Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/24/2011
Publication Date: 5/23/2011
Citation: Qu, L., Widrlechner, M.P. 2011. Variation in the Breeding System of Prunella vulgaris L. HortScience. 46(5):688-692.
Interpretive Summary: Selfheal (Prunella vulgaris) is a perennial herb in the mint family with a long history of use as a traditional medicine. Recent studies have found that selfheal possesses anti-inflammatory, antiviral and anti-bacterial properties, and it is likely that this will lead to increased commercial demand. There are very few research publications on the cultivation and genetics of this plant. By using selfheal populations originally collected from different parts of the world, we studied the breeding system of this species by examining variation in the size and arrangement of flower parts and the timing of pollen release, and by bagging flowers to determine how well they produce seeds without cross pollination. Two types of flowers, one with female parts extending past the open flowers (exerted styles), well removed from the male parts, and the other with shorter, inserted styles, were found among 30 populations. Two populations originally collected from Asia uniformly displayed exerted styles, and 27 had inserted styles. One population from Oregon had plants with both types of styles. By examining unopened flowers collected from 7 populations under a microscope, including those with both exerted and inserted styles, we found that they all release pollen before the flowers open. Through bagging flowers, we found that selfed seed production varied widely (6 to 94%) among 8 populations. The one with 6% selfed seed also had exerted styles. Our findings document variability in selfheal’s mating system. This information should be useful both to genebank managers in developing efficient methods for producing seeds and conserving this species and to plant breeders in creating effective breeding and selection strategies to improve this medicinal crop.
Technical Abstract: Prunella vulgaris (Lamiaceae), commonly known as selfheal, is a perennial herb with a long history of use in traditional medicine. Recent studies have found that P. vulgaris possesses anti-inflammatory, antiviral and anti-bacterial properties, which may lead to increased commercial demand. To date, research publications on P. vulgaris cultivation and genetics are scarce. Using accessions originally collected from different geographical regions, we investigated the breeding system of this species by observing variation in floral morphology, time of pollen release, and selfed-seed set in bagged flowers and isolated plants. Two types of floral morphology, one with exerted styles, extending past open corollas when viewed from above, and another with shorter, inserted styles, were found among 30 accessions. Two Asian accessions uniformly displayed exerted styles, and 27 accessions had inserted styles and another from Oregon displayed within-population variation in this trait. Microscopic observation of 7 accessions, including both exerted and inserted types, revealed that they all release pollen to some degree before flowers open. Using bagged flowers, we found that selfed-seed set varied widely among 8 accessions, ranging from 6 to 94%. However, bagging may sometimes underestimate seed set. The two accessions with the lowest rates when bagged increased seed set by 350 and 158%, respectively, when we evaluated single, un-bagged plants in isolation cages. The accession with 6% selfed-seed set when bagged also had exerted styles. These findings suggest that mating system in P. vulgaris may be evolving, and that understanding breeding-system variation should be useful in developing efficient seed-regeneration protocols and breeding and selection strategies.