bluuebunny/crossref_metadata_2025 huggingface dataset:
A Polymerase Chain Reaction Protocol for the Detection of Clavibacter xyli subsp. xyli, the Causal Bacterium of Sugarcane Ratoon Stunting Disease
Authors: Pan Y.-B. , Grisham M. P. , Burner D. M. , Damann K. E. , Wei Q.
Published: May 2007

A polymerase chain reaction (PCR) protocol was developed that specifically detected Clavibacter xyli subsp. xyli, the causal agent of sugarcane ratoon stunting disease. Generic PCR products from the intergenic transcribed spacer (ITS) region of 16S-23S ribosomal DNA of C. xyli subsp. xyli and C. xyli subsp. cynodontis were cloned and sequenced. Based on a multiple sequence alignment among these two sequences and other nonredundant highly homologous sequences from the database, two C. xyli subsp. xyli-specific PCR primers were designed, Cxx1 (5′ CCGAAGTGAGCAGATTGACC) and Cxx2 (5′ ACCCTGTGTTGTTTTCAACG). These two 20-mer oligonucleotides primed the specific amplification of a 438-bp DNA product from genomic DNA samples of 21 C. xyli subsp. xyli strains. Amplification was not observed with genomic DNA of one C. xyli subsp. cynodontis strain, five strains of four other Clavibacter species, and two strains of two Rathayibacter species. The 438-bp PCR product also was amplified directly from cultured C. xyli subsp. xyli cells and from C. xyli subsp. xyli-infected sugarcane vascular sap with a unique reaction buffer containing polyvinylpyrrolidone and ficoll. Extraction of genomic DNA was not necessary prior to PCR assay.
Efficacy of Metalaxyl, Fosetyl-Aluminum, and Straw Mulch for Control of Strawberry Leather Rot Caused by Phytophthora cactorum
Authors: Ellis M. A. , Wilcox W. F. , Madden L. V.
Published: May 2007

Chemical and cultural controls for strawberry leather rot, caused by Phytophthora cactorum, were compared in replicated plots on a commercial farm near Wooster, Ohio. Straw mulch, applied uniformly for winter protection, was removed in early spring from between the rows of all check and fungicide treatment plots. Supplemental straw mulch was applied to other plots to achieve a level of approximately 9 t/ha. Overhead irrigation, which caused the soil to puddle, was provided on alternate days during rain-free periods to promote disease development (58, 66, and 73% incidence in check plots for 1993, 1994, and 1995, respectively). Foliar sprays of fosetyl-Al, applied weekly from bloom through preharvest at rates (a.i.) of 2.24 and 4.48 kg/ha, provided 88 to 96% control, with no significant difference between fungicide rates. Metalaxyl (1.17 kg/ha), applied either once or twice as a soil drench from early growth through fruit set, provided 82 to 94% control. Straw mulch alone provided 95 to 99% control. Thus, straw mulch between the rows was equally or more effective than fungicides for controlling leather rot.
Association of Phoma terrestris, Pythium irregulare, and Fusarium acuminatum in Causing Red Root Rot of Corn
Authors: Mao W. , Carroll R. B. , Whittington D. P.
Published: May 2007

Greenhouse and field tests were conducted in 1992 and 1993 to determine the causal pathogen(s) of red root rot (RRR) of corn. Corn hybrids Dekalb DK 522, DK 572, DK 677, and DK 582 were utilized. Phoma terrestris, Pythium irregulare, and Fusarium acuminatum were used alone or in combination to infest potting mix in greenhouse tests or soil in field tests. Results indicated that P. terrestris is the primary pathogen in the RRR complex of corn in Delaware. When P. terrestris and Pythium irregulare were associated, the disease progressed faster and was more severe, resulting in significantly higher (P ≤ 0.01) root rot, basal stalk rot, and wilt. F. acuminatum played a minor role in causing the disease, with little additional symptom development when combined with P. terrestris or Pythium irregulare.
Phytophthora Shuck and Kernel Rot, a New Disease of Pecan Caused by Phytophthora cactorum
Authors: Reilly C. C. , Hotchkiss M. W. , Hendrix F. F.
Published: May 2007

Phytophthora shuck and kernel rot infection usually started at the stem end of the pecan fruit and progressed distally to encompass the entire shuck within 4 to 6 days. A distinct margin developed between dark brown necrotic tissue and healthy green tissue during rotting of the shucks. Phytophthora cactorum was isolated from the rapidly rotting pecan fruit. Two to three weeks after the symptoms appeared, the diseased shucks dried and stuck tightly to the shell. The seed coat of the kernel turned dark brown and the endosperm rotted. The new disease of pecan was first observed during September 1988 on maturing pecan fruit in central Georgia in the vicinity of the town of Byron where growers estimated losses of 50% or greater in some orchards. In south Georgia near the cities of Albany and Cordele, the disease was present but less severe. The causal agent was identified as P. cactorum and deposited with ATCC as isolate B1, ATCC No. 66186. Laboratory and field inoculations of nut clusters using the B1 isolate produced typical symptoms observed in nature. Symptoms of the disease were observed in 13 orchards, and the pathogen was isolated from the soil of 10 of these orchards in south and central Georgia.
Report on First Detection of Anthracnose (Colletotrichum gloeosporioides) on Lupins in Poland
Authors: Frencel I. M.
Published: May 2007

