bluuebunny/crossref_metadata_2025 huggingface dataset:
Preliminary Identification of Maize Stripe Tenuivirus in Thailand
Authors: Sdoodee R. , Teakle D. S. , Louie R.
Published: May 2007

Maize stripe tenuivirus (MStV) and its planthopper vector, Peregrinus maidis, occur in many tropical and subtropical regions worldwide (2). However, MStV has not been reported from the southeastern Asia continent. In January 1990, five of 200 Sorghum bicolor plants growing in Hat Yai, Thailand, showed symptoms typical of MStV, i.e., chlorotic spots, streaks, and wide bands on the younger leaves. Colonies of P. maidis also were present in leaf whorls of both symptomatic and asymptomatic sorghum plants. In December 1991, two sweet corn plants (Zea mays cv. Thai Super Sweet Composite 1 DMR) growing in the same area showed similar symptoms and were infested with P. maidis. When examined by phase-contrast microscopy, sap from chlorotic leaf tissue of one sweet corn plant had needle-shaped crystals typical of MStV infection (1). Sap from asymptomatic sweet corn plants had no crystals. In April 1996. maize cv. Chieng Mai 90 with MSt-like symptoms and also infested by P. maidis was collected from Hat Yai. Leaves were freeze dried, sent to Ohio, and tested by F(ab′)2 enzyme-linked immunosorbent assay (ELISA). Positive control samples were fresh or freeze-dried leaves of sweet corn infected with MStV from Australia, Costa Rica, Malawi, Mauritius. and the U.S. Leaves of asymptomatic glasshouse-grown sweet corn seedlings were negative controls. In the ELISAs, the OD values at A 405 of the Thailand sample with MStV symptoms was 1.00, compared with 0.33 to 1.52 for the positive control samples and 0.00 to 0.02 for fresh or freeze-dried negative controls. The microscopic and serological results indicate the occurrence of MStV in Thailand.

References: (1) O. E. Bradfute and J. H. Tsai. Phytopathology 80:715, 1990. (2) R. E. Gingery et al. J. Gen. Virol. 64:1765, 1983.
First Report of a Leaf Spot Caused by Cladosporium oxysporum on Greenhouse Tomato
Authors: Lamboy J. S. , Dillard H. R.
Published: May 2007

In a commercial greenhouse in upstate New York, dark brown, angular lesions were first observed in April on lower, older leaves of 4-month-old tomato plants (Lycopersicon esculentum Mill. ‘Jumbo’). Chlorosis frequently developed around the lesions. Removal of the infected leaves reduced the rate of epidemic development. However, by July, lesions were present throughout the plant canopy, up to 2 m. The irregularly shaped lesions varied in size from 1 to 5 mm, frequently with tan-colored centers initially. Conidia developed in the center of the lesions, primarily on the outer, or adaxial side of the leaf, but were infrequent on the abax-ial surface. This contrasts with Cladosporium leaf mold caused by Fulvia fulva, in which the conidia develop as a velvety brown patch in lesions on the abaxial, or underside of the leaf, accompanied by chlorosis on the upper side of the leaf (1). The conidia ranged in shape from oval or li-moniform (5 to 6 μm in diameter) to cylindrical (5 to 6 μm wide, 7 to 20 μm long). The fungus was identified as Cladosporium oxysporum Berk. & M. A. Curtis (3) by C. J. K. Wang and J. M. McKemy of the State University of New York College of Environmental Science and Forestry in Syracuse, NY. Koch's postulates were fulfilled with a tuft of mycelium and conidia grown on potato dextrose agar as inoculum on fully expanded leaves of 5-week-old tomato plants, cv. Jumbo. Two weeks later, characteristic sporulating lesions developed on inoculated plants, about 1 cm from the inoculation site. Within 3 weeks, in the research greenhouse, the disease spread to healthy tomato plants in the vicinity, confirming the highly infectious nature observed in the commercial greenhouse. The fungus was reisolated from inoculated leaves and also from the adjacent naturally infected plants. C. oxysporum was previously reported as the causal agent of a leaf spot disease of pepper (2) and also a storage disease of ripe tomato fruit (4). To the best of our knowledge this is the first report of C. oxysporum causing disease on tomato foliage.

References: (1) E. E. Chamberlain. N.Z. J. Agric. 45:136, 1932. (2) A. M. Hammouda. Plant Dis. 76:536, 1992. (3) J. M. McKemy and G. Morgan-Jones. Mycotaxon 41:397, 1991. (4) S. Singh et al. Indian J. Microbiol. 23:133, 1983.
A New Report of Rhizomania and Other Furoviruses Infecting Sugar Beet in Minnesota
Authors: Wisler G. C. , Widner J. N. , Duffus J. E. , Liu H.-Y. , Sears J. L.
Published: May 2007

Several fields planted in sugar beet (Beta vulgaris) in the Southern Minnesota Beet Sugar Cooperative growing area showed patches of pale greenish yellow foliage and upright leaves characteristic of rhizomania. Other symptoms included reduced root size and root proliferation. Samples taken from these areas during August of 1996 were evaluated for beet necrotic yellow vein virus (BNYVV), the cause of rhizomania, and for other sugar beet furoviruses. BNYVV was identified in 59 of 90 beet samples tested with enzyme-linked immunosorbent assay and Western blot (immunoblot) analyses (molecular mass approximately 22 kDa) with specific (polyclonal antisera donated by K. Richards; monoclonal antisera donated by G. Grassi) and broadly reactive antisera produced at the USDA in Salinas, CA. Recovery by mechanical inoculation of Chenopodium quinoa and Beta macrocarpa confirmed identity. Beet leaves showing symptoms of vein clearing, vein banding, mosaic, and vein necrosis were all identified as being infected with beet soilborne mosaic virus (BSBMV). No systemic leaf symptoms of BNYVV were found in any sample. The BSBMV isolates were identical to one another based on symptomatology of indicator plants and molecular masses in Western blots (approximately 24 kDa), but symptoms were distinct from those of other members of the BSBMV serogroup isolates previously studied from Texas, Idaho, Nebraska, and Colorado. The beet soilborne virus (BSBV) was also recovered by mechanical inoculation and Western blot analysis (antisera donated by R. Koenig) in three samples of field-collected beets. This is a new report of BNYVV, BSBMV, and BSBV in Minnesota. The distribution of rhizomania in infested fields was not isolated to any general area, which indicates that the virus has been present and multiplying in previous sugar beet crops and was not detected. Severity of infection ranged from mild root symptoms with near normal yields and sugar content, to moderate and severe root symptoms with low yields and low sugar content.
First Report of Powdery Mildew Caused by Erysiphe heraclei on Celery in North America
Authors: Koike S. T. , Saenz G. S.
Published: May 2007

