bluuebunny/crossref_metadata_2025 huggingface dataset:
First Report of Dothistroma septospora on Native Limber and Whitebark Pine in Montana
Authors: Taylor J. E. , Walla J. A.
Published: May 2007

Dothistroma septospora (Doroguine) Morelet (= Dothistroma pini Hulbary), the anamorph of Mycosphaerella pini Rostr. in Munk, has been reported to cause needle blight in 29 Pinus species and hybrids in North America, including limber pine (P. flexilis James) in plantings in Kansas, Nebraska, and Ohio. We are unaware of any reports of D. septospora on limber or whitebark pine (P. albicaulis Engelm.) growing within their native ranges in the western United States. In June 1997, limber and whitebark pine in Montana were observed with severe defoliation and symptoms typical of those caused by D. septospora: affected second- and third-year needles were green at the base with brown tips or reddish-brown spots or bands, and black fruiting bodies in discolored portions of needles. Symptomatic needles were collected in natural stands of limber pine at 22 locations representing 15 counties in central, south-central, and southwestern Montana, and whitebark pine at three locations representing two counties in the Crazy Mountains in south-central Montana. Approximately 20 needles and five stromata from each location were examined with dissecting and compound microscopes to observe morphological features. Stromata were black, linear, 150 to 1450 μm (average 650 μm) by 65 to 450 μm (average 190 μm), subepidermal, and erumpent. Conidiophores were hyaline and unbranched. Conidia were 16.0 to 23.5 μm (average 18.5 μm) by 3.0 to 4.1 μm (average 3.4 μm), hyaline, 3 to 5 septate, blunt at the ends, and slightly falcate. The fungus described above was found at all sample locations. The teleomorph, M. pini, was not observed. Symptom expression and mycological characteristics were consistent with Hulbary's lectotype (1) of D. pini (= D. septospora). This is the first report of D. septospora on limber and whitebark pine within the hosts' native ranges.

Reference: (1) R. L. Hulbary. Ill. Nat. Hist. Surv. Bull. 21:231, 1941.
First Report of Soybean Cyst Nematode (Heterodera glycines) on Soybean in Puerto Rico
Authors: Smith J. R. , Chavarria-Carvajal J. A.
Published: May 2007

Soybean (Glycine max (L.) Merr.) winter nurseries have been planted in Puerto Rico at the USDA's Isabela farm for 25 consecutive years. The field has had one soybean crop each year, with a summer fallow period between winter nursery seasons. In February 1998, during an inspection of root nodulation, cysts were discovered on roots of an F2 population (Benning × Pureunkong). Microscopic examination of roots confirmed the presence of female nematodes of Heterodera glycines Ichinohe in various stages of development. No cysts were found when soil and roots were randomly sampled at various growth stages (R1 to R7) from other soybean fields in Puerto Rico (Isabela, Salinas, Lajas, and Juana Diaz). Also, no cysts were observed on roots of common bean (Phaseolus vulgaris) at growth stages R7 to R8 in a neighboring research field. However, cysts were observed on 35-day-old roots of soybean cv. Lee, common bean, and pigeon pea (Cajanas cajun) grown in the above infested soil. A race assay, slightly modified from standard protocols (3), determined that the infested soil contained race 2 of H. glycines. The infested field was rotated to sorghum during the summer of 1998 and then soybeans were planted in the 1998-1999 winter nursery. H. glycines occurs in at least 26 states of the U.S., and in Canada, Asia, and South America (1,2).

References: (1) M. L. Mendes and D. W. Dickson. Plant Dis. 77:499, 1993. (2) R. D. Riggs and D. P. Schmitt. 1989. Soybean Cyst Nematode. Page 65 in: Compendium of Soybean Diseases. 3rd ed. J. B. Sinclair and P. A. Backman, eds. American Phytopathological Society, St. Paul, MN. (3) D. P. Schmitt and G. Shannon. Crop Sci. 32:275, 1992.
Resistance to Bean Golden Mosaic Virus in Bean Genotypes
Authors: Bianchini A.
Published: May 2007

Bean lines MD 806, MD 807, MD 820, MD 829, MD 808, and MD 821, all with high levels of resistance to bean golden mosaic virus (BGMV), were selected under field conditions. On a 1 to 9 scale (1 = symptomless plant; 9 = severe symptoms), the mean disease severity of the MD lines ranged from 1.7 to 3.9 for mosaic symptom (foliar yellowing) and from 1.7 to 2.2 for malformation. In contrast, disease severity in the susceptible cultivars Carioca, Carnaval, and Iapar 20 ranged from 4.1 to 8.7 for mosaic and from 4.0 to 7.3 for malformation. Symptoms on the selected lines were expressed later than on susceptible controls. The MD lines yielded 1.2- to 5.9-fold the yield of the cultivars Carioca and Iapar 20. Under greenhouse conditions, reactions of the bean genotypes to BGMV were similar to those observed in the field. MD 806 and MD 807 were obtained from early crosses involving genotypes that reacted to BGMV infection with mild mosaic (Aeté 1/38 and TMD-1) and mild malformation (Porrillo Sintético and Turrialba 1). Parents of the lines MD 820 and MD 829 were Phaseolus coccineus (of unknown reaction to BGMV) and Carioca. Line MD 648 (DOR-selected line) was the ancestral parent of lines MD 808 and MD 821, which had the highest levels of resistance or tolerance to BGMV. Severity of all BGMV symptoms showed gradual reductions from the earliest parents to their later selected progenies. Responses of the parent genotypes and progenies to BGMV infection suggest a combination of resistance characters in the selected MD lines. MD 806, MD 820, and MD 821 were released in the state of Paraná under the names Iapar 57, Iapar 72, and Iapar 65, respectively.
Variation in Aggressiveness of Canadian Isolates of Phytophthora infestans as Indicated by Their Relative Abilities to Cause Potato Tuber Rot
Authors: Peters R. D. , Platt H. W. (Bud) , Hall R. , Medina M.
Published: May 2007

