bluuebunny/crossref_metadata_2025 huggingface dataset:
Occurrence of Cucumber mosaic virus in Gerbera jamesonii in India
Authors: Verma N. , Singh A. K. , Singh L. , Kulshreshtha S. , Raikhy G. , Hallan V. , Ram R. , Zaidi A. A.
Published: May 2007

Gerbera jamesonii (family Asteraceae) is a popular perennial ornamental cut flower and potted plant with considerable economic importance. In a survey of gerbera grown in floriculture fields at the Institute of Himalayan Bioresource Technology (IHBT), Palampur and nearby nurseries, color break symptoms on the petals, asymmetrical ray florets, and deformed flowers were observed during 2003-2004. The virus evoked chlorotic local lesions on Chenopodium album, C. amaranticolor, and C. quinoa, while systemic mosaic was observed on Cucumis sativus, Nicotiana benthamiana, N. clevelandii, N. glutinosa, and N. tabacum cv. Samsun. The virus was transmitted nonpersistently by Myzus persicae and Aphis gossypii and was identified as Cucumber mosaic virus (CMV) using enzyme-linked immunosorbent assay (ELISA) with CMV-specific antibodies (Agdia, Elkhart, IN). Polyhedral particles approximately 29 nm were observed with electron microscopy of leaf dips from symptomatic gerbera leaves. Total RNA was isolated from the infected gerbera plants and N. glutinosa by using RNAqueous (Ambion, Austin, TX). CMV-specific primers (1) were used to detect the virus with reverse transcription-polymerase chain reaction that produced an amplicon predicted size of approximately 540 bp, but the virus was not detected in healthy controls. Sequence alignment of the amplicons (533 bp) utilizing BLAST resulted in 91 to 99% homology with the partial intercistronic region and partial coat protein gene (1042-1574 bp) (gene sequence submitted to EMBL database with Accession no. AJ634532) of CMV RNA3 in subgroup I. To our knowledge, this is the first report of CMV on gerbera in India.

Reference: (1) C. De Blas et al. J. Phytopathol. 141:323, 1994.
Sensitivity of California Isolates of Uncinula necator to Trifloxystrobin and Spiroxamine, and Update on Triadimefon Sensitivity
Authors: Miller T. C. , Gubler W. D.
Published: May 2007

Sensitivities of Uncinula necator to spiroxamine and trifloxystrobin were established by assay of 36 and 35 isolates, respectively, recovered from California grape vineyards in 2002 and increased as single-spore lines for laboratory testing. Twenty-nine single-spore isolates also were evaluated for levels of sensitivity to the fungicide triadimefon to determine if there had been a reversion to sensitivity following the development of resistance in 1986. Although triadimefon use was limited after 1992, other demethylation inhibitor (DMI) fungicides (fenarimol and myclobutanil) were used extensively in California vineyards. For spiroxamine, the sample mean value of the median effective concentration (EC50 value) was 365 μg/liter (95% confidence interval [CI] from 251 to 531 μg/liter) and values were distributed log-normally. The corresponding mean for trifloxystrobin was 12.8 μg/liter bounded by 8.9 to 18.5 μg/liter for the 95% CI. State-wide, the triadimefon mean EC50 was 8.8 mg/liter, bounded by a 5.3 to 14.5 mg/liter 95% CI, and those values were significantly higher than those obtained in the last assay 12 years earlier. Significant differences in sensitivity of U. necator to triadimefon were detected at a regional scale by comparison of mean EC50 values of frequency distributions representative of regions within California, although the relations between those regions were different from the prior survey.
Biological Control of Blossom Blight of Alfalfa Caused by Botrytis cinerea Under Environmentally Controlled and Field Conditions
Authors: Li G. Q. , Huang H. C. , Acharya S. N. , Erickson R. S.
Published: May 2007

Fungal and bacterial antagonists were tested for their inhibition of sporulation of Botrytis cinerea on detached alfalfa florets. Clonostachys rosea, Gliocladium catenulatum, and Trichoderma atroviride were evaluated for protecting young blossoms and pods of alfalfa from infection by B. cinerea in vitro. C. rosea was further tested to control pod rot and seed rot caused by B. cinerea under field conditions. The results showed that four of the tested antagonists, C. rosea, G. catenulatum, T. atroviride, and Trichothecium roseum, could inhibit sporulation by B. cinerea on detached alfalfa florets. Both C. rosea and G. catenulatum were effective in suppression of infection of alfalfa pods by B. cinerea when inoculated on fresh petals of alfalfa at the anthesis stage, and their efficacy was greater than that of Trichoderma atroviride. A significant suppression of B. cinerea by C. rosea and G. catenulatum on pods and seed of alfalfa was observed when they were inoculated on senescent petals at the pod-development stage. Results of a field trial indicated that C. rosea applied to upper parts of alfalfa plants significantly suppressed pod rot and seed rot caused by B. cinerea, and significantly increased seed production of alfalfa in each of 3 years. These studies show that C. rosea has potential as a biocontrol agent for control of alfalfa blossom blight caused by B. cinerea.
Acremonium implicatum, a Seed-Transmitted Endophytic Fungus in Brachiaria Grasses
Authors: Dongyi Huang , Kelemu Segenet
Published: May 2007