Since 1994, a fungal disease has been affecting celery (Apium graveolens) grown for seed in the central coast region of California. White, ectophytic mycelia and conidia, characteristic of a powdery mildew, were present on compound umbels, including the involucre, rays, raylets, flowers, and fruits. Celery with powdery mildew had twisted flower petals, and the disease possibly contributed to premature senescence and drying of the fruits. Powdery mildew was not observed on leaves. Mycelial growth was effused and amphigenous and had lobed appressoria. Conidiophores were straight, and cylindrical foot cells were followed by a longer cell and one or two shorter cells. Conidia were produced singly and were 36 to 44 × 11 to 16 μm. Fibrosin bodies were not observed. Germ tubes were located at the ends of conidia and formed lobed appressoria. Cleistothecia were not present. Based on these characteristics, the fungus was identified as Erysiphe heraclei (1). In California, parsley (Petroselinum crispum) is a host of E. heraclei (4), and parsley is grown in the same region as celery seed crops. To determine if parsley was an alternative host of the celery powdery mildew, infected celery umbels were gently pressed onto adaxial surfaces of leaves on 2-month-old greenhouse grown parsley cvs. Italian Plain and Triple Curled. Inoculated plants were incubated 48 h in a moist chamber at 22°C, then transferrred to a greenhouse at 22 ± 2°C / 16 ± 2°C day/night temperatures, 75% relative humidity, and natural light. After 12 to 14 days, powdery mildew was observed on both parsley cultivars. Uninoculated control plants did not develop the disease. This is the first report of powdery mildew on celery in North America. Previous reports list E. heraclei on celery in Chile, the former Czechoslovakia, France, Iraq, Italy, and the former USSR (Georgia region). In the U.S., E. heraclei is reported on carrot (Daucus carota) (2), parsley (4), meadow parsnip (Zizia aptera and Z. aurea) (3), and now celery.

References: (1) H. J. Boesewinkel. Bot. Rev. 46:167, 1980. (2) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN. (3) K. A. Hirata. Host Range and Geographic Distribution of the Powdery Mildew Fungi. Jpn. Scientif. Soc. Press, Tokyo. (4) S. T. Koike and G. S. Saenz. Plant Dis. 78:1219, 1994.
First Report of Marssonina brunnea f. sp. brunnea on Hybrid Poplar in the Pacific Northwest
Authors: Newcombe G. , Callan B. E.
Published: May 2007

Marssonina brunnea (Ellis and Everh.) Magnus f. sp. brunnea Spiers is the most damaging Marssonina sp. affecting Populus spp. in the world (1). First described from eastern North America at the turn of the century, it subsequently became a serious disease of hybrid poplar in Europe in the 1960s and in New Zealand in 1976 (1). It causes punctiform black spots on both leaf surfaces and lesions on petioles and young stems. Symptoms are typically most severe in the lower portion of the crown of trees. Not observed in the Pacific Northwest on hybrid poplar until recently, it is still only present in a few locations. Voucher specimens from near Ilwaco, WA, at the mouth of the Columbia River, and from near Har-rison Mills, British Columbia, were deposited in the Herbarium at the Pacific Forestry Centre (DAVFP 25202 and 24958, respectively). The fungus was identified as M. brunnea by its conidial morphology. Conidia were hyaline, uniseptate, mostly straight, and narrowly obovoid, and, when measured in lactoglycerol, averaged 16.1 μm × 5.0 μm (WA collection) and 15.7 μm × 5.6 μm (BC collection). The septum is located about 30% of the total conidium length from the conidium base. Inoculations of leaf disks (1) proved that the species was pathogenic to hybrids but not to local P. tremuloides Michx., and thus the fungus was identified as M. brunnea f. sp. brunnea. Variation in resistance, from light spotting to severe, was noted both among 12 P. trichocarpa Torr. & A. Gray × P. deltoides J. Bartram ex. Marsh. hybrid clones in the Ilwaco plantation and among 56 hybrid clones in the inoculation study.

