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Vegetatively propagated crops suffer from yield loss and reduced stand density and longevity caused by the build‐up of certain pests and pathogens between successive plantings via infected planting material. Here, six seedborne phytosanitary problems of banana are reviewed to evaluate whether a seed degeneration framework is a useful tool to identify approaches to achieve healthier planting materials. Phytoparasitic nematodes and weevils generate gradual declines in yields and in sucker health. Fusarium wilt and banana bunchy top virus cause progressive mat collapse across the field. Symptomless suckers from any mat in infested fields represent a risk of transmitting the disease to a new field. Xanthomonas and ralstonia wilts, due to incomplete systemicity, are intermediate in their threat to yield loss and frequency of transmission in suckers. Losses to banana streak virus are triggered by abiotic stress, although sucker transmission of episomal banana streak virus also contributes. A qualitative equation described here for seed degeneration covers a cycle beginning with the quality and risk factors of the planting material used to plant a new field and ends with the quality and risk factors of the suckers extracted from the field to plant a new field. This review of five planting material multiplication methods commonly used in banana contrasts their differing usefulness to address seed degeneration in the small farm context. It is proposed that initiatives to offset banana seed degeneration should integrate the role of off‐farm actors into decentralized initiatives rather than attempt to duplicate national seed certification frameworks from other true seed or vegetatively propagated crops.

Despite recent international research on the topic, we still have a fuzzy view of local seed networks structure and organization. This is partly due to the high variability of ways of categorising, multiplying and exchanging propagules of crops in the diversity of peasant societies, and also to the heterogeneity of scientific approaches and methodology used for studying seed networks. Beyond the fact that there exist several ways of defining what 'landraces' are, there are multiple types of practices, communities (or social units) and ways of transacting seeds that have been analysed through a great diversity of interests and methodologies. Based on various field examples drawn from MIRES partners' experiences, we will question units and scales relevant for a constructive way of analysing seed systems without harming the diversity of options farmers use for getting the genetic resources they need and/or wish.

SNP genotyping of 114 cultivated sunflower populations showed that the multiplication process and the main traits selected during breeding of sunflower cultivars drove molecular diversity of the populations. The molecular diversity in a set of 114 cultivated sunflower populations was studied by single-nucleotide polymorphism genotyping. These populations were chosen as representative of the 400 entries in the INRA collection received or developed between 1962 and 2011 and made up of land races, open-pollinated varieties, and breeding pools. Mean allele number varied from 1.07 to 1.90. Intra-population variability was slightly reduced according to the number of multiplications since entry but some entries were probably largely homozygous when received. A principal component analysis was used to study inter-population variability. The first 3 axes accounted for 17% of total intra-population variability. The first axis was significantly correlated with seed oil content, more closely than just the distinction between oil and confectionary types. The second axis was related to the presence or absence of restorer genes and the third axis to flowering date and possibly to adaptation to different climates. Our results provide arguments highlighting the effect of the maintenance process on the within population genetic variability as well as on the impact of breeding for major agronomic traits on the between population variability of the collection. Propositions are made to improve sunflower population maintenance procedures to keep maximum genetic variability for future breeding.

International audience; Molecular epidemiology studies further our understanding of migrations of phytopathogenic bacteria, the major determining factor in their emergence. Asiatic citrus canker, caused by Xanthomonas citri pv. citri, was recently reported in Mali and Burkina Faso, a region remote from other contaminated areas. To identify the origin and pathways of these emergences, we used two sets of markers, minisatellites and microsatellites, for investigating different evolutionary scales. Minisatellite typing suggested the introduction of two groups of strains in Mali (DAPC 1 and DAPC 2), consistent with microsatellite typing. DAPC 2 was restricted to Bamako district, whereas DAPC 1 strains were found much more invasive. The latter strains formed a major clonal complex based on microsatellite data with the primary and secondary founders detected in commercial citrus nurseries and orchards. This suggests that human activities played a major role in the spread of DAPC 1 strains via the movement of contaminated propagative material, further supported by the frequent lack of differentiation between populations from geographically distant nurseries and orchards. Approximate Bayesian Computation analyses supported the hypothesis that strains from Burkina Faso resulted from a bridgehead invasion from Mali. Multi-locus variable number of tandem repeat analysis and Approximate Bayesian Computation are useful for understanding invasion routes and pathways of monomorphic bacterial pathogens. (Résumé d'auteur)