The pan-tropical grass genus Brachiaria comprises about 100 species, several of which are forages of economic importance, particularly in tropical America. Acremonium implicatum is a fungus that forms an endophytic association with at least some of these economically important grasses. To ascertain whether A. implicatum can be seed transmitted in Brachiaria species, we vegetatively propagated, under greenhouse conditions, 20 tillers from an endophyte-infected mother plant obtained from each of 14 Brachiaria hybrids and species. Ten tillers of each genotype were treated with the fungicide tebuconazole to eliminate the endophyte, and the other 10 were left untreated. Seeds were then harvested individually from all 20 of these genetically identical plants, germinated, and the seedlings grown. A previously developed polymerase chain reaction-based method used a pair of endophyte-specific primers to amplify a diagnostic 500-bp DNA fragment. The seedlings generated from seeds harvested from endophyte-infected plants also tested positive, whereas those from seeds of endophyte-free plants showed no amplification products. This is the first report of A. implicatum being transmitted through seeds of Brachiaria grasses.
Incidence and Causes of Postharvest Fruit Rot in Stored Michigan Cranberries
Authors: Olatinwo R. O. , Schilder A. M. C. , Kravchenko A. N.
Published: May 2007

The incidence of postharvest fruit rot and associated fungi was studied in stored cranberries in Michigan in 2000 and 2001. Ripe cranberries were harvested from eight commercial farms in southwest and northeast Michigan, including the Upper Peninsula. Eight cranberry cultivars were represented: Stevens, Searles, Le Munyon, Pilgrim, Ben Lear, Bergman, Beckwith, and WSU 61. Fruit rot incidence was assessed within 1 week after harvest. Remaining sound fruit was stored for 2 months at 5°C, and fungi were isolated from rotted fruit after 1 and 2 months of storage. Year and region, but not cultivar, significantly affected the overall rate of rot development in storage. Storage rot levels generally were lower in 2001 than in 2000, particularly in southern Michigan. A high incidence of field rot at harvest did not necessarily lead to a high incidence of storage rot. Storage rot tended to be more severe in the northern than in the southern growing region. Fungi most frequently associated with storage rot were Fusicoccum putrefaciens, Colletotrichum acutatum, Coleophoma empetri, Phomopsis vaccinii, and Phyllosticta elongata. F. putrefaciens was the predominant storage rot fungus in northern Michigan in both years and caused up to 80% fruit rot in storage. C. empetri and P. elongata also were isolated more frequently from beds in northern than southern Michigan in 2001. The cvs. Pilgrim and Stevens were more susceptible to storage rot caused by Colletotrichum acutatum, and Bergman and WSU 61 were more susceptible to storage rot caused by Phomopsis vaccinii than some of the other cultivars.
First Report of Soybean dwarf virus on Soybean in Wisconsin
Authors: Phibbs A. , Barta A. , Domier L. L.
Published: May 2007

Soybean dwarf virus (SbDV) causes widespread economic losses on soybean (Glycine max (L.) Merr.) in Japan (4), and has been reported on soybean in Virginia (2), in various legumes in the southeastern United States (1), and in peas in California (3). During late July and early August of 2003, soybean plants in Wisconsin were surveyed for SbDV. In 286 soybean fields at the R2-R4 growth stage, the uppermost fully unfurled leaf was collected from 10 plants at each of five sites. Samples were collected at random without regard to symptoms. SbDV symptom information was not recorded. Samples were stored on ice until frozen at -80°C. Five fields in four Wisconsin counties (Columbia, Lafayette, Sauk, and Waushara) tested positive for SbDV using double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). DAS-ELISA testing was conducted with reagents from Agdia, Inc (Elkhart, IN) following the manufacturer's protocol. Absorbance was read at 405 nm with a Stat Fax 2100 microplate reader (Awareness Technology, Inc., Palm City, FL) or visually evaluated. DAS-ELISA did not discriminate between strains of SbDV. The presence of SbDV was confirmed, and strain identity was inferred as dwarfing strain using reverse transcription-polymerase chain reaction (RT-PCR). Total RNA was extracted from homogenized leaf tissue, reverse transcribed, and amplified with the SuperScript One Step RT-PCR System (Invitrogen, Carlsbad, CA) and SbDV-specific primers (5′-CTGCTTCTGGTGATTACACTGCCG-3′ and 5′-CGCTTTCATTTAACGYCATCAAAGGG-3′). Size of the RT-PCR products (110 bp) was consistent with the dwarfing strain, SbDV-D. All locations that tested positive for SbDV showed soybean aphids, Aphis glycines Matsumura (Homoptera: Aphididae), on 100% of soybean plants. Several aphid species have been reported to vector SbDV, but at this time, vector relations in the Wisconsin infections are unknown. To our knowledge, this is the first report of SbDV infecting soybean in Wisconsin.

References: (1) V. D. Damsteegt et al. Plant Dis. 79:48, 1995. (2) A. Fayad et al. Phytopathology (Abstr.) 90(Suppl.):S132, 2000. (3) G. R. Johnstone et al. Phytopathology (Abstr.) 74:795(A43), 1984. (4) T. Tamada et al. Ann. Phytopathol. Soc. Jpn. 35:282, 1969.
Black Dead Arm and Basal Canker of Vitis vinifera cv. Red Globe Caused by Botryosphaeria obtusa in Chile
Authors: Auger J. , Esterio M. , Ricke G. , Pérez I.
Published: May 2007

