Somaclonal Variation of Coreopsis Regenerated from Leaf Explants

Abstract

Coreopsis species (tickseed) can be regenerated from leaf segments allowing the possibility to exploit somaclonal variation as a means to develop novel phenotypes. We used true leaf explants from in vitro seedlings of perennial C. grandiflora (A. Gray) Sherff `Domino' and `Sunray' grown on Murashige and Skoog (MS) basal medium. Two of ten seedlings of `Domino' regenerated freely and others were generally recalcitrant. From these two seedlings, designated E2 and H2, shoots were regenerated and acclimatized to the greenhouse. About 175 plants were established and vernalized from which somaclones were selected based on distinct differences in flower orientation and appearance. The selected somaclones were propagated by division and transplanted to the field in August 2001 in a randomized complete block design with three-plant plots and three replications to determine whether novel characteristics persisted through an additional propagation cycle. In the field, plant height, leaf dimension, flowering, and flower dimensions were scored in June and July 2003. Differences were found between somaclones and similarly propagated E2 and H2 for desirable (more petals per flower, greater flowering, shorter plants), undesirable (less flowering, smaller flowers), and neutral (narrower leaves, taller plants) traits. Open-pollinated (OP) seed was collected and germinated and the seedlings from somaclones that differed significantly from E2 and H2 were evaluated. These maternally selected seedlings were overwintered then planted in the field in May 2004. Most traits that differentiated somaclones from E2 and H2 did not persist in the OP seedling population; however variation that was likely introduced through outcrossing resulted in desirable phenotypes with potential for new cultivar development.