Studies were conducted in 1995, 1996, and 1997 to determine the ability of Canadian isolates of Phytophthora infestans to cause tuber disease in a variety of potato cultivars. Most isolates of recently introduced multilocus genotypes (US-7, US-8, g11, g26, g29, and g40) were more aggressive on tuber tissue than isolates of the traditional US-1 genotype, based on surface necrosis (SN), lesion depth (LD), and compound aggressiveness index (CAI = SN × LD) components. Other multilocus genotypes (g30, g41, g42, and UN-3) were similar in aggressiveness to US-1. The g11 (US-11) genotype consistently displayed aggressiveness that was intermediate to that of the US-8 and US-1 genotypes. Variation also occurred within a multilocus genotype, and an isolate of the US-8 genotype from New Brunswick was consistently less aggressive than other US-8 isolates. Cvs. Dorita and Island Sunshine were consistently the most resistant to infection, regardless of isolate, relative to the more susceptible responses of Green Mountain, Russet Bur-bank, Kennebec, Superior, Shepody, Red Pontiac, Sebago, and Bintje. Even so, isolates of the newly introduced US-8 genotype were able to cause significantly more disease on these resistant cultivars than isolates of the US-1 genotype. The predominant genotypes currently found in potato production areas in Canada (US-8 and g11) have higher fitness on tuber tissue than displaced, preexisting strains (US-1).
Fusarium Species Pathogenic to Barley and Their Associated Mycotoxins
Authors: Salas B. , Steffenson B. J. , Casper H. H. , Tacke B. , Prom L. K. , Fetch T. G. , Schwarz P. B.
Published: May 2007

Epidemics of Fusarium head blight (FHB) occurred on barley in Minnesota, North Dakota, and South Dakota from 1993 to 1998. The Red River Valley region was most severely impacted by the disease based on assessments of FHB severity in grain samples harvested from commercial fields. Fusarium graminearum was the primary pathogen causing these FHB epidemics. It comprised from 62 to 64% of all Fusarium species isolated from infected kernels from 1994 to 1996. Fusarium poae (range of isolation 13 to 20%),F. sporotrichioides (10 to 17%), and F. avenaceum (6 to 10%) also were isolated from barley kernels and were likely involved in causing some FHB infection, but to a very limited extent. All four Fusarium species were pathogenic on barley in inoculation tests conducted in both the greenhouse and the field. Mycotoxin screens were performed on barley spikes inoculated with the respective species in the greenhouse. Spikes infected with F. graminearum contained deoxynivalenol and 15-acetyldeoxyni-valenol; those infected with F. sporotrichioides contained T-2 toxin, HT-2 toxin, and T-2 tetraol; and those infected with F. poae contained nivalenol. Some isolates of F. poae also produced 15-acetoxyscirpenol and scirpentriol. Although F. graminearum and DON are recognized as the primary FHB pathogen and mycotoxin, respectively, in barley, the possible presence of other Fusarium species and mycotoxins should not be overlooked.
First Report of Southern Blight Caused by Sclerotium rolfsii on St.-John's-Wort
Authors: Keinath A. P. , Rushing J. W. , Dufault R. J.
Published: May 2007

Interest in commercial production of common St.-John's-wort (Hypericum perforatum L.), an herb that is dried, processed, and used as an anti-depressant medication, is increasing. In August 1998, St.-John's-wort growing in the field at Charleston, SC, showed blight symptoms. Leaves on prostrate branches turned reddish-yellow, then brown, and then abscised. As the disease progressed, branches and approximately 10% of the plants were killed. Coarse, white mycelia were present on the bases of dead branches. Segments cut from symptomatic branches were disinfested in 0.5% sodium hypochlorite and placed on potato dextrose agar (PDA) at 25°C. Sclerotium rolfsii Sacc. was isolated from one of 12 branches with discolored leaves and six of six dead branches. For pathogenicity tests, sclerotia were harvested from 6-week-old cultures on PDA. Ten-week-old St.-John's-wort plants, growing in potting mix in 10-cm pots, were inoculated by placing four sclerotia on the soil surface 1 to 1.5 cm from the main stem of each plant. Plants were grown in a greenhouse at 90% relative humidity and 25 to 35°C. Single blighted branches were observed on three plants 12 days after inoculation and all plants were blighted 28 days after inoculation. S. rolfsii was recovered from 10 and 9 of 10 plants inoculated with isolates of S. rolfsii from St.-John's-wort and tomato, respectively. All 10 noninoculated plants remained symptomless. The pathogenicity test was repeated and the results were similar. This is the first report of S. rolfsii causing Southern blight on St.-John's-wort in the United States.
Infection of Olive Trees by Heterodera mediterranea in Orchards in Southern Spain
Authors: Castillo P. , Vovlas N. , Nico A. I. , Jiménez-Díaz R. M.
Published: May 2007

High infection rates of olive feeder roots and soil infestation by the cyst-forming nematode Heterodera mediterranea were found in commercial olive orchards cv. Manzanilla established in sandy soils at two localities of Sevilla Province of Andalucía, southern Spain. No disease symptoms were noted on the aboveground plant parts, but slightly distorted feeder roots and necrotic areas were observed near the infection points. Sedentary juvenile stages and adult females showed a semi-endoparasitic feeding habit. Histopathological studies of infected olive roots showed a disease response typical of cyst nematode infection of susceptible hosts. Nematode feeding induced syncytial formation involving cellular alterations in the cortex, endoder-mis, pericycle, and vascular parenchyma tissues in both cortical and endodermal root cells.
Incidence ofSalmonellaon Fresh Fruits and Vegetables Affected by Fungal Rots or Physical Injury
Authors: Wells J. M. , Butterfield J. E.
Published: May 2007