Several years ago, Vitis vinifera cv. Red Globe vines (over 6 years old), started to show disease symptoms approximately 10 weeks after bud break. Symptoms first appeared on the leaves at the base of the shoots and then spread to other leaves, continuing to appear throughout the growing season. Two forms of the disease (severe and mild) were observed, each case leading to premature leaf fall. The severe form was characterized by dieback of one or more shoots accompanied by leaf drop and shriveling and drying of fruit clusters. The mild form was characterized by wine-red spots on the leaf margins or the leaf blade, which coalesced to form large zones of necrosis between the veins and the margins of the leaf. Fruit clusters may wither. If the bark is scraped off, a brown streak, 1 to 2 cm wide, was often seen in the wood. The streaking began at the base of the affected shoot and extended upward to the ground level, eventually resulting in a basal canker. Botryosphaeria obtusa (Schwein.) Shoemaker (anamorph = Sphaeropsis malorum Berk.) was isolated from 86% of samples from vines that were 6 to 10 years old from 12 locations in IV, V, VI, and metropolitan regions of Chile. Isolations were made from brownstreaked wood. Isolates were identified on the basis of a previous description (1,2) and internal transcribed spacer (ITSI-5.8S-ITS2) rDNA sequences identical to those of B. obtusa (culture KJ9356, GenBank Accession No. AF027759). B. obtusa is established as one of the main fungi associated with black dead arm of grapevine (2,3). Pathogenicity tests were completed by inoculating approximately 20 μl of mycelial suspension via injection into the pith of 16 single-node, rooted cuttings of V. vinifera cv. Red Globe. Sixteen control cuttings were injected with an equal volume of sterile distilled water. Twenty weeks after inoculation, all B. obtusa-inoculated cuttings exhibited brown streaks in the wood extending 50 to 60 mm from the point of inoculation. The wood streaking observed in inoculated plants was identical to symptoms observed in naturally infected black dead arm vines in the vineyard. No symptoms were observed in the controls. B.obtusa was reisolated from the region of brown streaking in all the inoculated cuttings. B. obtusa was not isolated from the water-treated controls. To our knowledge, this is the first report of B. obtusa causing black dead arm and basal canker on Red Globe grapevine in Chile. The fungal isolates have been deposited in the plant pathology laboratory of the Sanidad Vegetal Department of Agronomy Faculty of the University of Chile under the name V. vinifera/B. obtusa from N 1 to 16.

References: (1) G. Cristinzio. Inf. Fitopatol. 28:21, 1978. (2) P. Larignon and B. Dubos. Phytoma 538:26, 2001. (3) A. J. L. Phillips. J. Phytopathol. 146:327, 1998.
Population Diversity within Isolates of Colletotrichum spp. Causing Glomerella Leaf Spot and Bitter Rot of Apples in Three Orchards in North Carolina
Authors: González Eugenia , Sutton Turner B.
Published: May 2007

The population diversity within isolates of Glomerella cingulata and Colletotrichum spp. associated with Glomerella leaf spot and bitter rot of apples was studied in an orchard of cv. Granny Smith located in Wilkes County, NC, and one orchard each of cultivars Granny Smith and Gala located in Lincoln County, NC. Morphological characters and vegetative compatibility groups (VCGs) were used to determine diversity within the species. The relative frequencies of the morphological types found within each species in each orchard were also determined. G. cingulata was the predominant species associated with bitter rot in the three orchards and Glomerella leaf spot in the Gala orchard. In the three orchards, different morphological types were observed within isolates of G. cingulata and Colletotrichum acutatum, but not within isolates of Colletotrichum gloeosporioides. Isolates of C. gloeosporioides were not found in the orchard of cv. Granny Smith in Lincoln County. In the other two orchards, C. gloeosporioides represented the lowest proportion of the population. Three VCGs were found among isolates of G. cingulata (VCG-1, 2, and 6), two among isolates of C. gloeosporioides (VCG-9 and 10), and two among isolates of C. acutatum (VCG-15 and 16). VCGs 2, 6, 9, 10, 15, and 16 were found in the Granny Smith orchard in Wilkes County, VCGs 1, 2, and 6 in the Gala orchard in Lincoln County, and VCGs 2 and 6 in the Granny Smith orchard in Lincoln County. Differences in frequencies among the different morphological types found within the three orchards remained relatively similar throughout the season and from year to year, suggesting that the relative frequencies of G. cingulata, C. gloeosporioides, and C. acutatum remain stable in an orchard once the fungi are established.
Genetic Diversity and Aggressiveness of Ophiosphaerella korrae, a Cause of Spring Dead Spot of Bermudagrass
Authors: Iriarte F. B. , Wetzel H. C. , Fry J. D. , Martin D. L. , Tisserat N. A.
Published: May 2007

The distribution of three Ophiosphaerella spp. that cause spring dead spot (SDS) of bermudagrass was studied by sampling at 24 locations in the southeastern United States. O. korrae was isolated from 73% of the 204 bermudagrass cores collected and was the only SDS pathogen recovered at most sites. O. herpotricha was isolated at three locations in Kentucky and one in North Carolina, and O. narmari was found at two locations in North Carolina. Most O. korrae isolates collected from Alabama, Kentucky, Mississippi, Tennessee, and Virginia clustered in an amplified fragment length polymorphism group (AFLP group II) that was distinct from Kentucky bluegrass isolates collected throughout North America and similar to bermudagrass isolates from Kansas and Oklahoma (AFLP group I). A third AFLP group (III) consisting of bermudagrass isolates from Mississippi and Virginia was identified. Isolates representing AFLP groups II and III grew more rapidly on potato dextrose agar at 25 and 30°C than those in group I. O. korrae isolates differed in their aggressiveness to two bermudagrass cultivars in greenhouse studies, but these differences were not associated with AFLP group, location, or host from which the isolate was collected.
Detection and Quantification of Fusarium solani f. sp. glycines in Soybean Roots with Real-Time Quantitative Polymerase Chain Reaction
Authors: Gao X. , Jackson T. A. , Lambert K. N. , Li S. , Hartman G. L. , Niblack T. L.
Published: May 2007

