Characterization of the potential yield of clone IRCA230

The experiment on Yield Potential Comparison on S/2 d3 and S/2d4 Tapping Systems of Clones IRCA230 were practiced on farm research at Chup Rubber Research Station of Cambodian Rubber Research Institute (CRRI). The experimental design was the RCBD with 8 treatments and 4 replications with a total number 400 trees per replication. They were opened at the standard girth of 50 cm measured at 1m high. All the trees were opened at 1.3 m from the ground. The tapping systems were S/2 d3 7d/7 and S/2 d4 7d/7. This clonal typology is based on measurements issued from the latex diagnosis. The objective of the experiment was to investigate the yield potential comparison of the tapping system S/2 d3 7d/7 and S/2 d4 7d/7 based on frequency of ethephon stimulation. Stimulation was related to the sucrose and inorganic phosphorus contents of the latex cells. Clone IRCA 230, with higher sugar content, with high ethephon stimulations per year obtained the highest yield. The cumulative yield in gram per tree over 8 years of tapping showed frequency d3 higher yield than frequency d4. The yield of tapping frequency with stimulation 1.5% 7/y control was higher than them. (Résumé d'auteur

Performance of different latex harvesting systems to increase the labor productivity of rubber plantations in Thailand

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

QTLs detection for growth and initial latex production in rubber (Hevea brasiliensis)

The objective of this study was to analyse the genetic determinism of growth and latex production in rubber tree by a QTL approach. The plant material consisted of 196 progenies derived from the F1 family RRIM600 x PB217. A genetic linkage map was built for this family with 229 SSR markers (microsatellites) and 198 AFLP markers. Phenotyping was carried out over a 6-year period on a field trial of 5 hectares, with around 2400 trees measured individually. A high broad sense heritability was found for latex production, and a major QTL directly associated to production was discovered (Hbg16a131). This QTL explained from 32% to 59% of the genetic variance of the production traits. It was also associated to other traits that were strongly correlated to production such as inorganic phosphorus and dry rubber content (latex diagnostic), as well as plugging index. This finding indicates the existence of one major gene (or a cluster of genes) located on linkage group 16 and involved in the genetic determinism of latex production. A second important QTL associated to the girth of the trunk (growth) was detected (Hbg3a312). Depending on the age of the trees, it explained from 16% to 28% of the genetic variance of the girth. By contrast, no significant QTL was found for sucrose content of the latex, as estimated independently from the production, so suggesting that sucrose genetic determinism might not include any single gene having by itself some important effect. The application of one ethephon stimulation did not evidence any specific QTL. Those results pave the way for Markers-Assisted Selection (MAS) as applied to clonal selection in rubber. Genotyping the candidates to selection for the 2 QTLs with important effects should allow a much more accurate estimation of genetic values as soon as at the first selection stage. (Résumé d'auteur

A Decision Support System for Optimized Equipment Turnover, February 2017

The objective of this research was to review current Iowa Department of Transportation (DOT) processes and procedures related to vehicle procurement, maintenance, operations, and sales and develop a tool to optimize equipment lifecycles. The study focused on single-axle A07 and double-axle A12 snowplows, as these represented 31.7% and 45.6%, respectively, of the fiscal year (FY) 2015 equipment replacement budget. Using data currently collected by the Iowa DOT and the models developed, the researchers developed a decision support system (DSS) that recommends optimized normal replacement cycles for single-axle A07 and double-axle A12 vehicles. The objective of the DSS is to minimize equipment lifecycle cost while meeting the needs of Iowa DOT road service. Based on the data provided by the Iowa DOT and the estimated resale value curve of the vehicles, this research indicated that the optimal replacement model is eight years for single-axle A07 vehicles and six years for double-axle A12 vehicles. Assuming the resale value curve is accurate, we estimate that the Iowa DOT would save approximately $1.8 million for single-axle A07s and$6.47 million for double-axle A12s per year by moving from a 15-year normal replacement model to eight years for single-axle A07s and six years for double-axle A12s

Application of QTL mapping for early selection on growth and latex yield traits in rubber breeding

The objective of this study was to apply the QTL mapping by Markers-Assisted Selection approach for early selection on growth and latex yield in rubber breeding. The plant material consisted of 196 progenies derived from the F1 family RRIM 600 x PB 217. A genetic linkage map was built for this family with 229 SSR markers (microsatellites) and 198 AFLP markers. Phenotyping was carried out over a 6 years period on a field trial of 5 hectares, with around 2,400 trees measured individual. The two major QTLs were detected repeatedly. The QTL g16-6 was associated with latex yield near the position of marker a131. This QTL explained up to 66% of the phenotypic variance. It was also associated to other traits that were strongly correlated to production such as inorganic phosphorus and dry rubber content (latex diagnostic), as well as plugging index. This finding indicates the existence of one major gene (or a cluster of genes) located on linkage group g16 and involved in the intensity of metabolic activity of latex cell. A second important QTL associated with girth of the trunk (growth) was detected (QTL g3-60) at the position of marker a312. It explained up to 31% of the phenotypic variance. The discovery of the two major QTLs g3-60 and g16-6 suggest that two major genes act as limiting factors in the genetic determinism of the growth in girth during favorable condition and of rubber production in low-intensive tapping systems. These loci should become privileged targets for the identification of key-genes in rubber. The possible use of their neighboring markers for developing Markers-Assisted Selection (MAS) in the short run appears very reasonable. It should contribute to improve the accuracy of the first selection stage which is the weakest point of the rubber clonal selection scheme. (Résumé d'auteur

