Efficient, Season-Independent Seed Germination in Black Cohosh (<i>Actaea racemosa</i> L.)

Abstract

Seed germination in black cohosh was systematically examined in eighteen populations including 15 USDA accessions with an effective protocol for the consistent, season independent germination of this valuable alternative specialty crop. Two in vitro approaches were investigated for breaking the complex double dormancy of black cohosh seeds for year round germination of plants for increased cultivation and laboratory studies. The first approach was a two-step alternat ing temperature stratification in which surface sterilized seeds were incubated in darkness at 25?C for two weeks fol lowed by incubation at alternating temperatures of 20?C and 8?C for 12-hour periods with a 16-hour photoperiod for 12 months. The second was a three-step-approach that involved initial stratification of seeds in darkness at 25?C for two weeks, followed by incubation at 4?C in darkness for 3 - 4 months and then cultivation at 25?C with a 16-hour photope riod to generate seedlings. Although both approaches broke double dormancy for black cohosh seed germination, the three-step-stratification technique yielded higher percentage seed germination in less time when compared to the two-step scheme, including for seeds stored over two years. Additional factors of critical importance for efficient ger mination included the selection of healthy and viable seeds, as well as thorough but non-excessive surface sterilization to control bacterial and fungal contamination. The in vitro approach for black cohosh germination allowed year-round cultivation and culture of a number of different genotypic accessions to enable laboratory based studies on cell culture and transformation approaches to aid in deciphering gene-metabolite relationships in this important medicinal plant.