Search

There is a need for more diverse bananas with far more diverse genetic backgrounds which meet specific objectives such as fresh fruit, cooking bananas or varieties dedicated to processing. This chapter shows how diversification objectives can be achieved by taking into account sexual reproductive barriers. The objective is to produce large populations of hybrids to facilitate selection of genotypes with combinations of the right characteristics.

Like many vegetatively propagated crops, most cultivated bananas are highlyheterozygous polyploids of mono or interspecific constitution. During humanselection for edibility over thousands of years, Musa cultivars developed a particularlyhigh level of male and female gamete sterility associated with a low fertilizingpotential making genetic recombination through meiosis and hybridization rareevents during domestication. Recent evolutionary studies in Musa suggest that only afew hybridization events occurred from the wild seedy primitive ancestors to the mostevolved present day cultivars. Unlike other crops, in such a context where the speciescomplex is nearly fixed, banana breeding relies on strategies where an extremelylimited number of crosses are possible. Several genomic tools are now being used todecipher the complexity of the Musa genepool. Molecular markers can distinguishbetween genotypes and have provided a dear understanding of banana domesticationsuggesting only a few hybridization events from the wild seedy primitive to thepresent day cultivars. This allows us to build breeding schemes mimicking thesequence of crossings and selections that occurred over several millennia. The Musagenome can now be explored for desirable genes and subsequent marker-assistedselection. For banana improvement, this approach is particularly important in abiological context of gamete sterility (and difficulties to get large quantities of seeds) for which recombination and implementation of introgression strategies remain thegreatest challenge. (Resume d'auteur)

The Global Strategy for the Conservation and Use of Musa Genetic Resources (hereafter referred to as the ‘Global Strategy’) has been expanded in 2016 by Musa genetic resources and breeding experts within the framework of the Global Musa Genetic Resources Network, MusaNet. MusaNet’s mandate is to oversee the further development and monitoring of the implementation of the Global Strategy. The updated Global Strategy aims to provide a clear framework and roadmap to be used by the Musa community for the efficient and effective conservation of the globally important collections of Musa and to strengthen the utilization of the genetic resources toward an increased use of available diversity. It includes recommendations and priorities indicated in several consultation processes following the 2006 Global Musa Strategy and particularly the expertise and key groups represented, including the Regional Research Networks (BAPNET, BARNESA, Innovate Plantain and MusaLAC) and global networks such as ProMusa. The Global Strategy covers numerous topics dealing with Musa genetic resources, with the 12 chapters divided into four main parts: Diversity, Identity, Management and Use. Each chapter contains the sections titled Where we are now, Where do we want to go and How will we get there. For Musa researchers, including taxonomists and breeders, but also end users such as farmers, decisions on the management of banana diversity are often made with limited information. With this in mind, the Global Strategy is a core reference on the taxonomy, characterization, evaluation and genetic improvement of cultivars, leading to actions such as the selection of new and improved cultivars. The use of a more diverse genepool can lead to higher production while at the same time promote ecosystem services such as resilience to pest and disease and the effects of climate change.

Agricultural production and supply chains are facing major challenges in the form of increasing demand for food products, a diversified use of agricultural products including for non-food purposes, ecologically intensive agriculture, and the necessity of taking climate change into account. The creation and adoption of new varieties that are productive, diversified, better adapted, and more environmentally friendly can help cropping systems that seek to address these issues become more efficient. Plant breeding efforts must anticipate the needs of the end users and adapt to very different agri-chains, illustrated in this chapter by two examples: first, an agri-chain that is highly structured around targeted export products, for example, the dessert banana, which requires ideotypes that meet the requirements of production and marketing systems; and second, an emerging agri-chain for multi-use sorghum, characterized by new production objectives of increased energy potential and production of biomaterials, sometimes without compromising with the requirement of high grain yields. To meet the objectives and the sustainability of agri-chains, research into genetic improvement must propose new approaches, new tools, and innovative breeding methods. The objectives, and sometimes the entire breeding process, are shared with all the actors, especially the end users, as part of an enhanced partnership within agri-chains. The breeding strategy also depends on ease of access, better use of available and useful genetic resources, in-depth knowledge of the structure and diversity of these resources, genetic determinism of desirable traits, and pre-breeding approaches. All these scientific and partnership innovations ensure the necessary responsiveness to support the execution of current breeding processes and the identification of new varieties that meet current and future uses and services.

