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International audience; The US National Fragaria collection at the United States Department of Agriculture (USDA), Agricultural Research Service (ARS), National Clonal Germplasm Repository (NCGR) is dynamic through the discovery and collection of new acquisitions and new characteristics that delineate existing species. Previous research using standard Fragaria chloroplast genome regions exhibited limited variation and was unsuccessful at distinguishing between species. The objective of this study was to examine universal chloroplast simple sequence repeats SSRs (cpSSRs) to evaluate diversity in Fragaria species. Four universal cpSSRs (ccmp2, ccmp5, ccmp6, and ccmp7) generated 28 Fragaria haplotypes in ninety four accessions representing 20 Fragaria taxa. Taxa-specific haplotypes were identified for F. nipponica, F. orientalis, F. iinumae and F. nilgerrensis. An octoploid-specific haplotype was observed in cultivated F. ×ananassa, F. chiloensis and F. virginiana supporting their close relationship. Genetic diversity using only four universal SSR markers was moderate (0.54, on average) despite the observed homoplasy. Species-specific dehydroascorbate reductase (DHAR) and granule-bound starch synthase (GBSSI-2) gene sequences were also evaluated to identify diploid strawberry species. Marker results and future needs for additional Fragaria-specific primers that may more accurately identify the chloroplast diversity in Fragaria will be discussed.

International audience; Cryopreservation is the only alternative, safe and cost-effective method for long-term storage of plant genetic resources, particularly for stone fruits (Prunus spp.). In this study, an efficient cryopreservation protocol was developed for sour cherry (Prunus cerasus L.). In vitro shoot tips of two varieties (Montmorency and Schattenmorelle) were successfully cryopreserved using the vitrification technique. Our study showed the possibility of replacing the 3-week cold hardening treatment of mother-plants with preculture of apices on medium enriched with sucrose and/or glycerol. The highest recovery percentages after liquid nitrogen exposure were obtained after a cold hardening treatment followed by a 3-day preculrure on 0.8 M sucrose medium or by replacing cold hardening with a 7-day preculture on the following media: 0.4 M glycerol or sucrose, 0.4 M sucrose + 0.4 M glycerol or 0.8 M glycerol. Under these conditions, recovery after cryopreservation ranged between 41 and 63%, These results complement the range of Prunus species successfully cryopreserved using in vitro explants. Our protocol, which is simplified in comparison with the original one, since cold hardening of mother-plants in a cold chamber is replaced by pretreatment of apices on medium with high sugar concentration, may facilitate the application of vitrification for cryopreservation of additional Prunus species

The present study investigates the genetic determinism of flowering and maturity dates, two traits highly affected by global climate change. Flowering and maturity dates were evaluated on five progenies from three Prunus species, peach, apricot and sweet cherry, during 3–8 years. Quantitative trait locus (QTL) detection was performed separately for each year and also by integrating data from all years together. High heritability estimates were obtained for flowering and maturity dates. Several QTLs for flowering and maturity dates were highly stable, detected each year of evaluation, suggesting that they were not affected by climatic variations. For flowering date, major QTLs were detected on linkage groups (LG) 4 for apricot and sweet cherry and on LG6 for peach. QTLs were identified on LG2, LG3, LG4 and LG7 for the three species. For maturity date, a major QTL was detected on LG4 in the three species. Using the peach genome sequence data, candidate genes underlying the major QTLs on LG4 and LG6 were investigated and key genes were identified. Our results provide a basis for the identification of genes involved in flowering and maturity dates that could be used to develop cultivar ideotypes adapted to future climatic conditions., This work was partially supported by the ISAFRUIT Project funded by the European Commission—Food Quality and Safety of the 6th Framework Program of RTD (No. FP6-FOOD-CT-2006-016279).

The circadian clocks that drive daily rhythms in animals are tightly coupled among the cells of some tissues. The coupling profoundly affects cellular rhythmicity and is central to contemporary understanding of circadian physiology and behavior. In contrast, studies of the clock in plant cells have largely ignored intercellular coupling, which is reported to be very weak or absent. We used luciferase reporter gene imaging to monitor circadian rhythms in leaves of Arabidopsis thaliana plants, achieving resolution close to the cellular level. Leaves grown without environmental cycles for up to 3 wk reproducibly showed spatiotemporal waves of gene expression consistent with intercellular coupling, using several reporter genes. Within individual leaves, different regions differed in phase by up to 17 h. A broad range of patterns was observed among leaves, rather than a common spatial distribution of circadian properties. Leaves exposed to light–dark cycles always had fully synchronized rhythms, which could desynchronize rapidly. After 4 d in constant light, some leaves were as desynchronized as leaves grown without any rhythmic input. Applying light–dark cycles to such a leaf resulted in full synchronization within 2–4 d. Thus, the rhythms of all cells were coupled to external light–dark cycles far more strongly than the cellular clocks were coupled to each other. Spontaneous desynchronization under constant conditions was limited, consistent with weak intercellular coupling among heterogeneous clocks. Both the weakness of coupling and the heterogeneity among cells are relevant to interpret molecular studies and to understand the physiological functions of the plant circadian clock.

