N- and P-mediated seminal root elongation response in rice seedlings

Aims: In rice, seminal root elongation plays an important role in acquisition of nutrients such as N and P, but the extent to which different N forms and P concentrations affect root growth is poorly understood. This study aimed to examine N- and P-mediated seminal root elongation response and to identify putative QTLs associated with seminal root elongation. Methods: Seminal root elongation was evaluated in 15 diverse wild and cultivated accessions of rice, along with 48 chromosome segment substitution lines (CSSLs) derived from a cross between the rice variety 'Curinga' and Oryza rufipogon (IRGC 105491). Root elongation in response to different forms of N (NH ₄ ⁺ , NO ₃ ^- and NH ₄ NO ₃ ) and concentrations of P was evaluated under hydroponic conditions, and associated putative QTL regions were identified. Results: The CSSL parents had contrasting root responses to N and P. Root elongation in O. rufipogon was insensitive to N source and concentration, whereas Curinga was responsive. In contrast to N, seminal root elongation and P concentration was positively correlated. Three putative QTLs for seminal root elongation in response to N were detected on chromosome 1, and one QTL on chromosome 3 was associated with low P concentration. Conclusions: Genetic variation in seminal root elongation and plasticity of nutrient response may be appropriate targets for marker-assisted selection to improve rice nutrient acquisition efficiency.