Storage Root Shape Determination in Sweetpotato: Fifty Shades of Phosphorus

Phosphorus is a critical macronutrient required in all metabolic processes in the plant, including energy transfer, signal transduction, biosynthesis of macromolecules, photosynthesis, and respiration. Plants acquire phosphorus in the form of phosphate (Pi), the availability of which varies in agricultural soils. To cope with spatial and temporal Pi supply, plants have developed adaptive responses that remobilize internal Pi and maximize external Pi acquisition. The latter response involves the redesign of root system architecture to accelerate soil exploration. In sweetpotatoes, knowledge about how the root system adapts to temporal variability of Pi is limited. Past studies have generally shown that Pi treatments did not influence sweetpotato yields. Field experiments conducted in 2014 have revealed a differential response among sweetpotato cultivars to the presence or absence of supplemental Pi application. Some of these responses include variation in root mass and storage root shape. Using an aeroponics system, intra-cultivar variation in root development attributes was also observed. The absence of phosphorus in the nutrient medium did not prevent storage root formation but was associated with constrictions in storage roots. Results from the current work can help shed light on the role of phosphorus in storage root formation and shape determination and have potential direct agricultural applications through the development of cultivar-specific Pi recommendations.