Search

Dynamic management has been proposed as a complementary strategy to gene banks for the conservation of genetic resources. The evolution of frequencies of genes for specific resistance towards powdery mildew (caused by Blumeria graminis f. sp. tritici) in populations of a French network for dynamic management of bread wheat genetic resources was investigated after 10 years of multiplication without human selection. The objective was to determine whether specific resistance gene diversity was maintained in the populations and whether any changes could be attributed to selection due to pathogen pressure. Seven populations, originating from four of the network sites, were characterized and compared to the initial population for six specific resistance gene frequencies detected by nine Blumeria graminis f. sp. tritici isolates. Diversity decreased at the population level, but because of a strong differentiation between the populations, this diversity was maintained at the network level. The comparison of Fst parameters estimated on neutral markers (RFLP) and on resistance gene data revealed that in two of the populations specific resistance genes had been selected by pathogen pressure, whereas evolution in two other populations seemed to be the result of genetic drift. For the three last populations, conclusions were less clear, as one had probably experienced a strong bottleneck and the other two presented intermediate Fst values. A dynamic management network with sites contrasted for pathogen pressure, allowing genetic drift in some populations and selection in others, appeared, at least on the short term, to be a good tool for maintaining the diversity of genes for specific resistance to powdery mildew.

The evolution of adult plant resistance towards powdery mildew (caused by Blumeria graminis f. sp. tritici) was investigated in 11 wheat populations cultivated for 10 years in a French network for dynamic management (DM) of wheat genetic resources. The aims of the study were to compare the evolution of resistance in sites submitted to different powdery mildew pressure and to investigate the implication of specific resistance gene action in adult plant resistance. For this, 7 of the 11 populations were characterized for their composition of specific resistance genes (results presented in a former paper). Even though no population differed significantly from the initial PA0 pool for mean adult plant resistance, divergence appeared among the final populations. The populations with the highest adult plant resistance level originated from sites where powdery mildew pressure is known to be high (Vervins, Le Rheu), whereas populations with the lowest adult plant resistance corresponded to areas with no, or very low, powdery mildew pressure (Toulouse, Montreuil-Bellay). A residual effect of defeated specific resistance genes was hypothesized, as lines accumulating at least two specific resistance genes appeared more resistant. Additional quantitative resistance seemed to be involved in adult plant resistance. DM lines appeared then as an interesting source of variability for resistance towards powdery mildew. Moreover, as these lines had been grown in mixed populations they may be appropriate as components of a composite cultivar.

Patients undergoing congenital heart surgery are at risk of morbidity and mortality. The reasons underlying this risk are complex. To identify opportunities to reduce adverse sequelae, the cardiovascular perfusion community was invited to amend existing perfusion-related fields as well as add new ones to the current version of the Society of Thoracic Surgeons Congenital Heart Surgery Database (STS-CHSD). The International Consortium for Evidence-Based Perfusion (ICEBP) was invited by the STS-CHSD Task Force to identify and resolve ambiguities related to definitions among the 3 current perfusion-related fields as well as to propose new variables (and definitions) for inclusion in the 2010 update of the STS-CHSD. The ICEBP used teleconferences, wiki-based communication software, and e-mail to discuss current definitions and create new fields with definitions. The ICEBP created modified definitions to existing fields related to cardiovascular perfusion and also developed and defined new fields that focus on (1) techniques of circulatory arrest and cerebral perfusion, (2) strategies of myocardial protection, and (3) techniques to minimize hemodilution and allogeneic blood transfusions. Three fields in the STS-CHSD related to perfusion were redefined, and 23 new variables and definitions were selected for inclusion. Identifying and defining fields specific to the practice of perfusion are requisite for assessing and subsequently improving the care provided to patients undergoing congenital heart surgery. The article describes the methods and justification for adjudicating extant and new perfusion-related fields added to the 2010 update of the STS-CHSD.