Fusarium solani f. sp. glycines is the causal organism of soybean sudden death syndrome (SDS). This organism is difficult to detect and quantify because it is a slow-growing fungus with variable phenotypic characteristics. Reliable and fast procedures are important for detection of this soybean pathogen. Protocols were optimized for extraction of DNA from pure fungal cultures and fresh or dry roots. A new procedure to test polymerase chain reaction (PCR) inhibitors in DNA extracts was developed. Novel real-time quantitative PCR (QPCR) assays were developed for both absolute and relative quantification of F. solani f. sp. glycines. The fungus was quantified based on detection of the mitochondrial small-subunit rRNA gene, and the host plant based on detection of the cyclophilin gene of the host plant. DNA of F. solani f. sp. glycines was detected in soybean plants both with and without SDS foliar symptoms to contents as low as 9.0 × 10-5 ng in the absolute QPCR assays. This is the first report of relative QPCR using the comparative threshold cycle (Ct) method to quantify the DNA of a plant pathogen relative to its host DNA. The relative QPCR assay is reliable if care is taken to avoid reaction inhibition and it may be used to further elucidate the fungus-host interaction in the development of SDS or screen for resistance to the fungus.
First Report of the Causal Agent of Huanglongbing (“Candidatus Liberibacter asiaticus”) in Brazil
Authors: Coletta-Filho H. D. , Targon M. L. P. N. , Takita M. A. , De Negri J. D. , Pompeu J. , Machado M. A. , do Amaral A. M. , Muller G. W.
Published: May 2007

Huanglongbing (ex-greening) disease is one of the most serious diseases of citrus. It is caused by the phloem-limited, gram-negative bacterium “Candidatus Liberibacter spp.”. This bacterium is not well characterized mainly because it is still uncultured. There are two known strains, Asian (“Candidatus Liberibacter asiaticus”) and African (“Candidatus Liberibacter africanus”) that cause severe damage to citrus plants including twig dieback, decline, and death. Symptoms first appear as leaf mottling and chlorosis occurring in one shoot or sector of trees. Later, leaf symptoms resemble nutritional deficiencies (Zn, Ca, and N) that vary depending on the strains, with more severe symptoms caused by “Ca. L. asiaticus”. The Asian strains are transmitted by the Asian citrus psyllid (AsCP), Diaphorina citri, which is present in Brazil. The bacterium has been detected in citrus plants in many geographic locations including China, Japan, Thailand, India, the Philippines, the Arabian Peninsula, and Africa. In 2004, plants showing Huanglongbing symptoms were observed in the Araraquara County, a central region of the State of Sao Paulo, the largest citrus-producing area in Brazil. To verify the presence of “Ca. L. spp.” in these plants, leaf samples of sweet orange cvs. Hamlin and Valencia were used for DNA extraction and polymerase chain reaction amplification using the specific OI1 and Oi2c primers (1). Amplification of the 16S rDNA was positive for 2 (cvs. Hamlin and Valencia) of 10 analyzed plants. The amplified fragments were cloned and sequenced. The amplicons obtained from both plants showed the same sequence, which differed from “Ca. L. africanus”, utilized as the positive control in the amplification experiment (27 divergent bases in 1,160). The sequences were used for BLAST searches, and the results showed identities ranging from 94.71 to 100% with “Ca. L. spp.” sequences available at the National Center for Biotechnology Information database (on-line publication). The highest scores were obtained with “Ca. L. asiaticus sequences. These analyses confirmed the presence of such agent in the State of Sao Paulo. To our knowledge, this is the first report of “Ca. L. asiaticus” in Brazil as well as elsewhere in the Americas. The significance of this report relates to the potential damage that this pathogen could cause to the citrus industry in the largest citrus-producing country in the world. It remains unclear how and when the pathogen entered Brazil.

Reference: (1) S. Jagoueix et al. Mol. Cell Probes 10:43, 1996.
A Postharvest Fruit Rot in d'Anjou Pears Caused by Sphaeropsis pyriputrescens sp. nov
Authors: Xiao C. L. , Rogers J. D.
Published: May 2007

During a survey of postharvest diseases in stored pears conducted in the 2001-02 storage season, a new postharvest fruit rot in d'Anjou pears was discovered in Washington State. Symptoms of this disease were stem-end rot, calyx-end rot, and wound-associated rot, which presumably originated from infections of stem, calyx, and wounds on the fruit surfaces, respectively. The decayed area on the fruit was firm or spongy and appeared brown. During the late storage period from March to May 2002, this disease was observed in 19 of 39 lots and accounted for 2 to 21% of all decayed fruit. The causal agent, Sphaeropsis sp., was consistently recovered from decayed fruit with the symptoms described above. Two isolates of the fungus were used for pathogenicity tests on pear fruit. Decay symptoms developed on fruit inoculated with spore suspensions of the fungus on the stem, calyx, and wounds on the fruit surface. The fungus was reisolated from these decayed fruit. The fungus, Sphaeropsis pyriputrescens sp. nov., was characterized and described. On potato dextrose agar (PDA), oatmeal agar, and pear juice agar at 20°C, the fungus grew at mean rates of 21, 15, and 24 mm day-1 in colony diameter, respectively. On PDA, the fungus formed a circular colony with dense, hyaline hyphae and a few or some aerial mycelia. Colonies appeared light yellow to yellow on 2-week-old PDA cultures. The fungus grew at temperatures from 0 to 25°C, with optimum growth between 15 and 20°C, little or no growth at 30°C, and no growth at 35°C. This is a low-temperature species.
Comparison of Reduced-Application and Sulfur-Based Fungicide Programs on Scab Intensity, Fruit Quality, and Cost of Disease Control on Peach
Authors: Schnabel Guido , Layne Desmond R.
Published: May 2007