Reference: (1) A. G. Spiers. Eur. J. For. Pathol. 18:140, 1988.
Characterization and Pathogenicity of Thanatephorus cucumeris from Sugar Beet in Minnesota
Authors: Windels Carol E. , Kuznia Rita A. , Call Jack
Published: May 2007

In 1993, hymenia of Thanatephorus cucumeris occurred on petioles of sugar beet leaves, but disease was not observed on leaves, crowns, or roots. Of 33 cultures isolated from sugar beet, 28 were identified as Rhizoctonia solani AG-3 (from four fields planted to potatoes in 1992) and five isolates were AG-5 (from one field planted to wheat in 1992). These isolates of R. solani AG-3 and AG-5 were nonpathogenic to moderately pathogenic on sugar beet seedlings (stands ranged from 49 to 95%). The same isolates were nonpathogenic when inoculated on 8-week-old sugar beet roots (root rot indices were ≤1 [0 to 7 scale]). All isolates of R. solani AG-3 (but none of AG-5) formed sclerotia on roots. Disease indices (0 to 4 scale) on potato sprouts at 10°C were low, did not differ significantly (P = 0.05) among isolates and the control in either of two experiments, and averaged 0.9 for 14 isolates of AG-3, 0.5 for three isolates of AG-5, and 0.5 in the control. All isolates of AG-3 (but none of AG-5) formed sclerotia on potato seed pieces. When potato sprouts were grown at 25°C, disease indices were low (averaged 0.4 in each of two experiments), but four isolates of AG-3 and three of AG-5 had disease indices significantly (P = 0.05) higher than those of the uninoculated control. Sclerotia were not observed. The presence of hymenia of T. cucumeris is significant in that sexual reproduction and inoculum production occurred on a nonhost crop and were related to AGs of R. solani associated with the previous crop (AG-3 for potato and AG-5 for wheat).
Development of Serological Procedures for Rapid and Reliable Detection of Wheat Streak Mosaic Virus in a Single Wheat Curl Mite
Authors: Mahmood T. , Hein G. L. , French R. C.
Published: May 2007

Wheat streak mosaic virus (WSMV) is transmitted by the wheat curl mite (WCM), Aceria tosichella. Immunofluorescent and dot-immunobinding assays were developed to detect the presence of WSMV in single WCM. Virus-specific immunofluorescent microscopy detected WSMV near the anterior end of viruliferous WCM. With dot-immunobinding assay, WSMV was detected in WCM fed on WSMV-infected wheat (Triticum aestivum) but not in WCM maintained on healthy plants. Both immunofluorescent and dot-immunobinding assays were sufficiently sensitive to detect WSMV in individual WCM, providing a means to determine the percentage of viruliferous WCM in field collections.
Virulence in Puccinia recondita f. sp. tritici Isolates from Canada to Genes for Adult-Plant Resistance to Wheat Leaf Rust
Authors: Kolmer J. A.
Published: May 2007

Sixty-seven isolates of Puccinia recondita f. sp. tritici collected in Canada were tested for virulence to adult plants of Thatcher near-isogenic wheat lines with leaf rust resistance genes Lr13, Lr22a, Lr34, Lr35, and Lr13 and Lr34 combined. All of the isolates had low infection type to the Thatcher lines with Lr22a and Lr35. All isolates had lower infection type and lower rust severity on the Thatcher line with Lr34 compared with Thatcher. The isolates were polymorphic for virulence to the Thatcher line with Lr13; many isolates were completely virulent to this line, and other isolates produced very low or intermediate avirulent infection type. On the Thatcher line with Lr13 and Lr34 combined, many isolates had infection type and rust severity similar to the Thatcher line with Lr34, while other isolates had lower infection type and rust severity compared with the single-gene lines with Lr13 or Lr34. Fifteen isolates with low, intermediate, and high infection type to adult plants with Lr13 were tested for infection type on seedling plants of the Thatcher lines with resistance genes Lr13, Lr22a, Lr34, Lr35, and Lr37, and on Thatcher lines with Lr13 paired with seedling resistance genes. Most isolates were completely virulent to seedling plants with Lr13 and Lr22a. Plants with Lr37 expressed seedling resistance to all isolates tested. Seedling plants with Lr34 had lower infection types to all isolates compared with Thatcher. Seedlings with Lr35 had high infection types to most isolates, with varying amounts of chlorosis. The Thatcher lines with Lr13 plus seedling resistance genes were most resistant to the isolates that had very low infection types on adult plants with Lr13 and intermediate infection types on plants with seedling resistance genes. Genes Lr22a, Lr35, and Lr37 offer additional sources of highly effective leaf rust resistance in wheat.
Inhibition of Aphanomyces euteiches f. sp. pisi by Volatiles Produced by Hydrolysis of Brassica napus Seed Meal
Authors: Smolinska Urszula , Knudsen G. R. , Morra M. J. , Borek V.
Published: May 2007

Seed meal from Brassica napus (rapeseed) produced volatile fungitoxic compounds potentially of value in the control of Aphanomyces root rot of pea. Hyphal growth, germination of encysted zoospores, and oospore survival and inoculum potential, were determined in the presence of volatiles produced from B. napus seed meal. Volatile compounds from B. napus meal completely suppressed mycelial growth and germination of encysted zoospores on agar. In growth chamber bioassays, pea (Pisum sativum) seed inoculated with zoospore suspensions and incubated 24 h in the presence of volatiles from rapeseed meal had 50% lower root rot disease severity than in the absence of meal. Volatile compounds passing through soil also significantly decreased survival and inoculum potential of oospores. Gas chromatographic analysis of rapeseed tissues and the volatile compounds evolved from tissues showed that substrate glucosinolates were hydrolyzed enzymatically to produce mainly isothiocyanates. Non-autoclaved rapeseed meal produced significantly higher levels of volatile compounds than did autoclaved meal. Also, volatile compounds produced from autoclaved meal were dominated by nitriles, whereas isothiocyanates were more common volatile products from non-autoclaved meal. Our results indicate that B. napus allelochemicals responsible for toxic effects toward A. euteiches f. sp. pisi are enzymatic hydrolysis products of glucosinolates.
Comparative Morphology and Pathology of Calonectria theae and C. colhounii in Hawaii
Authors: Uchida J. Y. , Aragaki M.
Published: May 2007

