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Latex diagnosis is widely adopted in natural rubber-producing countries to optimize the natural rubber production through a physiological-based latex-harvesting system management. This study is the first bibliographical searching and meta-analysis on the variation of latex physiological parameters i.e. sucrose, inorganic phosphorus, thiols, and total solid content. The study used information extracted from 158 scientific papers. Descriptive statistics, agglomerative hierarchical clustering, and principal component analysis were performed to characterize applications of latex diagnosis, how often parameters are used and interpreted as well as the variation of its parameter values. From 158 papers, latex diagnosis parameters were used in 114 agronomy, 22 in physiology, and 22 in breeding papers. The agglomerative hierarchical clustering analysis indicated that sucrose and inorganic phosphorus contents were clustered together and total solid and thiols contents were located in another cluster. The average values of the total solid content, sucrose, inorganic phosphorus and thiols were 43.9%, 9.4 mM, 16.5 mM, and 0.52 mM, respectively. The percentage of interpretation is 63.3% for sucrose, 54.4% for inorganic phosphorus, 47.5% for thiols, and 41.1% for the total solid content. The low interpretation of thiols and total solid contents question their relevance in latex diagnosis. The low adoption of latex diagnosis in breeding could hinder the selection of activities leads to a limitation of selection for long-term high yielding and stress-adapted clones.

Tapping panel dryness (TPD) affects natural rubber production. TPD is associated with clonal susceptibility, overexploitation of rubber trees and environ mental stress. Many studies have been conducted at the histological, physiological and molecular levels based on a binary point of view of the absence or presence of TPD. The dynamic analysis of the TPD onset through the monthly monitoring of the dry eut length revealed the presence of more or less important dry spots on the tapped panel of any trees, while brown bast is associated with a high Level of dry eut length. The content in latex diagnosis components tend to decrease with the occurrence of TPD. The sucrose content value of clones is negatively associated with TPD. The high tapping frequency and stimulation dl ET 12/year is a suitable method for inducing early TPD occurrence. This study suggests using an intensive harvesting system and monitoring of the dry eut length for genetic analysis of TPD.

The purpose of this paper is to present research results relative to impacts of Climate Change on natural rubber production, potential means of adaptation and contribution of rubber to livelihoods resilience to climate change following a recent workshop organized by IRSG in collaboration with CIFOR/FTA, IRRDB and CIRAD. Climate change already impacts rubber production. In some regions longer dry seasons and more variable precipitations threaten the survival of young plants. Rubber has never been planted in areas with an average temperature higher than 28°C; as latex flow after tapping depends on temperature, higher temperatures may have a severe impact on production. Abnormal rains can also disrupt tapping. These modifications will drive a shift of climatically favourable areas. Most pests and diseases affecting rubber are strongly influenced by climate conditions. Climate change is thus likely to modify their distribution and impacts. Without adaptation natural rubber production is projected to decline, in a context of otherwise increasing rubber demand. Three types of adaptation measures can be mobilized: management, breeding, and medium-term planning of plantation renewals and expansion in marginal areas. Management measures include partially shading young plants, mulching them, partial irrigation and life-saving irrigation to address increased risks of drought as well as adopting measures that reduce runoff. Systematic use of rain guards can address impacts of heavy rains on tapping. Better monitoring, prevention and early intervention can reduce damage by pests and diseases. Genomic assisted selection and collection of wild germplasm can support breeding progress towards high yielding, climate resilient and disease resistant clones. Such measures need to be supported by policies promoting the renewal of plantations and changes of practice. As shown by Sri Lanka the National Adaptation Plan (NAP) can offer opportunities to develop an integrated approach to adaptation of rubber to climate change and to contribute to the adaptation of smallholders.

