Gestion traditionnelle et statut des ressources génétiques du sorgho (Sorghum bicolor L. Moench) au Nord-Ouest du Bénin

Le sorgho, Sorghum bicolor (L.) Moench, est une importante ressource alimentaire au Bénin. Sa culture est essentiellement pratiquée au centre et au nord du pays. Afin de mieux comprendre le niveau de diversité et les systèmes traditionnels de gestion et de conservation des variétés locales cultivées au Nord-Ouest du pays, une enquête basée sur une approche participative de recherche a été conduite dans 13 villages régulièrement distribués dans la zone. Au total, 45 variétés locales (61 noms vernaculaires) ont été inventoriées, présageant d’une grande diversité génétique du sorgho dans le milieu. Le nombre moyen de variétés locales inventoriées est de cinq par village et de deux par ménage. La distribution des variétés à travers la zone d’étude a été déterminée et les principaux facteurs y afférant étudiés. La couleur des grains, la durée du cycle végétatif ou la valeur marchande sont les plus importants critères utilisés par les producteurs pour la dénomination, l’identification, la classification et la sélection des variétés. Les systèmes traditionnels de sélection et de gestion des semences varient substantiellement d’un village à un autre et d’une ethnie à l’autre. Aussi, l’étudea-t-elle révélé l’existence dans certains villages d’une menace de disparition des variétés à cycle végétatif long et à grains blancs. Des efforts concertés devraient donc être déployés pour la valorisation et la préservation des ressources génétiques de cette céréale afin d’accroître sa production pour une meilleure sécurité alimentaire au Bénin.Mots clés: Bénin, diversité variétale, conservation, Sorghum bicolo

Diversity and ecological niche model of malaria vector and non-vector mosquito species in Covè, Ouinhi, and Zangnanado, Southern Benin.

The present study aimed to assess mosquito species diversity, distribution, and ecological preferences in the Covè, Ouinhi, and Zangnanado communes, Southern Benin. Such information is critical to understand mosquito bio-ecology and to focus control efforts in high-risk areas for vector-borne diseases. Mosquito collections occurred quarterly in 60 clusters between June 2020 and April 2021, using human landing catches. In addition to the seasonal mosquito abundance, Shannon's diversity, Simpson, and Pielou's equitability indices were also evaluated to assess mosquito diversity. Ecological niche models were developed with MaxEnt using environmental variables to assess species distribution. Overall, mosquito density was higher in the wet season than in the dry season in all communes. A significantly higher Shannon's diversity index was also observed in the wet season than in the dry seasons in all communes (p < 0.05). Habitat suitability of An. gambiae s.s., An. coluzzii, Cx. quinquefasciatus and Ma. africana was highly influenced by slope, isothermality, site aspect, elevation, and precipitation seasonality in both wet and dry seasons. Overall, depending on the season, the ecological preferences of the four main mosquito species were variable across study communes. This emphasizes the impact of environmental conditions on mosquito species distribution. Moreover, mosquito populations were found to be more diverse in the wet season compared to the dry season

Genetic diversity of Sorghum bicolor (L.) Moench landraces from Northwestern Benin as revealed by microsatellite markers

The understanding of genetic diversity within local crop varieties constitutes an important step in the preservation of their genetic potential. The objective of this study was to assess the genetic diversity of sorghum (Sorghum bicolor (L.) Moench) cultivated in the Northwest of Benin and to reveal certain fundamental evolutionary mechanisms. A total of 61 accessions of sorghum landraces belonging to the four identified races in Benin were estimated using 20 microsatellite markers. For all the loci analyzed, 140 polymorphic alleles were detected with a mean value of 7.00 per locus and polymorphic information content (PIC) average value was 0.33 for all the 20 simple sequence repeats (SSRs), suggesting an important genetic diversity within the cultivated sorghum germplasm used. An unweighted pair group method arithmetic average (UPGMA) clustering and principal coordinate analysis (PCoA) based on DICE coefficient revealed three major genetic groups supported by two main components: the botanical race and the morpho-physiological characteristics of the grains (colour and degree of bitterness). It was thus recommended that further research on genetic diversity of sorghum should integrate these genetic parameters for a better preservation of the genetic resources of this important crop in Benin.Keywords: Genetic diversity, simple sequence repeats (SSRs) markers, Sorghum bicolor, Benin.

