[QTLs mapping of leaf traits and root vitality in a recombinant inbred line population of rice]

By employing a recombinant inbred line (RIL) population of 247 lines derived from an inidca-indica cross Zhenshan 97B x Milyang 46, a linkage map consisting of 158 DNA markers was constructed and used for the determination of QTLs conditioning five leaf traits and root exudates. The leaf traits analyzed were leaf area, leaf length, leaf width, leaf perimeter and leaf length/width ratio measured on top first leaf, top second and top third leaves. The RIL population showed transgressive segregation on each trait, and highly significant or significant positive correlations were observed between all traits except between leaf length and width, and between leaf perimeter and length/width ratio. A total of 24 QTLs located in 9 intervals were detected to have significant additive effects for leaf traits analyzed, with LOD scores ranging 2.9-11.8 and 4.0%-32.5% phenotypic variation explained for a single QTL. Clustering of QTLs for leaf traits was evident. In interval RM197-RZ516 on chromosome 6, 2 QTLs for leaf length, 2 QTLs for leaf width and 3 QTLs for leaf length/width ratio of different leaves were detected, among which the alleles for increasing trait values were from Zhenshan 97B for leaf length and leaf length/width ratio, and from Milyang 46 for leaf width. In interval RM1-RG532 on chromosome 1,2 QTLs for leaf length and 2 QTLs for leaf perimeter were detected on top first leaf and top second leaf, respectively, and all the alleles for increasing trait values were from Milyang 46. In this interval, larger additive effects were observed for QTLs detected on top first leaf than at top second leaf. In interval RZ667-B10B on chromosome 6, a QTL for leaf perimeter of top second leaf was detected, accounting for 8.0% phenotypic variation. In intervals RZ66-RM264 and RG81-RM313 on chromosome 8 and 12, each QTL was detected for leaf length of top third leaf and explained for 9.0% and 15.3% phenotypic variation, respectively. Epistasis analysis detected 56 and 4 significant additive-by-additive interactions for leaf traits and root vitality, explaining 2.7% to 13.7% and 6.8% to 14.9% of the total phenotypic variation, respectively. On comparison with QTLs for yield traits detected in the same population previously, it was found that the majority of QTLs for leaf traits and root vitality and those for yield traits were located in similar intervals. Fine mapping of QTLs for both leaf and yield traits in these chromosomal regions would facilitate investigations of the source-sink relationship in rice.