Evaluation of alfalfa resistance to the pea aphid, Acyrtosiphon pisum [Homoptera : Aphididae] – Methodological aspects to improve a standardized speedling test

Cette étude concerne des éléments de standardisation pour mettre en oeuvre un test d'évaluation de la résistance variétale de la luzerne (Medicago sativa) au puceron du pois (Acyrthosiphon pisum). Réalisé en conditions contrôlées, il évalue la résistance de plantules à l'infestation aphidienne. Pour réaliser cette dernière, il est nécessaire de produire les pucerons sur des plantes de luzerne plutôt que sur des plantes de féverole, leur action sur la luzerne étant alors moindre. La disposition d'un seul cultivar (condition de «non choix») donne les mêmes résultats que la disposition dans la même unité de plusieurs variétés (conditions de choix) et est plus facile à gérer. L'unité élémentaire, constituée de 54 plantules, est infestée avec 360 mg de pucerons lorsque les cotylédons s'ouvrent, ce que l'on renouvelle après 5 jours. Cette dose conduit à des résultats optimums par rapport à des infestations réalisées dans les mêmes conditions avec 180 ou 540 mg. L'infestation est arrêtée lorsque 60 % des plantules d'un cultivar sensible dépérissent ou meurent. Dans ces conditions, nous avons calculé le nombre de répétitions nécessaires. Six unités élémentaires permettent alors d'apprécier une différence de mortalité entre cultivars de 20 %.This study proposes a guide for the design of experiments to test alfalfa (Medicago sativa) for resistance to pea aphid infestation (Acyrthosiphon pisum). This test was conducted in controlled conditions on alfalfa seedlings. For the infestation, aphid population maintained on alfalfa was found to be more efficient than an aphid population reared on broad bean. When comparing alfalfa cultivars, a non-choice test gave the same results as a choice test, that was more difficult to perform. When infesting a unit of 54 seedlings at the cotyledon stage on the 1st and 5th day of the experiment, 360 mg compared with 180 mg and 540 mg aphids, led to the best compromise between levels of infestation and aphid stock culture availability. Infestation was stopped when more than 60% of susceptible cultivar seedlings were wilted or dead. Under these conditions, we calculated the number of replicates necessary to obtain a fixed level of difference. Six units per cultivar would distinguish between cultivars differing from 20% in their seedling mortality

Further Support to the Uncoupling-to-Survive Theory: The Genetic Variation of Human UCP Genes Is Associated with Longevity

In humans Uncoupling Proteins (UCPs) are a group of five mitochondrial inner membrane transporters with variable tissue expression, which seem to function as regulators of energy homeostasis and antioxidants. In particular, these proteins uncouple respiration from ATP production, allowing stored energy to be released as heat. Data from experimental models have previously suggested that UCPs may play an important role on aging rate and lifespan. We analyzed the genetic variability of human UCPs in cohorts of subjects ranging between 64 and 105 years of age (for a total of 598 subjects), to determine whether specific UCP variability affects human longevity. Indeed, we found that the genetic variability of UCP2, UCP3 and UCP4 do affect the individual's chances of surviving up to a very old age. This confirms the importance of energy storage, energy use and modulation of ROS production in the aging process. In addition, given the different localization of these UCPs (UCP2 is expressed in various tissues including brain, hearth and adipose tissue, while UCP3 is expressed in muscles and Brown Adipose Tissue and UCP4 is expressed in neuronal cells), our results may suggest that the uncoupling process plays an important role in modulating aging especially in muscular and nervous tissues, which are indeed very responsive to metabolic alterations and are very important in estimating health status and survival in the elderly

Climate change impact and adaptation for wheat protein

Wheat grain protein concentration is an important determinant of wheat quality for human nutrition that is often overlooked in efforts to improve crop production. We tested and applied a 32‐multi‐model ensemble to simulate global wheat yield and quality in a changing climate. Potential benefits of elevated atmospheric CO2 concentration by 2050 on global wheat grain and protein yield are likely to be negated by impacts from rising temperature and changes in rainfall, but with considerable disparities between regions. Grain and protein yields are expected to be lower and more variable in most low‐rainfall regions, with nitrogen availability limiting growth stimulus from elevated CO2. Introducing genotypes adapted to warmer temperatures (and also considering changes in CO2 and rainfall) could boost global wheat yield by 7% and protein yield by 2%, but grain protein concentration would be reduced by −1.1 percentage points, representing a relative change of −8.6%. Climate change adaptations that benefit grain yield are not always positive for grain quality, putting additional pressure on global wheat production

Water Deficit-Induced Changes in Concentrations in Proline and Some Other Amino Acids in the Phloem Sap of Alfalfa.

Changes in amino acid composition of alfalfa (Medicago sativa L.) phloem sap were studies in response to a water deficit. Sap was collected by stylectomy. As the leaf water potential ([psi]) decreased from -0.4 to -2.0 MPa, there was significant increase of the total amino acid concentration, due to that of some amino acids: proline, valine, isoleucine, leucine, glutamic acid, aspartic acid, and threonine. Asparagine concentration, which is the main amino acid assayed in the phloem sap of alfalfa (it accounts for 70% of the total content), did not vary with the plant water status. The other amino acid concentrations remained stable as [psi] varied; in particular, [gamma]-amino butyric acid concentration remained unchanged, whereas it varied in response to wounding. The more striking change in the sieve tubes was the accumulation of proline, which was observed below a [psi] threshold value of about -0.9 MPa (concentration x60 for a decrease of [psi] from -0.9 to -2.0 MPa). The role of such changes in phloem sap amino acid concentration in osmotic adjustment of growing tissues is discussed

Grain de resistance variétale de la luzerne au puceron du pois, estimé par deux critères lors de générations de sélection

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La recherche de QTL : objectifs et pratiques ; pour une approche interdisciplinaire (génétique, echophysiologie, zoologie) des interactions genotype-milieu biotique et abiotique chez les fourragères pérennes

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