Using tube rhizotrons to measure variation in depth penetration rate among modern North-European winter wheat (Triticum aestivum L.) cultivars

Deeper plant root systems are desired for improved water and nitrogen uptake in leaching environments. However, phenotyping for deep roots requires methods that enable plants to develop deep roots under realistic conditions. Winter cereals raise further complications as early growth occurs under low light and temperature during autumn and winter-conditions not met in standard glasshouse facilities. This study used tube rhizotrons of 2 m length, positioned outdoor under a rainout shelter to screen for depth penetration rates (DPR) of roots. Rooting depths of 1 to 1.5 m were achieved with 23 widely grown North European winter wheat cultivars in two autumn/winter and two summer experiments and nine of the cultivars were represented in two or more experiments. Heritability of DPR of roots was only consistent in autumn/winter experiments (27 %) signifying the importance of phenotyping in relevant seasons and environments. Depth penetration rate of roots varied significantly within the tested cultivars, from 1.39 (+/- 0.35) mm A degrees C-1 day(-1) for cv. Tuareg to 2.07 (+/- 0.34) mm A degrees C-1 day(-1,) for cv. Mercedes. This study documented consistent differences of DPR among North-European winter wheat cultivars in long tube rhizotrons under semi-natural conditions, which may form part of future phenotyping facilities for deep rooting traits.