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Dans un objectif de contribuer à la diversification la production de la banane aux Antilles françaises, les équipes de recherche du CIRAD et de l’INRA ont entrepris d’explorer la variabilité qualitative des bananes dessert et à cuire et les potentialités d’élaboration de produits transformés. La mise en évidence de liens entre les conditions de production (sol, climat) et les caractéristiques sensorielles et nutritionnelles ont conduit à l’identification de la dénomination « banane de Montagne ». Celle-ci se caractérise par une texture plus ferme, une pulpe plus jaune et présente des teneurs minérales plus faibles. L’évaluation de la qualité au sein de la biodiversité variétale a montré que les variétés locales et les hybrides, issus du programme de création variétale du CIRAD, présentaient des caractéristiques organoleptiques et physico-chimiques leur permettant de se différencier de la variété standard, laCavendish. Parmi les hybrides étudiés, certains ont présenté des aptitudes à la conservation similaires à celle de la Cavendish, leur conférant un potentiel de développement. Des pistes de recherche et développement ont été proposées dans la perspective d’une diversification à travers la fabrication de produits transformés., With the aim to contribute to the diversification of banana production in the French West Indies, research teams from CIRAD and INRA have begun to explore variability in quality of dessert and cooking bananas and potentialities of processed products development. The identification of relationship between production conditions (soil, climate) and the sensory and nutritional characteristics led to the designation "Banane Montagne" as a quality sign for a specific production. It is characterized by a firmer texture, more yellow pulp and provides lower mineral content. Quality assessment of diversity among varieties showed that local varieties and the hybrids from the breeding program of CIRAD have specific taste and chemical characteristics that markedly differentiate themselves from the standard variety, the Cavendish. Among the hybrids studied some showed a storability similar toCavendish, giving them a potential for development. Research projects are being developed on bananas as raw material in agrofood processes aiming to offer new processed and innovative products.

Ripening is the main physiological process affecting banana (Musa spp.) fruit quality traits. The progress of banana ripening process differs for fruit ripened on the plant versus green harvested bunches and depends on the treatment of the fruit after harvest. We investigated the effect of the mode of ripening on ethylene biosynthesis of 'IDN 110' (Musa acuminata, AA genome) banana fruit ripened (a) in planta (On-Plant); (b) ex planta in air (Air-Fruit); or (c) after acetylene treatment (Ace-Fruit). The levels of ethylene production of the whole fruit and, those of 1-aminocyclopropane-1-carboxylic acid (ACC) in pulp, and ACC oxidase (MA-ACO1 and MA-ACO2) and ACC synthase (MA-ACS1) mRNA in both peel and pulp tissues were examined. From harvesting at mature-green stage, the ripening speed of fruit was not correlated with ethylene production. Ace-Fruit took 10 days to reach overripe stage with a maximum of 22.6 µl kg-1 h-1 of ethylene production, whereas Air-Fruit and On-Plant fruit took 27 and 33 days to reach overripe stage, respectively, and produced 11.5 and 29.6 µl kg-1 h-1 of ethylene, respectively. During ripening, ACC accumulated differentially; except for On-Plant fruit, ACC level increased during ripening and concomitantly with ethylene production and MA-ACS1 mRNA level. Whatever the mode of ripening, the level of MA-ACO1 mRNA was 100-fold higher than that of MA-ACO2. The mRNA level of MA-ACO1 and MA-ACO2 were accumulated sequentially during fruit development and ripening. MA-ACO1 gene was transiently induced between mature green and ripe stages while that of MA-ACO2 increased mainly at the overripe stage. The pattern of MA-ACO2 gene expression was correlated with that of ethylene production whatever the mode of ripening while this correlation was observed with MA-ACO1 only On-Plant fruit. These results suggest that: (a) the level of ripening-ethylene production of the whole fruit is not the sole factor controlling the speed of fruit ripening in planta; (b) this level is regulated at the downstream step of ACC biosynthesis mediated by the MA-ACS1 gene; and (c) the product of MA-ACO2 might be involved in this regulation in pulp tissue. These findings are also discussed in regard with improvement of banana quality traits project throughout breeding programs.

