Bacterial pathogens of rice in the Kingdom of Cambodia and description of a new pathogen causing a serious sheath rot disease

A study of rice diseases in Cambodia from 2005 to 2007 showed widespread occurrence of diseases caused by Acidovorax avenae subsp. avenae, Burkholderia gladioli, B. cepacia and Pantoea ananatis. This is the first report of these pathogens in Cambodia. Additionally, a pseudomonad causing a widespread disease similar to sheath brown rot (caused by Pseudomonas fuscovaginae) was isolated. The studied strains were pathogenic to rice cvs Sen Pidau and IR 66, producing similar, though slightly less severe, symptoms to those observed in the field. Based on comparative 16S rDNA gene sequence analysis, combined with cell wall fatty acid analysis and metabolic profiles, the isolated strains were allocated to the genus Pseudomonas. The novel species were differentiated from Pseudomonas fuscovaginae and P. putida by their inability to metabolize d ‐fructose, d ‐galactose, d ‐galactonic acid lactone, d ‐galacturonic acid, d ‐glucosaminic acid, d ‐glucuronic acid, p‐hydroxy phenylacetic acid, d ‐saccharic acid and urocanic acid. The major fatty acids were C_16:0, summed feature 3 (C_16:1ω7c and C_16:1ω6c) and summed feature 8 (C_18:1ω7c), representing 80% of the total. Partial 16S rRNA gene sequences (1460 bp) were identical, except for two nucleotide changes amongst the six strains. Alignment of the causal strains within type‐culture databases revealed similarities of 99·7% with Pseudomonas parafulva AJ 2129^T, 99·2% with P. fulva IAM 1592^T, 98·9% with P. plecoglossicidia FPC 951^T, and 98·1% with P. fuscovaginae MAFF 301177^T. On the basis of data from this polyphasic study, it is proposed that the unknown strains isolated from rice represent a novel species of the genus Pseudomonas.     

Occurrence of 2n gametes in the F1 hybrids of Oriental × Asiatic lilies (Lilium): Relevance to intergenomic recombination and backcrossing

Cytological modes of the origin of 2n gametes were investigated in six different genotypes of F₁ hybrids between Oriental and Asiatic (OA) lilies (Lilium, 2n = 2x = 24). Chromosome pairing between the parental genomes was very low, the average frequency range from 0.3 to 1.2 bivalents per cell among the genotypes. Within a genotype the frequency of bivalents varied from 0 to 6 in some cases. The normally occurring haploid pollen grains were totally sterile. In contrast, in different genotypes, variable percentages of 2n pollen were found and shown to be fertile as estimated from pollen germination. A cytological analysis of Metaphase I and subsequent stages of meiosis using genomic in situ hybridization (GISH) revealed that there was intergenomic recombination between the alien genomes. Following Metaphase I stage, three different types of abnormal cytological events led to the formation of 2n pollen: (i) Post-Metaphase I division (PMI), (ii) Post-Metaphase II division (PMII) and (iii) Asymmetric Cytokinesis of the pollen mother cell followed by chromosome division. All three cytological events led to first division restitution (FDR) gametes. Based on in vitro pollen germination it was proved for two genotypes that 2n pollen was viable only during the first day of anthesis. It was possible to use 2n pollen successfully for backcrossing. Implications of 2n pollen for intergenomic recombination in BC₁ progenies are discussed.     

Influence of fertilization on acrylamide formation during frying of potatoes harvested in 2003

The quality of the potato has been found to vary, when grown under different agricultural and environmental conditions, such as the level of fertilization. Consequently these factors may influence the acrylamide formation during the preparation of French fries. These assumptions were studied on three varieties: Bintje, Ramos, and Saturna from the harvest of 2003. Decreasing N fertilization caused increases in the reducing sugar concentration from 60% up to 100% on DM for all varieties studied. Due to a high correlation between the reducing sugar content and the generation of acrylamide during frying, this resulted in a parallel increase in the acrylamide concentration of the French fries. Thus by lowering the amount of N fertilizer, an increase of 30-65% of the acrylamide generation during frying could be observed. It seems of extreme importance to find an appropriate balance between the level of N fertilizer in order to diminish acrylamide formation but on the other hand to obtain an acceptable tuber and to consider the environmental impact. All results reported should be seen in the perspective of the warm growing season of 2003.     