Le noisetier d'Afrique, Coula edulis Baill. Olacaceae, est un arbre des forêts denses humides africaines. Il produit des graines d'une grande valeur nutritive qui sont régulièrement récoltées et commercialisées par les populations d'Afrique centrale et de l'Ouest. Cependant, le manque d'informations relatives aux techniques de multiplication de l'espèce est la principale contrainte à sa domestication et à son intégration dans les systèmes agroforestiers locaux. L'étude, conduite parallèlement en pépinière et en milieu naturel, vise à mieux caractériser la germination de C. edulis et à déterminer ses aptitudes au marcottage aérien. Les résultats obtenus indiquent que la germination de C. edulis est très lente et échelonnée avec des taux de levée très faibles, voire nuls. De plus, les prétraitements appliqués aux graines se sont révélés inefficaces pour améliorer la vitesse et le taux de levée des semences. En revanche, le marcottage aérien permet de produire des plants de C. edulis d'une vigueur bien supérieure et dans un délai plus court que les semis en pépinière. Les résultats préliminaires du marcottage aérien sont prometteurs et ouvrent des perspectives intéressantes pour la multiplication et la domestication de l'espèce. L'intégration de Coula edulis dans les systèmes agroforestiers des plants issus du marcottage aérien est donc envisageable.

International audience; Bolboschoenus maritimus is one of the major weed constraints for irrigated rice-cropping systems in the Camargue, France. This perennial plant propagates mainly through the production of numerous tubers. Observations in both controlled conditions and on-field studies were used to enhance the level of knowledge of the biology, functioning and infestation dynamics of B. maritimus, with a view to rationalize weed control practices. It was found that B. maritimus displayed a great potential to produce a large number of shoots, rhizomes and tubers. Its propagation in the field plots depended on the initial weed density and its spatial colonization did not show any preferred direction (isotropic). Further observations that were made in the paddy fields showed an interaction between the different cultural practices that were tested and the infestation dynamics of B. maritimus. Efficient control of B. maritimus infestation in the field should make use of the data reported here, based on three levels: (i) prevention of weed stem proliferation during the cropping season with specific herbicides; (ii) elimination of the tubers after the rice crop; and (iii) reduction of the tuber-germinating ability.

Les forêts de chêne-liège, et en particulier la forêt périurbaine de la Maâmora, près de Rabat (Maroc) sont soumises depuis plusieurs décennies à de fortes pressions anthropiques. Il s'ensuit une dégradation accélérée des peuplements et une grave insuffisance de la régénération naturelle. De nombreux essais ont été entrepris par l'administration forestière pour trouver des solutions, en particulier au travers de la régénération assistée et du bouturage. Ces solutions ont été testées sur plusieurs années. Les résultats sont très probants et ont permis de lancer un programme efficace et à large échelle de rénovation de la subéraie marocaine. Les premières boutures racinées, produites en décembre 1993, ont permis, pour la première fois, l'installation d'essais pour étudier la rhizogenèse des boutures du chêne-liège et le comportement des clones comparé à celui des semis en plantation âgée de 7 ans. Cette étude est réalisée sur un matériel végétal provenant de pieds-mères de semis cultivés intensivement en pépinière. Les principaux résultats obtenus sont résumés comme suit : - les pieds mères ont montré une bonne réactivation au bouturage et à la taille de formation, avec une productivité moyenne de 4 boutures par prélèvement ; - le taux d'enracinement moyen global s'élève à 46%. Les boutures réagissent par la néoformation de 5 racines principales en moyenne ; - les prélèvements excessifs de boutures sur les pieds-mères affectent la vigueur de ces derniers et l'enracinement des boutures ; - les variations inter et intra clonales de l'enracinement sont discutées ???. - le taux de reprise des boutures en plantation est légèrement inférieur à celui des semis, mais la croissance moyenne des boutures et celle des semis sont similaires ; - les boutures racinées plantées, âgées de 7 ans, n'ont pas manifesté de signes de maturation. Elles sont d'une orthotropie normale. - le comportement des boutures et des semis en plantation est discuté ( ???.

The CFC/ICCO/Bioversity International project "Cocoa Productivity and Quality Improvement: a Participatory Approach" (2004-2010), chapter INIAP-Ecuador, provided an opportunity to continue evaluating most of the hybrid and clone trials started during the CFC/ICCO/IPGRI project "Cocoa Germplasm Utilization and Conservation: a Global Approach" (1998-2003), and to start participative cocoa research with the inclusion of producers pursuing a more efficient selection of superior cocoa cultivars. Under the umbrella of the current project, an agrosocio- economic study was completed, providing some useful insights on the multifactor environment which influences cocoa production in three distinct zones of Ecuador. Some important germplasm collecting activities also took place, enriching the phenotypic and genotypic variability of the cocoa genebank held by the Instituto Nacional de Investigaciones Agropecuarias (INIAP) at the Estación Experimental Tropical Pichilingue (EET Pichilingue). The project's period was also fruitful in providing information on the influence of some agronomic factors (compatibility, pruning levels, planting density, drought resistance, differences in flowering and other phenological markers) and on sensorial differences among distinct genotypes. Best hybrid trees were selected and multiplied as clones to compare their performance in trials which are currently being conducted both at the EET Pichilingue and in farmers' fields. These experiments will hopefully be the source of new commercial fine or flavour cocoa cultivars in the near future. The most important output of both abovementioned projects is their contribution, together with other projects, towards building up an important genetic base to gradually develop new cocoa varieties well into the next quarter of the century. Training and opportunities to develop research, agronomic and managerial experience for a number of people locally involved in the project represent an additional dimension in which the project made valuable contributions. We may well divide the cocoa breeding process in Ecuador into two parts, i.e. before and after the implementation period of both projects (1998-2010).