Anthracnose of bananas, caused by Colletotrichum musae and crown rot of bananas, caused by a broad unspecific parasitic complex; are the most important post-harvest diseases affecting the quality of exported bananas. These diseases develop during fruit transportation, conservation, ripening and marketing. Like for most post-harvest diseases, the control of these diseases relies mainly on post-harvest practices like fungicide applications, cooling, etc... Nevertheless, seasonal and spatial variations in the performance of these practices highly depend on the elaboration of a potential of fruit quality at field level. This potential of fruit quality is constituted by a physiological component (the fruit susceptibility) and a parasitic component (the level of fruit contamination). Recent work has shown the importance of these pre-harvest factors as important determinants of post-harvest quality of bananas. Referring to the parasitic component, it has been shown, in the case of anthracnose, that floral remnants are the main inoculum sources for fruit contamination by Colletotrichum musae, and that most contaminations occur very early in the field, during the first month of bunch emergence. Referring to the physiological component, fruit grown in highland areas are less susceptible to anthracnose and also to crown rot diseases than fruit grown in lowland areas. By another hand, it has been shown that the physiological age of fruit at harvest has also a strong influence on fruit susceptibility to both diseases: the youngest the fruits, the less susceptible. Lastly, the modification of source-sink ratio (leaf or fruit trimming), influences fruit susceptibility to crown rot but has no influence on fruit susceptibility to anthracnose. These results suggest that alternative methods to control these post-harvest diseases of bananas should take into account these pre-harvest factors.

Changes in amounts of sucrose, hexoses (glucose and fructose), and in activities of Sucrose-phosphate synthase (SPS), Sucrose synthase (SuSy) (sucrose hydrolytic way), Neutral Invertase (NIV) and Acid Invertase (AIV) were studied during development and ripening in-planta of banana fruit (2 dessert varieties: IDN 110 (M. acuminata AA) and Kirun (M. acuminata AA); and 2 cooking varieties: Galéo (M. acuminata AA) and Somwuck (M. acuminata AA). During ripening, all the varieties presented the same pattern of total soluble sugar accumulation. The most remarkable result was that cooking varieties did not accumulate sucrose contrarily to the dessert ones. SPS activity of dessert varieties increased throughout fruit development and ripening. For cooking varieties the activity firstly decreased during development. It increased then after at the beginning of ripening with a peak at half-ripe stage. SuSy activity of all varieties presented the same pattern of changes during development and ripening. Constant at a low level during development, it became extremely low and constant during ripening. NIV activity was extremely low and constant whatever the variety and the developmental stage. AIV activity was low for the two dessert varieties with however a small increase during ripening. Interestingly, it increased drastically during the same period for the low sucrose-accumulating cooking varieties (approximately 6-fold more than for dessert varieties). Our results show that: i) even if SPS activity increases concomitantly to soluble sugar accumulation, we did not find a correlation between its level and the amount of total soluble sugars or sucrose. ii) there is a strong correlation between the level of AIV activity and the ratio sucrose / hexoses; the higher the AIV activity is, the lower the ratio being. This means that AIV could be one of main determinants of the sugar composition of diploid banana fruit by correlating the ratio sucrose / hexoses.

WOUND anthracnose, caused by the fungus Colletotrichum musae, has a major impact on the quality of export bananas worldwide. Fruits harvested at an advanced physiological age seem to be more susceptible to anthracnose. We examined the relationship between the fruit physiological age, measured by the temperature sum (in degree days - dd), and the susceptibility to wound anthracnose by analysing the effects of three factors: - Flooding - a stressful growing condition - in a greenhouse; - Early harvesting of bananas under two climatic conditions; - Source-sink ratio modification by removal of leaves or hands. (Texte intégral)

