bluuebunny/crossref_metadata_2025 huggingface dataset:
Lisianthus Leaf Necrosis: A New Disease of Lisianthus Caused by Iris yellow spot virus
Authors: Kritzman A. , Beckelman H. , Alexandrov S. , Cohen J. , Lampel M. , Zeidan M. , Raccah B. , Gera A.
Published: May 2007

Unusual viral symptoms were seen on lisianthus (Eustoma russellianum) grown in the Besor area in Israel. Symptoms included necrotic spots and rings on leaves and systemic necrosis. Preliminary analyses suggested that the disease was caused by a tospovirus. Virus particles typical of a tospovirus were observed with electron microscopy in samples taken only from symptomatic leaves. Double-antibody sandwich enzyme-linked immunosorbent assay tests of leaf sap, extracted from lisianthus and mechanically inoculated indicator plants, gave a strong positive reaction to Iris yellow spot virus (IYSV). Polyclonal antibodies prepared against IYSV enabled specific detection of the virus in crude sap from infected plants. Western blot analysis showed that IYSV was serologically distinct from Tomato spotted wilt virus (TSWV). Primers specific to the nucleocapsid gene of IYSV were used in a reverse transcription-polymerase chain reaction assay (RT-PCR) to verify the presence of IYSV. RT-PCR gave an expected PCR product of approximately 850 bp. The sequence of the cloned nucleocapsid gene confirmed the identity of IYSV, thus confirming IYSV infection of lisianthus. This is the first report of IYSV infection in dicotyledons.
Solanaceous Weeds as Possible Sources of Cucumber mosaic virus in Southern Illinois for Aphid Transmission to Pepper
Authors: Hobbs H. A. , Eastburn D. M. , D'Arcy C. J. , Kindhart J. D. , Masiunas J. B. , Voegtlin D. J. , Weinzierl R. A. , McCoppin N. K.
Published: May 2007

Over 5,000 individual plants representing approximately 55 species from an area in southern Illinois where Cucumber mosaic virus (CMV) has been a major problem in pepper (Capsicum annuum) were tested for the presence of CMV by enzyme-linked immunosorbent assay (ELISA). Representative ELISA-positive samples were checked by western blot tests to confirm virus-specific reactions. Nearly all of the infected plants detected were either Solanum ptycanthum (eastern black nightshade) or Physalis spp. (principally P. heterophylla, groundcherry). Over 1,000 pepper transplants and approximately 500 tomato transplants, collected prior to planting, were negative for CMV by ELISA. In aphid transmission (arena) experiments, all five aphid species tested were capable of transmitting CMV from nightshade to pepper: Aphis fabae subsp. solanella, Aphis gossypii, Myzus persicae, Rhopalosiphum padi, and Sitobion avenae. Aphis fabae subsp. solanella, A. gossypii, and A. nerii were able to transmit CMV from P. heterophylla to pepper. Aphis fabae subsp. solanella was commonly found colonizing nightshade from May through October in southern Illinois.
Characterization of X-Disease Phytoplasmas in Chokecherry from North Dakota by PCR-RFLP and Sequence Analysis of the rRNA Gene Region
Authors: Guo Y. H. , Cheng Z.-M. , Walla J. A.
Published: May 2007

Genetic variation of X-disease phytoplasma strains from chokecherry (ChX) in North Dakota and nearby sites, and their relatedness with three standard strains of the X-disease phytoplasma group, eastern X-disease (CX), western X-disease (WX), and goldenrod yellows (GR1) phyto-plasmas, were studied. Primer pairs were developed to amplify the 23S ribosomal RNA (rRNA) gene and the 16S/23S spacer region. The rRNA genes (16S rRNA, 23S rRNA, and two ribosomal protein [rp] genes) and the 16S/23S spacer region were amplified by polymerase chain reactions. The restriction fragment length polymorphism (RFLP) patterns of 16S rRNA, 23S rRNA, and rp genes, generated by digestion with four restriction enzymes (AluI, HpaII, MseI, and RsaI), showed no difference among 43 ChX phytoplasma isolates. Sequencing of the 441-bp 16S/23S spacer region revealed variation at four positions among 12 ChX phytoplasma strains. A tRNAIle and other conserved sequences were identified in the spacer region. Among X-disease subgroups, RFLP analysis indicated that ChX is similar to WX, closely related to CX, and easily distinguished from GR1. Sequencing indicated that ChX is closer to CX than to WX. Together, the analyses indicated that ChX phytoplasmas are genetically different from the standard strains of other X-disease phytoplasma subgroups.
First Report of Phytophthora Root and Collar Rot of Alder in Hungary
Authors: Szabó Ilona , Nagy Z. , Bakonyi J. , Érsek T.
Published: May 2007

In June 1999, a disease associated with mortality of Alnus glutinosa, was observed in a 12- to 18-year-old peatland plantation in northwest Hungary. The root and collar rot symptoms were similar to those caused by Phytophthora cambivora in tree species other than alders. Nine isolations were made from diseased roots and soil samples using the Rhododendron leaf baiting method. Three isolates recovered from two sites, approximately 2 km apart, exhibited similar growth and morphology in vitro and were pathogenic to 2-year-old trees of A. glutinosa following inoculation of root collars. All three isolates had amphigynous long, two-celled antheridia. The mean diameter of oogonia ranged from 39.5 to 64.6 μm. They also produced nonpapillate, ellipsoid, non-caducous sporangia 26.9 to 50.5 μm long and 19.3 to 38.5 μm wide with broad exit pores in soil filtrate. These characteristics were similar to those reported for Phytophthora on alder from elsewhere in Europe and for P. cambivora that is not a pathogen of alder (1,2). However, Hungarian isolates from alder, in contrast to P. cambivora, were homothallic like previously recorded isolates from alder, formed nonornamented oogonia and developed colonies at lower optimum (approximately 25°C) and maximum (approximately 30°C) temperatures on carrot agar. A comparison with Phytophthora from alder from other countries (courtesy of C. M. Brasier) showed that the Hungarian isolates have smooth-walled oogonia typical of Swedish isolates rather than the ornamented oogonia of U.K. isolates, but have the appressed, slightly woolly colony morphology like U.K. isolates rather than the fluffy growth found in Swedish isolates. Moreover, cellulose acetate electrophoresis of glucose-6-phosphate isomerase revealed one homodimer band in Hungarian isolates that was identical with that of the Swedish isolate from alder P876 and isolates P1010 and P1011 of P. cambivora (courtesy of C. M. Brasier). This band comigrated with the middle one of the five-banded U.K. standard isolate P772. Molecular evidence (2) indicates that the Phytophthora from alder with its unusual characteristics is not a species in the strict sense but comprises natural hybrids that may have originated in an interspecific hybridization event between a P. cambivora-like species and an unknown species similar to P. fragariae. On this basis, the Hungarian Phytophthora from alder might have evolved similarly. It remains to be determined whether the pathogen was introduced or has developed independently.