Evaluation génétique du processus de la domestication des ignames sauvages dioscorea abyssinica, dans l’état de Nasarawa (Nigéria) par les marqueurs microsatellites (ssr). comparaison des ignames pré-domestiquées avec les variétés locales des ignames cult

L’importance du processus de la domestication des ignames sauvages Dioscorea abyssinica Hochst dans la dynamique évolutive et la diversification des variétés traditionnelles a été évaluée à travers l’étude d’une collection de 66 accessions d’igname composée de génotypes cultivées, (D. rotundata), sauvages (D. abyssinica), domestiquées ou en voie de domestication au moyen de neuf (9) microsatellites nucléaires. Les analyses ont révélé une importante diversité génétique au sein de la collection. Les clones nouvellement domestiqués ou en domestication sont génétiquement différents des anciennes variétés existantes. Les résultats permettent de conclure que la domestication crée effectivement de nouveaux génotypes à partir des espèces sauvages ou de recombinants issus d’hybridation inter-variétale et participe donc à l’introduction de nouvelles variétés dans le compartiment cultivé.Mots clés : Igname, domestication, Flux de gènes, microsatellites nucléaire.The importance of the wild yams, Dioscorea abyssinica Hochst domestication process in the evolutionary dynamics and diversification of traditional varieties have been evaluated through the characterization of a collection including 66 accessions of cultivated yam (D. rotundata) and wild yam (D. abyssinica), either already domesticated or in the process of domestication, was studied using nine (9) nuclear micro satellites. The analyses showed a significant genetic diversity in the collection studied. A Recently domesticated clones or clones in the process of domestication were genetically different from old varieties. The results helped to find that domestication effectively creates new yam genotypes from wild species or recombinants derived from inter-specific hybridization and contributes to the introduction of new varieties in the farming sector.Key words: Yam, domestication, gene flow, nuclear micro satellites

Molecular Identification of Xa4 Resistance Gene to Xanthomonas oryzae pv. oryzae in Cultivated Rice in Northwest Benin

Aims: The aim of this study was to identify the cultivated rice varieties that were resistant to Xanthomonas oryzae pv. oryzae (Xoo) by molecular screening. Xanthomonas oryzae pv. oryzae (Xoo) was the causal agent of bacterial blight, in the department of Atacora in Benin. Place and Duration of Study: Laboratory of Molecular Biology and Bioinformatics Applied to Genomics, between July 2021 and November 2021. Methodology: Thirty-two rice accessions were collected in the department of Atacora and the IRBB4 isogenic line carrying Xa4 resistance gene, as a positive control, were screened using SSR marker. Genomic DNA was extracted from plants leaves. PCR using a pair of MP12 primers linked to the Xa4 gene were performed and amplified products were analyzed by electrophoresis in a 2% agarose gel. Results: Our results showed that a significant number of rice varieties grown in northern Benin were resistant to Xoo. 62.5% were resistant of which 70% were local varieties. Some of these resistant varieties (35%) were heterozygous (Xa4/xa4) and others were homozygous (Xa4/Xa4). 10% had specific genotypes other than those expected, which showed the probability of existence new resistance alleles that need to be characterized. Conclusion: This is the first time that a bacterial blight resistance gene has been identified in Beninese rice cultivation. This result will be very useful to rice breeders for developing elites resistant varieties through markers assisted selection programs

Variabilité génétique des accessions d’igname Dioscorea alata L. introduites au Bénin à partir des Îles du Sud-Pacifique

