Genetic mechanism for soil-surface roots originating from a New Plant Type rice (Oryza sativa L.)

A new method of using seedling trays to evaluate root angle distribution in rice (Oryza sativa. L) was developed. By using this method, the root angle distributions of 97 accessions were characterized into two cluster groups ; A and B. The numbers of accessions in group A were limited, and these were categorized as shallow rooting types including soil-surface root. Group B included from shallow to deep rooting types, including both Indica and Japonica Group cultivars, lowland and upland cultivars, and landraces and improved types. An introgression line YTH16 harboring chromosome segments from a New Plant Type cultivar IR65600-87-2-2-3 with genetic background of an Indica Group rice IR 64, was included in Group A. To clarify the genetic mechanism for soil-surface rooting, quantitative trait loci (QTL) analysis was performed using hybrid populations derived from a cross between IR 64 and YTH16. A total of 8 QTLs were detected in the 3 introgressed segments on chromosomes (chr.) 2, 5 and 7. Seven chromosome segment lines (CSLs) combining these 3 QTL regions were selected from the progenies. The 2 CSLs harboring a single region (excluding the CSL with a region on chr. 5) showed high soil-surface root scores and low root vertical angles (RVA) in comparison with IR 64. Four CSLs harboring 2 or 3 regions showed high scores and low RVAs in comparison with YTH16 and the CSLs harboring a single QTL region. These results indicated that the soil-surface and shallow rooting of YTH16 was controlled by the 2 major QTLs’ regions on chrs. 2 and 7, and that chr. 5 particularly played a role for supporting the effect with them.

研究紹介 (Research Reports)