Developing cold tolerant Gaura lindheimeri: Identifying and characterizing Gaura coccinea and chromosome doubled Gaura lindheimeri

Gaura lindheimeri, native to Southern Texas and Louisiana (USDA hardiness zone 7/8), is not winter hardy in Minnesota (Z3/4), although it is sold as an herbaceous ornamental perennial. One objective of the University of Minnesota flower breeding program is to create winter hardy Gaura . A related perennial, G. coccinea (USDA Z2-10), was identified as a winter hardiness source. Gaura coccinea ranges in ploidy from diploid (2n=2x=14) to octoploid (2n=8x=56). Gaura drummondii is often misidentified as G. coccinea; requiring taxonomic clarification. Three primary research objectives were to: (1) distinguish Gaura coccinea and G. drummondii using morphological/molecular markers, (2) determine cold tolerance and short-day response to cold acclimation, and (3) develop chromosome doubling protocols and examine stability of tissue cultured diploid Gaura lindheimeri .; Cytological analysis of G. coccinea demonstrated most populations collected were tetraploid, with one hexaploid genotype from Texas (1000-1). Dendrograms derived from morphological data distinguished G. drummondii, G. coccinea, and genotype 393-1. Primary differences were found between sepal, fruit, and stipe lengths, and leaf width, which were smaller in G. coccinea. One Randomly Amplified Polymorphic DNA (RAPD) marker was unique to all G. drummondii. Dendrograms split the two species, but not genotype 393-1 out. Both G. coccinea and G. drummondii were able to acclimate, with Minnesota G. coccinea being more cold tolerant (-12°C) than G. drummondii and Texas G. coccinea (-9°C). Underground rhizomes were the best predictor of cold tolerance compared to stem and crown tissue. Only Minnesota G. coccinea exhibited acclimation after three weeks of short (8-hr) days.; Two anti-mitotic agents at three concentrations (trifluralin---0, 15, 30 muM; colchicine---0, 0.25, 1.25 mM) and three durations (12, 24, 48 hrs) were tested for in vitro chromosome doubling in G. lindheimeri. Regardless of duration, 1.25 mM colchicine produced ∼20% autotetraploids. Pollen conformation changes were indicative of chromosome doubling. High levels of variability for floral traits were observed with in situ plants. Two experiments demonstrated variation was induced by tissue culture, unstable, and epigenetic in nature. Most pink-flowered plants reverted back to the coloration and patterning of the original genotype.