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Description du sujet. Pour la zone écologique du Moyen-Ouest des plateaux d’altitude de Madagascar, six variétés de riz pluvial ont été sélectionnées par un programme de recherche. Objectifs. Il s’agit d’évaluer leur potentiel de diffusion en milieu réel. Méthode. Elles ont été co-évaluées sur un réseau de 20 fermes de référence pendant deux années. Résultats. L’expérimentation multi-locale a montré une gamme variée d’environnements indiquée par le rendement grain moyen en riz entre 1,04 à 4,50 t·ha-1, dans laquelle FOFIFA 182 s’est montrée significativement supérieure (2,90 t·ha-1) et SCRID 195 largement inférieure (1,65 t·ha-1), avec un groupe de quatre variétés non différenciées (autour de 2,40 t·ha-1). L’étude de l’interaction génétique-environnement a permis de différencier une variété produisant moins bien en milieu peu fertile, SCRID 90, et une moins stable, SCRID 91. SCRID 195, la variété la moins performante en termes de rendement, s’est montrée également la plus infectée par Striga asiatica, une plante hémiparasite. L’évaluation réalisée par les agriculteurs au terme de ces deux années complète celle de la recherche concernant le rendement du riz et le Striga, leurs principaux critères de performances des variétés, associés à six autres critères secondaires concernant le battage, la précocité, la résistance à la sècheresse, la qualité de grain, le gout et le poids de grain. Conclusions. Cette co-évaluation recherche-agriculteurs a permis de définir les variétés les plus performantes en termes de rendement et de contrôle du Striga, à savoir NERICA 4 (déjà vulgarisée) et FOFIFA 182 (proposée à la vulgarisation), de préciser l’intérêt de nouvelles variétés pour d’autres critères retenus par les agriculteurs et comme perspectives, la nécessité d’intégrer une approche systèmes de culture et une dimension temporelle, en lien avec la performance du riz pluvial.

All over the world, sugarcane breeding programs are developing new, high-yielding cultivars that are resistant to major diseases to improve the profitability and sustainability of the sugar-energy industries they serve. In Reunion Island, sugarcane genetic improvement efforts began in 1929. Many challenges had to be overcome. Continuous breeding efforts have been made to develop varietal resistances to control some major diseases and are still going on today. Given the extreme agroclimatic diversity that characterizes the different production areas of the industry, it was necessary to gradually develop a large network of seven decentralized breeding programs to support genetic progress throughout the whole industry. This article provides an overview of the sugarcane breeding program of Reunion. It describes historical achievements and gives detailed information about germplasm development, variety exchanges, breeding program and selection scheme and procedures. A review is also made on applied genetics research activities supporting variety improvement. Further progress depends on the optimized functioning of the current breeding program, which has never been so largely extended in terms of target environments. The article discusses prospects of genomics breeding applications in the complex genetic context of sugarcane, which will require large multidisciplinary collaborations.

International audience; Enhancing rice yield in upland rice systems through genetic improvement remains a major challenge in the tropics. This review aims to provide the trends on upland rice cultivation over the last 30 years and recent distribution of upland rice in the tropics, and to report progress in studies on genetic improvement for enhancing productivity in Africa, Asia, and Latin America. While upland rice cultivation area has reduced in Asia and Latin America over the last 30 years, the area in Africa has increased. The current share of upland rice area in total rice area is related to rainfall and gross national income per capita, especially in Africa, and higher share is associated with lower rice self-sufficiency at national level. Breeding programs in Asia and Latin America have developed high-yielding varieties using indica materials as parents. In Africa, New Rice for Africa (NERICA) varieties were developed from crosses between improved tropical japonica and Oryza glaberrima. However, recent studies report that there is scope for improving existing NERICA using upland indica materials from Asia. In highlands of Africa, there are ongoing breeding programs using japonica varieties, such as the Nepalese Chhomrong Dhan. Key important plant traits used in the breeding programs are not largely different across regions, especially intermediate plant height and tillering capacity (which may be related to weed-suppressive ability), and high harvest index. In conclusion, we propose an international network for breeding upland rice with accelerating seed exchange across regions that could enhance upland rice productivity through genetic improvement.

National audience; Les derniers acquis de la recherche sur les mécanismes de la recombinaison génétique, lors de la méiose, ouvrent de nouvelles voies de sélection des caractères d’intérêts chez les plantes cultivées.

Panicum maximum est une graminee fourragere caracterisee par la coexistence sur une meme inflorescence de deux modes de reproduction : l'apomixie et la sexualite. Selectionneurs, multiplicateurs de semences et utilisateurs ont pour une meme raison, le rendement, tendance a n'employer qu'un nombre limite de varietes. Ceci aboutit rapidement a l'echelle d'un pays a une homogeneisation genetique. Chez une plante apomictique, l'homogeneite devient preponderante. Les possibilites d'adaptation a un changement des conditions exterieures sont alors limitees. L'etude des strategies adoptees par cette espece pour se maintenir et se diversifier dans des conditions aussi variables que celles qui regissent les ecosystemes tropicaux permet de cerner l'attitude que le selectionneur et l'utilisateur doivent prendre afin de minimiser les risques lors de son exploitation agronomique

Depuis des millénaires, les migrations de populations et les échanges de matériel végétal ont placé le bananier dans des contextes écologiques très différents sur tous les continents. Les agriculteurs ont su valoriser les mutations naturelles résultant de la multiplication végétative. C'est cette combinaison de la reproduction naturelle et des sélections faites par l'homme depuis la nuit des temps qui est à l'origine de la diversité génétique actuelle.