Enriched wash from healthy and decayed portions of 341 fruits and vegetables collected in the marketplace and affected by fungal rots were tested for suspected Salmonella appearing as black, hydrogen sulfide-positive colonies on Salmonella-Shigella agar incubated at 37°C. Suspected Salmonella occurred in 20.2% of healthy and in 26.4% of decayed portions, two-thirds of which were caused by Alternaria and Botrytis. In a similar analysis of 121 samples with mechanical injuries, in which two-thirds were gouges, cuts, and bruises, there were no significant differences in Salmonella incidence between injured and uninjured portions. Of 332 suspected Salmonella randomly isolated from healthy and decayed or injured portions, 17 (5.1%) were confirmed as Salmonella by physiological and serological testing. When tomato, potato, and onion tissues were inoculated with Salmonella typhimurium, populations of that bacterium increased by one to two logs over a 48-h incubation at room temperature. Coinoculation of tissues with S. typhimurium and Botrytis or Rhizopus, but not Alternaria or Geotrichum, caused a statistically significant increase in populations of Salmonella compared with the controls.
Disease Resistance and Biomass Stability of Forage Pearl Millet Hybrids with Partial Rust Resistance
Authors: Wilson J. P. , Gates R. N.
Published: May 2007

The expression of partial resistance to Puccinia substriata var. indica and its contribution to digestible biomass production in forage pearl millet hybrids were evaluated in field experiments at Tifton, GA. Inbreds Tift 383, Tift 65, and nine inbreds with partial resistance selected from the cross Tift 383 × ‘ICMP 501’ were crossed to Tift 23DA4. The parental inbreds and hybrids were evaluated in natural epidemics in 1996 and 1997. Because of maturity differences among the lines, slope of the regression of logit rust severity on time (apparent infection rate) and area under the disease progress curve (AUDPC) calculated for a defined interval of plant growth (10 days before to 20 days after anthesis) and adjusted for initial rust severity at 10 days prior to anthesis were the most useful indicators of resistance. Inbred resistance was not a reliable predictor of hybrid resistance when evaluated by either variable. Hybrids were evaluated for biomass production in 1996 and 1997 in a split-plot design, with hybrids as main plots and nontreated or chlorothalonil fungicide-treated as subplots. Differences existed among hybrids for AUDPC and for digestible dry matter yield (DDMY) and its components. Over all hybrids, the response between DDMY and final rust severity was described by logarithmic regression. Two clusters of hybrids were identified by cluster analysis of disease-related data from both experiments. The cluster of susceptible hybrids tended to have a lower DDMY and were less stable over year × treatment environments than the cluster of partially resistant hybrids. Lodging in nontreated plots in 1997 primarily occurred in susceptible hybrids. Although resistance was expressed in certain hybrids, greater levels of partial resistance are needed to provide adequate protection against DDMY losses.
Characteristics and Distribution of Potato Latent Carlavirus (Red LaSoda Virus) in North America
Authors: Goth Robert W. , Ellis Peter J. , de Villiers Gerda , Goins E. W. , Wright N. S.
Published: May 2007

A carlavirus (code name RLSV and subsequently named potato latent carlavirus, PotLV) with serological and biological characteristics different from those of potato M carlavirus (PVM) and potato S carlavirus (PVS) was detected in the potato (Solanum tuberosum) cultivar Red LaSoda by the Scottish Agricultural Science Agency in 1992. During a routine electron microscope testing of accessions in the Vancouver Collection of Virus-Free Potatoes growing in the California winter test in 1993, a filamentous rod-shaped virus similar to PVS and PVM was found in a Red LaSoda clone from Nebraska. The virus was isolated and purified. The monoclonal antibody, MAb 4E12, which is highly specific to the PotLV virus, was developed. From 1994 to 1998, the accessions in the Vancouver Collection of Virus-Free Potatoes were assayed by triple antibody sandwich enzyme-linked immunosorbent assay (TAS-ELISA) using the 4E12 MAb. Seven accessions tested from 1994 to 1996 were infected with PotLV. None of the 270 and 267 accessions in this collection tested positive for this virus in 1997 and 1998, respectively. In 1997 and 1998, the 137 accessions in the U.S. National Varietal Collection maintained at Presque Isle, Maine, were also assayed using the 4E12 MAb. The cultivars High Plains, Platte, and Red LaSoda were the only accessions that tested positive for PotLV. Nicotiana benthamiana, N. megalosiphon, and N. occidentalis are new systemic hosts for PotLV. TAS-ELISA with the 4E12 MAb is now part of the standardized test for PotLV in Canada.
Disease Development and Changes in the Natural Pseudomonas syringae pv. tomato Populations on Field Tomato Plants
Authors: Cuppels D. A. , Elmhirst J.
Published: May 2007

The probe TPRI, derived from the Pseudomonas syringae pv. tomato gene cluster controlling production of the phytotoxin coronatine, was used in conjunction with the semiselective medium VBTar to trace natural populations of the pathogen on tomato plants from just before planting to harvest. In a survey of transplant seedlings in greenhouses, P. syringae pv. tomato populations ranged from 8 × 100 to 3.2 × 105 CFU/g of leaf tissue. Copper-sprayed seedlings had similar populations to nonsprayed plants, but copper tolerance was common among the P. syringae pv. tomato strains surveyed. Transplant seedlings from three greenhouses were tagged, randomly planted in three grower fields, and monitored for P. syringae pv. tomato and disease severity over two growing seasons. Statistical analysis indicated that, when the P. syringae pv. tomato populations of greenhouse plants were small, as recorded in this study, there was no correlation between greenhouse infestation and disease severity in the field. Environmental conditions played a greater role than greenhouse infestation in disease development. Once formed, leaf lesions remained a good inoculum source (104 to 105 CFU) throughout the 7-week life of the leaf. Bacterial speck damage correlated well in both years (r = 0.80 and r = 0.86, respectively) with P. syringae pv. tomato population levels.
Biological Properties of Apple Scar Skin Viroid: Isolates, Host Range, Different Sensitivity of Apple Cultivars, Elimination, and Natural Transmission
Authors: Desvignes J. C. , Grasseau N. , Boyé R. , Cornaggia D. , Aparicio F. , Di Serio F. , Flores R.
Published: May 2007

