Population structure and genetic bottleneck in sweet cherry estimated with SSRs and the gametophytic self-incompatibility locus

<p>Abstract</p> <p>Background</p> <p>Domestication and breeding involve the selection of particular phenotypes, limiting the genomic diversity of the population and creating a bottleneck. These effects can be precisely estimated when the location of domestication is established. Few analyses have focused on understanding the genetic consequences of domestication and breeding in fruit trees. In this study, we aimed to analyse genetic structure and changes in the diversity in sweet cherry <it>Prunus avium </it>L.</p> <p>Results</p> <p>Three subgroups were detected in sweet cherry, with one group of landraces genetically very close to the analysed wild cherry population. A limited number of SSR markers displayed deviations from the frequencies expected under neutrality. After the removal of these markers from the analysis, a very limited bottleneck was detected between wild cherries and sweet cherry landraces, with a much more pronounced bottleneck between sweet cherry landraces and modern sweet cherry varieties. The loss of diversity between wild cherries and sweet cherry landraces at the <it>S</it>-locus was more significant than that for microsatellites. Particularly high levels of differentiation were observed for some <it>S</it>-alleles.</p> <p>Conclusions</p> <p>Several domestication events may have happened in sweet cherry or/and intense gene flow from local wild cherry was probably maintained along the evolutionary history of the species. A marked bottleneck due to breeding was detected, with all markers, in the modern sweet cherry gene pool. The microsatellites did not detect the bottleneck due to domestication in the analysed sample. The vegetative propagation specific to some fruit trees may account for the differences in diversity observed at the <it>S</it>-locus. Our study provides insights into domestication events of cherry, however, requires confirmation on a larger sampling scheme for both sweet cherry landraces and wild cherry.</p

Towards map-based cloning: fine mapping of the D gene involved in peach fruit acidity

National audienc

Fine mapping of the D gene controlling fruit acidity in peach and screening of a new BAC library

International audienc

From the fine mapping to the cloning of the D gene involved in quantitative traits in peach fruit quality

International audienc

Études biomoléculaires et tests en verger : les compatibilités polliniques des variétés de cerisier

National audienc

Le cerisier a trouvé ses compatibilités polliniques

National audienc

Compatibilités polliniques chez le cerisier : la biologie moléculaire au service du verger

National audienc

Embolism resistance of conifer roots can be accurately measured with the flow-centrifuge method

Resistance to embolism of conifer branches has commonly been studied with the flow-centrifuge technique (Cavitron) to carry out routine measurements. The aim of this study was to test the accuracy of the Cavitron for measurements on conifer roots. Based on earlier findings, it was suggested that the application of the flow-centrifuge technique to roots may not be free from artefacts due to potential torus aspiration when the pressure gradient between the sample ends is high. Here, three different protocols were used to obtain vulnerability curves in Pinus pinaster and Pseudotsuga menziesii roots: no water pressure gradient, and low and high water pressure gradient. In addition water extraction curves were obtained to only estimate the water released from conduits by embolism. Water extraction curves showed no water release caused by embolism before -1.3 and -2.5 MPa for P. pinaster and P. menziesii, respectively. The results illustrated discrepancies between these protocols: roots measured with the high and low pressure gradient protocols appeared erroneously more vulnerable to embolism than roots measured with no pressure gradient. In addition, pit anatomical observations of roots showed non-punctured tori and a high flexibility of the margo, which may increase the risk of torus aspiration. All together these results suggest that the early loss of hydraulic conductivity observed for the low and high pressure gradient protocols was not due to embolism but rather to a torus aspiration artefact when the pressure gradient is too high. We conclude that the no pressure gradient protocol provides a suitable method and that high vulnerability to embolism reported in previous studies for conifer roots should be interpreted with caution in the light of our findings

A sweet cherry (Prunus avium L.) linkage map and its comparison to other prunus species

International audienceThe sweet cherry (Prunus avium) is one of the most popular temperate fruit crops. However, compared with others, such as the apple and peach, progress in breeding for improvement of sweet cherry has been slow. The long generation time and the large size of cherry trees severely limit the classical breeding method. Consequently, the integration of molecular markers in breeding programmes should be a powerful tool. Inheritance and linkage studies were conducted with microsatellite markers in an F, progeny including 133 individuals of a cross between 'Regina' and 'Lapins', which were chosen as parents for their distinct agronomic characters and especially because they allowed the study of resistance to fruit cracking, which is a limiting factor in sweet cherry production. 'Regina' is relatively resistant, and 'Lapins' is susceptible to fruit cracking. 'Lapins' is self-compatible, whereas 'Regina' is self-incompatible; moreover, they differ for several other characters: blooming and maturity dates, peduncle length, fruit colour, weight, firmness, titratable acidity and refractive index. These characters were measured at commercial and physiological maturity. For mapping, 337 Prunus microsatellites were tested for polymorphism: 249 (74%) give amplification, 76 were heterozygous in 'Regina', 63 in 'Lapins' and 44 in both parents. sMaps were constructed for each parent. The comparison of these cherry maps with other Prunus maps gives additional evidence for the high level of synteny within the Prunus genus. The two sweet cherry maps will be used for detection of QTLs involved in fruit quality

Intraspecific variation in embolism resistance and stem anatomy across four sunflower (Helianthus annuus L.) accessions

Drought-induced xylem embolism is a key process closely related to plant mortality during extreme drought events. However, this process has been poorly investigated in crop species to date, despite the observed decline of crop productivity under extreme drought conditions. Interspecific variation in hydraulic traits has frequently been reported, but less is known about intraspecific variation in crops. We assessed the intraspecific variability of embolism resistance in four sunflower (Helianthus annuus L.) accessions grown in well-watered conditions. Vulnerability to embolism was determined by the in situ flow-centrifuge method (cavitron), and possible trade-offs between xylem safety, xylem efficiency and growth were assessed. The relationship between stem anatomy and hydraulic traits was also investigated. Mean P50 was -3 MPa, but significant variation was observed between accessions, with values ranging between -2.67 and -3.22 MPa. Embolism resistance was negatively related to growth and positively related to xylem-specific hydraulic conductivity. There is, therefore, a trade-off between hydraulic safety and growth but not between hydraulic safety and efficiency. Finally, we found that a few anatomical traits, such as vessel density and the area of the vessel lumen relative to that of the secondary xylem, were related to embolism resistance, whereas stem tissue lignification was not. Further investigations are now required to investigate the link between the observed variability of embolism resistance and yield, to facilitate the identification of breeding strategies to improve yields in an increasingly arid world