A previously unreported lupin disease—anthracnose (Glomerella cingulata (Stoneman) Spauld. & H. Schrenk; anamorph Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. in Penz.)—was first encountered in Poland in July 1995 on white lupin (Lupinus albus L.), grown in experimental fields of the Plant Breeding Station at Wiatrowo. Initially the disease was observed on a few plants or small clusters of plants distributed randomly within the field. Distinct symptoms of anthracnose, including bending of the plant terminal and pinkish-brown lesions on stems, were first observed at the early flowering stage. Diseased stems collapsed, displaying characteristic necrotic, crook-shaped distortions. Field surveys in 1996 indicated the rapid spread of the pathogen within white lupin inbred lines, apparently from natural infection in 1995. Later in the season, symptoms of anthracnose also appeared on yellow (L. luteus L.) and narrow-leafed (L. angustifolius L.) lupins in close proximity to white lupin plots. A fungal pathogen was consistently isolated by plating surface-disinfected symptomatic stem segments on water agar. After 7 to 10 days, heavy sporulation was observed from which a single-spore subculture was made on potato dextrose agar (PDA). Conidia were one-celled, hyaline, and oblong with obtuse or rounded ends, and were 16 to 20 μm in length, consistent with the conidial descriptions of C. gloeosporioides (1). Acervuli were mostly single and setae inconspicuous. Six fungal isolates were selected to complete Koch's postulates. Conidia from PDA cultures were suspended in sterile water agar and injected into surface wounds on the main stem of white lupin plants. Moist cotton was fastened to the inoculation area for 24 h, then plants were placed in a glasshouse. Within 5 to7 days, typical lesions resembling natural symptoms developed. Symptoms did not appear on control plants. The teleomorph stage of the pathogen was not observed in the field or on inoculated plants. The potential risk of lupin seed infection by C. gloeosporioides is indicated from our preliminary bioassays. Blotter tests were done by plating surface-disinfected seeds of three white lupin seed lot (super-elite) samples, collected from experimental fields in two consecutive years. The seed-borne infection by C. gloeosporioides in samples from 1996 ranged from 9 to 12%, in comparison with no detection of seed-borne infection in 1995 samples examined. In many phytosanitary inspections of seed production fields in 1997, a high level of anthracnose, including total epiphytotics and widespread disease in lupin crops countrywide, was observed. This is the first documented report of C. gloeosporioides causing anthracnose on lupins in Poland.

Reference: (1) J. A. von Arx. 1987. Plant Pathogenic Fungi. Beihefte zur Nova Hedvigia. Vol. 87. J. Cramer, ed. Berlin. pp. 218, 220.
Western Dwarf Mistletoe Parasitizing Colorado Blue Spruce and Norway Spruce in California
Authors: Mathiasen R. L. , Allison J. R. , Geils B. W.
Published: May 2007

Western dwarf mistletoe (Arceuthobium campylopodum Engelm.), a common parasite of ponderosa pine (Pinus ponderosa Dougl. ex Laws.) and Jeffrey pine (Pinus jeffreyi Grev. & Balf.), was found parasitizing planted Colorado blue spruce (Picea pungens Engelm.) and Norway spruce (Picea abies (L.) H. Karsten) in Upper Cuddy Valley, CA (Kern County, T. 9 N., R. 21 W., Sec. 25). One tree greater than 6 m in height of each spruce species was infected and both trees were within 12 m of a Jeffrey pine severely infected with western dwarf mistletoe. Five to 10 branches were infected on each tree and a few of these had abundant mistletoe shoot production, which allowed identification of the parasite. This is the first report of western dwarf mistletoe on Colorado blue spruce. Although this is the first report of natural infection of Norway spruce in California, this mistletoe/host combination has been reported by Weir from artificial inoculation (2) and collected by Russell in central Washington (1). We recommend that these spruce species not be planted within 15 m of pines infected with western dwarf mistletoe. Specimens of western dwarf mistletoe on Colorado blue spruce and Norway spruce were collected and deposited at the Deaver Herbarium, Northern Arizona University, Flagstaff.

References: (1) F. G. Hawksworth and D. Wiens. 1996. Dwarf Mistletoes: Biology, Pathology, and Systematics. USDA Agric. Handb. 709. (2) J. R. Weir. Bot. Gaz. 56:1, 1918.
Viral Satellite RNA Expression in Transgenic Tomato Confers Field Tolerance to Cucumber Mosaic Virus
Authors: Stommel John R. , Tousignant Marie E. , Wai Thanda , Pasini Rita , Kaper Jacobus M.
Published: May 2007

Field trials of transgenic tomato plants expressing an ameliorative satellite RNA of cucumber mosaic virus (CMV) were conducted to test the efficacy of satellite-transgenic technology to protect against CMV infection. Three transgenic tomato lines derived from two susceptible genotypes were evaluated over two growing seasons for viral symptoms and titers, satellite RNA expression, and fruit yield. Satellite-transgenic lines exhibited mild or no CMV symptoms and low viral titers relative to nontransformed plants. A significant negative correlation between satellite RNA levels and disease severity was evident in transgenic lines. Total marketable yield of CMV-infected satellite-transgenic lines was 40 to 84% greater than that of CMV-infected parent lines. Importantly, yield of CMV-infected satellite-transgenic lines did not differ significantly from mock-inoculated parent lines. Risk assessment results demonstrated low levels of satellite RNA transmission within the test site and no evidence of satellite RNA-induced damage on surrounding plants.
Tomato Spotted Wilt Virus Resistance in Chrysanthemum Expressing the Viral Nucleocapsid Gene
Authors: Sherman John M. , Moyer James W. , Daub Margaret E.
Published: May 2007