Taro [Colocasia esculenta (L.) Schott] is a root crop which is an important staple food in many regions of the world, producing 10.5 million tonnes on 1.4 million hectares a year. The crop is cultivated in wet (rain fed) or irrigated conditions, requiring on average 2,500 mm water per year, and in many countries it is cultivated in flooded plots. it is estimated that taro production could decrease by 40 % as a result of the increase in drought and other severe events. In this work, Thirty three accessions, including local cultivars, selected and hybrid lines were submitted to long duration drought stress and screened for tolerance. Twelve physiological, morphological and agronomic traits were measured at harvest, and subject to multivariate analysis. Stress indices, Water Use Efficiency and Factorial Analysis were useful for discriminating accessions regarding drought tolerance and yield stability, and drought tolerant and susceptible cultivars were identified. Our results confirm that different taro cultivars have different drought avoidance and tolerance strategies to cope with water scarcity. Better yield performers minimised biomass and canopy loss, while tolerance was observed in cultivars that presented low potential yield, but efficiently transferred resources to enhance corm formation. Among the 33 accessions, two local cultivars showed high yield stability and could be considered as suitable parents for breeding programs, while two others are well adapted to drought, but with overall low yield potential.

Kava (Piper methysticum) is a major cash crop in the Pacific. The aim of this study was to assess genetic variation among 103 accessions of kava using SSRs and DArTs. Genetic structure was determined using clustering analyses (WPGMA) and principal coordinate analyses (PCA). Thirteen SSR primers and 75 DArT markers were found polymorphic, and the two types of markers generated similar clustering patterns. Genetic distances ranged from 0 to 0.65 with an average of 0.24 using SSRs and from 0 to 0.64 with an average of 0.24 using DArT. Eleven genotypes were identified with SSR while 28 genotypes were identified with DArT markers. By combining the two sets of markers, a total of only 30 distinct genotypes were observed. In the Vanuatu archipelago, noble cultivars originating from different islands clustered together within a very narrow genetic base despite their diversity of morphotypes. SSR and DArT fingerprints allowed the identification of kava cultivars unsuitable for consumption, so called two-days, and clearly differentiated the wild types classified as P. methysticum var. wichmannii from the cultivars as var. methysticum. Molecular data reveals that all noble cultivars evolved by the predominance of clonal selection. Although they are represented by clearly distinct morphotypes, these cultivars are genetically vulnerable and their potential to adapt to forthcoming changes is limited. These newly developed markers provide high resolution and will be useful for kava diversity analyses and quality assessment.

China is one of the largest cotton producing countries in the world thanks to high yields, on which a variety registration system has mainly focused, so that a lack of quality is nowadays acknowledged as a weak point of the cotton industry in that country. The objective of this study was to check the hypothesis that bias in cultivar selection in favor of yield has been maintained through the application of an imperfect selection index (SI), but that a better outcome is possible. Our demonstration is based on an analysis of the data from ten years of cotton variety trials using genotype-by-trait biplots, implemented both for the cultivar selection index (SI) currently applied in China and for an adjusted selection index (ASI) that more effectively took into account the antagonism between yield and quality traits. The main findings were: 1) significant negative associations between yield and fiber quality hindered their simultaneous improvement; 2) registered genotypes were mainly determined by the SI which was primarily yield-oriented; 3) no progress in fiber quality was recorded unlike yield; 4) balanced progress in yield and quality is possible through an adjusted selection index (ASI) guided by genotype-by-trait biplot analysis.

Sorghum (Sorghum bicolor (L). Moench) is an important staple food crop produced essentially under rained conditions in Mali. To preserve and exploit sorghum genetic diversity, germplasm collection was undertaken in 1978 across Mali. During this germplasm evaluation in 1982, a particular guinea sorghum cultivar from Chegue village in north western Mali, recorded as CSM63, was identified for its earliness and photoperiod insensitivity. This cultivar was unfortunately segregating not only for a testa presence, which is detrimental to To color and nutritional quality, but also for flowering time and plant height. Field screening coupled with the potassium hydroxide and bleach (KOH: B) tests were performed to eliminate testa while maintaining CSM63 agronomic values. Overall objectives were to trace history of CSM63 native population, screen for testa absence and define its favorable cropping zone. Field experiments were conducted at the Cinzana Agronomic Research Station (SRAC) while laboratory tests for testa absence and cooking quality were conducted at Sotuba Food Technology Laboratory (LTA) in Mali. Two thousand (2000) plants from original CSM63 population were grown in a complete isolation from other sorghum varieties to select 288 panicles for testa absence. For yield trial, a completely randomized block design was used with 3 replications. After series of selfing, a pure new line (CSM63-18-1AF) was identified without a testa with similar maturity, grain yield, better To color and nutritional values than the original CSM63. The new line was named CSM63E and its cropping zones were delimited beyond its center of origin. CSM63E was released for large scale production by Institut d'Economie Rurale (IER) and registered in National and West African Countries Regional Sorghum Catalogs. The adopted line is named Jakunbe (prevent drought) in Bambara language) by farmers. Jakunbe is the number one certified sorghum seed produced in Mali in 2016 in term of quantity. Cropping both Jakunbe and late maturing varieties beyond isohyets 700 mm exposes farmers to yield losses caused by non-proper environment.

