bluuebunny/crossref_metadata_2025 huggingface dataset:
First Report of Sclerotinia sclerotiorum on Common Ragweed (Ambrosia artemisiifolia) in Europe
Authors: Bohár Gy. , Kiss L.
Published: May 2007

Common ragweed (Ambrosia artemisiifolia L.) is reported as a host of Sclerotinia sclerotiorum (Lib.) de Bary in North America (2,4), but not in Europe. A Hungarian survey of fungal diseases of ragweed in 1994 did not find sclerotinia rot of common ragweed (A. artemisiifolia var. elatior (L.) Descourt.) (1). In autumn 1998, mature ragweed plants, 1 to 1.5 m tall, were collected from the borders of four sunflower (Helianthus annuus L.) fields in which sclerotinia rot of sunflower was frequently observed during the season, and also from six other roadside sites in Hungary. Ragweed plants exhibiting symptoms characteristic of sclerotinia rot, i.e., wilting foliage and light brown, dry lesions on the stems, were found only near two sunflower fields. Black, round to irregular or oblong sclerotia were also observed on the infected ragweed plants both externally on the stem lesions and internally, in the pith cavity. Sclerotia measured up to 5 mm in diameter and were 5 to 14 mm long. After isolation on potato dextrose agar, the pathogen produced abundant aerial mycelium and large sclerotia characteristic of S. sclerotiorum. To confirm pathogenicity, potted seedlings and mature plants of ragweed were inoculated in the greenhouse with autoclaved wheat grains colonized with mycelia of S. sclerotiorum placed 0.5 to 1 cm from the collar of the test plants. Seedlings were killed in 2 to 3 days while mature plants wilted after 5 to 6 days. In a field test, six mature plants were inoculated by attaching mycelial disks to their stems with Parafilm. These plants wilted 12 to 14 days after inoculation. The pathogen was reisolated from all diseased plants. This is the first report of S. sclerotiorum on common ragweed in Europe. Nonsclerotial mutants of the fungus (3) are being produced to be tested as potential biocontrol agents of common ragweed, which has become not only the most widespread, but also the most important allergenic plant species in Hungary since the early 1990s.

References: (1) Gy. Bohár and L. Vajna. Nōvényvédelem 32:527, 1996. (2) G. J. Boland and R. Hall. Can. J. Plant Pathol. 16:93, 1994. (3) G. J. Boland and E. A. Smith. Phytopathology 81:766, 1991.(4) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN.
Lisianthus Crown and Stem Rot Caused by Fusarium avenaceum in Central Italy
Authors: Pecchia S.
Published: May 2007

Lisianthus (Eustoma russelianum, syn. E. grandiflorum), a member of the Gentian family, is grown in the greenhouse in Italy as a commercial cut-flower crop. Its cultivation is a relatively new industry with high economic potential. However, disease problems have been observed on various greenhouse-planted lisianthus in Central Italy (Tuscany): symptoms of wilting, tan leaf flecks, tan stem discoloration, crown and stem rot, and death. White mycelia and orange sporodochia were also commonly observed on diseased crowns and stems. Fusarium avenaceum isolates were recovered from diseased tissues. Four single-spore isolates were selected for artificial inoculation. Pathogenicity tests were conducted in the greenhouse on 16- to 17-week-old E. russelianum plants, cvs. Mariacki, Echo, and Heidi, by placing a colonized agar plug, or drops of a conidial suspension, at the crown previously wounded with a sterile scalpel. Moist cotton was fastened to the wound site. Control plants were inoculated with sterile agar plugs or drops of sterile, distilled water. Five plants per cultivar and per treatment were used for each isolate. All plants developed typical disease symptoms within 1 or 2 weeks when inoculated with mycelial plugs or conidial suspensions, respectively. Control plants developed no symptoms. Koch's postulates were completed by consistently reisolating the pathogen from inoculated plants. This is the first report of F. avenaceum on lisianthus in Italy and is similar to reports of the disease in California and Florida (1,2).

References: (1) S. T. Koike et al. Plant Dis. 80:1429, 1996. (2) R. J. McGovern et al. Phytopathology 87:S64, 1997.
Powdery Mildew of Spearmint Caused by Erysiphe orontii in California
Authors: Koike S. T. , Saenz G. S.
Published: May 2007

In 1997 and 1998, the white fungal growth of a powdery mildew was observed on leaves and stems of both nursery and landscape spearmint (Mentha spicata) growing in coastal California (Monterey County). Mycelia were conspicuous, amphigenous, and epiphytic with indistinct to nipple-shaped appressoria. Conidiophore foot cells were cylindrical, straight, nonconstricted at the base, 61 to 92 μm × 11 to 14 μm in size, and were followed by 1 to 3 cells. Doliiform conidia, which were borne in chains of at least 3 to 5 conidia, measured 28 to 33 μm × 17 to 22 μm. Catenate conidia had sinuate edge lines. Conidia lacked fibrosin bodies. Upon germination, conidia produced germ tubes that were mostly apically inserted and ended in club-shaped appressoria, which fit Braun's Cichoracearum-type of conidial germination (1). Cleistothecia were not observed. Based on these features, the pathogen was identified as Erysiphe orontii Cast. (1). Pathogenicity was demonstrated by gently pressing diseased leaves onto leaves of potted spearmint, incubating plants in a humidity chamber for 48 h, then maintaining plants in a greenhouse. The powdery mildew that later developed was morphologically identical to the original isolates. While powdery mildew on spearmint has been observed previously in the state, this is the first report of the disease and first characterization of the pathogen for California.