International audience; A basic knowledge on linkage disequilibrium (LD) is necessary in order to determine resolution of association studies. We investigated the extent and patterns of LD in a self-incompatible species ( Prunus avium L.), in 3 groups (wild cherry, sweet cherry landraces and sweet cherry modern varieties), using a set of 35 microsatellite markers and the gametophytic self-incompatibility locus. Since population structure might create spurious LD, we thus used the information provided by a structure analysis published in a previous study to perform the LD analysis. In the current study, we detected a greater LD extent in sweet cherry than in wild cherry, which is plausibly due to the bottleneck associated with domestication and breeding. Higher LD values in sweet cherry sub-groups may be explained by smaller sample sizes. We also showed that the remaining structure in the groups of sweet cherry, in particular landraces, is responsible for a part of the LD extent. Intra-group relatedness may also account for extensive LD in two sub-groups. These results demonstrate, if ever necessary, the importance of controlling the genetic structure and relatedness when estimating LD. Moreover, LD decays very rapidly with genetic linkage distance in both wild and sweet cherries, which seems promising for future association studies.

The Rosaceae Conserved Orthologous Set (RosCOS) provides a gene-based genome-wide set of markers that have been used in comparative analyses of peach (Prunus persica), apple (Malus × domestica), and strawberry (Fragaria spp.). In order to extend the use of these RosCOS to sweet cherry (Prunus avium L.), we identified markers that are polymorphic in breeding germplasm. Ninety-five percent (595/627) of previously designed RosCOS primer pairs amplified a product in six sweet cherry cultivars predicted to represent the range of genetic diversity in breeding germplasm. A total of 45% (282/627) RosCOS were polymorphic among the six cultivars, and allele number ranged from 2 to 6, with a genome-wide mean of 2.35. A subset of 92 genome-wide single nucleotide polymorphisms (SNPs) corresponding to 76 RosCOS was analyzed in 36 founder accessions and progeny. The expected and observed heterozygosity suggested that 83% of the RosCOS were in Hardy–Weinberg equilibrium, implying that most RosCOS behave as neutral markers. Principal coordinate analysis (PCO) identified one wild accession and two Spanish landraces that clustered differently from the other accessions. The relatively high number of unique alleles found in the three differentially clustered selections suggested that their use as parents has potential to increase the genetic diversity in future US-bred cultivars. Of the 92 RosCOS SNPs, 81 SNPs that represented 68 genome-wide RosCOS segregated in four mapping populations. These RosCOS were mapped in four F1 populations, thereby greatly improving the genetic linkage map of sweet cherry.

L'article original est publié par The American Society of Plant Biologists Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; International audience; Root-knot nematode (RKN) Meloidogyne species are major polyphagous pests of most crops worldwide, and cultivars with durable resistance are urgently needed because of nematicide bans. The Ma gene from the Myrobalan plum (Prunus cerasifera) confers complete-spectrum, heat-stable, and high-level resistance to RKN, which is remarkable in comparison with the Mi-1 gene from tomato (Solanum lycopersicum), the sole RKN resistance gene cloned. We report here the positional cloning and the functional validation of the Ma locus present at the heterozygous state in the P.2175 accession. High-resolution mapping totaling over 3,000 segregants reduced the Ma locus interval to a 32-kb cluster of three Toll/Interleukin1 Receptor-Nucleotide Binding Site-Leucine-Rich Repeat (LRR) genes (TNL1–TNL3), including a pseudogene (TNL2) and a truncated gene (TNL3). The sole complete gene in this interval (TNL1) was validated as Ma, as it conferred the same complete-spectrum and high-level resistance (as in P.2175) using its genomic sequence and native promoter region in Agrobacterium rhizogenes-transformed hairy roots and composite plants. The full-length cDNA (2,048 amino acids) of Ma is the longest of all Resistance genes cloned to date. Its TNL structure is completed by a huge post-LRR (PL) sequence (1,088 amino acids) comprising five repeated carboxyl-terminal PL exons with two conserved motifs. The amino-terminal region (213 amino acids) of the LRR exon is conserved between alleles and contrasts with the high interallelic polymorphisms of its distal region (111 amino acids) and of PL domains. The Ma gene highlights the importance of these uncharacterized PL domains, which may be involved in pathogen recognition through the decoy hypothesis or in nuclear signaling.

International audience; This is the first known large-scale molecular study of simple sequence repeats (SSR) loci based on samples from grafted trees found in the Iberian Peninsula and Canary Islands and hybrids. Interspecific hybrids resistant to ‘ink disease’ (Phytophthora spp.) were obtained in France, Portugal and Spain, although difficult to distinguish by morphology. This study focuses on genetic variation using 10 SSRs (11 unlinked loci) from clonally propagated cultivars (574 accessions) of European chestnut (Castanea sativa) and hybrids (71 accessions). They were compared with a representative sample of exotic chestnut species present in the Atlantic area, 47 accessions of Castanea crenata, 37 of Castanea mollissima and 33 of Castanea henryi. Accessions were analysed using a model-based Bayesian procedure (Structure), factorial correspondence analysis and analysis of molecular variance. The main chestnut species, hybrids and alien introgressions were differentiated. Two main origins of variability in European cultivated chestnut were found in the Iberian Peninsula, one in the North and a second in the Centre. Andalusian and Canary Island accessions could be assigned to both of these zones, which indicate that they could have been colonised with cultivars originating from either zone, in the case of the Canary Islands from the sixteenth century on.