The quest for greater return on investment at short time is a recurring concern of the rubber industry. Early reverse tapping could be an option to this concern. It is therefore to verify this hypothesis that five different stages of initiation of upward tapping, 6th, 7th, 8th, 9th year and the control in 10th year, with application of 2.5 and 5% ethephon was conducted for eight years in the South-East (Bettie) and the Centre-West (Gagnoa) of Cote d'Ivoire. Irrespective of the ethephon concentration used, average yield obtained from upward tapping at 6th year was 3012 ± 516 kg ha-1 y-1 against 2528 kg ha-1 y-1 in the control, where controlled upward tapping started at 10th year with a productivity gain of 19%. The mean annual increase in circumference in the upward tapped trees at 6th year, was 3.02 ± 0.18 cm y-1 and statistically higher than that of the control treatment (2.40 cm y-1). Physiological profiles improved during the experiment, regardless of site and of periods of upward tapping. Generally, the sensitivity to panel dryness in the control is more pronounced than that of early upward tapping. Our results suggest very early upward tapping at 6th year after the 5 years of downward tapping, is the best period to harvest latex from the high tapping panel.

In the global rubber industry, yield gaps between rubber smallholdings and rubber agro-industries are important. These gaps are important regarding land productivity (kg/ha) and even more important regarding labor productivity (kg/tapper/day). However, technical packages of GAP (good agricultural practices) and BMP (best management practices) are available from decades of research in breeding, physiology, agronomy, crop protection and latex harvesting technology. Regarding latex harvesting, the differences between agro-industries and smallholdings are very often even more important than for other disciplines: reduced tapping frequencies compensated by accurate stimulation intensities or controlled upward tapping are scarcely encountered in smallholdings, tapping quality standards are often not respected, regarding bark consumptions, bark wounding, homogenous panel management… conversely to agro-industries. The bottlenecks to introduction of the latex harvesting GAP are multiple. Among them, psychological factors based on fear and risk management and educational factors due to a certain lack of training of smallholders on the parameters accounting for latex production and productivity (tapping quality, opening norms and panel management…). Smallholders are very (too) often on their own during the mature period, from the moment tapping starts. This is rather surprising as the risk is high of non-reversible mistakes during tapping, with non-reversible consequences on the plantation further yields. All efforts granted and services provided during the immature period can then be quickly and easily annihilated by a bad tapping quality or wrong tapping practices. This makes also the latex harvesting GAP and innovations particularly difficult to take on board by the smallholders, because of a rather limited possibility of transfer of technology (TOT). Some other factors are structural: for instance, small size of farms may prevent the possible introduction of reduced tapping frequencies when the tapping taskforce cannot be shared and mutualized among different owners. In latex harvesting, GAP introduction therefore requires to emphasize education and training of smallholders/tappers, so that they can know the possible technical packages that can help them to achieve higher productivity. This supposes that trainers in charge of TOT are themselves updated on the technologies to be transferred. TOT requires as well as to set up demonstration plots or experiments, on-farm and with a participative approach, in candidate leader smallholders farms accepting to test the possible innovations and GAP, so that “everybody can see the results” and afterwards take them on board in a spontaneous manner (“If it good for my neighbor, it should be good for me as well”). This communication presents the Cirad experience on this subject.

In Cambodia, the common tapping system which was widely adopted by smallholders and agro-industry plantations was S/2 d3 for downward tapping and S/4 d3 for upward tapping. However, under the decline of rubber price and increasing labor shortage, the application of low frequency tapping systems (LFT) may be a choice to solve these problems. Hence, different low frequency tapping systems were tested in traditional area of Cambodia. An experiment was established using seven-year old rubber trees of RRIM 600 clone at the Cambodian Rubber Research Station located in Tbong Khmum province. The experimental design was Randomized Complete Block Design with four treatments: T0: S/2 d37d/7 ET 2.5% 4/y, T1: S/2 d4 7d/7 ET 2.5% 5/y, T2: S/2 d5 7d/7 ET 3.3% 6/y and T3: S/2 d6 7d/7 ET 3.3 % 10/y comprising three replications (12 elementary plots). There were 120 trees per treatment in each elementary plot. After 3 years of tapping, LFT system S/2 d6 with Ethephon application (T3) provided the highest dry rubber yield per tree per tapping (g/t/t) but the lowest yield in gram per tree (g/t) and kilogram per hectare (kg/ha). As compared to d3, LFT systems (d4, d5 and d6) caused dry rubber yield loss in kg/ha by respectively 3, 9 and 11% but resulted in increased labor productivity (g/t/t) by respectively 11, 28 and 48%. Therefore, the increase in labor productivity (g/t/t) was higher than the loss in land productivity (kg/ha). Girth increment was not significantly different between treatments. Sucrose and reduced thiol contents of all treatments were not significantly different but inorganic phosphorus content was significantly different depending on the tapping system. Tapping panel dryness was similar for all treatments after three years of tapping.

