[Construction of chromosome segment substitution lines carrying overlapping chromosome segments of the whole wild rice genome and identification of quantitative trait loci for rice quality].

Rice is one of the major staple cereal grains. Most of the important traits of crops are complex traits controlled by quantitative trait loci (QTL). Detection and genetic identification of QTLs can provide insights into molecular and biological mechanisms of development and physiology. Chromosome segment substitution lines (CSSLs) have been proposed as a simple and powerful way to identify QTLs. The demand for rice grain quality becomes increasingly important. The primary components of rice grain quality include appearance, milling and physico-chemical, cooking and eating quality. Most of these traits are complex and controlled by QTLs, so genetic characterization of these traits is more difficult than that of traits each controlled by a singular gene such as Waxy, which controls glutinousness of rice grain. We constructed 133 chromosome segment substitution lines (CSSLs) from backcross progenies (BC3F2) derived from a cross between Teqing (an O. sativa L. ssp. indica variety) as the recurrent parent and wild rice (O. rufipogon Griff.) as the donor parent. In this process, we carried out marker-assisted selection (MAS) by using 118 CAPS or SSR markers covering the whole rice genome (Figs.1, 2). Because phenotypic values of quality trait were significantly different between cultivar Teqing and wild rice, the CSSLs were used to identify QTLs for rice quality traits. Three appearance quality traits (head rice percentage, HRP; percentage of chalky rice grains, PCRG; transparency, TP) and five physico-chemical properties (gelatinization temperature, GT; gel consistency, GC; amylose content, AC; protein content, PC; fat content, FC) were scored using 133 CSSLs which substituted segments covering the whole genome of wild rice. A total of 15 QTLs for five of the eight traits mentioned above (HRP, PCRG, TP, PC and FC) were identified on nine chromosomes, and several QTLs affecting different quality traits were mapped in the same regions (Fig.3, Table 1).