Tools for conservation of Balsamorhiza deltoidea and Balsamorhiza sagittata: Karrikin and thidiazuron-induced growth

Wildfires are having both devastating and regenerative impacts on the ecosystems in the Pacific Northwest of North America. Balsamorhiza sagittata and B. deltoidea (balsamroot) are ecologically important species in this region, and B. sagittata populations are increasing, while B. deltoidea is critically imperiled. The aim of this research was to establish in vitro protocols for germination and regeneration of Balsamorhiza spp. to enable conservation efforts. It was hypothesized that karrikins, which are plant growth regulators released from burning plants during wildfires, would induce seed germination in Balsamorhiza spp. Three karrikins (KAR₁ KAR₂, and KAR₁₁) were tested for the ability to enhance germination in these species at two levels (5 or 10 µM). KAR₂ had the strongest positive effect on germination and induced 47% and 60% germination, respectively, in B. sagittata seeds compared to 14% germination obtained in the control (water agar media). In B. deltoidea, KAR₂ treatment resulted in a germination rate of 73.1% and 100%, compared to 69% in the control. A germplasm collection of seedlings of both species was established for conservation and regeneration experiments. Thidiazuron treatment (10 µM) induced formation of embryo-like structures in seedlings of both B. sagittata and B. deltoidea, with régénérants originating from the crown of seedlings. The present study provides in vitro methods for conservation and mass propagation of Balsamorhiza species.