References: (1) C. M. Brasier et al. Plant Pathol. 44:999, 1995. (2) C. M. Brasier et al. Proc. Natl. Acad. Sci. USA 96:5878, 1999.
Chicken Litter Soil Amendment Effects on Soilborne Microbes and Meloidogyne incognita on Cotton
Authors: Riegel C. , Noe J. P.
Published: May 2007

The effects of chicken litter incorporated 28, 14, and 0 days before planting on Meloidogyne incognita in cotton and soil organisms were determined in the greenhouse. Treatments consisted of field soil amended with litter at rates of 0, 0.125, 0.25, 0.5, and 1% by weight. At 45 and 90 days after planting, numbers of M. incognita decreased as rates of litter increased. Microbivorous nematode densities increased as litter rates increased only in the first experiment. Plant growth increased as litter rates increased, regardless of when the litter was incorporated, or the presence or absence of M. incognita. Bacterial and fungal CFU fluctuated during both experiments, but generally had positive linear relationships with litter rate. Population densities of M. incognita decreased with increasing bacterial and fungal counts in amended soil. Bacterial genera identified from the litter-amended soil included Arthrobacter, Bacillus, Cellulomonas, Mi-crococcus, Pseudomonas, and Rhodococcus.
Epidemiology and Control of Citrus Greasy Spot in Different Citrus-Growing Areas in Florida
Authors: Timmer L. W. , Roberts P. D. , Darhower H. M. , Bushong P. M. , Stover E. W. , Peever T. L. , Ibáñez A. M.
Published: May 2007

Greasy spot, caused by Mycosphaerella citri, causes defoliation and yield losses on grapefruit in all areas of Florida, but is more severe in southwest Florida and the east coast than in central Florida. The amount of leaf litter, numbers of ascospores produced, and severity of greasy spot on trap plants were monitored throughout 1997 and 1998 in Immokalee (southwest Florida) and Lake Alfred (central Florida). Leaf litter and ascospore production were greatest from March to July in both locations, with little litter and few ascospores thereafter. Ascospore production occurred earlier in Immokalee than in Lake Alfred in both years. Disease on trap plants was moderate to severe throughout the year except from November to February. Large numbers of ascospores produced early in the year when conditions were less favorable resulted in the same disease severity levels as low numbers of ascospores produced later in the year when environmental conditions were favorable. Greater greasy spot severity in southwest Florida, compared with central Florida, is more likely due to higher rainfall and warmer winter temperatures than to differences in time of infection. Single annual copper fungicide applications were made each month from April to August in 1998 and 1999 in LaBelle (southwest Florida), Ft. Pierce (east coast), and Lake Alfred to determine the most effective time of application. Two two-spray treatments, May + July and June + August, were also evaluated in 1999. A single copper fungicide application in June provided the most consistently effective control across all locations. The June + August two-spray treatment was very effective in disease control, but usually no better than a well-timed single application.
New Sources of Resistance to Phytophthora sojae in the Soybean Plant Introductions
Authors: Dorrance A. E. , Schmitthenner A. F.
Published: May 2007

Single dominant Rps genes have been highly effective in managing Phytophthora sojae. However, numerous physiological races of P. sojae have developed in response to deploying single gene resistance. New sources of resistance with potentially novel Rps genes are needed. A selection of accessions (PI273483 to PI427107) from the United States Department of Agriculture Soybean Germplasm collection were evaluated for resistance to P. sojae using the hypocotyl inoculation technique for Rps genes and the layer test for partial resistance. Of the 1,015 accessions tested, 159 accessions were susceptible to races 7 (vir 1a, 2, 3a, 3c, 4, 5, 6, 7), 17 (1b, 1d, 2, 3a, 3b, 3c, 4, 5, 6, 7), and 25 (1a, 1b, 1c, 1k, 7). However, 162 accessions were resistant to these three races and 32 accessions were resistant to an additional five races chosen specifically to elicit a susceptible interaction with two and three Rps gene combinations. In addition, 55.5% of the 887 accessions tested had high levels of partial resistance or tolerance (scores ≤4.0) to P. sojae. The majority of the accessions that were resistant to all of the races tested and those that had very high levels of partial resistance originated in the Republic of Korea. These results indicate that this region is an area with many sources of resistance to P. sojae for both specific Rps genes and partial resistance.
First Report of Lasiodiplodia theobromae as a Foliar Pathogen of Parthenium hysterophorus
Authors: Kumar P. Sreerama , Singh S. P.
Published: May 2007