The purpose of this study was to assess tapping systems to decrease tapping frequency with stimulation in order to increase yield per day and tapper productivity. This experiment was set up in Chachoengsao Rubber Research Center since 2016. Experimental design was a Split plot comprising 4 replications. 3 main treatments are clones (RRIT 251, RRIM 600 and PB 235) and 4 sub-treatments are tapping systems ( S/2 d2, S/3 d1 2d3, S/2 d3 ET2.5% without recovery of lost tapping days and S/2 d3 ET2.5% with recovery of lost tapping days). Three years of tapping showed that RRIT 251 and PB 235 increased yield by 62% and 27% in comparison with RRIM 600. Regarding sub-treatments, S/2 d3 ET2.5% and S/2 d3 ET2.5%with recovery of lost tapping days could increase productivity per day (g/t/t) by 18-23%. Yield in term of kilogram per tree per year was not significantly different among tapping systems. Tapping days in d3 were only 71-81 days per year and less than for d2 and d1 2d3 with 107 and 138 tapping days per year respectively.

Fertilization is one of the most important factors that affect growth and yield of rubber tree. It takes a high rate of capital investment for plantation. Regulation on fertilizer quantity or/and ratio among fertilizer nutrients results in remarkable economical and technical impacts on the rubber plantation during the immature period. During the mature period, data are still controversial. This experimental study aimed to evaluate the effects of fertilizer on the rubber growth in immature stage. After seven years of experimentation, results showed that fertilization had a positive effect on the cumulative girth increment (cm) by 6% whereas the tapped rubber trees at opening increased by 7 to 13%.

Yield gaps between rubber smallholdings and rubber agro-industries often exist. These gaps are usually important regarding land productivity (kg/ha) but even more important regarding labor productivity (kg/tapper/day). However, technical packages of GAP (good agricultural practices) are available from decades of research in breeding, physiology, agronomy, crop protection and latex harvesting technology. Regarding latex harvesting, the differences between agro-industries and smallholdings are very often even more important than for other disciplines. Reduced tapping frequencies compensated by accurate stimulation intensities or controlled upward tapping are scarcely encountered in smallholdings. Other quality standards are also often less respected, mainly regarding bark consumption, bark wounding and homogenous panel management. In Thailand, smallholders own 85% of the total rubber area. In the southern and eastern regions of the country, climate conditions with heavy rains during the rainy season, associated with rubber price fluctuation, lead farmers to use high frequency tapping systems (S/3 d1 2d/3 or S/3 d1 3d/4 mainly) in order to compensate the reduction of the number of tapping days due to rains. Labor shortage is also a new and increasing issue for farmers who hire tappers. To improve labor productivity in each farm and address the increasing labor shortage, one way might be to reduce the time spent by tappers in the field, using low frequency tapping systems (LFT). LFT systems combine reduction of tapping frequency with Ethephon stimulation. Under accurate stimulation, yield significantly improves at each tapping, leading to a higher labor productivity (g/t/t and kg/tapper/day) and this can at least partly compensate the effect of the reduction of the tapping frequency on production. The objectives of this publication are (i) to assess the efficiency of different LFT systems with Ethephon stimulation on yield, labor productivity and latex physiological parameters and (ii) to select among those systems the ones showing an improved efficiency regarding labor productivity, in order to test them on farm.

