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Black Leaf Streak Disease (BLSD), caused by the fungal pathogen Mycosphaerella fijiensis, is the most important foliar disease affecting banana production worldwide, reducing fruit weight and fruit aptitude for conservation. With growing concerns about environmental preservation and stricter legislation, alternatives to chemical control for BLSD are an important challenge, especially in the French West Indies. These new approaches include various agronomical practices that could help reducing disease development, and its impact on bunch weight and fruit conservation. Designing new cropping systems without fungicide control of BLSD implies an integrated strategy and a combination of these practices. To understand better the relationships between leaf spots diseases and fruit conservation, Cavendish bananas were grown in different situations in Cameroon, Guadeloupe and Brazil. These experiments showed that a signal from diseased leaves triggers a direct reduction in banana green life duration, and that this signal might be stopped through the elimination of diseased leaves. Lately, a new prototype of cropping system has been evaluated in ecological conditions unfavorable to BLSD (in Dominican Republic), combining practices that would control disease cycle and the reduction of crop losses. In such conditions, even if bananas were harvested with a very low leaf surface, green life of the fruit proved to be acceptable for export, thanks to an adequate and regular pruning of the infected leaves. This result questions the usual threshold of 4 to 5 leaves required at harvest time for bunches as acceptable for exportation. However, variable losses (10-15%) in fruit weight were observed. This prototype should be now evaluated in epidemiological situations more favorable to disease development. New practices might also be associated in these conditions, like the introduction of biodiversity (mixtures of species) or the use of plant defense stimulators.

Black Leaf Streak Disease (BLSD), caused by the fungal pathogen Mycosphaerella fijiensis, is the most important foliar disease affecting banana production worldwide, reducing fruit weight and fruit aptitude for conservation. With growing concerns about environmental preservation and stricter legislation, alternatives to chemical control for BLSD are an important challenge, especially in the French West Indies. These new approaches include various agronomical practices that could help reducing disease development, and its impact on bunch weight and fruit conservation. Designing new cropping systems without fungicide control of BLSD implies an integrated strategy and a combination of these practices. To understand better the relationships between leaf spots diseases and fruit conservation, Cavendish bananas were grown in different situations in Cameroon, Guadeloupe and Brazil. These experiments showed that a signal from diseased leaves triggers a direct reduction in banana green life duration, and that this signal might be stopped through the elimination of diseased leaves. Lately, a new prototype of cropping system has been evaluated in ecological conditions unfavorable to BLSD (in Dominican Republic), combining practices that would control disease cycle and the reduction of crop losses. In such conditions, even if bananas were harvested with a very low leaf surface, green life of the fruit proved to be acceptable for export, thanks to an adequate and regular pruning of the infected leaves. This result questions the usual threshold of 4 to 5 leaves required at harvest time for bunches as acceptable for exportation. However, variable losses (10-15%) in fruit weight were observed. This prototype should be now evaluated in epidemiological situations more favorable to disease development. New practices might also be associated in these conditions, like the introduction of biodiversity (mixtures of species) or the use of plant defense stimulators.

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.

Ethylene signal transduction initiates with ethylene binding at receptor proteins and terminates in a transcription cascade involving the EIN3/EIL transcription factors. In order to get more insights into the ethylene responsiveness process of banana fruit, we have isolated from banana fruit four cDNA homologs of the Arabidopsis EIN3/EIN3-Like gene, MaEILs (Musa acuminata ethylene insensitive 3-like). Sequence comparison with other banana EIL genes already registered in the database led us to conclude that, at this day, at least 5 different genes namely MaEIL1, MaEIL2/AB266318, MaEIL3/AB266319, MaEIL4/AB266320 and AB266321 exist in banana. Expression of these genes were further analysed in peel and pulp tissues, in relationship with changes of fruit ethylene responsiveness and ripening processes. MaEIL mRNAs were detected in all examined tissues but at lower level in peel than in pulp. According to tissues, MaEIL genes were differentially regulated by ripening and ethylene in mature green fruit. MaEIL2/AB266318 was the unique ripening- and ethylene-induced gene, MaEIL1, MaEIL4/AB266320 and AB266321 genes were down-regulated while MAEIL3/ AB266319 presented an unusual pattern of expression. Interestingly, a marked change was observed mainly on MaEIL1 and MaEIL3/AB266319 mRNA accumulation, concomitantly with changes in ethylene responsiveness of fruit. Data presented in this study suggest the importance of a transcriptionally step control in the regulation of EIL genes during banana fruit ripening.

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.

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.

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.

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.

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.

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.

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.

