QTL analysis for phytonutrient compounds and the antioxidant molecule in mustard (Brassica juncea L.)

A recombinant inbred line (RIL) population was developed following hybridization between a low glucosinolate B. juncea genotype, NUDH-YJ-04 and a high glucosinolate cultivar, RL-1359. RILs differed for seed and leaf glucosinolates, total tocopherols and oil content. A linkage map of length covering 2346.9 cM was constructed. It comprised 198 markers distributed across the 18 linkage groups. The linkage map facilitated analysis of quantitative trait loci (QTL) associated with phytonutrient compounds and the antioxidant molecules. The composite interval mapping helped to identify 21 QTLs on 11 linkage groups with R-2 values between 15-53 % at logarithmic of odd (LOD) scores of 3.1-8.6. For seed aliphatic glucosinolates, most significant QTL, explaining 53 % of the phenotypic variation was located on J9, for glucoiberin (IBE-S). QTLs were also identified for indole glucosinolate (NEO-S) (44 %) on J7 and aromatic glucosinolate (NAS-S) (38 %) on J4. Total leaf glucosinolates (TGLC-L) explaining 15-21 % phenotypic variance were mapped to three different genetic intervals on J6 and J14, and total seed glucosinolates (TGLC-S) explained 17 % of the variance on J18. Tocopherol (TOC) QTL was confined to chromosome no. J6 (28 %) and J12 (19 %) at LOD score of 4.8 and 3.1. QTL for Oil content was tagged on J9 at LOD score of 3.2. Candidate genes underlying SIN-S, NEO-S and NAS-S QTLs, were considered to be GSL-elong, MYB-76 and MYB-28 in A4, A7 and A10 respectively. Despite a lower coverage, this is a first linkage map in this crop based solely on SSR markers and can serve as a basic map.