bluuebunny/crossref_metadata_2025 huggingface dataset:
Selection For Resistance and Tolerance to Oat Mosaic Virus and Oat Golden Stripe Virus in Hexaploid Oats
Authors: Walker Scott L. , Leath Steven , Murphy J. Paul , Lommel Steven A.
Published: May 2007

Coker 716, a hexaploid oat cultivar resistant to both oat mosaic virus (OMV) and oat golden stripe virus (OGSV) was crossed to three susceptible cultivars (Brooks, Madison, and Tech) to form three individual populations. Individual breeding lines were derived from each cross in the F2 generation and tested in plots consisting of equally spaced individual hills in OMV- and OGSV-infested soils and non-infested soils to evaluate resistance and yield loss of individual lines. Foliar symptoms, harvest index, and yield loss were examined as selection criteria for resistant genotypes. The study was conducted over 2 years at two North Carolina locations that differed in soil type and climate. Multiple regression models describing yield loss in each cross due to rating, year, and location were calculated. Coefficients of multiple determination in these models ranged from 0.39 to 0.51. Yield loss ranged from 39 to 60% among different crosses. Infection by OMV and OGSV accounted for the majority of yield loss in two of the populations. Disease severity varied widely over years and locations. The results suggest that selection of lines with symptomatic tissue of 10% or less, or selection of tolerant lines, is needed for breeding progress.
Assessment of Laboratory Methods for Evaluating Potato Tubers for Resistance to Late Blight
Authors: Dorrance Anne E. , Inglis Debra Ann
Published: May 2007

Two laboratory methods (whole tuber and tuber slice) were evaluated and compared with field assessment of potato tubers for resistance to late blight caused by Phytophthora infestans. Altogether, the resistance responses of 20 cultivars and advanced selections were compared by the three methods. All three assays separated materials into resistant and susceptible groups. The majority of cultivars and advanced selections did not react in the same way within the field and tuber-slice assays but did react similarly within the whole-tuber assay. Some cultivars were susceptible in the field at harvest but were resistant in the whole-tuber assay. The differences may be due to the extent of lenticel and eye development during tuber formation. In contrast, other cultivars resistant in the field at harvest were susceptible in the whole-tuber assay. In this case, placement in the hill may affect whether or not the tuber is exposed to inoculum or whether aging of tubers during storage affects susceptibility to tuber blight. Our study shows that high levels of tuber resistance are available in certain commercial cultivars and advanced potato selections. For laboratory assessments to be reliable, however, both pre- and poststorage evaluations may be necessary.
Reoccurrence of Rose Bloom Caused by Exobasidium oxycocci in Cranberry in Massachusetts
Authors: Caruso F. L.
Published: May 2007

Cranberry (Vaccinium macrocarpon Ait.) vines (cv. Howes) from a commercial cranberry bed on Nantucket Island displayed typical symptoms of rose bloom disease in June, 1997. The affected area (1.5 × 30.0 m) consisted of less than 1% symptomatic uprights and was not covered by sprinkler heads of the chemigation system. The same area that did not receive insecticides or fungicides was damaged by black-headed fireworm (Rhopobota naevana) feeding during the 1996 growing season. The surface of the leaves on the abnormal branches displayed the typical white, powdery external appearance, which consisted of basidia and basidiospores of the pathogen Exobasidium oxycocci Rostr. ex Shear that were hyaline, fusiform with a slight curvature, and measured 14 to 18 × 2 to 3 μm, matching a previous description (2). Plants showing symptoms had been infected during 1996. Abnormal lateral shoots with swollen pink leaves grew from infected axillary buds on the previous year's wood (3). Cranberry plants were inoculated with basidiospores but symptoms may take longer than 1 year to develop. Rose bloom was formerly a common disease affecting cranberry in Massachusetts and control strategies were addressed in the disease management recommendations sent out by the Cranberry Experiment Station to growers through 1954. Bergman (1) reported that the disease was found almost every year before 1945, but since then there were no serious outbreaks, possibly due to changes in cultural practices. The fungicide ferbam (ferric dithiocarbamate) largely replaced Bordeaux mixture as a fungicide to combat fruit rot in the late 1940s. The disease was not brought in with imported vines from the Pacific Northwest, where the disease is common, because the vines in this bed were planted in 1910. The disease has not been observed in either wild or abandoned cranberry beds that have not received fungicide applications. This is the first report of this disease in Massachusetts in nearly 50 years.

References: (1) H. F. Bergman. 1953. Yearbook of Agriculture, p. 792. (2) F. L. Caruso and D. C. Ramsdell, eds. 1995. Compendium of Blueberry and Cranberry Diseases. American Phytopathological Society, St. Paul, MN. (3) C. L. Shear et al. 1931. U.S. Dep. Agric. Tech. Bull. 258.
First Report of Black-Foot Disease, Caused by Cylindrocarpon obtusisporum, of Grapevine in California
Authors: Scheck H. J. , Vasquez S. J. , Gubler W. D. , Fogle D.
Published: May 2007

Black-foot disease, caused by Cylindrocarpon obtusisporum (Cook & Harkn.) Wollenweb., impacts young table and wine grape (Vitis vinifera) plantings throughout California. Two- to 5-year-old grapevines showed reduced vigor with small-sized trunks, shortened internodes, uneven wood maturity, sparse foliage, and small leaves with interveinal chlorosis and necrosis. In cross-section, trunks showed dark brown to black streaking in a few to most of the vascular elements. Symptoms included a reduction in root biomass and root hairs with sunken, necrotic root lesions. Pith of affected vines was compacted and discolored. Isolations made from roots, vascular elements, and pith tissue consistently yielded colonies of C. obtusisporum as verified by descriptions in standard texts. Koch's postulates were completed by dipping the roots of cv. Carignane seedlings in a 108 spore per ml suspension for 30 min. Plants were repotted in an artificial soil mix and held in a controlled environment facility at 24°C. Typical black-foot symptoms developed on 92% of the plants within 8 weeks. Control plants dipped in distilled water remained healthy. Cylindrocarpon destructans, a species closely related to C. obtusisporum, was first reported to cause “black-foot disease” on young vines in 1961 (2). In 1975, C. obtusisporum was reported to produce similar “black-foot” symptoms (1). We propose the common name Cylindrocarpon black-foot disease be used with both species.