Reference: (1) U. Braun. Beih. Nova Hedwigia 89:1, 1987.
First Report of Blossom Blight of Strawberry Caused by Xanthomonas fragariae and Cladosporium cladosporioides in California
Authors: Gubler W. D. , Feliciano A. J. , Bordas A. C. , Civerolo E. C. , Melvin J. A. , Welch N. C.
Published: May 2007

In the spring of 1996, severe blossom blight occurred in some strawberry fruit production fields in the Watsonville area. The symptoms, in addition to blighting of entire flowers, were as follows: on the lower surface of the calyx, watersoaked lesions that appeared dark green under reflected light and translucent under transmitted light; necrotic calyces of seemingly healthy green and ripe fruits; watersoaking of the base of the calyx that extended into the pedicel; green-gray sporulation on dead anthers; and presence of flower clusters with small and irregularly shaped fruits. Yellow bacterial colonies were consistently isolated from water-soaked and necrotic lesions on calyces and pedicels. These colonies were entire, circular, raised, glistening, mucoid, and slow growing, characteristics typical of Xanthomonas fragariae on nutrient agar-glucose-yeast extract medium. The bacterial isolate was also identified by rep-polymerase chain reaction as X. fragariae. In addition to the yellow bacteria, a fungus was also frequently isolated from infected anthers, sepals, petals, and pistils, and was identified as Cladosporium cladosporioides. On potato dextrose agar, the fungus had velvetlike colonies colored olivaceous-green to olivaceous-brown, apically and laterally branched conidiophores, and lemon-shaped conidia that were usually smooth but sometimes textured. Blossoms of greenhouse-grown strawberry plants cv. Selva were inoculated with either or both organisms. Blossoms inoculated with X. fragariae developed symptoms distinct from those inoculated with C. cladosporioides. The most prominent visible symptoms caused by X. fragariae were watersoaked lesions on calyces that later became necrotic, watersoaking of the calyx that extended into the pedicel, and blighting of flowers and developing fruits as a result of girdling of the pedicel. Infection by C. cladosporioides was characterized by necrosis of flower parts or the entire flower, presence of green-gray sporulation on dead anthers, and production of small and malformed or misshapen fruits. Inoculation with both organisms produced all the symptoms described above in different flowers of a plant. Infection with both organisms aggravated disease severity, but each organism was capable of inducing blossom blight independently. Both organisms were reisolated from artificially inoculated strawberry flowers, fulfilling Koch's postulate for proof of pathogenicity. This is the first report of the two organisms causing blossom blight of strawberry in California. This is also the first report that C. cladosporioides is a pathogen of strawberry.
Pear Blister Canker Viroid: Host Range and Improved Bioassay with Two New Pear Indicators, Fieud 37 and Fieud 110
Authors: Desvignes J. C. , Cornaggia D. , Grasseau N. , Ambrós S. , Flores R.
Published: May 2007

An investigation was conducted to improve the biological detection of pear blister canker viroid (PBCVd), which over a period of 2 to 3 years induces pear blister canker disease on the perry pear (Pyrus communis) cv. A20. PBCVd was not detected by dot blot hybridization or bioassay in any of the tested species of Amelanchier, Aronia, Cotoneaster, Crataegus, and Pyracantha. However, some species of Chaenomeles, Cydonia, and Sorbus, five out of 13 species of Malus, 15 Pyrus species, and 16 commercial pear cultivars were susceptible to PBCVd, although none developed symptoms. Only in perry pear seedlings did approximately 5% of the population react to infection with pure PBCVd strains by developing petiole, leaf, or bark necrosis 2 to 3 years (cv. A20) or 3 to 5 months (cv. Fieudière) after inoculation. The selected Fieud 37 and Fieud 110 clones are proposed as PBCVd indicators to replace A20. Results from bioassays on the indicators and from detection by a PBCVd-cRNA probe were essentially in agreement except for some Malus species.
Potential for Dispersal of Fusarium oxysporum f. sp. erythroxyli by Infested Seed
Authors: Gracia-Garza J. A. , Fravel D. R. , Nelson A. J. , Elias K. S. , Bailey B. A. , Gardini E. Arévalo , Darlington L. C.
Published: May 2007

Fusarium oxysporum f. sp. erythroxyli causes a vascular wilt of the narcotic plant coca (Erythroxylum coca var. coca). To determine whether this pathogen can be transmitted by infested seed, fruit from symptomatic and asymptomatic plants was collected from different coca-growing areas in Peru and from an experimental field site in Hawaii. A total of 202 fruit from Peru and 69 fruit from Hawaii were surface-disinfested and separated into five parts: pedicel, pericarp, seed coat, endosperm, and cotyledons. After the pedicel and pericarp were removed from the seed coat, the seed was surface disinfested again. Each fruit part was plated separately. Both F. oxysporum and F. moniliforme were recovered from fruit collected in Peru. Both species were isolated from all parts of some fruit. F. oxysporum was isolated from 33% of the fruit plated and most (35%) of these isolates were obtained from the seed coat. Slightly greater numbers of isolates (57%) were recovered from asymptomatic plants than from symptomatic plants (43%). Only F. oxysporum was isolated from fruit collected in Hawaii. Most of these isolates (59%) were from the pedicels of fruit collected from symptomatic plants. Out of 91 isolates of F. oxysporum, 21 were pathogenic to coca seedlings in a bioassay. Six of these pathogenic isolates were originally from the pedicel of the fruit, eight from the pericarp, four from the seed coat, and three from the endosperm. No isolates from the cotyledons were pathogenic. Most of the pathogenic isolates (76%) were from symptomatic plants. The pathogenic isolates were characterized using random amplified polymorphic DNA analysis and vegetative compatibility groups. Based on these analyses, two different subpopulations of the forma specialis erythroxyli were found in Peru, whereas only one was present in Hawaii. These data indicate that infested seed may contribute significantly to dissemination of this pathogen because seed is collected by growers and planted fresh or fermented briefly before planting.
Screening for Late Blight Susceptibility in Potato Tubers by Digital Analysis of Cut Tuber Surfaces
Authors: Niemira Brendan A. , Kirk William W. , Stein Jeffrey M.
Published: May 2007

