruit blotch has occurred in watermelon fields in Frio County (1). Honeydew from other fields in the vicinity, including one that was also sprinkler irrigated, did not show these symptoms. This is the first report of A. avenae subsp. citrulli causing a disease of honeydew fruit.

Reference: M. C. Black et al. Plant Dis. 78:831, 1994.
First Report of Leaf Scald Disease and Ratoon Stunting Disease of Sugarcane in French Guyana
Authors: Feldmann P. , Daugrois J. , Davis M. J. , Chatenet M. , Rott P.
Published: May 2007

In December 1995, leaf scald symptoms were observed in sugarcane (Saccharum sp.) cultivar B64277 in French Guyana. Symptomatic plants occurred both in a sugarcane germplasm collection near the road between Sinnamary and Saint-Elie and in a nursery near Sinnamary. Sugarcane imported from Martinique had been used to establish the germplasm collection that in turn had been used to establish the nursery. Ten-month-old mature plants in the germplasm collection had abnormal side shoots on the lower part of the stalks and suckers (nonmillable stalks) with white scalded areas on leaves. Leaves on 1-month-old shoots in the nursery exhibited chlorosis and white, pencil-line streaks. Samples prepared from symptomatic stalks from the two locations were plated on a selective medium (1), and two isolates of Xanthomonas albilineans were recovered. Both of these isolates caused leaf scald symptoms on leaves of sugarcane cultivar B69566 inoculated by a decapitation technique, and belong to serovar 3 previously reported in the Caribbean from Guadeloupe, Martinique, and St. Kitts. The RFLP (restriction fragment length polymorphism) pattern of these two isolates was different from the 54 patterns among 218 other strains collected throughout the world (2), but similar to the pattern of a strain of serovar 3 from Martinique. This indicated that the pathogen might have been introduced with cuttings imported from Martinique. Three stalks of mature cane from varieties B5992, B64277, and R570 from the germplasm collection were tested for the presence of Clavibacter xyli subsp. xyli, causal agent of ratoon stunting disease. Immunofluorescence tests on sap (3) revealed the presence of the pathogen in the three stalks of B64277. All sugarcane plants in the nursery and the germplasm collection were destroyed by the use of glyphosate sprays in January 1996 in an attempt to arrest the spread of the two bacterial pathogens. In order to obtain healthy seed cane for future planting, a new germplasm collection of 0.6 ha and consisting of 11 cultivars was planted in January 1996 with disease-free, tissue-cultured plants provided by the CIRAD sugarcane breeding station in Guadeloupe.

References: (1) M. J. Davis et al. Plant Dis. 78:78, 1994. (2) M. J. Davis et al. Phytopathology 87:316, 1997. (3) M. J. Davis and J. L. Dean. Plant Dis. 68:896, 1984.
Sensitivity of Botrytis cinerea from Connecticut Greenhouses to Benzimidazole and Dicarboximide Fungicides
Authors: LaMondia J. A. , Douglas S. M.
Published: May 2007

Botrytis cinerea was isolated from infected plants in six greenhouses in Connecticut. Forty-five isolates were evaluated in vitro to determine fungicide sensitivity to benzimidazole (benomyl and thiophanate-methyl) and dicarboximide fungicides (vinclozolin and iprodione). B. cinerea isolates with fungicide resistance were recovered from each greenhouse sampled. Benzimida-zole resistance was more common than dicarboximide resistance (74 to 76% versus 36 to 43%, respectively). Multiple fungicide resistance was common. Nineteen isolates were resistant to both a benzimidazole and a dicarboximide fungicide. The level (EC50) of resistance to dicer-boximides was low compared with resistance to benzimidazoles. Isolate growth rate was not correlated to fungicide sensitivity or EC50. Fungicide resistance was apparently unrelated to the patterns of fungicide use in greenhouses sampled.
Variation in Pathogenicity and DNA Polymorphism Among Botrytis cinerea Isolates Sampled Inside and Outside a Glasshouse
Authors: Kerssies A. , Bosker-van Zessen A. I. , Wagemakers C. A. M. , van Kan J. A. L.
Published: May 2007

Colonies of Botrytis cinerea were obtained from spore samplers placed inside and outside a glasshouse with a rose crop. Pure cultures were made from five colonies collected on one sampling date every month throughout the year. These isolates were tested for germination on water agar and for pathogenicity on gerbera and rose petals. The germination rate of the conidia on water agar varied between 60 and 99%. Pathogenicity of the isolates on gerbera and rose flowers ranged from 14 to 166% relative to reference isolate Bc16 and varied among isolates collected on the same day as much as among isolates collected in different months. The pathogenicity of the isolates on rose flowers was overall higher than on gerbera flowers. Random amplified polymorphic DNA (RAPD) analysis was performed on 30 selected isolates with different relative pathogenicity, collected both inside and outside the glasshouse. Almost all of the isolates were genetically different. No correlation was found among pathogenicity, sampling time, sampling place, and RAPD patterns. Results are further evidence for the statement that B. cinerea inoculum in glasshouses continuously originates from many different sources in their vicinity.
Serological Detection of Grapevine Associated Closteroviruses in Infected Grapevine Cultivars
Authors: Monis Judit , Bestwick Richard K.
Published: May 2007

