Expression patterns of cell wall-modifying genes from banana during fruit ripening and in relationship with finger drop

Few molecular studies have been devoted to the finger drop process that occurs during banana fruit ripening. Recent studies revealed the involvement of changes in the properties of cell wall polysaccharides in the pedicel rupture area. In this study, the expression of cell-wall modifying genes was monitored in peel tissue during post-harvest ripening of Cavendish banana fruit, at median area (control zone) and compared with that in the pedicel rupture area (drop zone). To this end, three pectin methylesterase (PME) and seven xyloglucan endotransglycosylase/hydrolase (XTH) genes were isolated. The accumulation of their mRNAs and those of polygalaturonase, expansin, and pectate lyase genes already isolated from banana were examined. During post-harvest ripening, transcripts of all genes were detected in both zones, but accumulated differentially. MaPME1, MaPG1, and MaXTH4 mRNA levels did not change in either zone. Levels of MaPME3 and MaPG3 mRNAs increased greatly only in the control zone and at the late ripening stages. For other genes, the main molecular changes occurred 1–4 d after ripening induction. MaPME2, MaPEL1, MaPEL2, MaPG4, MaXTH6, MaXTH8, MaXTH9, MaEXP1, MaEXP4, and MaEXP5 accumulated highly in the drop zone, contrary to MaXTH3 and MaXTH5, and MaEXP2 throughout ripening. For MaPG2, MaXET1, and MaXET2 genes, high accumulation in the drop zone was transient. The transcriptional data obtained from all genes examined suggested that finger drop and peel softening involved similar mechanisms. These findings also led to the proposal of a sequence of molecular events leading to finger drop and to suggest some candidates

Effects of Black Leaf Streak Disease and Sigatoka Disease on fruit quality and maturation process of bananas produced in the subtropical conditions of southern Brazil

Banana fruits are harvested at the green-mature stage (pre-climacteric) in order to allow sufficient time for transport and marketing. The time between the harvest and the initiation of the natural ripening process is called green life (GL), which is closely correlated to physiological age. Sigatoka Disease (SD: also called yellow Sigatoka) and Black Leaf Streak Disease (BLSD; also called black Sigatoka) are the main foliar diseases affecting banana production. The aim of this work was to investigate the influence of these diseases on banana GL and postharvest behavior in subtropical conditions (southeastern Brazil). The results showed that both diseases shortened the banana's GL when compared to control bananas of the same physiological age. Moreover, fruits from infested plots showed higher values of CO2 (+100% for SD and +300% for BLSD) and C2H4 production (+30% for SD and +60% for BLSD) at the climacteric peak. BLSD caused 40% reduction in fruit weight. Fruits from plants with a high degree of SD or BLSD undergo an altered maturation process. (C) 2011 Elsevier Ltd. All rights reserved.MA

MOUNTAIN BANANAS FROM THE FRENCH WEST INDIES

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

Mountain Bananas From French West Indies: First Data of Physico-Chemical Characterization

In order to propose a 'mountain' banana on the French market, the physicochemical caracteristics of bananas, growing at two different altitudes (Low 50 m and High 300 m) in Martinique, French West Indies, were compared. At the same harvest stage, fruits from the high altitude were significantly heavier, bigger and had a higher density and firmness than fruits from the lower altitude. After ripening, the higher altitude fruits were firmer and their peel was harder than those of the fruits from the lower altitude. The fruits from the higher altitude had significantly higher total solids, soluble solids, glucose, and fructose contents than the lower altitude fruits

MISE AU POINT SUR LA LUTTE INTEGREE CONTRE LE FLETRISSEMENT BACTERIEN DU A PSEUDOMONAS SOLANACEARUM E.F.SMITH AUX ANTILLES FRANÇAISES

La lutte contre P. solanacearum dans toutes les régions tropicales demeure particulièrement difficile en raison du caractère tellurique et vasculaire de cette bactérie. En Guadeloupe et en Martinique, la lutte a été concue de façon intégrée, en conjuguant les connaissances et ressources acquises en - Pathologie Végétale ; caractérisation et agressivité des souches de race 1 (biovar I et III), détection précoce par ELISA des plants porteurs sains, survie réduite aux potentiels hydriques élevés dans les vertisols de Grande- Terre, - Amélioration des Plantes ; sélection de variétés résistantes de tomate ("Caraïbo") et d'aubergines (familles SAM et SAF), - Agronomie ; diminution de la réceptivité des oxisols par fertilisations azotées (750 uN.ha-1), - Science du Sol ; conséquences de la microstructuration des sols sur l'expression de P. solanacearum. Les recherches menées dans différentes situations pédologiques et agronomiques permettent d'envisager une production régulière. ----- P. solanacearum is a soil-borne and a xylem invading bacterium, therefore it is especially difficult to bring this tropical world-wide disease under control. In Guadeloupe and Martinique we attempted to develop integrated control by joining up knowledges and resources acquired with : - Phytopathology ; characterization and aggressiveness of race 1 (biovar I and 111) strains, early detection of latent infections in tomatoes with an ELISA test, rapid decline of bacteria in natural vertisols (Grande-Terre) when maintained at high water potential, - Plant breeding ; selection of bacterial wilt resistant tomato line (Caraïbo) and family of eggplants (SAM and SAF), - Agronomy ; nitrogen fertilising (750 uN.ha-1) resulted in a considerable decrease of oxysol receptivity to the disease. - Soil science, outcome of soil network on P. solanacearum expression. Experimentations conducted in different pedological and agronomical conditions shows it is possible to obtain regular vegetable productions

Mise en evidence d'infections latentes a Pseudomonas solanacearum E.F.Smith chez la tomate

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Preliminary studies for tomato bacterial wilt (Pseudomonas solanacearum E.F.Sm.) resistance mechanisms

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