Construction of a new set of rice chromosome segment substitution lines and identification of grain weight and related traits QTLs

We report here the construction of a new set of chromosome segment substitution lines (CSSLs) in rice, in which the genome of the elite japonica cultivar C418 has been introgressed into the background of the elite indica cultivar 9311. This set was developed by marker aided selection, based on 136 SSR and in/del markers. The introgressed chromosomal segments presented in the 108 CSSLs covered 98.3% of the cultivar C418 genome. The CSSL set was used to genetically analyze variation for 1000-grain weight (TGW) and related traits in two contrasting environments, and led to the identification of 41 quantitative trait loci (QTLs), five of which were expressed in both environments. More detailed mapping of qTGW7 showed that it is cosegregated with RM22034 on the short arm of chromosome 7. The CSSLs varied phenotypically with respect to a number of agronomic traits besides TGW. CSSL populations would be effective in identifying QTLs for these various traits, and could provide germplasm relevant for crop improvement.