References: (1) S. Grasso et al. Vitis 14:36, 1975. (2) D. R. Maluta and P. Larignon. Viticulture 11:71, 1991.
Pyricularia Leaf Spot: A New Disease of Ornamental Plants of the Family Marantaceae
Authors: Pappas Athanassios C. , Paplomatas Epaminondas J.
Published: May 2007

A severe leaf spot disease incited by the fungus Pyricularia oryzae was identified on Ctenanthe oppenheimiana and C. setosa “Greystar.” Primary symptoms on young leaves consisted of individual circular to slightly irregular pinpoint spots with white necrotic centers zonated by narrow brown-yellow halos. On mature leaves, extended necrotic areas resembling those caused by phytotoxicity were formed. Artificially inoculated leaves with a spore suspension of the isolated fungus from the above case showed symptoms after 3 to 4 days' incubation at 25°C and high humidity. Fungal isolates obtained from Ctenanthe plants of Brazilian origin were found to be highly pathogenic on various plants within the family Marantaceae when they were tested by an excised leaf assay method. By contrast, P. oryzae isolates obtained from rice plants grown in Greece caused either hypersensitivity or immune response symptoms in various Marantaceae. Analysis of esterase and lactate dehydrogenase isozymes showed different banding patterns for rice and Ctenanthe isolates of P. oryzae. Conditions of prolonged leaf wetness combined with prevailing high temperature and humidity favored the epidemic appearance of the Pyricularia leaf spot disease on glasshouse-grown plants during the summer months of 1995 in Greece.
Genetic Basis and Monitoring of Resistance of Botryotinia fuckeliana to Anilinopyrimidines
Authors: Hilber Urs W. , Hilber-Bodmer Maja
Published: May 2007

The anilinopyrimidines constitute a new class of mainly protective, broad-spectrum fungicides with a high activity against Botryotinia fuckeliana, the causal agent of gray mold on a wide range of host plants. The present study was initiated to investigate the genetic basis of resistance to anilinopyrimidines in B. fuckeliana and to assess the frequency of resistant isolates in vineyards in Switzerland exposed to experimental applications of anilinopyrimidines. In mating experiments, two sensitive reference isolates were crossed with three anilinopyrimidine-resistant field isolates. The analysis of 72 sexual progeny from six apothecia demonstrated that resistance to the anilinopyrimidine fungicide cyprodinil segregated in a 1:1 ratio and is therefore monogenic. The same segregation ratio was found for resistance to the dicarboximide fungicide vinclozolin. Resistance to cyprodinil segregated independently from resistance to vinclozolin. From 1993 to 1995, isolates of B. fuckeliana were collected in Switzerland from five vineyards that differed in their anilinopyrimidine spray history. Of a total of 303 isolates tested in vitro, three anilinopyrimidine-resistant isolates were detected in two vineyards where the cumulative number of treatments was between two and nine. The results of the study are discussed with respect to the implementation of an antiresistance strategy in Switzerland.
Variability in Coat Protein Sequence Homology Among American and European Sources of Strawberry Vein Banding Virus
Authors: Mráz I. , Petrzik K. , Šíp M. , Fránová-Honetšlegrová J.
Published: May 2007

Strawberry vein banding virus (SVBV) isolates from North America, Czech Republic, Norway, and Germany were collected and their variability was determined by dot blot hybridization and confirmed by sequencing of a 431-nucleotide fragment from the middle part of the coat protein gene. Two different substitutions were found between the American and two Czech SVBV isolates, but the other isolates were identical in the compared region to the American isolate. Digoxigenin-labeled probes were prepared from these isolates and used for hybridization with polymerase chain reaction-amplified fragments of 26 Czech SVBV field isolates. No significant differences in the hybridization signal were found with any combination of samples and probes. These results show that the European isolates probably originate from a common ancestor and may have been introduced to Europe from America with planting or breeding material.
Distribution of Xylella fastidiosa in Oaks in Florida and Its Association with Growth Decline in Quercus laevis
Authors: Barnard E. L. , Ash E. C. , Hopkins D. L. , McGovern R. J.
Published: May 2007

A survey of more than 200 trees has documented the widespread occurrence of Xylella fastidiosa in Florida oak populations. The pathogen was detected readily via enzyme-linked immunosorbent assay in oaks exhibiting decline or leaf scorch symptoms and was infrequently detected in asymptomatic trees. It was also associated with reduced growth in Quercus laevis as measured by current-year shoot length. The occurrence of X. fastidiosa in Q. laevis and the evidence for its occurrence in Q. incana represent first reports for these oak hosts. The role of X. fastidiosa in oak decline scenarios deserves further attention.
Occurrence of Ergot (Sugary Disease) Incited by a Sphacelia sp. on Sorghum in Mississippi in 1997
Authors: Zummo N. , Gourley L. M. , Trevathan L. E. , Gonzalez M. S. , Dahlberg J.
Published: May 2007

Ergot (sugary disease) incited by a Sphacelia sp. was observed on Sorghum bicolor (L.) Moench var. Sweet Leaf II at Leland and Pop-larville, MS, in October 1997. The disease was characterized by droplets of a thick, sticky, semi-transparent secretion similar to aphid honeydew. The caryopsis of infected florets was converted to relatively soft, chalky pink, tumescent, immature sclerotia (1.5 to 1.7 × 4 mm) with blunt ends. Abundant conidia (11 to 17 × 5 to 7 μm) were produced on stromatic tissue and in large numbers in the sugary secretion. This fungus is similar to that described by Zummo in West Africa (2). Velazquez-Valle et al. (1) recently reported the distribution of Claviceps africana Frederiksen, Mantle & de Milliano in the United States in 1997. The Sphacelia stage of the fungus found in Mississippi is similar to that reported from other areas of the U.S. Our report extends the range for this fungus, which is contiguous to those areas reported by Velazquez-Valle et al. (1).

