Detection And Analysis Of QTL For Cooked Rice Elongation In Rice (Oryza Sativa L.)

Cooked rice elongation is very important in determining the cooking and eatingquality of rice. In this study, a recombinant inbred lines (RIL) population derived froma rice cross between indica cultivar 'IR24' and japonica cultivar 'Asominori', agenome-wide chromosome segment substitution lines (CSSL) population fromContinuously backcrossing of F₇ lines of 'Asominori×IR24' With Asominori and asecondary F₂ populations(derived from the cross between target CSSL and geneticbackground parent, Asominori) were used to investigate the QTL of Cooked riceelongation related traits. The objective of this study was to reveal the genetic basis ofcooked rice elongation, with a view using this to improve the quality of rice in future.The main results were as follows:1 QTL mapping for cooked rice elongation related traits using RIL and CSSLpopulationsRIL and CSSL populations were used to investigate the QTL of 9 cooked riceelongation related traits including milled rice length(MRL), milled rice width(MRW),milled rice shape(MRS), cooked rice length(CRL), cooked rice width(CRW), cookedrice shape(CRS), elongation ratio(ER), width expansion ratio(WE) and elongationindex(EI). All investigated traits showed extensive variations in the both populations,and apparent transgressive segregations were observed. Significant correlationsamong the 9 traits were observed in the both populations and the correlationcoefficients between the traits are identical in the two populations. A total of 26 QTLhad been identified using RIL population. Forty-two marker-linked loci had beenidentified across four environments using CSSL population, and eleven of them wereconsistently detected in the four different environments. The main molecular markerintervals on Chr.2, Chr.3 and Chr.5 had been identified, each of them harbored thesame or related QTL in the both populations. QTL for related traits were frequentlymapped in the same genome regions. Four QTL, qMRL-2, qCRS-2, qER-2 and qEI-2,were simultaneously located in the vicinity of RFLP marker C601 on chromosome 2 across 4, 2, 4 and 3 environments, respectively, using CSSL population. These QTLcontrolled MRL, CRS, ER and EI, respectively, with average PVEs of 10.31%,18.73%,18.04% and 14.98%. Four QTL controlled CRL, CRS, ER and EI,respectively, had been identified in the same region using RIL population, withaverage PVEs of 25.37%,20.64%,36.09% and 17.63%. Therefore, the QTL clusterhad higher stability and larger PVE, and would be useful for further marker-assistedselection (MAS) in rice quality improvement.2 QTL mapping for cooked rice elongation index fEI) using F₂ populationsUsing secondary F2 populations, derived from the cross of CSSL13 andAsominori, two QTL for EI were detected in the RM263-RM526 andRM526-RM1385 interval, respectively, with LOD value and PVEs of 2.83, 2.73 and12.46%, 12.49%. We should enlarge the population to find out whether the two QTLlinked tightly are the same one. In addition, the two QTL for EI are located near theQTL for water absorption of cooked rice grains, which confirms the significantcorrelation between EI and water absorption of cooked rice grains.