C13 and Deuterium Isotope Effects in the Photolysis of Methyl and Ethyl Bromide

Relative rates of formation of isotopic radicals in the photolysis of gaseous methyl and ethyl bromide have been measured. Photolyses (2537 A) were carried out in a large excess of cyclopentane. Methyl (or ethyl) radicals formed in the primary C☒Br bond scission abstract H from cyclopentane to form methane (or ethane). For methyl bromide, the C12/C13 enrichment factor for the first fraction of the methane was 1.039±0.003. The corresponding factor for the α‐carbon—Br rupture in ethyl bromide was 1.041±0.004. In the deuterium experiments, CH3Br—CD3Br mixtures in excess cyclopentane were photolyzed. The H/D fractionation factor (based on CH4/CD3H) was 1.41±0.01.The difference in rates of formation of isotopic radicals is due to the difference in ultraviolet absorption coefficients of the isotopic alkyl bromides. At 2537 A the observed ratio of the extinction coefficient of CH3Br relative to that of CD3Br is 1.38±0.05.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71079/2/JCPSA6-30-4-973-1.pd

Obsidian Samples from Archaeological Sites in Northwestern Alaska: A Preliminary Report

Reports the Na and Mn contents and Na/Mn ratios, determined by neutron activation analyses of 103 obsidian samples from the Onion Portage and nine related archeological sites. The occurrence and stratigraphic distribution are noted of four groups of obsidian distinguished by Mn content and Na/Mn ratio. Group B, the largest, appears in a complex with an age of 4000-3900 BC and in another of 1000-1700 AD, group A in complexes dating at 2600-2200 and 1500-500 BC, group C occurs 2200-1800 BC; and group D 400-1700 AD. There are at least four obsidian sources represented whose geographic locations are unknown

Evaluation du pouvoir disjonctif des variables catégorielles impliquées dans la sélection du palmier à huile (Elaeis guineensis jacq.) en Côte d’Ivoire

En amélioration génétique du palmier à huile (Elaeis guineensis Jacq.), les variables catégorielles constituent une part majoritaire de l’information utilisée pour différencier, les populations de géniteurs issus du programme de sélection récurrente réciproque (SRR). Le pouvoir disjonctif de ces variables a été testé sur 134 géniteurs sélectionnés issus des populations du premier, deuxième et troisième cycle de SRR. Les variables catégorielles utilisées pour différencier ces populations sont celles qui ont permis d’avoir des informations sur les origines géographiques et les généalogies parentales des géniteurs. L’analyse factorielle de l’ensemble de ces variables catégorielles, a permis de déterminer le pouvoir disjonctif de chacun des deux principaux critères de divergences des populations de géniteurs sélectionnes. Le critère "origine géographique" a représenté 14 % d’expression de disjonction totale des populations de géniteurs sélectionnés. Le critère "généalogie parentale" a représenté 70 % d’expression de disjonction totale des populations de géniteurs sélectionnés. L’utilisation de ces deux critères de différenciation des populations de géniteurs sélectionnées peut constituer une bonne alternative à l’utilisation des données moléculaires dans les études de la diversité des populations de palmier à huile en sélection.Mots-clés : Palmier à huile, sélection, variable catégorielle, disjonction de populatio

Assessment of various strategies for the preservation of clonal genetic resources in oil palm (Elaeis guineensis Jacq.)