References: (1) R. Velazquez-Valle et al. 37th Annu. Mtg. Carib. Div., Am. Phytopa-thol. Soc., San Jose, Costa Rica, No. 77, 1997. (2) N. Zummo. 1984. Sorghum Diseases in West Africa. An Illustrated Text. USDA/USAID, Zaria, Nigeria.
Influence of Soybean Cropping Sequences on Seed Yield and Female Index of the Soybean Cyst Nematode
Authors: Young Lawrence D.
Published: May 2007

Several soybean (Glycine max) cropping sequences were planted for 12 years in a field that, at the beginning of the test, was infested with race 14 of the soybean cyst nematode, Heterodera glycines. Continuous soybean cropping sequences included H. glycines-susceptible cultivars Forrest, J82-21, Peking × Centennial breeding line, and moderately resistant cultivars Bedford and J81-116. Forrest treated with aldicarb or pentachloronitrobenzene (PCNB) plus metalaxyl and resistant breeding line JS83-236 followed by resistant cultivars Cordell and Hartwig were additional continuous soybean sequences. Rotations included two sequences each of Bedford with J81-116 or J82-21, and three sequences of Bedford with corn (Zea mays) and susceptible Essex soybean. Rotations of Bedford, corn, and Essex had 12-year mean yields significantly greater than continuous Bedford or Forrest. The female index (FI) of H. glycines on five cultivars and lines was used to bioassay changes in parasitic potential in each cropping sequence. The FI on Bedford bioassay plants increased significantly over time for all field treatments involving Bedford. When J82-21 was the bioassay plant, FI decreased significantly in treatments involving Bedford. There were no significant changes in FI for any treatment when Forrest, J81-16, and Peking were used as bioassays. Rotations of soybean cultivars with different sources of resistance and rotations of resistant and susceptible cultivars with a nonhost crop were not successful practices to manage the nematode's ability to parasitize the resistant cultivar Bedford. However, rotation of resistant and susceptible cultivars with a nonhost crop produced greater mean soybean yields and slowed the shift toward greater parasitism of the resistant cultivar sufficiently to warrant adoption of this practice.
Influence of Dew Period and Temperature on Foliar Infection of Greenhouse-Grown Tomato by Colletotrichum coccodes
Authors: Byrne J. M. , Hausbeck M. K. , Meloche C. , Jarosz A. M.
Published: May 2007

Effects of temperature, duration of leaf wetness, and leaf position on foliar infection of greenhouse-grown tomato (cv. Bonnie Best) by Colletotrichum coccodes were determined by inoculating plants with C. coccodes (5.0 × 105 conidia per ml) and keeping them in a dew chamber for 0, 4, 8, 12, 16, 20, or 24 h of wetting at 15, 20, or 25°C. One week after inoculation, leaf disks were placed on the surface of an amended medium on which colonies of C. coccodes were compact and easily identified, and severity of infection was quantified after 4, 6, and 8 days. There was no infection of plants incubated at 15°C, while plants kept at 20 or 25°C had increasing numbers of colonies when leaf wetness duration was extended beyond 12 and 8 h, respectively. Leaf position had a significant effect, with leaves tending to increase in susceptibility as they age. After 24 h of leaf wetness at 25°C, the mean number of colonies per leaf disk from top, middle, and bottom leaves was 23.8, 29.0, and 34.0, respectively.
Potential of an Indigenous Fungus, Plectosporium tabacinum, as a Mycoherbicide for Control of Arrowhead (Sagittaria trifolia)
Authors: Chung Young Ryun , Koo Suk Jin , Kim Heung Tae , Cho Kwang Yun
Published: May 2007

An isolate of the indigenous fungus Plectosporium tabacinum was isolated from arrowhead (Sagittaria trifolia) in Yusung, Korea in 1990 and evaluated in laboratory and growth chamber tests as a potential mycoherbicide. The fungus grew comparatively slowly on potato dextrose agar and corn meal agar, attaining a diameter of 65 mm after 12 days at 25°C. Conidia were mass-produced in shake-cultures or in a fermentor using potato dextrose broth containing yeast extract (0.5%, wt/vol) at 25°C. When arrowhead seedlings at the 2- to 3-leaf stage were inoculated with conidial suspensions (2 × 107 conidia/ml) and incubated in a dew chamber for 18 h at 25°C, the plants developed small, brown spots on the leaves and petioles in 2 days, and were blighted completely within 7 days after inoculation. This effect was consistent on arrowhead plants from the 2- to 5-leaf stage. Another arrowhead species, S. pygmaea, was as susceptible as S. trifolia to the pathogen. Several crops, including rice, barley, and wheat and 34 other common weed species, were immune. In small-scale field tests in paddy fields during the summers of 1992 and 1993, a mean reduction of 71.3% in the number of arrowhead plants was observed following a foliar spray of a conidial suspension (107 conidia/ml). These results indicate that P. tabacinum has potential as a selective mycoherbicide for arrowhead control.
Diallel Analysis of Diplodia Ear Rot Resistance in Maize
Authors: Dorrance A. E. , Hinkelmann K. H. , Warren H. L.
Published: May 2007

