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Research Article - UN DECADE ON ECOSYSTEM RESTORATION The degradation of riparian ecosystems occurring throughout the past decades has motivated efforts aimed at the restoration of these ecosystems. The success of active revegetation approaches to restoration requires appropriate selection of reproductive material, which in turn requires knowledge of seed traits and germination. Alnus glutinosa (L.) Gaertn. (common alder) is a key riparian tree widely used in restoration projects, and has recently been classified as comprising three species: A. glutinosa; A. lusitanica Vít, Douda, & Mand ak; and A. rohlenae Vít, Douda, & Mand ak. To help guide restoration species selection, we assessed differences among populations of these species by (1) investigating seed weight, morphology, and germination success from a large population set and (2)modeling germination success in each species in relation to morphological traits and environmental conditions. Seedswere collected from 12 populations encompassing the latitudinal extremes of the species complex, and were then characterized and germinated. Ploidy levels and species were distinguished using cytometric analysis. Site-level climatic data and seed morphology datawere used to model germination success for each species. All seed traits differed between populations and one morphological-trait (seed weight-to-area ratio) differed significantly between the three species. Germination modeling showed that the southwestern species, A. lusitanica, responded positively to high temperature extremes, suggesting tolerance to the climate changes projected for southern Europe. Populations of A. lusitanica located at the latitudinal rear edge of commonalder’s distribution appear to show establishmentfacilitating adaptations, and therefore may contribute to ecological restoration efforts under a range of environmental conditions info:eu-repo/semantics/publishedVersion

International audience; Biological control (BC) is defined as the use of living natural enemies, antagonists, or competitors (biological control agents) to control other living organisms. In the second half of the last century, the general interest in BC has increased considerably because greater environmental awareness in society and the implementation of integrated pest management (IPM) strategies have pushed towards the development of environmentally friendly control approaches. However, BC is still only rarely used for pathogens (fungi, bacteria, viruses, nematodes, and phytoplasmas) of forest trees. Here, we present and discuss the biological specificities of both the hosts and the fungal pathogens which may account for this situation. To increase the likelihood of BC success, we suggest a holistic approach involving the use of top-down regulators, competitors and amensalists, all exerting pressure on the pathogen, as well as bottom-up forces helping the host (e.g., endophytes, mycorrhiza). Moreover, BC to mitigate emerging forest diseases should be fully integrated into other sustainable management strategies. Finally, we propose guidelines for developing an efficient BC of emerging fungal pathogens of forest trees.

Tree species-mixing has been suggested as one option to counteract the adverse effects of global change on tree mineral nutrition, yet the effect of mixing on nutrient availability remains poorly documented. We therefore analyzed the current foliar nutrient (N, P, K, Ca, Mg) quantities and ilr balances (isometric log transformed ratios between elements or groups of elements) for 261 European beech and 248 Scots pine trees from 15 sites, each consisting of one beech-pine mixed stand and the respective monocultures, across a gradient of environmental conditions in Europe. We hypothesized an overall positive effect of mixing on tree foliar nutrient content, and that this mixing effect would be stronger on nutrient-poor sites. Using linear mixed models and multivariate linear regression models, we first tested for the effects of species (beech/pine) and composition (pure/mixed) across all sites; we then investigated whether the species-mixing effect was related to site fertility. The nutrient composition of beech leaves and pine needles differed significantly for all ilr balances. For both species, significant mixing effects were detected for some nutrients and ilr balances; those effects, however, could not be consistently related to contrasted nutrient composition between species. For most nutrients and ilr balances, the mixing effect was influenced by the site nutritional status, but the pattern differed from expectation: absence or minor differences between monocultures and mixtures at the lower end of the chemical fertility gradient, and maximum differences in rich soils. The contrasting foliar nutrient composition of pine and beech trees and the site nutrient status only partly explained the mixing effects on tree mineral nutrition. Our results claim for a better understanding of nutrient-related mechanisms associated with complementarity and points towards the need to further expand the existing frameworks to account for the multivariate nature of tree nutrition., The main autor obtained a PhD grant from the ‘Fonds National de la Recherche Scientifique’ (FNRS-FRIA) and additional funding support from the Walloon forest service (Service Public de Wallonie—Département de la Nature et des Forêts) through the 5 year research programme “Accord cadre de recherches et de vulgarisation forestières”.

International audience; Dothistroma needle blight (DNB) is a serious pine disease present worldwide caused by the ascomycetous fungi Dothistroma septosporum and Dothistroma pini. Based on multiplex PCR analysis of 11 microsatellite markers screened on 253 D. septosporum isolates obtained from 32 sites across Slovakia, a total of 137 unique multilocus haplotypes (MLHs) were detected. The majority of MLHs (n = 91) were represented by a single isolate, but 13 MLHs were found at two different sites, and in some cases, these were separated by large distances. Four population clusters were identified using a discriminant analysis of principal components (DAPC). The genetic clusters obtained from the DAPC were mixed throughout the country and were not restricted to particular host species. Although both mating types of D. septosporum were found to be in an almost perfect 1:1 ratio in both the non-clone-corrected and clone-corrected datasets, random mating was rejected in the entire dataset. Random mating was only supported in the Pinus mugo group planted in urban areas and on a smaller spatial scale in two sites (Kalnica and Litava) using the clone-corrected dataset. These findings suggest a mixed mode of reproduction with an important component of sexual reproduction, although the sexual stage of the fungus (teleomorph) has not been physically observed in Slovakia yet. The examination of spatial relationships using spatial principal component analyses and the presence of isolation-by-distance together with relatively high genetic diversity suggests the pathogen has been long established in Slovakia and spread naturally across the landscape. However, the weak population structure and findings of identical clones at widely separated sites strongly suggests some degree of human assisted dispersal.

