QTL Mapping for Paste Viscosity Characteristics Related to Eating Quality and QTL-NIL Development in Japonica Rice (Oryza sativa L.)

Eating and cooking qualities are the most important trait in japonica rice breeding program. In this study, we performed genetic analysis to identify quantitative trait loci (QTLs) related to eating quality using 182 recombinant inbred lines (RILs) derived from a cross between two japonica cultivars, ‘Ilpumbyeo’ and ‘Moroberekan’. Parameters for eating quality being investigated include alkali digestive value (ADV) and amylose content (AC) for physico-chemical properties, glossiness of cooked rice (GCR), and six paste viscosity properties, peak viscosity (PV), hot-paste viscosity (HPV), cool-paste viscosity (CPV), breakdown (BD), setback (SB), and consistency viscosity (CSV) in RILs. This study revealed 28 QTLs on chromosomes 1, 3, 4, 5, 6, 7, 8, 9, and 10. Two QTL regions on chromosomes 3 and 6 were clustered with QTLs for physico-chemical property, GCR, and paste viscosity. The QTL loci for ADV, AC, GCR, PV, HPV, CPV, BD, SB, and CSV of paste viscosity properties in wx locus on chromosome 6 are the most important region for improving the texture of cooked rice. Three QTLs for PV, BD, and SB were detected on chromosome 9. PV and BD were highly positively correlated while SB showed high negative correlation with PV and BD. The QTLs for PV, BD, and SB are important to develop high eating quality rice lines of delayed retrogradation of cooked rice. Seven QTL-NILs substituted with Ilpumbyeo genetic background in most loci except for qLB4.2 for leaf blast resistance from Moroberekan allele, are expected to improve cooking and eating quality in japonica rice.