bluuebunny/crossref_metadata_2025 huggingface dataset:
First Report of Colletotrichum acutatum in Blueberry Plants in Spain
Authors: Barrau C. , de los Santos B. , Romero F.
Published: May 2007

An anthracnose disease was observed affecting leaves of high-bush blueberry plants (Vaccinium corymbosum L. ‘Sharpblue’) in small areas within two production fields in Huelva Province of Andalucía, in southwestern Spain. The first symptoms observed in late spring were circular, necrotic lesions, red to salmon in color, and ranging from 3 to 20 mm in diameter. Later, lesions became salmon colored in the center with a brilliant red halo. Fungal isolations were made from the lesions. Infected tissues were surface-disinfected in 1% sodium hypochlorite for 1 min, blotted dry on sterile filter paper, and plated on 2% water agar. The plates were incubated at 25°C for 5 to 10 days. Fungal colonies isolated from the tissues were transferred to potato dextrose yeast agar (PDYA). Only one fungal species was consistently isolated from affected leaf tissues and was identified as Colletotrichum acutatum J.H. Simmonds based on morphological characteristics (2) and enzyme-linked immunosorbent assay (1). Colonies of the fungus on PDYA showed a white-to-gray dense mycelium covered with salmon-colored spore masses. The reverse of the plates was a pink-salmon color. Colony diameter on PDYA averaged 50 mm after 7 days at 25°C. Conidia were hyaline, aseptate, fusiform to cylindrical, and 12.5 × 3.2 μm. Inoculation of leaves and fruits of blueberry cv. Misty with a conidial suspension (106 conidia per ml) of C. acutatum produced lesions on the leaves and fruits similar to those observed on diseased plants in the field. The pathogen was isolated from lesions on inoculated plants. To our knowledge, this is the first report of C. acutatum in high-bush blueberry plants in Spain.

References: (1) T. A. Cooke et al. EPPO Bull. 25:57, 1995. (2) B. C. Sutton. The Coelomycetes. CMI, Kew, England, 1980.
First Report of Soybean Rust in South Africa
Authors: Pretorius Z. A. , Kloppers F. J. , Frederick R. D.
Published: May 2007

In February 2001, rust caused by Phakopsora pachyrhizi Syd. was detected for the first time on soybean (Glycine max (L.) Merr.) near Vryheid in northern KwaZulu-Natal, South Africa. As the season progressed, the disease was also observed in other parts of the province, and epidemic levels were reached in the Karkloof, Cedara, Howick, and Greytown production regions. In affected areas, infection foci gradually increased in size and caused premature yellowing and defoliation of soybean crops, usually after the flowering stage. Typical rust symptoms (3) were produced predominantly on the lower surface of soybean leaves. Soybean rust subsequently spread to Amsterdam and Ermelo in the Highveld region of South Africa. Following emergency registration of triazole compounds, fungicides were commonly used to control soybean rust, especially in the more humid eastern production areas. Available yield data suggested a reduction in kernel mass between 4 and 23%, depending on the cultivar and host growth stage at the time of infection. Urediniospores from the original collection (isolate PREM 57280, Plant Protection Research Institute, Pretoria, South Africa) were 23 to 33 × 15 to 22 μm, indicating that spore dimensions fell within the known range for P. pachyrhizi (3). To confirm pathogenicity, 10 to 15 plants of each of the South African soybean cvs. Pan 589, Pan 780, Pan 854, Octa, and Prima were inoculated with isolate PREM 57280. Primary leaves were sprayed with a suspension of spores in light mineral oil (approximately 1 mg of spores per ml) before incubating plants in the dark in a dew chamber for 16 h. Large, sporulating uredinia, producing typical soybean rust urediniospores, developed on all inoculated plants. Classical and real-time fluorescent polymerase chain reaction assays as well as sequence analysis of the internal transcribed spacer regions verified the identity of isolate PREM 57280 as P. pachyrhizi (2). Since the disease is known to occur in Zimbabwe, Mozambique, and several other African countries (1,3,4), inoculum was most likely introduced by air currents from countries to the north of South Africa. It is highly probable that soybean rust will successfully overwinter in South Africa based on experience in other southern African countries.

References: (1) O. A. Akinsanmi and J. L. Ladipo. Plant Dis. 85:97, 2001. (2) R. D. Frederick et al. (Abstr.) Phytopathology 90 (suppl):S25, 2000. (3) G. L. Hartman et al. eds. Compendium of Soybean Diseases, 4th ed. The American Phytopathological Society, St. Paul, MN, 1999. (4) J. B. Sinclair and G. L. Hartman, eds. Soybean Rust Workshop, Publ. 1 College of Agricultural, Consumer, and Environmental Sciences, National Soybean Research Laboratory, Urbana, IL. 1996.
First Report of the Root-Knot Nematode Meloidogyne ardenensis on Lady's Mantle in Norway
Authors: Holgado R. , Hammeraas B. , Karssen G.
Published: May 2007

In August 2000, several small galls were observed on roots of lady's mantle (Alchemilla acutiloba Opiz) from an old grassland near Kristiansund in northern Norway. These plants, without clear above-ground symptoms, were infected with an unknown root-knot nematode. Soil and plant samples were collected in July 2001 at the previous year's location and sent for identification to the Plant Protection Service in Wageningen, the Netherlands. The smooth elongated galls included several males, swollen adult females with protruding small egg masses and hatching second-stage juveniles. Males and second-stage juveniles also were isolated from adhering soil. The root-knot nematode was identified as Meloidogyne ardenensis Santos (1). Identification was based on female, male, and second-stage juvenile morphology and female isozyme electrophoresis with malate dehydrogenase and esterase. M. ardenensis parasitizes several dicotyledonous hosts, primarily herbaceous and woody plants, and is distributed throughout Europe, with Scotland the most northern area (2). To our knowledge, this is not only the first published report of M. ardenensis in Scandinavia, but also the first report of this species on lady's mantle.