Ripening is the main physiological process that affects the behaviour of fruit quality traits. The progress of this process in banana fruit is different for fruit ripen or not on the tree and according to the treatment applied to the fruit after harvest. We investigated the effect of the mode of ripening on ethylene biosynthesis of IDN 110 (M. acuminata, AA) banana fruit ripen in-planta (in-Fruit) and ex-plant on air (air-Fruit) or after acetylene treatment (ace-Fruit). The levels of ACC and ethylene production and, those of ACC oxidase (MA-ACO1 and MA-ACO2) and ACC Synthase (MA-ACS1) mRNA were examined in pulp tissue of each of these fruits. Our results showed that, from the harvesting point made at mature-green stage, the ripening speed of fruit was not correlated with ethylene production. Ace-Fruit took 10 days to reach over-ripe stage with a maximum of 22.6 ^l.kg-1.h-1 of ethylene production, whereas Air- and in-Fruit took 27 and 33 days to reach over-ripe stage, respectively, and produced 11.5 and 29.6 ^l.kg-1.h-1 of ethylene, respectively. During ripening, ACC accumulated differentially and, except for in-Fruit, this accumulation was positively correlated with that of MA-ACS1 mRNA. No correlation was observed between ACC level and ethylene production. In all cases, the level of MA-ACO1 mRNA was 100-fold more than that of MA-ACO2, and both of them increased during fruit ripening. In contrast to MA-ACO2, the pattern of MA-ACO1 gene expression was correlated with that of ethylene production whatever the mode of ripening. The results herein suggested that i) the level of ethylene is not the nique factor that controls the speed of fruit ripening in-planta, ii) the level of ripening-ethylene production of the whole fruit is regulated at downstream step of ACC biosynthesis mediated by MA-ACS1 gene and, in pulp tissue, the product of MA-ACO2 might be involved in this regulation.

Wound anthracnose caused by Colletotrichum e, and early ripening are the main problems affecting the quality of export bananas from a lot of countries in the world. In the case of Guadeloupe in French West Indies, these problems generally concern bananas grown in lowland plantations during the rainy season. Three experiments were carried out to study the influence of the physiological age of bananas (calculated on the basis of mean daily temperature sums) on their susceptibility to anthracnose. Stressful growing conditions, especially soil flooding, slowed fruit growth but had no direct effect on fruit susceptibility to C. e or on the green life. However, fruit that had accumulated lower temperature sums were less susceptible to wound anthracnose. By varying the source-sink ratio, we show that bananas of the same grade but different physiological ages had markedly different susceptibility to C. e. Bananas with the same temperature sum accumulation but grown in different soil-climate conditions had different levels of susceptibility. Fruit grown in cooler, highland areas were less susceptible to C. e than fruit of the same physiological age from lowland plantations. Our results suggest that temperature sum accumulation rate is a critical factor affecting the susceptibility of bananas to the pathogen. (Texte intégral)

Mycosphaerella leaf spot diseases Sigatoka disease (SD) and Black leaf streak disease (BLSD) are considered as the most severe diseases of bananas for the export market. Serious infestations can lead to a substantial reduction in the leaf area and thus to fruit yield losses. In addition, these diseases were found to have an impact on fruit quality, especially on ripening earliness, which causes some production losses for exported bananas. To assess the effects of these 2 diseases on the bananas quality (especially its physiological stage), plantation surveys and experiments were conducted in Guadeloupe (F WI) for SD and in Cameroon for BLSD. Bananas quality was characterised, on bananas harvested at a constant physiological stage evaluated in thermal time (temperature sums at 900 degrees day) from flowering to harvest, by its greenlife (duration of preclimacteric period) and by few physico-chemical (grade, weight). Diseases severity was measured either at flowering (for SD) or at harvest (for BLSD). Results of surveys revealed that bananas harvested on plants severely affected with SD or BLSD had similar diameter growth, but a shorter greenlife (GL) than bananas harvested from uninfected or lightly infected plants. A strong correlation was obtained between disease severity and fruit greenlife. All these results indicate clearly the direct effect of MLSD of banana greenlife rather than a trophic effect. The putative physiological mechanisms involved are also discussed.