A meta-analysis of the Latex Diagnosis (LD) database gathering all LD data stored from 2006 to 2018 in SIFCA/SIPH plantations of Côte d'Ivoire (SAPH), Ghana (GREL) and Nigeria (RENL) has been performed. Average clonal LD data comprising Sucrose (Suc), Inorganic Phosphorus (Pi), Reduced Thiols (RSH) and latex Total Solid Content (TSC) were analyzed and compared for different plantation sites of SAPH (Toupah, Ousrou, Bongo, Rapides Grah, Digahio, Divo and Bettie), GREL (Abura) and RENL (Osse River, New Land, Utagba Uno, Araromi, Waterside and Iguobazuwa). The database was filtered in order to keep only the LD data obtained either from conventional and standard tapping systems (S/2 downward and S/4 upward), excluding the intensified period before slaughtering. Data were processed and analyzed on clones GT1, RRIM600, PR107, AV2037, RRIC100, AF261, PB5/51, PB217, PB235, PB260, PB312, PB314, IRCA18, IRCA41, IRCA109, IRCA111, IRCA130, IRCA209 and IRCA230. All clones were tapped either in d4 or d5 6d/7 tapping frequencies. Stimulation was applied on panel (Pa), under industrial stimulation rates adapted to each clone metabolism and clonal sugar loading characteristics. Based on the relation between Suc and Pi, the analysis of these LD data confirms the latex physiological positioning in clonal typology of all clones. It confirms in particular the high latex sugar loading capacity of clones PB217 (as this clone obtains the highest latex Suc level whatever the plantation site), IRCA109, IRCA41 and IRCA230. It also reveals a systematic positive correlation for all sites between RSH and Suc latex contents: Clones with high latex Suc maintain higher RSH latex concentrations than clones with lower Suc, confirming at industrial scale earlier research results. The physiological hypothesis is that a high clonal latex sugar loading, allowing higher stimulation rates and improved stimulation response, would as well maintain higher latex RSH levels resulting in an improved resistance to oxidative stress resulting from latex metabolic activation. This improved scavenging protection would therefore have positive effects on membranes integrity, on latex stability, on latex flow and on tapping panel dryness (TPD) onset. Moreover, as tapping intensity (tapping frequency and stimulation) was almost similar in all sites, we also make the hypothesis that the latex RSH level and the Pi x RSH value might be accurate indicators to describe, at plantation site level, the local clonal suitability as well as the global stress conditions of trees on each plantation site. This study will be completed later on in order to set up a standard interpretation method of such LD databases.

Agriculture is currently in transition, as it has to face different global challenges such as climatic change, transitions to new cropping areas and enhanced environmental awareness of the society. Economic development also results in drastic changes in labor structure, availability and cost. Research has therefore more topics to address than in a recent past, requiring more and more multi-disciplinary research approaches to take into account this increasing complexity. For instance, setting up “Good Agricultural Practices” (GAP) or Climate Smart Agriculture (CSA) for ensuring crop sustainability in such a changing environment (climate, soils, environmental and social changes) must address simultaneously the social, environmental and productive aspects. Linear vertical proposal of practices is unlikely to be adopted by stakeholders and relies now on prior dialogues between all stakeholders (producers, transformers, buyers, NGOs, civil society…) under much more participative approaches, in order to get a better understanding of the rationale (priorities and constraints) of all stakeholders involved in the value chain. Regarding the rubber tree, climatic, economic, environmental and social changes in the value chain already had and will have in the future stronger and stronger impacts on the commodity and therefore on the research to set up to address planters, processors and also end-users priorities and constraints. Already, the production of the land (kg/ha) is not anymore, in most of rubber producing countries, the most important yield parameter, as availability or cost of the tapping manpower has already become the most important production limiting factor. The recent raise in environmental awareness of the society and the raise of new environmental norms (FSC, SNRI…) also modify the production conditions in an ecological way. Decrease of inputs like pesticides or fertilizers, respectively judged responsible for health issues or pollutions, leads to the need to develop a “cleaner” agriculture based on the principles of agro-ecology but maintaining the yield performances. Economic resilience to commodities price fluctuations has also to be in front of research priorities. Research has therefore to be structured in order to coordinate all scientific disciplines (molecular physiology and genomics, plant physiology, ecophysiology, agronomy, pathology and crop protection, climatology and soil science, technology and processing, socioeconomics and environmental impact assessment) to propose integrated optimized practices adapted to all stakeholders of the value chain and to address those challenges.