Plants of Coffea arabica L. derived via somatic embryogenesis, namely, somaclones, were evaluated with C. arabica seedlings grown in the nursery. At the time of their transfer to the nursery, somaclones of C. arabica cvs. Caturra and Costa Rica 95 (Catimor) were smaller and less vigorous than seedlings of the same cultivars. Following an initial slow growth for a period of 10 weeks, somaclones began to grow faster than seedlings until both groups of plants were equal in size at 21 weeks (entire duration of growth in the nursery). Comparisons of aerial and root systems of 30-cm long somaclones and seedlings of two cultivars revealed that plants of somaclones were more vigorous than seedlings, based on the higher number of leaves (13-16 vs. 9), larger leaf area (1060-1280 vs. 730- 890 cm2), and greater dry weight of aerial organs (8.5-12 vs. 7.0-7.5 g). For cv. Caturra, the root dry weight of somaclones was significantly greater than that of seedlings (2.7 vs. 1.9 g) and was attributable to the large diameter roots ([0.5 mm). Analysis of 176,000 F1 hybrid somaclones revealed that these exhibited more heterogeneous growth than did the seedlings derived from zygotic embryos; moreover, there was a genotype effect. Almost 9-20% of somaclones required an additional 3-4 months of growth in the nursery, and 8-12% were culled for other undesirable horticultural attributes. Only 0.10-0.23% of somaclones displayed variant phenotypes. The observed somaclone vigor in the nursery was carried over to field performance as these plants were more precocious than seedlings and yielded coffee beans 1 year earlier than seedlings. Keywords Embryo.

Les bas-fonds du plateau de l'Adamaoua constituent des zones pastorales très prisées, mais leur exploitation optimale nécessite des moyens appropriés . Malheureusement, trés peu d'études ont été menées dans ces zones. La Société de Développement et d'Exploitations des Ressources Animales (SODEPA), dans son ranch du Faro, mène des recherches en vue d'intensifier cette exploitation. Une étude comparative de la capacité de reprise et de multiplic a tion des éclats de souche et des boutures de Pennisetum purpureum Schumach. cv Kizozi, trés adapté à ce milieu a été entreprise. L'essai dont le schéma expérimental était une randomisation complète en deux densités d'installation (0,66 m X 0,64 et 1m X 1m) a été mis en place sur des parcelles élémentaires de 30 m2 (3m X 10 m). L'évaluation de la capacité de reprise n'a montré aucune différence significative entre les deux formes de mise en place. En revanche, une différence significative (P

The extend to which seed dispersal influences seedling recruitment is of major importance for forest dynamics. In non-equilibrium situations, seed dispersal might be of even further importance as it is a major determinant of the rate and composition of secondary succession. We modelled primary seed dispersal in a planted pine–spruce stand intensively recolonized by Abies alba and Fagus sylvatica, an ecological situation commonly found throughout south- ern Europe. We then evaluated the role of primary seed dispersal in seedling emergence and recruited seedling density. Using a seed trap experiment and inverse modelling methods, we calibrated short- and medium-distance seed dispersal functions. The relationship between the density of dispersed seed, the density of emerging seedlings and microsite character- istics were assessed using generalized linear models. The cumulative distribution function of seedling-to-nearest-adult distances made it possible to test the concordance between seed rain patterns and seedling spatial distributions. Seed production was highly variable between years for A. alba and F. sylvatica. Seed dispersal was shown to be locally restricted (median dispersal distance of 13.2–19.2 m for A. alba depending on the year and 6.49 m for F. sylvatica). Model prediction was considerably increased when seed production was directly assessed (and not indirectly estimated using diameter, for example). The number of A. alba seedlings that emerged in 1999 was positively correlated with the number of seeds dispersed in 1998 and with the local density of Picea abies adults, and negatively correlated with grass cover. The spatial distribution of seedlings was less aggregated around adult trees than expected from seed dispersal models, but significantly different from random beyond 6 m to the nearest adult for F. sylvatica and 26 m for A. alba. Thus, seed rain patterns are only partially responsible for recruitment dynamics in our model forest. Our study demonstrates that inverse modelling methods are well suited for the study of seed dispersal at the local scale, especially when a direct count of seed production can be made, and are therefore of particularly high interest in forests where several successional stages are present

