Identification of QTLs for resistance to leaf and stem rusts in bread wheat (Triticum aestivum L.) using a mapping population of ‘Pamyati Azieva × Paragon’

Leaf rust (LR) and stem rust (SR) are harmful fungal diseases of bread wheat (Triticum aestivum L.). The purpose of this study was to identify QTLs for resistance to LR and SR that are effective in two wheat-growing regions of Kazakhstan. To accomplish this task, a population of recombinant inbred lines (RILs) of ‘Pamyati Azieva × Paragon’ was grown in the northern and southeastern parts of Kazakhstan, phenotyped for LR/SR severities, and analyzed for key yield components. The study revealed a negative correlation between disease severity and plant productivity in both areas. The mapping population was genotyped using a 20,000 Illumina SNP array. A total of 4595 polymorphic SNP markers were further selected for linkage analysis after filtering based on missing data percentage and segregation distortion. Windows QTL Cartographer was applied to identify QTLs associated with LR and SR resistances in the RIL mapping population studied. Two QTLs for LR resistance and eight for SR resistance were found in the north, and the genetic positions of eight of them have matched the positions of the known Lr and Sr genes, while two QTLs for SR were novel. In the southeast, eight QTLs for LR and one for SR were identified in total. The study is an initial step of the genetic mapping of LR and SR resistance loci of bread wheat in Kazakhstan. Field trials in two areas of the country and the genotyping of the selected mapping population have allowed identification of key QTLs that will be effective in regional breeding projects for better bread wheat productivity

Friction between carbon fibre reinforced polymers: Experiments and modelling

Carbon fibre reinforced polymers (CFRP) are well-known for the excellent combination of mechanical and thermal properties with light weight. However, their tribological properties are still largely uncovered. In this work an experimental study of friction between two CFRP at weak normal load (inferior to 20 N) was performed. Two effects were scrutinuously studied during the experiments: fibre volume friction and fibre orientation. In addition to this experimental work, a modelling of a contact between two FRP was realized. It is supposed that the real area of contact consists of a multitude of microcontacts of three types: fibre-fibre, fibre-matrix and matrix-matrix. The experimental work has shown a small rise in friction coefficient with the change of fibre orientation of two composites from parallel to perpendicular relative to the sliding direction. In parallel, the proposed analytical model predicts a independence of this angle. Regarding the influence of the fibre volume fraction, Vf, the experiments reveal a decrease in friction coefficient of 50% with a change of Vf from 0% to 62%. This observation corresponds to the qualitative dependence depicted with the model. © 2012 EDP Sciences

Frottement des matériaux composites polymères à renfort fibre de carbone : expériences et modélisation

Les matériaux composites polymères renforcés avec des fibres de carbone (PRFC) sont connus pour l’excellente combinaison de leurs propriétés mécaniques et thermiques avec leur faible masse. Cependant, leurs propriétés tribologiques restent largement méconnues. Dans le cadre de ce travail, l’étude expérimentale du frottement entre deux PRFC composites sous faible charge normale (jusqu’à 20 N) a été réalisée. Deux effets ont été soigneusement étudiés pendant l’expérience : la fraction volumique et l’orientation des fibres. En complément de ce travail expérimental, une modélisation du contact entre deux PRFC a été réalisée. On suppose que l’aire réelle de contact est constituée d’une multitude de microcontacts de trois types : fibre-fibre, fibre-matrice et matrice-matrice. L’étude expérimentale a montré une légère augmentation de coefficient de frottement avec le changement d’orientation de fibre de deux composites de parallèle à perpendiculaire par rapport au sens de glissement, alors que le modèle analytique proposé prédit une indépendance de cet angle. Quant à l’influence de la fraction volumique de fibres, Vf, les essais soulignent une diminution de coefficient de frottement de moitié avec une augmentation de Vf de 0 % à 62 %, ce qui correspond à la dépendance qualitative trouvée dans le cadre du modèle