Producción Científica, Fusarium circinatum, the causal agent of pine pitch canker (PPC), is currently one of the most important threats of Pinus spp. globally. This pathogen is known in many pine-growing regions, including natural and planted forests, and can affect all life stages of trees, from emerging seedlings to mature trees. Despite the importance of PPC, the global distribution of F. circinatum is poorly documented, and this problem is also true of the hosts within countries that are affected. The aim of this study was to review the global distribution of F. circinatum, with a particular focus on Europe. We considered (1) the current and historical pathogen records, both positive and negative, based on confirmed reports from Europe and globally; (2) the genetic diversity and population structure of the pathogen; (3) the current distribution of PPC in Europe, comparing published models of predicted disease distribution; and (4) host susceptibility by reviewing literature and generating a comprehensive list of known hosts for the fungus. These data were collated from 41 countries and used to compile a specially constructed geo-database. A review of 6297 observation records showed that F. circinatum and the symptoms it causes on conifers occurred in 14 countries, including four in Europe, and is absent in 28 countries. Field observations and experimental data from 138 host species revealed 106 susceptible host species including 85 Pinus species, 6 non-pine tree species and 15 grass and herb species. Our data confirm that susceptibility to F. circinatum varies between different host species, tree ages and environmental characteristics. Knowledge on the geographic distribution, host range and the relative susceptibility of different hosts is essential for disease management, mitigation and containment strategies. The findings reported in this review will support countries that are currently free of F. circinatum in implementing effective procedures and restrictions and prevent further spread of the pathogen., COST Action FP1406 (PINESTRENGTH), the Estonian Science Foundation grant PSG136, the Forestry Commission, United Kingdom, the Phytophthora Research Centre Reg. No. CZ.02.1.01/0.0/0.0/15_003/0000453, a project co-financed by the European Regional Development Fund., French National Research Agency (ANR) (ANR-11-LABX-0002-01), BBSRC, Defra, ESRC, the Forestry Commission, NERC and the Scottish Government (BB/L012251/1)

International audience; The characterization of the largest worldwide representative data set of apricot (Prunus armeniaca L.) germplasm was performed using molecular markers. Genetic diversity and structure of the cultivated apricot genetic resources were analyzed to decipher the history of diffusion of this species around the world. A common set of 25 microsatellite markers was used for genotyping a total of 890 apricot accessions in different collections from the center of origin to the more recent regions of apricot culture. Using a Bayesian model-based clustering approach, the apricot genotypes can be structured into five different genetic clusters (F-ST = 0.174), correlated with the geographical regions of origin of the accessions. Accessions from China and Central Asia were clustered together and exhibited the highest levels of diversity, confirming an origin in this region. A loss of genetic diversity was observed from the center of origin to both western and eastern zones of recent apricot culture. Altogether, our results revealed that apricot spread from China and Central Asia, defined as the center of origin, following three major diffusion routes with a decreasing gradient of genetic variation in each geographical group. The identification of specific alleles outside the center of origin confirmed the existence of different secondary apricot diversification centers. The present work provides more understanding of the worldwide history of apricot species diffusion as well as the field of conservation of the available genetic resources. Data have been used to define an apricot core collection based on molecular marker diversity which will be useful for further identification of genomic regions associated with commercially important horticultural traits through genome-wide association studies to sustain apricot breeding programs.

International audience; Abstract Climate change is expected to severely affect cropping systems and food production in many parts of the world unless local adaptation can ameliorate these impacts. Ensembles of crop simulation models can be useful tools for assessing if proposed adaptation options are capable of achieving target yields, whilst also quantifying the share of uncertainty in the simulated crop impact resulting from the crop models themselves. Although some studies have analysed the influence of ensemble size on model outcomes, the effect of ensemble composition has not yet been properly appraised. Moreover, results and derived recommendations typically rely on averaged ensemble simulation results without accounting sufficiently for the spread of model outcomes. Therefore, we developed an Ensemble Outcome Agreement (EOA) index, which analyses the effect of changes in composition and size of a multi-model ensemble (MME) to evaluate the level of agreement between MME outcomes with respect to a given hypothesis (e.g. that adaptation measures result in positive crop responses). We analysed the recommendations of a previous study performed with an ensemble of 17 crop models and testing 54 adaptation options for rainfed winter wheat (Triticum aestivum L.) at Lleida (NE Spain) under perturbed conditions of temperature, precipitation and atmospheric CO2 concentration. Our results confirmed that most adaptations recommended in the previous study have a positive effect. However, we also showed that some options did not remain recommendable in specific conditions if different ensembles were considered. Using EOA, we were able to identify the adaptation options for which there is high confidence in their effectiveness at enhancing yields, even under severe climate perturbations. These include substituting spring wheat for winter wheat combined with earlier sowing dates and standard or longer duration cultivars, or introducing supplementary irrigation, the latter increasing EOA values in all cases. There is low confidence in recovering yields to baseline levels, although this target could be attained for some adaptation options under moderate climate perturbations. Recommendations derived from such robust results may provide crucial information for stakeholders seeking to implement adaptation measures.

