Mapping of QTLs for kernel oil, starch and embryo size in corn using Korean high oil germplasm

Korean High Oil (KHO) is a previously uncharacterized corn germplasm with unusually high levels of oil in the kernel. The authors used QTL mapping to identify genomic regions associated with the high oil trait, as well as starch concentration and embryo size, using 190 F2:3 lines derived from multiple crosses of maize inbred lined A619 and KHO. A composite linkage map of 111 molecular markers were constructed after genotyping F2 individuals with single nucleotide polymorphism (SNP), simple sequence repeat (SSR) and insertion-deletion (IDP) markers. Near-infrared spectroscopy (NIR) was used to measure the oil and starch concentrations of the F2:3 seeds while Image J analyzer was used to measure the two-dimensional size of the embryo. Seven, three and six QTLs were mapped respectively for oil, starch and embryo size. A major QTL (oil6) with a high LOD score of 8.33 and explains 26.62% of the variation for oil was mapped in chromosome 6. A major QTL for starch in chromosome 9 (sta9) with an R square value of 25.22% was also mapped. On the other hand, all of the mapped embryo size QTLs had small phenotypic effects (R square 8%). The oil concentration QTLs that were mapped in this study were compared to previous investigations using different germplasm and were found to be located in the same or very near chromosomal regions. All of the co-located QTLs were consistent with their correlation and sign of additive effects as predicted by their parental difference. Recently, it was shown that an allele of diacylglycerol acyltransferase gene (DGAT) with an extra phenylalanine at amino acid position 469 (F469) is present in high oil germplasm. By sequencing the F469 region using primers designed from the previously cloned high oil DGAT allele, the authors found that F649 also was present in KHO. The existence of F469 in a teosinte accession in this study in a previous study has implications for the use of wild relatives of corn as a source of novel alleles or genes important for contemporary corn improvement.