This report is to complete the terms of reference of the project signed between General Directorate of Rubber (GDR/MAFF, Kingdom of Cambodia) and Cirad on 22 June 2018 and called “Implementing Good Agricultural Practices (GAP) in Cambodia for a Climate Smart Rubber Production: Training sessions”, under a funding provided by Agence Française de Développement (AFD). A seminar was organized by GDR from 19 to 22 June 2018 in GDR head office in Phnom Penh, followed by a visit of Cambodian Rubber Research Institute (CRRI) experimental station in Tboung Khmum Province on 23 June 2018. The document report addresses 5 terms of reference, as stated in the contract: • TOR1. A reminder of the definitions of the concepts of Good Agricultural Practices (GAP) and Climate Smart Agriculture (CSA). • TOR2. A reporting of the activities of Cirad in each area of expertise: Agro-socioeconomics (Dr Bénédicte Chambon), agrophysiology and agronomy (Dr Eric Gohet and Dr Régis Lacote), ecophysiology (Dr Yann Nouvellon), soil fertility management and crop diversification (Dr Florent Tivet), focusing mainly on capacity building in each area. • TOR3. A drafting of a GAP (Latex harvesting system) manual, understandable by farmers. • TOR4. Proposed supporting experimentation (managed by CRRI) • TOR5. Proposals for a long-term cooperation between the three partners of the project (GDR, CRRI and CIRAD) for tackling the adaptation of rubber cultivation to the different rubber cultivation areas of Cambodia, taking into account the diversity of socioeconomic contexts.

The relationship between tapping systems and the balance between latex production and carbohydrate availability would be very informative. This present work aims to study the effects of tapping systems on enzyme activities involved with Non-structural carbohydrates (NSCs) dynamic. The result indicated that enzyme activities from RR IM600 with upward tapping was higher from that of downward tapping. This could be partly due to the gradient sucrose along the t ruck as it is more concentrated in higher position than the lower one. Sucrose synthase was proportional to sucrose content in bark of upward tapping. Meanwhile, Sucrose Phosphate Synthase and Amylase were higher in wood than bark. These enzymes were also significantly higher in upward tapping than downward tapping. Using immunolocalization test, amylase was located in both vascular rays of bark and wood. It was noticed that enzyme activities strongly related to sucrose content while the link with starch content could not be clarified yet. To eventually explain the whole picture of NSC balance and latex production, information of latex production yield and enzyme involved in starch synthesis must be taken into account.

This study was carried out in the CRRI research station in Thbong Khmom province. The objective of the experiment was to investigate the yield potential for tapping system S/2 d4 7d/7 of the clone IRCA 230, by comparing and identifying optimum stimulation frequencies of d4 tapping frequencies of the downward half spiral cuts in both panels BO-1 and BO-2 and quarter spiral cut in panel H0-1. Intensity of stimulation was modulated according to clonal characteristics. During the physiological year 2005-2015, trees were tapped on downward panel and in year 2015-2016, trees were tapped in upward tapping. The result of yield in g/tree/tapping (g.t-1.t-1), g/tree (g.t-1) and kg/ha (kg.ha-1) showed higher the rate of hormonal stimulation, higher the yield. Regarding the specific last year of tapping on panel BO-2, which could estimate the yield capacity of the clone, IRCA 230 still showed the highest production under the highest tested rate of ethephon stimulation. Meanwhile, Suc content was slightly lower than that of the other treatments. At the same period, the relationship between Pi content and yield (g.t-1) indicates that the main effect of ethephon stimulation was on the metabolic activity itself, leading to increased yield in comparison to the other treatments.

In the global rubber industry, yield gaps between rubber smallholdings and rubber agro-industries are important. These gaps are important regarding land productivity (kg/ha) and even more important regarding labor productivity (kg/tapper/day). However, technical packages of GAP (good agricultural practices) and BMP (best management practices) are available from decades of research in breeding, physiology, agronomy, crop protection and latex harvesting technology. This paper lists the principles of Rubber GAPs, details the bottlenecks regarding their transfer to smallholders and explains Cirad strategies to favor the efficiency of GAP transfer of technology (TOT) to the rubber smallholders, based on Cirad experience in different rubber producing countries.