The costs of two reduced-fungicide programs (5 applications each) and two micronized wettable-sulfur programs (6 or 11 applications each) and their impact on scab control and fruit quality were evaluated on ‘Contender’ and ‘Cresthaven’ peach over two growing seasons. The reduced-fungicide programs consisted of applications of chlorothalonil and captan or chlorothalonil, azoxystrobin, and captan. All programs provided excellent scab control when disease pressure was low to moderate; however, six sulfur applications did not adequately control scab under high disease pressure. The product cost of the reduced-fungicide chemicals was higher, but comparable with six applications of micronized wettable sulfur or nine hypothetical applications of nonmicronized wettable sulfur per season. The reduced-fungicide programs were preferable to weekly applications of sulfur (11 applications) because they equally controlled scab at a reduced cost and have greater potential to protect against other summer diseases. The fungicide program effects on fruit quality were inconsistent. A more detailed study is needed to determine if a relationship between fungicide programs and fruit quality exists.
Shift in Sensitivity of Alternaria solani in Response to QoI Fungicides
Authors: Pasche J. S. , Wharam C. M. , Gudmestad N. C.
Published: May 2007

Isolates of Alternaria solani, cause of potato early blight, collected in 1998 through 2001 from various potato growing areas across the midwestern United States, were tested for sensitivity to azoxystrobin. Isolates collected in 1998, prior to the introduction of azoxystrobin, were tested to establish the baseline sensitivity of the fungus to this fungicide. Isolates collected in subsequent years, not necessarily from the same sites as baseline isolates, were tested to determine if populations of A. solani had become less sensitive to azoxystrobin. Azoxystrobin sensitivity was determined utilizing an in vitro spore germination assay. The effective fungicide concentration that inhibited spore germination by 50% (EC50) was determined for each isolate. There was no significant difference in mean EC50 values between baseline isolates and all other isolates collected through 1999. Mean azoxystrobin EC50 values of A. solani isolates collected in 2000 and 2001 were significantly higher compared with means from previous years, and mean azoxystrobin EC50 values from 2001 were significantly higher than means from isolates collected in 2000. A subset of 54 A. solani isolates was evaluated in vitro for cross-sensitivity to pyraclostrobin and trifloxystrobin. A highly significant and strong correlation among the isolates tested for fungicide cross-sensitivity was detected between azoxystrobin and pyraclostrobin; however, the correlation between azoxystrobin and trifloxystrobin, and between trifloxystrobin and pyraclostrobin, was significant but weak. A second subset of five isolates was chosen for in vivo assessment of azoxystrobin, pyraclostrobin, and trifloxystrobin sensitivity. Disease severity on plants treated with azoxystrobin and pyraclostrobin was significantly greater with reduced-sensitive A. solani isolates compared with sensitive isolates. Disease severity was not statistically different between azoxystrobin reduced-sensitive and sensitive A. solani isolates on plants treated with trifloxystrobin. This is the first report of a shift in sensitivity to QoI fungicides in a fungus possessing only an anamorphic stage.
Chemical Alternatives to Methyl Bromide in Spanish Strawberry Nurseries
Authors: Cal A. De , Martinez-Treceño A. , Lopez-Aranda J. M. , Melgarejo P.
Published: May 2007

Strawberry runners are a high-value cash crop in Spain that requires vigorous transplants free of pathogens. Preplant soil fumigation with methyl bromide, or with mixtures of methyl bromide and chloropicrin, is a standard practice for controlling soilborne diseases. Soil fumigants chloropicrin, 1,3-dichloropropene, dazomet, metam-sodium, metam potassium, and dimethyl disulfide were evaluated in combination with different plastic films as alternatives for methyl bromide soil fumigation of strawberry nurseries. The studies were conducted over a 4-year period, with fumigant applications prior to planting. Verticillium wilt (caused by Verticillium spp.) and crown rot (caused by Phytophthora cactorum) were the main diseases. Chloropicrin, 1,3-dichloropropene, and dazomet compared well with methyl bromide fumigation for control of strawberry nursery diseases. Furthermore, 1,3-dichloropropene and methyl bromide, applied at 50% rate under virtually impermeable film, provided effective disease control in strawberry nurseries. Fumigant effects on fungal soil populations are discussed.
First Report of Bacterial Canker of Walnut Caused by Brenneria nigrifluens in France
Authors: Ménard M. , Delort F. , Baudry A. , Le Saux M.
Published: May 2007

Since the summer of 2000, vertical oozing cankers have been observed on trunks and branches of Persian walnut trees (Juglans regia). Cvs. Fernor, Chandler, Mayette, and Hartley were the most frequently affected, but cvs. Lara and Franquette could also be affected. Brenneria nigrifluens (synonym Erwinia nigrifluens) (3) was isolated from diseased trees from 13 orchards and nurseries in southwestern (Aquitaine, Périgord, Charentes, and Quercy), southeastern (Grenoble areas), and western (near Angers) France. Cankers were observed on trunks and branches where brown-to-black exudates staining the bark appeared mainly in the summer. Isolations were performed primarily from exudates but also from infected tissues by using King's medium B. Colonies similar in appearance to Brenneria nigrifluens (1) were purified and characterized. Gram reaction, Kovac's oxidase, oxidative-fermentative metabolism, and urease activity were assayed for all isolates. API Biotype 100 kits (BioMérieux, Marcy l'Etoile, France) were used as recommended, except that incubations were at 28°C for 4 days. When compared with the reference strain (French Collection of Plant Pathogenic Bacteria (CFBP) 4998T = National Collection of Plant Pathogenic Bacteria (NCPPB) 564T = American Type Culture Collection (ATCC) 13028T) from California, 14 isolated strains were identified as B. nigrifluens on the basis of physiological and biochemical characteristics. These 14 strains were deposited in the CFBP under Accession Nos. 6746 to 6759. Pathogenicity of three selected strains (CFBP 6746, 6747, and 6758) was confirmed by inoculating branches of 7-year-old walnut trees with 108 CFU of each isolate introduced in wounds (2). The reference strain (CFBP 4998T) and water were similarly inoculated as controls. Two and five months later, necrotic lesions were observed in the inner bark and dark lines were observed in internal wood, but no external cankers were observed on any trees inoculated with the local and reference strains. B. nigrifluens was reisolated from the dark lines in internal wood up to approximately 10 cm from the inoculation site. To our knowledge, this is the first report of this bacterium in France.