International audience; Knowledge of propagation mechanisms is important for understanding the invasion ecology and management of invasive plants in order to restore invaded lands. The identification of recruitment pathways is one of the keys to understanding dispersal mechanisms and determining invasive plant control strategies. The objective of this study was to characterize the recruitment processes of Schinus terebenthifolius, one of the most serious plant invaders in Reunion Island's lowlands. Surprisingly, little attention was given in literature to vegetative propagation by suckering as a dispersal mechanism. Yet, field observations on abandoned farmland and riverbanks combined with germination experiments have shown major differences in recruitment patterns between wet and dry areas. On abandoned dryland farms, seedling emergence is 35 times less than on riverbanks and is replaced by suckering. Birds facilitated seed germination, but their role in seed dispersal (ornithochory) appeared minor and restricted to the formation of satellite invasion foci. Water movement appears to be a more efficient vector than ornithochory because it aids seed transportation (hydrochory), seed germination, and suckering on riverbanks. Control and restoration programs must distinguish the two kinds of recruitment that impact on short- and long-distance dispersal.

La formation, réalisée sous contrat avec Forhom (filiale formation du BDPA) dans le cadre du projet PARSAR (Appui à la réhabilitation du secteur agricole et rural), s'est déroulée pendant 5 jours sur le centre de recherche de M'vuazi, Province du Bas-Congo. Sur place l'accueil et la logistique était assuré par un organisme de formation congolais privé, le CEDA. La formation de 5 jours a réuni une quinzaine de cadres et de techniciens de la recherche (INERA) ainsi que des responsables de projet en charge de la production semencière. Elle portait sur les techniques améliorées de production de matériel de plantation du manioc avec plusieurs sessions : Rappels théoriques: biologie, botanique et génétique du manioc. Utilisation des techniques de multiplication rapide sur le manioc (mini bouturage, semences botaniques) avec travaux pratiques. Les principaux ravageurs et pathogènes du manioc et les techniques de protection sanitaire intégrée. La multiplication par culture de tissu: production, assainissement et sevrage des vitroplants. Théorie et Travaux pratiques. Un CD comportant l'ensemble des supports pédagogiques (ppt) et une nombreuse documentation sur les sujets traités à été remis aux participants. Outre cette formation sur le manioc le Cirad avait assuré précédemment avec le Carbap 3 autres sessions sur les Techniques de production semencière pour (1) la banane et le plantain (prestation Carbap), (2) le maïs et l'arachide (prestation Carbap) et (3) les techniques de contrôle, certification et stockage des semences (prestation Cirad). On peut cependant regretter que les termes de références fournis par Forhom pour ces formations, notamment pour la partie manioc, n'aient pas été plus précis et, en particulier, ne n'aient pas fait mention du laboratoire de culture in vitro fonctionnant avec l'appui de l'IITA sur la station de Mvuazi.

La production de plants a été étudiée dans le cadre de la mise en place du plan de gestion de la forêt villageoise de Diouroum. Les informations délivrées par les villageois ont notamment permis d'identifier 26 espèces locales qui se multiplient végétativement. Trois méthodes de multiplication, simples et peu coûteuses, ont été testées ensuite, de mai à juillet 2004. Huit espèces locales ont été étudiées. Des travaux d'excavation ont montré le drageonnage chez Faidherbia albida, Balanites aegyptiaca et Diospyros mespiliformis. La production de plants de F. albida par bouturage de segments de racines atteint, après deux mois, un taux de réussite de 47%, pour un diamètre optimal de 1,5 à 2 cm. Les essais de marcottage aérien ont mis en évidence la possibilité de produire des plants d'Acacia macrostachya, Lannea microcarpa et Tamarindus indica. L'induction de drageons par blessures de racines n'a pas permis d'obtenir de résultats chez les quatre espèces testées (F. albida, B. aegyptiaca, D. mespiliformis et L. microcarpa), durant cette courte période d'observation. De même, les essais de marcottage aérien chez Acacia nilotica et Ficus platyphylla et de bouturage de segments de racines chez L. microcarpa ont apparemment échoué. Ces travaux préliminaires nécessitent des études complémentaires à diverses périodes et durant au moins une année entière.