Climate resilience refers to the capacity of a system to buffer core functions against climate-related uncertainty and variability (1). The occurrence of diversity in responses to weather variability within a functional group or species (2, 3), such as European wheat that supplies bread and pasta, can ensure a reasonable yield regardless of weather conditions and provides genetic material for selection under changing climate (4). Genetic diversity is not directly related to response diversity, as shown for forage crops (5). Since most of the forage crop species were distributed among several weather response clusters and most of the clusters contained several species, the genetic closeness did not fully explain responses to critical weather conditions. This phenomenon may represent a keystone for breeding and thus deserves to be explored further. Indeed, genetic response diversity deserves more attention with respect to yield and quality (6). The suitability of response diversity to describe agronomic fitness in wheat monocultures is questioned by Snowdon et al. (7), but no arguments are presented. We (8) consider the approach suitable to assess and enhance the resilience of monocultures and thereby increase the stability of total yield under weather variability regardless of whether the complementary cultivars are cultivated on one farm or within a region, national borders, or Europe. Cultivar (or crop) mixtures common in forage cultivation and sometimes used with cereals … [↵][1]1To whom correspondence should be addressed. Email: helena.kahiluoto{at}lut.fi. [1]: #xref-corresp-1-1

1. When tree‐species mixtures are more productive than monocultures, higher light absorption is often suggested as a cause. However, few studies have quantified this effect and even fewer have examined which light‐related interactions are most important, such as the effects of species interactions on tree allometric relationships and crown architecture, differences in vertical or horizontal canopy structure, phenology of deciduous species or the mixing effects on tree size and stand density. 2. In this study, measurements of tree sizes and stand structures were combined with a detailed tree‐level light model (Maestra) to examine the contribution of each light‐related interaction on tree‐ and stand‐level light absorption at 21 sites, each of which contained a triplet of plots including a mixture and monocultures of Fagus sylvatica and Pinus sylvestris (63 plots). These sites were distributed across the current distribution of these species within Europe. 3. Averaged across all sites, the light absorption of mixtures was 14% higher than the mean of the monocultures. At the whole community level, this positive effect of mixing on light absorption increased as canopy volume or site productivity increased, but was unrelated to climate. At the species population or individual tree levels, the mixing effect on light absorption resulted from light‐related interactions involving vertical canopy structure, stand density, the presence of a deciduous species (F. sylvatica), as well as the effects of mixing on tree size and allometric relationships between diameter and height, crown diameter and crown length. 4. The mixing effects on light absorption were only correlated with the mixing effects on growth for P. sylvestris, suggesting that the mixing effects on this species were driven by the light‐related interactions, whereas mixing effects on F. sylvatica or whole community growth were probably driven by non‐light‐related interactions. 5. Synthesis. The overall positive effect of mixing on light absorption was the result of a range of light‐related interactions. However, the relative importance of these interactions varied between sites and is likely to vary between other species combinations and as stands develop. Czech Republic Ministry of Education, Youth and Sports. Grant Number: COST CZ ‐ LD14063 and and LD14074; COST (European Cooperation in Science and Technology). Grant Number: COST Action EuMIXFOR; German Research Foundation. Grant Number: FO 791/4‐1

20 p.-3 fig., Although epigenetic modifications have been intensely investigated over the last decade due to their role in crop adaptation to rapid climate change, it is unclear which epigenetic changes are heritable and therefore transmitted to their progeny. The identification of epigenetic marks that are transmitted to the next generations is of primary importance for their use in breeding and for the development of new cultivars with a broad-spectrum of tolerance/resistance to abiotic and biotic stresses. In this review, we discuss general aspects of plant responses to environmental stresses and provide an overview of recent findings on the role of transgenerational epigenetic modifications in crops. In addition, we take the opportunity to describe the aims of EPI-CATCH, an international COST action consortium composed by researchers from 28 countries. The aim of this COST action launched in 2020 is: (1) to define standardized pipelines and methods used in the study of epigenetic mechanisms in plants, (2) update, share, and exchange findings in epigenetic responses to environmental stresses in plants, (3) develop new concepts and frontiers in plant epigenetics and epigenomics, (4) enhance dissemination, communication, and transfer of knowledge in plant epigenetics and epigenomics, This finalization of the review was funded by COST Action CA19125—EPIgenetic mechanisms of Crop Adaptation to Climate cHange.

