Seasonal development of ontogenic resistance to downy mildew in grape berries and rachises

ABSTRACT Clusters of Vitis vinifera and V. labrusca are reported to become resistant to Plasmopara viticola at stages of development ranging from 1 to 6 weeks postbloom. It has been suggested that resistance is associated with loss of the infection court as stomata are converted to lenticels, but the time of onset, cultivar variation, and seasonal variation in ontogenic resistance has remained uncertain, as has the comparative susceptibility of stem tissue within the fruit cluster. In New York, we inoculated clusters of V. vinifera cvs. Chardonnay and Riesling and V. labrusca cvs. Concord and Niagara at stages from prebloom until 5 to 6 weeks postbloom. Berries were infected and supported profuse sporulation until 2 weeks postbloom, and pedicel tissue remained susceptible until 4 weeks postbloom. Although berries on later-inoculated clusters failed to support sporulation, discoloration and necrosis of berry tissues was often noted, and necrosis of the pedicel within such clusters often led to further discoloration, shriveling, reduced size, or loss of berries. When the epidermis of discolored berries that initially failed to support sporulation was cut, the pathogen emerged and sporulated through incisions, indicating that lack of sporulation on older symptomatic berries was due to infection at an early stage of berry development followed by conversion of functional stomata to lenticels during latency. We repeated the study on Chardonnay and Riesling vines in South Australia and found that the period of berry and rachis susceptibility was greatly increased. The protracted susceptibility of the host was related to the increased duration and phenological heterogeneity of bloom and berry development in the warmer climate of South Australia. The time of onset and subsequent expression of ontogenic resistance to P. viticola may thus be modified by climate and should be weighed in transposing results from one climatic area to another. Our results can be used to refine forecast models for grapevine downy mildew to account for changes in berry and rachis susceptibility, and to focus fungicide application schedules upon the most critical periods for protection of fruit.     

Comparison of the pressing behaviour of wood particleboard and strawboard

To improve the understanding of strawboard manufacturing processes, mat pressing behaviour of wood particleboard and strawboard bonded with urea formaldehyde resins were experimentally investigated and compared in terms of mat compressibility, transverse permeability, mat pressure, core temperature, core gas pressure and vertical density profile. The results have shown that straw particles are much more compressible and therefore require less platen pressure for pressing. Compared to wood particle and refined straw particle mats, hammer milled straw mats have low permeability and subsequently show high core gas pressure and high maximum core temperature during hot pressing, in addition to large differential densities between surface and core layers in the final pressed boards. It is recommended that a slower press closing rate and longer press opening time be used to develop the strawboard pressing schedule.     

Practical cytology for inflammatory skin diseases

Cytology is the most common and immediately informative diagnostic tool in the practice of dermatology. It is simple to perform and requires equipment usually already present in most practices such as a microscope and slides, cotton-tipped applicators and stains. Cytology interpretation is also easily self taught. With little practice the practitioner can easily become familiar with sample interpretation from inflammatory lesions; including recognition of bacteria, yeast, dermatophyte spores and hyphae, deeper fungal elements and parasites. Additionally, the practitioner should become familiar with the variety of inflammatory cells seen with these conditions, as well as keratinocyte morphology. This article provides an overview and the initial steps on how to become a more proficient cytologist in practice.     

Estimates of deep percolation beneath cotton in the Macquarie Valley

Expansion of flood irrigation in the Lower Macquarie Valley of New South Wales, Australia, has been suggested as a major cause of increased groundwater recharge. The aim of this study was to estimate deep percolation under irrigation on two soils in the valley, in order to infer groundwater recharge. Three methods were used; water balance, Darcian flux calculations and chloride mass balance modelling. Chloride mass balance modelling and the water balance method gave comparable estimates of deep percolation for each soil. Chloride mass balance modelling was identified as the most reliable method for estimating deep percolation, but only gave an estimate for the entire growing season. These estimates were 214 and 104 mm for a cracking clay and red brown earth, respectively. While there is potentially greater error associated with estimates obtained using the water balance, this technique provided estimates of deep percolation for each individual irrigation. Results of the water balance indicated that deep percolation was greatest early in the growing season, following initial wetting of the soil, when the crop had a low leaf area index. Results calculated using Darcian flux equations were highly variable, and were therefore unreliable estimates of deep percolation. Groundwater recharge, inferred from estimates of deep percolation determined with the chloride mass balance model, was used to estimate the magnitude of potential annual groundwater rise. The potential groundwater rise during the 1992/1993 cotton growing season ranged from 465 mm beneath the cracking clay to 267 mm under the red brown earth. It is suggested that groundwater recharge and rise were highly dependent on the weather conditions prevailing during this period. Received: 24 January 1997     

Imaging of transient structures using nanosecond in situ TEM

The microstructure and properties of a material depend on dynamic processes such as defect motion, nucleation and growth, and phase transitions. Transmission electron microscopy (TEM) can spatially resolve these nanoscale phenomena but lacks the time resolution for direct observation. We used a photoemitted electron pulse to probe dynamic events with "snapshot" diffraction and imaging at 15-nanosecond resolution inside of a dynamic TEM. With the use of this capability, the moving reaction front of reactive nanolaminates is observed in situ. Time-resolved images and diffraction show a transient cellular morphology in a dynamically mixing, self-propagating reaction front, revealing brief phase separation during cooling, and thus provide insights into the mechanisms driving the self-propagating high-temperature synthesis.     