The release of new sweet-acid banana cultivars resistant to black leaf streak, Sigatoka leaf spot and Fusarium wilt is important for domestic markets in tropical and subtropical countries. Common current breeding strategies consist of selecting tetraploid AAAB hybrids directly from crosses between AAB sweet-acid cultivars pollinated with AA clones carrying disease-resistance genes. However, this crossing pathway is hampered by low gamete fertility and the rare occurrence of desired 2N gametes on the AAB female side (N=3X=33 chromosomes). We propose an alternative pathway which aims to create new triploid hybrids directly from AB landraces. Natural AB clones are sterile but their AABB tetraploid counterparts obtained by colchicine treatment are fertile. This gamete fertility was made profitable in crosses with AA and BB accessions to generate AAB and ABB hybrids. We present here agronomical results of various progenies involving an in vitro synthesized tetraploid 'Kunnan' (AABB) and several AA and BB clones. These first results suggest the very high potential of this new strategy for the release of wellperforming new hybrids combining higher productivity, disease resistance and better fruit quality. Hybrids with a high added-value, produced in this way, could be made available for evaluation within the ProMusa network. (Resume d'auteur)

Original multidisciplinary research hereby clarifies the complex geodomestication pathways that generated the vast range of banana cultivars (cvs). Genetic analyses identify the wild ancestors of modern-day cvs and elucidate several key stages of domestication for different cv groups. Archaeology and linguistics shed light on the historical roles of people in the movement and cultivation of bananas from New Guinea to West Africa during the Holocene. The historical reconstruction of domestication processes is essential for breeding programs seeking to diversify and improve banana cvs for the future.

Introduction . A l’instar d’autres secteurs de produits destines a l’alimentation humaine, une restructuration profonde de la filiere ananas martiniquaise s’accomplit pour repondre a de nouvelles exigences de securite alimentaire et de protection de l’environnement : management de la qualite sur l’ensemble de la filiere et exploitation de nouvelles varietes d’ananas. A partir de l’analyse des pratiques actuelles, les auteurs ont evalue les besoins de changements, puis propose quelques outils pour la mise en œuvre d’un systeme de production. Materiel et methodes . Des enquetes ont permis de connaitre les pratiques et strategies actuelles des producteurs d’ananas et d’etablir une typologie des exploitations. Un comite de pilotage associant des representants de l’ensemble de la filiere elabore le systeme de management de la qualite en se basant sur la norme Agriconfiance®. De nouvelles varietes sont en cours d’evaluation pour couvrir au mieux les besoins en ananas de qualite pour la transformation ou pour la vente en frais. Resultats et discussion . Les ecarts constates entre recommandations et pratiques culturales sont apparus tres variables mais souvent importants : trop d’intrants en general, soit les pesticides, soit les engrais, soit les deux. Le systeme de management applique repose sur un contrat entre une cooperative et les producteurs. Les regles de qualite sont fixees dans deux cahiers des charges, l’un concernant la qualite de la production au champ, l’autre, la qualite du fruit pour l’usine. Un systeme de tracabilite a l’echelle de la parcelle a ete elabore. Il permet la prevision et l’enregistrement de toute activite liee a la production, avec la parcelle comme unite de base. Enfin, de nouvelles varietes hybrides selectionnees par le Cirad ont pu etre testees dans le nouveau processus de transformation de la cooperative, donnant de meilleurs resultats que l’ancienne variete Cayenne lisse. Conclusion . La restructuration de la filiere ananas en Martinique resulte avant tout de considerations economiques. Cette demarche a conduit au developpement d’un programme global d’assurance qualite, avec instauration d’un systeme de tracabilite parcellaire, destine a garantir la securite alimentaire. Une homogeneisation des pratiques culturales est necessaire, en se rapprochant des recommandations pour ameliorer la qualite. Elles pourraient etre rassemblees dans un guide de culture specifique. L’adoption de nouvelles varietes d’ananas permettant d’obtenir de meilleurs rendements de transformation ainsi qu’une qualite accrue du produit frais ou transforme sera aussi un element determinant du succes de la demarche.