A method for quantification of late blight (Phytophthora infestans) in potato tuber tissue using a digital scanner and image analysis software is presented. The average reflective intensity of light reflected from the cut surface of sample tubers measures the darkened, diseased potato tuber tissue amid lighter, late blight-free tissue. In the absence of disease, potato variety, tuber shape, and tuber size do not influence the scan results. While digital quantification of late blight in tubers under controlled inoculation conditions is consistent, the digital assessments of late blight did not correspond exactly with those from a conventional subjective visual method. Used together, the methods can provide complementary information regarding varietal susceptibility to P. infestans development on the tuber surface and internal tuber tissue. The method of image analysis presented may be used to determine susceptibility of potato tubers to late blight in varietal development programs, storage research programs, or other tuber research programs.
A Novel Geminivirus of Ipomoea indica (Convolvulacae) from Southern Spain
Authors: Banks G. K. , Bedford I. D. , Beitia F. J. , Rodriguez-Cerezo E. , Markham P. G.
Published: May 2007

A cutting of Ipomoea indica displaying yellow vein symptoms was collected from Nerja in southern Spain in 1995, rooted, and maintained by vegetative propagation under glasshouse conditions at the John Innes Centre, Norwich. Although this member of the Convolvulaceae is native to the New World, it has escaped from cultivation as an ornamental and has now been naturalized in many tropical and warm temperate regions of the world, such as southern Spain. The same plant was found to host a population of whiteflies that were also brought back to containment facilities, and maintained in colony. Total plant DNA was extracted from the I. indica plant and universal primers for begomovirus A component (1) were used to amplify an approximately 2.8-kb fragment that was cloned and sequenced. The sequence is available in the DDJB, EMBL, and GenBank nucleotide sequence data bases under accession number AJ132548. A GENEMBL search with the complete sequence of the clone showed 70.8% identity to the AC1 gene of Ageratum yellow vein virus (AYVV). A search with the coat protein gene sequence showed highest homology to tomato leaf curl virus from southern India, another monopartite virus. Typical geminivirus vein yellowing symptoms, nucleotide sequence similarity, and EM detection of geminate virus particles strongly suggest that a geminivirus is present in this plant. The low level of homology to other sequenced geminiviruses suggests that it is an uncharacterized Begomovirus sp. With degenerate DNA-B primers (2), no B component has so far been detected. This virus is provisionally named Ipomoea yellow vein virus (IYVV). With techniques already established for identifying Bemisia spp. (3), the whiteflies collected with this Ipomoea plant were confirmed as Bemisia tabaci. Transmission studies to healthy I. indica showed that this whitefly population (named biotype S), the Q biotype from Spain, and the B biotype from Israel were all unable to transmit IYVV to healthy I. indica, tobacco, tomato, or nightshade. This may be due to many years of vegetative propagation of the host plant as an ornamental, resulting in loss of virus transmissibility by insects, which has occurred with Abutilon mosaic virus (AbMV) and honeysuckle yellow vein mosaic virus (HYVMV). This is the first report of a novel geminivirus on I. indica. It highlights the importance of weeds as hosts and potential reservoirs of both viruses and pests. We acknowledge support from the British Council, The Royal Society, BBSRC, and MAFF.

References: (1) R.W. Briddon and P. G. Markham. Mol. Biotechnol. 1:202, 1994. (2) M. R. Rojas et al. Plant Dis. 77:340, 1993. (3) R. C. Rosell et al. Ann. Entomol. Soc. Am. 90:575, 1997.
First Report of Aster Yellows Phytoplasma in Alfalfa
Authors: Peters R. D. , Lee M. E. , Grau C. R. , Driscoll S. J. , Winberg R. M. , Kurtzweil N. C. , Lukaesko L. A. , Lee I.-M.
Published: May 2007

Samples of alfalfa (Medicago sativa L.) leaves and stems showing symptoms of inter-veinal chlorosis and purpling, commonly associated with insect feeding, were collected from 8 sites in central and southern Wisconsin in autumn of 1998. Samples were frozen within 24 h of collection. Approximately 0.3 g of plant tissue from each sample was used for total DNA extraction according to the protocol of Zhang et al. (4), with minor modifications in grinding procedures and reagent volumes to optimize results. Nested polymerase chain reaction (PCR) was carried out by amplification of 16S rDNA with the universal primer pairs R16mF2/R16mR1 followed by R16F2n/R16R2 as described by Gunder-sen and Lee (1). Undiluted total sample DNA was used for the first amplification; PCR products were diluted (1:30) in sterile water prior to final amplification. Alfalfa DNA and sterile water were used as negative controls; DNA from phytoplasma causing X-disease in peach (CX) served as a positive control. Fragments of 16S rDNA from putative phytoplasmas amplified by PCR with the primer pair R16F2n/R16R2 were characterized by restriction endonuclease digestion (3). The resulting restriction fragment length polymorphism (RFLP) patterns were compared with patterns for known phytoplasmas described by Lee et al. (3). Products of nested PCR were also purified and sequenced with primers R16F2n/R16R2 and an automated DNA sequencer (ABI 377XL; C. Nicolet, Biotechnology Center, University of Wisconsin-Madison). Of 51 samples of alfalfa assessed, one sample from Evansville, WI, yielded a nested PCR product of the appropriate size (1.2 kb), indicating the presence of phytoplasma. Digestion of this product with various restriction enzymes produced RFLP patterns that were identical to those for phytoplasmas in the aster yellows phytoplasma subgroup 16SrI-A (3). Alignment of the DNA sequence of the nested PCR product from the positive sample with sequences found in the GenBank sequence data base (National Center for Biotechnology Information, Bethesda, MD) with the BLAST sequence similarity function confirmed this result. Although other phytoplasma strains (particularly those causing witches'-broom) have been reported to infect alfalfa (2), this is the first report of the presence of the aster yellows phytoplasma in the alfalfa crop. Vectors involved in transmission and the potential agronomic impacts of aster yellows phytoplasma in alfalfa are topics of current investigation.