References: (1) L. Hauben et al. Syst. Appl. Microbiol. 21:384, 1998. (2) M. Ridé and S. Ridé. Proc. Int. Conf. Plant Pathogenic Bacteria, 4th, 2:957, 1978. (3) E. E. Wilson et al. Phytopathology 47:669, 1957.
First Report of Ash Anthracnose Caused by Discula fraxinea in Oregon
Authors: Rossman A. Y. , Castlebury L. A. , Putnam M. L.
Published: May 2007

Anthracnose on ash trees has been observed on landscape trees in western Oregon, yet there has been no formal report of the disease or its causal fungus. Anthracnose symptoms are observed annually in May and become severe by July when defoliation starts to occur. From 1989 to now, samples have been received from Benton, Josephine, and Marion counties, suggesting that ash anthracnose has been present throughout western Oregon for some time. To identify the causal agent, a fungus was isolated from acervuli on necrotic lesions on leaves of cultivated white ash (Fraxinus americana L.) trees in Benton County in July 2003. The acervuli produced hyaline, nonseptate, ellipsoid conidia 5 to 11 × 3.5 to 6 µm in diameter. The fungus was identified as Discula fraxinea (Peck) Redlin & Stack (teleomorph Gnomoniella fraxini Redlin & Stack) (2). The sequences of the internal transcribed spacer (ITS) region (GenBank Accession No. AY455814) and large subunit (GenBank Accession No. AY455818) nrDNA agreed with those of D. fraxinea from Maryland, except for three single-base substitutions and three insertions/deletions in ITS1. Ash anthracnose has been reported from the central and eastern United States and California, the prairie provinces in Canada, and recently, from British Columbia (1). A specimen (U.S. National Fungus Collections BPI 843391) and culture (Centraal Bureau voor Schimmelcultures CBS 114053) of D. fraxinea from Oregon were deposited.

References: (1) D. F. Farr et al. Fungal Databases. Systematic Botany and Mycology Laboratory. On-line publication. ARS USDA, 2003. (2) S. C. Redlin and R. W. Stack. Mycotaxon 32:175, 1988.
First Report of Beet pseudo yellows virus in Blackberry in the United States
Authors: Tzanetakis I. E. , Martin R. R.
Published: May 2007

Blackberry (Rubus sp.) plants in Arkansas, North Carolina, and South Carolina during the last 3 years have shown symptoms typical of virus infection, including vein yellowing, line pattern, and mottle, and in certain cases, decline and death. All of the symptomatic plants used in our studies were infected with Blackberry yellow vein associated virus (BYVaV) (1). We cloned cDNA derived from dsRNA extracted from a symptomatic plant from South Carolina and identified two cDNA clones (approximate size of 700 and 900 bp, in addition to those that corresponded to a sequence of BYVaV) with sequences identical to the sequence (GenBank Accession No. AY 268107) of Beet pseudo yellows virus (BPYV) heat shock protein 70 homolog gene. Total RNA extracts from the symptomatic plant were tested using reverse transcription-polymerase chain reaction (RT-PCR) with oligonucleotide primers BP CPm F (5′ TTCATATTAAGGATGCGCAGA 3′) and BP CPm R (5′ TGAAAGATGTCCRCTAATGATA 3′) that amplified a fragment of the minor coat protein (CPm) gene of BPYV. A PCR amplicon of the expected size (334 bp) was generated, and sequencing confirmed the results of the random cloning. We also detected the virus in a second blackberry plant from South Carolina with RT-PCR. To our knowledge, this is the first report of blackberry as a host of BPYV and the third new host of BPYV identified in the last few months (2,3). The naturalization of Trialeuroides vaporariorum, the greenhouse whitefly in the southern United States, and the broad host range of virus and vector make BPYV a potential threat for many crops in North America.

References: (1) I. E. Tzanetakis et al. (Abstr.) Phytopathology 93:S85, 2003. (2) I. E. Tzanetakis et al. Plant Dis. 87:1398, 2003. (3) W. M. Wintermantel. Plant Dis. 88:82, 2004.
Perennation of Uncinula necator in Vineyards of Eastern Washington
Authors: Grove G. G.
Published: May 2007

Studies on the mode of perennation of Uncinula necator in Eastern Washington were conducted over a 4-year period. Evidence of perennation of U. necator in infected dormant buds was not evident during vineyard surveys conducted over the period. Cleistothecia retrieved from bark fissures and senesced leaves contained viable ascospores at bud burst and later. The proportion of cleistothecia retrieved from bark that contained viable ascospores at bud burst ranged from 0.19 to 0.48, 0.09 to 0.72, 0.18 to 0.22, and 0.48 to 0.67 in 1998, 1999, 2000, and 2001, respectively. Viability of cleistothecia retrieved from senesced leaves in two vineyards at bud burst was 0.41 and 0.40 in 1998 and was 0.5 and 0.4 in 1999. Ascospore release in lab studies occurred from the late-dormant stage through the prebloom and (in some cases) the bloom stages. The initial ascosporic infection of Chardonnay leaves began at the late-dormant stage; colony numbers then declined through the prebloom and bloom stages. In vineyard studies, ascospores were trapped as late as 70 days after bud burst during rain events of 3.9 to 9.6 mm. Detection of ascospores in vineyard air preceded the initial occurrence of powdery mildew symptoms and signs and the occurrence of conidia in volumetric spore traps by several days. Cleistothecia are the only known source of primary inoculum in the grape-production regions of Eastern Washington.
Effects of Silicon and Fungicides on the Control of Leaf and Neck Blast in Upland Rice
Authors: Seebold K. W. , Datnoff L. E. , Correa-Victoria F. J. , Kucharek T. A. , Snyder G. H.
Published: May 2007

