Insecticide Resistance and Metabolic Mechanisms in Aedes aegypti from Two Agrosystems (Vegetable and Cotton Crops) in Côte d'Ivoire

Background: The emergence of insecticide resistance in Aedes vectors mosquitoes poses a real challenge for arboviral-borne disease control. In Côte d'Ivoire, data are available on phenotypic resistance and the presence of kdr mutations in Aedes aegypti. Therefore, information on metabolic resistance in Aedes populations is very scarce. Here, we assessed the insecticide resistance status of Ae. aegypti in periurban and rural areas of Côte d'Ivoire, and we investigated the role of detoxification enzymes as possible resistance mechanisms. Materials and Methods: Aedes mosquito eggs were collected between June 2019 to April 2021 in two agricultural sites. Adults of Ae. aegypti were tested using World Health Organization tube assays, with seven insecticides belonging to pyrethroids, organochlorines, carbamates, and organophosphates classes. We determined the knockdown times (KdT50, KdT95) and resistance ratios of pyrethroids in natural populations. The synergist piperonyl butoxide (PBO) was used to investigate the role of enzymes in resistance. Biochemical assays were performed to detect potential increased activities in mixed-function oxidase levels, nonspecific esterases (NSEs), and glutathione S-transferases. Results: The results showed that Ae. aegypti populations were resistant to five insecticides with mortality of 46% and 89% for 0.75% permethrin, 68% and 92% for 0.05% deltamethrin, 57% and 89% for lambda-cyhalothrin, 41% and 47% for dichlorodiphenyltrichloroethane (DDT), 82% and 91% for chlorpyrifos-methyl in Songon-Agban and Kaforo, respectively. Susceptibility to carbamates was observed in our study sites. After exposure to PBO, the susceptibility of Ae. aegypti to pyrethroids and DDT was partially restored in Songon-Agban. Whereas in Kaforo, none increase of the mortality rates of Ae. aegypti for these four insecticides was observed after exposure to PBO. Increased activity of NSE (α-esterases) was found in Songon-Agban compared with the reference susceptible strain. Conclusion: These findings provide valuable information to support decisions for vector control strategies in Cote d'Ivoire. Also, we highlight the need for the monitoring of insecticide resistance management in Aedes vectors.

Soil Bacterial Communities from Three Agricultural Production Systems in Rural Landscapes of Palmira, Colombia

Soils play important roles in the proper functioning of agroecosystems. Using molecular characterization methods such as metabarcoding, soils from eight farms (57 samples) belonging to three production system types-agroecological (two farms with twenty-two sampling points), organic (three farms with twenty-one sampling points), and conventional (three farms with fourteen sampling points)-were compared from the rural villages of El Arenillo and El Mesón in Palmira, Colombia. Amplification and sequencing of the hypervariable V4 region of the 16S rRNA gene was performed using next-generation sequencing (Illumina MiSeq) to estimate the bacterial composition and the alpha and beta diversity present. Across all soil samples, we found 2 domains (Archaea and Bacteria), 56 phylum, 190 classes, 386 orders, 632 families, and 1101 genera to be present. The most abundant phyla in the three systems were Proteobacteria, (agroecological 28%, organic 30%, and conventional 27%), Acidobacteria (agroecological 22%, organic 21%, and conventional 24%), and Verrucomicrobia (agroecological 10%, organic 6%, and conventional 13%). We found 41 nitrogen-fixing and phosphate-dissolving genera which promote growth and pathogens. Alpha and beta diversity indices were very similar across the three agricultural production systems, as reflected by shared amplicon sequence variants (ASVs) among them, likely due to the proximity of the sampling sites and recent management changes.

Extensive pollen-mediated gene flow across intensively managed landscapes in an insect-pollinated shrub native to semiarid habitats

Our knowledge of the impact of landscape fragmentation on gene flow patterns is mainly drawn from tropical and temperate ecosystems, where landscape features, such as the distance of a tree to the forest edge, drive connectivity and mating patterns. Yet, the structure of arid and semiarid plant communities - with open canopies and a scattered distribution of trees - differs greatly from those that are well-characterized in the literature. As a result, we ignore whether the documented consequences of landscape fragmentation on plant mating and gene flow patterns also hold for native plant communities in arid and semiarid regions. We investigated the relative contribution of plant traits, pollinator activity, and individual neighbourhood in explaining variation in mating and gene flow patterns of an insect-pollinated semiarid arborescent shrub, Ziziphus lotus, at three sites embedded in highly altered agriculture landscapes. We used 14 SSRs, seed paternity analyses, and individual mixed effect mating models (MEMMi) to estimate the individual mating variables and the pollen dispersal kernel at each site. Individual spatial location, flower density, and floral visitation rate explained most of the variation of mating variables. Unexpectedly, individual correlated paternity was very low and shrubs surrounded by the most degraded matrix exhibited an increased fraction of pollen immigration and a high effective number of pollen donors per mother shrub. Overall, our results reveal that an active pollinator assemblage ensures highly efficient mating, and maintains pollen-mediated gene flow and notable connectivity levels, even in highly altered landscapes, potentially halting genetic isolation within and between distant sites.

Crop-to-wild gene flow and its fitness consequences for a wild fruit tree: Towards a comprehensive conservation strategy of the wild apple in Europe

Crop-to-wild gene flow can reduce the fitness and genetic integrity of wild species. Malus sylvestris, the European crab-apple fruit tree in particular, is threatened by the disappearance of its habitat and by gene flow from its domesticated relative, Malus domestica. With the aims of evaluating threats for M. sylvestris and of formulating recommendations for its conservation, we studied here, using microsatellite markers and growth experiments: (i) hybridization rates in seeds and trees from a French forest and in seeds used for replanting crab apples in agrosystems and in forests, (ii) the impact of the level of M. domestica ancestry on individual tree fitness and (iii) pollen dispersal abilities in relation to crop-to-wild gene flow. We found substantial contemporary crop-to-wild gene flow in crab-apple tree populations and superior fitness of hybrids compared to wild seeds and seedlings. Using paternity analyses, we showed that pollen dispersal could occur up to 4 km and decreased with tree density. The seed network furnishing the wild apple reintroduction agroforestry programmes was found to suffer from poor genetic diversity, introgressions and species misidentification. Overall, our findings indicate supported threats for the European wild apple steering us to provide precise recommendations for its conservation.