In the global rubber industry, yield gaps between rubber smallholdings and rubber agro-industries are often important. These gaps are important regarding land productivity (kg/ha) and even more important regarding labor productivity (kg/tapper/day). However, technical packages of GAP (good agricultural practices) and BMP (best management practices) are available from decades of research in breeding, physiology, agronomy, crop protection and latex harvesting technology. This paper lists the principles of Rubber GAPs, details the bottlenecks regarding their transfer to smallholders and explains Cirad strategies to favor the efficiency of GAP transfer of technology (TOT) to the rubber smallholders, based on Cirad experience in different rubber producing countries.

The purpose of this study was to assess double cut alternate latex harvesting system (DCA) over a 15-years tapping period on clone RRIM600. This experiment was set up in Chachoengsao Rubber Research Center since 1999. Experimental design was a RCB comprising 4 replications with 6 treatments: A; S/2 d2, B; S/3 d2 ET2.5% 4/y, C to E; S/2 d3 ET2.5% 4, 6 and 8/y and F; DCA ((2xS/2 d2 (t,t)). Yields in g/t/t of S/2 d3 ET2.5%, 4-8/y were the highest with more 36-44% of the control S/2 d2. But yield in term of kg/tree/year and kg/ha/year were lower than the others tapping system. Over a period of 15 years, compared to a single cut tapping system (S/2 d2) of equivalent intensity, DCA increased cumulative rubber production by 9%. DCA, S/2 d2 and S/3 d2 ET2.5% 4/y also resulted in higher TPD rates than S/2 d3 ET2.5% 4, 6 and 8/y.

En la cadena productiva global del caucho, se observan diferencias importantes de rendimiento entre las pequeñas plantaciones y las agroindustrias de caucho, en particular por lo que se refiere a la productividad de la tierra (kg/ha) y la productividad del trabajo (kg/hombre/día). Sin embargo, los paquetes tecnológicos de las buenas prácticas agrícolas y de manejo existen, resultados de varias décadas de investigación en mejoramiento genético, fisiología, agronomía, protección fitosanitaria y tecnología de recolección de látex. Esta situación se debe a un déficit de transferencia de tecnología, aún más agudo al momento de iniciar la sangría de los árboles. Existen múltiples cuellos de botella que no permiten una buena transferencia de tecnología hacia los pequeños productores. Entre ellos, los factores psicológicos basados en el miedo y el mane jo del riesgo ("La estimulación matará a los árboles"...) y la falta de capacitación con respecto de los parámetros de producción y de productividad (normas de calidad de sangría, manejo del panel, etc). En realidad, la mayoría de los servicios de asesoría y de extensión se concentran en el período inmaduro (subsidios y asesoramiento para la provisión de clones, la siembra, la fertilización.. .), pero los pequeños productores a menudo se quedan solos durante el período maduro, cuando empieza la sangría de los árboles. Esto hace que el riesgo de cometer errores durante la explotación es alto, con consecuencias irreversibles sobre el potencial de producción futuro de la plantación. Todos los esfuerzos otorgados y los servicios prestados durante el período inmaduro pueden ser aniquilados rápida y fácilmente por prácticas inadecuadas y una mala calidad de la sangría. Algunos factores son estructurales, por ejemplo el tamaño pequeño de las plantaciones puede impedir la posible introducción de frecuencias reducidas de sangría cuando el grupo de rayadores no puede ser compartido y mutual izado entre diferentes propietarios. En la sangría, la introducción de las buenas prácticas agrícolas requiere por lo tanto enfatizar la capacitación de los pequeños productores y rayadores, para que puedan conocer los posibles paquetes tecnológicos que les ayudaran a obtener una mayor productividad. Esto supone que los capacitadores a cargo de la transferencia de tecnología sean actualizados sobre las tecnologías a transferir. La transferencia de tecnología requiere también establecer parcelas de demostración, con un enfoque participativo, en las plantaciones de agricultores candidatos que acepten de probar las posibles innovaciones y las buenas prácticas agrícolas, para que todos puedan ver los resultados y luego apropiárselas de manera espontánea. Pero no puede haber una recomendación universal; hay que conocer previamente la tipología de los agricultores para poder dar una recomendación técnica adaptada a cada tipo de agricultor.

