Watercress (Nasturtium officinale R. Br.) is a highly nutritious leafy crop with a rich health-related phytonutrient profile including secondary plant metabolites such as glucosinolates. This semi-aquatic crop is well-suited for indoor hydroponic cultivation and has a growing market for its distinctive peppery taste and health benefits. We describe crop trials in three contrasting environments and report the changes to plant morphology, yield, and nutritional profile under varying blue light treatments. Yield and glucosinolate quantity were significantly increased in a vertical farm system enriched in blue light, relative to field-grown crops. Additionally, PBITC, a glucosinolate not previously identified in field-grown watercress, was found in plants grown in a vertical farm. This work demonstrates the great potential of watercress in a new era of controlled environment agriculture to deliver improved health benefits to customers.

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.

Watercress (Nasturtium officinale) is a nutrient-dense salad crop with high antioxidant capacity and glucosinolate concentration and with the potential to contribute to nutrient security as a locally grown outdoor aquatic crop in northern temperate climates. However, phosphate-based fertilizers used to support plant growth contribute to the eutrophication of aquatic habitats, often pristine chalk streams, downstream of farms, increasing pressure to minimize fertilizer use and develop a more phosphorus-use efficient (PUE) crop. Here, we grew genetically distinct watercress lines selected from a bi-parental mapping population on a commercial watercress farm either without additional phosphorus (P-) or under a commercial phosphate-based fertilizer regime (P+), to decipher effects on morphology, nutritional profile, and the transcriptome. Watercress plants sustained shoot yield in P- conditions, through enhanced root biomass, but with shorter stems and smaller leaves. Glucosinolate concentration was not affected by P- conditions, but both antioxidant capacity and the concentration of sugars and starch in shoot tissue were enhanced. We identified two watercress breeding lines, with contrasting strategies for enhanced PUE: line 60, with highly plastic root systems and increased root growth in P-, and line 102, maintaining high yield irrespective of P supply, but less plastic. RNA-seq analysis revealed a suite of genes involved in cell membrane remodeling, root development, suberization, and phosphate transport as potential future breeding targets for enhanced PUE. We identified watercress gene targets for enhanced PUE for future biotechnological and breeding approaches enabling less fertilizer inputs and reduced environmental damage from watercress cultivation.