RESUMEN
Crown gall was detected in several vineyards in the Central Anatolia region of Turkey. Vineyards were planted to cultivars of grape that originated in Turkey and that were not grafted. The predominant species isolated from galls consisted of tumorigenic strains of Agrobacterium vitis. They were identified based on reactions to standard biochemical and physiological tests, by polymerase chain reaction amplification of specific Ti plasmid and chromosomal sequences, and by reaction to a species-specific monoclonal antibody. All strains utilized octopine, suggesting that they may carry similar types of Ti plasmids. Some of the strains exhibited a differential host range compared with others and were less virulent based on the numbers of galls that they induced on grape. When grapevines were treated with nontumorigenic A. vitis strain F2/5 prior to inoculation with the Turkish A. vitis strains, crown gall was effectively controlled. The genetic diversity of strains was evaluated by comparing DNA fingerprints that were generated by restriction enzyme digestion of the intergenic spacer region that lies between 16S and 23S rRNA genes. They segregated into two main groups, one that is similar to previously identified A. vitis strains carrying octopine type Ti plasmids and one that was more similar to strains carrying nopaline and vitopine Ti plasmids. The strains of A. vitis from Turkey may represent ancestral forms of the pathogen that will provide insight into the evolution of the bacterium.
RESUMEN
Woody ornamentals including 'Bradford' and 'Aristocrat' pears (Pyrus calleryana), Indian hawthorn (Rhaphiolepis sp.), and cotoneaster (Cotoneaster spp.) developed blossom and shoot blight symptoms suggestive of fire blight caused by Erwinia amylovora. Disease was observed in several counties in north Florida and south Georgia and samples were sent to Florida Extension Plant Diagnostic Clinic-Quincy (FEPDC-Q). The incidences in individual 'Bradford' pear were as high as 30 to 40 strikes per tree. This level of severe E. amylovora infections on 'Bradford' pear has not been seen in Florida for the last 10 years based on FEPDC-Q data. Symptomatic plants first appeared in the landscape and nurseries around the first week of April 2000 in the following counties: Bay, Holmes, Washington, Gadsden, Leon, Jefferson (north Florida), and Decatur (south Georgia). Severely infected 'Bradford' pear trees were also observed in Georgia cities of Cairo, Thomasville, Moultrie, and Tifton. The presence of E. amylovora in samples was verified by pEA29-polymerase chain reaction (PCR) (2,4), fatty acid methyl ester analysis (MIDI, Newark, DE), and colony type on semi-selective modified Miller-Schroth (MMS) medium (3). Of the 16 samples tested by PCR, E. amylovora was present in all. Actively growing shoots of Cotoneaster salicifolius (a susceptible host) were inoculated with a bacterium isolated from 'Bradford' pears that was identified as E. amylovora by PCR. Dark brown necrotic tissues with typical fire blight appearance developed within 10 days. E. amylovora was reisolated on MMS medium from inoculated shoot tissues of C. salicifolius and confirmed by PCR. The presence of E. amylovora from ornamental pears, Indian hawthorn, and cotoneasters was previously reported in Florida (1). Cool spring temperatures in the Florida panhandle and several rain events during the bloom period may have stimulated the severe outbreak of fire blight. This severe outbreak highlights the importance of using a forecasting model such as Maryblyt 4.3 to predict unexpected infection periods so that preventive control measures can be taken. References: (1) S. A. Alfieri, Jr. et al. Florida Department of Agriculture and Consumer Services, Bulletin No. 14, 1994. (2) S. Bereswill et al. Appl. Environ. Microbiol. 58:3522, 1992. (3) W. Brulez and W. Zeller. Acta Hortic. 117:37, 1981. (4) M. T. Momol et al. Plant Dis. 82:646, 1998.