4th International Symposium on Edible Alliaceae Location: Beijing, China, 2004/04/21-26; International audience; Embryogenic calluses were induced from young leaf explants of garlic (Allium sativum L). Four cultivars, ‘Rouge de la Réunion’, ‘Messidrome’, ‘Morasol’ and ‘Printanor’ have been successfully tested. These calluses expressed up to 90% of embryogenic calluses differentiating globular somatic embryos after 2 months on N6 modified medium supplemented with 2,4-D (0.1 mg l-1) and kinetin (0.5 mg l-1). Embryogenic calluses were used to establish cell suspension cultures of the above-mentioned cultivars. Friable calluses were induced from compact ones, and could give rise to the production of cell suspension cultures composed of small aggregates of embryogenic cells. These suspension cultures were maintained in liquid medium based on N6 modified macro-nutrients and supplemented with 2,4-D/benzyladenine (0.3 mg l-1/0.1 mg l-1). The packed cell volume (PCV) of the suspension cultures increased 2-fold in a 2-week period. These cell suspension cultures led to successful regeneration of mature embryos and their conversion into plantlets. Optimal embryo regeneration efficiency was obtained after plating on semi-solid medium base on N6 macro-nutrients and a balance in 2,4-D/Kinetin (0.1 mg l-1/0.5 mg l-1). A large number of somatic embryos (potentially 8 x 109 to 1011) could be produced per year for each cultivar. The conversion into plantlet was approximately 50%. Plants were successfully acclimatised in greenhouse. Histological analyses were performed along the suspension cultures and regeneration process, and helped for establishing the sequence of culture media. The somatic embryogenic nature was confirmed by single cell origin and polar development of the regenerants. This protocol was used in a goal of mass propagation of garlic plants true to the original type. It would be a key tool for biotechnologies in genetic improvement of garlic.

Background: Banana Mild Mosaic virus (BanMMV) is an unassigned member of the Flexiviridae family infecting banana and plantain (Musa spp). Vertical transmission by vegetative propagation is currently the only known means of propagation of this virus, since no biological vector has been identified nor has experimental mechanical inoculation on susceptible hosts been successful so far. Methods: Nucleotide sequences were obtained from BanMMV isolates originating from various locations worldwide. Two distinct regions of the viral genome were targeted: ORF 1, which encodes the viral RNA-dependent RNA polymerase (RdRp), and a region encompassing the 3' end of ORF5, which encodes the coat protein (CP), and the 3' non-coding region (3' NCR). Both regions play a key role in viral replication and are therefore supposedly very conserved. Results: BanMMV RdRp sequences displayed an extremely high level of molecular diversity when compared to similar sequences obtained from other plant RNA viruses. This situation resulted essentially from a very high ratio of synonymous mutations. A similar analysis performed for a limited selection of banana accessions on the CP/3'NCR region confirmed the high level of diversity observed in the RdRp dataset, characterized by a very high level of synonymous mutations. Analysis of intra-host diversity indicated the existence of two distinct situations with some plants harbouring only closely related sequence variants while others contained up to three widely divergent isolates. Analyses indicated an absence of structuration of the virus genetic diversity either by the geographical origin of the infected Musa accessions or by their genotype. This situation may be, in part, explained by the exchange of banana germplasm between different parts of the world and also by plant-to-plant transmission of the virus, the evidence for which is, for the first time, provided by this study.

In order to validate a mass propagation process of Coffea arabica based on the use of liquid nutrient media, the agronomic performance and trueness-to-type of regenerated trees (selected F1 hybrids) was assessed at a large scale. In a first trial representing 3,000 trees, we determined that the frequency of variants increased exponentially with age of the embryogenic suspension. For the five genotypes, somaclonal variation was low (1.3%) in trees produced from embryogenic callus or 3-month-old cell suspensions and increased in frequency with increasing suspension age (6, 10 and 25% in trees produced from cell suspensions aged 6, 9 and 12 months, respectively). Seven types of phenotypic variants were characterized. Based on vigour and productivity of the regenerated plants, it was possible to class the variants in order of severity of physiological disorders: "Colour of juvenile leaves", "Giant", "Dwarf', "Thick leaf ("Bullata")", "Variegata", "Angustifolia", "Multi-stem". The "Dwarf', "Angustifolia" and "Multi-stem" types were the most frequent among produced plants (1.4, 4.8 and 2.9%, respectively). In a second trial, the agronomic performances of 644 trees derived from somatic embryogenesis were compared with those of normal trees produced from microcuttings for the same four clones. Somaclonal variation has never been observed with microcutting-derived trees. The variant aside (2%), for all clones, the trees had vegetative characteristics, productivity, fertility, and biochemical, mineral and beverage characteristics that were identical to those of the controls. We conclude that propagation of coffee by embryogenic callus or young cell suspensions generated few variants. Moreover, detection of 70% of variants is possible at the nursery stage. Somatic embryogenesis can therefore be considered as a possible mass-propagation technique for coffee, for rapid multiplication of heterozygous structures that should lead to substantial genetic gains compared to traditional pedigree selection schemes.