Parthenium (Parthenium hysterophorus L.) has been a target of weed researchers in India for more than four decades. The weed is attacked by many pathogens, some of which have been tried as mycoherbicides with mixed results (1). In an effort to identify more pathogens of parthenium, surveys were conducted in different regions. A typical foliar disease was frequently observed in several districts of Karnataka State, especially during the winter months of 1996 to 1998. The primary symptoms were circular to irregular, light brown to gray leaf spots, ranging from 2 to 8 mm in diameter. Careful observation of diseased plants revealed that the development of several lesions in close proximity resulted in a rapid necrosis and withering of the entire leaf. The suspected causal organism, which was a dark, chocolate-brown fungus, grew well on potato-dextrose agar at 25°C and a 12-h photoperiod. It produced slowly maturing conidia (20 to 27 × 12 to 14 μm), which were dark brown, ellipsoid, thick-walled, and single-septate with longitudinal striations. A dense conidial suspension (108 conidia per ml) of the fungus was evenly applied (250 μl per leaf) on detached, surface-sterilized, healthy parthenium leaves (N = 10), and infection was ascertained after 4 days of incubation at 26 ± 2°C in petri dishes lined with moist cotton. When 45-day-old pot-grown parthenium plants (N = 50) were similarly inoculated and maintained above 95% RH for at least 48 h, typical symptoms resembling those of naturally infected plants were visible on 88% of the plants within 3 weeks of incubation at 28 ± 2°C. Whereas the fungus was consistently isolated from diseased leaves of inoculated plants, with 80% frequency of reisolation, uninoculated controls neither displayed symptoms nor yielded the pathogen. The experiment was performed three times with similar results, satisfying Koch's postulates. The identity of one of the virulent isolates, WF(Ph)8 (ex Siddeswaranadurga, Chitradurga district, December 1997), was confirmed as Lasiodiplodia theobromae (Pat.) Griffon. & Maubl. (=Botryodiplodia theobromae Pat.) (IMI 378919a) at CABI Bioscience, UK Centre (Egham). Although it is a ubiquitous tropical and subtropical plant pathogen that occurs between 40°N and 40°S (2), it was not previously recorded as a cause of leaf disease on parthenium. Investigations on the possible use of the pathogen as a mycoherbicide have given encouraging results.

References: (1) P. Sreerama Kumar. 1998. Pages 192-210 in: Biological Suppression of Plant Diseases, Phytoparasitic Nematodes and Weeds. S. P. Singh and S. S. Hussaini, eds. Project Directorate of Biological Control, Bangalore, India. (2) B. C. Sutton. 1980. The Coelomycetes. Commonwealth Mycological Institute, Kew, England.
Taxa of Leafhoppers Carrying Phytoplasmas at Sites of Ash Yellows Occurrence in New York State
Authors: Hill G. T. , Sinclair W. A.
Published: May 2007

Leafhopper (Homoptera: Cicadellidae) populations were sampled and leafhopper carriers of ash yellows (AshY) phytoplasmas were identified as first steps toward vector identification. Nearly 5,000 leafhoppers were collected in malaise traps at two sites of high AshY incidence in New York state in 1996 and 1997. These insects comprised 33 taxa, including representatives of 13 genera known to contain phytoplasma vectors. The most abundant genus was Scaphoideus, with numbers about six times greater than any other genus. A total of 1,632 insects were assayed individually for phytoplasmas by polymerase chain reaction (PCR) amplification of phytoplasmal 16S rDNA and restriction fragment length polymorphism analyses of PCR products using restriction enzymes TaqI and RsaI separately. Phytoplasmas were detected in 35 insects, all but one in the subfamily Deltocephalinae. AshY phytoplasmas were detected in 19 of 812 individuals of Scaphoideus spp. and 1 of 87 of Colladonus clitellarius. Phytoplasmas of the Prunus X-disease group were detected in 1 Scaphoideus sp., 4 individuals of C. clitellarius, and 4 of 83 Scaphytopius acutus individuals. Phytoplasmas of the aster yellows group were detected in 1 of 68 individuals of Gyponana spp. and 5 of S. acutus. AshY phytoplasma carriers merit testing for possible vector ability.
Genetic Structure of the Phytophthora infestans Population in Morocco
Authors: Sedegui M. , Carroll R. B. , Morehart A. L. , Evans T. A. , Kim S. H. , Lakhdar R. , Arifi A.
Published: May 2007

ABSRACT

In 1996 to 1998, a late-blight survey was conducted in potato- and tomato-growing regions of Morocco. A total of 149 isolates of Phytophthora infestans were collected and analyzed for the glucose-6-phosphate isomerase (Gpi) and peptidase (Pep) alleles, mating types, and metalaxyl sensitivities. Four genotypes were identified: MO-1 (mating type A1, Gpi 100/100, Pep 92/100), MO-2 (mating type A1, Gpi 86/100, Pep 92/100), MO-3 (mating type A2 Gpi 100/100, Pep 100/100), and MO-4 (mating type A1, Gpi 100/100, Pep 100/100). The potato isolates were MO-1 (1996 & 97), MO-3 (1998), and MO-4 (1998). The frequencies of A1 (MO-4) and A2 (MO-3) mating types in potato fields in 1998 were 26 and 74%, respectively. Potato isolates were pathogenic to both potatoes and tomatoes. The isolates collected from tomatoes in 1997 and 1998 were MO-2. Potato and tomato isolates were insensitive and sensitive to metalaxyl, respectively. The change of genotype population in 1998 was probably caused by migration of a new genotype from Europe associated with importation of potato seed. The detection of A1 and A2 mating types in the same potato field indicates the potential for sexual reproduction of P. infestans in Morocco.
Survival and Growth of Listeria monocytogenes on Fresh-Cut Apple Slices and Its Interaction with Glomerella cingulata and Penicillium expansum
Authors: Conway William S. , Leverentz Britta , Saftner Robert A. , Janisiewicz Wojciech J. , Sams Carl E. , Leblanc Eric
Published: May 2007