References: (1) M. S. N. de A. Santos. Nematologica 13:593, 1968. (2) P. R. Thomas and D. J. F. Brown. Plant Pathol. 30:147, 1981.
Pepper huasteco virus and Pepper golden mosaic virus are Geminiviruses Affecting Tomatillo (Physalis ixocarpa) Crops in Mexico
Authors: Méndez-Lozano J. , Rivera-Bustamante R. F. , Fauquet C. M. , Torre-Almaraz R. De la
Published: May 2007

Whitefly-transmitted geminivirus diseases cause important losses in several horticultural crops in all areas in Mexico (1). Tomatillo is important in the Mexican diet since it is widely used to prepare many types of salsas and other dishes. As a result, tomatillo, also known as tomate verde (green tomato), is cultivated in 29 of 32 states in Mexico, with the main production areas located in the states of Morelos, Puebla, and Michoacán. Leaf samples of 105 tomatillo plants exhibiting yellowing, yellowing mosaic, leaf curl, bunchy top, and stunting were collected from the states of Puebla, Morelos, Estado de México, and Sinaloa. Symptomatic plants were associated with the presence of whiteflies in many fields and suggested a viral etiology. Total DNA extracted from symptomatic tomatillo plants was used as a template in a polymerase chain reaction (PCR)-based geminivirus detection procedure. MP16 and MP82 primers (2) were used to direct the amplification of a segment from the stem-loop structure in the intergenic region (IR) to a conserved region in the coat protein (CP) of begomoviruses (2). Sixty-nine percent (72/105) of the samples produced the expected PCR fragment (400 to 450 bp). Similar results were obtained with a dot-blot hybridization procedure using as a probe the component A of Pepper huasteco virus (PHV) under low stringency conditions. More than 50 PCR products were cloned and sequenced. Sequence analysis (nucleotide level for the IR; amino acid level for the CP) revealed that the tomatillo-infecting geminiviruses clustered into two main groups. The first group showed a high percent identity (average of 95.3% at the CP N terminus) to PHV, whereas the second showed a similarly high percent (average 93.8%) identity to Pepper golden mosaic virus (PepGMV, previously called Texas pepper geminivirus. Both PepGMV and PHV were found in all sampled areas. Although mixed infections (differentiated by the respective IR probes) of PHV and PepGMV were common (61%), single infections were also detected (PHV 27%; PepGMV 10%). The presence of begomoviruses in tomatillo crops has been previously reported (1); however, their identity as PHV and PepGMV was not confirmed.

References: (1) I. Torres-Pacheco et al. Phytopathology 86:1186, 1996. (2) P. Umaharan et al. Phytophatology 88:1262, 1998.
Occurrence of Potato Wart Caused by Synchytrium endobioticum on Prince Edward Island, Canada
Authors: De Boer S. H.
Published: May 2007

During harvest (October 2000) of a 26-ha field of processing potatoes (cv. Russet Burbank) on Prince Edward Island (PEI), a small number of tubers with symptoms of potato wart were found in a 1-ha area of the field. Resting sporangia of Synchytrium endobioticum were present in diseased tissue. Potato wart is not endemic in Canada outside of Newfoundland, where the disease has occurred since 1909, and has been under official quarantine control since 1912 (1). In the United States, the disease was eradicated from Pennsylvania and West Virginia by 1974 and, more recently, was eradicated from Maryland, where its presence had been reconfirmed in 1987 (2). Anecdotal information pertaining to the PEI field suggests that the source of infection may have been infected tubers from Newfoundland that were grown in this portion of the field many years ago. Cv. Russet Burbank is resistant to pathotype 1 which occurs in the United Kingdom, but is susceptible to pathotype 2, which predominates in Newfoundland (1). A soil survey confirmed the presence of S. endobioticum resting sporangia in the 1-ha area in which the symptomatic tubers were found. Concentrations of sporangia ranged from <1 to 124 sporangium per g of air-dried soil. Resting sporangia of S. endobioticum were not found in soil samples from fields within a 0.8-km radius of the infested field, nearby garden plots, or fields in which the same equipment had been used since 1984.

References: (1) M. C. Hampson. Can. J. Plant Pathol. 15:223, 1993. (2) M. L. Putnam and A. B. Sindermann. Am. Potato J. 71:743, 1994.
First Report of Pepino mosaic virus on Tomato in Spain
Authors: Jordá C. , Pérez A. Lázaro , Martínez-Culebras P. , Abad P. , Lacasa A. , Guerrero M. M.
Published: May 2007

