W027 Detection of Apomixis in an Octoploid, Alpine Species, Draba oligosperma (Brassicaceae)

Date: Tuesday, January 17, 2012
Time: 4:50 PM
Room: Pacific Salon 6-7 (2nd Floor)
Ingrid Jordon-Thaden , University of Florida, Gainesville, FL
Marcus A. Koch , Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
Draba oligosperma, few-seed whitlow-grass, a rock-loving, high-altitude perennial that is distributed throughout the North American Cordillera. We present the first concrete evidence of autonomous apomixis in Draba oligosperma, Brassicaceae, by seed screening with flow cytometry, and clearing of ovules using Herr’s solution for tracking nucellar tissue development. Preliminary data indicates it is aposporus agamospermy, but more samples are being investigated. Upon seed screening of both sexual polyploid and diploid Draba species (D. glabella, D. hispanica, D. magellanicaD. nemorosaD. oreades, and D. siliquosa) and Draba oligosperma, we observed a 100% rate of apomixis in the samples tested in only D. oligosperma. The remaining species tested were all sexual. In addition, for three growing seasons, abnormalities in stamen development were documented in greenhouse culture. We observed that summer flowers, the stamen appears to develop, but the filament does not elongate. Positioning the anthers below the stigma when it is receptive. In the spring, however, the filaments elongate to an equal position as the stigma, as most Draba species do, but no pollen is shed in either case. Despite the morphological differences of the mature silique between the two seasonal flowers, the seeds from both types of flowers were determined to be apomictic. This species has long been proven to be apomictic by Mulligan and Findlay (1970) by underdeveloped pollen and subsequent development of seed in greenhouse studies. The key importance of this finding is that apomixis in cruciferous plants has been reported (and proven) until now ONLY for the genus Boechera. In contrast to Boechera with apomixis present on the diploid (and triploid/tetraploid) level, in this Draba species apomixis might have arosen after/as a consequence of hybridization and polyploidization.