UC Davis

Watercress (Nasturtium officinale R. Br.; Brassicaceae) is a highly nutritious leafy green vegetable consumed by customers globally. The peppery taste of watercress is the indicator of mustard oils which help reduce inflammation and chronic damage in cells and has been shown to have a role in cancer prevention in vitro. Watercress has a rich health-related phytonutrient profile including secondary plant metabolites glucosinolates (GLS), especially gluconasturtiin and its hydrolysis product phenethyl isothiocyantate (PEITC). We describe the development of the 259 F2 progeny mapping population and explored the effects of G x E interactions on phenotypic traits for a set of F4 lines with extreme phenotypes for growth, morphology, antioxidant capacity, and glucosinolates produced in contrasting field locations. After identifying and grouping the "extreme" lines, they were bulked and transcriptome analysis performed to identify differentially expressed candidate genes (DEG) on the phenylpropanoid biosynthesis pathways. Results indicated that the environment has a great impact on plant morphology and nutritional quality between the CA and UK sites. Plants grown in the CA site had higher biomass, thicker main stem with more stems, and a higher concentration of aromatic GLS. In a bulk-segregant RNA-Seq analysis, we identified 22 DEG (FDR<0.05) between the "high" and "low" selected GLS phenotype bulks, and four gene families (IPR029063, IPR004813, IPR001128, IPR025610) encoding key regulators in GLS biosynthesis.