Three tomato spotted wilt virus (TSWV) nucleocapsid (N) gene constructs were employed for Agrobacterium-mediated transformation of chrysanthemum (Dendranthema grandiflora) cv. Polaris. These constructs contained either a full-length N gene (pTSWVN+), a full-length N gene encoding a truncated N protein (pTSWVNt), or an antisense version of the full-length N gene (pTSWVN-), all derived from a dahlia isolate of TSWV (TSWV-D). Initial resistance screens were conducted on cuttings made from 152 pTSWVN+, 37 pTSWVNt, and 47 pTSWVN- transformed plants employing a highly virulent, heterologous strain of TSWV (TSWV-GB) isolated from chrysanthemum and vectored by thrips. This screening served to eliminate the majority of TSWV-susceptible transgenic lines. More rigorous resistance tests with three rounds of mechanical inoculation with TSWV-GB identified one pTSWVNt and two pTSWVN- transformed lines that exhibited a total lack of systemic symptoms and no virus accumulation. Six other lines, including some pTSWVN+, exhibited a lack of one or more of the destructive necrotic TSWV symptoms (stem canker and apical bud death) and a delay in symptom expression. Both sense and antisense constructs, therefore, were found to be effective at yielding TSWV resistance in chrysanthemum. Molecular analysis revealed that the highly TSWV-resistant pTSWVNt line had no detectable levels of N protein. All three resistant lines had low levels of N gene transcript and at least three transgene insertion sites within their genomes, although susceptible lines often had a similar number of insertion sites. The generation of Polaris lines resistant to TSWV transmitted either mechanically or by thrips represents the first time a major ornamental crop has been genetically engineered for disease resistance.
Characterization of a Severe Strain of Cucumber Mosaic Cucumovirus Seedborne in Cowpea
Authors: Gillaspie A. G. , Hajimorad M. R. , Ghabrial S. A.
Published: May 2007

A new seedborne strain of cucumber mosaic cucumovirus (CMV) that induces severe symptoms on many cowpea genotypes was detected in Georgia in 1994. This strain, designated CMV-Csb, is asymptomatic on tobacco, but it produces more severe cowpea stunt symptoms when present in combination with blackeye cowpea mosaic potyvirus than do the more prevalent CMV isolates. The new strain is seedborne in cowpea (1.5 to 37%), has no associated satellite RNA, and is classified as a member of subgroup I of CMV strains based on nucleic acid hybridization assays.
Black Root Rot, Caused by Thielaviopsis basicola, on Tomato Transplants in California
Authors: Koike S. T. , Henderson D. M.
Published: May 2007

In 1997, greenhouse-produced transplants of tomato (Lycopersicon esculentum) exhibited stunting, yellowing of leaves, and lack of vigorous growth. Roots of affected plants had numerous small (2 to 10 mm long), brown lesions. Isolations from symptomatic roots onto acidified potato dextrose agar and TBM-V8 medium (1) consistently resulted in gray fungal colonies that formed catenulate, cylindrical, hyaline endoconidia and catenulate, subrectangular, thick-walled, dark aleuriospores. The fungus was identified as Thielaviopsis basicola (Berk. & Broome) Ferraris based on colony characteristics and conidial morphology. Pathogenicity was tested by producing endoconidial suspensions of representative isolates and applying them as root drenches to 2-month-old tomato (cv. Early Girl) plants in soil-less, peat-based potting mix. Sterile, distilled water was applied to control plants. After 14 days in a greenhouse, symptoms similar to those originally observed developed and the pathogen was reisolated from lesions on the roots. Control plants developed no disease symptoms. The test was repeated and the results were similar. This is the first documentation of black root rot caused by T. basicola on tomato transplants in California. Disease incidence reached as high as 50 to 60% in certain plantings.

Reference: (1) J. N. C. Maduewesi et al. Phytopathology 66:526, 1976.
First Report of Fusarium solani f. sp. glycines Causing Sudden Death Syndrome of Soybean in Canada
Authors: Anderson T. R. , Tenuta A. U.
Published: May 2007

Sudden death syndrome (SDS), caused by Fusarium solani (Mart.) Sacc. f. sp. glycines, is a disease of soybean (Glycine max (L.) Merr.) in several central and southern states of the United States. In Ontario, Canada, individual soybean plants with typical foliar symptoms of SDS (1) have been observed annually in Kent County since 1993 but the causal organism was not isolated or identified. In 1996, plants with symptoms of SDS were observed in six fields located in Essex, Kent, and Lambton counties. Interveinal chlorosis and necrosis occurred on top leaves of affected plants and a pale brown discoloration occurred in the vascular system in lower stems and upper tap roots. Slow-growing isolates of F. solani f. sp. glycines with typical blue sporodochia were isolated from symptomatic plants on acidified potato dextrose agar (1). Root inoculation of 15 2-week-old seedlings with colonized oat kernals with each of five single-spore isolates caused typical SDS symptoms on 5-week-old soybean plants of cvs. Conrad, A2540, S19-90, and Ripley in the greenhouse. The severity and incidence of symptoms varied with cultivar and isolate. Of 125 plants inoculated, 6% of Conrad, 10% of A2540, 14% of S19-90, and 17% of Ripley plants developed foliar symptoms. Symptoms did not develop on noninoculated controls. F. solani f. sp. glycines was reisolated from roots of symptomatic plants. Although Ripley is known to have resistance to SDS (2), foliar and root symptoms developed following inoculation with each Ontario isolate of F. solani f. sp. glycines. Yield losses in 1996 were difficult to assess because of the scattered distribution of diseased plants in most fields. Diseased plants had few and poorly filled pods. In two fields, soybean growth was severely restricted in large areas covering 2 ha each; however, soybean cyst nematode (SCN) was present in both fields. SCN was present at all locations. Although total yield losses are currently low, it is evident that F. solani f. sp. glycines causing SDS has become widely distributed in southwest Ontario and disease severity is increasing.

