Plasticity in Root Length and Volume Through the Alternate Wetting and Drying Water Management in Rice

Saving water via rational management in paddy rice require efforts to minimize risks to food security, whether consider that its adoption by farmers generally lead to lower grain productivity. Recently, studies by meta-analysis approaches highlight that when soil water potential was higher than -20 kPa, grain yields are not significantly decreased. In this context, new efforts should be done by rice breeders aiming to improve the plant performance when submitted to a more severe alternate wetting and drying (AWD) aiming to face the increasingly extreme climatic events in the next decades. Thus, in this first-tier of the study, our main objective was to evaluate the responses of a genotypes set (cultivars and elite line) for some root traits plasticity and its potential to change gas exchange attributes and grain yield when plants are subjected to severe AWD irrigation management, even when soil water potential beyond this threshold (when soils dried beyond -20 kPa, even reaching -40 kPa). Our data highlight that the mean grain yield across genotypes ranged from 9.25 to 12.65 ton/ha when maintained under continuous flooding (CF) and from 9.52 to 11.67 ton/ha at AWD water management. Root plasticity responses across evaluated genotypes under AWD management were highlighted; BRS Pampa cultivar and Titan CL hybrid showed the greater plasticity index for total root length and total root volume. Data suggests that under severe AWD management, root plasticity in terms of more total root length and total root volume at 0-20 cm depth can leads to some contribution degree for higher grain yield and for its stability under AWD practice. These results can serves as a starting point to additional efforts via physiological breeding approaches aiming the construction of rice plant ideotypes more suitable for AWD management, especially take into account its contributions to mitigate potential impacts of future climate changes on food security.