La banane dessert, qui est la première ressource agricole aux Antilles, doit faire face d'une part à une forte concurrence avec les pays d'Afrique et d'Amérique latine et d'autre part à une pression parasitaire importante, notamment due aux maladies foliaires des bananiers. Dans ce contexte, la création de variétés de banane dessert présentant une résistance aux principales maladies et ravageurs du bananier et de nouvelles caractéristiques de qualité sensorielle apparait comme une voie privilégiée pour accroître la viabilité et la durabilité de la filière. Dans le cadre du programme d'amélioration variétale de la banane dessert créé par le CIRAD et basé aux Antilles, mon rôle a été de contribuer à son efficience en participant à la production (1) de méthodes de phénotypage de la qualité sensorielle et des désordres physiologiques, (2) d'outils d'aide à la sélection variétale et (3) de connaissances sur l'élaboration de la qualité sensorielle du fruit. Pour cela, mon projet scientifique s'est articulé autour de deux axes de recherche. Le premier axe visait l'identification d'indicateurs pertinents de la qualité sensorielle de la banane dessert très peu abordée auparavant. Ces indicateurs ainsi que leur seuil d'acceptabilité ont été évalués à partir d'une gamme diversifiée de génotypes. Il a pu être démontré notamment l'importance des paramètres d'acidité dans l'expression de plusieurs descripteurs sensoriels (acide, sucré, certains arômes, fermeté). Le second axe de recherche visait à analyser l'impact du génotype et des pratiques culturales sur l'évolution des composés d'intérêt sensoriel et sur l'expression de désordres physiologiques de la banane. En s'appuyant à la fois sur la conduite d'expérimentations au champ et la construction de modèles statistiques ou mécanistes, des éléments ont été apportés sur les origines de la variabilité mesurée qu'elle soit génotypique ou liée aux conditions environnementales. Des outils sont maintenant disponibles pour prédire le potentiel de conservation, l'apparition de la frisure et l'acidité chez différents génotypes selon les conditions de culture. Concernant l'acidité, les modèles développés ont permis d'identifier les processus physiologiques clés qui pilotent ce critère. L'amélioration de la qualité sensorielle de la banane dessert est simulée à partir de scenarii mettant en avant une optimisation de la sélection variétale et des pratiques culturales. Mes perspectives scientifiques sont de poursuivre les travaux sur la compréhension des processus pilotant la qualité sensorielle des fruits mais cette fois-ci soumis à des itinéraires post-récolte (impliqués dans la conservation, la maturation, ou la transformation des fruits). Les travaux contribueront à (1) limiter les pertes et gaspillages des fruits par une optimisation de ces itinéraires, et (2) renforcer la sécurité alimentaire des pays du Sud en participant à l'identification de critères de sélection spécifiques aux usages alimentaires de ces pays.

International audience; Modern sugarcane cultivars (Saccharum spp., 2n = 100–130) are high polyploid, aneuploid and of interspecific origin. A major gene (Bru1) conferring resistance to brown rust, caused by the fungus Puccinia melanocephala, has been identified in cultivar R570. We analyzed 380 modern cultivars and breeding materials covering the worldwide diversity with 22 molecular markers genetically linked to Bru1 in R570 within a 8.2 cM segment. Our results revealed a strong LD in the Bru1 region and strong associations between most of the markers and rust resistance. Two PCR markers, that flank the Bru1-bearing segment, were found completely associated with one another and only in resistant clones representing efficient molecular diagnostic for Bru1. On this basis, Bru1 was inferred in 86 % of the 194 resistant sugarcane accessions, revealing that it constitutes the main source of brown rust resistance in modern cultivars. Bru1 PCR diagnostic markers should be particularly useful to identify cultivars with potentially alternative sources of resistance to diversify the basis of brown rust resistance in breeding programs.

The rice varieties IR64 and Jao Hom Nin (JHN) demonstrated a broad-spectrum resistance against the rice blast pathogens in Thailand. A genomic investigation unravelled many resistance genes residing on four genomic regions, chromosome 2 and 12 in IR64 and 1 and 11 in JHN. A cross between these varieties was made to combine resistance genes into a single genotype. Marker-assisted selection (MAS) was employed to identify F2 and F3 plants carrying a combination of four resistance QTLs in a homozygous fusion. Flanking markers RM212/RM319 and RM144/RM139 to blast resistant QTLs on chromosome 1 and 11 in JHN rice and tightly-linked markers RM208 and RM179 to blast resistant QTLs on chromosome 2 and 12 in IR64 rice variety were used for MAS. The stepwise MAS screening was brought in as a strategy to provide a cost-saving and minimum number of PCR performing to select resistant genotypes. F4 generation, lines carrying all resistant QTLs show a broader spectrum of resistance against 11 representatives of Thai blast pathogen isolates. (Resume d'auteur)

The CSPWD is the Ghanaian form of lethal yellowing disease (LYD) of coconut, caused by a phytoplasma and has been active in Ghana since 1932. The paper updates the results of screening trials conducted with 38 pure and hybrid coconut varieties since 1981. Although no variety was found totally resistant, a wide range of susceptibility level was observed: almost all SGD were still unaffected, while the local WAT had almost totally disappeared, additive values were calculated for the parental varieties and it was shown that, in the average, hybrids are slightly more susceptible than predicted by a purely additive model. According to this genetic model, the SGD × VTT hybrid will be appreciably less susceptible than the MYD × VTT currently being used for replanting devastated farms in Ghana. Our results tend to confirm the general trend that cultivars from the Pacific group (especially the Dwarfs) are less susceptible than the Indo-Atlantic cultivars. Proposals are made to adapt planting material to the risk level. Genetic control can only be efficient if it is considered as a link in a chain of control measures involving the choice of a proper planting site, good management and early eradication of diseased trees.