We previously shown that diploid dessert cultivars accumulate more sucrose during ripening on plant than diploid cooking cultivars, and that Acid Invertase (AIV) might be in this case important by correlating the ratio sucrose / glucose + fructose of fruit (Fils-Lycaon et al. poster). To investigate the putative involved mechanisms, Sucrose Phosphate Synthase (SPS) and AIV, two enzymes involved in sucrose metabolism were studied in fruit of two diploid AA dessert (IDN110) and cooking (Sowmuk) bananas, during their development and postharvest ripening after acetylene treatment. From the green developmental to late ripening stages, SPS activity increased at comparable levels in both varieties from 107 to 222 µmoles of sucrose.h-1.g FW-1 for Sowmuk and from 68 to 168 and then after 106 µmoles of sucrose.h-1.g FW-1 for IDN110. Activity of AIV increased slowly in IDN110 fruit from 3 to 26 µmoles of glucose.h-1.g FW-1, and drastically in Sowmuk from 4 to 207 and then after 174 µmoles of glucose.h-1.gFW-1. At molecular level, the pattern of SPS and Cw-AIV mRNA accumulation was similar in both varieties during fruit development and ripening. SPS mRNA level increased transiently during the green developmental stage while that of Cw-AIV increased with ripening. Interestingly, at equivalent stages, the increase of Cw-AIV mRNA level was approximately 100-fold more in Sowmuk than in IDN110, which corroborates with the higher AIV activity measured for Sowmuk. As between the two varieties, no significant changes were observed for neutral invertase activity and for Susy gene expression and activity, our data strongly suggest that AIV activity constitutes a key step that controls the sucrose level during ripening of diploid banana fruit and that Cw-AIV gene contributes to this activity. Thus, Cw-AIV constitutes a target for the identification of molecular markers usable in breeding, and marker-assisted selection to improve quality traits of banana fruit.

We attempt to get more insight into molecular mechanisms that govern ethylene responsiveness in banana fruit. We report here the isolation of one complete and three partial cDNAs encoding for banana ETHYLENE-INSENSITIVE3-like protein (EIL). In the proposed model of the ethylene signal transduction pathway, the EIL protein is a transcription factor that acts downstream from the ethylene receptors. The partial MaEIL cDNAs, namely MaEIL1 (1817 bp), 2 (1840 bp) and 3 (1920 pb) encode for a protein of 495, 517 and 517 amino acids, respectively. These clones are 51 to 70% and 35 to 70% identical at nucleotide level and at polypeptide level, respectively; MaEIL3 being more homologous to MaEIL1 than MaEIL2. The full length cDNA (MaEIL4) is 2435bp long and encodes for a protein of 635 amino acids. It is 40 to 70% and 32 to 75 identical to the three others at nucleotide level and protein levels, respectively. The predicted polypeptide sequence of all these clones contains the conserved domains of EIN3-like proteins in their N-terminal half, including the prolinerich domain and the basic domains III, IV and V. In phylogenetic analysis, although MaEIL1, 3 and 4 belong to the cluster consisting of EIN3 and EIN3-like proteins known to be involved in ethylene transduction pathway, they constitute a quite different subgroup. MaEIL2 appears to be the most distantly related to this cluster. RT-PCR and northern blot experiments were performed to analyze the regulation of each gene expression by ripening and ethylene. (Texte intégral)

La production de banane à Grenade a été complètement détruite par le cyclone 'Yvan' en 2004. Les missions entreprises par un collège d'experts du Cirad visent à relancer la production de banane pour satisfaire le marché local, voire ensuite le marché d'export (régional ou européen). Sur les aspects post-récolte, il a été constaté que des mesures d'incitations financières à la production de banane de qualité seraient nécessaires. A partir de là, des efforts devront être fournis par les producteurs en terme de soins aux régimes (gainage, ablation), prévision de récolte et de conditionnement pour envisager une exportation régionale ou internationale. Un disque de récolte sera proposé dans la perspective d'exportation. La mûrisserie locale présente un équipement mal adapté pour permettre à la fois d'assumer la gestion des stocks et la qualité des fruits. Des aménagements sont proposés: création d'une chambre de gazage, appareils de contrôle de température, réhumidificateurs d'air.