Introduction. The determination of an adequate container volume that combines rational use of substrate with maximization of vegetative growth is very important to optimize citrus nursery tree production. This experiment aims to evaluate the influence of container volumes on vegetative growth of citrus nursery trees. Materials and Methods. Pera sweet orange nursery trees [Citrus sinensis (L.) Osbeck] budded on Rangpur lime (Citrus limonia Osbeck) were produced in six container volumes [(3.0, 3.8, 4.5, 4.6, 5.0 and 5.8) L], with the respective container dimensions of [(20 × 32, 20 × 35, 22 × 32, 22.5 × 35, 25 × 32 and 25 × 35) cm]. Another 5.0-L container studied had the dimensions of 20 cm x 40 cm. Commercial substrate was composed of Pinus bark and a controlled-release fertilizer was used. Parameter evaluation started after moving the rootstocks from seedling trays, 3.5 months after sowing, to plastic containers and continued until nursery trees reached one year old. The studied parameters were shoot height, diameter and leaf area of rootstocks and nursery trees, bud take percentage and scion and root dry matter of nursery trees. Results and discussion. The development of Rangpur lime plants was not affected by any treatment until budding. The largest container volumes induced faster and more vigorous vegetative development of Pera sweet orange nursery trees budded on Rangpur lime. A 5.0-L container volume could be indicated as a technical and economical option for the production of containerized citrus nursery trees.

In vitro# multiplication is often reported as the main cause for triggering the production of episomal infectious BSV particles in banana hybrid species harbouring some or all of the B (#Musa balbisiana#) genome, through the activation of BSV endogenous pararetrovirus (EPRV) sequences integrated into the B genome. Nevertheless, mass production of vitroplantlets remains the most widely used method for the diffusion of either #Musa# germplasm or new improved hybrid species. A better understanding of the effects of in vitro culture on BSV EPRV activation is thus necessary to evaluate the risks of spreading BSV through the wide diffusion of banana plantlets. In order to evaluate this risk, CIRAD and INIBAP are developing a collaborative project aimed at answering the following questions: Does BSV EPRV activation occur through in vitro culture in all inter-specific hybrid species and in " natural " plantain species too? Is there a correlation between the duration of #in vitro# subculture steps and the percentage of plantlets exhibiting BSV episomal particles ? In order to answer these questions, three different accessions were used: two natural triploid plantains (AAB) - 'Kelong Mekintu' (KM) and 'Black Penkelon' (PK)- and the tetraploid hybrid (AAAB) - CRBP 39. Virus-free suckers were selected and mass propagated using standard in vitro budding methods. During the successive multiplication (proliferation) subcultures, at least 40 shoots were randomly picked and screened for the presence of episomal BSV particles, using standard immuno-capture PCR based detection methods. BSV episomal particles were detected during in vitro culture in both natural plantains and CRBP39 hybrid, with BSV-Ol being the predominantly detected BSV strain . Both natural plantains and CRBP39 displayed similar patterns of activation. Percentages of plantlets indexed positive for BSV-Ol rapidly increased after the first subculture cycles. Depending on cultivars, maximum percentages of BSV-Ol positive plantlets ranged between 10 % (cv. 'Penkelon' and 'CRBP 39') and 20 % (cv. 'Kelong Mekintu') and were reached for TPS (total produced shoots) values between 800 and 2000. Following this increase step, a steady state phase was observed. Then the percentage of BSV-Ol positive plantlets decreased for the three cultivars studied when increasing the number of subcultures. This was especially striking for CRBP 39 hybrid, for which values of zero (i.e below the sensitivity threshold of detection tests) were reached from TPS values of 4000 onwards although the decrease was less pronounced for the two other cultivars studied. These results will be presented and their outcome for in vitro mass propagation and diffusion of #Musa# germplasm will be discussed (Texte intégral).

