UC Davis

Watercress (Nasturtium officinale R. Br.; Brassicaceae) is a highly nutritious leafy green vegetable consumed globally, with a rich health-related phytonutrient profile that includes the secondary plant metabolites glucosinolates (GLS), especially gluconasturtiin and its hydrolysis product phenethyl isothiocyanate (PEITC). The peppery taste and pungency of watercress comes from these mustard oils, and they are known to help reduce inflammation and chronic damage in cells and have been shown to have a role in cancer prevention in vitro and in vivo. We explored how both genotype and highly contrasting environments of California (CA) and the United Kingdom (UK) alter phenotypic traits for a set of F2:4 genotypes created from a unique bi-parental cross, chosen for their extreme phenotypes for yield, leaf and branch morphology, antioxidant capacity, and glucosinolate content in two contrasting field locations. Although both genotype and environment had a significant impact on plant morphology, nutritional quality, and yield, overall, the highly contrasting environments of California and the UK, had a much stronger effect. Plants grown in CA had higher biomass, thicker main stem and more branches, and a higher concentration of aromatic GLS, whilst plants grown in the UK had larger leaves with longer stems, suggesting a better harvestable product, at least for a salad and not a soup crop. Significant G x E interactions were observed for multiple traits, suggesting significant phenotypic plasticity of watercress and variation between genotypes that will enable the selection of ideotypes suitable for these highly contrasting growth environments, that can be considered as the ‘extremes’ of an environmental gradient where the crop might be grown, from the warm and dry soil-grown conditions of California to the relatively cool and wet aquatic growing system of the UK.