Silicon (Si) has been shown to suppress diseases of rice such as blast when applied to Si-deficient soils. In 1995 and 1996, Si was applied at 1,000 kg ha-1 to at two locations in eastern Colombia to determine if Si combined with reduced rates of fungicide could be used to manage leaf and neck blast effectively in upland rice. Two applications of edifenphos and three applications of tricyclazole were made at 0, 10, 25, or 100% of their labeled rates after amendment of soil with Si. At both locations, Si alone and Si combined with edifenphos reduced leaf blast severity by 22 to 75% when compared with nonamended, untreated controls, and suppression of leaf blast by Si alone was equal to or better than the full rate of edifenphos alone. Si alone suppressed neck blast as effectively or better than the full rate tricyclazole when severity was low; however, when severity was higher, a 10% rate of tricyclazole was needed in addition to Si. No differences in yield were observed between Si without fungicides and fungicides (full rate) without Si. Applications of Si made in 1995 had significant residual activity in terms of disease control and yield in 1996. The application of Si to Si-deficient soils may permit the use of reduced rates of fungicide to manage leaf and neck blast in upland rice.
Systemic Resistance Induced by Trichoderma hamatum 382 in Cucumber Against Phytophthora Crown Rot and Leaf Blight
Authors: Khan J. , Ooka J. J. , Miller S. A. , Madden L. V. , Hoitink H. A. J.
Published: May 2007

Phytophthora root rot, crown rot, leaf and stem blight, and fruit rot of cucumber can cause serious losses, and are difficult to control. Although composts can be used successfully for control of Phytophthora root rots, little is known about their effects on Phytophthora diseases of aboveground plant parts. This research shows that the severity of Phytophthora root and crown rot of cucumber caused by Phytophthora capsici was suppressed significantly in cucumber transplants produced in a composted cow manure-amended mix compared with those in a dark sphagnum peat mix. In split root bioassays, Trichoderma hamatum 382 (T382) inoculated into the compost-amended potting mix significantly reduced the severity of Phytophthora root and crown rot on paired roots in the peat mix. This effect did not differ significantly from that provided by a drench with benzothiadiazole (BTH) or mefenoxam (Subdue MAXX). Based on area under disease progress curves, T382 also significantly reduced the severity of Phytophthora leaf blight in transplants produced in the compost mix compared with controls not inoculated with T382. Efficacy of T382 did not differ significantly from that provided by a drench with BTH. T382 re-mained spatially separated from the pathogen in plants in both the split root and leaf blight bioassays, suggesting that these effects were systemic in nature.
First Report of Southern Blight Caused by Sclerotium rolfsii on Laurustinus
Authors: Polizzi G. , Vitale A. , Parlavecchio G.
Published: May 2007

Laurustinus (Viburnum tinus L.), native to the Mediterranean Region, is an evergreen shrub commonly used as a specimen shrub or small tree or used in border plantings. During August 2003, a blight occurred on 2-year-old-plants of laurustinus growing in pots in a nursery in eastern Sicily (Italy). Disease incidence ranged from 2 to 5% across the field. Symptoms included 3 to 4 cm long lesions and the development of white mycelial strands and brown, 1.0 to 1.8 mm, nearly spherical sclerotia on the crown of plants at the soil line that are typical of Sclerotium rolfsii Sacc. The foliage of infected plants wilted, followed by a sudden collapse of the plant. The fungus was consistently isolated on acidified potato dextrose agar (PDA) (pH 4.5) by plating symptomatic tissues that were surface disinfested (1.2% NaOCl) for 1 min. and rinsed in sterile water. Pathogenicity tests were performed by sprinkling 50 sclerotia, obtained from infected oat kernels (2), on the soil surface around the collar of each of 10 healthy, potted 1-year-old plants of laurustinus. Five of the plants were previously wounded on the crown 1.5 cm above or below the soil line with a sterile needle. Five noninoculated plants served as controls. All plants were maintained at 25 ± 2°C and enclosed for 72 hr in polyethylene bags (90 to 95% relative humidity). Blight symptoms similar to those seen in nursery were observed on inoculated plants 20 to 25 days after inoculation, while no symptoms developed on control plants. Koch's postulates were fulfilled by reisolation of the fungus on acidified PDA from all infected laurustinus plants. S. rolfsii was previously recorded on Prague viburnum (Viburnum × pragense L.) as the causal agent of southern blight (1). To our knowledge, this is the first report of southern blight caused by S. rolfsii on laurustinus.