SUMMARYIn most cotton-growing regions of West and Central Africa where rainfed conditions prevail, cropping conditions are highly diversified since the crop is planted over an extended period. We studied production and development patterns in 10 cotton (Gossypium hirsutum) varieties to determine the most efficient strategies that could be transformed into breeding traits. Four trials were carried out between 2002 and 2003 in two cotton-growing areas in Benin to compare the 10 varieties at three stand densities and two planting dates. The parameters monitored were the mean first flower opening date (FF), effective flowering time (EFT), plant height at harvest (HH), height to node ratio (HNR), length of fruiting branch (LFB), number of vegetative branches (NVB) and average boll retention at the first position of the fruiting branches (RP1). We identified two ideotypes that yielded better than the others: (i) Mar 88-214 performed well under late planting–high stand density conditions and was characterized by low vegetative growth and early flowering onset, a short flowering period and low RP1; (ii) H 279-1 performed especially well under early planting–low stand density conditions and was characterized by high vegetative growth, late flowering, long EFT and high RP1. We propose a breeding strategy for both ideotypes based on seven indicators with high heritability (FF, HH, HNR, and LFB) or medium heritability (NVB, EFT, and RP1).

International audience; Ce numéro propose une relecture de la place de l’oléiculture dans l’histoire de l’Ouest méditerranéen et plus particulièrement le Maroc. L’olivier y est considéré comme un modèle des relations sociales et environnementales : la distribution de la diversité génétique, les flux de gènes entre oliviers et oléastres, ou l’équilibre entre les variétés locales et les variétés étrangères sont liés aux stratégies de conservation, de sélection, d’amélioration et aux stratégies de développement et de valorisation oléicoles. La question de l’impact de la sélection variétale et de la dynamique évolutive de l’olivier constitue un axe commun aux chercheurs engagés dans différentes disciplines (écologie, biologie, génétique, ethnobiologie, archéologie, archéobotanique, histoire, agronomie, socio-économie, économie politique internationale). Leurs travaux mettent en perspective différents facteurs déterminant les dynamiques variétales, environnementales et sociales. Au début, les contributions apportent de nouveaux éléments sur la manière d’analyser et d’interpréter la diversité variétale et l’évolution de l’oléiculture depuis la préhistoire à la période contemporaine. Puis les approches de la génétique et de l'histoire interrogent la dominance de la « Picholine marocaine ». L'origine de cette variété, les facteurs historiques de sa diffusion au Maroc, son impact sur les agroécosystèmes traditionnels et sur la conception des programmes de sélection génétique y sont analysés. Afin d’approfondir les dynamiques à l’œuvre dans la diversification variétale de l’olivier, les approches de la génétique, de la socio-économie et de l’ethnobotanique, analysent l’évolution des écosystèmes et des pratiques paysannes. L’angle de l’économie politique internationale et de la socio-économie interroge alors le rôle des opérateurs privés et des organismes publics dans la diffusion variétale, en se focalisant en particulier sur les pépinières et les appellations d’origine oléicoles. Enfin, les dernières contributions présentent de nouvelles approches pour l'étude de l’olivier au Maroc. Des résultats préliminaires sur la plasticité de l’olivier, sur les caractères anatomiques de son bois et sur les données relatives au pollen y sont restitués. L’ensemble de ce travail fournit des éléments de réponse nuancés sur les facteurs déterminant la diffusion variétale et la dynamique de la diversification de l’olivier. Il ouvre de nouvelles pistes de recherche sur les mesures permettant de mieux évaluer les adaptations aux changements environnementaux et sur le rôle des politiques économiques dans la diffusion variétale.

International audience; For grafted plants, salt stress tolerance of the aerial plant part is poorly documented. Thus, we developed a simple, fast and inexpensive method to identify tolerant genotypes. Twigs of 14 mandarin accessions that we previously analyzed as seedlings were cut in solution to prevent embolism and were then evaluated in salt stress condition for a week. Physiological parameters such as gas exchanges, leaf Cl- and Na+, as well as the presence of H2O2 and the activity of enzymes involved in ROS synthesis and detoxification processes were analyzed. One accession known to be tolerant as rootstock was shown to be sensitive with limited Cl- translocation from the solution to the shoot while sensitive accessions when grown as seedlings presented limited wilting symptoms and accumulated large leaf Cl- content. A model is proposed to explain the different strategies of the plant to cope with high toxic ion content. This method allows separation of the root compartment, where ion exclusion mechanisms may exist and have an impact on the salt stress tolerance of the whole plant. (C) 2015 Elsevier GmbH. All rights reserved.

