Susceptibility of Lenticels within the Stem Depression of Tomato Fruit to Bacterial Soft Rot.

The postharvest development of bacterial soft rot in tomato fruit caused by Pectobacterium carotovorum is herein linked with inoculation of lenticel-like apertures located around the stem attachment. Stem scars misted with aqueous cell suspensions of P. carotovorum (1 × 106 CFU/ml) or briefly (5 s) immersed in the suspension were likely to become infected during subsequent storage, with a disease incidence exceeding 70% within 7 days at 24°C. Water soaking was initially observed beneath the fruit surface at the juncture of radial walls of endocarp tissues and a corky ring around the stem attachment. If fruit were swirled for 1 min in chlorine at 150 ppm, pH 6.5, within 5 s after inoculation, lesions did not occur. However, if the chlorine treatment was delayed by 120 s, lesions occasionally developed. A 60-min delay usually assured that decay would occur before fruit ripened (within 5 days). Delaying the chlorine wash by 18 h, as would occur if commercial harvests were held overnight prior to packing operations, led to the same incidence of bacterial soft rot as observed among control fruit. Inoculation of fruit with attached stems did not lead to as much decay during storage compared with stemless fruit, suggesting that an intact calyx physically reduced lenticel exposure to external aqueous cell suspensions. Tomato fruit exposed to uncontrolled free moisture during or shortly after harvest have a high potential for postharvest decays and the likely site for infection development is the area surrounding the stem attachment.

Variation in the mu-opioid receptor gene (OPRM1) moderates the influence of maternal sensitivity on child attachment.

The endogenous opioid system is thought to play an important role in mother-infant attachment. In infant rhesus macaques, variation in the µ-opioid receptor gene (OPRM1) is related to differences in attachment behavior that emerges following repeated separation from the mother; specifically, infants carrying at least one copy of the minor G allele of the OPRM1 C77G polymorphism show heightened and more persistent separation distress, as well as a pattern of increased contact-seeking behavior directed towards the mother during reunions (at the expense of affiliation with other group members). Research in adult humans has also linked the minor G allele of the analogous OPRM1 A118G polymorphism with greater interpersonal sensitivity. Adopting an interactionist approach, we examined whether OPRM1 A118G genotype and maternal (in)sensitivity are associated with child attachment style, predicting that children carrying the G allele may be more likely to develop an ambivalent attachment pattern in response to less sensitive maternal care. The sample consisted of 191 mothers participating with their children (n = 223) in the Maternal Adversity, Vulnerability and Neurodevelopment (MAVAN) project, a community-based, birth cohort study of Canadian mothers and their children assessed longitudinally across the child's development. Maternal sensitivity was coded from at-home mother-child interactions videotaped when the child was 18 months of age. Child attachment was assessed at 36 months using the Strange Situation paradigm. As predicted, G allele carriers, but not AA homozygotes, showed increasing odds of being classified as ambivalently attached with decreasing levels of maternal sensitivity. Paralleling earlier non-human animal research, this work provides support for the theory that endogenous opioids contribute to the expression of attachment behaviors in humans.

Control of Postharvest Botrytis Fruit Rot with Preharvest Fungicide Applications in Annual Strawberry.

The control of postharvest Botrytis fruit rot was evaluated during 1997-98 and 1998-99. Weekly applications of captan and thiram were examined at two or three different rates, respectively. Iprodione applications were combined with the captan and thiram treatments and also applied alone for two peak bloom periods. Strawberry fruit were harvested and graded twice weekly for marketable yield and preharvest incidence of Botrytis fruit rot. For postharvest evaluations, fruit from four harvests were selected and stored at 4°C, and Botrytis fruit rot incidence was recorded over 14 days of storage. Fungicide treatments reduced the incidence of preharvest Botrytis fruit rot and increased marketable yield. The incidence of postharvest Botrytis fruit rot was significantly affected by harvest date, length of time in storage, and fungicide treatment. The highest rate captan and thiram treatments had the least Botrytis fruit rot and the longest storage life. Reduced-rate captan and thiram treatments generally did not provide the same control as their respective high-rate treatments. Iprodione added to either the captan or thiram treatments did not consistently reduce the preharvest or postharvest incidence of Botrytis fruit rot or increase yield. Regular, full-rate fungicide treatments appear to be necessary to control Botrytis fruit rot in Florida and to provide the storage life necessary to reach distant markets.

Chlorine Concentration and the Inoculation of Tomato Fruit in Packinghouse Dump Tanks.