Calonectria theae is distinguished from C. colhounii by perithecial color, number of ascospores in an ascus, longer stipes, longer conidia, and the formation of a second conidial type that is extraordinarily long, angular, and borne on simple, submerged, dichotomously branching conidiophores. Both species were isolated from ohia (Metrosideros collinus), M. excelsus, and sentry palm (Howea forsteriana). C. theae was also isolated from leather leaf fern (Rumohra adiantiformis) and Strelitzia, while C. colhounii isolates were obtained from Eucalyptus, Leucospermum, and Chrysalidocarpus lutescens. All tested isolates of both Calonectria spp. were pathogenic to ohia, an important native tree species in Hawaiian forests. Both species killed apical shoots, and caused leaf spotting, blighting, and subsequent defoliation. Symptomatically, the diseases caused by these species are indistinguishable on ohia. This disease poses a potential threat to native forests.
Influence of Cryphonectria parasitica Basal Cankers on Radial Growth of Scarlet Oak in Pennsylvania
Authors: Davis D. D. , Torsello Mary L. , McClenahen James R.
Published: May 2007

Basal cankers induced by Cryphonectria parasitica (=Endothia parasitica) occur throughout the natural range of scarlet oak (Quercus coccinea) within Pennsylvania. Because colonization of scarlet oak is thought to be a long-term host/pathogen relationship, analyses were conducted to investigate effects of basal cankers on radial growth (expressed as area increment) at 1.4 m, breast height (BH). Moderately cankered oaks grew more slowly at BH than did noncankered trees. However, severely cankered scarlet oaks generally exhibited greater radial growth at BH than did noncankered trees. This apparent anomaly likely reflects stimulated growth at BH due to the fungal infection.
Analysis of Resistance to Eastern Filbert Blight in Corylus avellana
Authors: Osterbauer N. K. , Johnson K. B. , Mehlenbacher S. A. , Sawyer T. L.
Published: May 2007

Inheritance of resistance to eastern filbert blight, caused by Anisogramma anomala, in European hazelnut (Corylus avellana) was evaluated in the progeny of seven cultivars crossed in 12 combinations. The progeny were subjected to inoculation with A. anomala in the greenhouse and in the field. Three disease responses were measured: disease incidence, number of cankers, and proportion of wood diseased. In both the greenhouse and the field, progeny produced by crossing VR6-28 with three susceptible cultivars segregated 1:1 for complete resistance to eastern filbert blight, confirming a previous report that VR6-28 is heterozygous for a single, dominant resistance gene. Histograms of disease responses in progeny of the remaining six parents showed continuous distributions for all crosses examined. Consequently, these parents were analyzed for general and specific combining abilities for each disease response. In the field, general and specific combining ability were both significant (P < 0.05) for all disease responses, with general combining ability having twice the magnitude of specific combining ability. These results suggest these disease responses are controlled by additive gene action in the cultivars examined, with nonadditive gene action being of some importance. Based on general combining ability values, high levels of partial resistance were transmitted by the pollen parents, Gem and Tonda di Giffoni, and the seed parent, Willamette. Heritability of disease incidence, number of cankers, and proportion of wood diseased were calculated to be 0.21, 0.39, and 0.47, respectively, for this set of nine crosses after the first exposure period in the field. This suggests that it will be possible to use partially resistant parents to breed for hazelnuts exhibiting fewer and smaller cankers.
Comparisons of Tolerance of Ash Yellows Phytoplasmas inFraxinusSpecies and Rootstock-Scion Combinations
Authors: Sinclair W. A. , Griffiths H. M. , Whitlow T. H.
Published: May 2007

Growth responses of different ash (Fraxinus) species and rootstock-scion combinations to ash yellows (AshY) phytoplasmas were compared in greenhouse experiments by expressing each measurement as a proportion of the final average value of the variable in noninoculated, own-rooted control trees. Phytoplasmal infection suppressed shoot growth of white ash (F. americana) and green ash (F. pennsylvanica) beginning when buds opened, but did not suppress velvet ash (F. velutina) until after 60 days of growth. AshY-associated growth losses in height, stem diameter, and root volume, averaged across two experiments, were 80, 93, and 98%, respectively, in white ash; 60, 57, and 79% in green ash; and 23, 0, and 12% in velvet ash. Growth in height, but not in stem diameter or root volume, of diseased white ash on velvet ash rootstock was significantly greater than growth of diseased own-rooted white ash. White ash witches'-brooms grafted onto healthy velvet ash continued to grow but did not produce vigorous, dominant shoots. Growth of diseased velvet ash on white ash roots was severely suppressed in comparison with that of diseased own-rooted velvet ash. Management of AshY through the use of tolerant genotypes may require tolerance in both scions and rootstocks.
A Description of Silk Cut, a Stress-Related Loss of Kernel Integrity in Preharvest Maize
Authors: Odvody G. N. , Spencer N. , Remmers J.
Published: May 2007

Silk cut is an important recurring problem of many commercial maize (Zea mays) hybrids exposed to late-season drought stress in southern Texas. Silk cut is the preharvest occurrence of one or more lateral splits in the kernel pericarp that expose the kernel tissues and embryo to either pre- or postharvest attack by fungi and insects. It can occur as multiple lateral splits anywhere on the seed surface but its primary and most common occurrence is as a single, lateral split at the kernel edge on either side or both sides of the embryo. Individual splits range from nearly microscopic to those that almost encircle the seed. Silk cut can be initiated at kernel moistures as high as 50% but is more commonly initiated and observed at kernel moistures of 28% and lower. In yearly observations from 1986 to 1994, silk cut was highest in incidence and severity on normal-yield-potential maize crops exposed to rapidly increasing environmental stress (decreasing soil moisture and high soil and air temperatures) during the latter stages of maturity but especially after black-layer formation. Hybrids with open ear tips and loose husks were among those most vulnerable to silk cut but incidence and severity varied widely across years, sites, and stress environments. Incidence also varied widely between adjacent plants. Total silk cut (kernels with silk cut colonized by fungi and noncolonized) on 105 and 110 ears from consecutive plants of two vulnerable hybrids averaged 23 and 31% but ranged from 0 to 94 and 0 to 97%, respectively. Average difference in silk cut incidence between ears of adjacent plants of these hybrids was 28 and 29% and individual differences ranged from 0 to 93 and <1 to 97%, respectively. Kernels on the top one-third of the ear had a higher average incidence of silk cut (44%) than those in the middle (38%) or bottom (shank end) (31%) positions.
Field Sprays of Bacillus subtilis and Fungicides for Control of Preharvest Fruit Diseases of Avocado in South Africa
Authors: Korsten L. , De Villiers E. E. , Wehner F. C. , Kotzé J. M.
Published: May 2007