At the beginning of 2000, a damaging disease developed on protected tomato (Lycopersicon esculentum) crops grown in polyethylene greenhouses in different regions of Spain. Production losses were estimated at 15 to 80%. The tomato plants showed a variety of symptoms. The most common symptoms were leaf distortion, chlorosis, and mosaic. Some plants showed a dark green mosaic and bubbling of the leaf surface. Green striations were also observed on the stem and sepals. Most of the diseased plants had discolored fruits. Symptoms decreased as environmental temperature increased. The involvement of Pepino mosaic virus (PepMV) was suspected. To identify the etiological agent, ≈500 symptomatic tomato plants were collected from several locations in Alicante, Murcia, Almeria and the Canary Islands. Flexuous viral particles 510 nm long were observed by transmission electron microscopy, suggesting the presence of a potexvirus in the tissue extracts analyzed. All samples were tested by ELISA (enzyme-linked immunosorbent assay), using polyclonal antibodies to Narcissus mosaic virus (Adgen, Auchincriuve, Scotland), a virus serologically related to PepMV, and two antisera specific to PepMV (Adgen, Scotland and DMSZ, Braunschweig, Germany). PepMV was detected in 35% of the samples. Like PepMV, the virus infected (as confirmed by ELISA) greenhouse-grown Datura stramonium, Nicandra physalodes, Nicotiana benthamiana, N. clevelandii, Solanum tuberosum, and Vigna sinensis and did not infect Capsicum anuum, Cucumis sativus, Chenopodium amaranticolor, C. quinoa, Petunia × hybrida, Phaseolus vulgaris, Physalis floridana, N. glutinosa, N. rustica, or N. tabacum. The virus did infect Gomphrena globosa, which normally is not infected by PepMV. The first report of PepMV was on pepino (Solanum muricatum) in Peru in 1974 (1), but this virus has been recently reported in the Netherlands, England, Germany, and France on protected tomato crops (2). To our knowledge, this is the first report of PepMV in Spain, including the Canary Islands.

References: (1) R. A. C. Jones et al. Ann. Appl. Biol. 94:61, 1980. (2) European and Mediterranean Plant Protection Organisation (EPPO). Alert List Viruses. On-line publication/2000/003.
Effects of Powdery Mildew on Vine Growth, Yield, and Quality of Concord Grapes
Authors: Gadoury David M. , Seem Robert C. , Pearson Roger C. , Wilcox Wayne F. , Dunst Richard M.
Published: May 2007

Vitis labruscana ‘Concord’ is a widely planted grape cultivar grown in the United States for processing into juice and other products. Concord fruit are sporadically but sometimes severely damaged by the grape powdery mildew pathogen, Uncinula necator. The effects of powdery mildew on vine growth, yield, and quality of Concord grapes at three levels of cropping intensity commonly found in commercial grape production were determined in vineyard studies. Top-wire cordon-trained Concord vines were balance pruned, pruned to retain 80 nodes, or minimally pruned. Replicated plots of the foregoing were then either protected from powdery mildew by regular fungicide applications, or were inoculated and left unsprayed. Over a 4-year period, the effects of foliar infection on vine growth, yield, and juice quality of unsprayed vines were compared with vines that received a conventional protection program of four fungicide applications. Failure to control powdery mildew resulted in a chronic reduction in wood maturity measured as the number of nodes on canes that developed periderm. The reduction in nodes did not reduce yield, possibly due to compensation in shoots produced from the remaining nodes. Powdery mildew did not affect bud survival or vigor, measured as the number of shoots produced per node on retained canes. The most significant effects of powdery mildew were on berry sugar levels and juice color and acidity, which on the unsprayed vines were sometimes reduced below minimally acceptable thresholds for processed grapes. Significant reductions due to powdery mildew in these parameters occurred in all three pruning treatments, but were most pronounced at higher cropping levels.
Reaction of Broccoli to Isolates of Verticillium dahliae from Various Hosts
Authors: Bhat R. G. , Subbarao K. V.
Published: May 2007

Isolates of Verticillium dahliae from 15 different hosts and V. albo-atrum from alfalfa were tested for their ability to cause wilt on broccoli using a root-dip inoculation method. None of the isolates caused vascular discoloration in broccoli except those from cabbage and cauliflower that were weakly pathogenic. Broccoli cultivars Baccus, Greenbelt, Parasol, Patriot, and Symphony showed resistance to Verticillium infection. Re-isolated strains from fresh samples of internally discolored broccoli and cauliflower root tissues were unable to cause disease symptoms on re-inoculation of broccoli, but caused severe disease on cauliflower. Inoculation of 5-, 7-, 9-, or 11-week-old plants did not alter the resistance in broccoli or the susceptibility in cauliflower against Verticillium. Immunity of broccoli against infection by isolates of V. dahliae from non-crucifer hosts, its resistance against crucifer isolates, and as previously described, attrition of V. dahliae microsclerotia in soil by broccoli residue, coupled with its importance as a commercial vegetable, make broccoli an attractive rotation crop for the management of Verticillium wilt in many cropping systems.
Resistance Genes in the rp1 Region of Maize Effective Against Puccinia sorghi Virulent on the Rp1-D Gene in North America
Authors: Pataky Jerald K. , Pate Molly C. , Hulbert Scot H.
Published: May 2007

Resistance in sweet corn conferred by the Rp1-D gene has controlled common rust, caused by Puccinia sorghi, in North American corn for nearly 15 years. Eleven isolates of P. sorghi virulent on corn with the Rp1-D gene were collected from Rp-resistant corn in 1999 from Wiscon-sin, Illinois, New York, and Minnesota. Isolates were increased on susceptible sweet corn. Urediniospores of nine isolates were bulked. Reactions of individual Rp genes in the rp1 region and reactions of linked combinations of Rp genes in the rp1 region (i.e., compound rust resistance genes) were evaluated against the bulked population of P. sorghi in several greenhouse trials. Reactions of individual and compound Rp genes also were evaluated against individual isolates of P. sorghi. Each trial contained at least two replicates of several lines with Rp genes and one susceptible check. Five to 10 two-leaved seedlings per line were inoculated at least twice with a suspension of urediniospores. Ten days after inoculation, rust reactions were rated:+ = sporulating uredinia, - = no sporulating uredinia, and I = chlorotic or necrotic tissue surrounding small uredinia. Four single genes, Rp1-E, Rp-G, Rp1-I, and Rp1-K, and eight compound genes, Rp1-JFC, Rp1-JC, Rp-GI, Rp-G5, Rp-GDJ, Rp-G5JD, Rp-G5JC, and Rp-GFJ, conferred resistance. Additional characterization of virulence in North American populations of P. sorghi that are avirulent against Rp1-D is necessary to determine if these genes will be as widely effective as the Rp1-D gene has been. Two subpopulations of P. sorghi were detected from the bulked population after it was sequentially cultured for at least five cycles on seedlings with Rp1-C or with Rp1-J. The subpopulation cultured on Rp1-J was avirulent on lines with Rp1-C/L/N, Rp1-B, and Rp1-M; whereas the subpopulation cultured on Rp1-C was virulent on lines with each of these genes. Both subpopulations were virulent on lines with Rp1-D.
Apple dimple fruit viroid: Fulfillment of Koch's Postulates and Symptom Characteristics
Authors: Serio F. Di , Malfitano M. , Alioto D. , Ragozzino A. , Desvignes J. C. , Flores R.
Published: May 2007

