The reproductive potential of the root-knot nematode <Emphasis Type="Italic">Meloidogyne incognita</Emphasis> is affected by selection for virulence against major resistance genes from tomato and pepper

The emergence of virulent root-knot nematode populations, able to overcome the resistance conferred by some of the resistance genes (R-genes) in Solanaceous crops, i.e., Mi(s) in tomato, Me(s) in pepper, may constitute a severe limitation to their use in the field. Research has been conducted to evaluate the durability of these R-genes, by comparing the reproduction of several laboratory-selected and wild virulent Meloidogyne incognita isolates, on both susceptible and resistant tomatoes and peppers. We first show that the Me1 R-gene in pepper behaves as a robust R-gene controlling avirulent and virulent Me3, Me7 or Mi-1 isolates. Although the reproductive potential of the virulent isolates was highly variable on susceptible and resistant plants, we also confirm that virulence is highly specific to a determined R-gene on which selection has occurred. Another significant experimental result is the observation that a reproductive fitness cost is associated with nematode virulence against Mi-1 in tomato and Me3 and Me7 in pepper. The adaptative significance of trade-offs between selected characters and fitness-related traits, suggests that, although the resistance can be broken, it may be preserved in some conditions if the virulent nematodes are counter-selected in susceptible plants. All these results have important consequences for the management of plant resistance in the field.     

The bryophyte layer in a calcareous grassland after a decade of contrasting mowing regimes

Analysis of variance and redundancy analysis were used to study the effects of mowing regime and herb canopy structure on the bryophyte layer of a calcareous grassland in southern Belgium. Species richness in mown and control plots did not significantly differ. In control plots, a number of grassland species were able to survive within a grassy-shrubby fringe 15 years after shrub cutting. This suggests that there might be a time-lag of at least 20 years before cessation of mowing results in a significant decrease in species number per m². Mown plots were mostly characterized by the almost complete cover of large pleurocarps. Mowing resulted in almost continuous herb and moss layers that were unfavourable for a number of annual bryophytes, many of which are of high conservation interest. It is suggested that grazing, which increases the number of species, especially the number of pioneers, is likely to be more beneficial to bryophytes.     

Heterocyclic acetals from glycerol and acetaldehyde in Port wines: evolution with aging

In Port wine, isomers of glycerol and acetaldehyde acetals have been found at total contents ranging from 9.4 to 175.3 mg/L. During oxidative aging, the concentrations of the 5-hydroxy-2-methyl-1,3-dioxane and 4-hydroxymethyl-2-methyl-1,3-dioxolane isomers increased with time showing a linear correlation (r > 0.95). The flavor threshold for the mixture of the four isomers was evaluated in wine at 100 mg/L. Thus, it is expected that they contribute to "old Port wine" aroma in wines older than 30 years. Experiments with model solutions and wine clearly demonstrated that SO(2) combines with acetaldehyde and blocks the acetalization reaction.     

Effects of hydrophilic plasticizers on mechanical, thermal, and surface properties of chitosan films

Chitosan films were plasticized with four hydrophilic compounds, namely, glycerol (GLY), ethylene glycol (EG), poly(ethylene glycol) (PEG), and propylene glycol (PG). Our objective was to investigate the effect of plasticizers on mechanical and surface properties of chitosan films. The stability of plasticized films was observed by storage for 3 and 20 weeks in an environmental chamber at 50 +/- 5% RH and 23 +/- 2 degrees C. Plasticization improves the chitosan ductility, and typical stress-strain curves of plasticized films have the features of ductile materials, except the film made with 5% PG that exhibits as a brittle polymer and shows an antiplasticization effect. In most cases, the elongation of plasticized films decreases with the storage time, which might be due to the recrystallization of chitosan and the loss of moisture and plasticizer from the film matrix. Although at the beginning the mechanical properties of films made with PG, at high plasticizer concentration, are comparable to those of films made with EG, GLY, and PEG, their stability is poor and they tend to become brittle materials. The surface properties, analyzed by contact angle measurement, reveal that plasticization increases film hydrophilicity. It is found that GLY and PEG are more suitable as chitosan plasticizers than EG and PG by taking into account their plasticization efficiency and storage stability. Furthermore, a plasticizer concentration of 20% (w/w) with GLY or PEG seemingly is sufficient to obtain flexible chitosan film with a good stability for 5 months of storage.     

Volatile constituents of Semnostachya menglaensis Tsui

Semnostachya menglaensis Tsui (Acanthaceae) is a rare plant indigenous to Mengla in the tropical rainforest of the Xishuangbanna prefecture in the south of Yunnan province, People's Republic of China. When the leaves are crushed, a characteristic smell of basmati rice or pandan leaves develops. Their hexane extract, prepared from a specimen growing in a greenhouse of the botanical garden of the Kunming Institute of Botany, contains 1-(3,4,5,6-tetrahydro-2-pyridyl)-1-propanone (41.2%) and 1-(1,4,5,6-tetrahydro-2-pyridyl)-1-propanone (37.5%) which constitute the main part of the volatile compounds. Minor components are 1-(3,4,5,6-tetrahydro-2-pyridyl)-1-ethanone (4.9%), 1-(1,4,5,6-tetrahydro-2-pyridyl)-1-ethanone (4.8%), 1-(2-piperidyl)-1-propanone (5.2%), 1-octen-3-ol (3.2%), 1-octen-3-one (1.9%), and 3-octanol and 1-(2-pyridyl)-1-propanone in trace amounts.     