Western blot immunoassay and enzyme-linked immunosorbent assay using different monoclonal antibodies (MAb) and polyclonal antisera (PA) revealed mixed infections of serologically related and unrelated grapevine leafroll associated viruses (GLRaVs) and grapevine corky bark associated virus (GCBaV) in symptomatic grapevines. A PA designated rootstock-scion incompatibility (RSI)-24 kDa, grapevine corky bark PA, and GLRaV-2b MAb reacted to polypeptides of approximately 24 kDa isolated from grapevines exhibiting rootstock-scion incompatibility, leafroll, and corky bark disease symptoms, suggesting that these isolates are infected with closely related viruses. A PA designated GLRaV-2 US detected virus specific polypeptides of 38, 37, 36, and 24 kDa, while a polyclonal antiserum designated GLRaV-2 FR detected a single virus-specific polypeptide of approximately 24 kDa. The reactivity of GLRaV-2 US to various polypeptides suggests that the immunogen used to produce this antiserum was a mixture of viruses. Apical meristems were excised and cultured to eliminate the infection of viruses in the grapevines showing RSI symptoms and in the cultivar French Colombard infected with GLRaV-1. The elimination of these viruses was confirmed by Western blot assay. These studies show that the Western blot assay can be used to detect and differentiate grapevine disease-associated closteroviruses.
Ascochyta fabae and A. lentis: Host Specificity, Teleomorphs (Didymella), Hybrid Analysis, and Taxonomic Status
Authors: Kaiser W. J. , Wang B.-C. , Rogers J. D.
Published: May 2007

Isolates of Ascochyta fabae from faba bean (Vicia faba) and A. lentis from lentil (Lens culinaris) collected from different countries were used in this study. The Didymella teleomorph (sexual state) of each fungus was induced to develop and mature on inoculated sterile lentil stems. Both fungi were heterothallic, with two mating types, designated MAT1-1 and MAT1-2. When certain isolates of A. fabae and A. lentis were crossed, hybrid pseudothecia developed. Growth, sporulation, colony appearance, morphology, and pathogenicity of the hybrid progeny frequently differed greatly from the parent isolates. Inoculations with single-ascospore progeny from matings among compatible isolates of A. fabae caused disease in faba bean but not in lentil; inoculations with single-ascospore progeny from matings among compatible isolates of A. lentis incited disease in lentil but not in faba bean. Inoculations with single-ascospore progeny from crosses between faba bean and lentil isolates did not induce disease in either host. Asci from crosses between A. fabae and A. lentis mostly contained fewer than eight ascospores that were, on average, larger than those from eight-spored asci. Matings among certain isolates of A. fabae resulted in production of pseudothecia with ascospores considerably larger than is typical for D. fabae. Random amplified polymorphic DNA (RAPD) banding patterns of Ascochyta isolates from faba bean and lentil are clearly different, and banding patterns from hybrid progeny from crosses between A. fabae and A. lentis confirmed hybridity. RAPD markers proved useful in supporting identifications of ascospore isolates from faba bean to known Ascochyta species. Dendrogram analysis indicated similarity between the two fungal species was low. The pathogenicity tests, morphological characteristics, and RAPD markers indicate that A. fabae and A. lentis represent distinct taxa. D. lentis, with its anamorph, A. lentis, is proposed as a new species that is distinct from D. fabae, with its anamorph, A. fabae.
First Report of Sorghum Ergot Caused by Sphacelia sorghi in Mexico
Authors: R. J. Aguirre , A. H. Williams , G. N. Montes , Cortinas-Escobar H. M.
Published: May 2007