References: (1) D. E. Gundersen and I.-M. Lee. Phytopathol. Mediterr. 35:144, 1996. (2) A.-H. Khadhair et al. Microbiol. Res. 152:269, 1997. (3) I.-M. Lee et al. Int. J. Syst. Bacteriol. 48:1153, 1998. (4) Y.-P. Zhang et al. J. Virol. Methods 71:45, 1998.
Epidemiology ofBotrytis cinereain Sweet Basil and Implications for Disease Management
Authors: Sharabani G. , Shtienberg D. , Elad Y. , Dinoor A.
Published: May 2007

Sweet basil (Ocimum basilicum) is a herbaceous annual plant that is highly susceptible to gray mold, caused by Botrytis cinerea. Infections are initiated on the surface of stem wounds that are caused during harvest; the pathogen then progresses on the stem, killing leaves and secondary buds. When the infection reaches the main stem, the entire plant dies. A study of the epidemiology of the disease and of host-pathogen interactions led to the development of rules for effective disease management. The research was conducted in three steps. (i) Natural epidemics in commercial crops were monitored during the 1993 to 1994 and 1994 to 1995 growing seasons. Disease outbreaks were found to coincide with harvests during rainy days, whereas disease intensity did not change much when harvests were completed during rainless days. (ii) Studies under controlled environmental conditions revealed that cut ends of stems were highly susceptible soon after harvest, susceptibility diminished gradually, and stem cuts inoculated 48 h after harvest were rarely diseased. Observations under a scanning electron microscope showed that an opaque layer had appeared over the cut surface and, as the entire wound surface became covered, penetration of the fungus into the tissue was prevented. Based on these findings, it was hypothesized that avoidance of harvesting during rain events and application of one fungicidal spray, soon after harvest, would result in adequate disease suppression. (iii) These hypotheses were tested and corroborated in greenhouses in two experiments, in 1994 to 1995 and 1995 to 1996. Management of basil crops according to these concepts would also lower the risks for contamination of the marketable product with pesticide residues.
Resistance to Benzimidazole and Dicarboximide Fungicides in Greenhouse Isolates of Botrytis cinerea
Authors: Yourman L. F. , Jeffers S. N.
Published: May 2007

In 1996 and 1997, 325 isolates of Botrytis cinerea were collected from 35 commercial greenhouses growing ornamental crops in South Carolina to determine the incidence of resistance to benzimidazole and dicarboximide fungicides. Conidium germination was assessed on a defined agar medium amended with either thiophanate-methyl (a benzimidazole) or vinclozolin (a di-carboximide). A total of 53 representative isolates were evaluated further for conidium germination and mycelium growth on fungicide-amended medium and for infection of geranium seedlings treated with thiophanate-methyl or vinclozolin at label rates. Isolates were considered sensitive to thiophanate-methyl or vinclozolin when the effective concentration of the fungicide active ingredient resulting in 50% inhibition of germination (EC50-germ) was ≤5 μg/ml or when the effective concentration of fungicide active ingredient resulting in 50% inhibition of mycelium growth (EC50-growth) was ≤1 μg/ml. Of all isolates, 81% (262/325) were resistant to thiophanate-methyl and 69% (223/325) were resistant to vinclozolin. Four phenotypes were observed: sensitive to both fungicides (17%), resistant to both fungicides (67%), resistant only to thiophanate-methyl (14%), and resistant only to vinclozolin (2%). Isolates resistant to at least one fungicide were found in 33 of the 35 locations from which samples were taken. Disease incidences on geranium seedlings treated with 600 μg/ml of thiophanate-methyl and then inoculated with isolates sensitive and resistant to this fungicide were 1.4 and 96.1%, respectively. Disease incidences on geranium seedlings treated with 600 μg/ml of vinclozolin and then inoculated with isolates sensitive and resistant to this fungicide were 0.3 and 91.9%, respectively. With thiophanate-methyl, correlation coefficients (r) between disease incidence and log EC50-germ or log EC50-growth were 0.987 and 0.992, respectively. With vinclozolin, correlation coefficients between disease incidence and log EC50-germ and log EC50-growth were 0.975 and 0.893, respectively. Correlation coefficients between the two EC50 values for thiophanate-methyl were 0.989 and for vinclozolin were 0.900. Isolates sensitive to thiophanate-methyl had a mean EC50-germ value of 0.93 μg/ml and a EC50-growth value of 0.11 μg/ml. For isolates sensitive to vinclozolin the mean EC50-germ value was 1.63 μg/ml and the mean EC50-growth value was 0.26 μg/ml. Thiophanate-methyl-resistant isolates had mean EC50-germ and EC50-growth values greater than 500 μg/ml while vinclozolin-resistant isolates had a mean EC50-germ value greater than 500 μg/ml and a mean EC50-growth value of 3.18 μg/ml.
First Report of Fusarium Wilt Disease of Mimosa in Greece
Authors: Skarmoutsou H. , Skarmoutsos G.
Published: May 2007

