In vitro micropropagation of critically imperiled Crocanthemum canadense (Cistaceae) and identification of endomycorrhizal symbionts

Crocanthemum canadense (L.) Britt. (Cistaceae), Rockrose, is a small perennial herb found in Eastern North America sand barrens. It is classified as critically imperiled in Nova Scotia under the Nova Scotia Endangered Species Act. Nova Scotia C. canadense populations continue to decline; recent counts estimate only 5000–5500 plants remain. To better understand C. canadense conservation, we completed ex-situ in vitro germination and propagation trials using seed collected from native Nova Scotia populations at 14 Wing Canadian Forces Base, Greenwood, Nova Scotia. Concurrently, soil was collected from the same locations to analyze belowground endomycorrhizal symbionts, arbuscular mycorrhizal fungi (AMF). Recent research has documented the presence of AMF within C. canadense roots, however, this is the first study to successfully identify AMF species present in-situ using single spore rDNA barcoding. C. canadense successfully germinated in vitro with high germination rates (average 86.6%) for one population (SB000147) maintained at room temperature with a 16-hour photoperiod. Successful vigor continued to be monitored with regular multiplication and transfers. Eight AMF spores were identified, all members of the genus Rhizophagus. Seven spores identified as Rhizophagus clarus and one as Rhizophagus irregularis. R. clarus are commonly found in many semi-arid environments now including sand barrens. This research will aid in the conservation and restoration of this critically imperiled species by further understanding beneficial soil fungi, an understudied component of the declining sand barrens habitat.