Title: Variation in Breeding Systems in Hypericum Perforatum and Prunella Vulgaris Authors
Submitted to: Proceedings Assoc for Advancement of Industrial Crops (AAIC) Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: August 26, 2009
Publication Date: November 14, 2009
Citation: Qu, L., Widrlechner, M.P. 2009. Variation in Breeding Systems in Hypericum Perforatum and Prunella Vulgaris [abstract]. 21st Annual AAIC Meeting-The Next Generation of Industrial Crops, Processes, and Products. p. 44 Technical Abstract: The effective conservation of new crop germplasm and its efficient use in new-crop development both rely on a clear understanding of the crop's reproductive biology. Hypericum perforatum (St. John's wort) and Prunella vulgaris (Common selfheal) are two medicinal plant species with potential for crop improvement and increased cultivation. The North Central Regional Plant Introduction Station in Ames, Iowa serves as the active curation site for Hypericum and Prunella germplasm within the U.S. National Plant Germplasm System. Published reports indicate that H. perforatum is typically tetraploid and a facultative apomict. However, other ploidy levels are known, and the degree of sexual reproduction can vary widely among populations. Past research has noted that the floral morphology of P. vulgaris can vary from forms that are strongly inbreeding to those that can promote outcrossing. The objectives of our studies were to (1) develop protocols to use flow cytometry of individual seeds and plants to determine ploidy levels and the degree of apomixis in germplasm accessions of H. perforatum and (2) examine floral parts and conduct bagging experiments to determine the degree of self-pollination in P. vulgaris. Flow cytometry was used to evaluate individually ground seed and leaf samples of three accessions of H. perforatum. Using seed samples, we were able to confirm that all accessions were facultative apomicts with tetraploidy the predominant cytotype (85-91%), relatively few hexaploids (10-14%), and diploids (5%) detected in only one accession (Ames 27490). The proportion of seeds with sexually produced embryos varied among accessions from 17% in Ames 28292 to 43% in Ames 24790, with 6-34% resulting from the union of reduced (diploid) gametes. Leaf samples from seedlings were tetraploid (87-97%) and hexaploid (3-13%). In P. vulgaris, we found that pollen was often shed before the flowers opened. Accessions varied in the degree of separation between anthers and the stigmatic surface. Evaluation of seed production from bagged inflorescences revealed that plants with relatively small flowers from the Republic of Georgia (Ames 29156 and 29157) displayed the most selfing; bagged flowers had similar rates of seed set (ca. 80%) to those of open-pollinated flowers. Accessions collected from Oregon set 31% (Ames 29049) and 48% (Ames 29047) selfed seed, respectively, while an accession originally collected in Japan (Ames 29995) produced only 4% seed set when bagged. Information will be posted on the Germplasm Resources Information Network (GRIN) database about ploidy-level variation and the frequency of apomixis in H. perforatum accessions, and on variation in the degree of self-pollination in P. vulgaris. This will allow users to know which accessions may be expected to breed true from open-pollinated seed and which ones might be best suited for breeding and crop improvement through hybridization.