Goat horns: Platforms for viroid transmission to fruit trees?

Mechanical inoculations with contaminating tools and propagation of infected budwood were considered the main causes for the omnipresence of multiple viroid species among citrus and other Middle Eastern and Mediterranean fruit trees and grapevines. However, neither means could explain viroid infections of wild trees — scattered on terrains inaccessible to humans — nor the finding of similar viroids among graft-incompatible plants. Northern hybridization of RNA extracts made of scrapings from the surfaces of goat (Capra hircus) horns that were rubbed against etrog (Citrus medica) stems infected with a citrus viroids complex, revealed accumulation of considerable amounts ofCitrus exocortis viroids (CEVd) andHop stunt viroids (HSVd). Experimental transmission of both CEVd and HSVd was obtained by rubbing healthy citrus plants with goat horns that had been rubbed 24 h earlier on infected etrog stems. These results implicate goats as possible vectors of viroids. Transmissionvia goats could have facilitated the long-range spread of viroids among cultivated and wild plants andvice versa and also among graft-incompatible plants.     

Phenotypic and genotypic analysis of a commercial cultivar and wild populations of Anemone coronaria

Seven wild populations of Anemonecoronaria were assessed for 11 phenotypic traits, most of them having economic value for the flower industry. The wild populations were sampled to represent the diversity in habitats, climates, rock and soil types, terrains, and elevations in Israel. AFLP analysis was carried out on 12 individuals from each of six out of the seven wild populations and for six individuals from the commercial cultivar ‘Mona-Lisa’. It was found that the Dorot population, which is located in the area bordering the semi-arid zone at the very end of the species distribution, exhibits extreme and different phenotypes with relatively low variability compared withthe other wild populations. The other six wild populations, that grow in more favorable geographic and climatic conditions exhibit phenotypes with larger plants, larger numbers of flowers and less dissected leaves. These populations were less uniform than that of Dorot. Genetic characterization by AFLP markers revealed a total of 165 bands. The wild populations exhibit wide variation within-population, with about 80% polymorphic bands and average gene diversity between pairs of about 30%. The Dorot population has the lowest genetic variation and the Megido population the highest. Thus, the phenotypic variation reflects the genetic variation. The cultivar ‘Mona-Lisa’, as expected, has much lower genetic variation. The Dorot population and the ‘Mona-Lisa’ cultivar were found to have the largest genetic distances from the other wild populations, and the highest genetic variation between themselves. Phenetic analysis yielded a dendrogram describing the genetic relatedness of these populations. This revised version was published online in August 2006 with corrections to the Cover Date.     

AIDS meeting. Companies, donors pledge to close gap in AIDS treatment

Although basic science and clinical research typically dominate at this biennial event, by far the most riveting sessions at the XIII International AIDS Conference here revolved around the thicket of issues that prevent poor people in sub-Saharan Africa--where a staggering 24.5 million people are estimated to be infected with HIV--from receiving the 14 anti-HIV treatments now used in wealthy countries. Pharmaceutical companies and donors last week loosed a flood of promises about removing barriers. Conference attendees welcomed the offers of help, but many stressed that much more will be needed.     

Anterior cingulate conflict monitoring and adjustments in control

Conflict monitoring by the anterior cingulate cortex (ACC) has been posited to signal a need for greater cognitive control, producing neural and behavioral adjustments. However, the very occurrence of behavioral adjustments after conflict has been questioned, along with suggestions that there is no direct evidence of ACC conflict-related activity predicting subsequent neural or behavioral adjustments in control. Using the Stroop color-naming task and controlling for repetition effects, we demonstrate that ACC conflict-related activity predicts both greater prefrontal cortex activity and adjustments in behavior, supporting a role of ACC conflict monitoring in the engagement of cognitive control.     

Low temperatures enhance winter wilt of pepper plants caused by Pythium sp.

Pepper is the main vegetable crop grown in the Arava region of southern Israel. It is grown in the winter in nethouses and greenhouses. Low temperature wilt of mature pepper plants has been known for years in this region. The incidence of plant wilting was usually low when the soil was pretreated with methyl bromide. In recent years methyl bromide usage has been banned and disease incidence has increased. The causal agent of this phenomenon was unknown until the current study. Pythium sp. was the most common microorganism genus isolated from wilted plant roots. Young pepper plants were artificially inoculated with Pythium isolated from wilted plants and maintained at temperatures of 20°, 14°, 10.5° and 8.6°C. Significant wilting was observed in plants grown at 8.6°C, with symptoms starting 2?weeks after inoculation. At 10.5°C wilting developed more slowly and inoculated plants maintained at 14° and 20°C did not exhibit any wilting symptoms. The unique variation in sporangium morphology and the sequence of the ribosomal internal transcribed spacer (ITS) suggest that a new species of Pythium is involved. The fungicide metalaxyl-M was found effective in controlling the disease in pot experiments. The relationship between low temperatures and high disease incidence can explain the high disease incidence in the Arava Valley of Israel during the cold winters of 1999?C2000, 2004?C2005 and 2006?C2007.     