El mejoramiento genético y los logros alcanzados en las técnicas agronómicas y de explotación del árbol de caucho han permitido, en el lapso de un siglo, multiplicar por cinco la productividad de las plantaciones de caucho. La estimulación hormonal con Etefon ha permitido también mejorar la productividad del trabajo, compensando la reducción de la frecuencia de sangría. Para no sobrepasar el potencial de producción del clon de caucho, y evitar su fatiga fisiológica, se requería conocer el metabolismo propio de cada clon. El Diagnostico Látex (DL) ha permitido establecer una tipología clonal, la cual es en una combinación entre el metabolismo propio de la célula laticífera y la cantidad de reservas en azúcar de la misma. Los clones de caucho están clasificados en 15 categorías posibles, dependiendo de su reserva en sacarosa y de su metabolismo, el cual se puede activar de cierta intensidad con la estimulación. El DL permite monitorear la explotación de las plantaciones de caucho, para cada tipo de clon utilizado, y manejar de manera optimizada el sistema de sangría mejor adaptado a las condiciones de cada plantación. El DL es considerado por el CIRAD y la mayoría de sus socios agroindustriales como una herramienta fisiológica de rutina para optimizar, la productividad de caucho en bloques homogéneos de plantaciones comerciales. Sin el uso del DL, generalmente se aplica una recomendación global de un sistema de sangría y estimulación para un clon, sin conocer el potencial real de producción que puede haber localmente. Aun que esta recomendación general se basa en características fisiológicas clonales del látex, no se toman en cuenta las especificidades locales del potencial productivo, es decir los factores locales como la heterogeneidad del suelo, las variaciones micro climáticas en las grandes plantaciones, ni las enfermedades (hojas, raíces...). En este caso, las plantaciones se manejan sin saber cuál es la idoneidad de la intensidad de la estimulación aplicada. Una aplicación uniforme de la misma dosis de estimulante en todas las unidades culturales homogéneas puede en ciertas ocasiones conducir a una explotación óptima, o a una sub-explotación en las áreas donde existe un mayor potencial de rendimiento, o a una sobre-explotación en zonas de menor potencial productivo. El uso del LD permite optimizar la estimulación a nivel local (disminución de la estimulación cuando se detecta una sobre-explotación, aumento de la intensidad de la estimulación si se detecta una sub-explotación), y por lo tanto permite optimizar la producción bloque por bloque, tomando en cuenta la heterogeneidad de las plantaciones y por lo tanto, el real potencial de rendimiento local. Por supuesto, la interpretación del DL depende de los valores de referencia de los 4 parámetros del DL, los cuales son clonales y obtenidos previamente: los contenidos en sacarosa del látex (Suc), en fósforo inorgánico (Pi), en Thioles reductores (RSH) y el DRC/TSC. Estos valores de referencia se establecen para cada uno de los parámetros del DL, y por cinco niveles (muy bajo, bajo, normal, alto y muy alto), ya sea a escala regional o en caso de grandes plantaciones, a escala de cada plantación cuando la base de datos de los parámetros DL locales lo permite. (Texte intégral)

The purpose of this study was to characterize affect of DCA (double cut alternate tapping system) on renew bark and TPD (tapped panel dryness) symptom with RRIM 600 clone. This expriment was set up in Chachoengsao Rubber Research Center since 1999. Experimental design was RCB comprising 4 replications with 6 treatments: I). S/2 d2, 2). S/3 d2 ET 2.5% 4/y, 3-5). S/2 d3 ET 2.5% 4, 6 and 8/y and 6). DCA ((2xS/2 d2 (t,t)). The 2"d phase focus on l l -l 5th tapping year. The results show yield of DCA and S/3 d2 ET 2.5% 4/y were 1,760 and 1,819 kg/ha/year or higher 12% and 16% than S/2 d2 consequence. However, S/2 d3 ET 2.5%, 4-8/y were the highest average yield 36-44% but yield in term of kg/tree/year and kg/ha/year were lower than the others tapping system 15%, according to less tapping days than 32 days in comparison with d2. Over a period of 15 years, compared to a single cut tapping system (S/2 d2) of equivalent intensity, DCA increased cumulative rubber production by 10%. DCA, S/2 d2 and S/3 d2 ET 2.5% 4/y also resulted in higher TPD rates 33-34% than S/2 d3 ET 2.5% 4, 6 and 8/y which occurrence 19-24%.

