Development Of The Chromosome Segment Substitution Lines Derived From The Reciprocal Genetic Background Of Changhui121and Koshihikari

Chromosome segment substitution lines was a series of near-isogenic lines whichcovering the whole genome of crop and developed by backcross and molecular markerassisted selection. Using the substitution lines to map gene/QTL would be able toeliminate the interference of genetic background and achieve fine positioning. In this study,two sets of chromosome segment substitution lines （CSSLs） of Koshihikari, a japonica ricevariety with world famous good quality, and Chang Hui121, a indica rice variety withstrong restoring ability and fine combining ability, as reciprocal genetic background wereconstructed. The major results are as follows:（1）A total of625pairs of SSR primers were used to detected the polymorphismbetween Changhui121and Koshihikari. Among them,307pairs of SSR markers, whichaccounted for14.25%of the total, showed polymorphism. Each chromosome polymorphicmarkers distribution frequency is different, the lowest is32.08%on chromosome4and thehighest is68.75%on chromosome1. A total of180pairs of SSR primers evenlydistributed on all12chromosomes were selected from307pairs of polymorphic primers toanalyse genotypes of candidate strains. The location, order and distance of the180pairs ofSSR primers were determined according to a molecular marker linkage map constructed byMcCouch et al. The map covered the whole genome1427.7cM, average spacing7.93cM.（2） Using the indica variety Changhui121and the japonica variety Koshihikari asreciprocal receptor and donor, and making use of marker-assisted selection by180SSRmarkers, two sets of CSSL populations from BC₃F₂and BC₄F₁population wereconstructed. The CSSL population of Changhui121genetic background contained95linesand the CSSL population of Koshihikari genetic background contained86lines.（3） The genetic composition of two sets of chromosome segment substitution lineswas analysed by GGT2.0. The result showed that, in the CSSL population of Changhui121genetic background, the average percent of substitution markers in the95lines was7.61%,the total length of replacement fragment was2123.64cM, which was nearly40%more thanthe length of rice whole genome, and the average fragment length was23.02cM. Theaverage lines of each chromosome was8, could well represent all the12chromosomes.This CSSL population could represent93.66%of Koshihikari genotype. In the CSSLpopulation of Koshihikari genetic background, the average percent of substitution markersin the86lines was12.35%, the total length of the replacement segment2102.16cM, whichwas nearly38%more than the length of rice whole genome, and the average fragmentlength was24.85cM. The average lines of each chromosome was also8, and could alsowell represent all the12chromosomes. This CSSL population could represent93.66%Changhui121genotype.