Identification of a Unique Genomic Region in Sweet Chestnut (Castanea sativa Mill.) That Controls Resistance to Asian Chestnut Gall Wasp Dryocosmus kuriphilus Yasumatsu.

The Asian chestnut gall wasp (ACGW) (Hymenoptera Dryocosmus kuriphilus Yasumatsu) is a severe pest of sweet chestnut (Castanea sativa Mill.) with a strong impact on growth and nut production. A comparative field trial in Central Italy, including provenances from Spain, Italy, and Greece, was screened for ACGW infestation over consecutive years. The Greek provenance Hortiatis expressed a high proportion of immune plants and was used to perform a genome-wide association study based on DNA pool sequencing (Pool-GWAS) by comparing two DNA pools from 25 susceptible and 25 resistant plants. DNA pools were sequenced with 50X coverage depth. Sequence reads were aligned to a C. mollissima reference genome and the pools were compared to identify SNPs associated with resistance. Twenty-one significant SNPs were identified and highlighted a small genomic region on pseudochromosome 3 (Chr 3), containing 12 candidate genes of three gene families: Cytochrome P450, UDP-glycosyltransferase, and Rac-like GTP-binding protein. Functional analyses revealed a putative metabolic gene cluster related to saccharide biosynthesis in the genomic regions associated with resistance that could be involved in the production of a toxic metabolite against parasites. The comparison with previous genetic studies confirmed the involvement of Chr 3 in the control of resistance to ACGW.

Introgression of a synthetic sex ratio distortion transgene into different genetic backgrounds of Anopheles coluzzii.

The development of genetically modified mosquitoes (GMM) and their subsequent field release offers innovative approaches for vector control of malaria. A non-gene drive self-limiting male-bias Ag(PMB)1 strain has been developed in a 47-year-old laboratory G3 strain of Anopheles gambiae s.l. When Ag(PMB)1 males are crossed to wild-type females, expression of the endonuclease I-PpoI during spermatogenesis causes the meiotic cleavage of the X chromosome in sperm cells, leading to fertile offspring with a 95% male bias. However, World Health Organization states that the functionality of the transgene could differ when inserted in different genetic backgrounds of Anopheles coluzzii which is currently a predominant species in several West-African countries and thus a likely recipient for a potential release of self-limiting GMMs. In this study, we introgressed the transgene from the donor Ag(PMB)1 by six serial backcrosses into two recipient colonies of An. coluzzii that had been isolated in Mali and Burkina Faso. Scans of informative Single Nucleotide Polymorphism (SNP) markers and whole-genome sequencing analysis revealed a nearly complete introgression of chromosomes 3 and X, but a remarkable genomic divergence in a large region of chromosome 2 between the later backcrossed (BC6) transgenic offspring and the recipient paternal strains. These findings suggested to extend the backcrossing breeding strategy beyond BC6 generation and increasing the introgression efficiency of critical regions that have ecological and epidemiological implications through the targeted selection of specific markers. Disregarding differential introgression efficiency, we concluded that the phenotype of the sex ratio distorter is stable in the BC6 introgressed An. coluzzii strains.

Advances in biocultural geography of olive tree (Olea europaea L.) landscapes by merging biological and historical assays.

Olive tree is a vector of cultural heritage in Mediterranean. This study explored the biocultural geography of extra virgin olive oil (EVOO) from the cultivar Ogliarola campana in Campania region, Italy. Here, the rich cultural elements related to olive tree and oil represent a suitable case study for a biocultural analysis. We joined analytical techniques, based on stable isotopes and trace elements of EVOOs, with humanistic analyses, based on toponymy and historical data. In order to provide a science-based assessment of the terroir concept, we set up a new method of data analysis that inputs heterogeneous data from analytical and anthropic variables and outputs an original global evaluation score, named terroir score, as a measure of biocultural distinctiveness of the production areas. The analysis highlighted two distinct cultural sub-regions in the production area of Ogliarola campana: a continental cluster in the inner area of Irpinia and a coastal one around Salerno province. Finally, a biocultural map displays the diversity of heterogeneous variables and may support science-based decision making for territory valorisation. This novel biocultural analysis is a promising approach to substantiate the terroir concept with science-based elements and appears suitable to characterize local agri-food products with old tradition and historical data.