Three different approaches for the preservation of oil palm (Elaeis guineensis Jacq.) clonal genetic resources and their impacts on the induction of the « mantled » somaclonal variation were assessed. In vitro long term preservation of somatic embryos stock-cultures was studied : after a 5 year cultivation period, 75 % of clonal lines were still normal. Between 8 and 13 years of embryo cultures, half of the considered clonal lines were found to be « mantled ». Finally, 40 % were found to be normal over 15 years of in vitro conservation. Clonal conformity of ramets resulting from the re-cloning of somaplants depended, on one hand, on the floral status of the mother plant at the time of sampling and, on the other hand, on its origin. Re-cloning of abnormal regenerants led, in all cases, to 100 % abnormal offspring. The age of the ramet used as mother palm at the time of sampling was found to be critical for true-to-type regeneration. There is a high risk of obtaining variant regenerant palms if the clonal mother palm is sampled at nursery stage. Field observations carried out on palms originating from somatic embryos cryopreserved at -196 °C showed floral conformity rates comparable to those obtained from standard not-cryopreserved clonal palms, for 6 out of the 8 clonal lines studied. From the 2 remaining clonal lines, a few regenerant palms originating from standard batch were found to be « mantled », whereas those resulting from cryopreserved embryos were all normal. The assumption of changes in levels of genomic DNA methylation during preservation was discussed, together with the capacity of our cryopreservation protocol to select embryogenic cells which were only suited to trueto-type regeneration

Personal exposure to PM_2.5 emitted from typical anthropogenic sources in southern West Africa: chemical characteristics and associated health risks

Urbanization is an issue that is strongly emerging in southern West Africa (sWA). There is a lack of full understanding on chemical compositions and personal exposure levels to fine particulate matter (hereafter defined as PE PM2.5) and its health risks related to various anthropogenic sources in this region. In this study, PE PM2.5 was studied in dry (January) and wet (July) seasons of 2016 for the first time to characterize the contributions of a domestic fire site (DF) to the exposure of women and a waste burning site (WB) to that of students in Abidjan, Côte d'Ivoire, and a motorcycle traffic site (MT) to that of drivers in Cotonou, Benin. The average PE PM2.5 mass concentrations were 331.7±190.7, 356.9±71.9 and 242.8±67.6&thinsp;µg&thinsp;m−3 at DF, WB and MT sites for women, students and drivers, which were 2.4, 10.3 and 6.4 times the ambient PM2.5 concentrations, respectively. Elevated PE PM2.5 levels in the dry season were found at DF (358.8±100.5&thinsp;µg&thinsp;m−3), WB (494.3±15.8&thinsp;µg&thinsp;m−3) and MT (335.1±72.1&thinsp;µg&thinsp;m−3) sites, on average 15&thinsp;% higher than that at DF and 55&thinsp;% higher at both WB and MT sites in the wet season. The seasonal variations were attributed to emission sources, meteorological factors and personal activities. In addition, the results show that geological material (35.8&thinsp;%, 46.0&thinsp;% and 42.4&thinsp;%) and organic matter (34.1&thinsp;%, 23.3&thinsp;% and 24.9&thinsp;%) were the major components of PE PM2.5 at DF, WB and MT sites. It is worth noting that the contribution of heavy metals was higher at WB (1.0&thinsp;%) than at DF (0.7&thinsp;%) and MT (0.4&thinsp;%) sites, strongly influenced by waste burning emission. This results in the highest non-cancer risks of heavy metals to students, 5.1 and 4.8 times the values for women and drivers, respectively. By conducting organic speciation, fingerprints were used to access the exposure and identify the source contributions from typical local anthropogenic sources. The women's exposure concentration to particulate polycyclic aromatic hydrocarbons (PAHs) at DF (77.4±47.9&thinsp;ng&thinsp;m−3) was 1.6 and 2.1 times, respectively, that of students at WB (49.9±30.7&thinsp;ng&thinsp;m−3) and of drivers at MT (37.0±7.4&thinsp;ng&thinsp;m−3). This can be associated with the higher contributions from solid fuels' burning and meat grilling activities to women, resulting in a level 5 times in exceedance of the cancer risk safety threshold (1×10-6). Phthalate esters (PAEs), commonly used as plasticizers in products, were in high levels in the student exposure PM2.5 samples (1380.4±335.2&thinsp;ng&thinsp;m−3), owing to obvious waste burning activities nearby. The drivers' exposures to fossil fuel combustion markers of hopanes in PE PM2.5 at MT (50.9±7.9&thinsp;ng&thinsp;m−3) was 3.0–3.3 times those for women at DF (17.1±6.4&thinsp;ng&thinsp;m−3) and students at WB (15.6±6.1&thinsp;ng&thinsp;m−3). Overall, the current study shows that wood combustion, waste burning, fugitive dust and motor vehicle emissions were the dominant sources of PE PM2.5 and mainly contributed to its toxicities. The exposure to the heavy metals Pb and Mn caused high non-cancer risks to students at WB, while the severe cancer risk of PAHs was found for women at DF via inhalation. The result of this study provides original data, initial perspective of PM2.5 personal exposure and health risk assessment in the developing areas. The information encourages the governments to improve the air quality and living standards of residents in this region.</p

