Analysis of genetic factors that control shoot mineral concentrations in rapeseed (Brassica napus) in different boron environments

Mineral nutrients are essential for plant cell function, and understanding the genetic and physiological basis of mineral concentration is therefore important for the development of nutrient-efficient crop varieties that can cope with a shortage of mineral resources. In the present study, we investigated the profiles of B, Ca, Fe, Cu, Mg, P and Zn concentrations in shoots and analyzed the genetic variation in a rapeseed (Brassica napus) double haploid population at normal and deficient boron (B) levels in hydroponic conditions. Significant correlations between the concentrations of different minerals, such as Ca and Mg, Ca and P, and Cu and Fe, existed in both B environments. A total of 35 quantitative trait loci (QTL) and 74 epistatic interaction pairs for mineral concentrations were identified by whole genome analysis of QTL and epistatic interactions. The individual phenotypic contributions of the QTL ranged from 4.4% to 19.0%, and the total percentage of genetic variance that was due to QTL and epistatic interactions varied from 10.4% to 82.4%. Most of these QTL corresponded specifically to one of the two B conditions except for one stable main-effect P-QTL across the B environments. Three QTL for Ca and Mg were found to co-localize under normal B condition. These results revealed that genetic factors control mineral homeostasis in plants and multigenes involving ion transport are required to regulate mineral balance in plants under conditions of diverse nutrient stress. In addition, 26 genes involved in ion uptake and transport in Arabidopsis thaliana were in silico mapped onto the QTL intervals of B. napus by comparative genomic analysis. These candidate orthologous genes in B. napus allowed the selection of genes involved in the controlling mineral concentration that may account for the identified QTL.