The previously reported properties of a small circular RNA isolated from plants of cultivar Starking Delicious with symptoms similar to those of the dapple apple disease induced by Apple scar skin viroid (ASSVd), strongly suggested that it is a distinct viroid species of genus Apscaviroid to which ASSVd also belongs. Nevertheless, the autonomous replication of this novel RNA, termed Apple dimple fruit viroid (ADFVd), and the nature of the symptoms incited when inoculated free of other pathogens that might be present in the original source, were not determined. We addressed these questions by mechanically inoculating purified ADFVd into young apple seedlings (Golden). Dot blot hybridization of leaf extracts collected ten months after inoculation showed the presence of ADFVd in most of the inoculated seedlings, thus proving the ability of this RNA to replicate independently. Material from these ADFVd-infected seedlings grafted onto the ASSVd indicator Starkrimson incited the appearance on the fruit skin of discolored spots more or less depressed which were particularly frequent around the calyx cavity. Apple cultivars such as Gala, Pink Lady, and Braeburn reacted to ADFVd with similar symptoms, occasionally accompanied by scar skin in Braeburn, whereas ADFVd replicated without eliciting any visible symptoms in other apple cultivars such as Golden, or in the pear indicator Fieud 37. No interference in symptom expression or viroid accumulation were observed in plants inoculated first with ASSVd and then with ADFVd.
Resistance of Botryosphaeria dothidea from Pistachio to Iprodione
Authors: Ma Zhonghua , Luo Yong , Michailides Themis J.
Published: May 2007

Out of 79 field-collected isolates of Botryosphaeria dothidea, causal agent of panicle and shoot blight of California pistachio, 1 had low resistance to the dicarboximide fungicide iprodione (effective fungicide concentration to inhibit 50% of mycelial growth [EC50] = 2.726 μg/ml), whereas all the other isolates were sensitive (EC50 < 1 μg/ml). B. dothidea isolates readily developed resistance to iprodione in vitro. Furthermore, these in vitro-derived iprodione-resistant (IR) isolates retained high virulence on pistachio. The EC50 values for these IR isolates were greater than 25 μg/ml, whereas the EC50 values for the original wild-type counterparts were less than 1 μg/ml. Iprodione resistance significantly declined when these IR isolates were propagated on pistachio leaves in the absence of the fungicide. IR isolates also were resistant to vinclozolin, another dicarboximide fungicide, but sensitive to tebuconazole and benomyl. IR isolates showed an increase in osmotic sensitivity on media amended with NaCl. Applications of iprodione at 500 μg/ml, which is effective against naturally sensitive isolates, failed to control disease caused by IR isolates in both the laboratory and greenhouse. The results indicate that, although naturally occurring IR isolates of B. dothidea may be rare in California pistachio orchards, the fungus readily develops resistance to iprodione in vitro and, more importantly, retains high levels of virulence on pistachio.
Resistance to Bacterial Spot in Bell Pepper Induced by Acibenzolar-S-Methyl
Authors: Romero A. M. , Kousik C. S. , Ritchie D. F.
Published: May 2007

Bell pepper plants sprayed with the chemical acibenzolar-S-methyl (ABM, Actigard 50 WG) showed resistance to subsequent infections with the bacterial spot agent Xanthomonas axonopodis pv. vesicatoria. Induction of resistance was independent of the cultivar used, and was expressed as early as 3 days after treatment and continued for at least 2 weeks. In the field, applications of ABM every 2 weeks, alone or in combination with copper, resulted in disease control similar to the standard treatment of copper plus maneb. Yield response was variable, with certain combinations of chemical treatments and cultivars producing yields as large as the copper plus maneb treatment. In contrast, weekly applications during the entire crop season had a negative impact on yield. In plots maintained free of bacterial spot, applications of ABM every 2 weeks caused a reduction in yield for one cultivar of six tested. The use of chemical inducers for the control of bacterial spot on bell pepper, while generally promising, may result in an unpredictable loss in fruit yield.
Characterization of a Virus from Pigeonpea with Affinities to Species in the Genus Aureusvirus, Family Tombusviridae
Authors: Kumar P. Lava , Jones A. T. , Sreenivasulu P. , Fenton B. , Reddy D. V. R.
Published: May 2007