QTL detection by multi-parent linkage mapping in oil palm (Elaeis guineensis Jacq.)

A quantitative trait locus (QTL) analysis designed for a multi-parent population was carried out and tested in oil palm (Elaeis guineensis Jacq.), which is a diploid cross-fertilising perennial species. A new extension of the MCQTL package was especially designed for crosses between heterozygous parents. The algorithm, which is now available for any allogamous species, was used to perform and compare two types of QTL search for small size families, within-family analysis and across-family analysis, using data from a 2 × 2 complete factorial mating experiment involving four parents from three selected gene pools. A consensus genetic map of the factorial design was produced using 251 microsatellite loci, the locus of the Sh major gene controlling fruit shell presence, and an AFLP marker of that gene. A set of 76 QTLs involved in 24 quantitative phenotypic traits was identified. A comparison of the QTL detection results showed that the across-family analysis proved to be efficient due to the interconnected families, but the family size issue is just partially solved. The identification of QTL markers for small progeny numbers and for marker-assisted selection strategies is discussed

Molecular variability from two selection of BRT10 population in an inbreeding program of oil palm (Elaeis guineensis Jacq.) in Côte d’Ivoire

Genetic variability of two groups of palms composed with four progenies selected in BRT10 improved populations resulting from successive self-fertilizations of two parents LM2T and LM10T was studiedusing four polymorphic microsatellites DNA markers of Elaeis guineensis Jacq. The molecular variability of those progenies was analyzed and genetic diversity of each group of palms was deduced.The results of analysis of molecular variance revealed that 59.68% of variance can be explained by palms within each progeny, while 31.24% of total variance was partitioned between the two groups ofpalms. The program selection of self-fertilizations has created a distinct molecular structure within BRT10 improved populations resulting from LM2T and LM10T. Molecular analysis showed that thepartitioning of variance in this breeding program was higher among palms within each progeny than among the two groups of palms. Only the exploitation of molecular data revealed the truly diversifiedprogeny. The use of molecular data analysis in support with agro-morphological assessment should improve the cross performance while maintaining the genetic variation for further progress insubsequent selection cycles

Criteres Physiologiques Discriminants Au Jeune Age Pour La Selection De Genotypes De Palmier A Huile (Elaeis guineensis Jacq.) Tolerants A La Secheresse

