Quick and efficient approach to develop genomic resources in orphan species: application in Lavandula angustifolia

Next-Generation Sequencing (NGS) technologies, by reducing the cost and increasing the throughput of sequencing, have opened doors of research efforts to generate genomic data to a range of previously poorly studied species. In this study, we proposed a method for the rapid development of a large scale molecular resources for orphan species. We studied as an example Lavandula angustifolia, a perennial sub-shrub plant native from the Mediterranean region and whose essential oil have numerous applications in cosmetics, pharmaceuticals, and alternative medicines.\n\nWe first built a Maillette reference Unigene, compound of coding sequences, thanks to de novo RNA-seq assembly. Then, we reconstructed the complete genes sequences (with exons and introns) using a transcriptome-guided DNA-seq assembly approach in order to maximize the possibilities of finding polymorphism between genetically close individuals. Finally, we used these resources for SNP mining within a collection of 16 lavender clones and tested the SNP within the scope of a phylogeny analysis. We obtained a cleaned reference of 8, 030 functionally annotated genes (in silico annotation). We found up to 400K polymorphic sites, depending on the genotype analyzed, and observed a high SNP frequency (mean of 1 SNP per 90 bp) and a high level of heterozygosity (more than 60% of heterozygous SNP per genotype). We found similar genetic distances between pairs of clones, related to the out-crossing nature of the species, the restricted area of cultivation and the clonal propagation of the varieties.\n\nThe method propose is transferable to other orphan species, requires little bioinformatics resources and can be realized within a year. This is the first reported large-scale SNP development on Lavandula angustifolia. All this data provides a rich pool of molecular resource to explore and exploit biodiversity in breeding programs.