References: (1) A. Hagan. Southern blight on flowers, shrubs, and trees. On-line publication ANR-1157. Alabama A & M, and Auburn University ( www.aces.edu/dept/extcomm/publications/html ). (2) R. Rodriguez-Kabana et al. Plant Dis. Rep. 59:5, 1975.
First Report of Downy Mildew on Basil (Ocimum basilicum) in Italy
Authors: Garibaldi A. , Minuto A. , Minuto G. , Gullino M. L.
Published: May 2007

Sweet basil (Ocimum basilicum) is an economically important herb in several Mediterranean countries. Approximately 80 ha are grown annually in Italy for fresh and processed consumption. In 2003, a damaging foliar disease was observed in several greenhouses located in the Liguria Region of northern Italy. More that 50% of the plants were affected. Leaves of infected plants were initially slightly chlorotic, especially near the central vein. Within 2 to 3 days, a characteristic gray, furry growth was evident on the lower surface of infected leaves. These symptoms sometimes occurred on the top sides of leaves. Although the distribution of the disease was generally uniform, symptoms appeared first in a patchy pattern in the central part of the greenhouses where air temperature and relative humidity were highest. Where air circulation was apparently poor, bottom leaves were severely affected by the disease. Microscopic observations revealed conidiophores branching two to seven times. Conidiophores with a length of 250 to 500 μm (average 350 μm) ended with sterigmata bearing single conidia. Conidia measured 15 to 25 × 20 to 35 μm (average 22 × 28 μm) and were elliptical and grayish in mass. The pathogen was identified as a Peronospora sp. based on its morphological characteristics (3). Pathogenicity was confirmed by inoculating leaves of 40-day-old healthy plants with a conidial suspension (1 × 105 conidia per ml). Three containers containing 150 plants each of O. basilicum cv. Genovese gigante were used as replicates. Noninoculated plants served as controls. Inoculated and noninoculated plants were maintained in a growth chamber at 20°C (12 h of light per day) and 90 to 95% relative humidity. The pathogenicity test was carried out twice. After 6 days, typical symptoms of downy mildew developed on the inoculated plants and a Peronospora sp. was observed on the leaves. Noninoculated plants did not show symptoms. To our knowledge, this is the first report of a Peronospora sp. on basil in Italy. Peronospora sp. and P. lamii were previously reported on sweet basil in Uganda (1,2).

References: (1) C. G. Hansford. Rev. Appl. Mycol. 12:421, 1933. (2) C. G. Hansford. Rev. Appl. Mycol. 17:345, 1938. (3) D. M. Spencer. The Downy Mildews. Academic Press, N.Y., 1978.
Survival of Tilletia indica Teliospores in Different Soils
Authors: Bonde M. R. , Berner D. K. , Nester S. E. , Peterson G. L. , Olsen M. W. , Cunfer B. M. , Sim T.
Published: May 2007

To determine the potential for Tilletia indica, cause of Karnal bunt of wheat, to survive and become established in new areas, a teliospore longevity study was initiated in Kansas, Maryland, Georgia, and Arizona. Soil from each location was infested with T. indica teliospores and placed in polyester mesh bags. The bags were placed within soil from the same location within polyvinyl chloride pipes. Pipes were buried in the respective plots such that the bags were at 5-, 10-, and 25-cm depths. Each pipe was open at the ends to allow interaction with the outside environment, however fitted with screens preventing possibility of teliospore escape. In the Karnal bunt-quarantine area of Arizona, bags of infested soil also were placed outside the pipes. Teliospore-infested soil from each location was maintained dry in a laboratory. During the first 2 years, viability declined more rapidly in pipes than outside pipes, and more rapidly in fields in Kansas and Maryland than in Georgia or Arizona. After 2 years, viability declined nearly equally. In the laboratory over 3 years, viability decreased significantly more rapidly in dry soil from Kansas or Maryland than in dry soil from Georgia or Arizona, while pure teliospores remained unchanged. We hypothesized that soils, irrespective of weather, affect teliospore longevity
Influence of Silicon and Chlorothalonil on the Suppression of Gray Leaf Spot and Increase Plant Growth in St. Augustinegrass
Authors: Brecht M. O. , Datnoff L. E. , Kucharek T. A. , Nagata R. T.
Published: May 2007

Silicon, applied as calcium silicate slag (20% Si), was evaluated for its potential to suppress gray leaf spot (Magnaporthe grisea) and increase plant growth in newly planted St. Augustinegrass in the summers of 2000 and 2001. Calcium silicate was applied (1,000 kg Si/ha) to three sites that contained Si-deficient Histosols prior to sprigging St. Augustinegrass, cv. Floratam, in southern Florida. This treatment was compared with foliar sprays of chlorothalonil, calcium silicate plus chlorothalonil, and an untreated control. Immediately after planting, applications of chlorothalonil (720 g/liter) were made every 10 days for a total of seven sprays at a rate of 7.6 kg a.i./ha with a commercial sprayer. Based on area under the disease progress curve (AUDPC) values for the treatments calcium silicate alone, chlorothalonil, and calcium silicate plus chlorothalonil, gray leaf spot was reduced by 7, 65, and 68% at site one, 28, 34, and 59% at site two, and 41, 55, and 68% at site three, respectively when compared with the untreated control. The application of calcium silicate alone significantly reduced the final AUDPC of gray leaf spot when compared with the control at site two only. However, when disease severities were analyzed by week, the calcium silicate treatment significantly reduced the percentage of disease at weeks 2, 6, and 8 at site one and weeks 3 to 8 at site three when compared with the control. The final percent bare ground coverage for St. Augustinegrass was increased significantly using calcium silicate by 17 and 34% over the control at sites one and two, respectively (P ≤ 0.05). Silicon was the only element to significantly increase in the leaf tissue for treatments amended with calcium silicate. Levels of Si in leaves for treatments amended with calcium silicate were from 1.2 to 1.3%, while those not receiving calcium silicate had only 0.6 to 0.7%. Amendments with calcium silicate slag for St. Augustinegrass sod production on Si-deficient soils may be an option to reduce gray leaf spot development in newly sprigged fields and promote earlier ground coverage of grass when the environment is favorable for disease.