RESUMEN
In October 1998, symptoms characteristic of tomato yellow leaf curl virus (TYLCV) were observed on fresh market tomato (Lycopersicon esculentum Mill.) in four production fields, two in Decatur County, Georgia, and two in Gadsden County, Florida. Symptoms observed were plant stunting, reduced leaf size, yellow leaf margins, and mottling. The incidence of symptomatic plants was less than 1% in all fields examined. In most cases, symptoms were observed only on the upper portion of plants, suggesting these plants had been infected by secondary spread from an unknown source. Nuclear inclusions characteristic of geminiviruses were observed by light microscopy in leaf tissue from symptomatic plants (1). To identify the geminivirus, total DNA from infected plants was extracted from six symptomatic tomato plants (two from Georgia and four from Florida) for polymerase chain reaction (PCR; J. E. Polston, personal communication). DNA was amplified with geminivirus DNA A degenerate primer set PAL1v1978 and PAR1c496 (2) from these extracts in addition to extracts from a known TYLCV-infected, a tomato mottle virus (ToMoV)-infected, and a healthy tomato plant. A PCR product of 1.4 kb was obtained from plants with TYLCV-like symptoms, while a 1.4-kb product and a 1.1-kb product were obtained from extracts of the known TYLCV-infected and ToMoV-infected tomato plants, respectively. No PCR product was obtained from extracts of healthy tomato plants. The 1.4-kb PCR products from one Georgia sample and one Florida sample were compared with those of TYLCV and ToMoV by restriction enzyme (RE) digestion with EcoRI and ClaI. The RE pattern of the 1.4-kb fragment from both samples was identical to the RE pattern of TYLCV and different from that of ToMoV. Adult and immature whiteflies collected from the fields where TYLCV was found were identified as Bemisia tabaci, the vector of TYLCV, but the biotype was not established. This report of TYLCV in south Georgia and north Florida extends the geographic range of TYLCV in the U.S. northward approximately 100 km. Georgia is the second state in which TYLCV was found since its initial detection in south Florida in July 1997 (J. E. Polston, personal communication). Monitoring of silverleaf whitefly populations and detection of TYLCV on alternate hosts will continue in order to estimate the potential impact of this virus on south Georgia and north Florida agriculture. References: (1) R. G. Christie and J. R. Edwardson. Plant Dis. 70:273, 1986, (2) M. R. Rojas et al. Plant Dis. 77:340, 1993.
RESUMEN
Agrobacterium vitis was isolated from roots of 41 of 66 feral Vitis riparia vines collected in three different regions of New York State. Two of the regions were more than 150 km from commercial vineyards. The strains were highly diverse as determined by DNA fingerprinting of the chromosomal region lying between the 16S and 23S rRNA genes. Of 24 strains examined, 15 different fingerprints were generated, and none was identical to fingerprints generated by previously identified groups of tumorigenic A. vitis strains. Results of physiological tests that were done to characterize strains from V. riparia conformed closely to those expected for A. vitis, except that 23 of 26 strains did not utilize tartrate. All strains were nontumorigenic, did not hybridize with a probe consisting of T-DNA genes, did not utilize octopine or nopaline, and carried zero to three plasmids. Of 26 strains, 7 inhibited A. vitis strain K306 from causing galls at wound sites on grape as well as or better than a previously studied nontumorigenic A. vitis strain, F2/5, that is known to have biological control activity.