In attempts to identify the causal agent of pigeonpea sterility mosaic disease (PSMD), which is transmitted by eriophyid mites, a virus was isolated with great difficulty from some PSMD-affected pigeonpea (Cajanus cajan) plants from different locations in India. Once isolated from pigeonpea, the virus was transmitted readily by mechanical inoculation to several herbaceous species, reaching very high concentrations in some species. The virus was transmitted experimentally through soil to herbaceous test plants but not to pigeonpea. When virus particles were purified and inoculated mechanically to healthy pigeonpea, the virus induced necrosis in inoculated leaves only and did not spread systemically. Therefore, the virus is not the causal agent of PSMD. The virus has isometric particles approximately 30 nm in diameter that sediment as a single component and had a buoyant density in CsCl and Cs2SO4 of 1.34 and 1.27 g·cc-1, respectively. Purified virus particle preparations contained a single major protein of approximately 44 kDa and three RNA species of approximately 4,300, 2,700, and 1,500 nucleotides. Only the largest RNA species was infective to plants; the two smaller species were encapsidated subgenomic species of the 3′ end of the larger genomic RNA. The viral genome was sequenced and showed 93% homology to that of Pothos latent virus (PoLV), a recently described virus in the genus Aureusvirus, family Tombusviridae, and was indistinguishable from PoLV in gel double-diffusion serological tests. This virus, therefore, is regarded as a pigeonpea isolate of PoLV (PoLV-PP). In field studies in different locations in India, enzyme-linked immunosorbent assay and reverse-transcriptase polymerase chain reaction detected PoLV-PP in 10.7% of PSMD-affected and 8.1% of asymptomatic pigeonpea plants. The significance of these findings is discussed.
Characterization of Capsicum chinense Cultigens for Resistance to Meloidogyne arenaria, M. hapla, and M. javanica
Authors: Thies Judy A. , Fery Richard L.
Published: May 2007

Four Capsicum chinense cultigens with known reactions to Meloidogyne incognita were characterized for resistance to M. arenaria races 1 and 2, M. hapla, and M. javanica, in greenhouse and growth-chamber tests. The M. incognita-resistant cultigens PA-353, PA-398, and PA-426 exhibited high resistance to M. arenaria race 1; the M. incognita-susceptible PA-350 was susceptible to M. arenaria race 1. M. arenaria race 2 and M. javanica were not highly pathogenic to any of the C. chinense cultigens. PA-353, PA-398, and PA-426, however, supported an average of 98.1 and 94.8% fewer (P < 0.05) M. arenaria race 2 and M. javanica eggs per gram fresh root, respectively, than PA-350. M. hapla was pathogenic to all four C. chinense cultigens. PA-353, PA-398, and PA-426 will be useful sources of resistance to M. arenaria races 1 and 2, M. javanica, and M. incognita, for developing resistant habanero pepper cultivars; however, an alternative source of resistance must be identified for M. hapla.
Resistance of Sugarcane Cultivar R 570 to Puccinia melanocephala Isolatesfrom Different Geographic Locations
Authors: Asnaghi C. , D'Hont A. , Glaszmann J. C. , Rott P.
Published: May 2007

Two different inoculation techniques were investigated before studying the reaction of the major rust resistance gene of sugarcane cultivar R 570 against isolates of Puccinia melanocephala from different geographic locations. Cultivar R 570 exhibited severe rust symptoms when in vitro plantlets were inoculated with a rust isolate from Réunion Island, but a good correlation with field resistance was observed when detached leaves were inoculated with the pathogen. This latter technique was then used to inoculate R 570 and a sample of its self progeny with rust isolates from Brazil, Colombia, Florida (three isolates), Guadeloupe, Réunion Island, and Zimbabwe. R 570 was resistant to all isolates of P. melanocephala, and the segregation of resistance in the progeny did not change with the isolates, suggesting that a single gene, or a single chromosomic region, was involved in the resistance against all tested isolates. This major resistance gene has, therefore, potential value to improve resistance to rust in various geographic regions.
Molecular Identification and Classification of a Phytoplasma Associated with Phyllody of Strawberry Fruit in Maryland
Authors: Jomantiene R. , Maas J. L. , Davis R. E. , Dally E. L.
Published: May 2007

Several phytoplasmas have been reported to be associated with phyllody of strawberry fruit, including clover yellow edge, clover proliferation, clover phyllody, eastern and western aster yellows, STRAWB2, strawberry multicipita, and Mexican periwinkle virescence phytoplasmas. Plant symptoms in addition to phyllody may include chlorosis, virescence, stunting, or crown proliferation. In this report we describe a new phytoplasma in association with strawberry leafy fruit (SLF) disease in Maryland. Diseased plants exhibited fruit phyllody, floral virescence, leaf chlorosis, and plant stunting. Phytoplasmal 16S rDNA was amplified from SLF diseased plants by using the polymerase chain reaction (PCR) primed by primer pair P1/P7 and was reamplified in nested PCR primed by primer pair R16F2n/R2 (F2n/R2) as previously described (1). These results indicated the presence of a phytoplasma, designated SLF phytoplasma. Identification of SLF phytoplasma was accomplished by restriction fragment length polymorphism (RFLP) analysis of DNA amplified in PCR primed by F2n/R2, using endonuclease enzyme digestion with AluI, HhaI, KpnI, HaeIII, MseI, HpaII, RsaI, and Sau3AI. Phytoplasma classification was done according to the system of Lee et al. (2). RFLP analyses of rDNA amplified in three separate PCRs gave identical patterns. On the basis of collective RFLP patterns of the amplified 16S rDNA, the SLF phytoplasma was classified as a member of group 16SrIII (group III, X-disease phytoplasma group). The HhaI RFLP pattern of SLF 16S rDNA differed from that of the apparently close relative, clover yellow edge (CYE) phytoplasma, and all other phytoplasmas previously described in group III. Based on these results, SLF phytoplasma was classified in a new subgroup, designated subgroup K (III-K), within group III. The 1.2 kbp DNA product of PCR primed by primer pair F2n/R2 was sequenced, and the sequence deposited in GenBank under Accession No. AF 274876. Results from putative restriction site analysis of the sequence were in agreement with the results from actual enzymatic RFLP analysis of rDNA amplified from phylloid strawberry fruit. Although the sequence similarity between the 1.2-kbp fragment from the 16S rDNA of SLF phytoplasma and that of CYE phytoplasma was 99.9%, the Hha1 RFLP pattern of SLF rDNA supports the conclusion that the SLF phytoplasma may be closely related to, but is distinct from, CYE and other strains that are classified in group III. These findings contribute knowledge about the diversity of phytoplasmas affiliated with group III and the diversity of phytoplasmas associated with diseases in strawberry.