In the winter of 1996-1997 ergot was observed in sorghum (Sorghum bicolor) plants growing in several locations of Tamaulipas, Mexico, including San Fernando, Soto La Marina, Manuel, Cuahutemoc, and Altamira. The disease in sorghum plants was associated with high humidity and low temperatures during the blooming stage in February, 1997. The most obvious symptom was the exudation of honeydew from the infected flowers. Microscopic analysis of the honeydew revealed the presence of the asexual conidia of a Claviceps sp. The abundance, size, and shape of conidia were characteristic of Sphacelia sorghi (1). Honeydew was also observed in plants of Sorghum halepense, forage sorghum and volunteer plants of sorghum, which are also hosts. The first report of ergot in the Americas was made in 1995 in Brazil (2), where it was probably introduced via contaminated seed from Africa. The disease spread rapidly from Brazil to Argentina, Bolivia, Colombia, Paraguay, and Venezuela. The pathogen was probably dispersed and introduced to Mexico by contaminated seed, wind, or insects from South America. The disease represents a serious threat to the 800,000 ha of sorghum grown in Tamaulipas. Due to its confirmed extraordinary capacity to spread rapidly, ergot could affect sorghum growing in regions adjacent to Tamauli-pas, including Nuevo Leon in Mexico, and Texas in the U.S.

References: (1) D. E. Frederickson et al. Mycol. Res. 95:1101, 1991. (2) E. M. Reis et al. Plant Dis. 80:463, 1996.
First Report of Web Blotch of Peanut Caused by Phoma arachidicola in the Dry Zone of Sri Lanka
Authors: Mikunthan G.
Published: May 2007

Foliar symptoms of web blotch were observed on some peanut cultivars (Arachis hypogaea L.) grown in the Kilinochchi district in the dry zone of Sri Lanka during October 1993 to January 1994, following heavy rains (mean relative humidity 79 to 85%, mean temperature 25 to 27°C). Severe symptoms appeared on peanut cultivars ICGS 11 and ICGS 121. Cultivar ICGS 11 belongs to the Spanish group (A. hypogaea subsp. fastigiata var. vulgaris) and ICGS 121 belongs to bunch type (A. hypogaea subsp. hypogaea var. hypogaea). Initial symptoms of small, irregular, brown to reddish brown lesions along the midrib of both young and old leaves were observed. Large, nearly circular tan or dark brown blotches appeared on the adaxial surface of the leaves. Older lesions became dried and cracked. Lesions on the abaxial surface were pale brown, and less pronounced. These observations correlate closely with those made by Taber (2). Severe defoliation was observed in the infected fields of Spanish cultivars. Phoma arachidicola Marasus, G. D. Pauer, & Boerema was consistently isolated from symptomatic tissue. Colonies on potato dextrose agar were at first creamy white, and flattened with little aerial growth. Colonies eventually turned dark brown with a wide appressed margin. All isolates produced pale to dark brown and globose pycnidia. Dark-colored, globose, beaked pseudothecia were also observed in cultures, as reported by Subrahmanyam et al. (1). Dark-colored, round, single-celled pycnidiospores measuring 4 to 9 × 2.5 to 4 µm were observed in culture. The fungus was inoculated onto the leaves of 10 healthy plants of each cultivar and another 10 plants were maintained as uninoculated controls. All plants were covered with polypropylene bags to increase the humidity. Plants inoculated with the fungus produced symptoms 7 to 9 days after inoculation similar to those observed in the field. None of the control plants showed any disease symptoms. The fungus was reisolated from the diseased leaf tissue. Microscopic examination confirmed the identity of the fungus and satisfied Koch's postulates. All cultivars were then grown under irrigation during February to May 1994 (mean relative humidity 60 to 70% and mean temperature 32 to 35°C). No disease symptoms were observed, indicating that the proliferation of P. arachidicola on Spanish cultivars was influenced when the crop establishment period coincided with low air temperature (25 to 27°C) and high relative humidity (79 to 85%). This is the first report of web blotch in Sri Lanka and its occurrence was confined to the dry zone areas of the country.

References: (1) P. Subrahmanyam et al. 1994. Web blotch disease of groundnut. Inform. Bull. No. 43, ICRISAT; and Peanut Collaborat. Res. Support Prog. (2) R. A. Taber. Web blotch. Pages 9–10 in: Compendium of Peanut Diseases. D. M. Porter, D. H. Smith, and R. Rodrigues-Kabana, eds. American Phytopathological Society, St. Paul, MN, 1984.
Cleistothecia of Uncinula necator—An Additional Source of Inoculum in Italian Vineyards
Authors: Cortesi Paolo , Bisiach M. , Ricciolini M. , Gadoury David M.
Published: May 2007