In 3 consecutive years, preharvest applications of Bacillus subtilis field sprays integrated with copper oxychloride or benomyl consistently reduced severity of avocado black spot (BS), caused by Pseudocercospora purpurea at Omega, Republic of South Africa. Control was equal to that obtained with copper oxychloride or benomyl-copper oxychloride in the first and third years of spraying at Omega. In the second year, only the integrated treatment controlled BS, while copper oxychloride proved ineffective. The antagonist was applied on its own or integrated with copper oxychloride sprays at two other geographically distinct locations, Westfalia Estate and Waterval. The integrated and biological treatments at these localities were less effective than copper oxychloride sprays in controlling BS disease. Integrated control was more effective than B. subtilis sprays at Westfalia. On continuation of the biological spray program at Waterval for an additional three seasons, control was as effective as copper oxychloride in the last 2 years of spraying. Sooty blotch (SB), caused by an Akaropeltopsis sp., was reduced by the integrated treatment at Omega during the second season and at Westfalia during the first season. Although the two fungicide treatments reduced SB at Omega in the first season, copper oxychloride increased it above that of the control in the third season. Only the copper oxychloride treatment reduced SB at Waterval in the third season, while the B. subtilis treatment increased disease above that of the control in the fourth season.
Reactions of Sweet Corn Hybrids with Resistance to Maize Dwarf Mosaic
Authors: Kerns M. R. , Pataky J. K.
Published: May 2007

Maize dwarf mosaic (MDM), caused by the sugarcane mosaic subgroup of potyviruses, can substantially reduce yield and ear quality of sweet corn (Zea mays). The effects of strain A of maize dwarf mosaic virus (MDMV-A) and strain MDMV-B of sugarcane mosaic virus (SCMV-MB) on resistant sweet corn hybrids were evaluated. Incidence of symptomatic plants, types of symptomatic responses, yield, and ear quality were compared among 20 hybrids in 1993 and 14 hybrids in 1994. Incidence of symptomatic plants measured at the beginning of harvest ranged from 4 to 100% in 1993 and 1 to 100% in 1994 and differed among hybrids inoculated with MDMV-A and/or SCMV-MB. Hybrids BiGuard, Dallas, HMX 9352, and Topacio had low (<20%) incidences of symptomatic plants when inoculated with MDMV-A, SCMV-B, or MDMV-A/SCMV-MB. Some hybrids had moderate responses, with incidence varying around 25%. Some hybrids appeared to have greater resistance to MDMV-A than to SCMV-MB. The incidence of sectoring plants (i.e., distinct bands or sectors of asymptomatic and symptomatic tissue) was higher for hybrids with high levels of resistance and ranged from 0 to 14% in 1993 and 0 to 83% in 1994. Ear weight of inoculated hybrids, expressed as a percentage of the non-inoculated control, ranged from 84 to 109% in 1993 and from 84 to 105% in 1994. Slope coefficients from regressions of percent ear weight on incidence ranged from -0.085 to -0.15. Butt blanking was associated with high incidence of MDM-symptomatic plants. None of the commercially available MDM-resistant sweet corn hybrids were 100% asymptomatic, but levels of resistance in most of these hybrids were adequate to minimize the effects of MDM on yield.
Effect of Soil Saturation Duration and Soil Water Content on Root Rot of Maize Caused by Pythium arrhenomanes
Authors: Yanar Y. , Lipps P. E. , Deep I. W.
Published: May 2007

Three aggressive isolates of P. arrhenomanes (201-25, 7E, and 5E) were used to evaluate the effect of soil saturation duration and soil water content on maize root rot. Maize seedlings grown in infested and noninfested soil:sand mixtures were subjected to saturation durations of 0, 6, 12, 24, or 40 h. Four silty-clay loam soil:sand mixtures (100:0, 80:20, 50:50, and 0:100) were used to evaluate the effect of soil water content on disease development. Matric water potential was maintained at -1 J/kg during the experiment except for the saturation period. Multiple regression analysis was used to evaluate the effect of saturation duration and soil water content on root and shoot dry weight. Negative slope values were obtained for increasing saturation duration and reduced water content (increased proportion of sand to soil). Intercepts of regression lines for shoot and root dry weights were lower for the infested soil:sand treatments than the noninfested treatments. These results indicated that growth of maize plants was negatively affected by increased flooding duration, lower soil water content, and presence of the pathogen. Growth of maize was significantly (P = 0.05) less in the presence of the pathogen than in non-inoculated control treatments at each soil water content and flooding duration.
Effects of Barley Yellow Dwarf Virus on Root and Shoot Growth of Winter Wheat Seedlings Grown in Aeroponic Culture
Authors: Hoffman T. K. , Kolb F. L.
Published: May 2007

