Identification of quantitative trait loci underlying the protein, oil and starch contents of maize in multiple environments

A dissection of the genetic regulation of protein, oil and starch contents in maize (Zea mays L.) kernels will enhance high-quality breeding. The objective of the present research was to detect the quantitative trait loci (QTL) controlling protein, oil, starch and lysine contents in maize kernels and to dissect their inheritable relationships and basis. A population of 498 recombinant inbred lines derived from a biparental cross of two elite inbred lines were grown in six environments. All individuals were genotyped with 151 pairs of simple sequence repeat markers to construct a genetic linkage map. Using composite interval mapping, we detected total 25, 13, 31 and 15 QTLs for protein, oil, starch and lysine contents, respectively, in six environments. 32 QTLs at bins 2.03-2.04, 2.05-2.07, 5.05-5.07, 6.01-6.04, 8.03-8.05 and 10.03-10.05 were stably expressed across multiple environments. Co-localizations of QTLs for the four traits were found on chromosomes 1, 2, 5, 6, 8, and 10. Part of the co-localized QTLs, the direction of QTL effects coincided with the sign of their phenotypic correlations, which likely indicates the presence of pleiotropic QTL or tight linkage among them. Additionally, seven pairs of QTLs with significant additive x additive epistatic interaction effects were identified based on single-environment QTL analysis. The results obtained from the present investigation may hold great promise for further studies of improving kernel quality in maize.