International audience; Thermogenesis and heat generating tissues in inflorescences of the giant taro (Alocasia macrorrhizos (L.) G. Don) were studied from December 2005 to February 2006, on the Island of Espiritu Santo, Vanuatu. Temperatures were recorded in the ambient air, in the peduncle tissue, and on 12 positions within spadices during periods of maximum thermogenic activity, in the early morning hours of the female and male phases. The study showed that there were three thermogenic tissues: the sterile appendix, the fertile male part, and the differentiated sterile area below the fertile male part. During the female phase, heat was generated by the sterile appendix and the differentiated sterile area below the fertile male part, the smallest region of the spadix (mean ± SD = 0.86 ± 0.24 cm, 3.17% of the spadix length), and most probably by the fertile male part. Within the spadix, average temperatures gradually increased from the base of the female part and reached the first peak at the midpoint of the differentiated sterile area below the fertile male part (36.11 ± 1.54 °C). After that, they gradually decreased towards the midpoint of the fertile male part and increased again, reaching a second (main) peak at 1/4 of the sterile appendix height (44.83 ± 1.87 °C). From 1/4 to 1/2 of the appendix height they remained at more or less the same level, and then they decreased towards the tip of the spadix. During the male phase, heat was generated only within the fertile male part.; La thermogenèse et les tissus thermogénétiques du taro géant (Alocasia macrorrhizos (L.) G. Don) ont été étudiés de Décembre 2005 à Février 2006 sur l’île d’Espiritu Santo au Vanuatu. Les températures ont été mesurées dans l’air ambiant, dans le pédoncule ainsi que dans 12 emplacements à l’intérieur des spadices pendant les périodes d’activité thermogénétique maximale, au petit matin et pendant les phases femelles et mâles. L’étude a montré l’existence de trois tissus thermogénétiques : l’appendice stérile, la partie mâle fertile et la zone stérile différenciée située sous la partie mâle fertile. Durant la phase femelle, la chaleur était générée par l’appendice stérile et par la zone stérile différenciée sous la zone mâle fertile, soit la plus courte zone (0,86 ± 0,24 cm de long, soit 3,17 % du spadice), enfin très probablement par la zone mâle fertile elle-même. Á l’intérieur du spadice, les températures augmentaient progressivement à partir de la base de la partie femelle et atteignaient leur premier pic à la moitié de la zone stérile différenciée sous la zone mâle fertile (36,11 ± 1,54 °C). Ensuite, elles diminuaient graduellement vers le milieu de la zone mâle fertile, augmentaient à nouveau avant d’atteindre le second pic (le principal) au quart de la hauteur de l’appendice stérile (44,83 ± 1,87 °C). Entre le quart et la moitié de la hauteur de l’appendice, elles conservaient plus ou moins le même degré de température, puis décroissaient vers l’apex du spadice. Durant la phase mâle, la chaleur n’était générée que par la partie mâle fertile.

International audience; For sweet cherry (Prunus avium L.), as for other fruit tree species, there is an increasing interest in learning more about growth and fruiting traits of the tree in order to improve tree training in the orchard, especially for high density planting. The objective of this paper is to give an overview of current knowledge on tree architecture and physiology, and its bearing on training improvement. From an architectural viewpoint, the cherry tree is characterized by two main features: (1) it has upright scaffold branches (secondary bending is due to weight) with lateral flowering on the preformed portion of both short and long shoots; and (2) it is characterized by a strong dimorphism between short and long shoots, with a marked acrotony, i.e., longer laterals are in the top position, just below the annual growth termination. As with other fruit crops, all training and pruning methods are multifunctional, i.e., they have various effects on both tree architecture (distribution of the laterals in the canopy, shoot demography, etc.) and light interception and distribution within the tree canopy. Both of these subsequently influence fruit quality. The same training technique may have synergistic and/or antagonistic effects on architecture and light environment. A critical step, then, is to improve knowledge of the consequences of the techniques used for canopy management. A second step is to develop methods which allow for anticipation of branching and flowering for the following years and not only ones that correct current problems. These critical steps are the basis for implementing the emerging concept of detail or precision tree management to achieve sustainable yields of high fruit quality.

International audience; The French sweet cherry (Prunus avium L.) breeding programme of the Institut National de la Recherche Agronomique (INRA) began 30 years ago. Its objectives were to increase fruit size, quality and firmness, to expand the ripening period and to improve tree traits such as fruiting habit and precocity. Recently, the search for reduced susceptibility to fruit cracking was included and supported by genetic mapping studies with molecular markers. In the last four years, five new varieties have been selected and distributed commercially by our CEP innovation. These are: 'Ferpin', 'Folfer', 'Fermina', 'Ferdiva' and 'Fertard'. They extend the maturity period from 'Burlat' maturity to 40 days after 'Burlat'. The new varieties have large fruit size and good firmness. 'Fermina' is quite tolerant to fruit cracking. In the near future, three new varieties from the same series will be released; these are identified as: V 3868 (very large fruit size), V 3239 (large fruit size of good quality) and V 3476 (high productivity and firmness).

