Root Growth and Development Under Heat and Water Stresses: A Comparative Study Determining Independent and Combined Effects in Four Grain Legume Species

Thanks to their ability to fix atmospheric dinitrogen in symbiosis with soil bacteria, grain legumes provide a sustainable way to ensure food and nutritional security. Unfortunately, these crops are highly susceptible to environmental constraints such as heat or water stresses which leads to fluctuating yield as compared to cereals one. As such, grain legumes are under-represented in the worldwide agriculture. In the context of climate change, more frequent episodes of heat stress, concomitant (or not) with water stress are expected. This emphasizes the need to identify key plant traits towards a better yield stability under stressful conditions.

Because drought tolerance is intimately linked to root phenotype, nodulated root development, root growth and performance in terms of water and N uptake were evaluated in four grain legumes (Pea, Faba bean, Lentil and Lupin), under factorial experiments with heat and water stress. To that aim, plants were grown during their vegetative stage in innovative RhizoTubes^TM on the high throughput phenotyping platform (4PMI, INRA, Dijon, France) equipped with imaging cabinets allowing daily automatic characterization of whole root systems. Contrasting adaptive strategies were identified among the four species under individual or combined stresses. For example, under heat stress, some species (such as lentil) maximized nodule growth at the expense of their roots while in other species (such as lupin), root growth was instead preferentially maintained. Moreover, this study underlined that few root morphological traits responded specifically to either one or the other stress. For most of root morphological traits, combined heat and water stresses were more impacting that when solely. Relationships between nodulated root traits and individual or combined stress responses will be discussed.

This study was supported by FP7-LEGATO project and its grant agreement FP7-289562 and by Terres Inovia.