Winter Survival and Flowering Performance of In Vitro Propagated Dianthus Giganteiformis Subsp. Pontederae (A. Kern.) Soo under Different Overwintering Conditions

Abstract

Dianthus giganteiformis subsp. pontederae (A. Kern.) Soó is a protected perennial endemic to the Pannonian region whose fragmented populations require effective conservation measures. Although in vitro propagation has been successfully applied to this taxon, little information is available on the post-acclimatization performance of propagated plants under outdoor conditions. The aim of this study was to evaluate the overwintering survival, flowering, and post-winter performance of in vitro-propagated plants under outdoor and greenhouse overwintering conditions. A total of 160 acclimatized plants representing 20 seed-derived genotypes (Seed IDs) were included in the experiment. Half of the plants were overwintered outdoors under a protective horticultural fleece, while the remainder were maintained in a moderately heated greenhouse (13–15 °C). Plant survival, flowering, flowering stem production, and plant vigor were monitored from November 2025 to June 2026. Treatment effects were evaluated using Pearson's chi-square test, Cramer's V, the paired Wilcoxon signed-rank test, and Spearman's rank correlation. Outdoor overwintering resulted in higher survival (75.0% vs. 62.5%) and substantially higher flowering (75.0% vs. 30.0%) than greenhouse overwintering. Although the difference in survival was not statistically significant (p = 0.088), flowering differed significantly between treatments (p < 0.001). Genotype significantly influenced post-winter performance, with considerable variation among Seed IDs. The Final Performance Score was significantly higher following outdoor overwintering (p < 0.001), while genotype performance remained positively correlated between the two overwintering treatments (Spearman's ρ = 0.659, p = 0.002). These results demonstrate that in vitro-propagated D. giganteiformis subsp. pontederae can successfully establish, survive winter, and flower under outdoor conditions. The observed genotypic variation highlights the importance of maintaining multiple genetic lines during ex situ propagation. Overall, the study supports the use of micropropagation as an effective tool for the ex situ conservation of this protected taxon and provides practical guidance for its long-term cultivation and conservation management.