La capacité photosynthétique de vitroplants de vigne (var. Gravesac) a été déterminée à l'aide d'un dispositif de mesures des échanges gazeux en circuit ouvert. L'activité photosynthétique et la respiration de la plante sont importantes en culture in vitro. La photosynthèse nette maximale est de 2 µmol m-2 s-1 a 500 µ11-1 de CO2. A 350 µ11-1 de CO2 la photosynthèse est de 1,6 µmol m-2 s-1. La respiration a l'obscurité est de 0,018 µmol s-1 g-1 de poids sec total. La quantité totale des sucres solubles dans le milieu de culture reste constante pendant les deux mois de culture. Le saccharose est totalement hydrolysé en glucose et en fructose. Les vitroplants de Gravesac ne prélèvent pas de sucres dans le milieu, ce qui confirme leur degré élevé d'autotrophie dans ces conditions de culture. La comparaison entre les échanges gazeux de vitroplants et des plantes cultivées en serre met en évidence une réduction de 80% de l'activité in vitro. Evaluation of the photoautotrophic ability of Vitis plantlets (rootstock var Gravesac): Set-up of a special open flow gas exchange system The photosynthetic ability of Vitis rootstock plantlets (var. Gravesac) was estimated in vitro with an open flow system specially designed for in vitro culture. CO2 response curves were established and respiration was also measured. The maximum net photosynthetic rate, reached at 500 µ11-1 of CO2, is 2 µmol m-2 s-1. At 350 µ11-1 CO2 the photosynthetic activity is 1.6 µmol m-2 s-1. The dark respiration rate is 0.018 µmol s-1 g-1 of total dry weight. The total amount of soluble carbohydrates in the medium remains the same whether plantlets were present or not. In the medium with plantlets, the sucrose is entirely hydrolysed in glucose and fructose within two months. No carbohydrate uptake from the medium was recorded indicating an autotrophic behaviour. Measurements of CO2 exchange were also performed at leaves of plants cultivated in a greenhouse. The photosynthetic activity of in vitro plants accounts only for 20% of the level of greenhouse-grown plants., VITIS - Journal of Grapevine Research, Vol. 35 No. 2 (1996): Vitis

We investigated the changes in the expression profiles of the partially resistant apricot (Prunus armeniaca L.) cultivar Goldrich following inoculation with Plum pox virus (PPV) using cDNA-amplification fragment length polymorphism (AFLP). Altered expression patterns were detected and twenty-one differentially expressed cDNA had homologies with genes in databases coding for proteins involved in metabolism, signal transduction, defense, stress and intra/intercellular connections. Seven of the modified expressed patterns were further investigated by semi-quantitative RT-PCR or Northern blotting. The expression patterns of five of these genes were confirmed in the partially resistant P. armeniaca cv. 'Goldrich' and assessed in a susceptible genotype. One of these cDNAs, coding for a putative class III chitinase, appeared to be repressed in infected plants of the partially resistant genotype and expressed in the susceptible one which could be related to the partially resistant phenotype. On the contrary, the expression patterns of the genes coding for a transketolase, a kinesin-like and an ankyrin-like protein, were clearly linked to the susceptible interaction. These candidate genes could play a role either in the compatible interaction leading to virus invasion or to the quantitative resistance of apricot to PPV.

Twelve Arabidopsis accessions were challenged with Plum pox potyvirus (PPV) isolates representative of the four PPV strains. Each accession supported local and systemic infection by at least some of the PPV isolates, but high variability was observed in the behavior of the five PPV isolates or the 12 Arabidopsis accessions. Resistance to local infection or long-distance movement occurred in about 40% of all the accession-isolate combinations analyzed. Except for Nd-1, all accessions showed resistance to local infection by PPV-SoC; in the Landsberg erecta (Ler) accession, this resistance was compromised by sgt1 and rar1 mutations, suggesting that it could be controlled by an R gene-mediated resistance pathway. While most of the susceptible accessions were symptomless, PPV induced severe symptoms on inflorescences in C24, Ler, and Bay-0 as early as 15 days after inoculation. Genetic analyses indicated that these interaction phenotypes are controlled by different genetic systems. The restriction of long-distance movement of PPV-El Amar and of another member of genus Potyvirus, Lettuce mosaic virus, in Col-0 requires the RTM genes, indicating for the first time that the RTM system may provide a broad range, potyvirus-specific protection against systemic infection. The restriction to PPVPS long-distance movement in Cvi-1 is controlled by a single recessive gene, designated rpv1, which was mapped to chromosome 1. The nuclear inclusion polymerase b-capsid protein region of the viral genome appears to be responsible for the ability of PPV-R to overcome rpv1-mediated resistance.

International audience

A total of 45 microsatellites (SSRs) were developed for mapping in Fragaria. They included 31 newly isolated codominant genomic SSRs from F. nubicola and a further 14 SSRs, derived from an expressed sequence tagged library (EST-SSRs) of the cultivated strawberry, F. x ananassa. These, and an additional 64 previously characterised but unmapped SSRs and EST-SSRs, were scored in the diploid Fragaria interspecific F2 mapping population (FVxFN) derived from a cross between F. vesca 815 and F. nubicola 601. The cosegregation data of these 109 SSRs, and of 73 previously mapped molecular markers, were used to elaborate an enhanced linkage map. The map is composed of 182 molecular markers (175 microsatellites, six gene specific markers and one sequence-characterised amplified region) and spans 424 cM over seven linkage groups. The average marker spacing is 2.3 cM/marker and the map now contains just eight gaps longer than 10 cM. The transferability of the new SSR markers to the cultivated strawberry was demonstrated using eight cultivars. Because of the transferable nature of these markers, the map produced will provide a useful reference framework for the development of linkage maps of the cultivated strawberry and for the development of other key resources for Fragaria such as a physical map. In addition, the map now provides a framework upon which to place transferable markers, such as genes of known function, for comparative mapping purposes within Rosaceae.