References: (1) K. W. Roy et al. Phytopathology 79:191, 1989. (2) P. A. Stevens et al. Crop Sci. 33:929, 1993.
Characterization of a Potyvirus Infecting Sunflower in Argentina
Authors: Dujovny G. , Usugi T. , Shohara K. , Lenardon S.
Published: May 2007

A virus causing chlorotic mottling symptoms on sunflower was found in various locations in Argentina. Symptoms were small chlorotic spots, yellow blotches on leaves, and plant stunting. Virus transmission efficiency by mechanical inoculation was 73 to 100%, and by Myzus persicae was 31 to 49%. The host range included members of the Amaranthaceae, Asteraceae, Chenopodiaceae, and Solanaceae families. Electron microscopy of leaf dips from infected plants revealed flexuous particles 17 nm wide and 770 nm long. Cytoplasmic laminar aggregates and pinwheel inclusions were observed in ultrathin sections. Purified virus preparations analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis resolved a capsid protein of 33 kDa. A monoclonal antibody to aphid-transmitted potyviruses reacted with the capsid protein of this virus. In dot blot immunoassays, a polyclonal antiserum (early bleeding) reacted with infected sunflowers and weakly with Bidens mottle potyvirus, but not with either maize dwarf mosaic potyvirus or potato virus Y. The evidence suggests that a potyvirus is infecting sunflower, and a partial characterization of the causal agent is reported.
Identification and Quantification of Ascospores as the Primary Inoculum for Collar Rot of Greenhouse-Produced Tobacco Seedlings
Authors: Gutierrez W. A. , Shew H. D.
Published: May 2007

Collar rot, caused by Sclerotinia sclerotiorum, is a severe disease of tobacco seedlings grown in greenhouses. A semiselective medium was adapted and used to detect the presence and quantity of ascospores in commercial greenhouses. Petri dishes of the semiselective medium were placed inside and outside of greenhouses in four counties during the transplant production period in 1995 and 1996. Ascospores were present throughout the production period each year (February to April) and were confirmed to be the primary inoculum for the disease. Significant differences were observed in the number of ascospores trapped within and between counties. Peak numbers of ascospores were trapped between 10 and 12 a.m., and higher numbers of ascospores were trapped outside than inside houses. In general, distribution of ascospores inside houses was uniform unless a high concentration of apothecia was present very close to one section of the greenhouse. The semiselective medium and trapping technique used in this study may allow development of a forecasting system for collar rot of tobacco based on the presence and level of pathogen inoculum.
In vitro Inhibition of Soft-Rotting Bacteria by EDTA and Nisin and in vivo Response on Inoculated Fresh Cut Carrots
Authors: Wells John M. , Liao Ching-Hsing , Hotchkiss Arland T.
Published: May 2007

EDTA and the antibiotic nisin, in combination with heat, were tested for inhibition of growth of six pectolytic, soft-rotting bacteria in 80% trypticase soy broth (TSB). Fifty percent reduction of growth by EDTA at 25°C in TSB occurred at 3.24 mM for Erwinia chrysanthemi, 2.57 mM for Pseudomonas fluorescens, 0.96 mM for E. carotovora (subsp. carotovora), 0.48 mM for P. viridiflava, 0.17 mM for Xanthomonas campestris (pv. campestris), and 0.16 mM for Cytophaga johnsonae. Nisin at 50 ug/ml was effective against X. campestris and C. johnsonae (over 90% inhibition of growth) but not against the other four bacteria (less than 20% inhibition), which are the more economically important soft-rotters. Combinations of EDTA and nisin were synergistic. A combination of 0.3 mM EDTA + nisin at 50 μg/ml inhibited growth of E. carotovora, E. chrysanthemi, and P. viridiflava by over 70%, and growth of P. fluorescens by 37%. Hot water treatments for 0.3 min at 37 or 49°C reduced survival of bacteria in the presence of EDTA + nisin, but not of EDTA, nisin, or water alone. EDTA + nisin at 37°C reduced CFU/ml of E. carotovora, E. chrysanthemi, P. fluorescens, and P. viridiflava by 2 log units, and at 49°C by 3 log units, compared with the 25°C treatment. Decay of carrot disks inoculated at two inoculum levels (103 and 104 CFU per disk) with E. carotovora, P. fluorescens, or P. viridiflava was reduced by a 1.5-min immersion in 45°C water, with or without EDTA and nisin additives. Immersion in 0.3 mM EDTA + nisin at 15 to 50 μg/ml at 45°C reduced decay due to E. carotovora and to P. fluorescens at the lower inoculum level by an average of about 50% compared with water alone at 45°C, but differences were statistically significant only at the 90% level of confidence and no different than a standard chlorine dip, current commercial practice for cut carrot slices.
A Formulation of Trichoderma and Gliocladium to Reduce Damping-off Caused by Rhizoctonia solani and Saprophytic Growth of the Pathogen in Soilless Mix
Authors: Lewis J. A. , Larkin R. P. , Rogers D. L.
Published: May 2007

Commercially manufactured cellulose granules (Biodac) were mixed with a sticker and fermentor-produced biomass of isolates of Trichoderma spp. and Gliocladium virens to produce a formulation in which chlamydospores in the biomass were “activated” with dilute acid. Activation resulted in the formation of young, actively growing hyphae of the biocontrol fungi within a 2- to 3-day period under no special aseptic conditions. Activated Biodac with biomass of isolates Gl-3, Gl-21, and Gl-32 of G. virens and isolate TRI-4 of T. hamatum applied to soilless mix at a rate of 1.5% (wt/wt) reduced damping-off of eggplant caused by Rhizoctonia solani (R-23) and resulted in stands comparable to that (88%) in noninfested soilless mix. Saprophytic growth of the pathogen was also reduced. The application of either of two activated Biodac formulations to provide the same amount (1.5% with 9.4 mg of biomass per g of Biodac or 0.2% with 75.0 mg of biomass per g of Biodac) reduced preemergence damping-off as well as saprophytic growth of R-23. Also, there was about a 103-fold population increase of Gl-3 and TRI-4 in the soilless mix at the time of plant harvest compared with that provided to the soilless mix at the time of formulation addition. Activated Biodac of Gl-3 also reduced the spread of R-23 in soilless mix when the pathogen was applied at specific foci rather than evenly distributed. The inhibition of pathogen spread significantly reduced the postemergence damping-off of cucumber, eggplant, and pepper seedlings.
First Record of Faba Bean Necrotic Yellows Virus and Beet Western Yellows Luteovirus Affecting Lentil and Chickpea in Pakistan
Authors: Makkouk Khaled M. , Bashir Muhammad , Jones Roger
Published: May 2007