Studies conducted over the last 10 years have revealed that the disease caused by the apple scar skin viroid (ASSVd) is extremely rare in Europe. ASSVd was detected by molecular hybridization and indexing in field plots on the apple indicators Starkrimson and Indo, which showed symptoms of dapple apple disease within 2 years, and rough scarred skin within 3 years, respectively. Results from both approaches were in agreement. In an attempt to improve the biological detection of ASSVd, the Japanese PK13 isolate was inoculated to 4 Prunus, 13 Malus, 17 Pyrus, and 17 other pomaceous species. All the species tested of the Malus, Pyrus, Sorbus, Chaenomeles, Cydonia, and Pyronia genera were susceptible to ASSVd based upon back indexing and hybridization, but none developed leaf or bark symptoms during a 2-year period. The viroid was not detected in the tested members of genera Amelanchier, Aronia, Cotoneaster, Crataegus, Prunus, and Pyracantha. Symptoms on fruit of 42 commercial apple cultivars experimentally inoculated with ASSVd fell into five groups ranging from inconspicuous spots to severely scarred skin and cracking. ASSVd was eliminated from most of the infected apple plants when they were subjected to a dormant stage followed by thermotherapy and shoot tip grafting. Analysis of more than 400 apple seedlings, originated from Starkrimson and Indo fruits with typical ASSVd symptoms, showed that there is little or no seed transmission of this viroid. However, ASSVd was transmitted at a low rate under field conditions to adjacent trees.
Stem and Root Resistance to Tobacco Black Shank
Authors: Csinos A. S.
Published: May 2007

Stem lesion development in the absence of root decay in tobacco black shank caused by Phytophthora parasitica var. nicotianae has become common in the Coastal Plain tobacco growing area in Georgia. All aboveground symptoms of wilting, blackening of lower stem, and destruction of the pith can occur on tobacco without or with minor root decay. This type of black shank disease development occurred in 14 of 15 locations evaluated and accounted for about 30% of diseased plants. Cultivars with Florida 301—derived resistance had very low stem resistance to race 0 of the pathogen. However, root inoculations of these cultivars resulted in disease reactions typical of those expected in vivo in Georgia. Cultivars Coker 371-Gold and NC 71 and the breeding line 1071 demonstrated high resistance to inoculation with race 0 of P. parasitica var. nicotianae in both the stem and the roots, but they were susceptible when stem-inoculated with race 1 of the pathogen. Severity of root decay was isolate dependent.
Occurrence of a Subpopulation of Xanthomonas oryzae pv. oryzae with Virulence to Rice Cv. IRBB21 (Xa21) in Southern India
Authors: Priyadarisini V. Brindha , Gnanamanickam S. S.
Published: May 2007

About 200 isolates of the bacterial blight pathogen Xanthomonas oryzae pv. oryzae were obtained from infected rice (Oryza sativa L.) leaf samples from the Palghat District of Kerala State in southern India during January and February, 1998, when there was a severe epidemic of bacterial blight in the farmers' fields. One hundred and forty of these isolates were assayed for pathogenicity on rice cv. IR24 (no R gene), IRBB21 (Xa21), and NH56 (Xa4+xa5+xa13+Xa21) at their maximum tillering stage by the standard clip-inoculation technique (1) at the Regional Agricultural Research Station (Kerala Agricultural University), Pattambi. In two separate experiments, all the isolates were found to be pathogenic to IR24, producing lesions greater than 10 cm in length. None of the isolates induced susceptible symptoms on cv. NH56 and the average lesion length was less than 2 cm. Twenty of the 140 isolates, however, showed virulence to IRBB21 (seeds supplied by S. R. McCouch, Cornell University, and by P. Ronald, University of California-Davis) and induced lesions of 10.0 to 18.0 cm. We report here the presence of Indian races of X. oryzae pv. oryzae that are virulent to IRBB21 (Xa21), contradicting an earlier report of avirulence (2). These results suggest that the deployment of Xa21 alone will not be a sound strategy for the management of bacterial blight in southern India.

References: (1) S. S. Gnanamanickam et al. Plant Dis. 78:173, 1994. (2) G.-L.Wang et al. Mol. Plant-Microbe Interact. 9:850, 1996.
Fairy Rings in Turf Associated with the Bird's Nest Fungus Cyathus stercoreus
Authors: Mercier J. , Carson T. D. , White D. B.
Published: May 2007

During the summer of 1998, several fairy rings with the fruiting bodies of a bird's nest fungus were observed on two greens at the University of Minnesota turf plots in St. Paul. Both greens, a 3-year-old annual bluegrass green and a 2-year-old creeping bentgrass green, were constructed of a 90% sand: 10% reed sedge peat soil mix. The fungus was identified as Cyathus stercoreus (Schwein.) de Toni (Nidulariaceae) (1). The fruiting bodies were approximately 15 mm tall and 8 mm wide. The fairy rings were irregular in shape, with a diameter of up to 50 cm, and contained up to 120 fruiting bodies per ring. On annual bluegrass, chlorotic and necrotic grass was observed at the edge of the rings in July but those damaged areas recovered in August. No symptoms were associated with the rings in creeping bentgrass. Rings were first discovered in June and early July and expanded by about 10 cm in 30 days. New fruiting bodies appeared during July and August as the rings expanded. The application of the fungicide chorothalanil did not affect the rings. This is the first report of a bird's nest fungus associated with fairy ring in turf.

