Chia, Salvia hispanica L., was well developed into a cultivated crop and an important component of Mesoamerican cultures and nutrition. Early Mesoamerican breeders produced lines with well developed agronomic characteristics including good, uniform seed yield and retention. Seed retention in particular is disadvantageous for survival in the wild. Maize, beans and squash were developed into important crops concomitant with chia in Mesoamerica but unlike these other crops lack of photoperiodic variability in floral induction limited the spread of chia cultivation into North America. There has been renewed interest in chia as an excellent source of x3 fatty acids and dietary fiber for healthy diets. Such highly unsaturated oils also are useful starting materials for many renewable chemicals. Further we find chia grows very well in Midwestern and Eastern USA but flowers too late in the season for seeds to mature before killing frosts. We set out to develop the genetic diversity in floral induction to provide germplasm for production in the US and other temperate areas of the world. We demonstrate that new early flowering lines are able to flower under a photoperiod of 15 h under greenhouse conditions. In field conditions, some selected new lines flowered at a photoperiod of 14 h and 41 min during the 2009 growing season in Kentucky and can produce seeds in a range of environments in temperate areas.
In Salvia hispanica L., several changes in qualitative characters, including seed coat color, stem pigmentation, and shattering, have evolved with cultivation and domestication. Three F(2) segregating generations from crosses between wild and domesticated parents were scored for three qualitative traits. A single recessive gene, designated scc, was found to govern the white seed characteristic. A single dominant gene, designated SSP, was found to control striated stem pigmentation. A complete dominance of open calyx over closed calyx was observed in F(1) generations and small numbers of plants with closed calyxes were observed in F(2) generations, not conforming to Mendelian ratios. For this non-shattering trait, a complementation test was conducted between two lines representative of geographically and morphologically divergent domesticated varieties. Complementary gene action was not observed in any F(1) plants, and all F(2) plants were homogeneous with respect to the trait, suggesting the same genetic control for non-shattering among domesticated varieties. An analysis of limited data for linkage of SSP and scc indicated that the two loci segregate independently.
Variation and heritability of seed mass in the Mesoamerican crop chia, Salvia hispanica L. was studied to examine the feasibility of selection for the trait. Genotypic variation in seed mass in wild/cultivated and domesticated accessions of chia from different origins was assessed. Broadsense heritability of seed mass was estimated using variances associated with parental and F 2 generations derived from two crosses and from the response to one cycle of selection. Significant (P 0.0001) genotypic variation was observed among accessions. Mean seed mass for domesticated accessions (14.84 mg/100 seeds) was greater than that of the wild accessions (11.29 mg/100 seeds) by 31%. The heritability of seed mass was relatively high in chia (0.75), suggesting that this trait is under strong genetic control. This conclusion was supported by a single selection cycle from the F 2 to F 3 generation that produced a 16% increase in mean seed mass. The realized heritability estimated based on this one cycle of selection also was 0.75. These observations indicate that gains from selection in chia seed mass are possible when mass selection is conducted in early generations. Basic information is thus provided for future breeding efforts in a species for which little or no knowledge of inheritance currently exists.
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