Density and viability of populations of cleistothecia of Uncinula necator from bark, leaves, and soil were determined in three vineyards in the Florence and Siena provinces of Tuscany for 3 years. A higher density of cleistothecia was found on fallen leaves than on bark. However, the percentage of viable cleistothecia was higher on bark. No viable cleistothecia were recovered from soil. U. necator overwintered as mycelium in dormant infected buds, which gave rise to flag shoots, only in Santa Cristina, where 20 and 92 flag shoots per hectare were detected before bloom in 1994 and 1995, respectively. Disease incidence and severity increased similarly at Corti, Fornace, and at Santa Cristina, although powdery mildew epidemics started from ascospores only in Corti and Fornace, whereas flag shoots were present at Santa Cristina. Cleistothecia were formed in autumn in both 1994 and 1995, and their dispersal started in late September to mid-October, with the maximum number of cleistothecia trapped in funnels during the second half of October. Cleistothecia appear to function as the sole source of primary inoculum for grape powdery mildew in some Italian vineyards and serve as additional sources of inoculum where the pathogen also overwinters in infected buds. In Australia but not in New York, the pathogen also overwinters as cleistothecia on fallen leaves.
Germinability of Teliospores of Tilletia indica after Hot Water and Sodium Hypochlorite Treatments
Authors: Smilanick J. L. , Hershberger W. , Bonde M. R. , Nester S. E.
Published: May 2007

Hot water and sodium hypochlorite (NaOCl) were evaluated to eradicate teliospores of the Karnal bunt fungus, Tilletia indica, for the purpose of decontaminating grain storage and handling equipment. The germinability of free teliospores and teliospores within the sori of infected wheat was assessed. Temperatures of 25, 60, and 80°C, NaOCl concentrations (wt/vol, pH 11.5) of 0, 0.53, and 1.60%, and immersion periods of 1, 5, 15, and 30 min were evaluated. In other tests, the influence of pH on NaOCl potency and of a delay between treatment and water rinsing were evaluated. Immersion at 80°C in water alone or with NaOCl killed both free teliospores and those within the sori of infected seeds within 1 min. NaOCl at 1.60% at 25°C killed teliospores suspended in water within 15 min, but some teliospores inside sori survived 30 min of this treatment. NaOCl adjusted to pH 8 before use was superior to NaOCl at pH 11.5. An application of 1.60% NaOCl at 25°C for 5 min followed by a 10-min delay before the seeds were rinsed in fresh water killed free teliospores but not all teliospores within sori. This treatment was more effective than the 5-min treatment alone but inferior to the 15-min treatment with NaOCl at a concentration of 1.60%. Because teliospores within the sori of infected seeds are partially protected and much more resistant to NaOCl, we recommend the removal and disposal of seeds from equipment before the treatments are applied. NaOCl radically altered the appearance of the teliospores, leaving a persistent visual indication that they had been treated, while hot water treatment alone did not. Therefore, it is beneficial to add NaOCl to hot water, although the improvement in the sporicidal efficacy was often small.
Incidence of Fusarium spp. in Asparagus Spears
Authors: Guerrero Cosme , Nigh E. L. , Stanghellini M. E. , Elmer W.
Published: May 2007

Fusarium proliferatum and F. oxysporum have been identified as causal agents of asparagus decline in the field and have been associated with reduction in spear quality (1,2). Our objective was to determine the origin and incidence of spear infection by these fungi during the cropping years 1994 to 1997. From 15 to 40 asparagus samples were randomly selected from the field, packing houses, and retail markets and assayed for Fusarium spp. Collections were made in California, Connecticut, Peru, Mexico, and Australia. The number of samples varied between sampling sites and for the time of harvest season. One Mexican collection site was sampled at the beginning, mid-point, and end of the harvest season to evaluate influence of decreasing carbohydrate levels and increasing temperatures on infection and growth of the fungi. Isolations included sections (5 to 6 cm) from the basal and terminal portions of the spear to evaluate postharvest growth in the spear. Fusarium spp. were recovered from spear samples that included all geographical sampling locations (mean 45%, range 20 to 90%). F. proliferatum was the dominant species isolated consistently from the desert areas regardless of harvest period. The frequency of F. oxysporum isolation ranged from 2 to 32% with no correlation to time or location of sampling. Basal sections were more frequently infected (94%) than terminal portions of the spear (less than 6%). No major differences in the percentage of infected spears were found in collection sites regardless of country sampled. There were differences in the incidence of infection between harvest sample dates. Spears sampled late in the harvest period were 57% more infected than spears of early or mid-season collections. Samples from the same fields, regardless of whether collected directly from the field, from packing sheds, or from the retail market, had higher infection rates later in the harvest season compared with earlier harvests. This may be attributable to warmer temperatures, changes in levels of carbohydrates, or other physiological factors. Spears harvested from the field that were infected with both Fusarium spp. had a greater incidence of infection than spears recovered from packing houses or from retail sources. This supports the theory that the source of spear infection is diseased crowns and not postharvest sources. Isolates from the spears of both Fusarium spp. were found to be pathogenic when challenged to asparagus seedlings.

References: (1) R. G. Grogan and K. A. Kimble. Phytopathology 49:122, 1959. (2) W. Schreuder et al. Plant Dis. 79:177, 1995.