Continuous Flooding or Alternate Wetting and Drying Differently Affect the Accumulation of Health-Promoting Phytochemicals and Minerals in Rice Brown Grain

Climate changes impose adoption of water-saving techniques to improve the sustainability of irrigated rice systems. This study was aimed, by a two-years side-by-side comparison, at verifying the hypothesis whether Alternate Wetting and Drying (AWD) affects the concentrations of health-related compounds and minerals in brown grains of three japonica rice (Oryza sativa L.) cvs ('Baldo', 'Gladio', and 'Loto') usually grown in temperate areas in continuous flooding (CF). Due to the rotational turns in water distribution imposed by local authorities and to the weather behavior, different AWD timing and severity occurred in the two years of the study. AWD induced in both seasons yield losses in 'Baldo' and 'Gladio' but not in 'Loto'. In the brown grains of 'Loto', AWD increased the concentrations of total tocols, gamma-oryzanol, flavonoids, and the antioxidant activity. AWD affected the concentrations of minerals, particularly increasing copper, cadmium and nickel, and decreasing manganese, arsenic and zinc. In the sensitive cultivars, 'Baldo' and 'Gladio', AWD seems to affect plant yield, rather than for severity of the dry period, for prolonged absence of ponded water that exposes plants to cooler temperatures. The selection of suitable cultivars, like 'Loto', tolerant to AWD-related stresses, could combine environmental, yield-related, and nutritional benefits improving the product quality.