Seedlings of eight soft red winter wheat (Triticum aestivum) cultivars were grown in an aeroponic mist box to study the effects of barley yellow dwarf virus (BYDV) on root and shoot growth and to look for differences in root and shoot growth among cultivars. The cultivars selected for the study were Caldwell, Cardinal, Clark, Howell, IL 87-2834, Tyler, and Pioneer brands 2548 and 2555. A split-plot treatment design was used, with uninfected and inoculated treatments as whole plots and cultivars as subplots. Differences among cultivars were found for most growth characteristics under both control and BYDV-infected conditions. There was a strong positive correlation between shoot and root dry weights in both the control and BYDV treatments, indicating that cultivars with vigorous shoot growth tended to have more vigorous root growth. BYDV severely reduced root length, distance from seminal root tip to the nearest lateral root, and the root to shoot ratio for all cultivars tested. The number of adventitious roots and shoot percent dry matter were increased by BYDV infection for some cultivars. Chlorosis and stunting were not observed in shoots during the 18 days of the experiment, whereas roots were visibly stunted approximately 4 days after inoculation. Results indicate that, initially, the root system is affected more severely than the shoot in BYDV-infected wheat seedlings.
Characterization of a Vascular Wilt of Erythroxylum coca Caused by Fusarium oxysporum f. sp. erythroxyli Forma Specialis Nova
Authors: Sands D. C. , Ford E. J. , Miller R. V. , Sally B. K. , McCarthy M. K. , Anderson T. W. , Weaver M. B. , Morgan C. T. , Pilgeram A. L. , Darlington L. C.
Published: May 2007

A new forma specialis of Fusarium oxysporum (F. oxysporum f. sp. erythroxyli) pathogenic to Erythroxylum coca and E. novogranatense is described. The pathogen was isolated from the vascular tissue of diseased plants from an Erythroxylum plantation in Hawaii. This pathogen causes vascular wilt symptoms and death in both E. coca and E. novogranatense plants as soon as 7 weeks after soil infestation. The pathogenicity of seven isolates from the affected field was determined in field and growth-chamber studies. Genetic variation was not detected among the seven Hawaiian isolates, using arbitrarily primed polymerase chain reaction. The seven isolates could be differentiated from a strain isolated from a diseased E. coca plant from South America. All Hawaiian isolates and the South American isolate belonged to a single vegetative compatibility group.
Germplasm Evaluation of Glycine max for Resistance to Fusarium solani, the Causal Organism of Sudden Death Syndrome
Authors: Hartman G. L. , Huang Y. H. , Nelson R. L. , Noel G. R.
Published: May 2007

Sudden death syndrome (SDS) is an important soybean disease that potentially can be controlled by host plant resistance. In this study, over 800 soybean plant introductions (PIs), lines, and cultivars were screened for resistance to Fusarium solani. Of 728 PIs from China, PI 567.374 had mean foliar SDS severities significantly (P = 0.05) lower than PI 520.733 (resistant check) in both growth-chamber and greenhouse tests. In addition, PIs 567.315, 567.441C, 567.650B, and 567.664 had mean SDS severity ratings significantly (P = 0.05) lower than PI 520.733 in a growth-chamber test. Of 16 soybean cyst nematode-resistant entries tested, 5 had values lower than the resistant check, PI 520.733, with cv. Hartwig significantly lower in the first trial. In trial two, no entries were lower than the resistant check, although cvs. Bell and Hartwig were not significantly different from PI 520.733. In another experiment, few soybean cultivars or experimental lines had SDS severity ratings lower than PI 520.733 in any one of three trials. Some of the newly acquired PIs from China that exhibited low foliar SDS severity ratings may provide the sources of resistance needed to develop new SDS-resistant soybean breeding lines and cultivars.
Broccoli Raab as a Host of Alternaria brassicae in California
Authors: Koike S. T.
Published: May 2007

In the fall of 1996, commercial plantings of broccoli raab or rappini (Brassica rapa subsp. rapa) in the Salinas Valley, Monterey County, were damaged by a disease previously unreported in California. Symptoms consisted of small (7 to 8 mm in diameter), circular to oblong, brown to light tan leaf spots that contained characteristic concentric rings. An Alternaria sp. having conidia with prominent beaks and spores produced singly or in chains of two was consistently observed on and isolated from the host. Conidia from naturally infected broccoli raab measured 144.5 to 194.5 × 22.2 to 30.6 μm (beak length ranged from 33.3 to 75.0 μm). The isolates were identified as Alternaria brassicae (Berk.) Sacc. (2). Pathogenicity was confirmed by culturing five representative isolates on sterilized 20% V8 juice solution for 10 days under a 12-h light/12-h dark cycle, filtering the suspensions through cheesecloth, obtaining spore concentrations of 30,000 conidia per ml, and spraying suspensions onto 6-week-old seedlings of broccoli raab cv. Spring Raab. Plants were incubated in a humid chamber for 48 h and then maintained in a greenhouse. After 5 to 7 days, leaf spots similar to the original symptoms developed on all inoculated plants. The pathogen was reisolated and identified as A. brassicae. Control plants sprayed with distilled water remained symptomless. The inoculation test was repeated and results were the same. Because of the extensive plantings of cole crops in the Salinas Valley, isolates from broccoli raab were inoculated onto two sets each of broccoli (Brassica oleracea subsp. italica cv. Greenbelt), Chinese cabbage (Brassica campestris subsp. pekinensis cv. Cha-Cha), and Japanese mustard (Brassica campestris subsp. nipposinica cv. Mizuna), using the method described above. After 5 to 7 days, similar leaf spots developed on all inoculated plants and A. brassicae was reisolated and identified. Control plants sprayed with distilled water remained symptomless. This fungus does not appear to be a pathogen specific to particular cole crops in this area (1). For California, this is the first report of black spot caused by A. brassicae on commercially grown broccoli raab.