RESUMEN
Shoot tips of potted Empire and Golden Delicious trees on the susceptible dwarfing rootstock M.26 in the greenhouse were injected with inoculum containing 5 × 109 CFU/ml Erwinia amylovora. At intervals after inoculation, trees were sampled at increments between the shoot tip and the roots by excising stem segments. Segments were ground in phosphate buffer and assayed for the presence of E. amylovora by plating on semi-selective medium and by a polymerase chain reaction (PCR)-based detection method. Eleven days after inoculation, E. amylovora was detected by PCR in symptomless scion tissue >50 cm below the shoot-tip in Empire and Golden Delicious, and in 2-year-old tissue in Golden Delicious. By 21 days, E. amylovora was detected in the M.26 rootstock of Empire trees, and by 41 days in the M.26 rootstock of Golden Delicious. In a similar experiment the following year, Empire trees on M.26 rootstock were inoculated with E. amylovora at early (16 May), mid- (11 June), and late (6 July) phenophase of shoots. Three weeks after inoculation, E. amylovora was detected by PCR from M.26 rootstocks of five of six plants inoculated at the late phenophase, compared to zero of six plants inoculated at the early or mid-phenophase. Late-season fire blight infections of the scion may be particularly hazardous for the health of the rootstock.
RESUMEN
The genetic diversity among 16 strains of Erwinia amylovora, chosen to represent different host plant origins and geographical regions, was investigated by RAPD analysis. One strain of Erwinia herbicola and one of Agrobacterium vitis were used as outgroups. Ninety-eight different RAPD fragments were produced by polymerase chain reaction amplification with six different 10-mer primers. RAPD banding profiles were found that enabled the Erw. amylovora strains to be distinguished from one another. Cluster analysis based on the number of RAPD fragments shared between strains showed that strains of Erw. amylovora isolated from subfamily Pomoideae formed a single group, whereas two strains from Rubus (subfamily Rosoideae) formed a second group. Two strains isolated from Asian pear on Hokkaido, Japan, formed a third group. Sets of RAPD fragments were identified that enabled each of the two host-range groups and one geographical region (Hokkaido) of Erw. amylovora strains to be unambiguously distinguished from one another and from the outgroups. This study shows that strains of Erw. amylovora exhibit genetic diversity detectable by RAPD analysis, and that molecular and statistical analysis of RAPD fragments can be used both to distinguish between strains and to determine relatedness between them.
Asunto(s)
Erwinia/clasificación , Erwinia/genética , Cartilla de ADN , ADN Bacteriano/análisis , Electroforesis en Gel de Poliacrilamida , Erwinia/aislamiento & purificación , Erwinia/patogenicidad , Variación Genética , Filogenia , Técnica del ADN Polimorfo Amplificado AleatorioRESUMEN
Russet on apple fruits was caused by inoculation with isolates of Aureobasidium pullulans and Rhodotorula glutinis but not with Metschnikowia pulcherrima or two other unidentified yeasts, YT2 and YT17. Another unidentified yeast, YT5, caused russet in 1 of 2 years. Epiphytic survival of isolates on fruit was measured 3 months after inoculation. All isolates that caused russet survived epiphytically on fruit at harvest. With the exception of M. pulcherrima, nonrusseting isolates were not detected on the fruit at harvest. Conidia, hyphae, and chlamydospores characteristic of A. pullulans were observed in naturally russeted tissues of 14 different apple cultivars and Bartlett and Bosc pear collected from 13 orchards in New York state. A. pullulans was the most commonly isolated microorganism, and all A. pullulans isolates caused apple russet but varied in the severity of russet they caused. Isolates were identified using standard identification schemes. In addition, A. pullulans isolates were compared by generating fingerprints of restriction fragments of a PCR-amplified region of ribosomal DNA consisting of ITS-1, the 5.8S gene, and ITS-2.
RESUMEN
[3H]Acetylcholine (ACh) synthesis was measured in primary neuronal cultures from neonatal rat brains. Neuronal [3H]ACh synthesis was blocked by hemicholinium-3 and depended on the age of the cultures, increasing for ca. 10 days, and eventually declining. The irreversible inhibitor AF64A (10 or 30 microM) inhibited [3H]ACh synthesis from [3H]choline at concentrations (10 or 30 microM) with affecting choline acetyltransferase activity. Nine-day-old cultures recovered 90% of their [3H]ACh synthesis within 7 days after AF64A, while 13-day-old cultures never recovered. These results suggest that the turnover of neuronal choline transporters is age-related.