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Brian W. Trader*, Hope A. Gruszewski, Norman I. Barclift, Richard E. Veilleux, and Holly L. Scoggins

Coreopsis grandiflora (tickseed) regenerates readily from leaf segments allowing the possibility to exploit somaclonal variation as a means to develop novel phenotypes. We used true leaves from in vitro seedlings of Coreopsis grandiflora `Domino' grown on MS basal medium as explants in a series of experiments to evaluate the effect of media, leaf explant orientation, and genotype on shoot regeneration. Genotype accounted for most of the variation with two particular seedlings regenerating freely and eight others generally recalcitrant. From these two seedlings, designated E2 and H2, shoots were regenerated and acclimated to the greenhouse over a period of weeks. Once the plants had established (≈6 weeks after acclimatization) they were vernalized by moving them to a lighted bench (12-h photoperiod) in a walk-in cooler at 4 °C .On transfer back into the greenhouse, the plants flowered within a few weeks; 15 of 175 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 May 2002 in a randomized complete-block design with three-plant plots and three replications, to determine if the novel characteristics persisted through an additional propagation cycle. In the field, plant height, leaf dimension, flowering, and flower dimensions were scored in June-July 2003. Significant differences were found between somaclones and the original E2 and H2 similarly propagated seedlings for desirable (more petals per flower, greater flowering, shorter plants), undesirable (less flowering, smaller flowers), and neutral (narrower leaves, taller plants) traits.

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Brian W. Trader, Hope A. Gruszewski, Holly L. Scoggins, and Richard E. Veilleux

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.