The study of the #Musaceae#, excitingly complex in the late 1800s, profited well from the taxo-morphologic inventory system developed b British scientists in a twenty year effort to coherently classify wild type species and cultivars. This system still holds true under the analytic fire of the actual, modern, molecular markers. These markers are best known under their acronyms : AFLP, CAPS, RAPD, RFLP, SCAR, SSR, VNTR to name the most described ones. The present communication is an overview on molecular markers as applied to #Musa# genetic diversity studies and mapping at CIRAD from 1987 to 1997. Marker systems from polyphenols and isozymes to microsatellites, as well a SINE and LINE-like repetitive elements, will be discussed. Especially aspects of transferability in order to foster cooperation and exchange between "biotechnology centers" and "biodiversity centers" worlwide will be mentioned. On focus will be on RFLP and microsatellite genetic diversity studies, based on the nucleic, mitochondrial and chloroplast genomes. The molecular data will soon be accessible over the Internet in TROPGENE-DB (a molecular biology database on tropical crops at CIRAD of the ACeDB algorithm family). (Resume d'auteur)

Les marqueurs RFLP ont été utilisés pour étudier la transmission de l'ADN cytoplasmique dans les croisements entre bananiers diploïdes. Les descendances de 2 croisements contrôlés ont été étudiées à l'aide de sondes cytoplasmiques hétérologues. Cette analyse met en évidence un biais important en faveur d'une transmission maternelle de l'ADN chloroplastique et paternelle de l'ADN mitochondrial. Ces résultats suggèrent l'existence de 2 mécanismes séparés de transmission et de sélection des organelles. Aucun modèle n'est proposé pour l'instant. La connaissance du mode de transmission des organelles constitue un point important pour les analyses physiologiques chez les bananiers et peut fournir un outil puissant pour confirmer les origines hybrides.

For several years, CIRAD (Centre de cooperation internationale en recherche agronomique pour le developpement) has invested in the genetic improvement of banana and plantain (Musa spp.) with the goal to make production, both for export trade and local consumption, more environmentally sustainable. A crossing strategy was developed to obtain triploid hybrid varieties directly from diploid plant material. Molecular tools have now been developed to support this conventional cross-breeding scheme. Molecular markers have given new insight in Musa genetic diversity, leading to a better understanding of the relationships between modern cultivars and their ancestors, thereby providing critical information for the choice of parent material. The Musa genome structure and genetic maps have been Investigated, clarifying the mating behaviour of gametes during meiosis and giving Insight in how to manage ploidy and interspecificity. Genes involved in character expression have been identified, and genome sequencing is ongoing as a result of an International effort. The development of these molecular tools provides breeders with important information to increase the efficiency of genetic improvement efforts. This paper presents how the molecular approach is actually implemented in CIRAD's breeding strategy. (Resume d'auteur)

Pineapple internal browning (IB) is a chilling injury that produces enzymatic browning associated with flesh translucency. Pineapple biodiversity allowed the investigation of how polyphenol oxidase (PPO) and peroxidase (POD) activities with their different isoforms are involved in the IB mechanism. Fruits of four varieties that expressed IB symptoms differently, Smooth Cayenne (SCay) and the hybrids MD2, Flhoran 41 (Flh 41), and Flhoran 53 (Flh 53), were stressed by cold. The susceptible varieties showed classical brown spots but different patterns of IB, whereas MD2 and controls showed no IB. Enzymatic activities were measured on fruit protein extracts and PPO and POD isoforms separated on mini-gels (PhastSystem). Only PPO activity was significantly enhanced in the presence of IB. Up to six PPO isoforms were identified in the susceptible varieties. PPO was barely detectable in the nonsusceptible variety MD2 and in controls. The number of PPO isoforms and the total PPO activity after chilling are varietal characteristics.