The food-borne human pathogen Listeria monocytogenes survived and its populations increased on cv. Delicious apple slices at 10 or 20°C in air or controlled atmosphere of 0.5% O2 and 15% CO2, but did not grow at 5°C. Controlled atmosphere had no significant effect on the survival or growth of L. monocytogenes. The pathogen populations declined over time when grown in various concentrations of apple juice and the decline was greater as the concentration of the juice decreased. Populations of L. monocytogenes inoculated into decayed apple tissue continually increased on fruit decayed by Glomerella cingulata but did not survive after 5 days on fruit decayed by Penicillium expansum. The pH of the decayed area declined from pH 4.7 to 3.7 in the case of P. expansum, but in the case of G. cingulata the pH increased from pH 4.7 to 7.0. This pH modification may be responsible for affecting the growth of the food-borne pathogen. Storage temperature, as well as the absence of postharvest pathogens such as G. cingulata, is important for maintaining the safety of fresh-cut apples.
Reduction of Phytophthora Blight of Madagascar Periwinkle in Florida by Soil Solarization in Autumn
Authors: McGovern R. J. , McSorley R. , Urs R. R.
Published: May 2007

Three field experiments were conducted in southwest and west-central Florida in 1993 through 1995 to evaluate the effectiveness of soil solarization during autumn in reducing Phytophthora blight of Madagascar periwinkle (Catharanthus roseus) caused by Phytophthora nicotianae. Plots (3.6 by 3.6 m) were infested by incorporating winter wheat seed containing P. nicotianae in the upper 15 cm of soil. Solarization was then conducted for 21 to 41 days, primarily during October, using clear, 25- or 50-μm low-density polyethylene mulch. The progress of Phytophthora blight, monitored for 31 to 42 days following planting, was significantly reduced by solarization in all experiments, and final blight incidence was reduced in two of three experiments. Solarization also reduced population densities of P. nicotianae.
First Report of Phytoplasmas in Soybean, Alfalfa, and Lupinus sp. in Lithuania
Authors: Jomantiene R. , Davis R. E. , Antoniuk L. , Staniulis J.
Published: May 2007

Plants of cultivated soybean (Glycine max) and alfalfa (Medicago sativa) in Dotnuva and of wild Lupinus sp. in Ledakalnis, Lithuania, exhibited symptoms that suggested phytoplasmal infections. Soybean plants were of normal growth habit but exhibited veinal necrosis. Alfalfa and Lupinus plants exhibited stunting, abnormally small leaves, and witches'-broom symptoms. Diseases in the plants were termed soybean veinal necrosis (SVN), alfalfa stunt (AlfS), and Lupinus stunt (LupS), respectively. The presence of phytoplasmas in diseased plants was assessed using polymerase chain reaction (PCR) for amplification of phytoplasma-specific 16S rDNA. A phytoplasma-characteristic 1.2-kbp DNA fragment was amplified from all diseased plants but not from known healthy plants in nested PCRs in which the first DNA amplification was primed by primer pair P1/P7 and reamplification of DNA was primed by primer pair F2n/R2 (2,4). Products from the nested PCR primed by F2n/R2 were subjected to restriction fragment length polymorphism (RFLP) analysis, and the RFLP patterns obtained were compared with patterns previously published (1–4). On the basis of AluI, HaeIII, HhaI, HpaI, KpnI, MseI, and RsaI RFLP patterns, the SVN and LupS phytoplasmas were classified in group 16SrIII (peach X-disease phytoplasma group), subgroup B (III-B, type strain clover yellow edge phytoplasma), and the AlfS phytoplasma was classified in group 16SrI (aster yellows phytoplasma group), subgroup B (I-B, type strain aster yellows phytoplasma). Nucleotide sequences were determined for 16S rDNA fragments amplified from SVN and AlfS phytoplasmas in nested PCRs primed by F2n/R2. The sequences were deposited in GenBank under Accession nos. AF177383 for SVN and AF177384 for AlfS. Sequence similarity between the 16S rDNAs of SVN and Canadian clover yellow edge (strain CYE-C, GenBank Accession no. AF175304) phytoplasmas was 99.8%; sequence similarity between 16S rDNAs of AlfS and aster yellows (strain SAY, GenBank Accession no. M86340) phytoplasmas was 99.6%. The SVN phytoplasma 16S rDNA shared 100% sequence similarity with a 16S rDNA from the Lithuanian clover yellow edge (CYE-L, GenBank Accession no. AF173558) phytoplasma. The nucleotide sequence data supported the conclusion that the SVN and AlfS phytoplasmas were closely related to strains classified in subgroups III-B and I-B, respectively. Our findings extend the known geographic ranges of phytoplasma subgroups I-B and III-B to northern Europe, including Lithuania, and expand the known plant host ranges of these pathogens.

References: (1) R. E. Davis et al. Int. J. Syst. Bacteriol. 47:262, 1997. (2) R. Jomantiene et al. Int. J. Syst. Bacteriol. 48:269, 1998. (3) R. Jomantiene et al. HortScience 33:1069, 1998. (4) I.-M. Lee et al. Int. J. Syst. Bacteriol. 48:1153, 1998.
First Report of Race 3 of Fusarium oxysporum f. sp. lycopersici in Southeastern Florida
Authors: Ploetz R. C. , Haynes J. L.
Published: May 2007