Impact of Water Stress on Maize Grown Off-Season in a Subtropical Environment

During the last decade, the production of off‐season maize has increased in several regions of Brazil. Growing maize during this season, with sowing from January through April, imposes several climatic risks that can impact crop yield. This is mainly caused by the high variability of precipitation and the probability of frost during the reproduction phases. High production risks are also partially due to the use of cultivars that are not adapted to the local environmental conditions. The goal of this study was to evaluate crop growth and development and associated yield, yield components and water use efficiency (WUE) for maize hybrids with different maturity ratings grown off‐season in a subtropical environment under both rainfed and irrigated conditions. Three experiments were conducted in 2001 and 2002 in Piracicaba, state of São Paulo, Brazil with four hybrids of different maturity duration, AG9010 (very short season), DAS CO32 and Exceler (short season) and DKB 333B (normal season). Leaf area index (LAI), plant height and dry matter were measured approximately every 18 days. Under rainfed conditions, the soil water content in the deeper layers was reduced, suggesting that the extension of the roots into these layers was a response to soil water limitations. On average, WUE varied from 1.45 kg m⁻³ under rainfed conditions to 1.69 kg m⁻³ under irrigated conditions during 2001. The average yield varied from 4209 kg ha⁻¹ for the hybrids grown under rainfed conditions to 5594 kg ha⁻¹ under irrigated conditions during 2001. Yield reductions under rainfed conditions were affected by the genotype. For the hybrid DKB 333B with a normal maturity, yield was reduced by 25.6 % while the short maturity hybrid Exceler was the least impacted by soil water limitations with a yield reduction of only 8.4 %. To decrease the risk of yield loss, the application of supplemental irrigation should be considered by local farmers, provided that this practice is not restricted by either economic considerations or the availability of sufficient water resources.     

Experimental use of polyamide bands in combination with intramedullary pinning for repair of oblique femoral fractures in rabbits

OBJECTIVE: To evaluate the use of polyamide bands, manufactured for securing electrical cables, for repair of oblique femoral fractures in rabbits. STUDY DESIGN: Experimental study. ANIMALS: Twelve nulliparous, 21-25-week-old, California female rabbits. METHODS: Rabbits were divided into 3 groups (n=4) and studied for 14, 28, or 56 days. A Z-shaped mid-diaphyseal femoral osteotomy was repaired with a 2.5 mm intramedullary pin and a polyamide 6.6 cerclage band. Healing was evaluated at intervals by physical examination, limb use, femoral radiographs, and callus histology. RESULTS: Rabbits had early limb use with good wound healing. From the 1st day, movement of the hip and stifle joints was satisfactory. Radiographically, fractures were healed at 28 days. Histologically, there was no foreign body reaction and bone healing was normal. CONCLUSION: Nylon cerclage band application was accomplished easily, maintained reduction, and resulted in good healing and limb use. CLINICAL RELEVANCE: Sterilized nylon bands, manufactured for electrical use, can be used for cerclage in rabbits.     

ULTRASONOGRAPHIC EXAMINATION OF THE THYROID GLAND OF HYPERTHYROID CATS: COMPARISON TO 99mTcO−4 SCINTIGRAPHY

High-resolution ultrasonography was evaluated as an alternative to ^99mTcO^-₄ scintigraphy for examining size and appearance of thyroid glands in hyperthyroid cats. Thyroid ultrasound examinations were performed on 6 normal cats and 14 cats with hyperthyroidism. Thyroid lobe volume was estimated from ultrasound images using the equation for a prolate ellipsoid, π/6 (length * height * width). Total thyroid volume was estimated by adding the volume estimations of the left and right lobes. Thyroid lobes of hyperthyroid cats were considered abnormal if estimated volume exceeded the 99% confidence interval for normal thyroid volume determined from the control group. Scintigraphic examinations performed on hyperthyroid cats were evaluated for unilateral versus bilateral disease and for the presence of ectopic activity. Mean thyroid lobe volume and total thyroid volume for normal cats was 85 and 169 mm³, respectively. Mean thyroid lobe volume and total thyroid volume for hyperthyroid cats was 578 and 889 mm³. There was a significant difference in mean estimated total thyroid volume of normal and hyperthyroid cats. Thyroid lobes with greater than normal TcO^-₄ uptake on scintigraphy were larger and had variable homogeneity, echogenicity, and margination on ultrasound examination. There also was an 85.7% agreement of scintigraphy and ultrasonography in differentiating normal from abnormal thyroid lobes. A fair correlation between estimated total thyroid volume of hyperthyroid cats and most recent pretherapy serum thyroxine values were also found. This preliminary study indicates that thyroid ultrasound examination may provide information that is useful for diagnosis and treatment of feline hyperthyroidism. Although ultrasound provides accurate evaluation of the thyroid glands, it cannot replace ^99mTcO^-₄ scintigraphy for screening of metastatic lesions and ectopic glands.