Influencia del vigor de la raíz sobre la resistencia a la sequía de dos variedades de patata

Resum

Potato consumes the most irrigation water in the United Kingdom, so improving crop water use efficiency could be essential for sustainable agriculture. Potato is a relatively drought-sensitive species. However, water saving irrigation techniques can be applied to drought resistant varieties in the later stages to maintain yield despite applying less water. Optimising irrigation practices requires a good understanding of the physiological mechanisms allowing superior performance of drought tolerant varieties. A series of experiments aimed to explain why the Horizon variety is more drought resistant than the commonly used Maris Piper variety. Plants were grown in a polytunnel (to prevent rainfall compromising the experimental design) and irrigation was automatically scheduled based on defined soil moisture thresholds. Both varieties received four different irrigation treatments during the tuber bulking stage: full irrigation (FI), partial root-zone drying with the dry side alternating (PRD-A), partial root-zone drying with wet and dry sides fixed (PRD-F), and full root-zone drying (WRD) in decreasing order of amount of water applied. Tuber yield decreased with irrigation volume applied in Maris Piper but not in Horizon. This was related to the higher root density of Horizon in deep (> 40 cm) permanently wet soil layers. When plants were grown in 5 L pots in a glasshouse experiment over two months, no varietal differences in gas exchange, leaf water potential, leaf xylem abscisic acid concentration, and shoot biomass were found in responses to soil water deficits. Under well watered conditions, root growth during the first month was much higher in Horizon, but water deficit dramatically reduced this difference. Therefore, Horizon seems to maintain yield by rapidly securing access to water stored in deep moist layers. However, this advantage may require sufficiently deep soils and adequate water conditions (achieved by irrigation or rainfall) in the early stages after emergence.