Acceptability criteria in dessert banana were investigated to enable sensory qualities to be taken into account earlier in the assessment of new banana hybrids in a selection scheme. Twelve banana cultivars were characterized by sensory profiling and physical-chemical analyses at a defined eating stage. The 'right' levels of sourness, sweetness, firmness, mealiness, and banana aroma were evaluated by 214 consumers on the 'Just-About-Right' scale. Optimal acceptance of a banana means at the most 20% of consumers judged the banana to be e.g. 'too …' or 'not … enough'. The ideal banana received scores ranging between 6.1 and 6.7 for sweetness, between 2.8 and 3.3 for sourness, above 6.3 for banana aroma, between 3.7 and 4.7 for firmness and between 1.0 and 1.4 for mealiness on a discrete 0–9 scale, by titratable acidity of 5.5 meq 100 g−1, or a pH of 4.9, and a pulp puncture force between 1.9 and 2.4 N. Acceptability thresholds were calculated when a maximum of 33% of consumers judged bananas to be e.g. 'too …' or 'not … enough'. Screening new hybrids revealed the advantage of using an acceptability threshold of 33% of unsatisfied consumers as the first step, since after a hybrid has passed the acceptability threshold, crop management can be directed towards being as close as possible to the characteristics of the ideal banana. (Resume d'auteur)

To comply with the intensive industrial agriculture model of the Green Revolution, the modern plant breeding combines professionalized variety selection using germplasm conserved ex situ and commercial production of seeds. This model has been widely adopted in the North and very partially in the South because it is based on strong policies options and investments not tailored for developing countries. The Convention on Biological Diversity in 1992 offers an alternate approach to current varietal research with the raise of the concept of “agrobiodiversity” that promotes forms of agriculture able ensuring maintenance of genetic resources for the future. Using actual examples, this chapter illustrates advances in different plant breeding situations for crops predominantly cultivated by family farmers. In forest areas farmers are involved in the processes of creating and disseminating new varieties of coffee and cocoa while maintaining sustainable their agroforestry systems that give them advantages when price in international markets fluctuates. In dry areas with high population growth and weak agricultural production, emphasis is given to participatory breeding methods for traditional food crops which have high adaptation and multiple traditional uses, for example, sorghum in Africa and quinoa in Chile. Finally, this chapter discusses how research, through companion modeling, encourages local seed production systems, and promotes their development by enhancing knowledge exchanges between actors and creating new partnerships.

Arabica coffees (60 % of current world coffee production) are generally sold at considerably better prices than robustas on account of superior beverage quality. However, costs of production are much higher, mainly due to more stringent demands for soil and climatic conditions, crop management, primary processing and control of several pests and diseases including the potentially very destructive coffee leaf rust (CLR) and berry disease (CBD). Breeding for disease resistance in combination with vigour, productivity and quality started in the early 1920s in India, but especially in the second half of the 20th century comprehensive breeding programmes have been implemented in several other coffee producing countries. Many of the resulting CLR- and CBD + CLR-resistant cultivars (true-breeding lines and F1 hybrids) meet the required standards of profitable and sustainable crop production. Challenges of more recent date include limited access to additional genetic resources of Coffea arabica, breakdown of host resistance to CLR, aggravating insect pest problems and the increasingly negative impact of climate change on arabica coffee production worldwide. This review discusses prospects of breeding and disseminating next generation (hybrid) cultivars of arabica coffee for sustainable coffee production under changing conditions of diseases, pests and climate. International networking on coffee breeding will facilitate sharing of resources (financial, genetic) and scientific information, application of genomics-assisted selection technologies, and pre-breeding for specific characters. Breeding and multiplication of new cultivars well adapted to the local environment will continue to be carried out at national or regional levels. A tree crop like arabica coffee does not lend itself to centralized variety development and dissemination on a global scale.

Produire des variétés adaptées à une agriculture durable, en particulier plus résilientes face aux contraintes environnementales, représente un défi pour les généticiens. Dans le cas de la sécheresse, et sur la base d'une caractérisation du risque climatique, une approche pluridisciplinaire associant l'écophysiologie et la génétique peut permettre de définir des idéotypes variétaux combinant des caractères adaptatifs utilisables en sélection. La sélection pour une meilleure adaptation à la sécheresse s'appuie à la fois sur l'existence d'une diversité naturelle ou générée par hybridation et sur la mise en oeuvre de tests de criblages des caractères adaptatifs. Des exemples de programmes de recherche développés en partenariat par le Cirad sont présentés dans le cas de deux plantes tropicales, le cotonnier et l'arachide. Les atouts du sorgho africain liés à son caractère photopériodique sont évoqués. La valorisation de la diversité génétique passe par une exploration large au-delà des espèces cultivées mobilisant le pool génétique des espèces sauvages apparentées.

National audience

Le choix du matériel végétal pour le reboisement ou l’afforestation est essentiel pour assurer une bonne adaptation du peuplement aux conditions pédo-climatiques locales et atteindre un niveau de production et une qualité correspondants aux objectifs fixés. La première étape consiste généralement à explorer la diversité interspécifique avant de mettre en place un programme de sélection génétique dont l’objectif est de fournir régulièrement du matériel amélioré. Dans les landes de Gascogne, le choix s’est porté, au cours du XIXème siècle, sur le pin maritime puis un programme d’amélioration a été initié dans les années soixante à partir de la provenance locale. L’utilisation de matériel amélioré a permis d’augmenter sensiblement la productivité et la qualité des peuplements. Aujourd’hui, les variétés permettent un gain génétique supérieur à 30% pour la croissance et la rectitude du tronc. Le contexte nouveau de la forêt landaise, où une intensification durable de la production est demandée, a relancé les travaux d’exploration de la variabilité inter- et intra- spécifique. Le pin maritime restera l’espèce de choix dans le massif landais. Toutefois, des stratégies pour infuser de la variabilité intraspécifique dans le programme d’amélioration sont en cours de développement afin que les futures variétés soient adaptées aux évolutions économiques et environnementales., Plant material for reforestation or afforestation is of first importance to ensure adaptation of stands to local environmental conditions and to reach goals of wood productivity and quality. Generally the first step focuses on an exploration of between species diversity; then a breeding programme is set up to produce improved genetic material. Maritime pine was chosen for afforestation in the Landes forest (south west of France) during the XIXth century. Later on, a breeding programme was established during the 60’ies based on the local provenance. Development of improved material made it possible to increase stand productivity and quality. Genetic gains of current varieties reach more than 30% for growth and stem straightness. Exploration of diversity between and within species becomes again a key issue in the new context of Landes forest where sustainable intensification is required. Maritime pine will stay the main species in the Landes forest. Nevertheless, strategies are under development to implement new genetic diversity in the breeding programme for adapting futures varieties to environmental and economic changes.