The Sharka disease caused by the potyvirus Plum pox virus (PPV) is one of the most serious viral diseases affecting stone fruit trees. The study of PPV/Prunus interaction under greenhouse controlled conditions is space, time, labor consuming. While the PPV/Prunus interactions are now quite well known at the whole plant level, few data however are available on the interactions between the virus and the Prunus host plants at the cellular level. Using a green fluorescent protein (GFP)-tagged M type PPV strain, combined to an in vitro inoculation procedure, we developed a novel tool to track PPV invasion in Prunus persica (peach) cv. GF305 and Prunus armeniaca (apricot) cv. Screara susceptible hosts. Different graft combinations were performed using in vitro-maintained healthy or GFP-tagged PPV infected 'GF305' and 'Screara'. Contact for 30 days in grafts between the inoculum and the genotype to be tested were found sufficient to allow the systemic spread of the recombinant virus: fluorescence from GFP-tagged PPV could easily be detected in the entire plant under a binocular microscope allowing quick and reliable sorting of infected plants. Using a fluorescence stereomicroscopy or confocal microscopy, GFP could also be observed in stem cross-sections especially in epidermis and pith cells. In vitro grafting inoculation with GFP-tagged PPV provides a new and powerful tool to facilitate mid-term virus maintenance. Moreover, this tool will be of special importance in the study of PPV infection dynamics in Prunus, allowing as well precise observations of cellular events related to PPV/Prunus interactions.

Bulked segregant analysis combined with AFLPs was used to identify molecular markers linked to the Rca 2 gene conferring resistance to Colletotrichum acutatum pathogenicity group 2 which causes anthracnose in the octoploid strawberry Fragaria x ananassa. DNA bulks originating from a cross between the resistant cultivar 'Capitola' and the susceptible cultivar 'Pajaro' were screened with 110 EcoRI/M se IAFLP combinations. Four AFLP markers were found linked in coupling phase to Rca 2 with recombination percentages between 0% and 17.7%. Among the four markers linked to the resistance gene, two were converted into SCAR markers (STS-Rca 2417 and STS-Rca 2240) and screened in a large segregating population including 179 genotypes. The Rca 2 resistance gene was estimated to be 0.6 cM from STS-Rca 2417 and 2.8 cM from STS-Rca 2240. The presence/absence of the two SCAR markers was further studied in 43 cultivars of F. x ananassa, including 14 susceptible, 28 resistant, and one intermediate genotype. Results showed that 81.4% and 62.8% of the resistant/susceptible genotypes were correctly predicted by using STS-Rca 2417 and STS-Rca 2240, respectively. The 14 susceptible genotypes showed no amplification for either SCARs. These developed SCARs constitute new tools for indirect selection criteria of anthracnose resistance genotypes in strawberry breeding programs.

We developed primers for the amplification of 24 polymorphic nuclear microsatellites in apricot (Prunus armeniaca L.). Thirteen loci originated from three genomic libraries enriched for TC, TG and AAG motifs. Eight loci were developed from three fruit EST (Expressed-Sequence-Tag) libraries and three from a leaf cDNA microsatellite-enriched library. There were up to nine alleles per polymorphic locus in 12 different cultivars. No difference in allele numbers were shown between cDNA and genomic-source loci. Mean expected heterozygosity was 0.65 (range: 0.15–0.87). Mendelian segregation was confirmed for all loci. These markers should be helpful for diversity studies, genome mapping and cultivar identification in apricot and related species.

International audience

The development of saturated linkage maps using transferable markers, restriction fragment length polymorphisms, and micro-satellites has provided a foundation for fruit tree genetics and breeding. A Prunus reference map with 562 such markers is available, and a further set of 13 maps constructed with a subset of these markers has allowed genome comparison among seven Prunus diploid ( x = 8) species (almond, peach, apricot, cherry, Prunus ferganensis, Prunus davidiana , and Prunus cerasifera ); marker colinearity was the rule with all of them. Preliminary results of the comparison between apple and Prunus maps suggest a high level of synteny between these two genera. Conserved genomic regions have also been detected between Prunus and Arabidopsis . By using the data from different linkage maps anchored with the reference Prunus map, it has been possible to establish, in a general map, the position of 28 major genes affecting agronomic characters found in different species. Markers tightly linked to the major genes responsible for the expression of important traits (disease/pest resistances, fruit/nut quality, self-incompatibility, etc.) have been developed in apple and Prunus and are currently in use for marker-assisted selection in breeding programs. Quantitative character dissection using linkage maps and candidate gene approaches has already started. Genomic tools such as the Prunus physical map, large EST collections in both Prunus and Malus , and the establishment of the map position of high numbers of ESTs are required for a better understanding of the Rosaceae genome and to foster additional research and applications on fruit tree genetics.