Background: Perioperative bleeding is common in pediatric cardiac surgery patients. Traditional laboratory tests do not adequately characterize coagulation derangements in patients with bleeding. We sought to establish preoperative thromboelastography parameters in children prior to cardiopulmonary bypass, to compare thromboelastography assessment with standard coagulation parameters postoperatively, and to assess thromboelastography in children with significant hemorrhage. Methods: Sixty patients requiring cardiopulmonary bypass were enrolled in a prospective observational study of perioperative thromboelastography. Thromboelastography measures were obtained preoperatively, intraoperatively after protamine administration, upon admit to the intensive care unit, and when patients were treated for bleeding. Thromboelastography measures were not used for clinical care. Postoperative thromboelastography measurements were compared with the standard coagulation parameters. Intraoperative thromboelastography, postoperative thromboelastography, and clinical outcomes were compared among patients who did and did not have significant postoperative bleeding. Results: Preoperative thromboelastography parameters were similar to other published normal values for pediatric patients. Transfusion recommendations based on thromboelastography measurements were significantly different from those based on the standard coagulation testing. Thromboelastography measures after initial protamine administration were significantly different in patients with postoperative bleeding. This difference was not present upon arrival to the intensive care unit. Patients with significant bleeding tended to cease bleeding when clinical interventions were in agreement with recommendations based on thromboelastography. Conclusions: Pediatric patients with significant postoperative bleeding after surgery are more likely to have abnormal thromboelastography early after cessation of cardiopulmonary bypass. Thromboelastography illustrates derangements in the coagulation system and may aid in the treatment of postoperative bleeding.

The inheritance of seed coat color, pericarp color, polyphenoloxidase activity and bristle, glume, collar, and leaf-base anthocyanic colorations was investigated using intra- and interspecific crosses between Setaria italica and S. viridis. The results were compared to inheritance results obtained by previous authors. In most cases, the inheritance is simple (one or two loci) and data from different crosses (intra- and interspecific) and from different authors can be compared. Two sets of two characters were found to share common loci: the polyphenoloxidase locus is one of the loci responsible for seed coat color, and bristle and glume color are determined by the same two loci. The evolutionary significance of these results is discussed.

Temporal evolution of genetic variability in a Dynamic Management programme of wheat populations was assessed for fitness-related traits and for 29 RFLP markers. Populations of the 1st, 5th and 10th generations were studied. Genetic correlation between plant height (PH) and kernel number (KN) or kernel weight (KW) per plant was high and positive in each population, due to an advantage for the taller plants in intergenotypic competition conditions. This led to a linear increase in PH over generations. On the other hand, KN and KW linearly decreased over generations certainly due to re-allocation of reproductive resources to vegetative functions in the taller plants. On the basis of temporal variation of allelic frequencies of RFLP markers, very low effective sizes (Ne) were estimated: 216 between the 1st and 5th generation, and 157 between the 5th and 10th. These values, much lower than expected from census sizes (= 2650) demonstrated that selection strongly influenced the evolution of neutral loci either by direct hitch-hiking effects and/or by increasing variance of progeny size. The non-significantly different Ne estimates for both periods of time suggested that selection remained constant over the 10 generations. This result is consistent with the continuous evolution of the quantitative traits. A great heterogeneity of temporal variations was observed among loci, showing the heterogeneity of selective pressures over the genome. Detection of selected loci using genetic markers is discussed.

Multi-environmental experimentation made it possible to compare 311 hybrids and their 59 parental lines for five characters: yield, two yield components (number of grains per m2 and 1000-grain weight), height and date of heading. At all three sites, average high-parent heterosis exceeded 6%, and our results confirm that hybrids in general head as early as the earlier parent does and are as high as the taller parent. For the five characters studied ecovalences were significantly lower in the F1 than in the parents, indicating a higher level of homeostasis for hybrids. The experimental model, based on a ”top-cross” design comprised of 55 lines used as females and four testers, made it possible to implement different hybrid-value prediction models. For yield, by far the most important character to predict, the predictor based on the general combining ability and the per se value of the parents, appears to be the most interesting. The prediction remains, however, imperfect as specific combining ability (SCA) has a strong impact for this character. Attempting to take account of SCA in the prediction, by using a multiplicative model for ”male×female” interaction modelling, did not prove convincing.

