Cryopreservation of cell suspensions and embryogenic calluses of Citrus using a simplified freezing process

Une méthode de congélation simplifiée a été expérimentée avec une suspension cellulaire de mandarine commune et des cals embryogènes de six variétés de #citrus$. Son efficacité est comparable à celle du protocole de congélation standard développé précédemment pour ces matériels, qui nécessitait l'emploi d'un congélateur programmable. La suspension cellulaire peut être congelée sans modifier les conditions originales (0,15 M saccharose +5 % DMSO). Les cals embryogènes de 5 variétés sur les 6 expérimentées résistent à la congélation avec le procédé simplifié. Les résultats optimaux sont obtenus en augmentant la concentration en DMSO à 10 ou 15%. (Résumé d'auteur

First results of the ROSEBUD Dark Matter experiment

Rare Objects SEarch with Bolometers UndergrounD) is an experiment which attempts to detect low mass Weak Interacting Massive Particles (WIMPs) through their elastic scattering off Al and O nuclei. It consists of three small sapphire bolometers (of a total mass of 100 g) with NTD-Ge sensors in a dilution refrigerator operating at 20 mK in the Canfranc Underground Laboratory. We report in this paper the results of several runs (of about 10 days each) with successively improved energy thresholds, and the progressive background reduction obtained by improvement of the radiopurity of the components and subsequent modifications in the experimental assembly, including the addition of old lead shields. Mid-term plans and perspectives of the experiment are also presented.Comment: 14 pages, 8 figures, submitted to Astroparticle Physic

Cytological and molecular characterization of three gametoclones of Citrus clementina

Abstract Background Three gametoclonal plants of Citrus clementina Hort. ex Tan., cv. Nules, designated ESP, FRA, and ITA (derived from three labs in Spain, France, and Italy, respectively), were selected for cytological and molecular characterization in order to elucidate genomic rearrangements provoked by haploidization. The study included comparisons of their ploidy, homozygosity, genome integrity, and gene dosage, using chromosome counting, flow cytometry, SSR marker genotyping, and array-Comparative Genomic Hybridization (arrayCGH). Results Chromosome counting and flow cytometry revealed that ESP and FRA were haploid, but ITA was tri-haploid. Homozygous patterns, represented by a single peak (allele), were observed among the three plants at almost all SSR loci distributed across the entire diploid donor genome. Those few loci with extra peaks visualized as output from automated sequencing runs, generally low or ambiguous, might result from amplicons of paralogous members at the locus, non-specific sites, or unexpected recombinant alleles. No new alleles were found, suggesting the genomes remained stable and intact during gametogenesis and regeneration. The integrity of the haploid genome also was supported by array-CGH studies, in which genomic profiles were comparable to the diploid control. Conclusions The presence of few gene hybridization abnormalities, corroborated by gene dosage measurements, were hypothetically due to the segregation of hemizygous alleles and minor genomic rearrangements occurring during the haploidization procedure. In conclusion, these plants that are valuable genetic and breeding materials contain completely homozygous and essentially intact genomes

Obtention d'embryons et de cals embryogènes haploides de clémentiniers par gynogénèse induite

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Somatic hybridisation in citrus : some new hubrid and alloplasmic plants

International audienc

Rootstock breeding by somatic hybridisation for the mediterranean citrus industry

The predominance of sour orange rootstock for citrus in the Mediterranean area is currently threatened by the spread of citrus tristeza virus (CTV). As a result, the search for alternative rootstocks resistant to CTV and able to withstand other constraints, such as drought, alkalinity, salinity, Phytophthora and nematode problems, is now considered an urgent priority. Progress in genetic improvement of citrus rootstock by conventional sexual breeding is difficult, mainly because of the reproductive biology and heterozygosity of genitors. These induce important segregations of characters in progeny and a low probability of obtaining recombinant hybrids that combine all the desirable genes and traits of the two parents. In this context, the creation of somatic hybrids is very promising. Indeed, it allows for the accumulation of all the dominant genes of both parents for tolerance to biotic and abiotic factors, irrespective of their level of heterozygosity. This strategy has now been mastered by CIRAD in France with a view to launching a Mediterranean citrus rootstock challenge. Protoplast electrofusions were used for 11 interspecific and intergeneric combinations. Regenerated embryos and plants are studied by flow cytometry and molecular markers in order to select allotetraploid hybrids. The somatic hybrids then undergo an accelerated propagation step, which uses softwood cuttings for further multilocal evaluation of tolerance to biotic and abiotic factors and agronomic rootstock trials

Cryopreservation of cell suspensions and embryogenic calluses of Citrus using a simplified freezing process

Une méthode de congélation simplifiée a été expérimentée avec une suspension cellulaire de mandarine commune et des cals embryogènes de six variétés de #citrus$. Son efficacité est comparable à celle du protocole de congélation standard développé précédemment pour ces matériels, qui nécessitait l'emploi d'un congélateur programmable. La suspension cellulaire peut être congelée sans modifier les conditions originales (0,15 M saccharose +5 % DMSO). Les cals embryogènes de 5 variétés sur les 6 expérimentées résistent à la congélation avec le procédé simplifié. Les résultats optimaux sont obtenus en augmentant la concentration en DMSO à 10 ou 15%. (Résumé d'auteur

Somatic hybridisation in citrus : some new hubrid and alloplasmic plants

International audienc

Obtention d'embryons et de cals embryogènes haploides de clémentiniers par gynogénèse induite

National audienc

In vitro rescue and selection of spontaneous triploids by flow cytometry for easy peeler citrus breeding

International audienc