Chlorine concentrations (pH 6 to 7 and 22 to 27°C) that killed arthrospores (spores) of Geotrichum candidum or sporangioles (spores) of Rhizopus stolonifer, causal agents of sour rot and Rhizopus rot, respectively, in moving water within 30 to 45 s did not prevent these pathogens from inoculating wounded tomatoes (Lycopersicon esculentum) in a water flume containing chlorine and spores. Free chlorine concentrations of 20 or 25 mg/liter were lethal to spores of G. candidum within 30 s in most in vitro tests, whereas spores of R. stolonifer were slightly less sensitive. Wounded tomatoes placed in a flume with free chlorine at 30 mg/liter and then exposed to spores for 1 min developed about 50% less decay incidence during storage at 24°C for 6 days than did fruit exposed to spores and water alone. In the absence of chlorine, incidence averaged 57% (range, 15 to 95%) for R. stolonifer and 38% (range, 17 to 58%) for G. candidum. Sporadic sour rot lesions were observed among fruit that had been treated with free chlorine at 75 mg/liter, whereas chlorine at up to 180 mg/liter failed to completely protect fruit from Rhizopus rot. A water-soluble dye rapidly penetrated wounds on tomato fruit. The dye framed the outlines of cells at the wound surface and appeared to penetrate into a few intercel-lular spaces. Application of 1% sodium hypochlorite decolorized the dye on the wound surface, whereas deposits located below the wound surface remained blue. Thus, spores suspended in moving water can escape the action of chlorine if carried into intercellular spaces by diffusion or by capillary movement of cell sap and water.

Automatic neutron dosimetry system based on fluorescent nuclear track detector technology.

For the first time, the authors are describing an automatic fluorescent nuclear track detector (FNTD) reader for neutron dosimetry. FNTD is a luminescent integrating type of detector made of aluminium oxide crystals that does not require electronics or batteries during irradiation. Non-destructive optical readout of the detector is performed using a confocal laser scanning fluorescence imaging with near-diffraction limited resolution. The fully automatic table-top reader allows one to load up to 216 detectors on a tray, read their engraved IDs using a CCD camera and optical character recognition, scan and process simultaneously two types of images in fluorescent and reflected laser light contrast to eliminate false-positive tracks related to surface and volume crystal imperfections. The FNTD dosimetry system allows one to measure neutron doses from 0.1 mSv to 20 Sv and covers neutron energies from thermal to 20 MeV. The reader is characterised by a robust, compact optical design, fast data processing electronics and user-friendly software.

Ion track reconstruction in 3D using alumina-based fluorescent nuclear track detectors.

Fluorescent nuclear track detectors (FNTDs) based on Al2O3: C, Mg single crystal combined with confocal microscopy provide 3D information on ion tracks with a resolution only limited by light diffraction. FNTDs are also ideal substrates to be coated with cells to engineer cell-fluorescent ion track hybrid detectors (Cell-Fit-HD). This radiobiological tool enables a novel platform linking cell responses to physical dose deposition on a sub-cellular level in proton and heavy ion therapies. To achieve spatial correlation between single ion hits in the cell coating and its biological response the ion traversals have to be reconstructed in 3D using the depth information gained by the FNTD read-out. FNTDs were coated with a confluent human lung adenocarcinoma epithelial (A549) cell layer. Carbon ion irradiation of the hybrid detector was performed perpendicular and angular to the detector surface. In situ imaging of the fluorescently labeled cell layer and the FNTD was performed in a sequential read-out. Making use of the trajectory information provided by the FNTD the accuracy of 3D track reconstruction of single particles traversing the hybrid detector was studied. The accuracy is strongly influenced by the irradiation angle and therefore by complexity of the FNTD signal. Perpendicular irradiation results in highest accuracy with error of smaller than 0.10°. The ability of FNTD technology to provide accurate 3D ion track reconstruction makes it a powerful tool for radiobiological investigations in clinical ion beams, either being used as a substrate to be coated with living tissue or being implanted in vivo.

Growth and Survival of Salmonella montevideo on Tomatoes and Disinfection with Chlorinated Water.

The survival on tomato fruits ( Lycopersicum esculentum ) of a rifampicin-resistant strain of Salmonella montevideo (Centers for Disease Control and Prevention [CDC] isolate G4639), the alleged source of the 1993 multistate outbreak of salmonellosis, was affected by inoculum dose and inoculation site (unbroken surface or wounds and stem scars), as well as by the medium (distilled water, Butterfield's buffer, or trypticase soy broth [TSB]) used to deliver the bacterium, This bacterium inoculated at 4 log10 CFU (colony forming units) per site in distilled water survived for 20 h on tomato skin. However, comparable survival occurred at the stem scars and growth cracks with smaller inoculum doses (3 log10 CFU). The bacterial populations increased rapidly on puncture wounds and tomato slices but decreased on the unbroken surface and stem scar. With unbroken skin and approximately 4 log10 CFU per site, the population survived for at least 48 h but could not be consistently detected after 5 days. By contrast, the stem scar population survived for at least 7 days and decreased only 1 to 2 log10 units. The inherently low pH of the tomatoes did not inhibit bacterial growth. Treatment with 100 ppm of aqueous chlorine for up to 2 min failed to kill all bacteria at these inoculation sites. This was especially true when the bacterial suspensions were prepared in TSB. TSB supported better bacterial survival and/or growth and also protected against the bactericidal effect of aqueous chlorine.