Dynamic management of genetic resources aims to conserve genetic variability between different populations evolving in contrasting environments. It is thus of importance to determine whether differences appearing between populations are stochastic or if they come about from adaptation. Two-dimensional electrophoresis (2DE) was used to study genetic differentiation of 11 wheat populations evolving since 1984 in a multi-site network covering the major cultivation area of wheat in France. Gels were scanned and protein-spot intensities were measured through image analysis. As it was not possible to assay each individual, populations were characterized using pooled extracts from several plants. In the first step, two parents among the 16 parental lines involved in the initial wheat composite-cross population were exhaustively studied to identify a set of polymorphic spots against which the entire set of evolved populations could be compared. This analysis confirmed the efficiency of gel image-processing to determine the composition of pooled extracts. Of the 48 spots used to investigate population differentiation, 15 showed significant differences at the P

A programme of dynamic conservation of genetic resources has been conducted on winter wheat in France since 1984. One allogamous and 2 preferential selfing populations, with a large genetic base, made up the initial gene pools. Seed samples of these pools were distributed throughout a multi-site experimental network. The populations obtained were multiplied each year in each site. Populations developed significantly after 8 years of multiplication: plant height had increased, the proportion of viable pollen grains had increased in male-fertile plants of allogamous populations and a north-south gradient for precocity was observed for autogamous populations. Resistance to powdery mildew had developed in local populations, both for adult-plant resistance and the frequency of specific resistance genes to Erysiphe graminis f sp tritici. The differentiation depended on the gene pool of the host populations. Virulence frequencies of the parasite populations varied according to the site and the year. There was no clear relationship between virulence frequencies and resistance gene frequencies. The proportion of plants without specific resistance genes seems to correlate with adult-plant susceptibility in local autogamous populations. Most of the variability was maintained through propagation under various natural selection forces., Un programme de gestion dynamique des ressources génétiques est développé en France depuis 1984 sur le blé tendre. Deux populations préférentiellement autogames et une population conduite en allogamie, toutes 3 à large base génétique, constituaient les pools génétiques de départ. Des échantillons de grains de ces pools ont été distribués dans un réseau multilocal. Les populations ainsi obtenues sont multipliées année après année dans chaque lieu du réseau. Après 8 ans de multiplication, les populations ont nettement évolué. On constate une augmentation de la taille des plantes adultes, une meilleure production de grains de pollen viable chez les plantes mâles fertiles des populations allogames et la mise en place d’un gradient de précocité Nord-Sud pour les populations autogames. La résistance à l’oïdium a évolué dans les populations, à la fois pour la résistance au stade adulte et pour les fréquences de gènes de résistance spécifique vis-à-vis d’Erysiphe graminis f sp tritici. La différenciation dépend du pool génétique auquel appartiennent les populations hôtes. Les fréquences de virulence des populations du parasite varient selon les sites et les années. Aucune relation claire n’a été mise en évidence entre les fréquences de virulences du parasite et celles des gènes de résistance spécifique de l’hôte. La proportion de plantes sans résistance spécifique semble corrélée à la sensibilité au stade adulte dans les populations autogames. La diversité des milieux formant le réseau a globalement permis le maintien de la variabilité.

Outcrossing rates within the wild green foxtail, Setaria viridis, and the cultivated foxtail millet, S. italica, are very low. However, spontaneous interspecific hybridizations in the experimental garden occurred in both directions at rates ranging from 0.002% to 0.6% according to plant density and distance between parents. Offtypes found in farmers' fields where foxtail millet is cultivated were shown to have originated from such interspecific crosses. Differences in the EcoR1 patterns of chloroplast DNA between cultivated and wild plants indicated that reciprocal crosses do occur in the field. These findings indicate that even a largely selfing cultivated species may exchange genetic information with wild relatives at rates that may cause problems if transgenic cultivars are released.