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Abidjan, France

Lacote R.,CIRAD - Agricultural Research for Development | Gabla O.,Rubber Research Station BP | Obouayeba S.,CNRA | Eschbach J.M.,CIRAD - Agricultural Research for Development | And 3 more authors.
Field Crops Research | Year: 2010

Ethylene stimulation with ethephon (2-chloroethylphosphonic acid) is nowadays essential for increasing latex production in the rubber tree (Hevea brasiliensis): both small-scale planters and agro-industrial plantations worldwide use ethephon. Ethylene stimulation strongly influences cumulative yield and latex cell biochemistry. The purpose of this study was to characterize the long-term behaviour of the rubber tree under ethephon treatment. Over a period of 7 years in Côte d'Ivoire, West Africa, the effect of eight frequencies of ethylene stimulation on yield and latex cell biochemistry was compared in four rubber trees clones, IRCA 130, IRCA 230, GT 1, and PB 217. The ability of the trees to produce more latex under ethylene stimulation was related to the sucrose and inorganic phosphorus contents of the latex cells. For high-yield clones with low sugar content and high inorganic phosphorus content like IRCA 130, namely quick starter clones, no stimulation was necessary to improve yield. For clones like IRCA 230, with higher sugar content, eight ethylene stimulations per year was the optimum frequency to obtain the highest yield. The effect of ethylene stimulation on latex yield increase was significant in clones with high sucrose content and low inorganic phosphorus content such as PB 217. These clones, namely slow starter clones, needed more stimulation to produce more, but in the longer run there were no negative effects of ethylene on the latex yield. These results will help planters optimize latex production by choosing the most appropriate ethylene stimulation to clones according to their latex cells biochemistry. © 2009 Elsevier B.V. All rights reserved. Source

Kouakou K.,Center National Of Recherche Agronomique Cnra | Kebe B.I.,Center National Of Recherche Agronomique Cnra | Kouassi N.,CNRA | Ake S.,University Of Cocody | And 2 more authors.
Plant Disease | Year: 2012

The discovery of new outbreaks caused by Cacao swollen shoot virus (CSSV) in Côte d'Ivoire in 2003, when this disease seemed to have been eradicated since the end of the 1950s in that country, casts doubt on the sustainability of Ivorian cocoa production. The aims of this study were, first, to carry out a molecular characterization of CSSV isolates from the main outbreaks in Côte d'Ivoire; second, determine their phylogenetic position in relation to isolates already discovered in Togo and Ghana; and, finally, study their geographical distribution to understand the dispersal of the virus. Additionally, this study was intended to enable the implementation and validation of a polyvalent molecular diagnosis assay for CSSV. Sequences analyses, corresponding to a fragment located at the 5′ end of open reading frame (ORF)3 of the CSSV genome, revealed three new CSSV groups (D, E, and F) distinct from the A, B, and C groups already identified in Togo. Only group B was detected in all the outbreaks, whereas groups A and C were not identified in Côte d'Ivoire. In addition, a polymerase chain reaction diagnostic using the ORF3A F/R primer pair was polyvalent, because it enabled the detection of CSSV in 90% of the plots in all the cocoa regions analyzed by this study. © 2012 The American Phytopathological Society. Source

Orjuela J.,IRD Montpellier | Thiemele Deless E.F.,CNRA | Kolade O.,Africa Rice Center | Cheron S.,IRD Montpellier | And 2 more authors.
Molecular Plant-Microbe Interactions | Year: 2013

RYMV2 is a major recessive resistance gene identified in cultivated African rice (Oryza glaberrima) which confers high resistance to the Rice yellow mottle virus (RYMV). We mapped RYMV2 in an approximately 30-kb interval in which four genes have been annotated. Sequencing of the candidate region in the resistant Tog7291 accession revealed a single mutation affecting a predicted gene, as compared with the RYMV-susceptible O. glaberrima CG14 reference sequence. This mutation was found to be a one-base deletion leading to a truncated and probably nonfunctional protein. It affected a gene homologous to the Arabidopsis thaliana CPR5 gene, known to be a defense mechanism regulator. Only seven O. glaberrima accessions showing this deletion were identified in a collection consisting of 417 accessions from three rice species. All seven accessions were resistant to RYMV, which is an additional argument in favor of the involvement of the deletion in resistance. In addition, fine mapping of a resistance quantitative trait locus in O. sativa advanced backcrossed lines pinpointed a 151-kb interval containing RYMV2, suggesting that allelic variants of the same gene may control both high and partial resistance. © 2013 The American Phytopathological Society. Source