Race 3 of Fusarium oxysporum f. sp. lycopersici, cause of Fusarium wilt of tomato, Lycopersicon esculentum, was first recognized in Florida in 1982 on the west coast (Hillsborough and Manatee counties) (2). Approximately 10 years later, race 3 was reported in northeastern production areas of the state (Gadsden County) (1) and was observed on the east coast (Ft. Pierce area) (D. O. Chellemi, personal communication). During the 1998 to 1999 season, mature plants of Sanibel, a commercial tomato cultivar with resistance to races 1 and 2, were observed with symptoms of Fusarium wilt at the University of Florida's Tropical Research and Education Center in Homestead. Approximately 20% of the plants were conspicuously wilted, chlorotic, and necrotic in all or unilateral portions of the canopy. Internal, vascular discoloration in affected plants extended far into the canopy, distinguishing the disease from Fusarium crown rot, caused by F. oxysporum f. sp. radicis-lycopersici. Pure colonies of fungi were isolated from surface-disinfested (10 s with 70% ethanol, 2 min with 10% bleach) stem segments on potato dextrose agar (PDA) amended with streptomycin (100 mg/liter), rifamycin (50 mg/liter), and a commercial miticide (Danitol 2EHC [4 drops/liter]). Isolates were identified as F. oxysporum due to their production of typical falcate macroconidia with foot-shaped basal cells, microconidia borne in false heads only on mono-phialides, and chlamydospores. In replicated (three) greenhouse trials, six single-spore isolates were used to root-dip inoculate (107 conidia per ml) seedlings of differential tomato cultivars (Bonnie Best, no resistance; Manapal, race 1 resistance; Walter, race 1 and race 2 resistance). All isolates were pathogenic on each of the differential cultivars, and one isolate, 2-1, caused severe damage on Walter (mean rating of 3.5 on a 1 to 5 scale). The results were repeated in a second trial with the most virulent isolate. In both trials, pure colonies of F. oxysporum were recovered from symptomatic seedlings. Southeastern Florida is the last major tomatoproduction area in Florida to be affected by race 3 of F. oxysporum f. sp. lycopersici.

References: (1) D. O. Chellemi and H. A. Dankers. Plant Dis. 76:861, 1992. (2) R. B. Volin and J. P. Jones. Proc. Fla. State Hortic. Soc. 95:268, 1982.
First Report of Psittacanthus angustifolius on Pinus oocarpa and Pinus maximinoi
Authors: Mathiasen R. , Melgar J. , Beatty J. , Parks C.
Published: May 2007

The mistletoe Psittacanthus angustifolius Kuijt (Loranthaceae) was first described in 1987 on Pinus from Nicaragua near the Honduran border, but the species of pine was not designated (1). Kuijt (1) speculated that this mistletoe probably also occurs in Honduras. During March and October 1999 we observed P. angustifolius parasitizing Pinus oocarpa Schiede in the departments of Choluteca, Francisco Morazan, El Paraiso, Intibuca, Lempira, and Olancho in Honduras. This mistletoe appears to be a very common parasitic plant on pines in Honduras and is associated with host mortality. We also observed P. angustifolius parasitizing Pinus maximinoi H.E. Moore at two locations in the department of Lempira: one infection on a single tree 1.5 km east of El Matazano (elevation 1,400 m) and six and eight infections on two trees 0.5 km west of the main entrance to Celaque National Park east of Gracias (elevation 1,200 m). This is the first report of P. angustifolius in Honduras and the first report of this mistletoe on Pinus oocarpa and Pinus maximinoi. Specimens of P. angustifolius from Pinus oocarpa and Pinus maximinoi have been deposited at the Herbario, Escuela Nacional de Ciencias Forestales, Siguatepeque, Honduras, and at the Deaver Herbarium, Northern Arizona University, Flagstaff.

Reference: (1) J. Kuijt. Ann. Mo. Bot. Gard. 74:511, 1987.
Race Determination and Vegetative Compatibility Grouping ofFusarium oxysporumf. sp.melonisfrom South Africa
Authors: Schreuder W. , Lamprecht S. C. , Holz G.
Published: May 2007

Isolates of Fusarium oxysporum f. sp. melonis (72 total) obtained from 30 fields in 17 melonproducing regions in South Africa were race typed, using differential cvs. CM 17187, Doublon, Perlita, and Topmark, and grouped on the basis of vegetative compatibility. Fifty-four isolates were identified as race 0, eight as race 1, and ten as race 2. Race 0 occurred in 15 of 17 regions, whereas race 1 was sporadically recovered. Race 2 was obtained from only four fields located in one geographic region. Perlita plants (carrying the gene Fom3) inoculated with local isolates of races 0 and 2 and reference isolates of race 0 became stunted, and their leaves became yellow, thickened, and brittle. Using two inoculation methods, similar symptoms were induced by reference and local isolates of race 0 on Perlita seedlings. The results indicated that Fom3 in Perlita confers a tolerant reaction compared with the resistant reaction of gene Fom1 in Doublon and, therefore, should not be used alone in race determination tests. All isolates belonged to vegetative compatibility group 0134, indicating a high degree of genetic homogeneity among the South African F. oxysporum f. sp. melonis population.
Sources of Resistance to Anthracnose in the Annual Medicago Core Collection
Authors: O'Neill Nichole R. , Bauchan Gary R.
Published: May 2007

The annual genus Medicago core collection, consisting of 201 accessions, represents the genetic diversity inherent in 3,159 accessions from 36 annual Medicago species. This germ plasm was evaluated for resistance to anthracnose caused by Colletotrichum trifolii. Anthracnose is a major disease in perennial alfalfa (Medicago sativa L.) grown in North America and disease control is based principally on the use of resistant varieties. Evaluation of the core collection was conducted using standardized environmental conditions in growth chambers, and included the M. sativa standard reference cvs. Arc (resistant) and Saranac (susceptible). The degree of resistance found among accessions within species was highly variable; however, most annual species and accessions were susceptible. Only 14 accessions from seven species exhibited resistance greater than 40% seedling survival. These included accessions of M. murex, M. muricoleptis, M. polymorpha var. brevispina, M. polymorpha var. polymorpha, M. radiata, M. soleirolii, M. truncatula, and M. turbinata. Of the 12 accessions of M. polymorpha var. polymorpha, 4 exhibited more than 50% resistance, but 3 accessions were 100% susceptible. Most of the M. truncatula and M. turbinata accessions exhibited significantly more resistance than accessions of other species. Plant introduction (PI) accession number PI 495401 of M. muricoleptis exhibited 90.3% resistance. Accessions of M. scutellata were uniformly susceptible. Histological examinations of 14 of the most anthracnose-resistant accessions revealed that C. trifolii spores germinated and produced typical appressoria, but failed to penetrate and produce the primary and secondary hyphae characteristic of susceptible interactions. Resistant reactions were similar to those found in incompatible interactions with C. trifolii and alfalfa, which have been associated with specific genes leading to the production of isoflavonoid phytoalexins. The large genetic variability in annual Medicago spp. offers potential for locating and utilizing disease resistance genes through breeding or genetic engineering that will enhance the utilization of Medicago spp. as a forage crop.
Effect of Botanical Extracts on the Population Density of Fusarium oxysporum in Soil and Control of Fusarium Wilt in the Greenhouse
Authors: Bowers John H. , Locke James C.
Published: May 2007