A diallel cross of seven inbreds and one synthetic line of maize were analyzed in 1994 and 1995 for their reaction to Diplodia ear rot. An additional inbred line was included in the 1995 analysis. Plants were inoculated by placing a pycnidiospore suspension (5 × 103 spores per ml) of Stenocarpella maydis in the whorl at the V14 to V15 growth stage. Crosses were evaluated for disease incidence of Diplodia ear rot at harvest, and the percentage of plants with Diplodia ear rot in a plot was used for analysis. In both years, general combining ability (GCA) effects were significant. In 1995, specific combining ability effects were also significant. There were no reciprocal effects. There was no significant interaction between year and genotypes, indicating that crosses reacted the same in both years. Inbred lines B37, H111, B68, and MS had negative GCA effects that contributed toward resistance in both years. VA26, with intermediate resistance to Diplodia ear rot, contributed toward susceptibility. Only inbred lines with a high degree of resistance should be used as parents.
Purple Blotch, Caused by Alternaria porri, on Leek Transplants in California
Authors: Koike S. T. , Henderson D. H.
Published: May 2007

In 1997, a foliar disease was detected on leek (Allium porrum) grown as transplants in California greenhouses. Initial symptoms consisted of small (less than 5 mm in diameter), circular, white leaf spots. Spots later enlarged, and became elliptical to oblong in shape and purple with tan borders in color. When spots coalesced, the leaf tips desiccated and wilted. Singly borne, brown conidia from leaves were obclavate in shape with slender, unbranched beaks extending from the narrow end of the spore body. Spore body dimensions measured 81 to 120 (96 mean) µm × 14 to 19 (16 mean) µm, and beaks measured 11 to 56 (30 mean) µm × 3 to 6 (4 mean) µm. Spore bodies had 6 to 9 transverse septa and occasionally 1 longitudinal septum. The fungus was identified as Alternaria porri (Ellis) Cif. (1). The same fungus was also consistently isolated from the margins of the spots. For pathogenicity tests, isolates were grown for 6 weeks on potato dextrose agar under a combination of one cool white and one Vita-Lite fluorescent tube on a 12 h light/dark cycle. Conidial suspensions (1.0 × 10 e 4 conidia/ml) were sprayed onto 2-month-old leek (cvs. Broad London and Gavilan). Plants were incubated in a moist chamber for 48 h and then kept in a greenhouse. After 14 days, leaf spots similar to the original symptoms developed on inoculated plants, and the pathogen was reisolated. Control plants sprayed with distilled water remained symptomless. The experiment was repeated and the results were similar. The isolates also caused leaf spots on onion (Allium cepa cv. Stockton Early Yellow) and chives (Allium schoenoprasum). This is the first report of purple blotch caused by A. porri on commercially grown leeks in California. The occurrence of this disease on leeks in enclosed greenhouses strongly suggested that the primary inoculum was seed-borne.

Reference: (1) M. B. Ellis and P. Holliday. C.M.I. Descriptions No. 248, 1970.
First Report of St. John's-Wort Anthracnose Caused by Colletotrichum gloeosporioides in Hungary
Authors: Schwarczinger I. , Vajna L.
Published: May 2007

In 1997, we observed high incidence of severe disease symptoms in a plantation of St. John's-wort (Hypericum perforatum L.) that has been cultivated as a medicinal plant in Hungary. Symptoms were characterized by brown, 2- to 15-mm-diameter, sunken lesions that girdled the stems and, when occurring near the base, killed the plants. Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. in Penz. was consistently isolated from lesions. Acervuli containing conidia and dark setae emerged from the lesions. Perithecia of the teleomorph Glomerella cingulata (Stoneman) Spauld. & H. Schrenk also appeared on stems. Plants were inoculated with conidial suspension of the fungus (2 × 107/ml), then incubated in a moist chamber for 24 h, and subsequently transferred to the greenhouse. The first symptoms appeared on stems and leaves 7 days after inoculation. Chlorotic spots grew into circular and buff-colored lesions that coalesced and then desiccated. The fungus caused severe defoliation and plant death within 2 weeks. Koch's postulates was completed by consistently reisolating the pathogen from inoculated plants. This disease on St. John's-wort has not previously been reported in Hungary. However, an anthracnose disease caused by Glomerella cingulata (Stoneman) Spauld. & H. Schrenk var. migrans Wollenweber (Gloeosporium orbiculare Berk. & Mont.) was reported in Germany in 1949 (1).

Reference: (1) H. W. Wollenweber and H. Hochapfel. Z. Parasitenkd. 14:181, 1949.
First Report of Phytophthora nicotianae Causing Leaf Blight, Fruit Rot, and Root Rot of Papaya in American Samoa
Authors: Roberts P. D. , Trujillo E.
Published: May 2007

Papaya trees (Carica papaya) were observed in 1997 with symptoms of acute chlorosis and wilting of foliage, circular whitish lesions with necrotic centers on fruits, and root and trunk rots that killed the diseased trees. Identical symptoms were observed on many trees in fields interplanted with other crops and in home gardens on two of the five islands of American Samoa. A Phytophthora sp. was consistently isolated on water agar from symptomatic stems, fruits, and roots. The fungus was grown in pure culture on V8 juice medium at 25°C under continuous fluorescent illumination, and was identified, on the basis of spherical to broadly ovoid (34 to 67 × 40 to 50 µm), intercalary to terminal sporangia, chlamydospores (20 × 40 µm), and uniform to uneven hyphae (5 to 7 µm wide), as Phytophthora nicotianae Breda de Haan (= P. parasitica Dastur) (1,2). Ten 4-week old papaya seedlings grown on pasteurized soil in 15-cm pots were inoculated with a 2-ml suspension of 100 sporangia per ml in sterile water applied to the soil surface. Six uninoculated plants were used as controls. Two mature fruit that had reached the climacteric point were inoculated with 200 µl of sterile water containing approximately 20 sporangia. Inoculum was placed inside a 1-cm-diameter rubber circle that had been attached to the surface of the fruit to prevent run-off. Two uninoculated fruits served as controls. Inoculations of seedlings and fruit were conducted three times. Wilting symptoms developed on inoculated plants in less than 5 days and plant death accompanied by crown rot occurred in 14 days. Inoculated fruit developed lesions covered with a whitish fungal growth within 10 days after inoculation. Plants and fruits exposed to sterile water were healthy. The pathogen was reisolated from the diseased plants and fruits and it was morphologically identical to the original isolate, confirming its role as the causative agent of the disease. The wide distribution of diseased plants over an estimated one-quarter of the area of the island of Tutuila (approximately 24 sq. km) and on the adjacent island of Ofu indicates that the disease was not of recent introduction.