Mimosa, Albizia julibrissin, is an ornamental tree that thrives in Greece under difficult urban environmental conditions and is prized for its ability to create alleys. In 1991, at Kalamaria municipality, Thessaloniki, mimosa trees were found with symptoms of a Fusarium wilt disease and many trees were already dying or dead. The first symptom was a characteristic yellowing and wilting of foliage. Leaves on symptomatic trees fell prematurely and eventually the defoliated portion of crowns died. Numerous adventitious branches on the stems also developed wilt symptoms and died. When stems were cross-sectioned, a brownish discoloration in the spring wood vessels of the outer annual ring could be observed. In the more advanced stages of the disease, dark sap exudations flowed out of bark cracks. Orange-pink sporodochia with masses of conidia developed in bark cracks and lenticels. Of 1,520 trees examined for external symptoms in the autumn of 1991, 1,339 (88.2%) were apparently healthy, 96 (6.3%) had symptoms, and 85 (5.6%) were dead. In autumn 1992, the same trees were examined and the respective values were 1,276 (83.9%), 130 (8.6%), and 114 (7.5%). Wood samples from the most recent annual ring taken from 30 infected and 30 apparently healthy trees were plated on potato dextrose agar. Fusarium oxysporum was recovered from 93% of the symptomatic trees and only 7% of the asymptomatic ones. Since 1992, the disease has spread within the area where it was first found but has not been observed anywhere else in Greece. A disease of mimosa with similar symptoms was first reported by Hepting (1) in 1936 from North Carolina. The associated fungus Fusarium oxysporum f. sp. perniciosum was described by Hepting (2), who also demonstrated its pathogenicity. The disease has also been previously reported in Russia. This is the first report of mimosa wilt disease in Europe.

References: (1) G. H. Hepting. Plant Dis. Rep. 20:177, 1936. (2) G. H. Hepting. USDA Circ. 535, 1939.
First Report of Pyrenophora tritici-repentis Race 5 from North America
Authors: Ali S. , Francl L. J. , De Wolf E. D.
Published: May 2007

Tan spot, caused by Pyrenophora tritici-repentis, is an important foliar disease of wheat worldwide. The fungus produces two distinct symptoms, necrosis (nec) and chlorosis (chl), on susceptible wheat genotypes. Fungal isolates have been grouped into five races based on their ability to induce necrosis and/or chlorosis on differentials Glenlea, Katepwa, 6B365, and Salamouni (1). Moreover, the isolates were designated on their ability to induce necrosis and chlorosis as follows: nec+chl+ (necrosis and chlorosis), nec+chl- (necrosis only), nec-chl+ (chlorosis only), and nec-chl- (neither symptom). Races 3 and 5 induce extensive chlorosis (nec-chl+) on 6B365 and Katepwa, respectively. Race 5 was reported on durum from North Africa. Races 1 to 4 were described from North America (1,2). During 1998, a survey of durum fields was conducted in the primary durum-growing area of North Dakota to assess the virulence pattern of P. tritici-repentis. Fifty-two single-spore isolates were obtained from diseased leaves. The isolates were evaluated for their virulence by inoculating them individually onto 15 seedlings of each wheat differential in the greenhouse. Forty-nine of 52 isolates were grouped as race 1 (nec+chl+) and three isolates, obtained from the Langdon Experiment Research Station, were grouped as race 5 (nec-chl+). Race 5 isolates were evaluated three times and consistently induced extensive chlorosis on Katepwa. This is the first report of the occurrence of race 5 outside of North Africa. This race may threaten wheat in the United States, so cultivars and germplasm should be evaluated for resistance. More isolates are under investigation to obtain a comprehensive virulence pattern of the pathogen population in the United States.

References: L. Lamari and C. C. Bernier. Can. J. Plant Pathol. 11:49, 1989; (2) L. Lamari et al. Can. J. Plant Pathol. 17:312, 1995
Characterization of Isolates of Phytophthora infestans from Tomato and Potato in North Carolina from 1993 to 1995
Authors: Fraser Dawn E. , Shoemaker Paul B. , Ristaino Jean B.
Published: May 2007

Eighty-five isolates of Phytophthora infestans from 33 tomato and 8 potato fields in North Carolina, South Carolina, and Tennessee were collected from 1993 to 1995 and tested for mating type, sensitivity to metalaxyl, and allozyme genotype at glucose-6-phosphate isomerase (Gpi) and peptidase (Pep) loci. One isolate collected from potato in eastern North Carolina in 1994 was the A1 mating type, whereas all other isolates from potato and tomato were the A2 mating type. Six isolates were sensitive to metalaxyl (<40% growth at 1.0 μg of metalaxyl per ml), nineteen isolates were intermediate in sensitivity to metalaxyl (>40% growth at 1.0 μg of metalaxyl per ml and <40% growth at 100 μg of metalaxyl per ml), and sixty isolates were resistant to metalaxyl (<40% growth at 1.0 and 100 μg of metalaxyl per ml). Four different allozyme genotypes at the Gpi and Pep loci were identified. The single A1 isolate found on potato in eastern North Carolina had the dilocus allozyme genotype Gpi 86/100, Pep 92/100 and was identified as the US-1 genotype. Fifty-five isolates had the dilocus allozyme genotype Gpi 100/111, Pep 100/100 and were classified as the US-7 genotype, whereas twenty-four isolates were Gpi 100/111/122, Pep 100/100 and were classified as the US-8 genotype. Two isolates that were sensitive to meta-laxyl and seventeen isolates that were intermediate in sensitivity to metalaxyl were found among the US-7 and US-8 genotypes. In addition, five isolates had the allozyme genotype Gpi 100/100, Pep 92/100 (similar to the previously reported US-6 genotype), but they were the A2 mating type and either sensitive or intermediate in response to metalaxyl. These isolates composed a new genotype not previously reported in the United States and were designated as US-18. The US-7 genotype was more frequent on tomato in western North Carolina and the US-8 genotype was present on potato in eastern North Carolina, indicating that different inoculum sources are responsible for epidemics on the two crops in different regions of the state.
Outbreak of Leaf Spot of Saponaria Caused by Alternaria saponariae in California
Authors: Koike S. T. , Henderson D. M. , Tjosvold S. A. , Simmons E. G.
Published: May 2007

