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sur le développement des zones arides et semi-arides

Titre : Natural allelic diversity and signal responses associated with water deficit tolerance in Solanum tuberosum Group Phureja

Auteur : Diaz Valencia, Paula Andrea

Etablissement de soutenance : Universidad Nacional de Colombia

Grade : Doctor en Ciencias Agrarias 2022

Résumé
Genetic improvement of diploid potato (Solanum tuberosum Group Phureja) for water deficit tolerance and tuber yield is challenging because of the complex nature of these traits. In order to develop a research that cconsiders the complexity of the trait and simultaneously to make the experiments more tractable, we conducted two studies. The first was conducted to investigate the genetic architecture of the water deficit tolerance by employing the Working Collection of the Potato Breeding Program at the Universidad Nacional de Colombia. A diversity panel of 104 diploid potato accessions were evaluated under both well-watered and water deficit treatments at tuber initiation stage. The response to water deficit conditions was assessed with the relative chlorophyll content (CC), the maximum quantum efficiency of PSII (Fv/Fm), relative water content (RWC), leaf sugar content, tuber number per plant (TN), and tuber fresh weight per plant (TW). The phenotypic evaluation results revealed that the physiological, biochemical and yield-component variables had a broad variation, while the yield-component variables more powerfully distinguished between the tolerant and susceptible genotypes than the physiological and biochemical variables. The multivariate analysis based on the Drought Tolerance Index (DTI) revealed different levels of water deficit tolerance for the 104 genotypes. The Genome-Wide Association Studies (GWAS) was conducted using a matrix of 47 K single nucleotide polymorphisms (SNP), recently available for this population. We are reporting 38 Quantitative Trait Loci (QTL), seven for well-watered conditions, twenty-two for water deficit condition,s and nine for DTI which explain between 12.6% and 44.1% of the phenotypic variance. A set of 6 QTL were found to be associated with more than one variable. Of the nine QTL detected from DTI on chromosomes 2, 3, 5, 8, 10 and 12, three candidate genes with a feasible role in water deficit response were identified. These results provide a foundation for future research directed at understanding the molecular mechanisms underlying potato tolerance to water deficits, and the QTL identified could be used in marker-assisted selection (MAS) for water-deficit tolerance breeding in potato. In the second study, we investigated the physiological, biochemical and yield-related variables of four contrasting water-deficit tolerance diploid potato genotypes to water deficit with emphasis on temporal trend responses. Comparative analysis successfully identified that the physiological changes were faster and pronounced in the water-deficit sensitive genotypes. In contrast, in the tolerant genotypes water deficit induced earlier and more remarkable accumulation of sucrose and glucose. The observed temporal response showed that statistical differences between tolerant and sensitive genotypes in ψl, CC, and soluble sugar content can be distinguished from 3DAT. In general, the temporal variation in physiological and biochemical parameters demonstrated the presence of different strategies among tolerant genotypes. These results can contribute to a better understanding of the temporal physiological and biochemical mechanisms leading to water-deficit tolerance and will help potato breeding programs with improved stress tolerance and stable yields under changing climate conditions without the loss of yield potential under optimal conditions. The results of this study provide insights into the nature of genetic variations governing water deficit tolerance in diploid potato. Knowledge gained of the dissection may be utilized in breeding programs to select lines with improved yield and water deficit tolerance. Additionally, the information from the panel SNP polymorphisms and candidate gene detection provides research avenues to further refine/narrow down genomic regions associated with these agronomically important traits, and also opens gates for genetic enhancement through genomic aided selection.

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