Reference: (1) H. J. Brodie. 1975. The Bird's Nest Fungi. University of Toronto Press, Toronto.
First Report of Crown Gall, Caused by Agrobacterium tumefaciens on Geraldton Wax (Chamelaucium uncinatum) in South Africa
Authors: Carstens E. , Dawood Z. , Mansvelt E. L. , Serfontein S. , Malan D. G.
Published: May 2007

Geraldton wax (Chamelaucium uncinatum, family Myrtaceae) plants are grown as cutflowers for the export market in South Africa. In July 1998, gall-like structures were observed on collars and roots of Geraldton wax plants in commercial fields in Wellington. The galls were observed after plants exhibited poor growth. The galls varied in size and in texture from soft and spongy to hard. Secondary symptoms involved poor root development and browning of stem tissues near galls. Isolations from the galls yielded nearly pure cultures of a Gram negative, rod-shaped bacterium on Roy Sauer medium (2), typical of an Agrobacterium sp. Carbon source utilization testing with the Biolog GN Bacterial Identification System (version 3.50) confirmed the bacterium as a biovar of A. tumefaciens with a similarity of 0.88. Pathogenicity was confirmed by injecting 4- to 6-week old tomato and tobacco plants and 1-year-old Geraldton wax plants with approximately 5 μl of the bacterial suspension (108 CFU/ml) in sterile, distilled water. Inoculated plants were then transferred to a greenhouse at 25°C. Galls developed 1 month after inoculation. The bacterium was readily reisolated from the inoculated plants. A. tumefaciens is endemic to South Africa and has a very wide host range that includes several ornamentals (1). This is the first report of A. tumefaciens on Geraldton wax plants in South Africa.

References: (1) J. F. Bradbury. 1986. Guide to Plant Pathogenic Bacteria. CAB Int., Slough, U.K. (2) N. W. Schaad. 1988. Laboratory Guide for Identification of Plant Pathogenic Bacteria. The American Phytopathological Society, St. Paul, MN.
Survival of Conidia of Discula destructiva in Frass of the Convergent Lady Beetle
Authors: Hed Bryan E. , Windham Mark T. , Grant Jerome F.
Published: May 2007

The survival of conidia of Discula destructiva in frass of convergent lady beetles (Hippodamia convergens) was investigated. D. destructiva was isolated from frass pellets of 76% of adult convergent lady beetles exposed to D. destructiva for 1 h. Of the beetles from which D. destructiva was initially isolated, more than 80, 32, 19, 13, and 12.5% retained viable conidia of D. destructiva internally for at least 12, 24, 48, 72, and 96 h, respectively. Numbers of conidia, estimated with a hemacytometer, ranged from 0 to 3.2 × 106 conidia per frass pellet.
Components of Resistance to Rhizoctonia solani Associated with Two Tall Fescue Cultivars
Authors: Green D. E. , Burpee L. L. , Stevenson K. L.
Published: May 2007

Components of resistance to Rhizoctonia solani in the tall fescue cultivars Kentucky 31 (moderately resistant) and Mojave (susceptible) were evaluated under controlled environmental conditions. Size and expansion rate of foliar lesions were recorded on 100 individual plants of each cultivar. Lesions on the first fully expanded leaves of 6- to 10-month-old inoculated plants covered a significantly greater proportion of the leaf width on cv. Mojave compared to Kentucky 31. Rate of lesion expansion was also greater on cv. Mojave than on Kentucky 31. Lesion size and rate of expansion were greater on the second compared to the first fully expanded leaf of both cultivars. Wider leaves and slower lesion expansion are two components responsible for the greater level of resistance to R. solani in cv. Kentucky 31 compared to Mojave tall fescue.
Differences in Aggressiveness of Sphaeropsis sapinea RAPD Marker Group Isolates on Several Conifers
Authors: Blodgett J. T. , Stanosz G. R.
Published: May 2007

Seedlings of Scot's pine varieties East Anglia and Austrian Hills, red pine, mugho pine variety Pumileo, Colorado blue spruce, Douglas-fir, and balsam fir were wounded and inoculated with water agar plugs colonized by isolates of the two random amplified polymorphic DNA (RAPD) marker groups (A and B) of Sphaeropsis sapinea. Isolates were obtained from hosts in Michi-gan, Minnesota, and Wisconsin. Symptom severity (distance from the inoculation site at which necrotic needles were present) resulting from inoculations with each group A isolate exceeded that from inoculations with each group B isolate on all hosts except Colorado blue spruce. Hosts varied considerably in their responses to group A isolates. Based on symptom severity, East Anglia Scot's pine was most susceptible and balsam fir was least susceptible when inoculated with group A isolates. The pathogen was recovered from both symptomatic and asymptomatic seedlings inoculated with isolates of either group. Results emphasize the importance of characterizing a RAPD marker group(s) of S. sapinea encountered in the field or used in research; the need for comparative evaluations of resistance among coniferous genera, species, and varieties to S. sapinea of both groups; and the potential for asymptomatic persistence of S. sapinea from both groups in or on several coniferous hosts.
Races of Puccinia graminis in the United States During 1996
Authors: McVey D. V. , Long D. L. , Roberts J. J.
Published: May 2007

