Achievements and problems in the implementation of microcutting technology for clonaI rubber rootstock propagation

Microcutting is one of in vitro plant propagation methods and has been developed for rubber (Hevea brasiliensis) by using axillary buds from young seedlings as explant sources. There are some constraints to implement microcutting technology in mass propagation of Hevea such as high level of contamination, low proliferation rate, poor rooting, and difficulty in acclimatization process. Achievements and problems in the implementation this technique in Indonesia will be reported in this paper. Around 19.000 explants from 89 genotypes have been introduced in primary culture for almost 3 years (2006-2008), 40% of them loss during this stage due to contamination and no response of the explants. All healthy and good response explants had been transferred to multiplication phase. The multiplication rate was 1.3 to 1.6 per month for the best genotypes. In 2007 and 2008, around 6.000 new shoots had been introduced to conditioning phase, 80% of them have continued to rooting phase. These two stages produced about 4.000 plantlets which were then acclimatized to ex vitro conditions on different media and micro-environments. The suitable medium for vitroplants acclimatization was a mix of cocopeat, soil, sand and dung manure. Better growth and survival rate were achieved when the vitroplants were cultured inside a closed plastic tunnel placed under tree canopies. The survival rate of vitroplants, 1.5 month after weaning, has increased to 60% but still fluctuated and only 15% in average after 6 months. The survived plants with good root systems were then transferred to a shading nursery. Vitroplants and GT 1 seedlings were planted in the field for 7 months before budded with scions of PB 260 clone. All rootstocks from vitroplants and GT 1 seedlings were successfully budded with scions of PB 260. At present, budded and unbudded vitroplants are being planted in the field. (Résumé d'auteur

The rootstock clones in rubber tree: a new varietal type toward the rejuvenated bi-clone

Cloning rubber rootstocks by microcutting will remove the genetic variability of the seedling rootstocks; Moreover, it will open the way to the breeding of rootstock clones regarding main challenges as the growth-vigor of the trees, the water stress tolerance or the root diseases tolerance. In other respects, using rejuvenated selected clones for budding will counteract the weakening effect of ageing. The conventional rubber clones are two-parts trees built up by budding mature budwood of selected clones [trunk and canopy] on unselected and uncloned seedling rootstocks [root system]. Outputs from biotechnology on Hevea brasiliensis, make it possible now to create the "rejuvenated biclone" associating a new rootstock clone A with a rejuvenated budded clone B. Such "bi-clone" will allow to optimize each part of the tree and their specific interaction; thus making the propagation more reliable and with higher quality regarding growth and rubber yield. This paper gathers laboratory and field data which grounded this project. The cloning of young seedlings by microcutting was previously defined by the CIRAD team in France since 1988 and more than 50.000 vitroplants were produced then. Field development of such self-rooted vitroplants was analysed at the CNRA research centre, in Ivory Coast, during ten years for growth and rubber yield. Results give evidence for the conformity of the root system and for the vigorous development of these trees which could have been used as clonal rootstocks. Work in progress with Michelin shows that rejuvenated budded clones, issued from primary somatic embryogenesis, display higher growth speed than the conventional mature clones. Currently, the IBRIEC and IRRI teams, in Indonesia, are successfully implementing the same microcutting process. The first "bi-clones" have been built and planted at Bogor early in 2008, showing the feasibility of it. (Résumé d'auteur

Extruded and injection moulded virgin PA 6/6 as abrasion resistant material

Polyamide (PA6/6) is often used as a tribological pair in abrasion prevalent applications such as hinges and sliders. PA6/6 is frequently processed by injection moulding and extrusion process. It is known that these processes influence the polymers mechanical behaviour, but their influence on the polymers wear response has not been studied. Hence the present research attempts to study the influence of different manufacturing processes on tribological behaviour for PA6/6. Wear tests were performed on a pin abrading tester (DIN 50322). Abrasion resistance of both extruded and injection moulded PA6/6 were tested at different loads (20 and 35 N). Single-pass (nonoverlapping mode) and multipass testing (overlapping mode) were used to understand the influence of clogging of wear debris. It is evidenced that with increasing load the specific wear rate decreases; moreover, fine abrasives tend to reduce the wear rate. In multipass testing a transfer layer clogged on the counterface that acted as a protective agent and lowers wear rate. Poor mechanical strength of injection moulded polymers is apparently compensated by microstructural response for having a similar wear behaviour between extruded and injection moulded PA 6/6. Hence a proper balance between microstructural and mechanical characteristics is an absolute must in PA 6/6 for better wear performance

Integration of biotechnologies for rubber tree improvement. What about rootstock clones ?

Breeding and dissemination of planting material for rubber plantations are closely linked to propagation methods. Since the progress made by shifting from multiplication by seed to propagation by budding, the development of new techniques, such as micropropagation, has been awaited. New varietal types such as self-rooted plants, rejuvenated budded clones, genetically modified organisms, and rootstock material were developed from microcutting and somatic embryogenesis techniques at the research level. The development of rootstock clones adapted to the selected scion clones is likely to be the most promising approach to improve significantly rubber tree for various agronomical traits such as tree growth, tolerance to wind damage, root diseases and drought conditions. Both the recalcitrance to micropropagation techniques and the long-term process of evaluation and clone recommendation have hampered rapid progress in rubber tree, but nowadays, new research advances have to be considered. The root architecture modelling, genomics and post-genomics approaches, molecular breeding have been integrated to optimize the prediction in genetic improvement programme of several estate crops like oil palm. The integration of biotechnologies for rubber tree improvement must be considered to accelerate the development of rootstock material. That will be decisive for assessing the degree to which new technologies are taken on board in modern rubber growing. The involvement of growers and agro-industrialists. (Résumé d'auteur

