Identification of QTLs across Recombinant Inbred Lines and Testcross Populations for Traits of Agronomic Importance in Rice

This study was conducted to determine whether quantitative trait loci (QTLs) controlling traits of agronomic importance detected in recombinant inbred lines (RILs) are also expressed in testcross (TC) hybrids of rice. A genetic map was constructed using an RIL population derived from a cross between B5 and Minghui 63, a parent of the most widely grown hybrid rice cultivar in China. Four TC hybrid populations were produced by crossing the RILs with three maintaining lines for the widely used cytoplasmic male-sterile (CMS) lines and a genic male-sterile line Peiai64s. The mean values of the RILs for the seven traits investigated were significantly correlated to those of the F1 hybrids in the four TC populations. Sixty-seven main-effect QTLs were identified. Of these, the QTL that had the strongest effect on each of the seven traits in the RILs was detected in two, three or four of the TC populations, and eight others were detected in one TC population. Epistatic analysis revealed that the effect of epistatic QTLs was relatively weak and combination-specific. Searching publicly available QTL data in rice revealed positional convergence of the QTLs with the strongest effect in a wide range of populations and under different environments. Since the main-effect QTL is expressed across different testers, and in different genetic backgrounds and environments, it is a valuable target for gene manipulation and for further application in rice breeding. When a restorer line that expresses main-effect QTLs is bred, it could be used in a number of cross combinations.

Key Words: Hybrid, Molecular marker, Quantitative trait locus, Recombinant inbred line, Testcross

Online ISS 1091-6490
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