Differential Activity of Carboxylic Acid Amide Fungicides Against Various Developmental Stages of Phytophthora infestans

ABSTRACT Three carboxylic acid amide (CAA) fungicides, mandipropamid (MPD), dimethomorph (DMM) and iprovalicarb (IPRO) were examined for their effects on various asexual developmental stages of Phytophthora infestans in vitro and in planta. Germination of cystospores and direct germination of sporangia were inhibited with nanomole concentrations of MPD (0.005 mug/ml) and micromole concentrations of DMM (0.05 mug/ml) or IPRO (0.5 mug/ml). A temporary exposure of 1 h to CAAs was not detrimental to germination and infectivity of sporangia or cystospores. CAAs applied to cystospores at 1 h after the onset of germination did not prevent the emergence of germ tubes, but inhibited their further growth and deformed their shape. None of the fungicides affected discharge of zoospores from sporangia or the encystment (cell wall formation/assembly) of the zoospores. Mycelium growth in solid or liquid media was inhibited with micromole concentrations. CAAs mixed with sporangia and drop inoculated onto detached leaves strongly suppressed infection. Curative application at 1 day postinoculation (dpi) required higher concentrations of CAAs than preventive application to inhibit infection and lost its effectiveness at 2 dpi. When sprayed on established late blight lesions 4 days after inoculation, CAAs reduced sporangial production in a dose-dependent manner. Trans-laminar protection of potato or tomato leaves, although achieved with higher doses, was more effective with MPD than with DMM or IPRO. Shade house studies demonstrated superior control of late blight epidemics by MPD compared with the other molecules. The data suggest that germ tube formation by cystospores or sporangia is the most sensitive stage in the life cycle of P. infestans to CAAs. Of the three CAAs, MPD had the highest intrinsic activity against spore germination. This property, together with its better trans-laminar activity, makes MPD more effective than DMM or IPRO in controlling epidemics caused by P. infestans.     

Sources of parathion exposures for Israeli aerial spray workers, 1977

Exposure of Israeli agricultural spray pilots and ground crews to parathion was studied. Measurements were made with personal samplers contianing wet midget impingers; samples were analyzed by gas chromatography. Cockpit air exposure levels during 11-21-minute sampling periods for 12 flights ranged from nearly 0 to 430 microgram/m3. During sampling periods of 30 minutes to 4 hours the threshold limit value (TLV) of 100 microgram/m3 was exceeded in 2 of 19 instances. In seven measurements of ground crew exposures, TLV was not exceeded. Air washing with parathion resulted in airborne contamination of the ground level area at more than three times the TLV. Skin exposure data suggested that this route of exposure was significant for ground crew workers but not for pilots. Calculations based on the present data and standard absorption formula suggested that total daily intake for ground crew, but not for pilots, exceeded the Accepted Daily Intake (ADI) of 5 microgram/kg body weight. Sources of exposure and contamination for ground crew and pilots were identified. Recommended environmental control measures for parathion exposure should include cockpit air filtration, modification in flight patterns, paving landing areas, installation of hosing and drainage, NaOH neutralization point, and separate loading and unloading sites. Personal control measures were suggested as a supplement.     

Antiviral effect of a factor from TMV-infected plants on the inoculativity of an insect vector

The capacity of whiteflies (Bemisia tabaci) to acquire and transmit tomato yellow leaf curl virus successfully is reduced if the insect is membrane-fed on a solution of an antiviral factor (AVF) from virus-infected plants. Whiteflies are known to have a native protective mechanism, involving at least two different factors. AVF was shown to act via the same pathway as the above-mentioned protective mechanism, since at least one of the above factors was induced in the insect body by AVF even in virus-free insects     

Thyroxine interaction with actinomycin D and possible biological implications

Actinomycin D and thyroxine interact in solution (pH 8 to 10), as revealed by changes in the absorbance of actinomycin D. Thyroxine can prevent the growth-inhibitory effect of actinomycin D on Bacillus subtilis if it is present in a molar ratio of 3000 (thyroxine to actinomycin D).