Banana production is a key economic resource in the French West Indies. It is essential that growers in this region enhance their sales by proposing new products-such as mountain bananas-in response to high market competition from other exporting regions where production costs are lower. The quality of mountain bananas is officially recognised in Europe on the basis of a real taste difference. All French West Indian bananas grown at altitudes over 250 m ASL according to specifications can be sold under the mountain banana label. Mountain banana features can be assessed via objective data. At harvest stage, mountain bananas are denser, bulkier and less susceptible to wound anthracnose, caused by Colletotrichum musae, than lowland bananas, probably because of their higher mechanical resistance. Sensorial differences have also been documented in ripe bananas. At the same harvest stage and under identical ripening conditions, mountain bananas have a firmer texture, more intense yellowish pulp, and higher sugar and aromatic compound contents. A jury taste test analysis confirmed the sensorial differences between lowland and mountain bananas. The results of a multisite study indicated that temperature and rainfall during bunch growth are the main factors that distinguish mountain bananas.

It is now assumed that the quality of fruit is a complex trait in which a lot of mechanisms are involved, some of them being antagonistic. All of these mechanisms are the results the coercive action of differentially regulated genes. Understanding at molecular level of the mechanisms that control the target quality trait is an essential work beforehand to any plan of improvement of fruit quality trait using plant genetic strategies such as candidate-gene approach and or marker-assisted selection. Presently we investigate at molecular level the ethylene responsiveness, and sugar and phenylpropanoïd metabolisms, three ripening aspects involved in functional, nutritional and organoleptic qualities of banana fruit. As a first part of this project, we report here the cloning and sequencing of genes that are differentially expressed during fruit ripening, as tools for functional genomic studies and putative molecular marker developments. Different molecular biology approaches haves been used to isolate ripening these ripening related-genes. They include cDNA amplification (RT- and RACE-PCR) and, construction of complete and subtractive suppressive cDNA libraries (SSH). Sequencing and BLAST analysis of some of these isolated cDNA clones revealed that 205 of them presented a high homology with different genes in database. Many of the predicted proteins encoded by these genes are putatively involved in the regulation of gene expression, hormonal metabolism, hormonal-signal transduction, sugar metabolism and other ripening process. Among these 205 genes, 11 are still unclassified since presenting homology to unknown proteins of rice or Arabidopsis. Finally, thirteen additional clones were putatively novel, since they failed to match with database sequences. Expressions of a few of the matching clones have been followed in relation with ethylene responsiveness of fruit. Our results show that the expression of these genes is under ethylene and development (or both) control. These cDNA clones provide us with a basis for future work that will combine physiological, genomic and genetic approaches to identify key candidate-genes involved in the expression of banana quality trait. (Texte intégral)

Les maladies de conservation (anthracnose de blessure, anthracnose de quiescence, pourritures de couronnes) sont des facteurs qui limitent fortement la commercialisation des bananes exportées. Le Colletotrichum musae est à l'origine des deux formes d'anthracnose, tandis qu'un complexe parasitaire plus important est impliqué dans les pourritures de couronnes: C. musae, mais aussi d'autres espèces parmi lesquelles des Fusarium, des Verticillium, des Botryodiplodia. La sensibilité à ces maladies est variable en fonction des zones de production, mais aussi en fonction du stade de maturité des fruits, et la lutte est essentiellement chimique. Les variétés de bananiers cultivées pour l'exportation, sont triploïdes et généralement fortement stériles. Ceci complique les schémas d'amélioration génétique et peu de produits issus de l'amélioration ont été diffusés à ce jour. Par le passé, les objectifs des programmes d'amélioration génétique des bananiers ont essentiellement concerné l'obtention de variétés résistantes aux cercosporioses des bananiers et à la maladie de Panama. Aujourd'hui, les caractères relatifs à la qualité des fruits sont intégrés dans les programmes d'amélioration.