References: (1) H. H. Hob et al. The genus Phytophthora in Taiwan. Inst. Bot., Ac. Sinica, Monogr. Ser. 15., 1995. (2) G. M. Waterhouse and J. M. Waterhouse. C.M.I. Descriptions of Pathogenic Fungi and Bacteria No. 34, 1964.
Pathogenic and Molecular Characterization of ThreePhomopsisIsolates from Peach, Plum, and Asian Pear
Authors: Uddin W. , Stevenson K. L. , Pardo-Schultheiss R. A. , Rehner S. A.
Published: May 2007

Three isolates of Phomopsis, causing shoot blight of peach, shoot tissue necrosis of plum, or bud death of Hosui Asian pear, respectively, were evaluated for their pathogenicity on apple, pear, peach, and plum. Current year's shoots of 1-year-old Stayman Winesap apple, Barlett pear, Babygold-7 peach, and Bruce plum trees were inoculated with each isolate by wounding a bud and applying agar blocks bearing young hyphae. The length of cankers on shoots was measured 10, 17, and 24 days after inoculation. Cankers developed on shoots of all hosts inoculated with the peach isolate and on peach shoots inoculated with plum and Asian pear isolates. No cankers developed on apple, pear, or plum shoots inoculated with plum and Asian pear isolates. In the first experiment, 10 days after inoculation, the length of cankers on apple trees (56.0 mm) inoculated with the peach isolate was not significantly different (P ≥ 0.05) from that on peach (42.8 mm), but was significantly greater than that on plum (25.3 mm) and pear (13.1 mm). The cankers on peach were significantly longer than those on pear, but not on plum. Cankers on all four hosts were significantly different from one another 17 and 24 days after inoculation. There was no significant difference between the length of cankers on peach shoots inoculated with plum and Asian pear isolates, and they were significantly smaller than those inoculated with the peach isolate. None of the control trees developed cankers. The three isolates differed in colony morphology, and appearance of conidiomata, conidiogenous cells, and α-conidia on potato-dextrose agar. None of the isolates produced β-conidia in culture. Multi-locus DNA fingerprint analysis and internal transcribed spacer sequence comparisons revealed similarities between the plum and Asian pear isolates but a significant difference between these two and the peach isolate. The results indicate that the Phomopsis sp. that causes shoot blight of peach has the potential to cause disease on other stone and pome fruits, and peach may also be susceptible to isolates of Phomopsis from different tree fruit hosts.
Bermudagrass Resistance to Spring Dead Spot Caused byOphiosphaerella herpotricha
Authors: Baird J. H. , Martin D. L. , Taliaferro C. M. , Payton M. E. , Tisserat N. A.
Published: May 2007

Field and greenhouse studies were conducted to evaluate the resistance of seed- and vegetatively propagated bermudagrass entries (Cynodon spp.) to spring dead spot caused by Ophiosphaerella herpotricha. In Kansas greenhouse studies, O. herpotricha caused root discoloration and root weight reductions in all entries tested. However, in Kansas field plots, root weight reductions were not different among entries and were not correlated with disease severity ratings. In an inoculated field study in Oklahoma, diseased areas ranged from 47 cm2for the entry Jackpot to 262 cm2for Poco Verde in 1995, and from 121 to 1,810 cm2for the entries Guymon and Common in 1996. African bermudagrass (Cynodon transvaalensis) exhibited the greatest number of live shoots per diseased area in both years, due in part to its greater shoot density, but also indicating greater potential to recover from the disease. African bermudagrass, Guymon, Sundevil, Midlawn, Midfield, Ft. Reno, Mirage, and several experimental seed-propagated entries were most resistant to spring dead spot, having the lowest diseased area and greatest number of live shoots within diseased areas. In Oklahoma, severity of spring dead spot among bermudagrass entries was correlated with feeeze injury that occurred during the first winter after planting.
Resistance inCapsicum pubescenstoXanthomonas campestrispv.vesicatoriaPepper Race 6
Authors: Sahin F. , Miller S. A.
Published: May 2007

One hundred seventy Capsicum spp. germplasm accessions were evaluated as potential sources of resistance to X. campestris pv. vesicatoria pepper race 6 (P6). This race has been identified recently in Ohio and overcomes all three known resistance genes in cultivated pepper. Only C. pubescens plant introduction (PI) 235047 was found to be resistant to X. campestris pv. vesicatoria P6 strains using hypersensitivity and pathogenicity tests. Further studies using PI 235047 as a differential line showed that strains classified as X. campestris pv. vesicatoria races P1 and P3 were heterogeneous in terms of virulence. Strains of X. campestris pv. vesicatoria P1 and P3 that were compatible with PI 235047 were reclassified as two new pepper races, designated X. campestris pv. vesicatoria P7 and P8, respectively. According to the new race classification, PI 235047 plants are incompatible with X. campestris pv. vesicatoria pepper races P0, P1, P3, P4, and P6, but compatible with races P2, P5, P7, and P8.
First Report of Ascochyta Blight of Cicer montbretii, a Wild Perennial Chickpea in Bulgaria
Authors: Kaiser W. J. , Hannan R. M. , Muehlbauer F. J. , Mihov M.
Published: May 2007

