Cold tolerance and short day acclimation in perennial Gaura coccinea and G. drummondii

The use of related species to integrate important traits into cultivated crops is a common practice in plant breeding. Gaura coccinea and, potentially its derived species Gaura drummondii, could be donor species for introgressing cold tolerance into non-hardy G. lindheimeri. However, cold tolerance and acclimation has not been studied in these species, so protocols for determining these traits are required. The objectives of this study were to determine the relative cold tolerance of G. coccinea, G. drummondii and whether short day photoperiod is involved in cold acclimation. G. drummondii from Texas, USA and G. coccinea from Minnesota and Texas, USA were subjected to freezing tests using whole plant or electrolyte leakage after natural acclimation or non-acclimation conditions. Minnesota genotypes were able to withstand colder temperatures (-12 °C) than Texas genotypes (-9 °C). Acclimation capacity was determined for whole plant and electrolyte leakage assays using three different plant organs-stem, crown, and rhizome. Underground rhizomes were the best predictors of cold tolerance, however they were difficult to obtain. Stem sections of G. drummondii (Texas) and G. coccinea (Minnesota and Texas) were used to determine a shift in acclimation under short days. The Minnesota G. coccinea genotypes demonstrated greater cold tolerance after 3 weeks of short days while Texas G. coccinea, G. drummondii genotypes did not change even after 5 weeks.