Export Banana is the first agricultural production in the French West Indies. Intensive cropping of this banana generally induces substantial pollution and damage to the fragile tropical insular environment of Guadeloupe and Martinique. Moreover, high production costs and international competition make it difficult to compete in these conditions. Among the tools developed by CIRAD to promote alternative and sustainable banana cropping systems as well in an economic way as in an ecological one, creation and selection of new varieties that are resistant or tolerant to the main pests and diseases of bananas are the main purpose of a fifteen years lasting research program. Since three years, work has been focused on the validation of these new disease-resistant hybrids, involved in an integrated development program, VaNouBa, gathering all the aspects of evaluation in industrial conditions: agronomy, phytopathology, physiology and genetics. Within the frame of this project, the promising hybrid "FlhorBan 920" is being studied. Twenty hectares have thus been planted in Guadeloupe and Martinique in 2004 with this variety which is resistant to Yellow Sigatoka Disease (Mycosphaerella musicola) and Black Leaf Streak Disease (M. fijiensis), and tolerant to lesion nematodes. Thanks to its multiple resistance/tolerance features, this variety can validly be considered as an environmentally-friendly banana. Moreover the fruit, looking and tasting different from the traditional Cavendish varieties may allow the banana growers from Martinique and Guadeloupe to propose a very specific and competitive product. The success of the current development step will lead to a very near commercial launching step.

L'anthracnose de blessure due à Colletotrichum musae est la maladie de conservation qui pénalise le plus fortement les bananes en provenance des Antilles Françaises. Elle affecte particulièrement la production des plantations de basse altitude au cours de la saison des pluies. Une enquête agronomique menée au sein de la bananeraie Guadeloupéenne a permis de mettre en évidence la faible sensibilité à C. musae des fruits de "montagne" et la grande variabilité de sensibilité des fruits de basse altitude. Au sein de cette zone, les fruits les plus sensibles se caractérisent par de fortes teneurs en Mn et de faibles teneurs en Ca. Ces deux éléments minéraux ne semblent pas être directement impliqués dans la relation hôte-pathogène. Par contre, les fortes teneurs en Mn pourraient être indicatrices de conditions de stress pour le bananier. Le stress de culture n'a pas d'effet direct sur la relation hôte-pathogène, mais entraîne par contre un ralentissement important de la croissance des fruits. Des expérimentations où le rapport source/puits était modifié ont montré, qu'au sein d'une zone homogène, l'âge physiologique des fruits calculé en somme de températures était le facteur explicatif principal de la sensibilité des fruits à C. musae. Par contre, lorsque les températures sont différentes, comme entre la zone de "montagne" et la zone de basse altitude, la vitesse d'accumulation des sommes de températures semble également être un facteur prépondérant. Enfin, il est apparu que l'éthylène et la maturation du fruit n'étaient pas impliquées dans le développement des lésions d'anthracnose de blessure. Par contre, un lien a été suggéré entre la capacité du fruit à mûrir et la sensibilité à C. musae. Les résultats obtenus au cours de ce travail ont plusieurs applications, notamment en terme de gestion de la récolte et de regroupement des productions au cours du transport.

Dans un contexte de forte concurrence internationale, l'élimination du traitement chimique après récolte des bananes d'exportation constitue aujourd'hui l'enjeu qui permettrait de renforcer la sécurité alimentaire des consommateurs et de démarquer la filière antillaise sur un nouveau segment de marché. En effet, cette lutte chimique est aujourd'hui remise en cause par (i) l'apparition de souches résistantes aux fongicides utilisés; (ii) le manque d'efficacité de ces traitements signalé régulièrement au cours du second semestre; (iii) les attentes des consommateurs et des pouvoirs publics pour une agriculture plus respectueuse de la santé et de l'environnement. Ce projet vise à définir des méthodes permettant de contrôler les maladies de conservation (anthracnose et pourritures de couronnes) tout en excluant le recours à la lutte chimique. Un cahier des charges, économiquement viable et s'adressant à l'ensemble des maillons de la filière, sera élaboré pour produire des fruits "propres" satisfaisant aux standards de qualité en vigueur.