World production of bananas, estimated at 106 million tons (Lescot 2006), ranks fourth in agricultural production. Bananas make up the largest production of fruits and the largest international trade, more than apple, orange, grape and melon. Bananas are cultivated in more than 120 countries in tropical and subtropical zones on 5 continents. Banana products represent an essential food resource and have an important socioeconomic and ecological role. Current varieties are generally seedless triploid clones either of the single genome A from the species Musa acuminata (group AAA) or of both genomes A and B from species M. acuminata and Musa balbisiana (groups AAB and ABB). More rarely, diploid varieties (AA and AB) and tetraploid clones are encountered. There are two major channels of banana production: those cultivated for export and those reserved for local markets. The main banana varieties cultivated for export, known as ‘Grande Naine’, ‘Poyo’ and ‘Williams’, belong to the monospecific triploid bananas (AAA) of the Cavendish sub-group. They differ from each other only in somatic mutations such as plant height or bunch and fruit shape. Their production relies on an intensive monoculture of the agro-industrial type, without rotation, and a high quantity of inputs. Banana cultivation for local consumption is based on a large number of varieties adapted to different conditions of production as well as the varied uses and tastes of consumers. Diploid bananas, close to the ancestral wild forms, are still cultivated in Southeast Asia. In other regions, triploid clones belonging to different sub-groups – Plantain, Silk, Lujugira, Gros Michel, Pisang Awak – are the most widely distributed. Bananas have many uses. They are not only consumed as fresh fruits but also cooked, like plantains. They are processed in various ways, into chips, fries, fritters

Banana hybrids with resistance to Yellow Sigatoka and Black Leaf Streak disease were evaluated for resistance to the burrowing nematode Radopholus similis and to the lesion nematode Pratylenchus coffeae in a growth chamber at 24–28°. Plants produced by tissue culture were acclimatised for 6 weeks prior to inoculation. Forty-five days after inoculation with nematodes, the root systems were processed and nematode numbers assessed. Two cultivars of Grande Naine (Musa AAA, Cavendish subgroup, ITC1256 and cv902) and one cultivar of Yangambi Km5 (Musa AAA, Ibota subgroup, ITC1123) were used respectively as susceptible and resistant controls. Results based on multiplication rates and root infestations showed that three of these hybrids (FB918, FB919 and FB924) were not significantly different from the resistant control Yangambi Km5 with a lower multiplication of R. similis. Similarly four of these hybrids (FB918, FB919, FB920, FB924) showed a lower multiplication of P. coffeae, not significantly different from the same resistant control. This is the first study that shows a partial resistance to both nematode species, R. similis and P. coffeae within synthetic hybrids of M. acuminata, adding an important extra value to these dessert banana hybrids formerly bred to resist to Mycosphaerella leaf spot diseases.

CIRAD pineapple genebank was established in Martinique in 1985 and now rise above 600 accessions. Considerable data - origin, botanical description, agronomic behaviour - have been collected. In year 2000, the development of a user-friendly database was undertaken. Within the database, each accession is documented according to the IPGRI plant descriptors: Passport, Characterization, Evaluation and Management descriptors. In addition, a set of indicators gives information about data reliability and representativeness. The database is intended for the use of researchers in charge of the genebank and for genetic resources endusers working in genetics, breeding, development or training. Through the user interface, curators have access to data input and management frames. End users can consult the database through several pre-set forms: rough or extended list of germplasm, accession data sheets illustrated with photographs. Any other kind of queries can be developed with Microsoft Access software. The development of standardized data frames allows information exchange with other databases. (Resume d'auteur)

Author for correspondence e-mail: raboin@cirad.fr; International audience; The origin of triploid export banana cultivars was investigated. They all belong to Cavendish and Gros Michel subgroups of triploid clones and have a monospecific Musa acuminata origin. The appearance of these cultivars is thought to be result of hybridization between partially sterile diploid cultivars producing non reduced gametes and fertile diploids producing normal haploid gametes. To trace these diploid ancestors we compared the RFLP patterns, revealed by 36 probe/enzyme combinations, of 176 diploid clones representing the worldwide available variability with that of clones from the Cavendish and Gros Michel subgroups. This lead us to the identification of the common putative diploid ancestor of cultivars from Cavendish and Gros Michel subgroups which contributed to triploid cultivar formation through the production of 2n restitution gametes. For cultivars of Gros Michel subgroup we also propose a normal gamete donor that may have complemented the triploid allele set