In an intensive survey of lentil and chickpea fields and Research Station plots in the Punjab province of Pakistan, more than 6,505 samples were collected and tested for presence of 14 different viruses by the tissue-blot immunoassay (TBIA) procedure (2). All antisera used were virus specific, including those for faba bean necrotic yellows virus (FBNYV) (1) and beet western yellows luteovirus (BWYV) (ATCC 647). Counting plants with virus symptoms greatly underestimated virus incidence in lentil crops but was a better guide to virus occurrence in chickpeas. Overall, about 1 in 5 plants of lentil were virus infected with 15% of fields having incidence over 50%. In contrast, levels of infection were mostly low in chickpea. Pea seed-borne mosaic virus (PSbMV) followed by cucumber mosaic virus (CMV), both of which are aphid- and seed-borne, were the most abundant viruses in lentils, but also occurred in chickpea. PSbMV incidence was 17% in lentil and 0.1% in chickpea fields, whereas CMV incidence was 1% in lentil and 0.1% in chickpea fields. The other viruses found on both lentil and chickpea were FBNYV, BWYV, chickpea chlorotic dwarf geminivirus, chickpea luteovirus, and alfalfa mosaic alfamovirus. Because of yield losses associated with PSbMV infection, the high levels of infection in lentils are cause for concern. This is the first record of FBNYV and BWYV affecting lentil and chickpea in Pakistan, but their incidence in the fields where they have been detected was low (less than 1%). FBNYV was detected in three of the 33 lentil and two of the 34 chickpea fields surveyed. BWYV was detected in two of the 33 lentil and three of the 34 chickpea fields surveyed.

References: (1) A. Franz et al. Ann. Appl. Biol. 128:255, 1996. (2) K. M. Makkouk and A. Comeau. Eur. J. Plant Pathol. 100:71, 1994.
First Report of Powdery Mildew of Tomato Caused by an Erysiphe sp. in Spain
Authors: Olalla L. , Torés J. A.
Published: May 2007

A new powdery mildew disease of tomato (Lycopersicum esculentum Mill.) was observed for the first time in several greenhouses in Almería (Spain) in March through June 1997. Fungal growth appeared as typical, white, powdery mildew colonies that were restricted to upper leaf surfaces. Initially, individual colonies were small and nearly circular in shape but later enlarged and coalesced to cover the whole leaf surface. Conidia were produced singly on unbranched, 3-cell conidiophores, and were cylindrical to ovate, ranging in size from 27.6 to 43.5 μm (mean = 35.3, SD = 3.8) in length and from 14.1 to 23.2 μm (mean = 19.0, SD = 2.2, n = 95) in width. No fibrosin bodies were observed. Germ tubes were formed from the ends of conidia. Appressoria from mycelia were single and moderately lobed. Conidiophores measured from 56.6 to 108.8 μm (mean = 84.8, SD = 14.2) with straight foot cells 24.7 to 55.1 μm (mean = 38.6, SD = 7.5) in length, and from 7.3 to 10.2 μm (mean = 8.0, SD = 1) in width. Morphological characteristics of this powdery mildew are similar to those previously given for the Erysiphe sp. described in the United Kingdom (1) and Greece (2). Cleistothecia were not found, so species identification was not made. Conidia from infected tomato leaves were shaken onto leaves of melon (Cucumis melo L. ‘Rochet’), cucumber (Cucumis sativus L. ‘Bellpuig’), summer squash (Cucurbita pepo L. ‘Black Beauty’), watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai ‘Sugar Baby’) and tomato cvs. Roma, Daniela, and Marmande. After 7 days the disease was observed on summer squashes, melons, and all tomato cultivars, but not on watermelons or cucumbers.

References: (1) J. T. Fletcher et al. Plant Pathol. 37:594, 1988. (2) D. J. Vakalounakis and A. Papadakis. Plant Pathol. 41:372, 1992.
Phormium Yellow Leaf Phytoplasma Is Associated with Strawberry Lethal Yellows Disease in New Zealand
Authors: Andersen M. T. , Longmore J. , Liefting L. W. , Wood G. A. , Sutherland P. W. , Beck D. L. , Forster R. L. S.
Published: May 2007

A yellows disease of strawberry plants was identified in propagation beds in New Zealand. Affected plants were flatter to the ground, showed purpling of older leaves, reduced leaf size, yellowing of younger leaves, and sometimes plant death. A phytoplasma was observed in the phloem of affected plants. The 16S rRNA gene of the phytoplasma was amplified by polymerase chain reaction from symptomatic plants and from one asymptomatic plant, but not from 36 other asymptomatic plants. Nucleotide sequence analysis of the 16S rRNA gene showed that the phytoplasma is closely related or identical to the phytoplasma associated with the yellow leaf disease of New Zealand flax (Phormium tenax).
The Effect of Race QCCJ of Puccinia graminis f. sp. tritici on Yield and Quality in Barley
Authors: Dill-Macky R. , Roelfs A. P.
Published: May 2007

The progress of epidemics of race QCCJ of Puccinia graminis f. sp. tritici was examined in field plots of the barley cultivars Robust, Excel, Stander, Azure, Stark, Larker, Bonanza, and Steptoe. In addition, a potential source of resistance (cv. Diamond), and a susceptible line (ND11075) were included. Rust-free treatments were maintained to provide comparisons of grain yield and quality. Barleys with Rpg1, which confers resistance to races of P. graminis f. sp. tritici other than Pgt-QCCJ, were generally more resistant than cultivars or lines that lacked this gene. However the severity of losses indicated that under high disease pressure the resistance conferred by Rpg1 would not be effective. Yield reductions of up to 29% were recorded and were generally associated with reduced grain size and weight. The continued presence of Pgt-QCCJ as a component of the P. graminis population in the United States, since it was first detected in 1989, indicates that Pgt-QCCJ remains a threat to commercial barley production.
First Report of Powdery Mildew Caused by an Oidium sp. on White Sweetclover in Kansas
Authors: Stuteville D. L.
Published: May 2007