Influence of environment on growing period and yield, protein, oil and α-linolenic content of three chia (Salvia hispanica L.) selections

Chia (Salvia hispanica L.) is an annual summer herb, and a member of the Labiatae family. Three selections, named Tzotzol, Iztac 1, and Tliltic, were planted at different elevations in three Inter-Andean valleys of Ecuador (Patate—2042 m, Guayllabamba—2200 m and Salinas—1621 m) to assess performance and seed quality. Length of growing period was influenced by location, with Tzotzol and Iztac 1 increasing with elevation. Iztac 1 had the highest seed yield at all three locations, with the difference between Iztac1 and Tzotzol being significant (P < 0.05). Similar protein contents were found among selections, within a site, except for Patate where Tliltic had a higher content. Seed at the Salinas site contained significantly (P < 0.05) higher α-linolenic and lower linoleic and oleic fatty acid contents than seed produced at the other two sites. In general seed yield, protein content, and fatty acid composition of the three selections were similar, and in some cases higher, than those reported for other ecosystems in which chia has been grown.     

Large volume cold on-column injection for gas chromatography-negative chemical ionization-mass spectrometry analysis of selected pesticides in air samples

A new gas chromatographic method is described for the analysis of fungicides captan, captafol, and folpet from organic extracts of air samples using large volume injection (LVI) via a cold on-column (COC) inlet coupled with gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS). Although standard split/splitless injection due to high injection port temperatures (>225 degrees C) have been shown to degrade these thermally labile fungicides, COC injection minimizes degradation. Insecticides such as chlorpyrifos and diazinon were also examined to show added selectivity. By using a solvent vapor exit with the COC inlet, injection volumes of 10-100 microL can be made to lower detection levels. GC-NCI-MS was compared to GC-electron impact ionization-mass spectrometry for each pesticide using LVI-COC injections and was found to be 2-80 times more sensitive, depending on the pesticide. Method detection limit (MDL) values with 100 microL injections were 2.5 microg L-1 for captan, folpet, and diazinon, 5.0 microg L-1 captafol, and 1.0 microg L-1 for chlorpyrifos, with the normal working range examined for sample analysis from MDL to 100 microg L-1. Detection of all pesticides except captafol, used only in the United States but not Canada, was demonstrated from air samples taken from Abbotsford, British Columbia, Canada.     

Digestibilities of the protein in various foods as determinedin vitro by an immobilized digestive enzyme assay (IDEA)

The digestibility of the protein in various foods or food components was analyzed using an immobilized digestive enzyme assay (IDEA) system. The assay consists of two bioreactors, one containing pepsin and the other containing trypsin, chymotrypsin and intestinal mucosa peptidases. The fraction of the peptide bonds hydrolyzed during an extent of hydrolysis assay was correlated with independentin vivo determinations of the digestibilities. A correlation coefficient of 0.80 was obtained. The derived linear regression equation can be used to predict digestibility. The method is sensitive to structural modification of protein, as for example, those caused by effects of heat treatment.Paper No. 11032 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 27695-7601. The use of trade names does not imply endorsement by the North Carolina Research Service of the products.     

Photoinduced plasticity in cross-linked polymers

Chemically cross-linked polymers are inherently limited by stresses that are introduced by post-gelation volume changes during polymerization. It is also difficult to change a cross-linked polymer's shape without a corresponding loss of material properties or substantial stress development. We demonstrate a cross-linked polymer that, upon exposure to light, exhibits stress and/or strain relaxation without any concomitant change in material properties. This result is achieved by introducing radicals via photocleavage of residual photoinitiator in the polymer matrix, which then diffuse via addition-fragmentation chain transfer of midchain functional groups. These processes lead to photoinduced plasticity, actuation, and equilibrium shape changes without residual stress. Such polymeric materials are critical to the development of microdevices, biomaterials, and polymeric coatings.     

Ancient DNA evidence for Old World origin of New World dogs

Mitochondrial DNA sequences isolated from ancient dog remains from Latin America and Alaska showed that native American dogs originated from multiple Old World lineages of dogs that accompanied late Pleistocene humans across the Bering Strait. One clade of dog sequences was unique to the New World, which is consistent with a period of geographic isolation. This unique clade was absent from a large sample of modern dogs, which implies that European colonists systematically discouraged the breeding of native American dogs.