Sols, états de surface et rendements du cotonnier en station expérimentale (Togo central)

Dans une station expérimentale agronomique, le comportement des plantes cultivées peut dépendre autant des variations liées au support que des différences de techniques culturales. Sur huit parcelles agronomiques de la station de Dalanda, au Togo central, des variations édaphiques ont été comparées avec celles du rendement du cotonnier au cours de la campagne 1989. Les variations édaphiques ont été déterminées par l'observation de coupe de sol, et par la cartographie du microrelief et des états de surface. Les hétérogénéités du rendement ont été mesurées en se basant sur un traitement agronomique homogène. La méthode employée permet de cartographier le comportement du cotonnier et de comparer les cartes obtenues avec les variations spatiales des caractéristiques du support. Des corrélations ont été établies entre des caractéristiques du sol, les états de surface et le rendement en coton-graine. (Résumé d'auteur

Typologie et logique socio-économique des systèmes de culture associant céréales et légumineuses dans les agro-écosystèmes soudano-sahéliens du Burkina Faso

Dans la zone soudano-sahélienne du Burkina Faso, les associations mixtes céréales-légumineuses dominent les surfaces cultivées annuellement. Cependant, les rendements sont faibles et ne couvrent souvent pas les besoins alimentaires des exploitations qui les pratiquent. Afin d’améliorer la productivité de ces associations, il est nécessaire de comprendre la logique socio-économique de leurs mises en oeuvre. Dans cette optique, 60 exploitations agricoles familiales (EA) ont été enquêtées dans la région Nord du Burkina. Des analyses en correspondances multiples (ACM) font ressortir 4 types de systèmes de culture caractérisés d’une part par le niveau d’apport de matière organique et la fréquence de désherbage et d’autre part, par la présence de structures pérennes de conservation des eaux et des sols. La fertilisation organique et le désherbage fréquent sont associés aux EA les mieux pourvues en main d’oeuvre familiale, en petits ruminants et surfaces agricoles. L’âge de l’exploitant agricole et le nombre d’épouses sont de bons indicateurs des moyens économiques de l’EA. La plupart des recettes monétaires annuelles par EA varient dans la gamme très large de 25 à 300 KFCFA. Ces aspects doivent être pris en compte en vue de raisonner des propositions techniques adaptées à la diversité des EA de cette région.© 2016 International Formulae Group. All rights reserved.Mots clés: ACM, associations mixtes céréales-légumineuses, typologie des systèmes de culture, logique socioéconomique, Burkina FasoEnglish Title: Typology and socio-economic logic of cropping systems in Sub-Saharan agro-ecosystems of Burkina FasoEnglish AbstractIn Sub-Saharan zone of Burkina Faso, legumes and cereals mixed cultivation systems occupy most of the cultivated area. However, yields are low and often do not cover the food needs of farms that practise them. In order to improve the productivity of these intercropping systems, it is necessary to understand the socio-economic logic of their implementation. To this purpose, sixty family farms were surveyed in the northern region of Burkina Faso. Multiple correspondences analysis (MCA) showed four types of cropping systems characterized on one hand by the level of organic matter intake and weeding frequency and on the other hand, by the presence of permanent structures for water and soil conservation. Organic matter fertilization and frequent weeding are associated with farms with high family labor, livestock (especially small ruminants) and high cultivated area, while 70% of farmers have an off-farm activity. The age of household head and the number of their wives are good indicators of farmers’ income. Most of farmers’ monetary recipes vary widely from 25 to 300 KFCFA. These aspects must be taken into consideration for reasoning suitable technical recommendations for the farmer’s in this region.© 2016 International Formulae Group. All rights reserved.Keywords: MCA, legumes and cereals mixed cultivation systems, typology of cropping systems, socioeconomic logic, Burkina Fas

Predicting soil erosion after land use changes for irrigating agriculture in a large reservoir of southern Portugal

The construction of the Alqueva reservoir in a semi-arid Mediterranean landscape brought new opportunities for irrigated farming. Land use changes and climate change may alter the risk of soil erosion that was not predicted in the initial development plans and decrease the lifetime of the investment. A comprehensive methodology that integrates the Revised Universal Soil Loss Equation (RUSLE) and geographic information system was adopted to study the effect on soil erosion of different land-uses of the Alqueva reservoir region. Analysing the soil erosion of each land-use it was obtained the following land use erosion vulnerability: Olive orchard>Vineyard>Montado>Alfalfa. The strong erosion variances that were observed in the study area show the importance of locating the 'hot spots' of soil erosion. Simulated scenarios for the entire area can be used as a basis for site-specific soil conservation plans, to promote sustainable land management practices and to facilitate localized erosion control practices and environmentally friendly farming. (C) 2015 The Authors. Published by Elsevier B.V

Structure and evolution of Apetala3, a sex-linked gene in Silene latifolia

<p>Abstract</p> <p>Background</p> <p>The evolution of sex chromosomes is often accompanied by gene or chromosome rearrangements. Recently, the gene <it>AP3 </it>was characterized in the dioecious plant species <it>Silene latifolia</it>. It was suggested that this gene had been transferred from an autosome to the Y chromosome.</p> <p>Results</p> <p>In the present study we provide evidence for the existence of an X linked copy of the <it>AP3 </it>gene. We further show that the Y copy is probably located in a chromosomal region where recombination restriction occurred during the first steps of sex chromosome evolution. A comparison of X and Y copies did not reveal any clear signs of degenerative processes in exon regions. Instead, both X and Y copies show evidence for relaxed selection compared to the autosomal orthologues in <it>S. vulgaris </it>and <it>S. conica</it>. We further found that promoter sequences differ significantly. Comparison of the genic region of <it>AP3 </it>between the X and Y alleles and the corresponding autosomal copies in the gynodioecious species <it>S. vulgaris </it>revealed a massive accumulation of retrotransposons within one intron of the Y copy of <it>AP3</it>. Analysis of the genomic distribution of these repetitive elements does not indicate that these elements played an important role in the size increase characteristic of the Y chromosome. However, <it>in silico </it>expression analysis shows biased expression of individual domains of the identified retroelements in male plants.</p> <p>Conclusions</p> <p>We characterized the structure and evolution of <it>AP3</it>, a sex linked gene with copies on the X and Y chromosomes in the dioecious plant <it>S. latifolia</it>. These copies showed complementary expression patterns and relaxed evolution at protein level compared to autosomal orthologues, which suggests subfunctionalization. One intron of the Y-linked allele was invaded by retrotransposons that display sex-specific expression patterns that are similar to the expression pattern of the corresponding allele, which suggests that these transposable elements may have influenced evolution of expression patterns of the Y copy. These data could help researchers decipher the role of transposable elements in degenerative processes during sex chromosome evolution.</p