| Quality improvement of rice grains has become one of the most important goals in rice breeding. The major problems for rice grain quality are the bad appearance and eating quality in China, i.e., the high percentage of chalky grain and bad palatability of cooked rice. In this study, a chromosome segment substitution lines (CSSLs) population, derived from Asominori (japonica)/ IR24 (indicd) with Asominori as the recurrent parent, was planted and phenotyped for nine rice-eating-quality traits in three successive years. Thereby, quantitative trait loci (QTLs) for these cooking and eating quality traits were determined, meanwhile expression stability of the QTLs was investigated across the three years. On the other hand, 18 rice cultivars were selected and planted by four production ways in two years and three sites, of which 20 eating and appearance quality traits were observed and analyzed to evaluate the stability of the cultivars and traits with additive main effects and multiplicative interaction (AMMI) model. The main results are as follows:1. A total of 32 QTLs for nine cooking and eating quality traits were identified in the three years, and the phenotypic values were different significantly (p<0.001) between the CSSLs harboring any of the QTLs and Asominori. Among them, six QTLs on chromosomes 6 and 8, namely qLT-8 for luster (LT), qTD-6 and qTD-8 for tenderness (TD), qIVOE-6a and qIVOE-8 for IVOE, and qAC-8 for amylose content (AC), were detected consistently across the three successive years, indicating that genes of the QTLs could function stably across different years. The markers flanking the QTLs would be very useful not only for applying marker-assisted selection (MAS) to rice breeding for quality improvement, but also for fine mapping and map-based cloning of these genes.2. Stability for the eighteen tested cultivars was analyzed based on the phenotypic values of twenty quality traits in two years and three sites with the AMMI model. Three appearance quality traits, namely, grain length (GL), grain width (GW) and length-width ratio (LWR), showed good stability in six different environments; while six quality traits low, including ratio of grains with chalkiness (RC), size of chalkinessper grain (SC), peak viscosity (PKV), cool paste viscosity (CPV), setback viscosity (SBV) and integrated value of organoleptic evaluation (IVOE) of cooked rice. Moreover, the other eleven quality traits showed medium stability. On the other hand, five cultivars, Nanjing 16, W002, Shanyou 63, 3004 and Fengyouxiangzhan, were characterized by high stability, while four low, i.e., Changyou 1, Huaiyin 9901, Yangliangyou 6 and Teyou 559. These results would be very useful to improve rice quality and production stability.3. Negative correlation were detected among IVOE and eight quality characters, namely, GL, LWR, AC, CPV, SBV, consistency viscosity (CSV), gelatinization temperature (GT) and protein content (PC); while positive among the IVOE and GW, LT, TD, viscosity (VC), elasticity (EL) and breakdown viscosity (BDV), respectively. It is noteworthy that the correlation coefficient between AC and IVOE was lower than that between IVOE and other physical-chemical properties such as BDV, SBV, GT, PC, etc. Therefore, it would be more practical to apply these physical-chemical properties related to eating quality rather than AC for improving the palatability of cooked rice.4. The four cultivations for rice could affect all the twenty quality traits significantly except GL, GW and LWR. In term of the palatability of cooked rice, the green food cultivation produced the best rice quality, however, the high production cultivation could produce the rice grains with lower RC and SC. Therefore it might be a good strategy that the rice cultivars of lower RC and higher stability could be planted by green food cultivation to produce the good-quality and safe rice grains.
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