References: (1) S. T. Koike. Plant Dis. 80:822, 1996. (2) E. G. Simmons. Mycotaxon 55:55, 1995.
First Report of Banana Streak Virus Infecting Sugarcane and Arrowroot in Colombia
Authors: Reichel H. , Belalcázar S. , Múnera G. , Arévalo E. , Narváez J.
Published: May 2007

We have recently reported on the presence of banana streak virus (BSV) affecting plantains (Musa spp.) in Colombia (2). BSV is serologically related to sugarcane bacilliform virus and has been found to be transmitted by the pink mealybug (Saccharicoccus sacchari) from sugarcane to banana (1). In the vicinity of affected plantain crops in the localities of Andes (Antioquia) and Montenegro (Quindio), we observed sugarcane (Saccharum officinarum L.) plants with chlorotic streaks on their leaves, as well as arrowroot (Canna edulis Ker-Gawl.) plants with mild mosaic symptoms. The foliar tissue of symptomatic plants of these two species was tested for BSV and cucumber mosaic virus (CMV) by double antibody sandwich-enzyme-linked immunosorbent assay with commercial polyclonal antisera (Agdia Inc., Elkhart, IN). BSV was detected in samples of both plant species, whereas CMV was not detected in either one. Immunosorbent electron microscopy analysis of BSV-infected, symptomatic, foliar tissue of sugarcane showed the presence of viral-like bacilliform particles measuring approximately 150 × 30 nm, typical of BSV. This is the first report of BSV infecting Saccharum officinarum in Colombia and the first report of Canna edulis as a host for this virus.

References: (1) B. E. L. Lockhart and L. J. C. Autrey. Plant Dis. 72:230, 1988. (2) H. Reichel et al. Plant Dis. 80:463, 1996.
Sporulation ofFusarium solanif. sp.glycines, Causal Agent of Sudden Death Syndrome, on Soybeans in the Midwestern and Southern United States
Authors: Roy K. W.
Published: May 2007

Production of macroconidia by the causal agent of sudden death syndrome, Fusarium solani f. sp. glycines, occurred on lower stems and roots of soybean plants symptomatic for the disease in Illinois, Indiana, Kentucky, Mississippi, and Tennessee. Most of the sporulation was light to dark blue to blue-green in color. Microscopically (15×) visible sporulation occurred on plants in 26, and macroscopically visible sporulation occurred on plants in 15, of 32 fields inspected. In some fields, the incidence of plants with microscopically visible sporulation was as high as 70%, and the incidence of plants with macroscopically visible sporulation reached 50%. Sporulation varied from pinpoint microscopic areas to macroscopically visible masses 4 to 6 cm2or larger. Areas of microscopically visible sporulation occurred on lower stems and roots within 2.5 cm above and below the soil line on about 50% of the plants, and areas of macroscopically visible sporulation occurred within the same region on about 60% of the plants. Both microscopic and macroscopic sporulation also occurred on taproots as far as 10 cm or more below the soil line. Severe foliar symptoms and root decay were associated with a greater incidence of plants with sporulation. The occurrence of sporulation should help distinguish sudden death syndrome from other diseases of like foliar symptomatology and help confirm its diagnosis. It is presumed from the results that sporulation eventually contributes to the inoculum density of F. solani f. sp. glycines in soybean fields.
Sources of Inoculum and Management for Rhizoctonia solani Damping-off on Tobacco Transplants under Greenhouse Conditions
Authors: Gutierrez W. A. , Shew H. D. , Melton T. A.
Published: May 2007

Damping-off and target spot are important diseases of tobacco transplants produced under greenhouse conditions. Identification of sources of inoculum for these diseases caused by Rhizoctonia solani is an important first step in disease management. Control strategies based on sanitation and the eradication of primary inoculum were studied. Potting mix and Styrofoam trays used in transplant production were assayed to determine if they were sources of primary inoculum. Eleven sources of potting mix were sampled over a 2-year period. None of the mixes contained viable inoculum of R. solani. R. solani was isolated from previously used trays after 1 year of storage by removing and plating pieces of Styrofoam from individual tray cells on alkaline water agar (AWA). Sclerotia and melanized hyphae of R. solani were observed in the cracks present in the cells of the trays. Dry heat (70 to 80°C for 2 h) and chemical (sodium hypochlorite and sodium chloride) treatments reduced the levels of inoculum on trays up to 45% compared to controls, but only methyl bromide and steam treatments (80°C for 0.5 to 2.0 h) eradicated inoculum of R. solani from trays. Elimination of primary inoculum from previously used trays effectively controlled target spot and stem rot diseases caused by R. solani.
Reaction of Soybean Cultivars to Isolates of Fusarium solani from the Red River Valley
Authors: Nelson Berlin D. , Hansen Jana M. , Windels Carol E. , Helms Ted C.
Published: May 2007

Five isolates of Fusarium solani, originally isolated from diseased soybean roots in the Red River Valley (RRV) of Minnesota and North Dakota, were evaluated for their ability to cause symptoms on 10 genetically diverse soybean cultivars. Taproots of 2-week-old plants were inoculated with F. solani-infested oat kernels, and 3 and 10 weeks later, plants were evaluated for root rot and foliar symptoms. At 3 weeks after inoculation, taproots of all cultivars had extensive reddish brown to black lesions; root rot severity (1–6 scale) ranged from 4.8 to 5.1, and 3.5% of the plants had died. Foliar symptoms were not observed. At 10 weeks after inoculation, all cultivars showed extensive decay of taproots and >50% of lateral roots were necrotic; root rot severity (1–4 scale) ranged from 2.7 to 3.7, and 42.5% of the plants had died. Foliar symptoms were first observed between the R-1 to R-6 growth stages (about 5 weeks after inoculation) on the lower leaves and consisted of chlorosis at the margins that progressed inward. Veins initially were green, but leaves eventually became chlorotic, then necrotic, and fell with petioles still attached to the stem. In some cases, all of the foliage died. There was no significant (P = 0.05) isolate × cultivar interaction for root rot at 3 or 10 weeks after inoculation or for severity of foliar symptoms. Thirty-three cultivars commonly grown in southern Minnesota and the RRV were evaluated for reaction to one isolate of F. solani. Root rot severity ranged from 4.2 to 5.7 (1–6 scale) and 3.5 to 4.0 (1–4 scale), at 3 and 9 weeks after inoculation, respectively, and >50% of the plants died by 9 weeks after inoculation. Severity of foliar symptoms was low. These results indicate that isolates of F. solani from the RRV cause root rot and foliar symptoms on soybean and that cultivars grown in the region lack resistance to this pathogen. Foliar symptoms were not identical to those associated with sudden death syndrome.
Identification and Characterization of Banana Bract Mosaic Virus in India
Authors: Rodoni B. C. , Ahlawat Y. S. , Varma A. , Dale J. L. , Harding R. M.
Published: May 2007

