TOWARDS UNDERSTANDING THE MOLECULAR DYNAMICS OF COLD STRESS RESPONSE IN A TOLERANT POTATO SPECIES, SOLANUM COMMERSONII DUN.

It has been estimated that, with climate changes, the potato as well as all crop plants will be exposed to more unexpected events, ranging from abiotic to biotic stress conditions. These will reduce plant survival, production and geographic distribution (Beerling et al. 2000). Among abiotic stresses, cold is one of the suboptimal conditions that is more harmful to the cultivated potato, classified as frost-sensitive. Luckily, some wild potato species are frost hardy and capable of cold acclimation. Thus, they are a potential genetic resource for introgressing freezing tolerance into cultivated varieties. Among the wild potatoes, S. commersonii is the one displaying the highest tolerance to low temperatures and whose genome sequence has been deciphered (Aversano et al. 2015). Although the cold response machinery is widely studied in plant, the capacity of a genotype to tolerate low temperatures has not been fully understood yet and relatively little progress has been made in terms of breeding. This is partly due to the fact that the genetic control of cold tolerance is a quantitative and complex trait, with low heritability, presenting additive, dominance and epistatic gene actions. A combination of new and efficient approaches is necessary to accelerate the identification, characterization and effective exploitation of loci affecting tolerance to low temperatures not only in potato but in all crops. With these thoughts in mind, this thesis is aimed at investigating the molecular mechanisms contributing to cold tolerance in the potato species possessing the highest capacity to withstand low temperatures, S. commersonii. To reach our goals, we carried out a transcriptomic (RNAseq) (chapter II) and smallRNA (smRNAseq) (chapter III) analysis on two clones of S. commersonii contrasting in their ability to face cold. Chapter IV approaches the regulation of gene expression through RNA silencing. Indeed, a focus on DCL and RDR gene families in S. commersonii and S. tuberosum was given.