Evolutionary analyses aimed at detecting the molecular signature of selection during crop domestication and/or improvement can be used to identify genes or genomic regions of likely agronomic importance. Here, we describe the DNA sequence-based characterization of a pool of candidate genes for crop-related traits in sunflower. These genes, which were identified based on homology to genes of known effect in other study systems, were initially sequenced from a panel of improved lines. All genes that exhibited a paucity of sequence diversity, consistent with the possible effects of selection during the evolution of cultivated sunflower, were then sequenced from a panel of wild sunflower accessions an outgroup. These data enabled formal tests for the effects of selection in shaping sequence diversity at these loci. When selection was detected, we further sequenced these genes from a panel of primitive landraces, thereby allowing us to investigate the likely timing of selection (i.e., domestication vs. improvement). We ultimately identified seven genes that exhibited the signature of positive selection during either domestication or improvement. Genetic mapping of a subset of these genes revealed co-localization between candidates for genes involved in the determination of flowering time, seed germination, plant growth/development, and branching and QTL that were previously identified for these traits in cultivated × wild sunflower mapping populations.

Tocopherols are compounds present in oilseeds with major effect on nutritional and technological properties of seed oils. Brassica spp. mainly contain varying concentrations of a-tocopherol, with high vitamin E value, and c-tocopherol, which contributes to oil stability. The objective of this research was to select for contrasting tocopherol content and profile in Ethiopian mustard (Brassica carinata A. Braun). A collection of 211 F 4:5 lines was evaluated for tocopherol content and profile, and divergent selection was conducted till the S 3:4 generation. Selection resulted in two lines with increased tocopherol content (244 and 243 mg/ kg seed as average of four environments), one line with reduced tocopherol content (117 mg/kg), two lines with reduced a/c-tocopherol ratio (0.22 and 0.28) and two lines with increased a/c-tocopherol ratio (3.74 and 3.34). Control line C-101 averaged 196 mg/kg with a/c-tocopherol ratio of 1.10. Reduced a/c-tocopherol ratio was controlled by recessive alleles at a single locus. Seed to plant correlation was high (r = 0.92), which suggests the feasibility of selecting at the single-seed level.

Plastochromanol-8 and tocopherols are natural antioxidants with vitamin E activity that protect seeds and plants from oxidative damage. Whereas a-tocopherol is predominant in photosynthetic tissues, g-tocopherol is more abundant in seeds. Ethiopian mustard (Brassica carinata A. Braun) seeds contain varying levels of both tocopherol forms. The objective of this research was to study changes in plastochromanol-8 and tocopherol contents during seed germination in Ethiopian mustard lines with contrasting seed tocopherol levels, and to evaluate their influence on seed germination and seedling growth. Cotyledons and radicles of seven lines with contrasting seed tocopherol levels and a control line were sampled periodically until 120 h after sowing (HAS) under light and dark conditions, and were analysed for plastochromanol-8 and tocopherol contents. The main factors genotype, tissue, light and HAS were significant for all the traits, excepting the light effect for total tocopherol content. Most of the lines showed a gradual decrease in g-tocopherol that was nearly completely replaced by a-tocopherol at 120 HAS. However, line BCT-4, with high g-tocopherol content in seeds, exhibited unusually high g-tocopherol content in cotyledons and radicles during the whole sampling period. Light treatment and initial seed tocopherol levels had no influence on germination percentage. Despite significant differences for seedling development among genotypes, no clear association between seedling development and seed tocopherols was observed. The results revealed that the unusual presence of high g-tocopherol levels in cotyledons and radicles of line BCT-4 did not have an effect on seedling growth.

Ethiopian mustard (Brassica carinata A. Braun) line BCT-6, with reduced γ-tocopherol content in the seeds, has been previously developed. The objective of this research was to conduct a genetic analysis of seed tocopherols in this line. BCT-6 was crossed with the conventional line C-101 and the F1, F2, and BC plant generations were analyzed. Generation mean analysis using individual scaling tests indicated that reduced γ-tocopherol content fitted an additive-dominant genetic model with predominance of additive effects and absence of epistatic interactions. This was confirmed through a joint scaling test and additional testing of the goodness of fit of the model. Conversely, epistatic interactions were identified for total tocopherol content. Estimation of the minimum number of genes suggested that both γ- and total tocopherol content may be controlled by two genes. A positive correlation between total tocopherol content and the proportion of γ-tocopherol was identified in the F2 generation. Additional research on the feasibility of developing germplasm with high tocopherol content and reduced concentration of γ-tocopherol is required.