Prunus species express a more or less wide spectrum of resistance to root-knot nematodes (RKN) of the genus Meloidogyne. Among them, sources from Myrobalan plum (P. cerasifera) control all major and minor RKN species tested. In this outbreeding species, the clones P.2175 and P.2980 are heterozygous for the Ma single dominant gene and carry the alleles Ma1 and Ma3, respectively. Each allele confers a high-level resistance to the predominant RKN, M. arenaria, M. incognita and M. javanica and to the Florida isolate of an unknown Meloidogyne sp. which overcomes the resistance from peach and almond sources. The polymorphism of two coupling-phase SCAR markers tightly linked to Ma, SCAL19690 and SCAFLP2202, was evaluated within diverse diploid Prunus accessions. This material belongs to the subgenera Prunophora (Myrobalan and apricot) or Amygdalus (peach, almond and almond-peach) and includes the RKN resistance sources ‘Nemared’, ‘Alnem 1’ and ‘GF.557’. The alleles SCAL19690 and SCAFLP2202 were not present in three apricot cultivars (‘Moniqui’, ‘Luizet’ and ‘Stark Early Orange’) representative of the genetic diversity of this species and they segregated in an interspecific cross between P.2980 and apricot. These results suggest that apricot, reported as resistant to M. arenaria, M. incognita and M. javanica, and the Myrobalan plum might possess two different resistance systems. SCAL19690 and SCAFLP2202 were also absent from all tested Amygdalus material, whatever its resistance to RKN. Eight Myrobalan×Amygdalus segregating progenies including bispecific (P.2175 or P.2980×peach or almond) and trispecific (P.2175 or P.2980×almond-peach) hybrids were tested with the Florida isolate to identify individuals carrying the Ma resistance alleles. Both SCARs were then evaluated for segregation in these progenies to develop marker-assisted selection of Prunus interspecific rootstocks. SCAL19690 and SCAFLP2202 could be clearly detected and their tight linkage to Ma1 and Ma3 was confirmed. Consequently these SCARs appear to be powerful tools to screen for RKN resistance conferred by the Ma gene. They should also facilitate marker-assisted pyramiding of Ma with other resistance genes from the Amygdalus subgenus or from the botanically-related Armeniaca section.

In a previous study, cDNA microsatellite markers were described in apricot (Prunus armeniaca L.). Specific PCR primers were designed to amplify the microsatellite-containing regions from genomic DNA in different Prunus species. In the present work, cDNA microsatellite markers were developed in the hexaploid Prunus domestica L. species and polymorphism was ascertained in a segregating plum population. Co-dominant mendelian segregation of alleles was demonstrated and microsatellite polymorphism displayed up to 6 alleles per SSR locus per individual. Parentage lineage of three full-sib European plum cultivars (cv. ‘Cacanska najbolja’, ‘Cacanska rana’ and ‘Cacanska lepotica’) was reconstructed by the analysis of the above nuclear SSR markers, completed by four chloroplastic microsatellite loci. The six most informative nuclear loci enabled discrimination between the three Cacak cultivars and unrelated individuals as well as the previously proposed parents, ‘Wangenheim’ and ‘Pozegaca’. Data obtained support previous evidence that these cultivars originated from the ‘Stanley’ cultivar. However, SSR analysis finally excluded ‘Wangenheim’ as the other possible parent. Based on the results obtained with nuclear and chloroplast SSR loci, we propose the origin of those three Cacak cultivars in a cross between ‘Stanley’ as the mother plant and ‘Ruth gerstetter’ as the pollinator. Furthermore, we demonstrate the utility of these apricot SSR markers for genotype fingerprinting of the hexaploid plum cultivars.

International audience

A set of 109 microsatellite primer pairs recently developed for peach and cherry have been studied in the almond x peach F(2) progeny previously used to construct a saturated Prunus map containing mainly restriction fragment length polymorphism markers. All but one gave amplification products, and 87 (80%) segregated in the progeny and detected 96 loci. The resulting Prunus map contains a total of 342 markers covering a total distance of 522 cM. The approximate position of nine additional simple sequence repeats (SSRs) was established by comparison with other almond and peach maps. SSRs were placed in all the eight linkage groups of this map, and their distribution was relatively even, providing a genome-wide coverage with an average density of 5.4 cM/SSR. Twenty-four single-locus SSRs, highly polymorphic in peach, and each falling within 24 evenly spaced approximately 25-cM regions covering the whole Prunus genome, are proposed as a 'genotyping set' useful as a reference for fingerprinting, pedigree and genetic analysis of this species.