References: (1) R. Jomantiene et al. Int. J. Syst. Bacteriol. 48:269, 1998. (2) I.-M. Lee et al. Int. J. Syst. Bacteriol. 48:1153, 1998.
Control of Postharvest Blue and Green Molds of Oranges by Hot Water, Sodium Carbonate, and Sodium Bicarbonate
Authors: Palou Lluís , Smilanick Joseph L. , Usall Josep , Viñas Inmaculada
Published: May 2007

Control of citrus blue mold, caused by Penicillium italicum, was evaluated on artificially inoculated oranges immersed in water at up to 75°C for 150 s; in 2 to 4% sodium carbonate (wt/vol) at 20 or 45°C for 60 or 150 s; or in 1 to 4% sodium bicarbonate at room temperature for 150 s, followed by storage at 20°C for 7 days. Hot water controlled blue mold at 50 to 55°C, temperatures near those that injured fruit, and its effectiveness declined after 14 days of storage. Sodium carbonate and sodium bicarbonate were superior to hot water. Temperature of sodium carbonate solutions influenced effectiveness more than concentration or immersion period. Sodium carbonate applied for 150 s at 45°C at 3 or 4% reduced decay more than 90%. Sodium bicarbonate applied at room temperature at 2 to 4% reduced blue mold by more than 50%, while 1% was ineffective. In another set of experiments, treatments of sodium bicarbonate at room temperature, sodium carbonate at 45°C, and hot water at 45°C reduced blue mold incidence on artificially inoculated oranges to 6, 14, and 27%, respectively, after 3 weeks of storage at 3°C. These treatments reduced green mold incidence to 6, 1, and 12%, respectively, while incidence among controls of both molds was about 100%. When reexamined 5 weeks later, the effectiveness of all, particularly hot water, declined. In conclusion, efficacy of hot water, sodium carbonate, and sodium bicarbonate treatments against blue mold compared to that against green mold was similar after storage at 20°C but proved inferior during long-term cold storage.
Variation Among Isolates of Fusarium graminearum Associated with Fusarium Head Blight in North Carolina
Authors: Walker Scott L. , Leath Steven , Hagler Winston M. , Murphy J. Paul
Published: May 2007

Fusarium head blight (FHB) can reduce yield of wheat and decrease the value of harvested grain by accumulation of detrimental toxins. Understanding the variability of the fungal population associated with infection could improve disease control strategies. Sixty-six isolates of Fusarium graminearum associated with FHB were collected in North Carolina and tested for in vitro growth rate, in vitro production of deoxynivalenol (DON) and zearalenone, and pathogenicity on three cultivars of soft red winter wheat. Significant differences among isolates were found for all three traits. Randomly Amplified Polymorphic DNA (RAPD) analysis revealed high levels of genotypic diversity among isolates. Isolates of F. graminearum, F. culmorum, and F. avenaceum acquired from the Pennsylvania State University Fusarium Center were included for comparison in all tests. In vivo levels of DON were measured for the five isolates associated with the highest levels of disease and the five isolates associated with the lowest levels of disease, and no significant differences were found. However, all ten isolates produced detectable levels of DON in vivo. Mean disease ratings ranged from 3.4 to 96.4%, in vitro (DON) levels ranged from 0 to 7176.2 ppm, and zearalenone ranged from 0 to 354.7 ppm, among isolates. A multiple regression model using in vitro growth, in vitro DON, and zearalenone production, collection location, wheat cultivar of isolate origin, plot, tillage conditions, and previous crop as independent variables and percent blighted tissue as the dependent variable was developed. The cumulative R2 value for the model equaled 0.27 with in vitro rate of growth making the largest contribution. Analysis of phenotype and genotype among isolates demonstrated diversity in a single plot, in a single location, and in North Carolina. Genotypic and phenotypic diversity were significant under both conventional and reduced tillage conditions, and diversity was high regardless of whether the previous crop had been a host or non-host for F. graminearum. These data indicate a variable pathogen population of F. graminearum exists in North Carolina, and members of this population can be both highly pathogenic on wheat and produce high levels of detrimental toxins, indicating a potential threat for problems with FHB within the state.
Identity and Pathogenicity of Two Phytophthora Taxa Associated with a New Root Disease of Olive Trees
Authors: Sánchez-Hernández Esperanza , Muñoz-García Mónica , Brasier Clive M. , Trapero-Casas Antonio
Published: May 2007

Fifty-two Phytophthora isolates from necrotic roots of olives were characterized. Colony morphologies on carrot-agar medium led us to separate them into two groups: A (36 isolates) and B (16 isolates). The optimum growth temperature for Group A was about 21°C, with slow growth at 30°C. In contrast, Group B isolates had an optimum temperature for growth of 26°C, and grew rapidly at 30°C. Growth rates, sporangial and oogonial characteristics of the Group A isolates conformed to P. megasperma “BHR-type” sensu stricto. This designation was supported by a sequence analysis of their ITS rDNA regions. Colony patterns, sporangial characteristics and temperature-growth relationships of the Group B isolates conformed closely to those of the ‘O-group’ taxon of Phytophthora. They also conformed to this unusual taxon in their ITS sequence. In addition, Group B isolates were either entirely self-sterile, self-sterile A1s or weakly self-fertile. Pathogenicity tests showed that both taxa were highly aggressive on roots of olive trees. The association of flooding with Phytophthora infection indicates that the previously reported high sensitivity of olive to root asphyxiation may be more properly regarded as root-rot caused by Phytophthora spp.
Impact of Powdery Mildew and Leaf Rust on Milling and Baking Quality of Soft Red Winter Wheat
Authors: Everts Kathryne L. , Leath Steven , Finney Patrick L.
Published: May 2007