Powdery mildew was observed on plants of white sweetclover (Melilotus alba Medik.) in Riley County, Kansas, in 1995, 1996, and 1997 but was not examined closely until 1997. White, effuse to dense, amphigenous mycelia bearing Oidium conidia were obvious by mid June. Effuse growth occurred on petioles and stems. Invaded leaflets wilted and dropped, sometimes leaving a green petiole. Signs and symptoms diminished during the warmer periods of July and August, reoccurred in September, and remained prominent until the foliage froze in November. However, on 1 December, viable, newly produced conidia were collected from scant hyphal growth on protected leaves at the base of a few plants. A sexual state was not found. Characteristics of the conidial state fit those of Erysiphe pisi (1). Powdery mildew was never observed on plants of yellow sweetclover (M. officinalis (L.) Lam.) growing among the mildewed plants of white sweetclover. This is the first report of powdery mildew on M. alba in Kansas.

Reference: (1) H. J. Boesewinkel. Bot. Rev. 46:167, 1980.
First Report of Powdery Mildew Caused by Sphaerotheca fusca on Tomatillo in California
Authors: Koike S. T. , Smith R. F.
Published: May 2007

Tomatillo or husk tomato (Physalis ixocarpa Brot.) is an annual Solanaceous bush grown for its fruit, which are harvested when the fruit fill the enlarged calyx and are used primarily in Hispanic cooking. In the summer of 1997, commercial field-grown tomatillo in the Salinas Valley (Monterey County) was severely affected by a powdery mildew disease. Fungal growth was found on leaves, petioles, and calyces and resulted in twisting, desiccation, and premature senescence of the tissues. The mycelium was white to gray, ectophytic, amphigenous, and effuse. Mycelial appressoria were indistinct. Conidiophore foot cells were straight, cylindric, measured 36.1 to 61.1 µm (mean 47.0) × 11.1 to 13.9 µm (mean 11.7), and were followed by 1 to 3 shorter cells. Doliform conidia were formed in chains and measured 25.0 to 50.0 µm (mean 32.5) × 11.1 to 22.2 µm (mean 17.7). The length-to-width ratios of conidia generally were less than 2.0, and fibrosin bodies were present. Germ tubes usually were laterally inserted, lacked conspicuous appressoria, and were of the pannosa-type. Cleistothecia were not observed. Based on these characters, the fungus was identified as Sphaerotheca fusca (Fr.) Blumer, Beitr. Krypt.-Fl. Schweiz (1). Pathogenicity was confirmed by gently pressing infected leaves onto leaves of potted tomatillo. Inoculated plants were kept in a chamber at 100% humidity for 48 h, and then maintained in a greenhouse. Powdery mildew developed on inoculated plants after 12 to 14 days, while uninoculated plants did not develop disease. The experiment was conducted a second time and the results were the same. This is the first report of a powdery mildew disease of tomatillo in California.

Reference: (1) U. Braun. Nova Hedwigia 89:1, 1987.
Bacterial Blight of Broccoli Raab: A New Disease Caused by a Pathovar of Pseudomonas syringae
Authors: Koike Steven T. , Henderson Diana M. , Azad Hamid R. , Cooksey Donald A. , Little E. L.
Published: May 2007

Bacterial blight is a new disease of broccoli raab or rappini (Brassica rapa subsp. rapa) that has developed on commercially grown crops in the Salinas Valley (Monterey County) in California. Symptoms consist of small, angular, water-soaked flecks on lower foliage that are visible from both adaxial and abaxial sides of the leaves. These flecks expand and become surrounded by bright yellow borders. With time, multiple leaf spots coalesce and result in large, irregular necrotic areas, extensive leaf yellowing, and eventual leaf death. If symptoms develop on the uppermost leaves attached to the inflorescence, the shoot loses market quality and will not be harvested. Pseudomonas syringae was consistently isolated from symptomatic plants, and selected strains caused similar symptoms when inoculated onto broccoli raab test plants. Broccoli raab strains caused leaf spot symptoms on nine other Cruciferous plants, as well as on three grass species (California brome, oat, and common timothy). Conversely, broccoli raab was not infected by P. syringae pathovars coronafaciens, maculicola, and tomato. Broccoli raab strains were positive for coronatine toxin production. Fatty acid analyses indicated that the P. syringae from broccoli raab was most closely related to P. syringae pvs. coronafaciens and maculicola, but its distinct host range suggests that it may be considered a separate pathovar.
Occurrence of Peronosclerospora sorghi in Uganda
Authors: Bigirwa G. , Adipala E. , Esele J. P.
Published: May 2007

A study was conducted to determine the occurrence and severity of sorghum downy mildew on three major hosts (maize, sorghum, and Johnson-grass) in Uganda. Five surveys were conducted in four growing seasons, between 1994 and 1995. The disease was encountered in 11 of the 22 districts surveyed. In the majority of the areas, incidence was less than 10%, but it was significantly higher (P < 0.05) in the second season of 1994 than in the first season of 1995. Soil type significantly (P = 0.001) influenced the incidence of sorghum downy mildew, with high incidence being associated with sandy soils, followed by loamy soils, and lowest incidence in clay soils. Incidence, shredding, and oospore production were comparatively higher on sorghum and Johnson-grass than on maize.
Characteristics of a Latent Potyvirus Seedborne in Guar and of Guar Green-Sterile Virus
Authors: Gillaspie A. G. , Pappu H. R. , Jain R. K. , Rey M. E. C. , Hopkins M. S. , Pinnow D. L. , Morris J. B.
Published: May 2007