Several commercial formulations of botanical extracts and essential oils are being investigated as possible alternatives to soil fumigation for control of Fusarium wilt diseases. Soil infested with Fusarium oxysporum f. sp. chrysanthemi was treated with 1, 5, and 10% aqueous emulsions of formulated extracts of clove (70% clove oil), neem (90% neem oil), pepper/mustard (chili pepper extract and essential oil of mustard), cassia (extract of cassia tree), and Banrot (a standard fungicide applied at different labeled rates) in separate experiments. Population densities of F. oxysporum f. sp. chrysanthemi were determined at 0 (before treatment), 1, 3, 7, 14, and 21 days after treatment. Treatment of the soil with 5 and 10% aqueous emulsions resulted in significant (P < 0.05) differences among treatment means at each assay date. After 3 days, pepper/mustard, cassia, and clove extracts added as 10% aqueous emulsions reduced the population density of F. oxysporum f. sp. chrysanthemi 99.9, 96.1, and 97.5%, respectively, compared with the untreated control. Neem oil extract increased the population density of F. oxysporum f. sp. chrysanthemi at all concentrations tested. Banrot did not reduce the population density of F. oxysporum f. sp. chrysanthemi in any experiment. In a second, related experiment, soil infested with Fusarium oxysporum f. sp. melonis also was treated with 1, 5, and 10% aqueous emulsions of formulated extracts, incubated in closed plastic bags for 1 week, and planted with muskmelon seeds (cv. Gold Star) in the greenhouse. Treatment of infested soil with 5 and 10% aqueous emulsions of the botanical extracts resulted in differences among treatments after 5 to 6 weeks. The pepper/mustard, cassia, and clove extracts suppressed disease development in repeated experiments (80 to 100% healthy plant stand) compared with the untreated infested soil (<20% stand). The observed reduction in the pathogen population and increased healthy plant stand in the greenhouse indicates that these extracts could have important roles in biologically based management strategies for control of Fusarium wilt diseases.
Influence of Inoculum Density of Verticillium dahliae on Root Discoloration of Horseradish
Authors: Khan A. , Atibalentja N. , Eastburn D. M.
Published: May 2007

The relationship between inoculum density (number of microsclerotia per gram of air-dried soil) of Verticillium dahliae at the time of planting and the severity and incidence of root discoloration of horseradish at harvest was investigated in a 2-year study conducted in the greenhouse, microplots, and commercial production fields. The objective of the study was to develop a disease-forecast system that would assist growers in assessing the risk of the disease before planting horseradish in a particular field. Significant correlations were observed between inoculum density and severity and incidence of root discoloration in the greenhouse and microplots, although the form of the relationship varied with trials from linear to quadratic and negative exponential. No correlation was found between inoculum density of V. dahliae and severity and incidence of root discoloration in commercial production fields. In some fields with low inoculum densities, high ratings of severity and incidence of root discoloration were observed even with the partially resistant cultivar 769A. Conversely, in other fields with high inoculum densities, low ratings of severity and incidence of discolored roots were observed even with the susceptible cultivar 647A. These results suggest that a disease-forecast system based solely on inoculum densities of V. dahliae would be unreliable under field conditions when the other factors affecting the inoculum density-disease relationships cannot be controlled. Knowing the amount of initial inoculum may, however, save growers from planting horseradish in highly infested fields, but it would not guarantee a disease-free crop in fields with low levels of infestation.
Rice Pest Constraints in Tropical Asia: Characterization of Injury Profiles in Relation to Production Situations
Authors: Savary Serge , Willocquet Laetitia , Elazegui Francisco A. , Teng Paul S. , Van Du Pham , Zhu Defeng , Tang Qiyi , Huang Shiwen , Lin Xianquing , Singh H. M. , Srivastava R. K.
Published: May 2007

A protocol for characterizing patterns of rice cropping practices and injuries due to pathogens, insects, and weeds was developed and used in six sites in tropical Asia covering a wide range of environments where lowland rice is cultivated. The data collected in a total population of 456 individual farmers' fields were combined to site-specific weather data and analyzed using non-parametric multivariate techniques: cluster analyses with chi-square distance and correspondence analyses. The main results are: (i) patterns of cropping practices that are common across sites can be identified; (ii) conversely, injury profiles that are common across sites can be determined; (iii) patterns of cropping practices and injury profiles are strongly associated at the regional scale; (iv) weather patterns are strongly associated with patterns of cropping practices and injury profiles; (v) patterns of cropping practices and injury profiles allow for a good description of the variation in actual yield; and (vi) patterns of cropping practices and injury profiles provide a framework that accurately reflects weather variation and site diversity, and reliably accounts for variation in yield. The mean estimated yield across sites (4.12 t ha-1) corresponds to commonly cited averages in the region and indicates the potential for increased productivity with better management practices, especially an improved water supply. Injuries due to pests are secondary compared with other yield-limiting factors. Injury profiles were dominated by stem rot and sheath blight (IN1); bacterial leaf blight, plant hoppers, and leaf folder (IN2); and sheath rot, brown spot, leaf blast, and neck blast (IN3). IN1 was associated with high (mineral) fertilizer inputs, long fallow periods, low pesticide use, and good water management in (mostly) transplanted rice crops of a rice-rice rotation. IN2 was associated with direct-seeded rice crops in an intensive rice-rice rotation, where fertilizer and pesticide inputs are low and water management is poor, or where fertilizer and pesticide inputs are high and water management is adequate. IN3 corresponds to low input, labor intensive (hand weeding and transplanting) rice crops in a diverse rotation system with uncertain water supply. Weed infestation was an omnipresent constraint. This study shows the potential for developing pest management strategies that can be adapted throughout the region, rather than being site-specific.
Outbreak of Tomato yellow leaf curl virus (Family Geminiviridae) in Georgia
Authors: Pappu S. S. , Pappu H. R. , Langston D. B. , Flanders J. T. , Riley D. G. , Diaz-Perez J. C.
Published: May 2007

