Quantitative trait loci for cold tolerance in the maize IBM population

B73 and Mo17 represent the main families of elite maize (Zea mays L.) inbred lines. B73 and Mo17 significantly differed in their proportion of germination under low-temperature conditions, and the IBM population derived from the cross B73 x Mo17 provides breeders a great opportunity for locating quantitative trait loci (QTLs) for cold tolerance in elite maize germplasm, the objective of this study. Under low-temperature conditions, the recombinant inbred lines significantly differed for all traits except vigor. No QTLs were detected at optimal conditions, but two QTLs involved in leaf color at low temperature were located in the short arm of chromosome 3 and the long arm of chromosome 6. The final fit for QTLs detected in our study explained 14.2% of phenotypic variance and 28.2% of genetic variance. However, in cross-validation analysis, QTLs detected in chromosomes 3 and 6 were detected in only 12.3% and 25.7% of all cross-validation runs, respectively, and explained 3.7% of the genetic variance. Although Mo17 could bring some favorable alleles, marker-assisted selection is not advisable because differences between allelic variants are small and explain a low proportion of genotypic variance. The locus luteus11 is proposed as a candidate gene for the QTL located in chromosome 6, while the QTL located in chromosome 3 probably corresponds to an unknown gene.We thank the Maize Genetic Cooperation Stock Center for germplasm and the Maize Genetics and Genomics Database for genotyping data. Research was supported by the National Plan for Research and Development AGL2004-06776), the Autonomous Government of Galicia (PGIDIT04RAG403006PR), and the Excelentísima Diputación Provincial de Pontevedra. V. M. Rodríguez acknowledges his fellowship from the Ministry of Science and Technology from Spain.MCYTDiputación de PontevedraPeer reviewe