Quantitative trait locus mapping for carbon isotope ratio and root pulling force in canola

Carbon isotope ratio (delta C-13) and root pulling force (RPF) are associated with dehydration avoidance in plants. The delta C-13 measures the efficiency of C gain relative to water loss, whereas RPF, the vertical force required to pull plants from the ground, indirectly estimates root-related dehydration avoidance capacity. To determine quantitative trait loci (QTL) controlling these traits in canola (Brassica napus L.), a mapping population was evaluated in 2011 and 2012 in Fort Collins, CO. The split-plot experiment had two moisture regimes (main plot) and 148 doubled haploid lines (subplot), replicated three times. Analysis of variance indicated highly significant (P < .01) variation among genotypes for delta C-13, RPF, days to flowering, and several other agronomic traits. In 2011, delta C-13 was correlated (P < .01) with days to flowering in both moisture treatments (r = .41 dry, 0.31 wet) and with fresh biomass in the dry treatment (r = .64). The RPF was consistently correlated with plant height (r = .32-.54, P < .01) and fresh biomass (r = .17-.58, P < .05) in all environments. In 2011, QTL were detected on chromosomes A09 and C08 for delta C-13 and on chromosomes A05, C01, C04, and C08 for RPF. The QTL for delta C-13, RPF, and plant height co-localized on C08. In 2012, QTL were detected on A02 for delta C-13 and on C01 and C08 for RPF. Moderate heritability and low QTL x environment interaction for delta C-13 and RPF suggest that if validated, markers for these traits could be used in marker-assisted selection.