Saliou Ndiaye

Influence of irrigation on the distribution and control of the nematode Meloidogyne javanica by the biocontrol bacterium Pasteuria penetrans in the field

Pasteuria penetrans, a bacterial parasite of plant-parasitic nematodes, is used to control root-knot nematode Meloidogyne spp. populations in vegetable crops. But its efficiency is variable, mostly because of the patchy distribution of the bacteria in arable fields. As the infective P. penetrans are non-motile bacteria in soil, abiotic soil factors can affect the bacteria–nematode relationships. An epidemiological study, conducted in a vegetable field, showed that abiotic factors such as irrigation, soil water holding capacity and texture, affected the efficiency of P. penetrans. A correspondence analysis between these abiotic factors and the density of P. penetrans spores in the soil, and the proportion of Meloidogyne javanica juveniles infected by the bacteria, revealed that irrigation affected directly the distribution of the spores in soil pores related to their passive transport by water flow. Laboratory experiments conducted on the passive transport of spores confirmed that intensive irrigation leached the spores down the soil profile and decreased the percentage of infected Meloidogyne juveniles.

Genetic diversity and phylogenetic relationships in local cattle breeds of Senegal based on autosomal microsatellite markers.

Aim: In Senegal, uncontrolled cross-breeding of cattle breeds and changes in production systems are assumed to lead to an increase of gene flow between populations. This might constitute a relevant threat to livestock improvement. Therewith, this study was carried out to assess the current genetic diversity and the phylogenetic relationships of the four native Senegalese cattle breeds (Gobra zebu, Maure zebu, Djakoré, and N’Dama). Methods: Genomic DNA was isolated from blood samples of 120 unrelated animals collected from three agro-ecological areas of Senegal according to their phenotypic traits. Genotyping was done using 11 specific highly polymorphic microsatellite makers recommended by Food and Agriculture Organization. The basic measures of genetic variation and phylogenetic trees were computed using bioinformatics’ software. Results: A total of 115 alleles were identified with a number of alleles (Na) at one locus ranging from 6 to 16. All loci were polymorphic with a mean polymorphic information content of 0.76. The mean allelic richness (Rs) lay within the narrow range of 5.14 in N’Dama taurine to 6.10 in Gobra zebu. While, the expected heterozygosity (HE) per breed was high in general with an overall mean of 0.76±0.04. Generally, the heterozygote deficiency (FIS) of 0.073±0.026 was relatively due to inbreeding among these cattle breeds or the occurrence of population substructure. The high values of allelic and gene diversity showed that Senegalese native cattle breeds represented an important reservoir of genetic variation. The genetic distances and clustering trees concluded that the N’Dama cattle were most distinct among the investigated cattle populations. So, the principal component analyses showed qualitatively that there was an intensive genetic admixture between the Gobra zebu and Maure zebu breeds. Conclusions: The broad genetic diversity in Senegalese cattle breeds will allow for greater opportunities for improvement of productivity and adaptation relative to global changes. For the development of sustainable breeding and crossbreeding programs of Senegalese local breeds, effective management is needed towards genetic selection and transhumance to ensure their long-term survival.

Preliminary Study of Fish Assemblage Structure of the Marine Protected Area of Cayar in Senegal

Preliminary Study of Fish Assemblage Structure of the Marine Protected Area of Cayar in Senegal Since its establishment in 2004, Cayar Marine Protected area (North of Senegal) is characterized by a lack of information on its fish fauna. Therefore, it becomes necessary to characterize the fish fauna of this MPA and its dynamics in time and space for a sustainable management of this conservation area. This present study investigated seasonal and spatial structure of the fish assemblage of Cayar MPA. This study consisted of collaborative seasonal sampling with local communities from six stations within the four main fishing areas with two types of fishing gears, purse seine and long line between 2015 and 2016. Ecological and trophic classification was performed in order to determine the fish fauna nature of this MPA. Multivariate analysis like factorial correspondence analysis and hierarchical classification analysis were carried out to study spatial and seasonal structure of fish assemblage of Cayar MPA. A total of 103 fish species from 45 families were reported. The most abundant species and the richest family were Pagellus bellottii and Carangidae, respectively. The fish assemblage was dominated by species of marine affinity and predators. Spatial and seasonal fish assemblages differed both in terms species richness and fish abundance. The highest and lowest species richness and abundance were recorded during the cold season and cold to warm transition period, respectively. A clear separation was found between stations where purse seine and long line were applied, in species composition and abundance. Results from this study might serve as the reference point of the fish assemblage in Cayar MPA. However, further investigation on the environmental variability is needed for a better understanding of the observed fish assemblage organization in time and space.