L\'alimentation hydrique est le principal facteur limitant la productivité du palmier à huile (Elaeis guineensis Jacq.). Les réponses physiologiques des plantules, soumises à un déficit hydrique, ont été évaluées sous serre, dans des pots durant 4 mois. En vue d\'identifier des critères discriminants au jeune âge pour une utilisation en sélection variétale, du matériel sensible et un autre tolérant à la sécheresse ont été soumis à un cycle de dessèchement - réhydratation. Les paramètres tels que : le statut hydrique (taux de transpiration relative, potentiel hydrique foliaire), les échanges gazeux (photosynthèse, conductance stomatique) et l\'activité photochimique (fluorescence chlorophyllienne) ont été étudiés. Le régime hydrique a fortement affecté l\'ensemble des paramètres étudiés. Le taux de satisfaction des besoins en eau a varié de 90 à 4 %, et le potentiel hydrique a atteint une valeur de -3 MPa trois semaines après suspension de l\'arrosage. Pendant la phase de réhydratation, les plantules ont présenté une capacité de reprise satisfaisante. Malgré une bonne corrélation, les deux paramètres d\'échanges gazeux ne peuvent être proposés isolément comme critères de sélection dans les conditions de l\'expérience. Par contre, la mesure de la fluorescence chlorophyllienne a permis de distinguer le matériel tolérant du sensible au bout d\'une semaine. Ces resultats ouvrent une perspective dans la sélection de génotypes de palmier à huile tolérants à la sécheresse au jeune âge.Water deficit is the main limiting factor in oil palm production (Elaeis guineensis Jacq.) in West Africa.Physiological responses to drought plantlets were accessed under green house conditions for 4 months. A drought tolerant species and a sensitive one were subject to one wetting and drying cycle. Parameters such as water status (transpiration rate, water potential), leaf gas exchanges (photosynthesis, stomatal conductance) and photochemical activity (chlorophyll fluorescence) were monitored. Results show that all parameters were affected by watering. Transpiration rate dropped from 90 to 4 %, with a leaf potential close to -3 MPa three weeks after watering was interrupted. Despite a good correlation, the two leaf gas exchange parameters alone were not relevant criteria for the early screening of oil palm material. However, chlorophyll fluorescence data allowed early screening of both genotypes within one week after withdrawal of watering. The latter parameter can offer effective tool to oil palm breeders for screening young oil palm genotypes to drought tolerance. Key-words Keywords: Elaeis guineensis, palmier à huile, déficit hydrique, photosynthèse, fluorescence chlorophyllienne, Côte d\'Ivoire.Agronomie Africaine Vol. 19 (1) 2007: pp. 1-1

Diffusion variétale du palmier à huile (Elaeis guineensis Jacq.)

La productivité du palmier à huile au cours du siècle passé a connu une croissance importante où l’amélioration génétique a pris une large part. Elle a connu un rythme de croissance assez comparable à celui obtenu pour des plantes annuelles de pays tempérés (blé, maïs, tournesol, etc.). Il est possible de dégager les étapes importantes qui ont marqué l’histoire de l’amélioration. Après une assez longue période de sélection massale, l’exploitation du gène « shell », dont l’hérédité a été découverte par Beirnaert en 1939, a apporté une amélioration de 30% [1]. Vers 1960, l’exploitation de l’hétérosis des croisements inter-origines apporte une nouvelle amélioration de 10% environ [2]. Enfin, deux cycles de sélection récurrente ont été achevés par différentes équipes et chacun a apporté 12 à 18% d’amélioration de la productivité. En 1991, la valeur moyenne des semences commerciales, plantées dans de bonnes conditions, était proche de 6,7 tonnes d’huile par hectare et par an [3]. Aujourd’hui, elle est de l’ordre de 7,2 t/ha/an [4]. Ces gains quantitatifs ont été accompagnés de progrès qualitatifs importants comme la diminution de la vitesse de croissance, l’augmentation du pourcentage d’huile dans les régimes ou l’acquisition d’une forte résistance à la fusariose en Afrique de l’Ouest [5]. La qualité du futur matériel végétal devrait être sensiblement améliorée par l’utilisation d’une base génétique élargie dans les programmes d’amélioration [6]. En effet, les stations de recherche disposent d’une bonne diversité génétique rassemblée lors de nombreuses prospections réalisées en Afrique (pour E. guineensis) et sur une espèce apparentée en Amérique latine (pour E. oleifera). Ces collections apportent de nouveaux caractères de qualité de l’huile, de résistance à la fusariose, qui sévit en Afrique, ou à la pourriture du cœur en Amérique latine. Le progrès génétique disponible en expérimentation doit être intégré dans les semences vulgarisées au plus vite et en quantité suffisante. Cependant, pour la reproduction du meilleur matériel, il existe des contraintes liées à la biologie des semences qui compliquent et ralentissent cette vulgarisation. En raison d’une dormance difficile à lever, les semences de palmier à huile sont distribuées sous forme de graines germées et leur distribution demande une organisation particulière