En Afrique sub-saharienne, 90% des semences de mil et sorgho sont autoproduites par les agriculteurs. La recherche de variétés plus productives et rustiques a conduit une association d'organisations paysannes (AOPP) à tester des variétés améliorées en conditions paysannes. L'AOPP participe maintenant à la multiplication et à la diffusion de semences certifiées et s'insère dans une démarche de sélection participative associant recherche, ONG et Organisations Paysannes (OP). Dans le cadre de deux projets sur la gestion de l'agrobiodiversité, une variété de sorgho, Keninkeni Dieman, a été inscrite au catalogue malien en 2012. De plus, une coopérative, GDBA-Mali, a été créée en associant ONG et OP travaillant sur cette thématique. Elle prendra en charge des programmes de sélection participative et la diffusion de semences. À travers ces projets et l'inscription de variétés avec des OP, on peut mesurer l'évolution des systèmes semenciers en Afrique de l'Ouest, de systèmes informel d'un côté ou étatique de l'autre, à un système plus complexe et international.

article présenté lors du colloque ‘Innovations Sylvicoles’ qui s’est tenu à Pierroton le 3 décembre 2014; National audience; Plant material for reforestation or afforestation is of first importance to ensure adaptation of stands to local environmental conditions and to reach goals of wood productivity and quality. Generally the first step focuses on an exploration of between species diversity; then a breeding programme is set up to produce improved genetic material. Maritime pine was chosen for afforestation in the Landes forest (south west of France) during the XIXth century. Later on, a breeding programme was established during the 60’ies based on the local provenance. Development of improved material made it possible to increase stand productivity and quality. Genetic gains of current varieties reach more than 30% for growth and stem straightness. Exploration of diversity between and within species becomes again a key issue in the new context of Landes forest where sustainable intensification is required. Maritime pine will stay the main species in the Landes forest. Nevertheless, strategies are under development to implement new genetic diversity in the breeding programme for adapting futures varieties to environmental and economic changes.; Le choix du matériel végétal pour le reboisement ou l’afforestation est essentiel pour assurer une bonne adaptation du peuplement aux conditions pédo-climatiques locales et atteindre un niveau de production et une qualité correspondants aux objectifs fixés. La première étape consiste généralement à explorer la diversité interspécifique avant de mettre en place un programme de sélection génétique dont l’objectif est de fournir régulièrement du matériel amélioré. Dans les landes de Gascogne, le choix s’est porté, au cours du XIXème siècle, sur le pin maritime puis un programme d’amélioration a été initié dans les années soixante à partir de la provenance locale. L’utilisation de matériel amélioré a permis d’augmenter sensiblement la productivité et la qualité des peuplements. Aujourd’hui, les variétés permettent un gain génétique supérieur à 30% pour la croissance et la rectitude du tronc. Le contexte nouveau de la forêt landaise, où une intensification durable de la production est demandée, a relancé les travaux d’exploration de la variabilité inter- et intra- spécifique. Le pin maritime restera l’espèce de choix dans le massif landais. Toutefois, des stratégies pour infuser de la variabilité intraspécifique dans le programme d’amélioration sont en cours de développement afin que les futures variétés soient adaptées aux évolutions économiques et environnementales.

Increasing salinity in Mediterranean soils and the wide spread of citrus tristeza virus have challenged the use of sour orange (Citrus aurantium) and have accelerated the process of seeking alternative rootstocks. In the present study, nine cultivars of citrumelo (Citrus paradisi Macf. x Poncirus trifoliata (L.) Raf.) were evaluated for salt tolerance. Two month-old seedlings were raised under greenhouse conditions and irrigated with a half strength Hoagland solution supplemented with different concentrations of NaCl, i.e., 0 mM, 35 mM and 85 mM. Tolerance was assessed after two months of stress by measuring stem growth, number of leaves, fresh and dry weight organs and leaf water, chlorophyll and chloride contents. A differential behavior was noticed among the seedlings we studied. When using increased concentration of salt in irrigation water, all the parameters were significantly reduced except for leaf chloride content which highly increased in response to stress. At 85 mM, the cultivar SC2 showed a high tolerance resulting in less apparent leaf symptoms, higher growth and higher leaf chlorophyll content when compared to other seedlings. Similarly, the cultivar C4475-C was shown to be a strong root chloride excluder with less than 2.6% DW (dry weight) chloride accumulation at leaf level. By contrast, our results suggest that C4475-A and C4475-B are salt sensitive cultivars regarding to all the parameters studied while the other citrumelos were considered as moderately tolerant. (résumé d'auteur)