The "double cut alternative" (DCA) tapping system: an innovative tapping system designed for Thai rubber smallholdings using high tapping frequency

In Thailand, the continuous decrease in the size of rubber plantations has led to the general adoption of intensive tapping systems which may lead to over harvesting, high rates of tapping panel dryness (TPD), short life-cycles of the plantations, and low labour productivity. In Thailand, farmers usually use a half-spiral downward tapping system (S/2) or a one third-spiral (S/3) with a tapping frequency of once two days (d2) or more. To increase productivity, it is difficult to reduce tapping frequencies, even with ethylene stimulation, as this would result in days without work for tappers. The purpose of this study was to characterize the behaviour of the Hevea rubber yield under the double cut alternative tapping system (DCA). The aim was to ensure the long-term sustainability of latex yield by increasing the time required for latex regeneration between two tappings through splitting this high tapping intensity (100% or above) into two different tapping cuts tapped alternately (S/2 d4 7d7 (t,t). Over a period of 10 years, compared to a single cut tapping system (S/2 d2) of equivalent intensity, DCA increased cumulative rubber production by 9%. Ability of the trees to produce more latex under DCA was related to the sucrose and inorganic phosphorus contents of the latex cells in each tapping panel. DCA produced metabolic activity more favourable to yield during the first 10 years of tapping. But DCA also resulted in higher TPD rates, a sign of a metabolic dysfunction of the productive bark. DCA is a new tapping system. Further research is required to optimize the use of the DCA strategy. Such research, particularly those related to study of multiple-cut systems, should lead to new advances in our knowledge of the physiology of the rubber tree, mainly at the trunk scale. (Résumé d'auteur

Quantification of critical factors affecting fitness of the sugary1 mutant in maize

Fitness of sugary1 (su1) is affected by some critical traits that depend on the genotypes and environments, while their effects have not been quantified with convincing statistical methods. The objective of this work was to identify and quantify the critical factors of su1 fitness with different genotypes and environments. We used two pairs of field corn inbreds that differentially affected su1 viability to develop F1, F2, BC1 and BC2. After selfing, Su1 and su1 kernels were evaluated under controlled environmental conditions and in field trials. Multiple regressions showed that dry weight of juvenile plant was affected by early vigour (plant size, colour and health) and emergence in cold conditions; ear weight by plant appearance, number of plants and chlorophyll content; number of ears by plant appearance, number of plants, chlorophyll content and female flowering; and kernel weight by ear weight, number of plants, row number and ear length. The main critical factors for su1 fitness were early vigour and emergence under cold conditions at initial stages, while several adult traits were related with final fitness.Research was supported by the Spanish Plan for Research and Development (project code AGL2007-64218/AGR and AGL2010-22254) and the Diputación Provincial de Pontevedra. A Djemel acknowledges his fellowship from the Spanish Council for Scientific Research (CSIC).MICINNDiputación Provincial de PontevedraCSICPeer reviewe

A Decision Support System for Optimized Equipment Turnover, February 2017

The objective of this research was to review current Iowa Department of Transportation (DOT) processes and procedures related to vehicle procurement, maintenance, operations, and sales and develop a tool to optimize equipment lifecycles. The study focused on single-axle A07 and double-axle A12 snowplows, as these represented 31.7% and 45.6%, respectively, of the fiscal year (FY) 2015 equipment replacement budget. Using data currently collected by the Iowa DOT and the models developed, the researchers developed a decision support system (DSS) that recommends optimized normal replacement cycles for single-axle A07 and double-axle A12 vehicles. The objective of the DSS is to minimize equipment lifecycle cost while meeting the needs of Iowa DOT road service. Based on the data provided by the Iowa DOT and the estimated resale value curve of the vehicles, this research indicated that the optimal replacement model is eight years for single-axle A07 vehicles and six years for double-axle A12 vehicles. Assuming the resale value curve is accurate, we estimate that the Iowa DOT would save approximately $1.8 million for single-axle A07s and$6.47 million for double-axle A12s per year by moving from a 15-year normal replacement model to eight years for single-axle A07s and six years for double-axle A12s

Coconut Phytophthora. Workshop proceedings, 26-30 October 1992, Manado, Indonesia

Ce séminaire sur le Phythophthora du cocotier avait pour but de réunir tous les acteurs d'un projet démarré en 1990 et de faire le point sur les études réalisées pour la connaissance et la lutte contre ce champignon. Ce projet a donné une grande priorité aux échanges d'informations et aux complémentarités entre les équipes de recherche européennes et tropicale

Aerospace Medicine and Biology: A continuing bibliography with indexes, supplement 172

This bibliography lists 132 reports, articles, and other documents introduced into the NASA scientific and technical information system in September 1977