A symptomless, seedborne potyvirus was isolated from guar (Cyamopsis tetragonoloba) germ plasm in Griffin, Georgia. The host range and serology were similar to those reported for guar green-sterile virus (GGSV) and guar symptomless virus. Biological, serological, and molecular comparisons of the Georgia isolate and the South African GGSV indicate they are similar and are closely related to bean common mosaic potyvirus (BCMV). The Georgia isolate is seed-transmitted at a rate of up to 94% in guar line PI 340385. Sequence analysis of the capsid protein (CP) gene and the 3′-untranslated region (3′-UTR) showed that both isolates are 96% homologous. GenBank searches indicate that both are related to various strains of BCMV. The highest CP nucleotide sequence and 3′-UTR identities of 91 and 93%, respectively, were with those of BCMV-NL4. On this basis, both isolates from guar should be considered as strains of BCMV.
Inheritance of Complete Resistance to Pearl Millet Downy Mildew
Authors: Singh S. D. , Talukdar B. S.
Published: May 2007

Inheritance of downy mildew (Sclerospora graminicola) resistance in pearl millet (Pennisetum glaucum) was studied in a cross involving DMRP (downy mildew resistant Pennisetum) 292 and DMSP (downy mildew susceptible Pennisetum) 23. DMRP 292, derived from IP 18292, and DMSP 23, derived from Tift 23DB, were made homozygous for downy mildew resistance-susceptibility by three generations of single plant selection followinginoculations with homogenized sporangial population of S. graminicola from the ICRISAT Asia Center. Potted seedlings of parental lines, F1, F2, and BC progenies were evaluated for their reactions to downy mildew following inoculation. The results show that complete resistance to downy mildew in DMRP 292 is controlled by a single dominant gene. Because of the simple mode of inheritance, resistance utilization from DMRP 292 is simple and straightforward. We designate this gene as Rsg1.
Differential Susceptibility of Anthurium Cultivars to Bacterial Blight in Foliar and Systemic Infection Phases
Authors: Fukui H. , Alvarez A. M. , Fukui R.
Published: May 2007

Susceptibility of anthurium cultivars to systemic infection by the bacterial blight pathogen, Xanthomonas campestris pv. dieffenbachiae, was examined using a bioengineered bioluminescent strain (V108LRUH1) and compared with susceptibility to foliar infection. Eight cultivars with different levels of susceptibility to foliar infection were evaluated for their susceptibility to systemic infection. Petioles of second youngest leaves cut near the main stem were inoculated with strain V108LRUH1, and subsequent movement of this bacterium into other petioles was monitored by observing bioluminescence from the plants. The actual extent of systemic movement was determined by reisolating V108LRUH1 from dissected segments of the remaining petioles. In susceptible cultivars, the pathogen advanced very rapidly and nearly reached the distal end of petioles. In resistant cultivars, the pathogen was detected in none (or very few) of the petiole segments. However, the susceptibility ranking among the tested cultivars for systemic infection did not always correspond to the ranking determined for foliar infection: i.e., one cultivar that was susceptible to foliar infection was highly resistant to systemic infection, and vice versa. This suggests that cultivar susceptibility of anthuriums to bacterial blight may differ depending on the phase of disease progression, and thus evaluation for both disease phases is essential for complete understanding of cultivar susceptibility.
Severe Outbreak of Chocolate Spot of Fava Bean, Caused by Botrytis fabae, in California
Authors: Koike S. T.
Published: May 2007

A damaging disease developed on commercial fava bean (Vicia faba L.) in coastal California following heavy rains in January through March, 1998. Two symptom types were observed. The most common symptoms on leaves and stems were small (1 to 5 mm), circular to oblong, dark red spots. As disease progressed, spots coalesced and caused large red areas on leaves and stems. Secondly, large (8 to 12 mm), oblong to irregular, dark brown necrotic spots with concentric circles formed on leaves, resulting in blighting and death of foliage. Severely affected plants lost over 50% of foliage and pod development was poor. Botrytis fabae was consistently isolated from both types of spots (1,2). Ellipsoidal to ovoid conidia measured 17 to 22 × 11 to 17 μm, and all isolates formed profuse, small (1 to 3 mm), spherical to oblong, black sclerotia. Pathogenicity was confirmed by inoculating isolates onto fava bean plants, incubating them in a humidity chamber for 48 h, then maintaining plants in a greenhouse. Inoculated plants developed both types of symptoms, and B. fabae was reisolated. Uninoculated controls developed no symptoms. The experiment was repeated and results were the same. While chocolate spot of fava bean has been observed previously in various parts of the state, this is the first documentation of this disease in California. The disease was also confirmed on fava bean grown as a winter cover crop in the same coastal area of California.

References: (1) J. G. Harrison. Trans. Br. Mycol. Soc. 83:631, 1984. (2) J. G. Harrison. Plant Pathol. 37:168, 1988.
First Report of Bell Pepper (Capsicum annuum) as a Host of Sclerotinia minor in California
Authors: Gonzalez T. G. , Henderson D. M. , Koike S. T.
Published: May 2007

In 1997, commercially grown bell pepper in the Salinas Valley (Monterey County), California, developed a previously undescribed disease. Plant foliage became pale green and wilted. Crowns developed brown lesions that girdled the plants, resulting in plant death. White mycelia and small (2 to 3 mm), black, irregularly shaped sclerotia were observed on the outside of plant crowns and in the centers of stem cavities. Isolations consistently resulted in the recovery of Sclerotinia minor. Pathogenicity was tested by inoculating 2-month-old bell pepper plants (cv. California Wonder) with sclerotia from three pepper and three lettuce (Lactuca sativa) isolates of S. minor (seven plants per isolate). Six to 10 sclerotia were placed 1 cm below the soil line and adjacent to the plant crowns. After 8 days, plants inoculated with pepper and lettuce isolates developed symptoms similar to those found in commercial fields, and S. minor was recovered from all peppers. The uninoculated control plants developed no symptoms. This is the first report of bell pepper as a host of S. minor.
Analysis of Double-Stranded RNAs from Cherry Trees with Stem Pitting in California
Authors: Zhang Yun-Ping , Uyemoto J. K. , Kirkpatrick B. C.
Published: May 2007

