Adventitious root formation in anacardium occidentale L. in response to phytohormones and removal of roots

Despite advances in tissue culture techniques, propagation by leafy, softwood cuttings is the preferred, practical system for vegetative reproduction of many tree and shrub species. Species are frequently defined as 'difficult'- or 'easy-to-root' when propagated by conventional cuttings. Speed of rooting is often linked with ease of propagation, and slow-to-root species may be 'difficult' precisely because tissues deteriorate prior to the formation of adventitious roots. Even when roots form, limited development of these may impair the establishment of a cutting. In this study we used softwood cuttings of cashew (Anacardium occidentale), a species considered as 'difficult-to-root'. We aimed to test the hypothesis that speed, and extent of early rooting, is critical in determining success with this species; and that the potential to form adventitious roots will decrease with time in the propagation environment. Using two genotypes, initial rooting rates were examined in the presence or absence of exogenous auxin. In cuttings that formed adventitious roots, either entire roots or root tips were removed, to determine if further root formation/development was feasible. To investigate if subsequent root responses were linked to phytohormone action, a number of cuttings were also treated with either exogenous auxin (indole-3-butyric acid-IBA) or cytokinin (zeatin). Despite the reputation of Anacardium as being 'difficult-to-root', we found high rooting rates in two genotypes (AC 10 and CCP 1001). Removing adventitious roots from cuttings and returning them to the propagation environment, resulted in subsequent re-rooting. Indeed, individual cuttings could develop new adventitious roots on four to five separate occasions over a 9 week period. Data showed that rooting potential increased, not decreased with time in the propagation environment and that cutting viability was unaffected. Root expression was faster (8-15 days) after the removal of previous roots compared to when the cuttings were first stuck (21 days). Exposing cuttings to IBA at the time of preparation, improved initial rooting in AC 10, but not in CCP 1001. Application of IBA once roots had formed had little effect on subsequent development, but zeatin reduced root length and promoted root number and dry matter accumulation. These results challenge our hypothesis, and indicate that rooting potential remains high in Anacardium. The precise mechanisms that regulate the number of adventitious roots expressed, remain to be determined. Nevertheless, results indicate that rooting potential can be high in 'difficult-to-root' species, and suggest that providing supportive environments is the key to expressing this potential. (c) 2006 Elsevier B.V. All rights reserved.

Characterization and PCR multiplexing of polymorphic microsatellite loci in cashew (Anacardium occidentale L.) and their cross-species utilization

Cashew (Anacardium occidentale L.) is the most economically important tropical nut crop in the world, and yet there are no sequence tagged site (STS) markers available for its study. Here we use an automated, high-throughput system to isolate cashew microsatellites from a non-enriched genomic library blotted onto membranes at high density for screening. Sixty-five sequences contained a microsatellite array, of which 21 proved polymorphic among a closely related seed garden population of 49 genotypes. Twelve markers were suitable for multiplex analysis. Of these, 10 amplified in all three related tropical tree species tested: Anacardium microcarpum, Anacardium pumilum and Anacardium nanum.

Penser la strategie de l'Antiquité à nos jours

Déjà utilisé dans un sens large à Byzance au VIe, le terme « stratégie » ne tut adopté en Europe occidentale qu’au XVIIIe siècle. Dans cet ouvrage, l’auteur définit la stratégie est une voie globale pour parvenir à des fins politiques, utilisant la menace ou l’usage effectif de la force et prenant en compte les moyens disponibles, mais aussi les valeurs et les objectifs des adversaires, dans une dialectique des volontés des adversaires. Ces variables sont au centre de cet ouvrage. Depuis Aristote et la notion de guerre juste développée par Augustin d’Hippone et Thomas d’Aquin, jusqu’au « paradigme napoléonien », qui a dominé la stratégie et la guerre à partir de la fin de l’époque moderne, et le concept de la guerre totale de Ludendorff, Béatrice Heuser expose l’évolution d’un discours sur la guerre et sa justification (ou non) comme recherche de la paix. Si, après Napoléon et Clausewitz, la victoire militaire apparaît comme le but ultime de tout conflit, à partir de la Première Guerre mondiale, et surtout de l’utilisation de la bombe atomique en 1945, les stratégistes redécouvrent l’importance de penser la paix après la guerre, le « paradigme de la paix ». Les développements de la stratégie navale, puis des stratégies aériennes et nucléaires, ainsi que les concepts de petite guerre ou de guérilla, qui dominent l’actualité, prennent leur place dans cette histoire de la stratégie, ou « comment les hommes ont pensé la guerre .