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

Graduation date: 2008Elite inbred sunflower (Helianthus annuus L.) lines were found to have short-lived\ud embryo and seed covering dormancies. Seed dormancy of wild sunflowers (H. annuus,\ud H. argophyllus and H. exilis) was found to be controlled primarily by the seed covering\ud (seed coat and pericarp) and embryo dormancy was short-lived (four to eight weeks).\ud Native American Landraces (NALs) had low to moderate embryo and seed covering\ud dormancy, which was more similar to elite lines. The seed covering in the NALs\ud contributed more to seed dormancy than did the seed covering in the elite lines. The seed\ud coat itself was implicated in seed dormancy and the length of dormancy caused by the\ud seed coat varied by accession and variety. Excising ¼ of the seed, rather than removing\ud the entire seed covering, increased germination but also increased the number of seed that\ud decayed. Dormancy of embryos from 19 wild sunflower accessions ranging in south to\ud north latitude from Texas to Saskatchewan, Canada was found to be highly variable;\ud however seed covering dormancy was similar among all the wild accessions in the\ud northern latitudes. Germination of accessions in the most southern latitudes was greater\ud (P