Expression of a rice chitinase gene in transgenic banana ('Gros Michel', AAA genome group) confers resistance to black leaf streak disease

Peer reviewe

La banane: de son origine à sa commercialisation

Les bananiers cultivés sont des herbes géantes appartenant au genre Musa. Ils produisent des fruits qui sont à la fois stériles et parthénocarpiques. Il en existe plus de 1 000 variétés et ce sont généralement des clones triploïdes (parfois diploïdes ou tétraploïdes) issus principalement de croisements entre deux espèces sauvages séminifères, Musa acuminata et Musa balbisiana. En termes de production mondiale, la banane est le quatrième produit agricole après le riz, le blé et le maïs. Elle constitue la base de la sécurité alimentaire de nombreuses populations. Les systèmes culturaux sont très diversifiés de par le monde et les objectifs contrastés : autoconsommation, ventes sur les marchés locaux ou nationaux, exportation, etc. Il faut distinguer les bananes à cuire, comprenant entre autres les plantains, des bananes dessert qui font notamment l’objet d’un important commerce international. Ce dernier a débuté au début des années 1900 et a connu depuis lors une croissance continue. Actuellement, la banane est le fruit le plus exporté tant en termes de valeur que de quantité et cette industrie est d’une importance vitale pour les pays producteurs. Malgré la grande diversité génétique rencontrée au sein du genre Musa, le marché d’exportation repose essentiellement sur le seul groupe variétal Cavendish. La production de banane doit faire face à de nombreux défis d’origines biotique et abiotique pour continuer de répondre aux critères de durabilité, qualité et rendement qui lui sont imposés.Cultivated bananas are giant herbaceous plants within the genus Musa. They are both sterile and parthenocarpic. There are well over a thousand domesticated Musa cultivars, they are mostly triploid (a few are diploid or tetraploid) and are derived from crosses between two wild species, Musa acuminata and Musa balbisiana. In terms of production, bananas are the fourth agricultural product after rice, wheat, and maize. They constitute the basis of food security for many people. Cropping systems vary widely around the world and contrasting objectives are encountered: consumption by the producer, sale on local or national markets, export, etc. Cooking bananas, including plantains, must be distinguished from dessert bananas, which constitute a major international trade. This international trade started only in the early 1900s but it has since grown continuously. Banana is currently the most exported fruit, in terms of both value and quantity. Despite the high genetic diversity found within the genus Musa, the export market is mainly based on single Cavendish. There are major challenges to banana production from biotic or abiotic stresses to continue to meet the criteria of sustainability, quality and yield that are imposed

Analysis of the mechanisms of action of Mycosphaerella fijiensis toxins during the development of Black Leaf Streak disease.

peer reviewedThe goal of our programme is to understand the role of M. fijiensis toxins in Black Leaf Streak disease to facilitate early selection of banana genotypes resistant to the disease. Toxic effects induced by crude extracts, as well as by purified juglone released by the pathogen in culture filtrates, were analysed on two reference cultivars of banana. Injection of the pathogen metabolites into banana leaves showed a light-dependent toxicity revealed by the development of necrosis and a rapid decrease of the relative vitality index determined from chlorophyll fluorescence measurements. We demonstrated that juglone, a purified metabolite of M. fijiensis, has a direct inhibitory effect on the electron transfer properties of purified banana chloroplasts. Regardless of the bioassay performed, the susceptibility of the two reference cultivars to this metabolite was correlated with their respective sensitivity to the pathogen infection. On the other hand, some preliminary data showed that juglone initiates oxidation of ascorbic acid, the most abundant antioxidant system in plants. On this base, we hypothesized that oxidative damage could be involved in the action of M. fijiensis toxins

Pythium root rot of common bean : biology and control methods. A review

Pythium root rot constitutes a highly damaging constraint on the common bean, Phaseolus vulgaris L., grown in several areas of Eastern and Central Africa. Here, this food legume is cultivated intensively under poor conditions of crop rotation due to the exiguity of the land in the region. Yield losses of up to 70 % in traditional local bean cultivars have been reported in Kenya and Rwanda. In this study, a detailed analysis of the biology and diversity of the Pythium genus was carried out in order to understand the mechanisms leading to the development of the disease. Various control methods for reducing the damage provoked by this disease were analyzed