Hevea rootstock clones development. Building-up new verietal type : a multi-faceted challenge

With rubber trees occupying about 3.2 million hectares in Indonesia in 2006, the need for planting material from nurseries is rapidly increasing: more than 30 million plants for 2007. Nurseries can hardly manage to provide recommended seedling progenies as rootstocks. Propagation of clonal rootstocks through in vitro microcuttings could be an alternative way. The development of rootstock clones is a multi-faceted challenge. (Résumé d'auteur

Peluang aplikasi stek mikro (Microcutting) untuk perbanyakan batang bawah klonal pada tanaman karet

Clonal propagation with budding system through grafting buds from scion onto rootstocks is the usual way for rubber (Hevea brasiliensis, Muell. Arg.) propagation. Scions with good characters were obtained through breeding program and then propagated clonally, while rootstocks usually in form of seedling material due to the lack of an appropriate multiplication technique. In fact, the used of seedling as a rootstock, face on some constrains such as limited seeds due to seed season and suitable clone as a source of seeds. Besides, seedling will produced un-uniform rootstock which significantly influenced production loss as a cause of growth inferiority of scion as well as of incompatibility between scion and rootstock. Clonal propagation of rubber plant through microcutting technology which based on in vitro culture had been started at CIRAD (France) since 1980. Recently, CIRAD has completely mastered all process in rubber microcutting technique and proved the produced plants developed taproot and lateral root system in the field. In two first year tapping, the production of microcutting plants were 20% higher (kg dry rybber/tree) than those from conventional one. It seems that microcutting will be a new way to propagate clonal material of rubber plant. Since 2005, a research collaboration had been started by three parties, including Indonesian Biotechnology Research Institute for estate Crops (IBRIEC), Indonesian Rubber Research Institute (IRRI) and French Agricultural Research Centre for International Development (CIRAD). The aim of this collaboration is to adapt and to implement microcutting technology based on Indonesian environment and plant materials. The feasibility to implement microcutting technique depend on the succesful to overcome some constraint which usually face in this technique, such as high level of contamination especially in primary culture stage, difference response of plant materials to culture environment, and high level of death plant during acclimatization process. This paper summarizes some research progress on rubber microcutting and some results from collaborative research to show the possibility of their application in propagation of clonal rootstock in rubber plant. (Résumé d'auteur

Use of Sheet Material for Rapid Prototyping of Cardiovascular Stents

Manufacturing of cardiovascular stents most commonly involve the use of tubular precursors and laser microcutting of the stent mesh, followed by chemical and electrochemical surface treatments. For mass manufacturing purposes, this production route is well-established, while for small batch or prototype production it proves to be cumbersome. Especially concerning newly developed alloys based, the production of microtubes is time consuming and highly costly. On the other hand, production of these new alloys in sheet metal form is a simpler approach, since the process uses non-dedicated tools and is easier as opposed to extrusion and tube drawing. Accordingly, in this work, the use of sheet material as precursor for rapid prototyping of cardiovascular stents is proposed. In particular, a ns-pulsed fiber laser is used for cutting permanent AISI 316L. Laser microcutting conditions are investigated in terms of generated spatter and kerf geometry. Chemical etching is employed to clean the dross generated around the cut kerf. A novel stent geometry allowing for transforming the sheet material to a tubular form is employed to produce prototype stents

Comparative study of CW, nanosecond- and femtosecond-pulsed laser microcutting of AZ31 magnesium alloy stents

Magnesium alloys constitute an interesting solution for cardiovascular stents due to their biocompatibility and biodegradability in human body. Laser microcutting is the industrially accepted method for stent manufacturing. However, the laser-material interaction should be well investigated to control the quality characteristics of the microcutting process that concern the surface roughness, chemical composition, and microstructure of the final device. Despite the recent developments in industrial laser systems, a universal laser source that can be manipulated flexibly in terms of process parameters is far from reality. Therefore, comparative studies are required to demonstrate processing capabilities. In particular, the laser pulse duration is a key factor determining the processing regime. This work approaches the laser microcutting of AZ31 Mg alloy from the perspective of a comparative study to evaluate the machining capabilities in continuous wave (CW), ns- and fs-pulsed regimes. Three industrial grade machining systems were compared to reach a benchmark in machining quality, productivity, and ease of postprocessing. The results confirmed that moving toward the ultrashort pulse domain the machining quality increases, but the need for postprocessing remains. The real advantage of ultrashort pulsed machining was the ease in postprocessing and maintaining geometrical integrity of the stent mesh after chemical etching. Resultantly, the overall production cycle time was shortest for fs-pulsed laser system, despite the fact that CW laser system provided highest cutting speed

Biodegradable magnesium coronary stents: Material, design and fabrication

Biodegradable cardiovascular stents in magnesium (Mg) alloys constitute a promising option for a less intrusive treatment, due to their high compatibility with the body tissue and intrinsic dissolution in body fluids. The design and fabrication aspects of this medical device require an integrated approach considering different aspects such as mechanical properties, corrosion behaviour and biocompatibility. This work gathers and summarises a multidisciplinary work carried out by three different research teams for the design and fabrication of Mg stents. In particular, the paper discusses the design of the novel stent mesh, the deformability study of the Mg alloys for tubular raw material and laser microcutting for the realisation of the stent mesh. Although, the results are not fully validated as the device has not been fully tested, they show the feasibility of the used approaches, as the first prototype stents in Mg alloy were produced successfully. © 2013 Copyright Taylor and Francis Group, LLC