In most temperate fruit trees, fruits are located on one-year old shoots. In Prunus species, flowers and fruits are born in axillary position along those shoots. The axillary bud fate and branching patterns are thus key components of the cultivar potential fruit production. The objective of this study was to analyze the branching and bearing behaviors of 1-year-old shoots of apricot cultivars and clones genetically closely related. Shoot structures were analyzed in terms of axillary bud fates using hidden semi-Markov chains and compared depending on the genotype, year and shoot length. The shoots were composed of three successive zones containing latent buds (basal zone), central flower buds (median zone) and vegeta-tive buds (distal zone), respectively. The last two zones contained few associated flower buds. The zones length (in number of metamers) and occurrence strongly depended on shoot development in the two successive years. With decrease in the number of metamers per shoot, the last two zones become shorter or may not develop. While the number of metamers of the basal and distal zones and the number of associated flower buds correlated to the number of metamers of the shoot, the number of metamers of the median zone and the transition probability from the median to the distal zone were cultivar specific.

Marcais, Benoit/0000-0002-8107-644X; Jung, Thomas/0000-0003-2034-0718; Jung, Marilia Horta/0000-0003-2219-8647; Corcobado, Tamara/0000-0001-5762-4728; Lyubenova, Aneta/0000-0001-7414-1808; Pastircak, Martin/0000-0001-5118-9518; Pastircakova, Katarina/0000-0003-0371-428X; Fort, Tomas/0000-0002-4186-0918; Oskay, Funda/0000-0002-8918-5595; Oliva, Jonas/0000-0003-2418-2542; FORT, Tania/0000-0001-6998-5985; Kiss, Levente/0000-0002-4785-4308; Iturritxa, Eugenia/0000-0002-6390-5873; Aday Kaya, Ayse Gulden/0000-0002-5631-6026; Nave, Corina/0000-0003-2290-8282 WOS:000452564900005 The spatial distribution and niche differentiation of three closely related species (Erysiphe alphitoides, Erysiphe quercicola and Erysiphe hypophylla) causing oak powdery mildew was studied at scales ranging from the European continent, where they are invasive, to a single leaf. While E. alphitoides was dominant at all scales, E. quercicola and E. hypophylla had restricted geographic, stand and leaf distributions. The large-scale distributions were likely explained by climatic factors and species environmental tolerances, with E. quercicola being more frequent in warmer climates and E. hypophylla in colder climates. The extensive sampling and molecular analyses revealed the cryptic invasion of E. quercicola in nine countries from which it had not previously been recorded. The presence of the three species was also strongly affected by host factors, such as oak species and developmental stage. Segregation patterns between Erysiphe species were observed at the leaf scale, between and within leaf surfaces, suggesting competitive effects. (C) 2018 Elsevier Ltd and British Mycological Society. All rights reserved. Conseil Regional d'AquitaineRegion Nouvelle-Aquitaine [20030304002FA, 20040305003FA]; European Union FEDEREuropean Commission [2003227]; Investissements d'AvenirFrench National Research Agency (ANR) [ANR-10-EQPX-16-01]; European BiodivERsA project "RESIPATH: Responses of European Forests and Society to Invasive Pathogens"; Portuguese Science and Technology FoundationPortuguese Foundation for Science and Technology [BIODIVERSA/0002/2012, ANR-13-EBID-0005-01]; ANR (France)French National Research Agency (ANR) [ANR-13-BSV7-0011]; Japan Society for the Promotion of ScienceMinistry of Education, Culture, Sports, Science and Technology, Japan (MEXT)Japan Society for the Promotion of Science [16K07613, 16F16097]; Slovak Research and Development AgencySlovak Research and Development Agency [APVV-15 0210] We thank Adrien Bolay, Caroline Gordon, Banga Grigaliunaite, Gabriela Juhasova, Vasyl Heluta, Seyed Akbar Khodaparast, Eleni Topalidou, Gy-ongyver Nagy, and all other collectors, for providing samples. Part of the analyses were performed at the Genome Transcriptome Facility of Bordeaux (grants from the Conseil Regional d'Aquitaine no 20030304002FA and 20040305003FA, from the European Union FEDER no 2003227 and from Investissements d'Avenir ANR-10-EQPX-16-01). Funding was obtained through the European BiodivERsA project "RESIPATH: Responses of European Forests and Society to Invasive Pathogens" co-financed by national funds (ANR-13-EBID-0005-01 for France, Portuguese Science and Technology Foundation Ref. BIODIVERSA/0002/2012). Other grants came from the ANR (France) Funfit project (ANR-13-BSV7-0011), the Japan Society for the Promotion of Science Grant-in-Aid for Scientific Research (Nos. 16K07613 and16F16097), and the Slovak Research and Development Agency under the contract No. APVV-15 0210.

Trees scale leaf (A(L)) and xylem (A(X)) areas to couple leaf transpiration and carbon gain with xylem water transport. Some species are known to acclimate in A(L) : A(X) balance in response to climate conditions, but whether trees of different species acclimate in A(L) : A(X) in similar ways over their entire (continental) distributions is unknown. We analyzed the species and climate effects on the scaling of A(L) vs A(X) in branches of conifers (Pinus sylvestris, Picea abies) and broadleaved (Betula pendula, Populus tremula) sampled across a continental wide transect in Europe. Along the branch axis, A(L) and A(X) change in equal proportion (isometric scaling: b similar to 1) as for trees. Branches of similar length converged in the scaling of A(L) vs A(X) with an exponent of b = 0.58 across European climates irrespective of species. Branches of slow- growing trees from Northern and Southern regions preferentially allocated into new leaf rather than xylem area, with older xylem rings contributing to maintaining total xylem conductivity. In conclusion, trees in contrasting climates adjust their functional balance between water transport and leaf transpiration by maintaining biomass allocation to leaves, and adjusting their growth rate and xylem production to maintain xylem conductance.