Most of natural rubber (NR) comes from the cultivation of Hevea brasiliensis in tropical countries. However, mainly due to land use changes (urbanization, substitution...),new rubber plantation developments are often moving to climatically less favorable areas (usually called "marginal" areas or "non-traditional" areas). These new planting areas are often characterized by one or more climatic factors considered as less favorable to rubber tree cultivation. Howevern it is still a challenge to estimate exante and accurately the effect of such climatic stresses on the rubber yield potential. For this purpose, we propose a tentative multilinear regresstion model, using climatic parameters commonly available from local weather stations (total annual rainfall (mm), average thermal amplitude), in order to calculate a composite climatic marginality index for rubber tree cultivation (CCMIndex). Such CCMIndex could be used exante to provide an early evaluation of the expectable loss in rubber yield potential due to climatic marginality in any nex rubber planting area. It should also allow to discriminate among climatic types (climatic typology with 4 main types: warm/humid, warm/dry, cold/humid and cold/dry) and to quantify their respective climatic stress intensity. The CCM index could be used to adapt latex harvesting systems recommendations per climatic typeafter the type and the intensity of the climatic marginality have been descripted and quantified. Another index, based on dry months distribution along the year, can provide complementary information to describe the risk of occurrence of secondary leaf fall due to leaf diseases (SLF Risk Index). Combining the CCM index and the SLF Risk index could likely provide an accurate and simple estimate of the overall effect to climate on NR yield potential in any NR production area. Moreover, in a general context of climatic change, these two indexes might be used simultaneously to simulate the possible effect of future variations in temperature and rainfall intensity or pattern resulting from climatic changes on the future rubber yield potential of any current or future NR production area, at local, regional, national or global scales. This communication presents the current status of the model, which may be regularly upgraded depending on data accumulation improving the model parameterization.

Tapped trees from 19 clones (CDC56, CDC308, CDC3 l 2, CDC429, FDR446 l, FDR4575, FDR5240, FDR5283, FDR5597, FDR5665, FDR5788, FDR5802, MDFl80, MDX607, MDX608, MDX624, PMB 1, SIAL893 and TP875) showing good tolerance to SALB (South American Leaf Blight) have been studied for their latex physiological parameters from 2007 to 2011 on Plantation Michelin Da Bahia (PMB). Igrapiuna, Brazil. Main latex physiological parameters (sucrose latex content, inorganic phosphorus latex content, reduced thiols latex content and latex DRC) have been recorded from 3 large scale clone trials, with or without ethephon stimulation. Without stimulation, latex analysis results show clear discrimination between the clones for their latex metabolic types, from very low to high latex metabolism. The clones showing the most interesting physiological characteristics (medium to high metabolism together with higher latex sucrose content) are FDR4575, FDR5788 and PMB l. These 3 clones are likely to obtain the highest yield potentials among the selection. 3 other clones (MDX608, CDC308 and FDR446 l) show high metabolism with lower sucrose content, showing typical quick sta1ter profiles. Finally, 5 other clones (FDR5240, TP875, CDC429, CDC3 l 2 and FDR5665) show typical medium metabolism profiles. Ali other clones show some physiological limitations due either to their low latex metabolism, either to their low latex sugar content. With stimulation, latex parameters variability among clones is greatly reduced, making it difficult to discriminate clones profiles. This confirms that ethephon stimulation is not helping in the evaluation of clonal latex physiological characteristics. From this early clonal physiological characterization, a tentative optimum stimulation range can be proposed for each of the 19 clones tested in these trials.