Because irregular bearing generates major agronomic issues in fruit-tree species, particularly in apple, the selection of regular cultivars is desirable. Here, we aimed to define methods and descriptors allowing a diagnostic for bearing behaviour during the first years of tree maturity, when tree production is increasing. Flowering occurrences were collected at whole-tree and (annual) shoot scales on a segregating apple population. At both scales, the number of inflorescences over the years was modelled. Two descriptors were derived from model residuals: a new biennial bearing index, based on deviation around yield trend over years and an autoregressive coefficient, which represents dependency between consecutive yields. At the shoot scale, entropy was also considered to represent the within-tree flowering synchronicity. Clusters of genotypes with similar bearing behaviours were built. Both descriptors at the whole-tree and shoot scales were consistent for most genotypes and were used to discriminate regular from biennial and irregular genotypes. Quantitative trait loci were detected for the new biennial bearing index at both scales. Combining descriptors at a local scale with entropy showed that regular bearing at the tree scale may result from different strategies of synchronization in flowering at the local scale. The proposed methods and indices open an avenue to quantify bearing behaviour during the first years of tree maturity and to capture genetic variations. Their extension to other progenies and species, possible variants of descriptors, and their use in breeding programmes considering a limited number of years or fruit yields are discussed.

Depuis 1999, le GIS Peuplier (AFOCEL -devenue FCBA-, Cemagref -devenu Irstea-, INRA) conduit un programme d’amélioration génétique et réalise ses propres hybridations. Deux grands types d’hybrides sont produits parallèlement : des hybrides euraméricains de première génération (P. deltoides x P. nigra) et des hybrides interaméricains faisant intervenir les deux espèces P. deltoides et P. trichocarpa mais toutefois issus de générations d’hybridation plus ou moins avancées. Le présent rapport fait état des avancées du GIS peuplier en 2012, il est structuré en cinq tâches principales : 1. Sortie variétale : clones hybrides de P. deltoides x P. deltoides Constitution du dossier pour l’inscription des 4 variétés, élaboration du contrat d’édition (GIS Peuplier/Agri-Obtentions/MAAPRAT), des contrats de licence (Agri-Obtentions/pépiniéristes). et choix des pépiniéristes licenciés. 2. Poursuite de la sélection de clones hybrides euraméricains (P. deltoides x P. nigra) Identification moléculaire, qualification de la forme, essai de sensibilité aux pathogènes majeurs des 26 clones euraméricains sélectionnés en 2011. Mise en élevage de plants de deux ans pour installation en populetum d'évaluation agronomique. Installation d’un populetum en parcelles mono-arbres à Bourret (82) 3. Poursuite de la sélection de clones hybrides interaméricains ( P. deltoïdes x P.trichocarpa : F1 et rétro-croisements vers P. deltoïdes) Notation de l’essai résistance et tolérance à la rouille de Charrey-sur-Saône installé en 2011; installation en dispositif d'évaluation du solde de clones issus de rétro-croisements (DxDT). 4. Gestion des futurs parents / Croisements contrôlés : Plantation en archive de géniteurs potentiels (P. nigra, P. deltoïdes, P.trichocarpa) sur deux sites (VG de l’Etat et INRA Bordeaux), Installation en test clonal les recombinaisons intra-spécifiques P. nigra et P. deltoïdes pour sélection de nouveaux parents Récolte du pollen de parents interaméricains pour finaliser les croisements intra spécifiques P. deltoides, 5. Autres actions GIS Peuplier : Contribution à la révision du règlement technique d’admission « peuplier », catégorie testée Évaluation de la sensibilité à l’agent pathogène Marssonina de 5 clones de l’obtenteur privé 3C2A.

En France, le riz est principalement cultivé en zone méditerranéenne, en Camargue. La riziculture irriguée, avec semis direct, y est majoritairement contrainte par l'occurrence de périodes froides et le risque de salinisation des sols. S'y ajoutent des périodes de vent du nord, froid et sec, qui peuvent intervenir tout au long du cycle cultural (avril-mai à septembre-octobre). Depuis 1988, le Centre de coopération internationale en recherche agronomique pour le développement (Cirad) et le Centre français du riz (CFR), conduisent en Camargue un programme d'amélioration variétale. Il vise à créer des cultivars satisfaisant les producteurs (niveau et régularité de la production), les riziers (rendement industriel et transformation) et les consommateurs (qualités de cuisson et de goût). Les riz cultivés en Camargue appartiennent à la sous-espèce japonica d' Oryza sativa. L'hybridation constitue la base de création de variabilité. Les descendances sont sélectionnées selon la méthode généalogique associée ou non à l'haplodiploïdisation appliquée à la première génération. La sélection assistée par marqueurs a été récemment introduite afin d'améliorer l'efficacité de la sélection vis-à-vis de contraintes comme les maladies cryptogamiques dont l'occurrence, en rapport avec le climat, est erratique. Vingt-cinq (25) variétés ont été inscrites au Catalogue officiel, parmi lesquelles 5 ont connu un succès certain auprès des producteurs. Les avancées obtenues pour l'aptitude à la levée en conditions anaérobies, la tolérance à la pyrale, le format et le caractère aromatique du grain sont discutées. Les perspectives en lien avec l'évolution des objectifs, tels que le contrôle des adventices ou l'adaptation au changement climatique, sont exposées.

