PARENT SESSION
Oral Session 61: Populations and Genetics I.
Presiding: J Lau
Wednesday, August 4, 8:00 AM to 11:30 AM, Meeting Room B 116.

Genetic variation in seed germination and dormancy among crop-wild hybrids in sunflower (Helianthus annuus).

Mercer, Kristin^*,1, Shaw, Ruth¹, Wyse, Donald¹, ¹ University of Minnesota, St. Paul, MN, USA

ABSTRACT- The movement of genes among populations is one mechanism by which the genetic variation within plant populations can increase, influencing their evolutionary potential. Such gene flow from cultivated to wild plants can act as a source of unique traits or alleles for wild populations. Selection on seed dormancy and germination behavior differs for crop and wild plants, with crops bred for quick and uniform germination under favorable conditions, while natural selection in the wild often promotes winter-hardiness, dormancy and prolonged germination. As the first growth stage in the generation following a hybridization event, germination serves as a critical gateway for the entry of crop alleles into the population; increased germination in hybrids could in turn influence the introgression of crop alleles and the evolution of wild populations. However, across wild populations there exists much diversity. The impact of crop traits on a wild population would necessarily depend on the existing germination traits and their underlying genetics. We conducted lab and field experiments to understand how crop-wild sunflower hybrid seeds differ from their wild counterparts in germination behavior, and the extent to which the results are genetically contingent. Using seed produced from hand-pollinations between nine wild maternal populations and either wild or one of three crop paternal parents we found greater overall germination in the hybrid as compared to the wild seed across maternal populations. However, populations differed in the magnitude of distinction between wild and hybrid germination. Additionally, hybrids possess dormancy and germination traits that are intermediate between wild and crop seeds. Such variation in ecologically important traits across genetic backgrounds reveals potential for differences in population dynamics and rate of crop gene introgression following a hybridization event.

Key words: genetic variation, seed germination, sunflower crop-wild hybrids, gene flow