Decision tree for mapping of halophyte cover around Ghannouch, Tunisia.

Environment of Ghannouch in the south-east of Tunisia is characterized by the wide-spread hypersaline soils, typically colonized by halophytes. The study of their distribution is required in order to reveal the extent of salinization and its dynamic. Mapping and monitoring with a remote sensing approach are foreseen as the ways to trace the spatial and temporal dimensions of the phenomenon. The identification of halophyte vegetation can take advantage by analyzing optical remote sensing data. Here, we propose using a decision tree approach applied to European Space Agency Sentinel-2 imagery, for an accurate land cover mapping of Ghannouch district in Gabès governorate. Data pre-processing was carried out using the European Space Agency's Sentinel Application Platform and the SEN2COR toolboxes. The mapping approach combines the spectral information in several channels of the visible-near-infrared spectrum. The land cover identification was performed following a spectral classification approach, exploiting several optical indices, normalized difference water index, normalized difference vegetation index, and several soil salinity index, in order to elaborate a decision tree algorithm. As a result, for an area of interest of 50 × 50 km2, at least 68% was classified as halophyte land cover. This mapping exercise represents an important step toward improved halophytes mapping in Tunisia and could be used to monitor the status of other salinity prone regions in the world.

Rethinking the history of common walnut (Juglans regia L.) in Europe: Its origins and human interactions.

Common walnut (Juglans regia L) is an economically important species cultivated worldwide for its high-quality wood and nuts. It is generally accepted that after the last glaciation J. regia survived and grew in almost completely isolated stands in Asia, and that ancient humans dispersed walnuts across Asia and into new habitats via trade and cultural expansion. The history of walnut in Europe is a matter of debate, however. In this study, we estimated the genetic diversity and structure of 91 Eurasian walnut populations using 14 neutral microsatellites. By integrating fossil pollen, cultural, and historical data with population genetics, and approximate Bayesian analysis, we reconstructed the demographic history of walnut and its routes of dispersal across Europe. The genetic data confirmed the presence of walnut in glacial refugia in the Balkans and western Europe. We conclude that human-mediated admixture between Anatolian and Balkan walnut germplasm started in the Early Bronze Age, and between western Europe and the Balkans in eastern Europe during the Roman Empire. A population size expansion and subsequent decline in northeastern and western Europe was detected in the last five centuries. The actual distribution of walnut in Europe resulted from the combined effects of expansion/contraction from multiple refugia after the Last Glacial Maximum and its human exploitation over the last 5,000 years.

Isoscapes of carbon and oxygen stable isotope compositions in tracing authenticity and geographical origin of Italian extra-virgin olive oils.

The authentication and verification of the geographical origin of food commodities are important topics in the food sector. This study shows the spatial variability in δ(13)C and δ(18)O of 387 samples of Italian extra-virgin olive oil (EVOO) collected from 2009 to 2011. EVOOs' δ(13)C and δ(18)O values were related to GIS (Geographic Information System) layers of source water δ(18)O and climate data (mean monthly temperature and precipitation, altitude, xerothermic index) to evaluate the impact of the most significant large-scale drivers for the isotopic composition of Italian EVOOs. A geospatial model of δ(18)O and δ(13)C was developed for the authentication and verification of the geographical origin of EVOOs. The geospatial model identified EVOOs from four distinct areas: north, south-central Tyrrhenian, central Adriatic and islands, highlighting the zonation of the expected isotopic signatures. This geospatial approach can be used to define a protocol for analyzing the isotopic composition of EVOOs in order to certify their origin and prevent food fraud. Limits and perspectives of the model are discussed.