| Research Abstract |
We used two parameters to evaluate the internode elongation ability in deep-water rice; position of the lowest elongated internode (LEI) and the rate of internodal elongation under rising water conditions (RIE). An F_2 population consisting of 155 plants derived from a cross between Taichung 65 (T65), a Japonica non-deep water rice, and Bhauda, an Indica typical deepwater rice, was used for QTL analysis. Genotyping of the F2 population was done using 93 RFLP and 21 SSR markers. QTL analysis was performed with QTL Cartographer v. 1.16c. Both simple interval mapping (SIM) and composite interval mapping (CIM) techniques were used. QTLs for the LEI position and RIE were declared significant at the threshold of 1% level with the LOD score higher than 3.4, given by 5000 permutations. The LEI position of T65 and Bhauda was 13.7 and 6.4, and RIE of them was 1.3 and 8.1 cm day^<-1>, respectively. Two QTLs for the LEI position were detected on chromosomes 3 and 12, and explained 79.3 % of phenot
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ypic variance. For RIE, two QTLs were detected on chromosomes 1 and 12, and explained 49.7 % phenotypic variance. In all QTLs, Bhadua alleles increased internode elongation ability. We selected two plants from 75 BC3F1 plants by using SSR markers RM6703, RM8136, RM282, RM6832, RM5479, and RM2197, and generated two BC3F2 populations. The population BC3F2-A was heterozygous for the qLEI3 region and fixed to T65 homozygous in the other QTL regions. Similarly, another BC3F1 plant that was heterozygous in the interval containing qLEI12/qRIE12 was selected to obtain the BC3F2-B population. The LEI of both populations fell within four LEI classes (10, 11, 12 and 13). However, no clear bimodal segregation was observed. It was also impossible to divide the segregation of RIE in BC3F2-B into distinct classes. We conducted QTL analyses in these populations. In the interval between the markers RM282 and fl03141, peak LOD was scored for LEI in the BC3F2-A population. In BC3F2-B, the LOD score peaked in the interval between markers RM5479 and fl12163 for both LEI and RIE. All the QTLs had additive effects and showed a slight dominance effect. In the other heterozygous regions, no QTL was detected. Less
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