Detection And Analysis Of QTL For Cold Tolerance At The Bud Bursting Period In Rice (Oryza Sativa L.)

Rice is one of the most important crops in the word. The cultivated rice (Oryza sativa L.) originated from tropical or subtropical areas is generally susceptible to cold temperatures below 15℃. Breeding for a high level of cold tolerance at the bud bursting period in rice is highly desirable. In the present study, mapping quantitative trait loci (QTL) controlling cold tolerance at the bud bursting period has been carried out among two recombinant inbred lines (RILs) derived from the cross of Asominori(japonica) and IR24(indica), IR36(indica) and Nekken 2(japonica), respectively. The contribution and effection of the QTLs detected from "Asominori/IR24" RILs were confirmed by the cold tolerance of AIS lines from the IR24 chromosome segment substitution lines (CSSLs). These QTLs and linked markers should be useful in breeding of varieties with high cold tolerance at the bud bursting period in marker assisted selection (MAS) program. The results were as follow:1. Detection of QTL for cold tolerance at the bud bursting period using recombinant inbred lines derived from the cross of Asominori and IR24A recombinant inbred line (RIL) population derived from the cross of Asominori (japonica) and IR24 (indica) was used to detect quantitative trait loci (QTL) for cold tolerance at the bud bursting period. A total of three QTLs controlling cold tolerance at the bud bursting period were detected on chromosome 5 and chromosome 12 with LOD of QTLs ranging from 2.9 to 4.7, named qCTBP-5-1, qCTBP-5-2 and qCTBP-12, and the individual QTL accounted for 19.21%, 12.00% and 12.21% of the total phenotypic variance, respectively. The positive cold tolerance effects of qSCT-5-2 at the bud bursting period came from japonica variety Asominori with strong cold tolerance, and the positive cold tolerance effects of the other two QTLs came from IR24 with weak cold tolerance.2. Graphical genotype analysis for cold tolerance at the bud bursting period in the CSSLsSome lines of IR24 chromosome segment substitution lines (CSSLs) with Asominori genetic background (AIS) derived from the cross of Asominori and IR24 were selected to confirm the existence of the putative QTL. The contribution and effection of qSCT-5-2 was confirmed by the cold tolerance at the bud bursting period of 2 AIS lines from the IR24 chromosome segment substitution lines (CSSLs).3. Detection of QTL for cold tolerance at the bud bursting period using recombinant inbred lines derived from the cross of IR36 and Nekken 2Another recombinant inbred line (RIL) population derived from the cross of IR36 (indica) and Nekken 2 (japonica) was also used to detect quantitative trait loci (QTL) for cold tolerance at the bud bursting period. A total of four QTLs controlling cold tolerance at the bud bursting period were detected on chromosome 4,5 and 7 with LOD of QTLs ranging from 2.1 to 4.6, named qCTBP-4-1,qCTBP-4-2,qCTBP-5 and qCTBP-7, and the individual QTL accounted for 10.17%,14.03%,15.95% and 4.55% of the total phenotypic variance, respectively. The positive cold tolerance effects of all the four QTLs came from japonica variety Nekken 2 with strong cold tolerance.