International audience; Many studies have reported that hydraulic properties vary considerably between tree species, but little is known about their intraspecific variation and, therefore, their capacity to adapt to a warmer and drier climate. Here, we quantify phenotypic divergence and clinal variation for embolism resistance, hydraulic conductivity and branch growth, in four tree species, two angiosperms (Betula pendula, Populus tremula) and two conifers (Picea abies, Pinus sylvestris), across their latitudinal distribution in Europe. Growth and hydraulic efficiency varied widely within species and between populations. The variability of embolism resistance was in general weaker than that of growth and hydraulic efficiency, and very low for all species but Populus tremula. In addition, no and weak support for a safety vs. efficiency trade-off was observed for the angiosperm and conifer species, respectively. The limited variability of embolism resistance observed here for all species except Populus tremula, suggests that forest populations will unlikely be able to adapt hydraulically to drier conditions through the evolution of embolism resistance.

International audience; Transgenic, 'HoneySweet' plums inoculated with Plum pox virus, recombinant strain (PPV-Rec) alone, PPV-Rec + Apple chlorotic leafspot virus (ACLSV), PPV-Rec + Prune dwarf virus (PDV), and PPV-Rec + ACLSV + PDV were grown in an open field under high and permanent infection pressure both from graft inoculation and natural aphid vectors for 8 years. 'HoneySweet' control trees were non-graft-inoculated trees. Plants were monitored by symptomology, DAS-ELISA, semiquantitative (SQ)-ELISA, and real-time (RT)-PCR. Inoculum shoots showed severe PPV symptoms from the first year after inoculation throughout the study. Mild PPV symptoms appeared in some of the basal leaves of graft-inoculated 'HoneySweet' trees in the second year following inoculation. During the following six years, even these mild and isolated symptoms on 'HoneySweet' trees diminished. The presence of PPV in these basal areas of 'HoneySweet' trees was confirmed by ELISA, ISEM, and RT-PCR. Relative concentration of PPV determined by SQ-ELISA and by RT-PCR was lower than in leaves of inoculum shoots. No difference in PPV symptoms was observed between PPV-Rec, and combinations PPV-Rec with other viruses. While no symptoms of ACLSV appeared during the study, ACLSV was detected by ELISA and RT-PCR. No symptoms of PDV appeared and PDV was not detected. 'HoneySweet' trees exposed to natural aphid-vectored PPV were not infected. Fruits of 'HoneySweet' were qualitatively and quantitatively compared with fruits of 'Stanley' and 'Domaci svestka' in 2010 from noninfected trees of 'HoneySweet' and fruits from 'HoneySweet' trees graft-inoculated with PPV-Rec + ACLSV + PDV were both of high quality and comparable to, or for certain characteristics, of higher quality than fruit of the commercial cultivars which were evaluated.

International audience; There is evidence that recently occurring top dieback of Norway spruce (Picea abies (L.) Karst.) trees in southern Norway is associated with drought stress. We compared functional wood traits of 20 healthy looking trees and 20 trees with visual signs of top dieback. SilviScan technology was applied to measure cell dimensions (lumen and cell wall thickness) in a selected set of trunk wood specimens where vulnerability to cavitation (P 50) data were available. The conduit wall reinforcement ((t/b)²) was a good proxy for P 50. Cell dimensions were measured on wood cores of all 40 trees; theoretical vulnerability of single annual rings could be thus estimated. Declining trees tended to have lower (t/b)² before and during a period of water deficit (difference between precipitation and potential evapotranspiration) that lasted from 2004 to 2006. The results are discussed with respect to genetic predisposition. Introduction In southern Norway, recently occurring top dieback in 40-50 years old forest stands of Norway spruce (Picea abies (L.) Karst.) is thought to be associated with climatic extremes (Hentschel et al. 2014). In this region, the period between 2004 and 2006 was characterized by high water deficits during the growing season, estimated as the difference between the cumulative precipitation and the potential evapotranspiration (see Fig 1 in Hentschel et al. 2014). During this period, trees with symptoms of top dieback (Fig. 1) showed lower intrinsic water-use efficiency that is associated with increased stomatal conductance (Hentschel et al. 2014) and produced wood with lower density, indicating higher vulnerability to cavitation (Rosner et al. 2014). Functional traits for estimating hydraulic vulnerability gain increasing importance as screening tools because hydraulic experiments are labour intensive or prone to errors (Cochard et al. 2013). In this study, we extend an existing dataset (Rosner et al. 2014) with tree samples and derive functional traits for hydraulic vulnerability from tracheid dimensions assessed by SilviScan technology (Evans 1994). Thereafter we document how these proxies changed over the years in 20 healthy looking and in 20 declining trees in order to learn more about the predisposing factors for top dieback in Norway spruce in southern Norway.