Changes in milling and baking quality (especially flour yield) of soft red winter wheat can have a large economic impact on flour mills. To determine the relationship between early-season powdery mildew and late-season leaf rust on flour yield, flour protein, alkaline water retention capacity, and kernel texture (softness equivalent), a study was conducted over 2 years at Kinston and Plymouth, NC. Different levels of powdery mildew and leaf rust developed on three winter wheat cultivars that varied in levels of disease resistance, the presence of seed treatment, and the presence and timing of foliar fungicide application. In Kinston and Plymouth in 1989-90, where leaf rust occurred early, the softness equivalent score was lower in wheat grown from seed treated with triadimenol. The following year, when the leaf rust epidemic increased later, foliar fungicide application reduced disease and resulted in lower softness equivalent scores in both Plymouth and Kinston for cv. Saluda and in Kinston for cv. Coker 983. A regression model was developed to describe the relationship between the log of the area under the disease progress curves and adjusted flour yield (AFY). The AFY of Saluda was reduced in the presence of powdery mildew such that %AFY = 103.96 - 0.92 (log AUMPC).
First Report of Tomato Spotted Wilt Virus on Potatoes in Iran
Authors: Pourrahim R. , Farzadfar Sh. , Moini A. A. , Shahraeen N. , Ahoonmanesh A.
Published: May 2007

Severe leaf and stem necrosis before flowering was observed in potato (Solanum tuberosum) fields of Firouzkoh Province, Iran, during the summer of 1998. Infected plants died before the end of the growing season. Necrosis was more severe in cv. Agria than in cvs. Ajaxs and Arinda. A high population of Thrips tabaci was observed in August and September. Tomato spotted wilt virus (TSWV) (1) was detected in affected potatoes by using specific TSWV-IgG (from Bioreba) in double-antibody sandwich enzyme linked immunosorbent assay and by indicator plant reactions. Mechanical inoculation of indicator plants with leaf extracts of symptomatic potatoes produce necrotic local lesions in Chenopodium quinoa, C. amaranticolor, Gomphrena globosa, Vicia faba, Vigna sinensis, Phaseolus aureus var. Gohar, P. vulgaris, and Petunia hybrida. The virus caused systemic necrosis in Capsicum frutescens, Datura stramonium, D. metel, Nicotiana glutinosa, N. rustica, and Trapaeolum majus, preceded by systemic chlorotic spots. TSWV was reported from ornamental crops in Tehran and Absard areas near to Firouzkoh province (2), but this is the first report of TSWV occurrence on potatoes in Iran.

References: (1) T. S. Ie. Descriptions of Plant Viruses. No. 39, 1970. (2) A. A. Moeini, et al. Iran. J. Plant Pathol. (In press.)
Outbreaks of Soybean Frogeye Leaf Spot in Iowa
Authors: Yang X. B. , Uphoff M. D. , Sanogo S.
Published: May 2007

Frogeye leaf spot of soybean, caused by Cercospora sojina, is typically a disease of warm and humid regions (2). Although the disease was reported in the Midwest in the 1920s (1), no outbreaks have been recorded in Iowa. Outbreaks of frogeye leaf spot occurred during 1999 in soybean fields in Ames and Grand Junction in central Iowa. During the 2000 growing season, the disease occurred in southwestern, southcentral, central, southeastern, and east-central Iowa. Occurrences of the disease with severity (reduction of green leaf area) greater than 50% were observed in production soybean fields at Grand Junction in central Iowa and Central City in eastern Iowa. In a 12-ha no-till field planted with cv. Asgrow 2501, the disease was noticeable and uniformly distributed in the entire field in mid July. Disease severity in this field was greater than 70% by the end of August. Disease incidence, however, was less than 10% in three adjacent soybean fields. In a soybean performance test at a central Iowa location where the disease occurred in 1999 and 2000, the disease was observed on all 80 varieties, with four having a severity equal to or greater than 40%. Fourteen entries had less than a 10% disease severity and 19 entries had a disease severity equal to or greater than 30%. Infected leaves in these locations had typical lesions of frogeye leaf spot, which appeared as reddish brown margins surrounding light brown or ash gray centers. On the infected tissues, hyaline, straight, and multiseptate conidia from clustered conidiophores were found, isolated, and identified to C. sojina. The relatively warm winter temperatures in 1998 to 1999 and 1999 to 2000 were associated with frogeye leaf spot epidemics. Because of the seedborne nature of C. sojina, efforts are warranted to monitor and survey the occurrence of frogeye leaf spot in Iowa, an important seed production state in the northern soybean production region.