We have identified banana bract mosaic potyvirus (BBMV) in banana plants growing in the Coimbatore and Tiruchchirappalli regions of southern India based on symptomatology, particle morphology, sequence homology, and nucleic acid hybridization assays. Potyvirus-like particles typical of BBMV also were detected in sap dips from banana plants growing in Maharashtra State. Sequence comparisons of the C terminus of the coat protein-coding and 3′ untranslated regions revealed that the Indian isolates of BBMV had greater than 96.6 and 97.2% homology with a Philippines isolate at the nucleotide and amino acid levels, respectively. BBMV-infected banana cultivars from the Coimbatore region showed the characteristic mosaic on the bract of the banana inflorescence. In contrast, infected plants growing in the Tiruchchirappalli region and Maharashtra State displayed symptoms similar to those associated with cucumber mosaic cucumovirus and not the characteristic bract mosaic symptom. These results indicate that BBMV is more widespread than previously thought.
Characterization of a Pepper Vein Banding Virus from Chili Pepper in India
Authors: Ravi K. S. , Joseph J. , Nagaraju N. , Prasad S. Krishna , Reddy H. R. , Savithri H. S.
Published: May 2007

A survey conducted in pepper-growing tracts of Karnataka State, covering 165 fields in 33 villages, revealed the occurrence of many pepper mosaic diseases. Based on reactions on selected test plants, the viruses were identified as pepper vein banding virus (PVBV), pepper veinal mottle virus, potato virus Y, cucumber mosaic virus, and tobacco mosaic virus. Among these, PVBV was the most prevalent. PVBV was purified from infected leaves of Capsicum annuum cv. California Wonder. Electron microscopy revealed flexuous rod-shaped particles in the purified preparations. The coat protein (CP) molecular weight was 35,000, which is similar to members of the Potyvirus group. As in other potyviruses, the CP underwent proteolytic degradation to a fragment with a molecular weight of 31,000. Both of these bands cross-reacted with antibodies against tobacco etch virus in Western blots. Polyclonal antibodies were produced against PVBV. Cross-reactivity studies with other potyviral antisera showed that PVBV is serologically closer to peanut mottle virus than to peanut stripe virus or sorghum potyvirus. N-terminal sequence analysis of the intact CP and trypsin-resistant core revealed that PVBV is a distinct member of the Potyvirus group.
Occurrence of Vine Decline Diseases of Melons in Honduras
Authors: Bruton B. D. , Miller M. E.
Published: May 2007

A survey of vine decline diseases of melons (Cucumis melo L.) was conducted on three geographically separate farms (12 fields) in the area of San Lorenzo, Honduras, during the spring of 1996. Symptoms were typical of the vine declines in that the leaves began yellowing and collapsing in the crown just prior to harvest and the decline radiated outward. Crown lesions, typical of many of the vine declines, were observed infrequently. Most plants exhibited no crown lesion. Roots exhibited brown lesions and root corking, and were generally lacking root hairs, although the roots were not macerated. Fruit were small sized, low in sugars, and sunburned. Isolations were made from the crown area, primary root, and secondary roots of affected plants by excising 3- to 5-mm pieces and surface sterilizing for 30 to 60 s with 0.5% sodium hypochlorite. Four tissue pieces from each plant part were placed on 2.0% water agar plus 0.1 g of streptomycin sulfate per liter and their identity maintained. Plates were examined for fungal growth daily for 5 days and hyphal tips from all colonies were transferred to potato dextrose agar and Synthetischer nährstoffärmer agar (2) to allow for sporulation. Rhizoctonia solani Kühn was the predominant fungus isolated from affected plants in several fields, with an incidence as high as 75%. A Pythium sp. was isolated from primary and secondary roots of 50% of the plants on the Santa Rosa farm. Vines exhibiting tan to light brown crown lesions either on one side of the vine or encompassing the crown, but without gumming, always produced colonies of Fusarium semitectum Berk. & Ravenel. Fusarium solani (Mart.) Appel & Wollenweb. emend. W. C. Snyder & H. N. Hans. was isolated from roots of more than 30% of the plants, although this is not unusually high. Crown lesions typical of charcoal rot were observed in some fields, with Macrophomina phaseolina (Tassi) Goidanich being isolated from 65% of the plants in one field. Charcoal rot was a minor problem in all fields but one. Didymella bryoniae (Auersw.) Rehm was not isolated from any of the plants. A Stagonospora-like fungus, which has been demonstrated recently as a potential contributor to vine decline (1), was isolated on 17% of the plants from five fields on the Embarcadero Farm. Monosporascus cannonballus Pollack & Uecker was isolated infrequently in one field on the Santa Rosa Farm. This is the first report of M. cannonballus and a Stagonospora-like fungus in Honduras.

References: (1) M. E. Miller et al. Phytopathology 86:S3, 1996. (2) H. I. Nirenberg. Mitt. Biol. Bundesanst. Land Forstwirtsch. Berlin-Dahlem. 169:1, 1976.