QTL mapping and analysis of the embryo and maternal plant for three limiting amino acids in rapeseed meal

Rapeseed meal is a rich vegetable protein source because of its balanced amino acid content. Lysine, threonine and methionine are three limiting essential amino acids for livestock and poultry on whose inheritance there is little information available especially at molecular level across different environments. In present study, quantitative trait locus (QTL) identification and analysis for these three important amino acids in rapeseed meal were conducted using two backcross populations derived from 202 double haploid lines of an elite hybrid cross “Tapidor × Ningyou7 (TN)” and their parents. A newly developed QTL model and related mapping software were used to analyze the genetic main effects and QTL × environment (QE) interaction effects for QTLs located in the embryo and maternal genomes, respectively. The results revealed 17 QTLs associated with lysine, threonine and methionine contents in rapeseed meal, 10 of which were in the A sub-genome and the rest in C sub-genome of Brassica napus L., showing significant embryo and maternal genetic effects. Among these QTLs, two were also found to have significant QE interaction effects. In addition, some QTLs were located at the same position or linkage group, such as three QTLs (qLysC-4-2, qThrC-4-2 and qMetC-4-2) in A4 linkage group and two (qThrC-7-3 and qMetC-7-3) in A7 linkage group were co-localized, and three (qLysC-1-1, qThrC-1-1 and qMetC-1-1) were distributed in the same A1 linkage group. qLysC-1-1, qThrC-12-5 and qMetC-7-3 were the major QTLs, which could explain 25.4, 36.7 and 16.4 % of their phenotypic variations, respectively. The genetic main effects and the QE interaction effects of QTLs from embryo and maternal genomes were important for these limiting essential amino acids. The results above might be helpful for marker-assisted selection in rapeseed breeding and cloning of functional genes relevant to lysine, threonine and methionine contents.