QTL detection of rice grain quality traits by microsatellite markers using an indica rice (Oryza sativa L.) combination

Abstract

The gelatinization temperature (GT), gel consistency (GC) and amylose content (AC) are the three major rice traits that are directly related to cooking and eating quality (Little et al. 1958). GT is a physical trait responsible for cooking time and the capacity to absorb water during the processes cooking, and the temperature at which starch irreversibly loses its crystalline order during cooking. The GC is responsible for softness, and the AC is responsible for texture and appearance in rice. Hence, regulating AC in rice has been a major concern of rice breeders. To facilitate the development of new varieties with high cooking and eating qualities, it is necessary to understand the genetic bases of such traits. Lanceras et al. (2000) found four QTLs for AC on chromosomes three, four, six and seven. These QTLs accounted for 80% of phenotypic variation observeded in AC. Two QTLs on chromosome six, and one on chromosome seven were detected for GC, which accounted for 57% of phenotypic variation. Umemoto et al. (2002) confirmed this and demonstrated that the alk locus encodes the enzyme soluble starch synthase IIa. Bao et al. (2002) and Lanceras et al. (2000) found the effect of the wx region on GC. However, He et al. (1999) and Bao et al. (2002) showed that GC is controlled by two QTLs with minor effects. Zhou et al. (2003) improved the eating and cooking quality of Zhenshan 97 by introgressing the waxy gene region from Minghui 63 (wx-MH), a restorer line that had medium AC, soft GC and high GT. Li et al. (2004) identified four QTLs for AC, three for GT and five for GC using backcross-inbred lines. The four QTLs for AC were located on chromosomes three, four, five and six. The QTL on chromosome six covered the wx gene region and mainly contributed to the variance between