Five distinct dsRNA species were recovered from Bing sweet cherry (Prunus avium (L.) L.) trees with stem pitting symptoms. A 4.7-kilobase pair (kbp) dsRNA was isolated from mahaleb rootstock (P. mahaleb L.); an unrelated 4.7-kbp dsRNA, always co-purified with a 1.3-kbp dsRNA, and a 9-kbp dsRNA were from Bing cherry. In addition, an 8.5-kbp dsRNA found in diseased Shirofugen flowering cherry and in Bing cherry was identified as sour cherry green ring mottle virus (CGRMV). The larger, 8.5- and 9.0-kbp dsRNA species were graft-transmissible, while the smaller ones were non-transmissible and appeared cryptic in nature. Reverse transcription-polymerase chain reaction (RT-PCR) assays were developed for each dsRNA species by cloning and sequencing cDNA synthesized from the dsRNA templates. When several diseased collections were assayed by RT-PCR, approximately 14% reacted positively with primers for the 9.0-kbp dsRNA or CGRMV. Although CGRMV and the 9.0-kbp dsRNA caused wood-marking symptoms in graft-inoculated Mazzard (P. avium) seedling trees, no xylem or canopy symptoms developed in grafted Bing cherry. The causal agent or agents of cherry stem pitting have not been identified.
Development of a Sensitive Colorimetric-PCR Assay for Detection of Viruses in Woody Plants
Authors: Rowhani Adib , Biardi Lenka , Routh Geoffrey , Daubert Steve D. , Golino Deborah A.
Published: May 2007

Diagnostic methods employing the polymerase chain reaction (PCR) provide the most sensitive means currently available for detecting viruses in woody plants. A new technique has been tested that does not rely on gel electrophoresis or molecular hybridization to detect virus-specific PCR products. This colorimetric method for detection of PCR products from woody plants was demonstrated to be at least as sensitive as gel analysis. When combined with immunocapture of virions from plant sap, colorimetric detection provides a means to apply PCR technology to a large number of samples. Here, we report on the use of this technique for detection and quantitation of a walnut isolate of cherry leafroll virus (CLRV-W), citrus tristeza virus (CTV), prune dwarf virus (PDV), prunus necrotic ringspot virus (PNRSV), and tomato ringspot virus (ToRSV) in woody and herbaceous plants. For purified virus preparations, detection limits ranged from 100 pg/ml to 100 ag/ml. We also describe the colorimetric PCR detection of CTV in pooled samples.
Detection of Two Races of Phialophora gregata f. sp. adzukicola, the Causal Agent of Adzuki Bean Brown Stem Rot
Authors: Kondo N. , Fujita S. , Murata K. , Ogoshi A.
Published: May 2007

Adzuki bean brown stem rot (BSR) is endemic on Hokkaido Island and has been controlled since 1985 by using resistant cultivars. BSR was reported on the resistant cultivar Kita-no-otome in a field near Memuro-cho, and this study was undertaken to determine if pathogenic races were present. The existence of avirulent and virulent isolates of the pathogen to cultivar Kita-no-otome was shown by comparing the virulence among six isolates (T96-1, T96-2, T96-3, T96-4, T96-5, and S95-1) obtained from diseased plants or naturally infested field soils. Three out of six isolates caused no disease on Kita-no-otome (DSI = 0), whereas the other three isolates were virulent on this cultivar (DSI = 1.2 to 2.6). In additional experiments, another three lines, Toiku No. 125, Toiku No. 132, and Toiku No. 140, derived from various gene sources, also revealed the same response to two representative isolates (T96-1 and T96-5) tested as with Kita-no-otome. Consequently, two races of Phialophora gregata f. sp. adzukicola, race 1 and race 2, can be distinguished by avirulence or virulence to Kita-no-otome, respectively.
Identification of the East African Strain of Sweet Potato Chlorotic Stunt Virus as a Major Component of Sweet Potato Virus Disease in Southern Africa
Authors: Gibson R. W. , Kaitisha G. C. , Randrianaivoarivony J. M. , Vetten H. J.
Published: May 2007

Sweet potato virus disease (SPVD) is the most damaging disease of sweet potato Ipomoea batatas (L.) Lam. in Africa. It is caused by sweet potato feathery mottle potyvirus (SPFMV) plus either the West African strain of sweet potato chlorotic stunt crinivirus (Closteroviridae) (SPCSV-WA) (2) or the serologically distinct and apparently more severe East African strain (SPCSV-EA) (1). Typical symptoms of SPVD include severe plant stunting, leaf distortion, chlorosis, mosaic, or vein clearing (1). During a survey done in February 1998 of 48 farmers' fields in Lusaka Province and North Western Province of Zambia, sweet potato plants with typical SPVD symptoms were observed. Incidence was generally 1 to 5% but occasionally >20%. To determine which viruses (SPFMV, SPCSV-EA, SPCSV-WA) were present in symptomatic plants, enzyme-linked immunosorbent assays (ELISAs) were done on leaf sap extracts. Twenty-two SPVD-affected plants from Lusaka Province and 15 from North Western Province were tested and SPFMV and SPCSV-EA (but not SPCSV-WA) were detected in all samples. SPCSV-EA by itself may cause purpling or yellowing of lower or middle leaves (1). Eight plants showing these symptoms were collected from North Western Province, and SPCSV-EA only was detected in six of the samples. SPVD was also observed in a 1997 survey of crops near Antsirable, Madagascar; incidence was generally <1% but occasionally >20%; SPFMV and SPCSV-EA, but not SPCSV-WA, were detected in two SPVD samples tested. Our results are the first report of SPCSV in southern Africa. SPVD in the regions surveyed appears to be due to SPFMV and SPCSV-EA; SPCSV-WA was not detected.

References: (1) R. W. Gibson et al. Plant Pathol. 47:95, 1998. (2) G. A. Schaefers and E. R. Terry. Phytopathology 66:642, 1976.