International audience

International audience

EFPP 2002 : disease resistance in plant pathology; International audience

International audience; As in many other fleshy fruits, the predominant organic acids in ripe peach (Prunus persica (L.) Batsch) fruit are malic and citric acids. The accumulation of these metabolites in fruit flesh is regulated during fruit development. Six peach fruitrelated genes implicated in organic acid metabolism (mitochondrial citrate synthase; cytosolic NAD-dependent malate dehydrogenase, and cytosolic NADP-dependent isocitrate dehydrogenase) and storage (vacuolar proton translocating pumps: one vacuolar H¹-ATPase, and two vacuolar H¹-pyrophosphatases) were cloned. Five of these peach genes were homologous to genes isolated from fruit in other fleshy fruit species. Phylogenetic and expression analyses suggested the existence of a particular vacuolar pyrophosphatase highly expressed in fruit. The sixth gene was the first cytosolic NAD dependent malate dehydrogenase gene isolated from fruit. Gene expression was studied during the fruit development of two peach cultivars, a normal-acid (Fantasia) and a low-acid (Jalousia) cultivar. The overall expression patterns of the organic acid-related genes appeared strikingly similar for the two cultivars. The genes involved in organic acid metabolism showed a stronger expression in ripening fruit than during the earlier phases of development, but their expression patterns were not necessarily correlated with the changes in organic acid contents. The tonoplast proton pumps showed a biphasic expression pattern more consistent with the patterns of organic acid accumulation, and the tonoplast pyrophosphatases were more highly expressed in the fruit of the low-acid cultivar during the second rapid growth phase of the fruit.

Plum pox virus (PPV) resistant rootstocks would be useful to control the spread of PPV in nurseries and orchards. The PPV-resistant transgenic Prunus domestica plum clone C-5 was used as a parent with Prunus spinosa to develop PPV resistant hybrid progeny. This work showed that C-5 plum is sexually compatible with the Prunus rootstock species P. spinosa. Resistance assays of chip-bud inoculated plants following two cycles of growth and cold-induced dormancy demonstrated that the transgenic hybrid clones were symptomless and DAS-ELISA negative. Further, immuno-blotting failed to detect PPV CP in inoculated transgenic hybrids. These results demonstrated the usefulness of C-5 for developing PPV resistant rootstocks with P. spinosa.

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National audience

Un essai utilisant des plantes obtenues a partir de boutures et presentant une gamme de dommages causes par le mildiou, donc de vigueur potentielle, a ete utilise pour etudier les interrelations entre les divers caracteres associes a l'accumulation de reserves de glucides et au rendement. La technique de la regression progressive a ete utilisee pour les analyser. Pour la premiere fois, le cycle de trois ans conduisant a du raisin recolte a ainsi pu etre etudie a l'etat isole.

Previous studies have established that chloroplasts are inherited paternally in Actinidia interspecific crosses. However, fertilisation problems in interspecific crosses may affect the transmission of organelles. Six female clones, i.e. ‘Abbott’, ‘Bruno’, ‘Greensill’, ‘Hayward’, ‘Jones’, ‘Monty’, and four male clones were used to identify cpDNA polymorphisms within the cultivated kiwifruit species A. deliciosa. The restriction patterns by HpaII of a chloroplast fragment amplified by PCR with a pair of universal primers revealed a polymorphism at the intraspecific level. The inheritance of cpDNA in 143 seedlings from three intraspecific crosses in kiwifruit (Actinidia deliciosa) was studied. All offspring displayed the restriction pattern of the paternal parent, indicating that maternal inheritance of cpDNA in kiwifruit is rare at best. Strict maternal inheritance of mtDNA was confirmed in the same crosses used to investigate cpDNA transmission. Studies of cytoplasmic inheritance in the Actinidia genus represent to date the best documented report of differential organelle inheritance of cpDNA and mtDNA in angiosperms.

International audience

Resume : Chez Juglans regia L. ‘Lara’, des observations bihebdomadaires de l’allongement de trois types morphologiques de pousses annuelles floriferes (monocycliques, avec ou sans petit axe a developpement immediat, et bicycliques) en fonction de quatre types de rameaux porteurs ont ete realisees sur des arbres âges de 4 ans, au cours d’une saison de croissance, dans le Sud-Ouest de la France. Chez les arbres etudies, l’influence du type de rameau porteur apparait essentiellement sur les dates de debut d’allongement des pousses annuelles monocycliques. La longueur des pousses porteuses n’est pas correlee a la longueur des pousses monocycliques nouvellement emises, mais elle l’est avec la longueur des pousses bicyliques portees. Chez les pousses floriferes bicycliques, deux vagues d’allongement successives, l’une printaniere et l’autre estivale ont ete decrites au cours d’un cycle annuel de croissance. L’interruption intra-annuelle de l’allongement se traduit par la presence d’une serie de cataphylles separees par des entre-noeuds courts. Les pousses printanieres se differencient des pousses estivales par la structure et le nombre d’organes foliaires emis. L’influence de la duree d’allongement, de la longueur et du nombre de feuilles de la pousse printaniere sur l’edification d’un rameau acrotone a developpement immediat suivie ou non d’une pousse estivale a ete etudiee. Mots cles : Juglans regia ‘Lara’, noyer commun, allongement, croissance primaire, morphologie, pousse annuelle.