Saponaria (Saponaria vaccaria [= Vaccaria hispanica]) is a Caryophyllaceae plant that is grown commercially in California as a cut flower. In 1998, a leaf spot disease devastated the commercially grown saponaria in coastal California. The entire saponaria crop was completely unmarketable because of extensive leaf spotting. Symptoms consisted of circular, brown, necrotic leaf spots with diameters up to 8 mm and concentric zones of lighter and darker tissue. Chlorotic borders developed around the spots. Conidia from leaves were obclavate, usually had 7 transverse and 1 to 4 longitudinal septa, and narrowed gradually toward the apex into a blunt-tipped, unbranched beak cell. The spore body measured 69 to 90 (to 119) × 17 to 21 (to 25) μm, with the distinctive beak cell 17 to 53 μm long. Conidia formed short chains on host tissue. The fungus was identified as Alternaria saponariae (Peck) Neergaard (2). For pathogenicity tests, six representative isolates were grown on V8 juice agar under fluorescent tube lighting. Potted saponaria were sprayed with either conidial concentrations (1 × 10e5 conidia per ml) or water. Plants were incubated in a chamber with a humidifier for 48 h and then maintained in a greenhouse (23 to 25°C). After 14 days, leaf spots similar to the original symptoms developed on all inoculated plants, and the pathogen was reisolated. Plants sprayed with water were symptomless. The experiment was repeated and the results were similar. Using the same isolates and method, we inoculated carnation (Dianthus caryophyllus), sweet William (Dianthus barbatus), and saponaria. However, disease developed only on saponaria. While A. saponariae on saponaria was reported previously in California (1), this is the first report to characterize the pathogen and document that isolates are pathogenic on saponaria but not on other commercial Caryophyllaceae hosts.

References: (1) K. F. Baker and L. H. Davis. Plant Dis. Rep. 34:403, 1950. (2) P. Neergaard. Aarsberet. J. E. Ohlsens Enkes Plantepat. Lab. No. 3, 1938.
The Distribution of Fusarium Wilt of Blackeyed Cowpeas within California Caused by Fusarium oxysporum f. sp. tracheiphilum Race 4
Authors: Smith S. N. , Helms D. M. , Temple S. R. , Frate C.
Published: May 2007

Fusarium wilt of blackeyed cowpeas has been known in California since the 1930s, and breeding for resistance to this disease pathogen has been a continuous effort. During the 1960s and 1970s, California Blackeye 5 (CB 5) cowpea (Vigna unguiculata L. Walp.), a widely grown cultivar of the time, became increasingly diseased by Fusarium oxysporum f. sp. tracheiphilum (Fot) Race 3 (2) throughout the growing regions of California. University of California cultivars CB 46 and CB 88 (1) were developed for resistance to Fot Races 1, 2, and 3. CB 46 is currently the principal blackeye cultivar grown on the majority of the acreage in the San Joaquin Valley. In 1989, a new race we designate “Fot Race 4” was isolated from wilted plants at a single field site in Stanislaus County. In years prior to identification, Fot Race 4 had caused severe wilt of CB 46 and CB 88 in this field. Even though the new Fot Race 4 remained confined to a small area for a number of years, sources of host plant resistance to Fot Race 4 were identified, hybridized, and screened, resulting in new progeny with desirable commercial agronomic characteristics. As observed in Stanislaus County, F. oxysporum f. sp. tracheiphilum Race 4 has the potential to cause serious crop damage, depending on virulence and soil inoculum levels, which may vary from year to year. In 1997 and 1998, an entirely different area in the southern San Joaquin Valley, about 140 miles from the original site in Stanislaus County, was found to have plants infected with Fot Race 4. Diseased plants were collected from patches in three separate CB 46 or CB 88 field sites in Tulare County. About 30 cultures were isolated from the diseased plants, which showed stunting, yellowing, and vascular discoloration. In greenhouse fusarium dip tests CB 46, CB 88, CB 5, and several Fot Race 4 resistant breeding lines were inoculated with all the collected isolates and evaluated. CB 46, CB 88, and CB 5 proved to be susceptible to these isolates, showing typical Fot Race 4 symptoms. The Fot Race 4 pathogen was then reisolated from greenhouse-grown, diseased stem tissue of CB 46, CB 88, and CB 5. These findings emphasize the importance of vigilance and necessity of continual disease surveys. They serve as an early alert for the University of California breeding program, and validate local cooperation with University of California Extension Farm Advisors. As a result of this effort new cultivar candidates with resistance to Fot Race 4 are in the final phases of multi-year commercial testing.

References: (1) D. M. Helms et al. Crop Sci. 31:1703, 1991. (2) K. S. Rigert and K. W. Foster. Crop Sci. 27:220, 1987.
First Report of Powdery Mildew on Cornus florida in Connecticut Caused by Microsphaera pulchra
Authors: Smith V. L.
Published: May 2007

Powdery mildew of dogwood (Cornus florida L.) has been observed on landscape trees since 1992, and has been increasing in severity recently. In 1998, mildewed leaves (n = 100) were collected from each of four locations in Connecticut. White mildew colonies first appeared in the early summer, 4 to 6 weeks after leaf emergence, and the initial colonies rapidly coalesced to cover the entire adaxial leaf surface. Incidence on observed trees reached nearly 100%. Premature autumn coloration and defoliation occurred on those trees where incidence was highest; tree mortality due solely to powdery mildew was not observed. Cleistothecia were apparent on both adaxial and abaxial leaf surfaces within 4 to 6 weeks of initial infection. Mycelium was white in color, and conidiophores were three-celled with a slightly bent foot cell. Fibrosin bodies were not present in conidia (n = 400), which measured 14.1 m ± 0.80 × 28.1 m ± 1.60 (mean + standard error of the mean). Cleistothecia measured 114.7 m ± 1.77 in diameter, and had 4 to 10 dichotomously branched appendages, which measured 140.7 m ± 3.95 in length (1.23× cleistothecial diameter). The fungus was identified as Microsphaera pulchra based on mycelial, conidial, and cleistothecial characteristics (1). In addition, cleistothecia were found on twigs and on fallen leaves of dogwood; these overwintering cleistothecia contained mature asci and mature ascospores in March 1999. Microsphaera penicillata recently was redescribed to include only that species causing powdery mildew on Alnus spp., and having appendages 1.5× cleistothecial diameter (2). The fungus causing powdery mildew in Connecticut previously had been reported to be M. penicillata, which was not found in the present study.