Stem rust caused negligible yield losses in 1996 in the United States. Wheat stem rust was first found during the second week of April in a field of soft red winter wheat southwest of Houston, Texas. Race Pgt-TPMK continues to predominate, with 66% of 273 isolates from 100 collections. TPMK represented 76 and 63% of the isolates from wheat in fields and nurseries, respectively. Race QFCS was identified at a frequency of 12 and 29% from farm fields and nurseries, respectively, and 26% overall. Eight other races consisted of 3% or less of the isolates. From barley, race QCCJ, virulent to the Rpg-1 gene for resistance to stem rust, was identified in only 12% of 77 isolates of 27 collections, while TPMK consisted of 64% of the isolates. No virulence was found to wheat lines with genes Sr9b, 13, 22, 24, 25, 26, 27, 29, 30, 31, 32, 37, Gt, or Wld-1. Oat stem rust was first found in late April in southern Louisiana and central Texas. Race NA-27, virulent to Pg-1, -2, -3, -4, and -8, was again the predominant race in the United States, comprising 91% of 93 isolates from 36 collections. NA-5 and NA-16 were the other two races identified, comprising 4% each.
First Report of East African Cassava Mosaic Begomovirus in Ghana
Authors: Offei S. K. , Owuna-Kwakye M. , Thottappilly G.
Published: May 2007

Virus species causing cassava mosaic disease have been categorized into three classes based on their reaction with monoclonal antibodies (MAbs) and their distribution (2). These viruses have different, scarcely overlapping distribution: African cassava mosaic begomovirus (ACMV) occurs in Africa west of the Rift Valley and in South Africa; East African cassava mosaic (EACMV) occurs in Africa east of the Rift Valley and in Madagascar; and Indian cassava mosaic virus (ICMV) occurs in India and Sri Lanka (2). During 1998, surveys were conducted in farmers' fields in Ghana to assess the incidence and reaction of local cassava cultivars to cassava mosaic disease. Leaf samples from symptomatic plants were indexed by triple antibody sandwich-enzyme-linked immunosorbent assay with crude extracts and monoclonal antibodies obtained from the International Institute of Tropical Agriculture (IITA). Each sample was assayed with monoclonal antibody SCR 23, which detects ACMV and EACMV, SCR 33, which detects ACMV, and SCR 58, which detects ICMV. None of the samples reacted with SCR 58. Two of the samples collected from the western region of Ghana produced strong reactions with MAb SCR23 but did not react with ACMV-specific MAb SCR 33. This result was consistent in three separate experiments conducted on the samples, confirming that the virus was EACMV and not ACMV. The results extend the work by Ogbe et al. (1) and provide further evidence of the occurrence of EACMV in west Africa.

References: (1) F. O. Ogbe et al. Plant Dis 83:398, 1999. (2) M. M. Swanson and B. D. Harrison. Trop. Sci. 34:15, 1994.
Rhizoctonia Species and Anastomosis Groups from Corn Kernels in Turkey
Authors: Demirci E. , Kordali S.
Published: May 2007

In 1996, 165 samples of corn (Zea mays L.) kernels to be tested for seed-borne fungi were obtained from five provinces throughout the major corn-producing areas in the eastern Black Sea Region of Turkey: Artvin (41 samples), Rize (28 samples), Trabzon (32 samples), Giresun (30 samples), and Ordu (34 samples). A subsample of kernels (≈100 g each) from each sample was surface-disinfected in 3.5% NaOCl for 1 min. Kernels were washed in three changes of sterile water, and 100 kernels per subsample were placed in petri plates (5 kernels per plate) containing potato dextrose agar. After 5 to 7 days of incubation at 25°C in the dark, cultures were examined at 40× magnification for mycelia of Rhizoctonia spp. From 16,500 kernels examined, 40 isolates of Rhizoctonia spp. were recovered and characterized according to colony morphology and hyphal anastomosis using known tester isolates of Rhizoctonia spp. (1). Of these isolates, 10 were identified as R. solani, 18 as R. zeae, and 12 as binucleate Rhizoctonia sp. R. solani isolates were assigned to three anastomosis groups (AG): AG-4 (two isolates), AG-5 (two isolates), and AG-10 (six isolates). Binucleate Rhizoctonia sp. isolates were all assigned to AG-Ba. R. solani AG-4 and -5 and binucleate Rhizoctonia AG-Ba isolates were obtained from Artvin; R. solani AG-10 isolates were obtained from Ordu; and R. zeae isolates were obtained from Trabzon and Giresun. This is the first reported observation of Rhizoctonia spp. and anastomosis groups on corn kernels from Turkey.

Reference: (1) B. Sneh et al. 1991. Identification of Rhizoctonia Species. The American Phytopathological Society, St. Paul, MN.
Identification of Rhizoctonia solani AG-UNK from Rice and Rice Fields in Texas as AG-11
Authors: Jones R. K. , Carling D. E.
Published: May 2007

A survey of Texas rice fields in 1984 and 1985 yielded collections of Rhizoctonia solani AG-1 IA (causal agent of sheath blight of rice), R. oryzae (causal agent of sheath spot of rice), and a collection of eight multinucleate Rhizoctonia solani-like isolates that would interanastomose, but not anastomose, with tester isolates of AG-1 through AG-8 (representing those available at that time). In 1985, the isolates were characterized as R. solani AG-UNK (2). Isolates were recovered as atypical sclerotia from elutriated field soils in rice-soybean and rice-fallow rotations. Isolates also were recovered from late-season stem lesions nearly identical to those associated with sheath spot disease and from rice residues at locations throughout the upper Gulf Coast of Texas but at extremely low frequencies compared with recovery of R. solani AG-1 IA and R. oryzae. Teleomorphs of R. solani AG-UNK were observed during middle to late season on rice sheaths and matched descriptions of Thanatephorus cucumeris. Isolates were pathogenic on rice and soybean foliage in greenhouse trials but caused no significant yield losses when inoculated on adult rice plants (50 days after emergence) in field trials (2). Isolates exhibited mean hyphal diameters of 5.1 μm, averaged 8.3 nuclei per penultimate cell, grew 0.53 mm/h at 28°C on potato dextrose agar, and were negative in phenol tests (2). From samples maintained in storage during the past 15 years, the isolates have now been identified as AG-11 based on positive anastomosis with tester strains of AG-11 (1). This report records the occurrence of AG-11 in Texas, establishes the identity of the AG-UNK group, and expands the known geographic range of AG-11 in the United States.