Cubry P.,CIRAD - Agricultural Research for Development | Cubry P.,Current address DBN Plant Molecular Laboratory | de Bellis F.,CIRAD - Agricultural Research for Development | Avia K.,University of Oulu | And 5 more authors.
BMC Genomics | Year: 2013

Background: A reciprocal recurrent selection program has been under way for the Coffea canephora coffee tree for approximately thirty years in the Ivory Coast. Association genetics would help to speed up this program by more rapidly selecting zones of interest in the genome. However, prior to any such studies, the linkage disequilibrium (LD) needs to be assessed between the markers on the genome. These data are essential for guiding association studies.Results: This article describes the first results of an LD assessment in a coffee tree species. Guinean and Congolese breeding populations of C. canephora have been used for this work, with the goal of identifying ways of using these populations in association genetics. We identified changes in the LD along the genome within the different C. canephora diversity groups. In the different diversity groups studied, the LD was variable. Some diversity groups displayed disequilibria over long distances (up to 25 cM), whereas others had disequilibria not exceeding 1 cM. We also discovered a fine structure within the Guinean group.Conclusions: Given these results, association studies can be used within the species C. canephora. The coffee recurrent selection scheme being implemented in the Ivory Coast can thus be optimized. Lastly, our results could be used to improve C. arabica because one of its parents is closely related to C. canephora. © 2013 Cubry et al.; licensee BioMed Central Ltd. Source

Silvie P.J.,CIRAD - Agricultural Research for Development | Silvie P.J.,Laboratoire Evolution | Renou A.,CIRAD | Vodounnon S.,AIC | And 12 more authors.
Crop Protection | Year: 2013

In the late 1980s, after a long period during which insecticides were sprayed at preset dates to control cotton (Gossypium hirsutum L.) pests and their damage, some French-speaking countries in sub-Saharan areas decided to disseminate a special form of crop protection approach among smallholders, i.e. targeted staggered control (LEC, for Lutte étagée ciblée). According to this approach, decisions on some insecticide applications were made on the basis of infestation levels or the extent of crop injury caused by major pests: Aphis gossypii Glover aphids, Haritalodes (= Syllepte) derogata F., leaf-eating caterpillars, and more generally Helicoverpa armigera (Hübner), Diparopsis watersi Rothschild, Earias insulana (Boisduval) and Earias biplaga (Walker) bollworms. Polyphagotarsonemus latus (Banks) mites were sometimes included on this list. Today, the calendar-based or conventional program is still widely implemented with some changes in insecticides applied due to the development of pyrethroid resistance in H. armigera. Depending on the country, protection programs based on pest monitoring have been preserved or replaced by programs still using thresholds (staggered or true). In Benin, there are two forms of LEC tailored to two regions delineated according to the extent of damage caused by of bollworms that live inside cotton bolls, i.e. Thaumatotibia (= Cryptophlebia) leucotreta (Meyrick). The logical follow-up to LEC, involving true thresholds, was developed in Mali, Cameroon and, recently, Senegal. Cameroon opted for a sequential plan for individual decision program or LOIC (for Lutte après observation individuelle des chenilles), based on control after sequential sampling of bollworms. A calendar program with additional applications of insecticides based on a particular scouting of H. armigera was developed in Togo. In Ivory Coast, the use of true thresholds is limited to the beginning of the cotton crop cycle whereas in Burkina Faso true thresholds are used after the first two calendar sprayings. The present article describes the diversity of these cotton protection programs, sampling methods and associated intervention thresholds based on pests or injury levels in addition to the advantages and constraints associated with their adoption. © 2012 Elsevier Ltd. Source

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