In the Stranja Mountains of southeastern Bulgaria, native populations of Cicer montbretii Jaub. & Spach were found on the edge of a road in an oak forest near the village of Gramatikova (42°1′38″N; 27°36′49″E) at an elevation of about 125 m. C. montbretii, a perennial species, is the only wild Cicer sp. native to Bulgaria. At the time of collection, necrotic lesions were observed on the stems, leaflets, and pods of several plants, and these lesions were reminiscent of those induced by Ascochyta rabiei (Pass.) Labrousse. The teleomorph (sexual stage) of A. rabiei, Didymella rabiei (Kovachevski) v. Arx (syn. Mycosphaerella rabiei Kovachevski), was discovered in 1936 on overwintered chickpea residue in southern Bulgaria. The fungus is heterothallic and requires the pairing of two compatible mating types for development of fertile pseudothecia. Both mating types of A. rabiei were isolated previously from naturally infected, cultivated chickpeas (C. arietinum L.) from northeastern and southern Bulgaria (1), and the teleomorph, Didymella rabiei (Kovachevski) v. Arx, developed on naturally infested chickpea debris from both regions when it was incubated at appropriate environmental conditions. Isolations were made from lesions on the leaflets, stems, pods, and seeds of C. montbretii by surface disinfecting tissue in 0.25% NaOCl for 5 min, drying on paper hand towels, and placing small pieces of tissue on 2% water agar and Difco potato dextrose agar. Plates were incubated at 22 to 24°C under fluorescent lights with a 12-h photoperiod. A. rabiei was isolated from all foliar tissues of the plant, including seeds. Koch's postulates were fulfilled by inoculating the foliage of chickpea PI 458870 and reisolating the fungus from lesions that developed on the leaflets and stems. Six Bulgarian isolates of A. rabiei from C. montbretii were paired with compatible mating type tester isolates of A. rabiei, MAT1-1 (ATCC 76501) and MAT 1-2 (ATCC 76502), following the procedure of Kaiser and Kusmenoglu (2). Both mating types were found among the six isolates. Two were MAT 1-1 and four MAT 1-2. The teleomorph did not develop on the small amount of naturally infested chickpea residue tested. Therefore, in Bulgaria, both cultivated and wild chickpeas are infected naturally by A. rabiei and both mating types have been isolated from these hosts. D. rabiei will likely be found in native stands of C. montbretii in Bulgaria as more samples of overwintered infested debris are examined for the teleomorph. This is the first report of A. rabiei causing blight of a wild Cicer sp.

References: (1) W. J. Kaiser. Can. J. Plant Pathol. 19:215, 1997. (2) W. J. Kaiser and I. Kusmenoglu. Plant Dis. 81:1284, 1997.
Occurrence of Bacterial Stem Rot, Caused by Erwinia chrysanthemi, on Field-Grown Tomato in Florida
Authors: Chellemi D. O. , Dankers H. A. , Hill K. , Cullen R. E. , Simone G. W. , Gooch M. D. , Allingham J. E.
Published: May 2007

In September 1997, wilted 4-week-old tomato (Lycopersicon esculentum Mill.) plants were observed in a commercial production field in St. Lucie County, FL. Closer inspection of affected plants revealed hollow stems and petioles with dark, water-soaked lesions. Diseased tissue was macerated and streaked onto nutrient agar (NA) and crystal violet pectate (CVP) agar. After incubation for 2 days at 30°C, isolates produced pits on the CVP agar. Isolates were transferred onto NA and the incubation and transfer procedure was performed two additional times to obtain pure cultures. Suspensions of bacterial cells were injected into tomato and tobacco leaves to test for a hypersensitive or pathogenic reaction. Isolates produced collapsed necrotic tissue on tomato while no reaction was observed on tobacco. Tests for differentiating species and subspecies in the ‘carotovora’ group of Erwinia were conducted following the protocol of Dickey and Kelman (1). With known cultures of E. carotovora subsp. carotovora and E. chrysanthemi as controls, the isolate from tomato was determined to function as a facultative anaerobe, utilize asparagine as a sole source of carbon and nitrogen, and give positive reactions for pectate degradation, phosphatase, and growth at 37°C. Known cultures of E. carotovora subsp. carotovora, E. chrysanthemi, and the tomato isolate were grown on trypticase soy broth agar for 24 h at 28°C and their cellular fatty acids derivatized to fatty acid methyl esters (FAMEs). Statistical analyses of FAME profile data (MIDI Microbial Identification System, Newark, DE, version 3.60) identified the tomato isolate as Erwinia chrysanthemi. Pathogenicity was determined by inoculating 50-day-old tomato plants (cv. SunPride) with a suspension of E. chrysanthemi obtained from nutrient broth plates incubated at 24°C for 60 h. Three plants each were inoculated with the E. chrysanthemi identified from tomato, sterile water, and known cultures of E. chrysanthemi and E. carotovora subsp. carotovora by placing a drop at the junction of the petiole and stem and passing a sterile needle through the drop into the stem. Plants were maintained in a greenhouse. Dark, water-soaked cankers were observed on the stems of plants inoculated with E. chrysanthemi, including the tomato isolate and E. carotovora subsp. carotovora, after 7 days. No symptoms were observed on plants inoculated with sterile water. Reisolation of the pathogen and identification was performed with tissue from one of the symptomatic inoculated plants. Analyses of FAMEs confirmed E. chrysanthemi as the causal agent. This is the first report of E. chrysanthemi causing a vascular disease of field-grown tomato in Florida.

