2019 ASHS Annual Conference

Drought is a major abiotic stress affecting crop production. Characterization of genetic factors involved in plant response to water deficit is an important step towards breeding for drought-tolerant crops. Lettuce (Lactuca sativaL.), one of the major vegetable crops produced in the United States, consists of up to 95% water and is particularly prone to drought stress. To elucidate the genetic architecture underlying lettuce response to different water regimes, we subjected an interspecific F₈ recombinant inbred line (RIL) population derived from a cross between the cultivar Salinas and one of its wild relatives (L. serriola accession UC96US23) to optimal water and drought conditions. Drought stress was imposed by withholding water for 21 days when the plants were 4-weeks old. QTL mapping performed using a high-density linkage map comprised of 4,880 SNP markers revealed 21 QTL segregating for drought related traits. The phenotypic variation explained by these QTL ranged from 3.66% for relative water content (RWC) under optimal condition to 22.27% for RWC under drought condition. Wild lettuce accession UC96US23 contributed favorable alleles for the majority of the traits, suggesting its potential importance in introgression breeding for development of drought-tolerant lettuce cultivars.