Tomato yellow leaf curl virus (TYLCV) of the family Geminiviridae is a serious production constraint to tomato (3). In the southeastern United States the virus has been largely confined to Florida. The disease appeared in the southern most Georgia county (Decatur) in 1998, at an incidence rate of less than 1% (2). During the fall of 1999, tomato plants showing symptoms indicative of TYLCV were observed in commercial fields in Grady, Colquitt, and Lowndes counties and the experimental plots of the Coastal Plain Experiment Station in two locations in Tift County, GA. The 12-acre commercial field in Grady County had a disease incidence of 15%. In Tift County, in both experimental plots (≈5 miles apart), TYLCV incidence ranged from 15 to 20%. Bemisia argentifolii populations in southern Georgia, based on the observed high incidence of silverleaf symptoms in squash and the intensity of adult migrations during August and September, were the highest in more than 5 years. TYLCV infection was verified by polymerase chain reaction (PCR) amplification with degenerate primers (5′-GCC CAC ATY GTC TTY CCN GT-3′ and 5′ -GGC TTY CTR TAC ATR GG-3′) specific to the DNA A component (4). A simplified and faster DNA extraction procedure was used to obtain PCR-ready templates. Leaf tissue was homogenized in 300 μl of extraction buffer (1), followed by one phenol and one chloroform/ isoamyl alcohol (24:1) extraction. The supernatant was purified using a QiaPrep MiniPrep purification kit (Qiagen, Valencia, CA) and was used in PCR amplification. The procedure yielded highly consistent PCR-quality template. The resulting ≈1.3-kb PCR product was cloned in pGEM-T vector (Promega Corp., Madison, WI) and completely sequenced. Sequence comparisons indicated 98% identity with known TYLCV isolates from Spain (GenBank Accession no. AJ223505), the Dominican Republic (GenBank Accession no. AF024715), and Israel (GenBank Accession no. X15656). Using PCR followed by restriction digestion analysis, three symptomatic plants from one field each in Colquitt and Lowndes counties were TYLCV positive. The higher incidence of TYLCV in the Georgia counties of Tift and Grady and its concurrent occurrence in Colquitt and Lowndes counties indicates its rapid spread in the southeastern United States.

References:(1) I. B. Dry et al. J. Gen. Virol. 74:147, 1993. (2) M. T. Momol et al. Plant Dis. 83:487, 1999. (3) J. E. Polston et al. Plant Dis. 83:984, 1999. (4) M. R. Rojas et al. Plant Dis. 77:340, 1993.
First Report of Zucchini yellow mosaic virus in Argentina
Authors: Gracia O.
Published: May 2007

In August 1996, a severe viral disease occurred in squash produced in the subtropical Province of Salta, Argentina. Plants of Cucurbita pepo L. (zucchini) and Cucurbita maxima L. ‘Any’ were affected. Approximately 50% of the plants showed prominent yellow mosaic, necrosis, and foliar distortion. Most of the fruits on infected plants were small, with scattered glossy yellow knobs over a green background, and some showed additional fruit malformation. A potyvirus was isolated from infected plants by mechanical transmission. Filamentous particles were associated with symptomatic inoculated squash and cucumber plants in leaf-dip preparations with an electron microscope (Elmisckop I, Siemens, Germany). The particles were flexuous rods ≈755 nm long. The host range of the isolated virus was mostly limited to the cucurbits (systemic infection) but also included Gomphrena globosa (local and systemic symptoms) and Chenopodium quinoa and Chenopodium amaranticolor, which showed only local chlorotic lesions. Twenty species in the Compositae, Leguminosae, and Solanaceae were not infected (2). In agar double-diffusion tests with sodium dodecyl sulfate (SDS)-degraded virus particles, no reactions were observed with Papaya ringspot virus, Watermelon mosaic virus (WMV), and WMV-Mo antisera, but a strong precipitin line was obtained with the antiserum prepared by Purcifull (1) for isolate 1119 of Zucchini yellow mosaic virus (ZYMV). Isolate 1119 and our isolate appeared serologically indistinguishable in SDS immunodiffusion tests. Both gave fused precipitin bands without spur formation. The results (field symptoms, transmissibility, host range, particle morphology, and serology) lead to the conclusion that ZYMV is present in Argentina. Since 1996, outbreaks have occurred every year in Salta, devastating squash crops. In 1998, ZYMV also was found in the provinces of Mendoza and San Juan, infecting zucchini squash and melons (Cucumis melo L.). A survey of crops indicates that disease incidence and severity were lower than in Salta.