In banana, the maternal transmission of chloroplast DNA and paternal transmission of the mitochondrial DNA provides an exceptional opportunity for studying the maternal and paternal lineage of clones. In the present study, RFLP combined with hybridization of heterologous mitochondrial and chloroplastic probes have been used to characterize 71 wild accessions and 131 diploid and 103 triploid cultivated clones. In additon to Musa acuminata and Musa balbisiana, other species from the four Musa sections were studied to investigate their contribution to the origin of cultivated bananas. These molecular analyses enable the classification of the Musa complex to be discussed. Results ascertain relationships among and between the wild accessions and the mono- and interspecific diploid and triploid bananas, particularly for the acuminata genome. Parthenocarpic varieties are shown to be linked to M. acuminata banksii and M. acuminata errans, thus suggesting that the first center of domestication was in the Philippines - New Guinea area. Resume : Chez le bananier, la transmission maternelle de l'ADN chloroplastique et paternelle de l'ADN mitochondrial offre la possibilite d'etudier les filiations maternelles et paternelles entre clones. Cette etude RFLP a l'aide de sondes heterologues mitochondriales et chloroplastiques a permis de caracteriser les genomes cytoplasmiques de 71 accessions sauvages, 131 bananiers cultives diploides et 103 triploides. En plus des bananiers sauvages Musa acuminata et M. balbisiana, d'autres especes des 4 sections du genre Musa ont ete etudiees pour evaluer leur contribution a l'origine des bananiers cultives. La classification du complexe Musa est ici discutee. Ces resultats permettent d'etablir des apparentements entre les bananiers sauvages, et les cultivars diploides et triploides mono ou inter-specifiques en particulier au sein du genome acuminata. Il est montre que les varietes parthenocarpiques sont apparentes a M. acuminata banksii et M. acu- minata errans et donc suggerent un centre de domestication primaire du bananier dans la zone Philippines - Nouvelle Guinee. Mots cles : Musa, RFLP, ADNcp, ADNmt, filiation.

Ce document fait le point sur l'utilisation de la diversite genetique dans le genre #Musa#. Divers themes sont abordes : importance des #Musa#, ressources genetiques du genre #Musa# (especes sauvages et cultivees), possibilites et contraintes d'acces a la diversite pour l'amelioration, utilisations (disponibilite en ressources genetiques, introduction de materiel genetique, utilisation des ressources genetiques en amelioration, applications des biotechnologies en amelioration, transformation genetique), extension de la diversite utilisee par les programmes d'amelioration des #Musa# (amelioration conventionnelle, selection de varietes resistantes, amelioration par mutagenese et variations somaclonales, possibilites d'hybridation decentralisee), la diversite et les petits planteurs, le role des reseaux (reseaux au niveau global, regional ou national)

Nuclear genome size variation was studied in #Musa acuminata# (A genome), #Musa balbisiana# (B genome) and a range of triploid clones differing in genomic constitution (i.e. the relative number of A and B genomes). Nuclear DNA content was estimated by flow cytometry of nuclei stained by propidium iodide. The A and B genomes of #Musa# differ in size, the B genome being smaller by 12% on average. No variation in genome size was found among the accessions of #M. balbisiana# (average genome size 537 Mbp). Small, but statistically significant, variation was found among the subspecies and clones of #M. acuminata# (ranging from 591 to 615 Mbp). This difference may relate to the geographical origin of the individual accessions. Larger variation in genome size (8.8%) was found among the triploid #Musa# accessions (ranging from 559 to 613 Mbp). This variation may be due to different genomic constitutions as well as to differences in the size of their A genomes. It is proposed that a comparative analysis of genome size in diploids and triploids may be helpful in identifying putative diploid progenitors of cultivated triploid #Musa# clones. Statistical analysis of data on genome size resulted in a grouping which agreed fairly well with the generally accepted taxonomic classification of #Musa#.