Reference: (1) R. S. Dickey and A. Kelman. 1988. Pages 44–59 in: Laboratory Guide for Identification of Plant Pathogenic Bacteria. N. W. Schaad, ed. American Phytopathological Society, St. Paul, MN.
Powdery Mildew Caused by an Oidium sp. in Alfalfa in Wisconsin
Authors: Edmunds J. I. , Miller D. J. , Stuteville D. L.
Published: May 2007

In July 1996 and August 1997, dense amphigenous mycelia bearing Oidium conidia infected the lower stems and leaves of alfalfa (Medicago sativa L.) plants in research nurseries in south-central Wisconsin, causing the defoliation of the affected leaves. In the greenhouse, the disease spread rapidly from transplanted field plants to adjacent flats of alfalfa seedlings. A teleomorphic state of the fungus was not observed. Morphological characteristics of the oidia were similar to those of Erysiphe pisi (1). Conidia were ellipsoid-cylindrical and closely resembled those shown from Pisum sativum L. (2). Dry (2) conidia averaged 14.6 × 41.4 μm (range: 13.0 to 15.6 × 39 to 46.8 μm). Conidia shaken from mildewed alfalfa plants onto plants of garden pea (Pisum sativum) cv. Early Perfection and red clover (Trifolium pratense L.) cv. Lakeland infected both hosts. However, powdery mildew developed sooner and was much more severe in pea than in red clover. Noninoculated control plants remained free of powdery mildew. This is the first report of powdery mildew in alfalfa in Wisconsin fields. In extensive pathogenicity studies in greenhouses in Wisconsin (2), conidia from at least one isolate from red clover infected Medicago falcata L. and M. sativa L. var. glutinosa Urban, but not alfalfa cv. Vernal.

References: (1) H. J. Boesewinkel. Bot. Rev. 46:167, 1980. (2) J. R. Stavely and E. W. Hanson. Phytopathology 56:309, 1966.
First Report of White Mold (Sclerotinia sclerotiorum) on Soybean in Maine
Authors: Johnson S. B. , Kleinhenz M. D. , Dwyer J. D. , Griffin T. , Olanya O. M. , Lambert D. H. , Porter G. A.
Published: May 2007

White mold or Sclerotinia stem rot (Sclerotinia sclerotiorum (Lib) de-Bary) was first observed on soybean varieties in a variety trial at the Maine Agricultural and Forest Experiment Station, Presque Isle, and in commercial soybean fields in late July and August 1997. Symptoms and signs included stem bleaching, fluffy white mycelial growth on soybean stems and foliage, and presence of sclerotia typical of white mold. Disease assessment, based on symptoms, was conducted on the varieties in the trial in the experiment station. Field observations on disease occurrence were also conducted in commercial soybean fields in northern Maine. In the variety trial experiment, mean incidence (%) of white mold ranged from 0 to 6.8% on Lambert, APK007, P9092, P9132, and Stine varieties. No white mold was detected on P9071, P9007, Korada, Bravor, Ugo, APK020, and Aquillon varieties. Of the infected varieties, incidence of white mold was detected in 10 of 33 fields examined. This is the first report of the occurrence of white mold on soybean in Maine. Because of large-scale commercial potato production in the region, and previous occurrence of white mold on potato, it is likely that the pathogen is present in soils of various commercial potato fields in Maine. Precautions should, therefore, be taken in introducing resistant varieties and ensuring proper rotation and cropping sequences as soybean production increases in Maine.
A Partial Host Range of the High Plains Virus of Corn and Wheat
Authors: Seifers Dallas L. , Harvey Tom L. , Martin T. J. , Jensen Stanley G.
Published: May 2007

Barley (Hordeum vulgare), cheat (Bromus secalinus), corn (Zea mays), oat (Avena sativa), rye (Secale cereale), and wheat (Triticum aestivum) were infected by a Kansas isolate of the High Plains virus (HPV) in greenhouse experiments, but several other grass species were not. Infection of a host was dependent upon wheat curl mite numbers. Although both green foxtail (Setaria viridis) and yellow foxtail (S. glauca) are found naturally infected by HPV, only yellow foxtail could be infected in greenhouse experiments. Field sampling (1994 to 1996) of symptomatic yellow foxtail showed that it is a good indicator of the presence of HPV, with 252 of 278 symptomatic plants testing positive in enzyme-linked immunosorbent assay (ELISA) for HPV, 2 of 278 for American wheat striate mosaic virus, and 1 of 278 for johnson grass mosaic virus, whereas 23 of 278 symptomatic plants were negative for all viruses tested by ELISA and were not infectious in back-assays.
Analysis of Patterns of Pineapple Mealybug Wilt Disease in Sri Lanka
Authors: Hughes G. , Samita S.
Published: May 2007

Mealybug wilt disease of pineapple has a complicated etiology, which is not yet fully understood. As a result, assessments of the disease in the field, such as those that are made in the context of evaluation of disease control methods, are usually based on symptomatology. Field assessments, based on symptoms of mealybug wilt disease, were made in the Kurunegala and Gampaha districts of Sri Lanka. These data were fitted to statistical probability distributions as a method of summarizing the spatial pattern of disease incidence. Most plots showed aggregated patterns of diseased plants, but there were some exceptions. Summarizing patterns of disease incidence by means of fitting statistical probability distributions provides a basis for significance testing in cases where factors affecting disease incidence are the subject of field experimentation. Some examples of this methodology are given.
Isolation and Partial Characterization of a Filamentous Virus Associated with Peach Mosaic Disease
Authors: James D. , Howell W. E.
Published: May 2007