La vanille est le premier arôme naturel produit et consommé au monde, et pourtant la diversité génétique du vanillier reste très mal connue. En raison des enjeux économiques et politiques que la vanille naturelle représente pour de nombreux pays du Sud (Madagascar, Comores, Polynésie, et plus récemment en Inde, Nouvelle Guinée, Mexique et Chine), seul le Cirad a l'expérience et les moyens de conduire une prospection et de constituer une collection mondiale de vanilliers. L'objectif est d'établir les caractéristiques morphologiques, agronomiques, biochimiques et moléculaires de cette collection dans des conditions de certification sanitaire et de production réelle. Un double in vitro doit permettre de conserver à l'abri, de multiplier et de diffuser du matériel sain caractérisé et certifié. La comparaison entre espèces et variétés, rendue possible par la culture dans des conditions similaires, donnera des indications sur la sensibilité aux agresseurs, sur les performances agronomiques ou aromatiques, permettra d'améliorer les méthodes culturales ou technologiques à bon escient, et d'envisager des programmes de sélection et d'amélioration. En répondant aux demandes ponctuelles extérieures des 15 dernières années, le Cirad a nettement renforcé son expertise et les méthodes d'analyse et diagnostic dans trois domaines: agronomie, protection de la plante et post-récolte. Le projet de description de la diversité génétique des vanilliers s'appuie sur ce savoir-faire acquis sur la filière et pourrait aisément déboucher sur des valorisations en répondant aux questions couramment posées: quel est le rôle de la génétique dans la production de vanilline ? Tous les vanilliers sont-ils sensibles aux mêmes virus ? La déhiscence de la gousse a-telle un déterminisme génétique ou environnemental ? Le Cirad, avec l'appui de partenaires, souhaite redynamiser la filière vanille en comblant certaines "lacunes" en travaillant en particulier sur 1. la mise en place d'un centre de ressources génétiques visant à faire de la caractérisation génétique, du diagnostic sanitaire, et des comparaisons multiparamétriques, 2. les problèmes phytosanitaires (viroses, mycoses, ravageurs...) et la recherche de résistances, 3. le montage d'un centre de transit ou de multiplication de boutures certifiées, Le Cirad souhaite s'impliquer dans ce sens en Polynésie française, à La Réunion, en Guadeloupe et à Madagascar, car ces îles possèdent des avantages complémentaires: culture, climat, biodiversité, savoir-faire, image de marque, potentiels de production de gousses, de plants certifiés ou de produits transformés.

L'ail (Allium sativum L.) est une espèce importante et largement cultivée et consommée dans le monde comme condiment et pour ses propriétés pharmaceutiques en particulier ses activités antibiotique, antitumorale, antiathériosclérotique et préventive des maladies cardio-vasculaires. Les variétés commerciales présentes sont toutes sexuellement stériles et sont propagées exclusivement par voie végétative. Ceci entraîne un faible taux de multiplication au champ, des possibilités réduites d'amélioration génétique et de fortes contraintes sanitaires. En effet, toutes les populations d'ail sont à l'origine infectées par un complexe de virus, parmi lesquels deux potyvirus (OYDV et LYSV) sont les plus répandus et les plus destructeurs. Chacun de ces virus peut réduire les rendements de 20 à 60%, et jusqu'à 80% dans les cas d'infections mixtes, en fonction du type variétal et du stade de l'infection. Pour apporter solution à ce problème des méthodes pour obtenir un fort taux de multiplication de variétés débarrassées de virus ont été conçues. Le micro bouturage in vitro a été utilisé pendant des années en utilisant des cultures de méristèmes apicaux pour l'élimination des virus et la production de matériel sain. Plusieurs protocoles ont été publiés et proposés pour l'amélioration des performances de cette technique de micro-propagation. Cependant le taux de multiplication obtenu reste relativement faible. D'autres méthodes ont été rapportées et concernent en particulier la régénération de plantes au travers de l'organogénèse et de l'embryogénèse somatique. La production, la culture de cals et la régénération de ces derniers ont été réalisées à partir d'explants tirés de diverses parties de la plante (plateau basal, apex méristématique, primordium foliaire et racines). Cependant, ces techniques non plus, en l'état de leur développement, n'ont pas fourni des taux de multiplication suffisants. Il faut aussi remarquer que l'origine somatique de l'embryogénèse n'a encore pas été prouvée. Nous avons cherché à développer une méthode: - permettant la propagation de masse de plants et par conséquent réduisant le nombre de cycles de multiplication et la diminution des risques de ré-infestation du matériel par des maladies, - ouvrant des voies d'amélioration génétique de l'ail permettant en particulier l'application de la fusion de protoplastes et des techniques de transformation génétique. Cette méthode a été réalisée par: - la mise au point de l'embryogénèse somatique prouvée par suivi histologique des tissus - l'établissement de cultures de suspensions cellulaires à partir de tissus embryogènes. La régénération de ces dernières pouvant mener à la production de masse de plants ou de nouveaux matériels génétiques après transgénèse ou moutagénèse.

