Developing KDML105 Backcross Introgression Lines Using Marker-Assisted Selection for QTLs Associated with Drought Tolerance in Rice

Marker-assisted selection (MAS) has been employed to improve the efficiency and speed up breeding programs, specifically in selection. A major use of MAS is in assisting backcrossing of genes/QTLs to elite cultivars. Markers aid in the selection of target alleles and in the assessment of a recipient's parent genome. Introgression and selection of QTLs using molecular markers in foreground selection may have additional problems, since the exact position of the target is often not known. In such cases, QTL detection must be estimated with the expectation that its most likely position is within a confidence interval limit. The backcrossing process with target selection resulted in 103 KMDL105 introgression lines carrying 1, 2 or 3 target combinations, where 79, 20 and 4 lines were derived from KDML105 x IR68586-F 2 -CA-143 (DH212) (cross 1), KDML105 x IR68586-F 2 -CA-31 (DH103) (cross 2) and KDML105 x IR68586-F 2 -CA-54 (DH126) (cross 3) crosses, respectively. Genome scanning revealed that carrier chromosomes in all crosses showed a low percentage of the recipient parent genome. Also, non-carrier chromosomes, especially in crosses 1 and 2, were found to carry segments of the donor, which was reflected in the low percentage of the recipient genome of KDML105 in all crosses. The results proved that MAS aids in the transfer of target segments and may improve the recovery of the recipient genome if background selection is employed. Abbreviations: MAS, marker-assisted selection; QTL, quantitative trait loci; KDML105, Khao Dawk Mali 105; DTS, drought tolerance segment