COST Action FP1106 STReESS ; EU Life Programme (LIFE12 ENV/FI/000409 ; Ajut Marie Curie IF fellowship (No 659191) Phloem osmolality and its components are involved in basic cell metabolism, cell growth, and in various physiological processes including the ability of living cells to withstand drought and frost. Osmolality and sugar composition responses to environmental stresses have been extensively studied for leaves, but less for the secondary phloem of plant stems and branches. Leaf osmotic concentration and the share of pinitol and raffinose among soluble sugars increase with increasing drought or cold stress, and osmotic concentration is adjusted with osmoregulation. We hypothesize that similar responses occur in the secondary phloem of branches. We collected living bark samples from branches of adult Pinus sylvestris, Picea abies, Betula pendula and Populus tremula trees across Europe, from boreal Northern Finland to Mediterranean Portugal. In all studied species, the observed variation in phloem osmolality was mainly driven by variation in phloem water content, while tissue solute content was rather constant across regions. Osmoregulation, in which osmolality is controlled by variable tissue solute content, was stronger for Betula and Populus in comparison to the evergreen conifers. Osmolality was lowest in mid-latitude region, and from there increased by 37% toward northern Europe and 38% toward southern Europe due to low phloem water content in these regions. The ratio of raffinose to all soluble sugars was negligible at mid-latitudes and increased toward north and south, reflecting its role in cold and drought tolerance. For pinitol, another sugar known for contributing to stress tolerance, no such latitudinal pattern was observed. The proportion of sucrose was remarkably low and that of hexoses (i.e., glucose and fructose) high at mid-latitudes. The ratio of starch to all non-structural carbohydrates increased toward the northern latitudes in agreement with the build-up of osmotically inactive C reservoir that can be converted into soluble sugars during winter acclimation in these cold regions. Present results for the secondary phloem of trees suggest that adjustment with tissue water content plays an important role in osmolality dynamics. Furthermore, trees acclimated to dry and cold climate showed high phloem osmolality and raffinose proportion.

Origin ‘HoneySweet’ originated as a seedling from the open pollination of ‘Bluebyrd’ plum (Scorza and Fogle, 1999). The pollen parent of ‘HoneySweet’ is unknown. ‘HoneySweet’ was originally selected in vitro as a regenerated shoot from a hypocotyl slice that had been transfected with Agrobacterium tumefaciens EHA 101 carrying the plasmid pGA482GG/PPV-CP-33 (Scorza et al., 1994). The regenerated, transgenic shoot, coded as C5, along with other transgenic shoots, was rooted in vitro and transferred to a greenhouse. Following greenhouse testing using graft and aphid inoculations with the M and D strains of Plum pox virus (PPV), C5 (later patented as ‘HoneySweet’), was asexually propagated by bud grafting on to standard rootstocks, including Prunus persica (GF305 peach seedlings), Prunus domestica (European plum seedlings), Prunus myrobalan, and GF 8-1 (Prunus cerasifera × P. munsoniana). An overview of the development of ‘HoneySweet’ plum and molecular characterization can be found in Scorza et al. (2013a).

Summary Dothistroma needle blight (DNB) is one of the most important diseases of pine. Although its notoriety stems from Southern Hemisphere epidemics in Pinus radiata plantations, the disease has increased in prevalence and severity in areas of the Northern Hemisphere, including Europe, during the last two decades. This increase has largely been attributed to expanded planting of susceptible hosts, anthropogenic dispersal of the causative pathogens and changes in climate conducive to disease development. The last comprehensive review of DNB was published in 2004, with updates on geographic distribution and host species in 2009. Importantly, the recognition that two species, Dothistroma septosporum and D. pini, cause DNB emerged only relatively recently in 2004. These two species are morphologically very similar, and DNA-based techniques are needed to distinguish between them. Consequently, many records of host species affected or geographic location of DNB prior to 2004 are inconclusive or even misleading. The objectives of this review were (i) to provide a new database in which detailed records of DNB from 62 countries are collated; (ii) to chart the current global distribution of D. septosporum and D. pini; (iii) to list all known host species and to consider their susceptibility globally; (iv) to collate the published results of provenance trials; and (v) to consider the effects of site factors on disease incidence and severity. The review shows that DNB occurs in 76 countries, with D. septosporum confirmed to occur in 44 and D. pini in 13. There are now 109 documented Pinaceae host taxa for Dothistroma species, spanning six genera (Abies, Cedrus, Larix, Picea, Pinus and Pseudotsuga), with Pinus being the dominant host genus, accounting for 95 host taxa. The relative susceptibilities of these hosts to Dothistroma species are reported, providing a resource to inform species choice in forest planting. Country records show that most DNB outbreaks in Europe occur on Pinus nigra and its subspecies. It is anticipated that the collaborative work described in this review will both underpin a broader global research strategy to manage DNB in the future and provide a model for the study of other forest pathogens.