Destiné à tous ceux qui s'intéressent à la production de plants forestiers, cet ouvrage présente, pour 59 espèces d'arbres et arbustes indigènes(1) ou endémiques(2) de La Réunion, l'itinéraire technique à suivre depuis la récolte des semences jusqu'à l'obtention en pépinière d'un matériel bon à planter. L'ouvrage repose sur les résultats d'expérimentations menées par le Cirad-forêt durant ces dix dernières années, tant dans le domaine de la manipulation des semences que dans celui de l'écologie de la germination. Mais il résulte également de la précieuse coopération des pépiniéristes de l'Office National des Forêts de La Réunion, sans qui les aspects liés à l'élevage des plants de bon nombre d'espèces présentées ici n'auraient pu être développés.

Senecio inaequidens# D.C., an Asteraceae from Sout-Africa, is a successful invasive species in Europe. In the South of France it is a real problem in pastures where the plant may grow abundantly, while it is toxic for the cattle. This pluriannual species spreads rapidly through its numerous seeds and is able to colonize any distributed area. As alkaloids produced by #Senecio# are known to accumulate in roots (Hartmann, 1994), their potential effect was tested in order to evaluate if allelopathy is a component of #Senecio# ability to invade those areas [Authors' introduction].

Somatic hybridization allows the creation of new patterns of nuclear, mitochondrial and chloroplastic association. It is therefore necessary to master cytoplasmic molecular markers to determine the genetic origin of both organelles of plantlets obtained from protoplasts fusion. In the case of Citrus and related genera, only southern blot hybridization and restriction fragment-length polymorphism (RFLP) techniques were used for this task until now. Here, we describe the use in the Aurantioideae subfamily, of a simple and non labeling cleaved amplified polymorphic sequence (CAPS) technique, to determine the cytoplasmic genome origin of intergeneric somatic hybrids. Mitochondrial and chloroplastic universal primers previously selected for population genetic studies in Quercus by Demesure et al. (1995) are used with some modifications. The variability of cytoplasmic genome among somatic fusion partners is detected by coupling amplification and restriction reactions. Digested DNA fragments are analyzed by agarose gel electrophoresis (PCR-RFLP). This technique has been applied for the analysis of the cytoplasmic constitution of somatic hybrids arising from intergeneric, intersubtribal and intertribal combinations. Systematic transmission of the mitochondria from protoplasts isolated from embryogenic callus parents was confirmed.

Le programme de recherche en horticulture florale, en Guadeloupe comme en Martinique est centré en priorité sur l'introduction de nouvelles espèces et variétés ornementales. Les producteurs des Antilles françaises cultivent depuis plus de 20 ans une vingtaine d'espèces et variétés florales et la "collection mondiale" offre infiniment plus de possibilités. De nouvelles plantes sont collectées en régions tropicales, puis transférées en quarantaine à Montpellier, afin de subir les indexations nécessaires, selon un schéma précis. Les individus sont ensuite multipliés pour la production de plants sains, à destination des producteurs pépiniéristes. Le travail de recherche consiste essentiellement à "installer" in vitro les nouvelles espèces et variétés appartenant aux familles sélectionnées pour compléter la gamme des fleurs et plantes actuelle. Il s'agit de mettre au point des techniques de mise en culture, de multiplication végétative et de sevrage du matériel végétal. Plus de 80 espèces et variétés ont pu déjà être ainsi proposées aux floriculteurs. Le dispositif du CIRAD Guadeloupe, récemment mis en place, accueille les plants issus de quarantaine et assure la production de vitroplants certifiés indemnes de maladies. La demande en plants sains ornementaux ne se limite pas à la Martinique ou à la Guadeloupe. Certains pays producteurs de fleurs ont déjà manifesté leur intérêt pour l'acquisition de plantes nouvelles, ce qui permettrait au programme fleurs Martinique-Guadeloupe d'avoir une portée internationale.

Ce document passe en revue les techniques de culture in vitro adaptées aux conditions tropicales :1- Aspects fondamentaux de la culture in vitro. 2- Partie expérimentale. Installation d'un laboratoire de culture in vitro en conditions tropicales : choix du site, superficie du laboratoire et agencement intérieur, choix des équipements. Gestion du laboratoire : ressources humaines, formation et gestion du personnel, consommables, qualité du matériel végétal " source ". 3- Protocole expérimental. Etude de cas n°1 : culture in vitro du teck. Etude de cas n°2 : culture in vitro du bananier (Musa sp.) : aspects fondamentaux, la multiplication in vitro du bananier (matériel végétal, équipement et matériel expérimental, milieux de culture, préparation des solutions-mères, régulateurs de croissance, préparation des milieux), protocole expérimental : méthode de micropropagation (étape d'initiation des cultures, étape de prolifération, étape d'allongement et d'enracinement des tigelles, transfert et croissance des vitroplants en pépinière, sevrage " artisanal " des vitroplants de bananier). Une liste de de fournisseurs en France complète ce document