Objectif: L’igname est l’une des plus importantes cultures vivrières à tubercules en Afrique de l’Ouest, en particulier au Bénin. Dans le but de renforcer la variabilité génétique des ignames cultivées D. alata (L.) au Bénin, une collection de 21 accessions a été récemment introduite des îles du Sud-Pacifique grâce à une coopération CIRAD-Institut National de Recherche Agricole du Bénin (INRAB). Le présent travail a pour objectif d’évaluer la variabilité génétique au sein de cette collection afin de favoriser son utilisation rationnelle.Méthodologies et résultats : Pour cette investigation, 10 marqueurs microsatellites et 17 traits agromorphologiques ont été utilisés. Une variation phénotypique significative a été observée dans la collection, notamment au niveau de nombreux attributs qualitatifs. Sur le plan moléculaire, un total de 40 allèles a été détecté avec en moyenne 4 allèles par locus. Neuf des 10 marqueurs microsatellites SSR utilisés se sont révélés discriminants avec une valeur moyenne du Potentiel en Information du Polymorphisme (PIC) estimée à 0,239. Les similarités génétiques estimées entre les accessions varient amplement (0,11 – 0,87), suggérant qu’une importante diversité existe dans la collection. L’étude de la structuration de cette variabilité génétique permet de classer les accessions en trois classes phénotypiques et deux groupes génétiques différents au sein de la collection.Conclusion : Ces résultats ont montré que les accessions introduites sont morphologiquement et génétiquement très diversifiées et contribuent donc significativement au renforcement de la diversité génétique des ignames cultivées au Bénin.Mots clés : Agro-morphologie, Bénin, D. alata, Diversité génétique, Îles Pacifiques, SSRsAbstractObjective: Yam is one of the most important tuber crops grown in West Africa, in particular in Benin. In order to reinforce the genetic variability of water yam D. alata (L.) cultivated in Benin, a collection of 21 accessions was recently introduced from the South Pacific Islands through the cooperation of CIRAD and National Institute of Agricultural Research of Benin (INRAB). The objective of this study was to assess the genetic diversity in this collection for favoring its rational use.Methodology and results: To conduct this investigation, ten microsatellites loci and 17 agro-morphological traits were used. A significant phenotypic variation was observed within the collection, mainly at many qualitative attributes. At molecular level, a total of 40 alleles was detected with an average allele number of 4 per locus. Nine of 10 microsatellites used were found to be discriminative with a mean value of Polymorphic Information Content (PIC) estimated at 0.239. Genetic similarities estimated between the accessions varied widely (0.11- 0.87), suggesting that an important genetic variability exist in the collection. The inference of the structure of such genetic variability revealed the existence of two genetic groups organized into three phenotypic classes within the collection.Conclusion: These results revealed that the introduced accessions are morphologically and genetically well diversified and thus will contribute significantly in reinforcing the existing local water yam genetic diversity in Benin.Key words: Agro-morphology, Benin, D. alata, Genetic Diversity, Pacific Islands, SSR

Malaria transmission potential of Anopheles gambiae s.l. in indoor residual spraying areas with clothianidin 50 WG in northern Benin

Abstract The study objective was to assess the frequency of the kdr-L995F and ace-1 G280S genetic mutations in Anopheles gambiae s.l. mosquitoes and examine their ability to transmit Plasmodium falciparum in areas where indoor residual spraying (IRS) was implemented with Clothianidin 50 WG. The study was conducted in six communes in the Alibori and Donga departments of which four were IRS-treated and two were untreated and served as control. Post-IRS monthly samples of adult mosquitoes were collected in study communes using human landing catches (HLC). An. gambiae s.l. specimens were processed to detect kdr-L995F and ace-1 G280S mutations via PCR as well as Plasmodium falciparum infectivity through CSP ELISA. Our data revealed a high and similar allelic frequency for the kdr-L995F mutation in both treated and control communes (79% vs. 77%, p = 0.14) whilst allelic frequency of the ace-1 G280S mutation was lower across the study area (2–3%, p = 0.58). The sporozoite rate was 2.6% and 2.4% respectively in treated and untreated communes (p = 0.751). No association was found between Plasmodium falciparum infection in Anopheles gambiae s.l. vectors and carriage of kdr-L995F and ace-1 G280S mutations regardless of genotypes. The study findings underline the need for an integrated approach to malaria control, combining different control methods to effectively target transmission. Regular monitoring of insecticide resistance and genetic mutations is essential to guide control strategies