International audience; Widely grown cultivars of apricot usually exhibit phenotypic variation among clones that may lead to different bearing potentials. Clone selection is one of the breeding tools that may be used to improve bearing behavior. However, little is known about the basis of the different bearing behaviors among clones of a particular cultivar. Our assumption was that these behaviors could be linked to shoot morphology and demography. This study aimed to analyze the morphology of 1-year-old shoots in five clones issuing from a classical Czech cultivar, 'Velkopavlovicka', belonging to the Hungarian best cultivars group. In 12-year-old trees, branches were described over 3 years and from the second to the fourth orders. In these branches, all annual shoots that developed in a given year were described at the node level and were classified into three types depending on their length. For each clone, the proportion of the different shoot types, the number of flower buds per shoot and per node ( considering central and lateral axillary flower buds), as well as the presence of fruits were considered. The mean number of flowers per shoot was higher in the first observation than in the second, and the largest differences among clones were found for medium shoots. All clones displayed similar within-branch demography of shoot types, but differences were found between years, which appeared related to the tree bearing status. This study confirmed that 'Velkopavlovicka' clones bear most fruits on short or medium-length shoots. It also suggests that fruit load and shoot length influence the regularity of flowering, in conjunction with the shoot type proportion, which also matters at more global scales, such as branches or trees. Our results show that Doc. Blatny, LE-111 and VP-LE-12/2 are more suitable than the other evaluated clones of 'Velkopavlovicka' from an agronomic point of view, although further investigations will be necessary to assess them.

International audience; Analyses of genetic diversity and phylogenetic relationships illuminate the origin and domestication of crop species and have important implications for plant breeding programs and the conservation of genetic resources. Apricot ( Prunus armeniaca L.) genetic resources in collections that are widely dispersed around the world were assessed using 25 simple sequence repeat ( SSR) markers. Analysis of allelic diversity among SSR data revealed at least a double pattern of diffusion from Central Asia to eastern and western countries with a clear east-west loss of genetic diversity related to the genetic bottleneck during apricot domestication. Structure and phylogenetic analysis indicated that accessions from Central Asia and China were genetically most diverse, suggesting that this large region constitutes the apricot center of origin.

BFP - Equipe Virologie; First Report of Little cherry virus 1 Infecting Apricot in the Czech Republic

International audience; Sharka is one of the most serious viral diseases affecting stone fruit species and, in apricot, resistance to its viral agent, the Plum Pox Virus (PPV), is conferred by one major quantitative trait locus (QTL), named PPVres for PPV resistance. Previous studies indicated that PPV-resistant cultivars and breeding progenies can be selected by using a set of SSR markers (named PGS) targeting the PPVres locus. However, before these markers can be employed for marker-assisted selection, they were validated in a wide range of genetic backgrounds and environments. We used a total of 11 mapping populations issued from three distinct environments to confirm that this marker set located within the QTL adequately predicted PPV resistance. In this study, we show that selection of PPV-resistant material based only on markers co-localizing with the PPVres major locus is not fully reliable. Indeed, genotype-phenotype discrepancies were observed depending on the progeny and the PPV-resistant/susceptible parents. While most of the PPV-resistant individuals displayed the resistant alleles, a significant number of PPV-susceptible individuals showed the same resistant haplotype. An effect of the PPV strain used for phenotyping was also demonstrated. We thus hypothesize that the presence of other factors or genes involved in the mechanism of resistance to sharka in apricot could explain these unexpected results. Our work indicates that the current PGS marker set is not broadly applicable for MAS and that marker-assisted breeding based on the sole PPVres locus is not sufficient to unambiguously select PPV-resistant apricot cultivars.

International audience; A large database of invasive forest pathogens (IFPs) was developed to investigate the patterns and determinants of invasion in Europe. Detailed taxonomic and biological information on the invasive species was combined with country-specific data on land use, climate, and the time since invasion to identify the determinants of invasiveness, and to differentiate the class of environments which share territorial and climate features associated with a susceptibility to invasion. IFPs increased exponentially in the last four decades. Until 1919, IFPs already present moved across Europe. Then, new IFPs were introduced mainly from North America, and recently from Asia. Hybrid pathogens also appeared. Countries with a wider range of environments, higher human impact or international trade hosted more IFPs. Rainfall influenced the diffusion rates. Environmental conditions of the new and original ranges and systematic and ecological attributes affected invasiveness. Further spread of established IFPs is expected in countries that have experienced commercial isolation in the recent past. Densely populated countries with high environmental diversity may be the weakest links in attempts to prevent new arrivals. Tight coordination of actions against new arrivals is needed. Eradication seems impossible, and prevention seems the only reliable measure, although this will be difficult in the face of global mobility.

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; POLAK J., KUMAR J., KRSKA B., RAVELONANDRO M. (2012): Biotech/GM crops in horticulture: Plum cv. HoneySweet resistant to Plum pox virus. Plant Protect. Sci., 48 (Special Issue): S43-S48. Commercialisation of Biotech/GM (Biotech) crops started in 1995. Not only field crops, but also horticultural transgenic crops are under development and are beginning to be commercialised. Genetic engineering has the potential to revolutionise fruit tree breeding. The development of transgenic fruit cultivars is in progress. Over the past 20 years an international public sector research team has collaborated in the development of HoneySweet plum which is highly resistant to Plum pox virus (PPV) the most devastating disease of plums and other stone fruits. HoneySweet was deregulated in the USA in 2010. HoneySweet (aka C5) has been evaluated for eleven years (2002-2012) in a regulated field trial in the Czech Republic for the resistance to PPV, Prune dwarf virus (PDV), and Apple chlorotic leaf spot virus (ACLSV), all of them being serious diseases of plum. Even under the high and permanent infection pressure produced through grafting, PPV has only been detected in HoneySweet trees in several leaves and fruits situated close to the point of inoculum grafting. The lack of infection spread in HoneySweet demonstrates its high level of PPV resistance. Co-infections of PPV with PDV and/or ACLSV had practically no influence on the quantity and quality of HoneySweet fruit which are large, sweet, and of a high eating quality. In many respects, they are superior to the fruits of the well-known cultivar Stanley. Many fruit growers and fruit tree nurseries in the Czech Republic are supportive of the deregulation of HoneySweet plum to help improve the plum production and control the spread of PPV.