Le genre #Musa# appartient a la famille des Musaceae. Les principaux cultivars de bananiers comestibles proviennent du croisement entre #Musa balbisiana# et #Musa acuminata#. La section #Australimusa# est la plus importante comme ressource genetique pour la production de fibres textiles (abaca). Originaire de l'Asie du Sud-Est, les bananiers sont actuellement repartis dans la zone intertropicale ; en Afrique et en Amerique. Dans toutes les zones geographiques, les mutations somatiques ont introduit une importante biodiversite genetique et phenotypique. Des programmes de conservation du germplasm et de la biodiversite ont ete inities depuis le seminaire organise en Belgique en 1989. Ils visent a collecter et a stocker le genome des diverses varietes de bananiers partout dans le monde (Amerique latine et Caraibes, Afrique centrale, Afrique de l'Est, Afrique de l'Ouest, Asie du Sud-Est et Pacifique) sous la coordination de l'INIBAP. D'autres programmes de recherche ont ete conduits sur l'amelioration des performances culturales et la resistance contre les organismes nuisibles et les maladies a l'aide des biotechnologies

La majorite des bananiers cultives sont triploides. Importants en selection, les bananiers diploides sont analyses pour la comprehension de l'organisation genetique du complexe d'especes Musa. A l'aide de 30 sondes uniques nucleaires cartographiees, le polymorphisme de longueur de fragments de restriction (RFLP) est utilise pour analyser la diversite genetique de 160 varietes de bananiers diploides : 70 clones seminiferes (sauvages) appartenant aux especes Musa acuminata, M. balbisiana et M. schizocarpa et 90 varietes parthenocarpiques (cultivars). Des alleles specifiques a chacune des 3 especes ont ete trouves. M. acuminata est l'espece la plus polymorphe; sa structuration est discutee. Il est montre que M. schizocarpa est relativement proche de M. acuminata banksii, M. balbisiana se revelant beaucoup plus eloignee. Tous les diploides parthenocarpiques presentent des alleles M. acuminata, confirmant le role de cette espece dans l'origine de la parthenocarpie. L'existence de cultivars hybrides M. acuminata par M. schizocarpa est demontree. (Resume d'auteur)

Une carte moléculaire partielle du génome du bananier diploïde Musa acuminata est présentée. Cette carte est basée sur 58 marqueurs RFLP, 4 marqueurs isozymes et 28 marqueurs RAPD, marqueurs ségrégeant dans une population F2 (SF265 (cv. Musa acuminata) x Musa acuminata ssp. banksii) de 92 individus. Un total de 90 loci a été détecté dont 77 étaient dans 15 groupes de liaison tandis que 13 ségrégeaient indépendamment. Des distortions de ségrégation ont été montrées par 36% des loci souvent favorisées par le parent mâle. Les réarrangements structuraux du chromosome étaient supposés être une des principales causes de ces distortions. Discussion sur l'utilisation des données sur les liaisons génétiques pour mieux connaître la génétique et l'évolution du genre Musa et comme aide aux programmes d'amélioration et de sélection

Deciphering the diversity of the banana complex needs a joint characterization and analysis of the original wild species and their relatives, primitive diploid forms and triploid derived varieties. Sexuality, the primary source of diversity, is strongly disrupted in the cultivated varieties (sterility, parthenocarpy and vegetative propagation) by human selection of vegetatively maintained punctuated mutations. Many biological tools are available for characterizing this diversity, each one illustrating some peculiar facets, and we show that their joint analysis enables an evolutionary reading of this diversity. We propose various scenarios regarding the structure of wild species, on the domestication of the edible diploids from hybrids between wild forms, on the direct ancestry of triploids from cultivated diploids, and on the ancient migrations dispersing cultivated forms around the world. The comparison with data from archaeology, linguistics and human genetics will enable the validation, refinement and dating of the proposed domestication process.

An examination of bract anthocyanins in 59 banana varieties separated them into five main chemotypes, based upon the presence/absence of methylated compounds and/or the ratio between delphinidin and cyanidin derivatives. The data suggest the occurrence of two centres of domestication for the acuminata cultivars in southeast Asia; the origins of some hybrid cultivars are also discussed.