Plant viral diseases are the most important pathogen attack tomato particularly of which is Tomato yellow leaf curl virus (TYLCV). Obtaining stable and durable resistances seems the most effective solution for controlling the disease. In this context, a breeding programme with two steps was conducted in the Niayes ecological area of Senegal: i) 41 tomato varieties from different origins were screened to assess their reaction to TYLCV disease, ii) 12 resistant varieties and two susceptible were tested in an experimental field. The first step was a preliminary trial in unreplicated plots, to identify promising varieties. However, disease assessments (incidence and severity) were done three times and we used longitudinal data analyses to classify the varieties for resistance. Yields in t/ha were also measured for the different varieties. Among our accessions, Roma VF and Xina known for their susceptibility, and Nadira known for its tolerance, were used as controls. Our results revealed 12 resistant varieties, 16 tolerant varieties and 8 susceptible varieties. The yield values were well correlated to the resistance measured by both incidence and by severity right from the second date of symptom observations, at the time of flowering. TYLCV disease is thus one of the main factors limiting tomato-growing the Niayes agro-ecological area. The second step of the selection process was done in a complete block design with three replications. This trial allowed a confirmation of the 12 resistant varieties. The final selection of the varieties took into account the other traits, like yield and traits related to the fruit characters. (Resume d'auteur)

National audience

Introgression of resistance to coffee berry disease (CBD), caused by Colletotrichum kahawae, is one of the best control methods for this disease. In a set of three successive experiments, we assessed the efficiency of detached berries inoculation to characterize coffee resistance to CBD. Cvs Ruiru 11 and SL 28 were inoculated with a suspension containing from 103 to 106 fungal spores ml-1. The number of infected berries and their degree of infection were assessed and statistically analyzed. Results indicated that berry resistance could be separated into two components: one against the pathogen penetration and the other against its growth in the berries. The existence of a third dynamic component of resistance is suggested: the continued evolution and eventual decrease of resistance during berry expansion and maturation stages. Resistance to C. kahawae penetration was higher in cv. Ruiru 11 than in cv. SL 28, but was bypassed at the highest inoculum concentration tested (106 spores ml-1). The resistance of the inner berry tissues to pathogen growth appeared similar in both cultivars, but was broken in cv. SL 28 at the highest inoculum concentration. It is assumed that both forms of resistance could be of quantitative nature because they were modulated by the inoculum concentration. As the varieties were ranked in the same order in the three experiments, it was concluded that the technique is reliable for a relative ranking of the tested cultivars.

The CFC/ICCO/Bioversity project on "Cocoa Productivity and Quality Improvement: a Participatory Approach" represents an effort to: - Validate on-farm improved varieties selected by the Centre National de Recherches Agronomiques (CNRA); - Explore the results obtained in the project on "Cocoa Germplasm Utilization and Conservation: a Global Approach"; - Promote exchange of varieties with resistance to Phytophthora pod rot. The activities undertaken over the 5-year period (2004-09) included: - On-station selection of the following trials: two clone trials, two intra-population hybrid trials, three hybrid trials, and the establishment of a regional hybrid trial; - On-farm survey about the planting materials used by the farmers and the establishment of 36 demonstration plots on farms including 15 improved varieties selected by CNRA and 15 farmers' selections. The traits evaluated were yield, yield efficiency, percentage of rotten pods and the average weight of one pod. The analyses of the on-station trials showed highly significant differences among the genotypes tested, many of which showed superiority with regard to the control varieties. Genetic parameters were calculated and discussed for the intra-population hybrid trials. This permitted to apply a selection index to increase selection efficiency in these trials. A list of elite hybrids that are candidates for multilocation variety trials has been established. The first results of the Regional Variety Trials shows superiority of the Côte d'Ivoire hybrids for vigour and precocity compared to the introduced varieties. The farm survey included 1133 farmers over the six main cocoa-producing regions. The results show that most farmers use their own farm or neighbours' farms as sources of new planting materials and that yield and precocity are the main selection criteria. The relevance of establishing demonstration plots on-farm to stimulate the farmers to adopt breeders' selections as well as to identify superior farm selections is presented.

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).

National audience

Previous study on food plants has shown that near infrared (NIR) spectral methods seem effective for authenticating coffee varieties. We confirm that result, but also show that inter-variety differences are not stable from one harvest to the next. We put forward the hypothesis that the spectral signature is affected by environmental factors. The purpose of this study was to find a way of reducing this environmental variance to increase the method's reliability and to enable practical application in breeding. Spectral collections were obtained from ground green coffee samples from multi-location trials. Two harvests of bean samples from 11 homozygous introgressed lines, and the cv 'Caturra' as the control, supplied from three different sites, were compared. For each site, squared Euclidean distances among the 12 varieties were estimated from the NIR spectra. Matrix correlation coefficients were assessed by the Mantel test. We obtained very good stability (high correlations) for intervariety differences across the sites when using the two harvests data. If only the most heritable zones of the spectrum were used, there was a marked improvement in the efficiency of the method. This improvement was achieved by treating the spectrum as succession of phenotypic variables, each resulting from an environmental and genetic effect. Heritabilities were calculated with confidence intervals. A near infrared spectroscopy signature, acquired over a set of harvests, can therefore effectively characterize a coffee variety. We indicated how this typical signature can be used in breeding to assist in selection.

Dans un contexte de déréglementation, d'extension des cultures sur milieux contraignants, d'évolution des demandes industrielles et d'utilisations de plus en plus diversifiées, les attentes en matière d'innovation variétale de la canne à sucre sont fortes. L'amélioration variétale permet aussi d'assurer une agriculture respectueuse de l'environnement en utilisant la diversité génétique et les interactions entre la plante, ses pathogènes et son environnement.