The quality of a fruit like banana results from numerous modifications which take place during ripening. Among these are the biosynthesis of the hormone ethylene (Liu and al., on 1999), the degradation of starch, and the biosynthesis of free sugars (Beaudry et al., 1989; Hubbard et al., 1990; Cordenunsi and Lajolo, 1995; Do Nascimento et al., 2000; Purgatto et al., 2001). These metabolic pathways were studied at the biochemical and molecular level. However, neither their putative regulation at the gene level by ethylene, nor the relations between the synthesis of starch, its degradation and the appearance of free sugars, have been well established yet. The objectives of this study are: - to understand events of ripening like the biosynthesis of ethylene and soluble sugars, - to characterise the quality of four potential parents, at the physico-chemical, biochemical and molecular levels.

Dans un contexte de forte concurrence internationale, l'élimination du traitement chimique après récolte des bananes d'exportation constitue aujourd'hui l'enjeu qui permettrait de renforcer la sécurité alimentaire des consommateurs et de démarquer la filière antillaise sur un nouveau segment de marché. L'objectif des travaux menés par le Cirad-Flhor a été de mieux comprendre l'élaboration de la qualité des fruits afin de proposer de nouvelles techniques de lutte contre les maladies de conservation et de limiter les mûrs d'arrivage.

The harvesting of bananas for export is constrained by the need to transport the production by sea to the importing country, which takes 10-20 days from the West Indies to Europe. The fruit must arrive before the start of the climacteric rise. The fruit must therefore be harvested early enough to have a green life (GL, time elapse, in degree-days, between cutting the fruit and the climacteric rise) longer than the transport time. Our aim is to find an indicator of harvesting date which would give rise to a constant GL at harvest. For this purpose, it was assumed that GL depends on fruit maturity and thus on its developmental stage at harvest. Several indicators of development were considered: - the fruit age expressed in degree-days (dd, base temperature 14°C) accumulated since inflorescence emergence, - the relation between GL and pulp organic acid content.

Wound anthracnose is a disease of banana that is caused by a fungus, #Colletotrichum musae#, which infects the fruit in the field and stay quiescent until the fruit ripen. When the fruit are damaged, larger lesions develop while the fruit are still green. Anthracnose appear every year in the middle of the rainy season, mainly in low-altitude areas. In order to identify the factors which might explain variation in fruit susceptibility to wound anthracnose, a diagnostic survey was conducted in all of the soil and climatic conditions of Guadeloupe.

Banana fruit weight and size are important criteria for banana growers as they determine yield and sell prices. Within-bunch variability in fruit weight was recently shown to be related to a difference in pulp cell number (PCN) at the end of cell divisions (350 degree-day (dd) after inflorescence emergence). However, it is likely that both source activity and sink size determine fruit weight and size. Two hypotheses are tested. (i) source/sink ratio modifications during cell division phase influence PCN and thus pulp dry weight (PDW) at harvest, (ii) PCN mostly détermines fruit length while cell filling rate mostly determines fruit diameter.

Within-bunch variability in banana (cv Cavendish Grande Naine) fruit size is a result of a negative gradient in fruit weight and size from the top to the bottom of the bunch. A histological study of pulp development combined with fruit growth measurements (diameter, length and weight) was carried out to define development phases and to date the end of cell multiplication in pulp. To relate pulp cell number (PCN) and fruit filling rate, we applied variations in the source/sink ratio before and after the end of pulp cell division using fruit pruning, bunch bagging and leaf shading. For a fruit located at the top of the bunch, PCN on a fruit radius and starch grain number per cell increased from 70 degree-day (dd.) after flower emergence to approximately 350 dd.. At 200 dd., starch grain size and pulp dry matter weight started increasing. A development lag of about 50 dd. appeared between top and bottom fruits. This lag led to a lower cell number on a fruit radius at 350 dd. in bottom fruits. Pulp digestion and cell counting confirmed this result and showed that early bunch bagging increases PCN. As fruit volume at the end of cell division and PCN were strongly correlated, PCN was estimated for each treatment. Estimated PCN was found to be well correlated to fruit filling rate for different source/sink ratios. (Texte intégral)

