Novel bioassay using Bacillus megaterium to detect tetracyclines in milk

[EN] Tetracyclines are used for the prevention and control of dairy cattle diseases. Residues of these drugs can be excreted into milk. Thus, the aim of this study was to develop a microbiological method using Bacillus megaterium to detect tetracyclines (chlortetracycline, oxytetracycline and tetracycline) in milk. In order to approximate the limits of detection of the bioassay to the Maximum Residue Limit (100 g/l) for milk tetracycline, different concentrations of chloramphenicol (0, 1000, 1500 and 2000 g/l) were tested. The detection limits calculated were similar to the Maximum Residue Limits when a bioassay using B. megaterium ATCC 9885 spores (2.8 × 108 spores/ml) and chloramphenicol (2000 g/l) was utilized. This bioassay detects 105 g/l of chlortetracycline, 100 g/l of oxytetracycline and 134 g/l of tetracycline in 5 h. Therefore, this method is suitable to be incorporated into a microbiological multi-residue system for the identification of tetracyclines in milk.This research work has been carried out as part of the CAI + D'11 Projects (PI 501 201101 00575 LI, H.C.D. Resol 205/13 Universidad Nacional del Litoral, Santa Fe, Argentina) and PICT 2011-368 (Res. No 140/12, Agencia Nacional de Promocion Cientifica y Tecnologica).Tumini, M.; Nagel, OG.; Molina Pons, MP.; Althaus, RL. (2016). Novel bioassay using Bacillus megaterium to detect tetracyclines in milk. Revista Argentina de Microbiología. 48(2):143-146. https://doi.org/10.1016/j.ram.2016.02.001S14314648

Performance comparison of dwarf laying hens segregating for the naked neck gene in temperate and subtropical environments

This study compares laying performances between two environments of dwarf laying hen lines segregating for the naked neck mutation (NA locus), a selected dwarf line of brown-egg layers and its control line. Layers with one of the three genotypes at the NA locus were produced from 11 sires from the control line and 12 sires from the selected line. Two hatches produced 216 adult hens in Taiwan and 297 hens in France. Genetic parameters for laying traits were estimated in each environment and the ranking of sire breeding values was compared between environments. Laying performance was lower, and mortality was higher in Taiwan than in France. The line by environment interaction was highly significant for body weight at 16 weeks, clutch length and egg number, with or without Box-Cox transformation. The selected line was more sensitive to environmental change but in Taiwan it could maintain a higher egg number than the control line. Estimated heritability values in the selected line were higher in France than in Taiwan, but not for all the traits in the control line. The rank correlations between sire breeding values were low within the selected line and slightly higher in the control line. A few sire families showed a good ranking in both environments, suggesting that some families may adapt better to environmental change

Genetic architecture of common bunt resistance in winter wheat using genome-wide association study

Background: Common bunt (caused by Tilletia caries and T. foetida) has been considered as a major disease in wheat (Triticum aestivum) following rust (Puccinia spp.) in the Near East and is economically important in the Great Plains, USA. Despite the fact that it can be easily controlled using seed treatment with fungicides, fungicides often cannot or may not be used in organic and low-input fields. Planting common bunt resistant genotypes is an alternative. Results: To identify resistance genes for Nebraska common bunt race, the global set of differential lines were inoculated. Nine differential lines carrying nine different genes had 0% infected heads and seemed to be resistant to Nebraska race. To understand the genetic basis of the resistance in Nebraska winter wheat, a set of 330 genotypes were inoculated and evaluated under field conditions in two locations. Out of the 330 genotypes, 62 genotypes had different degrees of resistance. Moreover, plant height, chlorophyll content and days to heading were scored in both locations. Using genome-wide association study, 123 SNPs located on fourteen chromosomes were identified to be associated with the resistance. Different degrees of linkage disequilibrium was found among the significant SNPs and they explained 1.00 to 9.00% of the phenotypic variance, indicating the presence of many minor QTLs controlling the resistance. Conclusion: Based on the chromosomal location of some of the known genes, some SNPs may be associated with Bt1, Bt6, Bt11 and Bt12 resistance loci. The remaining significant SNPs may be novel alleles that were not reported previously. Common bunt resistance seems to be an independent trait as no correlation was found between a number of infected heads and chlorophyll content, days to heading or plant height