References: (1) U. Braun. Nova Hedwigia 89:1, 1987. (2) U. Braun. The Powdery Mildews (Erysiphales) of Europe. Gustav Fischer, New York, 1995.
First Report of Cercospora traversiana on Trigonella coerulea in Bulgaria
Authors: Bobev S. G. , Margina A. F. , de Gruyter J.
Published: May 2007

In the spring of 1996, diseased plants of Trigonella coerulea were noted in an experimental area at Kazanlak, Bulgaria. The primary symptoms were leaf spots 8 to 2 mm in diameter, light brown then becoming gray and slightly zonate, and surrounded by a diffuse chlorotic margin. When single lesions occur the disease normally develops as a typical leaf spot. However, the development of more than one spot is followed rapidly by yellowing and withering of entire leaflets. Stem lesions usually begin at the point of leaf attachment, extend both directions about 15 to 20 mm, and often encircle the stems. Isolations on potato dextrose agar (PDA) yielded a slow-growing, gray fungus. Conidia from the isolated fungus when inoculated at 3.104 spores per ml on potted T. coerulea seedlings and kept in a moisture chamber for 48 h caused foliar spots in 5 to 8 days and sporulating structures similar to those seen in field observations. Simultaneous inoculation of T. foenum-graecum (fenugreek) plants produced similar symptoms, but the percentage of successfully inoculated leaves (3.6%) was lower than in T. coerulea (27.6%). Conidiophores of the fungus are dark, arising in clusters, unbranched, septate (1 to 3), and have small conidial scars. Conidia are hyaline, straight, multicelled (1 to 17), tapering at the base, and measured 30 to 212 × 4 to 6 μm. The pathogen was identified as Cercospora traversiana Sacc. and this is the first report of its occurrence in Bulgaria.
Verticillium dahliae, a Cause of Wilt in Echinacea purpurea
Authors: Putnam M. L. , Crowe F.
Published: May 2007

In July 1997, mature (flowering) purple coneflower plants exhibiting severe stunting, interveinal leaf bronzing, leaf twisting, and vascular discoloration of the stem were abundant in a 2-ha commercial field in central Oregon. Isolations from vascular tissues onto water agar yielded Verticillium dahliae. A single conidium isolate was obtained and used to inoculate 2-month-old, greenhouse-grown E. purpurea plants raised from seed to complete Koch's postulates. Conidia were washed from 25-day-old cultures grown on potato dextrose agar and filtered through cheesecloth. The resulting conidial suspension was adjusted to 8 × 106 spores per ml. Plants (n = 15) were washed free of soil and the roots immersed into either the conidial suspension (n = 10) or sterile, deionized water (n = 5) for 5 min, then potted into a pasteurized soil mix (1:1:1, clay loam:sand:perlite). Plants were maintained under natural light on a glasshouse bench from February to August (21–30/12–20°C day/night over the course of 6 months). Forty days postinoculation a heat wave caused temperatures in the glasshouse to peak at 42°C, which killed all but one inoculated plant and four control plants. Six months postinoculation the inoculated plant exhibited symptoms similar to those originally observed in affected field-grown plants including leaf bronzing, severe stunting, and vascular discoloration. The control plants were asymptomatic. Isolation from the vascular tissues of the inoculated plant yielded V. dahliae; no fungus was recovered from control plants. This is the first report of Verticillium wilt in purple coneflower.
First Report of Alternaria tenuissima as a Leaf Pathogen of Amaranthus hybridus
Authors: Blodgett J. T. , Swart W. J. , Chen Weiqun
Published: May 2007

Amaranthus hybridus is an important alternative leafy-vegetable crop with the potential for increased commercial production in southern Africa and other semi-arid regions of the world (2). In May 1998, extensive leaf spotting was observed on A. hybridus at Potchefstroom, South Africa. Many of the leaves had symptoms and most were severe. Symptoms were dark brown to black, circular to oval, necrotic lesions with a diameter ranging from <1 mm up to 7 mm. Larger lesions had tan centers. Tissues adjacent to the leaf spots remained green. Alternaria tenuissima was isolated from 43% of 40 lesions sampled making up 89% of the isolates recovered. A. tenuissima was isolated from asymptomatic leaves of 5-month-old A. hybridus plants sampled from the same site in April 1997 (1). The foliar symptoms observed on A. hybridus in Potchefstroom were reproduced by inoculating wounded leaves of A. hybridus with single-spore A. tenuissima isolates obtained from asymptomatic leaves collected at Potchefstroom. Eight isolates were selected for pathogenicity tests conducted in a growth chamber. A. hybridus leaves grown from seed in a greenhouse were placed in moist chambers and wounded with a needle (0.5 mm) at leaf center; one 5-mm-diameter, colonized potato dextrose agar plug of each of the isolates was placed on the center of each leaf. A sterile plug was used as a control. Moist chambers were placed in a growth chamber set at 25°C day and 20°C night and provided artificial light for 16 h per day. In a greenhouse (average temperature 25°C day, 17°C night), a conidial suspension (105 conidia per ml of sterile, distilled water) was applied to an individual leaf of each of 14 plants with an atomizer. Sterile, distilled water was applied to control leaves. Leaves were then wounded with a needle (0.5 mm) at leaf center. Treatments were assigned randomly and the experiments were repeated. Symptoms were first observed at 14 and 18 days (growth chamber and greenhouse, respectively). Seven of the eight isolates caused necrotic lesions with an average diameter of 3 mm (both growth chamber and greenhouse). Symptoms were observed on an average of 56 and 82% of the inoculated leaves (growth chamber and greenhouse, respectively). The range of symptoms was the same as that observed in the field, but symptoms were only observed at the wounds. Controls remained green and showed no symptoms. A. tenuissima was recovered from necrotic lesions of surface-disinfested, inoculated leaves (average 93 and 68%; growth chamber and greenhouse, respectively), never recovered from growth chamber controls, and seldom recovered from greenhouse controls (5%). These results suggest that A. tenuissima is a leaf-spot pathogen of A. hybridus and wounding might trigger disease expression. A minimal amount of leaf spotting of this leafy-vegetable crop can cause total crop loss.

