Establishment of resistance to stresses caused by soil moisture fluctuation through strengthening the ability of plastic response ability of root system in rice

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This study aimed to examine the functional roles of the ability of the plant to change its development as environmental conditions change, which is known as phenotypic plasticity in crop adaptation to water stress such as drought as well as soil moisture fluctuation stress, and. We conducted a series of experiments to evaluate the functional roles of root plasticity by using various accessions/populations such as OryzaSNP germplasm set, chromosome segment substitution lines (CSSL) derived from Nipponbare and Kasalath cross, IR 64 INLs and a few promising genotypes for stress tolerance including NERICA (New Rice for Africa that is an interspecific cross between Oryza sativa and Oryza glaberrima). We used the rootbox-pinboard method, slant tube method, experimental bed installed with line source sprinkler system that can create gradient in drought stress intensities, and sloping bed that can create increasing rooting depths under field conditions for phenotyping root traits. These results consistently showed that in addition to deep roots, the plastic development of the root system is a key trait for plant adaptation to water stress. We also found that the plasticity in development of the entire root system is important in response to progressive drought, while that in lateral root development and aerenchyma formation is important in response to transient drought and O2 deficient conditions. We quantitatively showed the contributions of root plasticity to dry matter production through enhanced water uptake under water stress.