References: (1) K. Athow and A. H. Probst. Phytopathology 42:660–662, 1952. (2) D. V. Phillips. 1999. Pages 20–21 in: Soybean Disease Compendium. Hartman et al. eds, American Phytopathological Society. St. Paul, MN.
First Report of an Aster Yellows Phytoplasma Associated with Cabbage in Southern Texas
Authors: Lee I.-M. , Dane R. A. , Black M. C. , Troxclair Noel
Published: May 2007

In early spring 2000 carrot crops in southwestern Texas were severely infected by an outbreak of phyllody associated with aster yellows phytoplasma. Cabbage crops that had been planted adjacent to these carrot fields began to display previously unobserved symptoms characteristic of phytoplasma infection. Symptoms included purple discoloration in leaf veins and at the outer edges of leaves on cabbage heads. Proliferation of sprouts also occurred at the base of the stem and between leaf layers of some plants, and sprouts sometimes continued to proliferate on extended stems. About 5% of cabbage plants in the field exhibited these symptoms. Two symptomless and four symptomatic cabbage heads were collected in early April from one cabbage field. Veinal tissues were stripped from each sample and used for total nucleic acid extraction. To obtain specific and sufficient amount of PCR products for analysis, nested PCR was performed by using primer pairs (first with P1/P7 followed by R16F2n/R16R2) (1,2) universal for phytoplasma detection. A specific 16S rDNA fragment (about 1.2 kb) was strongly amplified from the four symptomatic but not from the two asymptomatic samples. The nested PCR products obtained from the four symptomatic samples were then analyzed by restriction fragment length polymorphism (RFLP) using the restriction enzymes MseI, HhaI, and HpaII, and the RFLP patterns were compared to the published patterns of known phytoplasmas (1). The resulting RFLP patterns were identical to those of a phytoplasma belonging to subgroup B of the aster yellows phytoplasma group (16SrI). These RFLP patterns were also evident in putative restriction sites observed in a 1.5 kbp nucleotide sequence of the 16S rDNA. This is the first report of aster yellows phytoplasma associated disease symptoms in cabbage in Texas. The occurrence of cabbage proliferation coincided with the presence of high populations of the insect vector, aster leafhopper.

References: (1) I.-M. Lee et al. Int. J. Syst. Bacteriol. 48:1153, 1998. (2) B. Schneider et al. 1995. Molecular and Diagnostic Procedures in Mycoplasmology, Vol. I. Academic Press, San Diego, CA.
Distribution and Characteristics of Groundnut Rosette Disease in Kenya
Authors: Wangai A. W. , Pappu S. S. , Pappu H. R. , Deom C. M. , Naidu R. A.
Published: May 2007

Groundnut rosette is a major virus disease of peanut in sub-Saharan Africa. The disease is caused by a complex of three agents: GRAV (groundnut rosette assistor luteovirus), GRV (groundnut rosette umbravirus), and the associated satellite RNA (Sat-RNA). During the 1997 to 1998 crop season, the incidence of rosette in farmers' fields was estimated at 24 to 40% in western Kenya and 30% in the Rift Valley. Sequence analysis of Kenyan isolates revealed that GRAV-CP sequences shared 97 to 100% and 95 to 98% sequence homology at nucleotide and amino acid levels, respectively, amongst themselves and with the Malawian and Nigerian isolates. The ORFs 3 and 4 of GRV were similar, with a homology of 99% at the nucleotide and amino acid levels among Kenyan isolates. The GRV sequences of Kenyan isolates were closer to the Malawian (95 to 96%) than to the Nigerian (87 to 88%) isolates. Sat-RNA shared 89 to 94% nucleotide identity with those from Malawi and Nigeria. A closer sequence relationship was observed between Kenyan and Malawian isolates in all regions compared. This is the first report on the distribution and molecular characterization of groundnut rosette disease complex in East Africa.
Field Control of Bacterial Spot and Bacterial Speck of Tomato Using a Plant Activator
Authors: Louws F. J. , Wilson M. , Campbell H. L. , Cuppels D. A. , Jones J. B. , Shoemaker P. B. , Sahin F. , Miller S. A.
Published: May 2007

Acibenzolar-S-methyl (CGA 245704 or Actigard 50WG) is a plant activator that induces systemic acquired resistance (SAR) in many different crops to a number of pathogens. Acibenzolar-S-methyl was evaluated for management of bacterial spot (Xanthomonas axonopodis pv. vesicatoria) and bacterial speck (Pseudomonas syringae pv. tomato) of tomato in 15 and 7 field experiments, respectively. Experiments were conducted over a 4-year period in Florida, Alabama, North Carolina, Ohio, and Ontario using local production systems. Applied at 35 g a.i. ha-1, acibenzolar-S-methyl reduced foliar disease severity in 14 of the 15 bacterial spot and all 7 bacterial speck experiments. Disease control was similar or superior to that obtained using a standard copper bactericide program. Acibenzolar-S-methyl also reduced bacterial fruit spot and speck incidence. Tomato yield was not affected by using the plant activator in the field when complemented with fungicides to manage foliar fungal diseases, but tomato transplant dry weight was negatively impacted. X. axonopodis pv. vesicatoria population densities on greenhouse-grown tomato transplants were reduced by acibenzolar-S-methyl treatment. Bacterial speck and spot population densities on leaves of field-grown plants were not dramatically affected. Acibenzolar-S-methyl can be integrated as a viable alternative to copper-based bactericides for field management of bacterial spot and speck, particularly where copper-resistant populations predominate.
Interactions Between Xanthomonas campestris pv. graminis Strains and Meadow Fescue and Italian Rye Grass Cultivars
Authors: Michel V. V.
Published: May 2007

Eleven strains of Xanthomonas campestris pv. graminis, causal agent of grass bacterial wilt, collected over 20 years, varied significantly (P < 0.001) in their aggressiveness on meadow fescue and Italian rye grass. Aggressiveness of strains isolated since 1993 was not higher than strains isolated from 1975 to 1984. Significant interactions (P < 0.001) between X. campestris pv. graminis strains and cultivars occurred for meadow fescue but not for Italian rye grass (P =0. 934). Inoculation with a single, highly aggressive strain for breeding of meadow fescue proved to be useful to increase the resistance to bacterial wilt, but improvement became stagnant after an initial strong increase in resistance level. Furthermore, a possible breakdown of the resistance of meadow fescue cultivars when grown in exotic environments might be possible. Therefore, the use of a strain mixture for breeding of meadow fescue is recommended.