L'anthracnose de blessure de la banane due à #Colletotrichum musae# est une maladie post-récolte qui cause d'importantes pertes de production aux Antilles françaises, principalement au second semestre de l'année sur des fruits issus des bananeraies de basse altitude. Une enquête-diagnostic a été menée en Guadeloupe et en Martinique en 1996 et 1997 sur 120 parcelles représentatives de l'ensemble des situations pédo-climatiques et des techniques culturales de chaque île. Plusieurs critères de qualité du fruit ont été analysés : la pression naturelle d'inoculum, la dureté de la pulpe, et l'efficacité du traitement fongicide. Les analyses statistiques ont permis de montrer que le niveau de contamination est fortement lié à la qualité du nettoyage de la parcelle, puis à la zone pédo-climatique, caractérisée par la pluviométrie. Il n'y a pas de relation directe entre l'anthracnose et les critères mécaniques du fruit. Pour la dureté de la pulpe, il apparaît que les facteurs explicatifs de la variabilité sont l'altitude, puis la teneur en certains éléments minéraux dans la pulpe des fruits. Pour le critère relatif à l'efficacité du traitement fongicide, il semble que l'altitude soit le facteur explicatif le plus pertinent. Les fruits provenant des bananeraies d'altitudes élevés (plus de 300m) présentent des caractéristiques de résistance plus importantes que les fruits des zones de pleines. Cependant, aucun facteur relatif à la nutrition minérale du bananier et au rendement de la parcelle n'a pu être relié avec la sensibilité à C. musae des fruits. Des hypothèses relatives à des stress de culture pendant la phase de croissance des fruits, engendrant une modification du potentiel de qualité de la banane, sont alors envisagées

Banana growers commonly use blue sleeves to protect the bunches during fruit growth. The Katryx(R) bag is a transparent sleeve with specific UVb and IR permeability properties, particularly a 30 % IR permeability reduction. This three-layer product was developed and patented by the Plastibana company, to allow better light and temperature conditions for banana growth. The effects of Katryx(R) and blue sleeves on the inside microclimate and on fruit quality were investigated. When using a frame to simulate the bunch, it was found that the Katryx(R) sleeve had a buffer effect with high temperatures. Thermal variations between night and day were thus limited; the inside temperature was kept around the theoretical optimum growth value in the West Indies, which varies between 29 and 30'C. When using the Katryx(R) sleeve, an increase in light quantity and a modification in light quality were also observed and, therefore, an increase in the photothermal coefficient. Banana plants ('Cavendish' cv 'Grande Naine') were used to investigate the effect of Katryx(k and blue sleeves on fruit growth. Katryx(R) covering increased fruit firmness and peel hardness, as well as fruit length and average grade (+2 to 8%), depending on the environmental conditions and on the position of the hand.

L'engainage des régimes de bananes est une technique culturale utilisée pour limiter le grattage des fruits dû au frottement des feuilles et accélérer la croissance des bananes. La gaine Katryx, transparente et incolore, est un plastique composé de trois couches qui, par ces propriétés optiques et thermiques, permet de modifier l'environnement microclimatique autour du régime. Ce microclimat et ses effets sur la croissance des fruits ont été comparés à ceux observés avec la gaine en polyéthylène bleu habituellement utilisée aux Antilles. Trois types d'essais ont été réalisés. Le premier a cherché à caractériser le microclimat sous gaine par des mesures de température et de rayonnement. Les deuxième et troisième essais ont permis d'évaluer les effets de ce microclimat sur la croissance des fruits, en station expérimentale et en plantation. Le microclimat sous la gaine transparente se caractérise par une réduction des fortes températures et une augmentation de la qualité du rayonnement incident sur le régime. Le rapport journalier entre ce rayonnement et la température est deux fois plus élevé sous la gaine Katryx que sous la gaine bleue. Il en résulte que l'intervalle floraison-récolte est réduit et les fruits présentent une croissance améliorée. La gaine Katryx permet d'améliorer les conditions de croissance des bananes et, de ce fait, d'augmenter de manière significative la productivité des bananeraies. Une meilleure compréhension des effets qu'elle provoque devrait permettre d'envisager l'élaboration d'une gaine apte à optimiser les conditions de croissance des bananes.