Origin of Clostridium perfringens isolates determines the ability to induce necrotic enteritis in broilers

Since the ban on growth-promoting antibiotics in animal feed in the European Union, necrotic enteritis has become a major cause of mortality in broiler chickens. Despite the importance of the disease, the pathogenesis is still not completely understood. In the current study, Clostridium perfringens strains isolated from healthy flocks and isolates from outbreaks of necrotic enteritis were evaluated for the ability to cause gut necrosis in an intestinal loop model in laying hens and in an experimental infection model in broilers. High, intermediate and low alpha toxin producing strains were chosen from each isolation source. Only the isolates from field outbreaks induced necrotic gut lesions, independent of the amount of alpha toxin produced in vitro. It was also shown that alpha toxin producing isolates from calf hemorrhagic enteritis cases were not able to induce necrotic enteritis in poultry. These results suggest the presence of host specific virulence factors in C. perfringens strains, isolated from chickens with intestinal necrotic enteritis lesions.     

Measurement of tidal volume using Respiratory Ultrasonic Plethysmography in anaesthetized,mechanically ventilated horses

ObjectiveTo compare tidal volume estimations obtained from Respiratory Ultrasonic Plethysmography (RUP) with simultaneous spirometric measurements in anaesthetized, mechanically ventilated horses.Study designProspective randomized experimental study.AnimalsFive experimental horses.MethodsFive horses were anaesthetized twice (1 week apart) in random order in lateral and in dorsal recumbency. Nine ventilation modes (treatments) were scheduled in random order (each lasting 4 minutes) applying combinations of different tidal volumes (8, 10, 12 mL kg^?1) and positive end-expiratory pressures (PEEP) (0, 10, 20 cm H₂O). Baseline ventilation mode (tidal volume = 15 mL kg^?1, PEEP = 0 cm H₂O) was applied for 4 minutes between all treatments. Spirometry and RUP data were downloaded to personal computers. Linear regression analyses (RUP versus spirometric tidal volume) were performed using different subsets of data. Additonally RUP was calibrated against spirometry using a regression equation for all RUP signal values (thoracic, abdominal and combined) with all data collectively and also by an individually determined best regression equation (highest R²) for each experiment (horse versus recumbency) separately. Agreement between methods was assessed with Bland-Altman analyses.ResultsThe highest correlation of RUP and spirometric tidal volume (R² = 0.81) was found with the combined RUP signal in horses in lateral recumbency and ventilated without PEEP. The bias ± 2 SD was 0 ± 2.66 L when RUP was calibrated for collective data, but decreased to 0 ± 0.87 L when RUP was calibrated with individual data.Conclusions and clinical relevanceA possible use of RUP for tidal volume measurement during IPPV needs individual calibration to obtain limits of agreement within ± 20%.     

Seasonal interaction of serum vitamin D concentration and bone density in alpacas

OBJECTIVE: To evaluate temporal changes in bone mineral density associated with seasonal variation in serum vitamin D, calcium, and phosphorus concentrations in alpacas. ANIMALS: 5 healthy mature neutered male alpacas. PROCEDURE: Metacarpal bone mineral density was measured at 4 times during a year. Each time alpacas were weighed, blood was collected for determination of serum calcium, phosphorus, and vitamin D concentrations, and samples of feed were analyzed for nutrient content. Vitamin D status was determined by use of an assay that measured serum 25-hydroxycalciferol concentration. Effects of changes in serum vitamin D, calcium, and phosphorus concentration and body weight with season on bone mineral density were determined. RESULTS: Bone mineral density, body weight, and serum vitamin D and phosphorus concentrations varied with season. Bone mineral density, serum vitamin D concentration, and body weight also varied among individual alpacas. Serum vitamin D concentration was lower in January than the previous October and increased from May to the following September. The decrease in bone mineral density lagged behind the decrease in serum vitamin D concentration and was lower in May, compared with the previous October. Body weight was lower in May than the previous October or following September. Solar radiation was highest in July and lowest in December. CONCLUSIONS AND CLINICAL RELEVANCE: Seasonal changes in bone mineral density are associated with changes in serum vitamin D concentrations in alpacas. Changes in bone mineral density associated with a decline in serum vitamin D concentration may predispose some alpacas to developing fractures minimal trauma.     

Effects of a short period of drought on changes in tuber volume and specific leaf weight. II. Diurnal changes

Summary Single-stemmed potato plants, cv. Bintje, were grown on a nutrient solution under controlled conditions. They were exposed to a short drought stress, or remained untreated. Short-term changes in tuber volume and in specific leaf weight were measured non-destructively. Tubers from control plants increased rapidly in volume during the night and did not grow, or even shrivelled during the day. Tubers of stressed plants did not show a uniform response; some tubers markedly declined in volume during the day. The patterns of volume increase of stressed plants became erratic after the stress, mainly because some plants never fully recovered. Patterns of diurnal fluctuation in tuber volume were similar to diurnal changes in specific leaf weight; tubers within the same stressed plant sometimes reacted differently. In these cases the effects on the diurnal fluctuation partly reflected the long-term effects, reported in an earlier paper.