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National audience

International audience

International audience

6. International Cherry Symposium : Renaca, CHILE - NOV 15-19, 2009 Publisher : International Society for Horticultural Science (ISHS); International audience; Three-year (2006, 2008 and 2009) QTL detection studies were conducted at INRA-Bordeaux (France) on a sweet cherry F 1 progeny population derived from the cross between 'Regina' and 'Lapins'. 'Regina' is a very late blooming and ripening variety with low fruit cracking susceptibility. 'Lapins', one of the first widely commercialised self-fertile varieties, blooms relatively early, has an intermediate ripening date, and is relatively susceptible to fruit cracking. The progeny is composed of 124 F 1 individuals planted on their own roots in the orchard and their duplicates were grafted on Tabel Edabriz and planted in pots. A partially saturated linkage map was constructed with 89 and 72 SSR markers for both parents, 'Regina' and 'Lapins', respectively. Traits were measured during 2 or 3 years, including bud break date, bloom and ripening dates, cracking susceptibility, fruit weight, and fruit firmness. Fruit cracking (% of cracked fruits), based on the observation of 100 randomly selected fruits, was evaluated on individuals planted in the orchard and on individuals planted in pots, according to different tests. The first test was conducted using the potted trees grown in a plastic tunnel with an automatic irrigation system. The trees were moved into the tunnel at the period of maximum cracking susceptibility and constant amounts of water were sprayed over the trees for five consecutive days. For the second test, trees planted in the field were used and fruits were harvested at physiological maturity. Finally, these same trees were used for the classical Christensen test. The strongest and most stable QTLs were found for the following traits: bloom and ripening dates (LG4 and LG5), mean fruit weight (LG2 and LG3), and fruit firmness (LG2). QTLs for cracking susceptibility were relatively weak and variable across years. Implications for sweet cherry breeding and the use of marker-assisted selection are discussed.

International audience

International audience

International audience

Interspecific crosses between Actinidia arguta (2n = 4x) and A. deliciosa (2n = 6x) were carried out in order to transfer cold resistance from a wild to the cultivated kiwifruit species. Of the 65 progenies obtained and analysed by flow cytometry, 16 were diploid, one was tetraploid and 48 were, as expected, pentaploid. Morphologically, the diploids can be distinguished from the pentaploids by their longer lamina. The existence of 5x progenies confirms the existence of gene flow between A. arguta and A. deliciosa, whereas the existence of 2x and 4x progenies provides evidence for parthenogenesis within the Actinidia genus following an interspecific cross. The study demonstrates the utility of flow cytometry for genomic analysis of progenies derived from interspecific crosses. Possible uses of both sexual and parthenogenetic progenies in the breeding and genetics of kiwifruit are discussed.

Plant phenolics have drawn increasing attention due to their potential nutritional benefits. Although the basic reactions of the phenolics biosynthetic pathways in plants have been intensively analyzed, the regulation of their accumulation and flux through the pathway is not that well established. The aim of this study was to use a strawberry (Fragaria × ananassa) microarray to investigate gene expression patterns associated with the accumulation of phenylpropanoids, flavonoids, and anthocyanins in strawberry fruit. An examination of the transcriptome, coupled with metabolite profiling data from different commercial varieties, was undertaken to identify genes whose expression correlated with altered phenolics composition. Seventeen comparative microarray analyses revealed 15 genes that were differentially (more than 200-fold) expressed in phenolics-rich versus phenolics-poor varieties. The results were validated by heterologous expression of the peroxidase FaPRX27 gene, which showed the highest altered expression level (more than 900-fold). The encoded protein was functionally characterized and is assumed to be involved in lignin formation during strawberry fruit ripening. Quantitative trait locus analysis indicated that the genomic region of FaPRX27 is associated with the fruit color trait. Down-regulation of the CHALCONE SYNTHASE gene and concomitant induction of FaPRX27 expression diverted the flux from anthocyanins to lignin. The results highlight the competition of the different phenolics pathways for their common precursors. The list of the 15 candidates provides new genes that are likely to impact polyphenol accumulation in strawberry fruit and could be used to develop molecular markers to select phenolics-rich germplasm., This work was supported by PLANT-KBBE FraGenomics, by the Euroinvestigacion Subprogram from PLANT_KBBE Call, provided by the Spanish Science and Technology Ministry (grant no. EUI2008–03770 to A.M.), by the Centre CONSOLIDER on Agrigenomics and the Xarxa de Referencia en Biotecnología of the Generalitat de Catalunya, and by the Deutsche Forschungsgemeinschaft (grant no. SCHW634/14 to S.-Y.Y. and W.S.).

International audience; Our aim was to assess the possible differential effect of increasing temperatures due to global warming on dormancy progression in apricot. The effect of a range of chilling temperatures on vegetative and reproductive bud dormancy progression in excised shoots was examined during two seasons. Temperature treatments were applied in different dormant stages to evaluate the possible interaction of date × temperature for dormancy release in apricot. During sampling, chill accumulated in the field ranged from 0 to 49 chill portions (CPs), corresponding to 0–100% of the chilling requirement (CR) of the apricot selection Z505-2. Forcing conditions were applied after a 60-day chill treatment on each sampling date, and rate to budbreak (1/mean time to bud break: MTB−1) was established in vegetative (terminal and lateral) and reproductive buds to determine depth of dormancy. Results showed that the stage of dormancy has a strong influence on the effect of different temperatures on dormancy progression in apricot. For the first time, a non-linear effect of different chilling temperatures during the dormancy cycle in apricot was obtained, especially in the superior range of temperatures traditionally considered to release dormancy. Thus, introduction of this differential effect could help to improve the models to estimate dormancy release in the context of climate change.

International audience

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National audience