Genome-wide Approach to Identify Quantitative Trait Loci for Drought Tolerance in Tetraploid Potato (Solanum tuberosum L.)

Drought represents a major abiotic stress factor negatively affecting growth, yield and tuber quality in potato. Quantitative trait locus (QTL) analyses were performed in cultivated potato for drought tolerance index DRYM (deviation of relative starch yield from the experimental median), tuber starch content, tuber starch yield, tuber fresh weight, selected transcripts and metabolites under control and drought stress conditions. Eight genomic regions of major interest for drought tolerance were identified, three representing standalone DRYM QTL. Candidate genes, e.g., from signalling pathways for ethylene, abscisic acid and brassinosteroids, and genes encoding cell wall remodelling enzymes were identified within DRYM QTL. Bulked segregant analyses combined with next-generation sequencing were used to identify mutations in genes under the DRYM QTL on linkage group 3. Co-localisations of DRYM QTL and QTL for tuber starch content, tuber starch yield and tuber fresh weight with underlying genes of the carbohydrate metabolism were observed. Overlaps of DRYM QTL with metabolite QTL for ribitol or galactinol may indicate trade-offs between starch and compatible solute biosynthesis. Expression QTL confirmed the drought stress relevance of selected transcripts by overlaps with DRYM QTL. Future analyses of identified genes for drought tolerance will give a better insight into drought tolerance in potato.