References: (1) D. E. Carling et al. Phytopathology 84:1387, 1994. (2) R. K. Jones and S. B. Belmar. Plant Dis. 73:1004, 1989.
First Report of Stachybotrys chartarum Causing Soybean Root Rot
Authors: Li S. , Hartman G. L.
Published: May 2007

Stachybotrys chartarum (Ehrenb. ex Link) S.J. Hughes was isolated from surface-disinfested soybean (Glycine max (L.) Merr.) root lesions. The fungus was cultured on potato dextrose agar, and its morphology was examined by light and environmental scanning electron microscopy. Conidiophores were determinate, macronematous, solitary or in groups, and simple or irregularly branched. Phialides occurred in whorls and were obovate or ellipsoidal. Conidia were unicellular, round to ellipsoidal, 5 to 13 × 4 to 7 μm, initially hyaline, smooth-walled, and dark brown to black and rough-walled when mature. A pure culture obtained from infected soybean roots was used to test pathogenicity under greenhouse and growth-chamber conditions. S. chartarum was grown on sterilized sorghum grain for 2 weeks and placed in soil 2 to 3 cm below sown soybean seeds. Noninfested sorghum grain was used as a control. All soybean plants inoculated with S. chartarum had root lesions ranging from 7 to 25 mm 21 days after sowing, while control plants did not have any measurable root rot. The DNA sequence of the internal transcribed spacer (ITS) region was 100% identical to S. chartarum strain ATCC 9182 (1) but differed from all published sequences of other Stachybotrys and Memnoniella spp. in GenBank (1). Polymerase chain reaction with S. chartarum-specific primer StacR3 and IT51 (1) amplified a 198-bp DNA fragment from the total genomic DNA. The molecular evidence further supports the identification of S. chartarum isolated from soybean. This is the first report of S. chartarum causing soybean root rot.

Reference: (1) R. A. Haugland and J. L. Heckman. Mol. Cell. Probes 12:387, 1998.
Fusarium oxysporum and F. sambucinum Associated with Root Rot of Amaranthus hybridus in South Africa
Authors: Chen W. , Swart W. J.
Published: May 2007

Amaranthus hybridus has been identified as an important alternative vegetable crop with potential for increased commercial production in South Africa (1). In summer 1999, severe losses occurred in a large plot of 2-month-old A. hybridus plants on an experimental farm near Bloemfontein, South Africa. More than 90% of the plants were severely stunted, with chlorotic foliage that was wilted in most cases. Root rot was present in all symptomatic plants and was clearly visible as an amber to brown discoloration of tap and secondary roots; in severe cases, white mycelium was clearly visible on diseased root tissue. Isolations from symptomatic roots were made on potato dextrose agar (PDA) amended with streptomycin sulfate. Isolates (N = 121) were recovered from diseased roots (n = 89). The two most frequently isolated fungi were transferred to carnation leaf agar and identified as Fusarium oxysporum (n = 90, 74%) and F. sambucinum (n = 29, 24%). Pathogenicity tests with one isolate of each species were performed in the greenhouse on 1-month-old potted A. hybridus seedlings (10 plants per treatment). A single hyphal tip of each isolate was transferred to PDA and incubated at 25°C for 7 days in the dark. Five 4-mm-diameter mycelial plugs were taken and placed directly on the taproot of each plant, halfway along the length and ≈30 mm below the soil surface. Control plants were treated with uncolonized PDA plugs. Seedlings inoculated with either fungus exhibited wilting within 7 days; stunting, chlorosis (pale green to yellow), and root necrosis after 2 weeks; and mortality after 4 weeks. Inoculated plants were removed from pots after 3 weeks, roots were washed free of potting soil, and necrotic lesion length was measured. Necrosis and discoloration of root tissue were similar to those observed in field plants. The mean length of tissue necrosis induced by the fungi was 22.5 and 34.8 mm for F. oxysporum and F. sambucinum, respectively. F. sambucinum, thus, was more pathogenic than F. oxysporum despite being recovered significantly less often from field plants. Control plants inoculated with noninfested PDA plugs remained healthy. The presence of both pathogens was confirmed by reisolation from artificially inoculated taproots of all plants. No Fusarium spp. were recovered from the 10 control treatments. F. oxysporum has been reported on diseased red root pigweed (A. retroflexus) in the United States (2), but this is the first report of both F. oxysporum and F. sambucinum as causal agents of root rot in A. hybridus. These pathogens, therefore, must be considered a potential threat to commercial production of A. hybridus in South Africa and elsewhere.

References: (1) W. J. Swart et al. S. Afr. J. Sci. 93:22, 1997. (2) R. M. Harveson and C. M. Rush. Plant Dis. 81:85, 1997.
Pathotype and Avirulence Gene Diversity of Pyricularia grisea in Thailand as Determined by Rice Lines Near-Isogenic for Major Resistance Genes
Authors: Mekwatanakarn Poonsak , Kositratana Wichai , Levy M. , Zeigler R. S.
Published: May 2007

