QTL detection for eating quality including glossiness, stickiness, taste and hardness of cooked rice

To identify the chromosomal regions controlling the eating quality of cooked rice, we performed a quantitative trait locus (QTL) analysis using 93 backcross inbred lines (BILs) and 39 chromosome segment substitution lines (CSSLs) derived from crosses between a japonica rice cultivar Koshihikari (glossier appearance, tasty, sticky and soft eating quality of rice when cooked) and an indica cultivar Kasalath (less glossy appearance, less sticky and hard eating quality of rice when cooked). We evaluated the eating quality of rice including overall evaluation (OE), glossiness (GL), taste (TA), stickiness (ST) and hardness (HA) in each line based on the sensory test of cooked rice. Twenty-one QTLs for eating quality were mapped to eight regions on chromosomes 1, 2, 3 (two regions), 6, 7, 9 and 10. The Koshihikari alleles at 19 out of 21 QTLs increased the eating quality, while the Kasalath alleles at the other two QTLs increased the eating quality. We also mapped the QTLs for chemical properties, such as amylose content (AC) and protein content (PC), which affected the eating quality. Four QTLs in the terminal region of the short arm of chromosome 3 and five QTLs on chromosome 6 for eating quality were mapped to the same region as that of the QTLs for AC. Three QTLs on chromosome I for eating quality were also mapped to the same region as that of a QTL for PC. The chromosome positions of the other QTLs for eating quality did not coincide with those of the QTLs for AC and PC. Six out of 21 QTLs for eating quality, qTA3, qOE6, qGL6, qTA6, qST6 and qHA6, were commonly identified by analysis using both BILs and CSSLs. One QTL, qTA3, was not a locus of AC, PC or known eating genes. Thus the QTL was mapped in the interval between the SSR markers RM1332 and RM6676 in the middle region of the short arm of chromosome 3 by fine mapping of three sub-CSSLs. Five QTLs, qOE6, qGL6, qTA6, qST6 and qHA6, seemed to be associated with the Waxy (Wx) gene located on chromosome 6.