Abstract
BackgroundReproductive output is critical to both agronomists seeking to increase seed yield and to evolutionary biologists interested in understanding natural selection. We examine the genetic architecture of diverse reproductive fitness traits in recombinant inbred lines (RILs) developed from a crop (seed oil) × wild-like (rapid cycling) genotype of Brassica rapa in field and greenhouse environments.ResultsSeveral fitness traits showed strong correlations and QTL-colocalization across environments (days to bolting, fruit length and seed color). Total fruit number was uncorrelated across environments and most QTL affecting this trait were correspondingly environment-specific. Most fitness components were positively correlated, consistent with life-history theory that genotypic variation in resource acquisition masks tradeoffs. Finally, we detected evidence of transgenerational pleiotropy, that is, maternal days to bolting was negatively correlated with days to offspring germination. A QTL for this transgenerational correlation was mapped to a genomic region harboring one copy of FLOWERING LOCUS C, a genetic locus known to affect both days to flowering as well as germination phenotypes.ConclusionsThis study characterizes the genetic structure of important fitness/yield traits within and between generations in B. rapa. Several identified QTL are suitable candidates for fine-mapping for the improvement of yield in crop Brassicas. Specifically, brFLC1, warrants further investigation as a potential regulator of phenology between generations.
Highlights
Reproductive output is critical to both agronomists seeking to increase seed yield and to evolutionary biologists interested in understanding natural selection
We examine the quantitative-genetic structure and quantitative trait loci (QTL) architecture of bolting time and reproductive fitness characters in recombinant inbred lines of Brassica rapa developed from a cross between a seed oil cultivar and wild-like genotype
These results suggest that the QTL architecture for the majority of fitness traits examined in this study was at least partially conserved between the greenhouse and field
Summary
Reproductive output is critical to both agronomists seeking to increase seed yield and to evolutionary biologists interested in understanding natural selection. A QTL mapping study in Arabidopsis thaliana suggested that antagonistic pleiotropy of a gene region controlling both seed mass and ovule number may lead to the tradeoffs between these traits that have been observed in numerous cultivated and natural species [7]. If this region represents structured pleiotropy, in that allelic substitutions at one locus affect both traits, they will be resistant to change even under strong selection [15,16]. It may be prudent to search for natural populations in which these associations are weaker or focus selection efforts on loci that are not pleiotropically regulated
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