References: (1) D. E. Purcifull et al. Plant Dis. 68:230, 1984. (2) H. L. Wang. Plant Dis. 76:530, 1992.
First Report of Alternaria alternata as a Dieback Pathogen of Kiwifruit
Authors: Tsahouridou P. C. , Thanassoulopoulos C. C.
Published: May 2007

During a survey of diseases on kiwifruit (Actinidia chinensis) cv. Hayward during spring 1998 in Northern Greece, leaves of kiwifruit trees were found covered with small, necrotic brown spots. Intense spotting was associated with defoliation. Furthermore, small, sunken, dark brown cankers appeared a few centimeters below the twig tip, and twigs died distal to the canker a few days later, while the twig remained healthy below the canker, often producing a new shoot below the canker. Isolations from symptomatic leaves and internal tissues of twigs on potato dextrose agar (PDA), after surface-sterilization with 0.5% NaOCl and 90% alcohol, respectively, consistently yielded a fungus that, based on conidial morphological characteristics, was identified as Alternaria alternata (Nees:Fr.) Keissl. (2). Pathogenicity tests were performed on 3-year-old kiwi plants. Tests on twigs were conducted by inoculating 35 twigs with 5-mm disks from 7-day-old cultures on PDA at 25°C. Each twig was inoculated with three disks. Tests on leaves were conducted by spraying a conidial suspension (5 × 106 conidia per ml) of the cultures on leaves. Plants were kept in a glasshouse at 22 to 25°C. Symptoms, identical to those observed in the field, developed on leaves and twigs 6 and 18 days, respectively, after inoculation. All inoculated leaves exhibited symptoms of the disease, whereas more than 95% of inoculated twigs exhibited disease symptoms. A. alternata was consistently reisolated from inoculated tissues. A. alternata is widely known to be a leaf spot pathogen of kiwifruit (1). This is the first report of A. alternata causing twig dieback.

References: (1) L. Corazza and L. Luongo. Plant Dis. 83:487, 1999. (2) E. G. Simmons. Mycotaxon 37:79, 1990.
First Report of Hemp Canker Caused by Sclerotinia sclerotiorum in Alberta, Canada
Authors: Bains P. S. , Bennypaul H. S. , Blade S. F. , Weeks C.
Published: May 2007

Hemp (Cannabis sativa L.) is a herbaceous annual grown mainly for its blast fiber and seed oil. In 1999, Health Canada issued licenses to plant 12,145 ha of hemp in Canada. Of these, 730 ha were in Alberta. During the last week of August, hemp plants (cv. Fasamo) in a central Alberta field showed the following symptoms and signs: wilting foliage turning light brown; dry tan to gray lesions on stems; shredding and breaking of stems at the lesion; presence of white mycelium in the lesion; and black round, irregular, or oblong sclerotia (up to 5 mm diameter and 2 to 11 mm long) present externally at the lesion on the stem and inside the pith cavity. Lesions were found at the crown, near the inflorescence, and along the entire stem length. Disease incidence in a survey of six commercial fields (40 ha) ranged from 1 to 8%. The organism isolated from lesions on potato dextrose agar produced white aerial mycelia and large numbers of sclerotia characteristic of Sclerotinia sclerotiorum. Pathogenicity was confirmed by inoculating 23-day-old greenhouse-grown hemp plants (cv. Fasamo) with autoclaved wheat grains colonized for 14 days with a S. sclerotiorum culture previously isolated from an infected hemp plant. The grains were placed on soilless growing medium near the plant and covered very lightly. One week after inoculation, grayish lesions appeared on the stems, white mycelia appeared on lesions, and plants wilted. The pathogen was reisolated from the lesions. This is the first report of S. sclerotiorum on hemp in Alberta, Canada. The disease known as hemp canker has been reported to cause severe losses under cool wet conditions in the Netherlands (1).

Reference: (1) J. M. McPartland. J. Int. Hemp Assoc. 3:19, 1996.
Potato Late-Blight Management in the Toluca Valley: Forecasts and Resistant Cultivars
Authors: Grünwald Niklaus J. , Rubio-Covarrubias Oswaldo A. , Fry William E.
Published: May 2007

We evaluated host resistance and fungicide forecasting as components of integrated management in the Toluca Valley of central Mexico. Potato cvs. Rosita and Norteña showed high levels of resistance (20 and 4% final disease severity, respectively) in the no-spray controls, whereas susceptible cv. Alpha was at 90% defoliation well before the end of the season. Disease on Alpha was well managed with a weekly spray of chlorothalonil. None of three published forecast systems was entirely appropriate for this pathosystem. SIM-CAST accurately allocated fungicide for a susceptible cultivar but needs to be adapted for the high level of resistance of Rosita and Norteña. TOM-CAST and BLITECAST did not recommend the initial fungicide application until after disease was well established in the plots. We believe that the low-temperature response of Phytophthora infestans needs to be reevaluated for the highland tropics.
Fimbrial-Specific Monoclonal Antibody-Based ELISA for European Potato Strains of Erwinia chrysanthemi and Comparison to PCR
Authors: Singh U. , Trevors C. M. , De Boer S. H. , Janse J. D.
Published: May 2007

A murine hybridoma cell line, named 6A6, was developed to produce monoclonal antibodies for serological detection of European potato strains of Erwinia chrysanthemi. The monoclonal antibodies were of the immunoglobulin G2b type and were shown to react with a fimbrial antigen by immuno-gold electron microscopy, and with the fibrillin protein by Western blotting. In enzyme-linked immunosorbent assay (ELISA), the monoclonal antibody reacted with all but two strains of E. chrysanthemi isolated from potato. One non-reactive strain originated from Australia and therefore was likely a different biovar, and the other strain was of unknown origin. The monoclonal antibody also reacted with 20 out of 36 strains of E. chrysanthemi isolated from hosts other than potato. A triple-antibody ELISA test utilizing monoclonal antibody 6A6 successfully detected E. chrysanthemi in infected potato stems and tubers but sensitivity was limited to about 107 CFU/ml, compared to a sensitivity of 103 CFU/ml for a polymerase chain reaction test using published primers directed to the pectate lyase gene.