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. The

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. The

La culture de la banane d'exportation est la première production agricole aux Antilles françaises. Pratiquée de façon intensive, elle est génératrice de pollutions et de dégradations de l'environnement insulaire fragile de Martinique et de Guadeloupe. Qui plus est, les coûts de production élevés et la concurrence internationale rendent cette culture difficilement compétitive. Parmi les outils que développe le Cirad pour promouvoir des systèmes de cultures alternatifs et durables, tant au plan économique qu'écologique, la création et la sélection d'hybrides bananiers résistants ou tolérants aux principales maladies et aux ravageurs se font depuis quinze ans. Depuis trois ans, l'accent a été mis sur la validation des hybrides créés à travers le projet de développement "VaNouBa", intégrant tous les aspects de l'évaluation en conditions réelles: agronomie, phytopathologie, physiologie et génétique. Dans ce cadre, une variété est actuellement à l'étude: FihorBan 920. Vingt hectares partagés entre Guadeloupe et Martinique ont été plantés en 2004. Résistante aux cercosporioses et tolérante aux nématodes, la FlhorBan 920 est une banane plus propre, plus respectueuse de l'environnement et de la santé du consommateur. De plus, de goût et d'aspect différents de la variété classique, elle devrait permettre aux producteurs antillais de commercialiser une banane capable de se démarquer sur le marché d'exportation. Si cette phase de développement est un succès, elle sera ensuite suivie d'une phase de lancement commerciale.

La culture de la banane d'exportation est la première production agricole aux Antilles françaises. Pratiquée de façon intensive, elle est génératrice de pollutions et de dégradations de l'environnement insulaire fragile de Martinique et de Guadeloupe. Qui plus est, les coûts de production élevés et la concurrence internationale rendent cette culture difficilement compétitive. Parmi les outils que développe le Cirad pour promouvoir des systèmes de cultures alternatifs et durables, tant au plan économique qu'écologique, la création et la sélection d'hybrides bananiers résistants ou tolérants aux principales maladies et aux ravageurs se font depuis quinze ans. Depuis trois ans, l'accent a été mis sur la validation des hybrides créés à travers le projet de développement "VaNouBa", intégrant tous les aspects de l'évaluation en conditions réelles: agronomie, phytopathologie, physiologie et génétique. Dans ce cadre, une variété est actuellement à l'étude: FihorBan 920. Vingt hectares partagés entre Guadeloupe et Martinique ont été plantés en 2004. Résistante aux cercosporioses et tolérante aux nématodes, la FlhorBan 920 est une banane plus propre, plus respectueuse de l'environnement et de la santé du consommateur. De plus, de goût et d'aspect différents de la variété classique, elle devrait permettre aux producteurs antillais de commercialiser une banane capable de se démarquer sur le marché d'exportation. Si cette phase de développement est un succès, elle sera ensuite suivie d'une phase de lancement commerciale.

Anthracnose is the main post-harvest disease of bananas grown in the French West Indies. Colletotrichum musse, the causal agent, forms quiescent infections on the fruit peel that lead to necrosis at maturity. The existence of quiescent infections makes it impossible to assess the inoculum level on the fruit peel before the ripening of the banana. The development of a technique to quantify the inoculum level on the fruit before harvest would be very interesting for banana growers; it can lead them for certain technical decision such as whether or not to apply fungicides after harvest. This work has been done to determine a practical method, usable in routine, to quantify the inoculum level on mature and immature fruit, so that it can be used as a method of early prediction. Two points have to be considered: - breaking the dormancy of the appressoria, - the non apparition of senescent spots. After the elaboration of the method, we have considered the role of the ethylene treatment as the primary determinant of the breaking of the dormancy of the appressoria. (Résumé d'auteur)

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.

Anthracnose is the main post-harvest disease of bananas grown in the French West Indies. Colletotrichum musse, the causal agent, forms quiescent infections on the fruit peel that lead to necrosis at maturity. The existence of quiescent infections makes it impossible to assess the inoculum level on the fruit peel before the ripening of the banana. The development of a technique to quantify the inoculum level on the fruit before harvest would be very interesting for banana growers; it can lead them for certain technical decision such as whether or not to apply fungicides after harvest. This work has been done to determine a practical method, usable in routine, to quantify the inoculum level on mature and immature fruit, so that it can be used as a method of early prediction. Two points have to be considered: - breaking the dormancy of the appressoria, - the non apparition of senescent spots. After the elaboration of the method, we have considered the role of the ethylene treatment as the primary determinant of the breaking of the dormancy of the appressoria.

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.