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; Plum pox virus (PPV) is a devastating stone fruit disease of major importance, and better understanding of the genetic control of resistance to this trait would be useful for more efficient development of resistant cultivars. Previous studies have reported a locus of major effect from PPV resistance on linkage group 1. The current study confirms these results by mapping plum pox virus resistance in a F1 progeny issued from a cross between "Harlayne", as a PPV-resistant parent, and "Vestar" as a susceptible parent. The hybrids were grafted simultaneously and subsequently inoculated with the PPV-M and D strains. The symptom scoring on leaves was performed nine times over two vegetative cycles. Marker-trait associations were analyzed using the Kruskal-Wallis (KW) non-parametric test, and the PPV resistance loci were mapped using composite interval mapping (CIM). We show that both analyses (KW and CIM) highlighted the upper part of linkage group 1 of the apricot "Harlayne" genitor.

In this study we determined the microclimatic drivers of storage water use in Scots pine (Pinus sylvestris L.) growing in a temperate climate. The storage water use was modeled using the ANAFORE model, integrating a dynamic water flow and – storage model with a process-based transpiration model. The model was calibrated and validated with sap flow measurements for the growing season of 2000 (26 May–18 October). Because there was no severe soil drought during the study period, we were able to study atmospheric effects. Incoming radiation was the main driver of storage water use. The general trends of sap flow and storage water use are similar, and follow more or less the pattern of incoming radiation. Nevertheless, considerable differences in the day-to-day pattern of sap flow and storage water use were observed, mainly driven by vapour pressure deficit (VPD). During dry atmospheric conditions (high VPD) storage water use was reduced. This reduction was disproportionally higher than the reduction in measured sap flow. Our results suggest that the trees did not rely more on storage water during periods of atmospheric drought, without severe soil drought. A third important factor was the tree water deficit. When storage compartments were depleted beyond a threshold, storage water use was limited due to the low water potential in the storage compartments. The maximum relative contribution of storage water to daily transpiration was also constrained by an increasing tree water deficit.

Knowledge of belowground structures and processes is essential for understanding and predicting ecosystem functioning, and consequently in the development of adaptive strategies to safeguard production from trees and woody plants into the future. In the past, research has mainly been concentrated on growth models for the prediction of agronomic or forest production. Newly emerging scientific challenges, e.g. climate change and sustainable development, call for new integrated predictive methods where root systems development will become a key element for understanding global biological systems. The types of input data available from the various branches of woody root research, including biomass allocation, architecture, biomechanics, water and nutrient supply, are discussed with a view to the possibility of incorporating them into a more generic developmental model. We discuss here the main focus of root system modelling to date, including a description of simple allometric biomass models, and biomechanical stress models, and then build in complexity through static growth models towards architecture models. The next progressive and logical step in developing an inclusive developmental model that integrates these modelling approaches is discussed. Knowledge of belowground structures and processes is essential for understanding and predicting ecosystem functioning, and consequently in the development of adaptive strategies to safeguard production from trees and woody plants into the future. In the past, research has mainly been concentrated on growth models for the prediction of agronomic or forest production. Newly emerging scientific challenges, e.g. climate change and sustainable development, call for new integrated predictive methods where root systems development will become a key element for understanding global biological systems. The types of input data available from the various branches of woody root research, including biomass allocation, architecture, biomechanics, water and nutrient supply, are discussed with a view to the possibility of incorporating them into a more generic developmental model. We discuss here the main focus of root system modelling to date, including a description of simple allometric biomass models, and biomechanical stress models, and then build in complexity through static growth models towards architecture models. The next progressive and logical step in developing an inclusive developmental model that integrates these modelling approaches is discussed. Knowledge of belowground structures and processes is essential for understanding and predicting ecosystem functioning, and consequently in the development of adaptive strategies to safeguard production from trees and woody plants into the future. In the past, research has mainly been concentrated on growth models for the prediction of agronomic or forest production. Newly emerging scientific challenges, e.g. climate change and sustainable development, call for new integrated predictive methods where root systems development will become a key element for understanding global biological systems. The types of input data available from the various branches of woody root research, including biomass allocation, architecture, biomechanics, water and nutrient supply, are discussed with a view to the possibility of incorporating them into a more generic developmental model. We discuss here the main focus of root system modelling to date, including a description of simple allometric biomass models, and biomechanical stress models, and then build in complexity through static growth models towards architecture models. The next progressive and logical step in developing an inclusive developmental model that integrates these modelling approaches is discussed.