References: (1) J. T. Blodgett et al. S. Afr. J. Sci. 94:xviii, 1998. (2) W. J. Swart et al. S. Afr. J. Sci. 93:xxii, 1997.
First Report of Ceratocystis fimbriata Infecting Balsam Poplar (Populus balsamifera)
Authors: Vujanovic Vladimir , St.-Arnaud Marc , Charlebois Denis , Fortin Elisabeth
Published: May 2007

This is the first report of Ceratocystis fimbriata Ellis & Halst. (Ophiostomatales) (anamorph: Chalara sp. (Corda) Rabenh.) associated with symptoms of perennial canker on small branches and wilt of leaves and twigs on balsam poplar (Populus balsamifera L.). The fungus is known to occur on trembling aspen (P. tremuloides Michx.) (1) throughout the mountainous West and extends eastward to Quebec and Pennsylvania (2).These tree species are common in the boreal and Rocky Mountain areas of North America. In April 1999, the disease was observed on cuttings (15 × 1 cm) collected from the terminal branches of young balsam poplar trees (h = 4.5 m) near Baie Comeau located 350 km northeast of Quebec City (48°61′, 68°21′), Quebec, Canada. Apparently healthy cuttings were potted in a soil mix (peat moss and vermiculite, 3:1 vol:vol), grown in a greenhouse at 22 ± 1°C and watered twice a week. About 2 weeks after bud break, a number of cuttings were symptomatic, showing necrotic bark lesions and cankers, discoloration and wilting of leaves, and reddish brown exudate surrounding leaf petioles. During the following two weeks, 22% of the cuttings died (212 out of 958). The fungus was isolated from diseased cuttings on 2% MEA (malt extract agar), from the necrotic bark around active cankers (2 × 1 cm), from brown to black streaks found in vascular tissue, and from the ascomata found on the canker margin and inconspicuous necrotic roots. From necrotic petioles, one other opportunistic fungus, Aureobasidium pullulans (de Bary) G. Arnaud, was occasionally isolated. The inoculum for infection of the balsam poplar may have originated from neighboring trembling aspen trees. We believe that C. fimbriata could have a negative impact on reforestation efforts unless phytosanitary inspections are made of the planting stock.

References: (1) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN. (2) W. A. Sinclair et al. 1993. Diseases of Trees and Shrubs. 3rd ed. Cornell University Press, Ithaca, NY.
First Record of Bursaphelenchus Nematodes from Pine Forests in Greece
Authors: Skarmoutsos G. , Skarmoutsou H.
Published: May 2007

Pine forests are important elements of natural ecosystems in Greece. Pines are very well adapted to the ecoclimatic conditions of this country and are extensively used in plantations. While there is danger of accidental introduction of Bursaphelenchus xylophilus into Europe through timber trade, in recent years pine wilting of unknown cause has been observed in many European countries. In many cases various Bursaphelenchus spp. have been isolated from wilting conifer species (1–3). A survey for nematodes of pine in Greece was carried out from 1996 to 1998, as part of a project (FAIR 1CT 95-0083) funded by the European Commission, in which five European countries are involved. Trees chosen for sampling were either dying or recently dead. From each tree, three disks 10 cm in thickness were cut, from the lower, medium, and upper parts of the main stem. The bark was removed and Baermann-funnel-extraction for nematodes was immediately carried out for 48 h at room temperature. During the 3 years of the survey, samples from 93 pine trees from different areas of Greece were examined. Samples were obtained from the indigenous species Pinus brutia, P. halepensis, P. nigra, and P. sylvestris as well as the exotic species P. pinaster and P. radiata. Thirty-two of the samples were found infected by different species of Bursaphelenchus. B. eggersi Ruhm was isolated from P. pinaster, B. hellenicus Skarmoutsos, Braasch, and Michalopoulou from P. brutia, and B. leoni Baujard from P. brutia, P. nigra, P. pinaster, and P. radiata. B. sex-dentati Ruhm, the most abundant of all species, was recovered from P. brutia, P. halepensis, P. nigra, P. pinaster, and P. radiata, whereas B. teratospicularis Kakuliya was isolated from P. brutia and P. halepensis. Samples from P. sylvestris did not yield any Bursaphelenchus nematodes. All isolated species constitute a first record in Greece with B. hellenicus described as a new species (4). This study on the relationship between dead and dying pines and nematodes of the genus Bursaphelenchus is the first undertaken in this country.

References: (1) P. Baujard. Rev. Nématol. 3:167, 1980. (2) A. Marinari Palmisano and L. Ambrogioni. Redia 77:225, 1994. (3) J. Philis and H. Braasch. Nematol. Mediterr. 24:119, 1996. (4) G. Skarmoutsos et al. Nematologica 44:623, 1998.