Five hundred twenty-seven isolates of Pyricularia grisea were collected from trap rice cultivars of indigenous and exotic origin across three seasons at five sites in Thailand. Single conidium isolates were inoculated onto 15 rice lines near-isogenic (NILs) for resistance genes, one recurrent parent, and two local cultivars. One hundred seventy-five pathotypes were identified, of which 160 were represented by fewer than eight isolates. Predicted pathotype number was estimated at greater than 450 for the study region. Significant differences in pathotype diversity were detected across sites, seasons, and among isolates collected from exotic versus indigenous hosts. Isolates and pathotypes with greater numbers of virulence genes (as inferred from compatibility with NILs) were less common than those with fewer virulence genes. Analysis of virulence distributions among isolates grouped according to their MGR586 DNA-fingerprint similarities (i.e., “lineages”) also showed that, for the most commonly represented lineages, isolates with fewer virulence genes predominated. Lineages represented by one or a few isolates had greater numbers of virulence genes. Lower frequency of recovery of isolates with accumulated virulence genes is consistent with an associated fitness penalty. Resistance genes Pi 1, Pi z-5, and Pi ta2 were broadly effective across this population, compatibility with Pi 1 and Pi z-5 was very rare, and no isolate combined compatibility with both genes. Well-represented (more than 20 isolates) MGR586 lineages showed specific incompatibilities with some NILs, but these were restricted to Pi 1 and Pi z-5. No combination of resistance genes would confer resistance across all lineages.
Factors Affecting the Transmission and Spread of Sugarcane yellow leaf virus
Authors: Schenck S. , Lehrer A. T.
Published: May 2007

Sugarcane, Saccharum spp. hybrid, is widely infected in the United States and many other countries with a yellowing and stunting disease called sugarcane yellow leaf syndrome. The causal agent, Sugarcane yellow leaf virus (ScYLV), is a Polerovirus of the Luteoviridae family. In this study, it was transmitted by the sugarcane aphid, Melanaphis sacchari, and also by the corn leaf aphid, Rhopalosiphum maidis, and the rice root aphid, R. rufiabdominalis. Two other aphids that infest sugarcane in Hawaii did not transmit the virus. Some Hawaiian sugarcane cultivars are susceptible to ScYLV, while others remain virus-free in the field. The latter were not infected when inoculated with viruliferous M. sacchari. Virus-free plants of susceptible cultivars were produced through apical meristem culture and were readily reinfected by viruliferous M. sacchari. They were also quickly reinfected when planted in a field in proximity to other infected sugarcane naturally infested with M. sacchari. Sugarcane cultivars are hybrids of several Saccharum species. In a field-grown collection of Saccharum and related species, 11 to 71% of the clones of four of the species were infected with ScYLV. None of the related genus Erianthus plants were infected, but four clones were infected experimentally by aphid inoculation. A low to moderate percentage of corn, rice, and sorghum seedlings became infected when inoculated with ScYLV, but barley, oats, and wheat proved to be very susceptible. None of seven weeds common in sugarcane fields were infected with ScYLV.
Improved Efficiency of Zea mays Agroinoculation with Maize streak virus
Authors: Martin D. P. , Rybicki E. P.
Published: May 2007

Agroinoculation is a technique permitting the transmission of geminivirus genomes cloned in Agrobacterium tumefaciens into a wide variety of mono- and dicotyledonous host plants. Most geminiviruses are obligately transmitted by insect vector species under natural conditions; therefore, agroinoculation has greatly simplified the study of this group of viruses. In many cases, agroinoculation has replaced insect transmission, and has been used to compare virulence characteristics among viruses. Here we report on the discovery that, in agroinfectious Maize streak virus constructs, the orientation of cloned viral genomes relative to the Cauliflower mosaic virus 35S (CaMV35S) promoter of the binary cloning vector pBI121 can significantly affect agroinfectivity of the constructs. Rates at which plants became symptomatic were significantly higher when agroinoculating maize seedlings with constructs containing the CaMV35S promoter upstream of the viral replication-associated protein (Rep) gene than when the same viruses were cloned either in the opposite orientation or into a vector without a strong eukaryotic promoter sequence. Plants infected using the construct with Rep cloned downstream of the CaMV35S promoter also displayed more stunting and, in the early stages of the infection, more severe chlorotic streak symptoms.
Control of Stewart's Wilt in Sweet Corn with Seed Treatment Insecticides
Authors: Pataky J. K. , Michener P. M. , Freeman N. D. , Weinzierl R. A. , Teyker R. H.
Published: May 2007

Corn flea beetles, Chaetocnema pulicaria, vector Erwinia stewartii (synamorph Pantoea stewartii), which causes Stewart's bacterial wilt of corn (Zea mays). A seed treatment insecticide, imidacloprid, killed flea beetles and reduced the number of feeding wounds and Stewart's wilt symptoms per leaf in greenhouse studies. The objective of our research was to evaluate the ability of imidacloprid and thiamethoxam seed treatments to control Stewart's wilt on sweet corn hybrids under field conditions with naturally occurring populations of the corn flea beetle. Six field trials were planted at four locations in 1998. Eleven field trials were planted at nine locations in 1999. The treatment design was a factorial of sweet corn hybrids and seed treatments. Stewart's wilt incidence ranged from 0 to 54% in the 1998 trials. Incidence of Stewart's wilt in nontreated plots of the susceptible hybrid Jubilee ranged from 2% at the 8-leaf stage to 77% 1 week after mid-silk in the 1999 trials. Seed treatment insecticides reduced the incidence of Stewart's wilt by ≈50 to 85% relative to nontreated controls. The level of control was ≈75 to 85% in seven trials planted before 1 June 1999, when incidence of Stewart's wilt on nontreated Jubilee ranged from 4 to 71%. The level of control was ≈50 to 70% in the three trials planted after 1 July 1999, when incidence of Stewart's wilt on nontreated Jubilee ranged from 44 to 73%. Although comparisons varied, the level of control gained from seed treatment insecticides was similar to the next higher level of host resistance. Seed treatment insecticides appear to control Stewart's wilt during very early growth of corn plants, when foliar applications of insecticides are ineffective and the effectiveness of host resistance varies depending on the proximity of flea beetle feeding sites to the plant's growing point.