A filamentous virus, 752 nm long by 9.25 nm wide and with striations of 3.47 nm in pitch, was isolated from peach mosaic-affected peach. The peach mosaic-associated virus (PMV) has a coat protein subunit molecular mass of 20.5 kDa, and dsRNA bands of 7.0, 6.4, 4.2, and 1.9 × 106 Da, with a number of bands of lower molecular mass ranging in size from 1.3 to 0.3 × 106 Da. The herbaceous host range of PMV includes Chenopodium amaranticolor, C. quinoa, and Nicotiana occidentalis “37B.” The virus was successfully bud-transmitted from infected peach to peach indicator plants, cv. Elberta, which displayed typical peach mosaic symptoms. Attempts to transmit PMV to Prunus avium cv. Bing and P. mahaleb were unsuccessful. In serological assays, PMV polyclonal antibody (PAb) cross-reacted with cherry mottle leaf virus (CMLV). CMLV PAb and CMLV monoclonal antibodies cross-reacted with all isolates of PMV tested. Blocking with skim milk had no effect on the cross-reactions observed. PMV was consistently associated with peach mosaic disease, and the bud transmission studies and serological data suggest that this virus is the causal agent of peach mosaic disease. Data indicating that there is no relationship between peach latent mosaic viroid and peach mosaic disease was also obtained. PMV and CMLV appear to be closely related viruses, with identical coat protein subunit size and dsRNA profiles.
Distribution of Fumonisins in Maize Ears Infected with Strains of Fusarium moniliforme that Differ in Fumonisin Production
Authors: Desjardins Anne E. , Plattner Ronald D. , Lu Ming , Claflin Larry E.
Published: May 2007

Strains of Fusarium moniliforme (Gibberella fujikuroi mating population A) that differ in fu-monisin production in vitro were previously identified in a Kansas field population. One strain that produced high levels of fumonisins and two strains that produced very low levels of fu-monisins were applied to maize kernels at planting at the Rocky Ford Farm near Manhattan, Kansas. The distribution of fumonisins in symptomatic and symptomless kernels from individual harvested ears was determined by high performance liquid chromatography, and the distribution of the three applied strains in the kernels was determined by vegetative compatibility group analysis. Both symptomatic and symptomless kernels were extensively colonized with F. moniliforme, but the highest levels of fumonisins were in the symptomatic kernels. All three applied strains were recovered from kernels in 1993, and two of them were recovered from kernels in 1994. However, a high frequency of ear and kernel infection with a strain that produced little fumonisin in vitro did not consistently decrease the level of fumonisins. The frequency of infection with fumonisin low-producing strains may have been too low for competitive exclusion of naturally occurring fumonisin high-producing strains. Also, strains that are low-fumonisin producers under laboratory conditions may be high producers in the field.
Inoculation of Tomato Spotted Wilt Virus into Cotton
Authors: Groves R. L. , Kennedy G. G. , Walgenbach J. F. , Moyer J. W.
Published: May 2007

Tomato spotted wilt virus (TSWV) is an economically important virus of many crops throughout the world. Cotton, Gossypium hirsutum L., has previously been demonstrated to be susceptible to TSWV (1). During the fall of 1996, cotton was assayed as a potential host of TSWV, as it is an important early season host of thrips vectors of TSWV. Four commercial cotton varieties (DP 20, DP 52, DP 5409, and HS 46) were screened for susceptibility to four isolates of TSWV: two from tobacco, one from pineapple, and one from dahlia. Greenhouse-grown plants in the first true leaf stage were inoculated mechanically. Mean percent infection ranged from 20 to 33% (x = 27%) across all cotton varieties screened against all virus isolates 21 days post-inoculation. TSWV was recovered through mechanical inoculation from double antibody sandwich-enzyme-linked immunosorbent assay (DAS ELISA) positive cotton leaves in 83% of indicator plants, Emilia sonchifolia (L.) DC. ex Wight. Individual cotton plants testing TSWV ELISA positive were held for an additional 28 days with 4% of these again testing virus positive. The four cotton varieties were tested in the cotyledon, one-leaf, and four-leaf stages for susceptibility to tobacco thrips, Frankliniella fusca Hinds, transmission of one TSWV isolate from tobacco. First instar thrips were obtained from an avirulent colony. Mean percent infection among all varieties assayed was 10, 63, and 5%, respectively, for the three developmental stages. Cotton appears to be most susceptible in the one-leaf developmental stage with potential to serve as a source for TSWV spread to other crops.

Reference: (1) G. L. Schuster and R. S. Haliwell. Plant Dis. 78:100, 1994.
The Influence of Temperature and Leaf Wetness Duration on Infection of Perennial Ryegrass by Rhizoctonia solani
Authors: Gross M. K. , Santini J. B. , Tikhonova I. , Latin R.
Published: May 2007

Controlled environment experiments were conducted to determine the influence of temperature and leaf wetness duration on infection of perennial ryegrass by Rhizoctonia solani. Infection of grass plants raised in pots and exposed to mycelium of R. solani was evaluated at various combinations of temperature and leaf wetness duration. Temperatures included 15, 18, 21, 24, and 27°C. Leaf wetness periods were 9, 12, 15, 18, and 24 h. Disease was most severe (more than 50 leaves with brown patch lesions per pot) when plants were in contact with the inoculum source for 24 h of leaf wetness at 24°C. The least amount of disease (0 leaves with lesions per pot) occurred at 15°C and a 9-h wet period. The data were subjected to analysis of variance with orthogonal polynomial contrasts. Significant effects were included in a regression model that described the response of infection to temperature and wetness duration. The polynomial model included linear and quadratic terms for temperature and wetness duration. The adjusted coefficient of determination for the fitted model was 0.93, indicating an excellent fit to the data. The model is intended for use in an improved brown patch warning system for perennial ryegrass in the midwestern United States.