Seed dormancy in domesticated and wild sunflowers (Helianthus annuus L.) : types, longevity and QTL discovery Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/3484zk798

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  • Elite inbred sunflower (Helianthus annuus L.) lines were found to have short-lived embryo and seed covering dormancies. Seed dormancy of wild sunflowers (H. annuus, H. argophyllus and H. exilis) was found to be controlled primarily by the seed covering (seed coat and pericarp) and embryo dormancy was short-lived (four to eight weeks). Native American Landraces (NALs) had low to moderate embryo and seed covering dormancy, which was more similar to elite lines. The seed covering in the NALs contributed more to seed dormancy than did the seed covering in the elite lines. The seed coat itself was implicated in seed dormancy and the length of dormancy caused by the seed coat varied by accession and variety. Excising ¼ of the seed, rather than removing the entire seed covering, increased germination but also increased the number of seed that decayed. Dormancy of embryos from 19 wild sunflower accessions ranging in south to north latitude from Texas to Saskatchewan, Canada was found to be highly variable; however seed covering dormancy was similar among all the wild accessions in the northern latitudes. Germination of accessions in the most southern latitudes was greater (P<0.0001) than germination of accessions from more northern latitudes. The seed covering had to be completely removed in order to maximize germination of wild accessions from all latitudes. Seed germination of whole achenes of elite lines was greatest under alternating conditions of 12 hours of light and 12 hours of darkness. Recombinant inbred lines (RILs) of an elite by wild cross (HA89 x ANN1238) were evaluated for seed dormancy quantitative trait loci (QTL). QTL were mapped to 14 of the 17 linkage groups, for the time course of 0 to 24 weeks of seed after-ripening. Twenty four QTL related to whole seed dormancy were found. Whole seed dormancy QTL explained between 9-30% of the phenotypic variation observed. Seven QTL were found related to embryo dormancy. QTL related to embryo dormancy explained from 12-23% of the phenotypic variation observed. Delay of germination percentage (DOGp) of each RIL was calculated using the Richards function (1959) to detect QTL related to 25, 50 and 75% germination. Twelve DOGp QTL were detected to help further explain seed dormancy QTL. Four strong regions harboring several QTL each were identified which sets the stage for more in depth future analyses.
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