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Title: A Survey of Apomixis and Ploidy Levels Among Poa L. (Poaceae) Using Flow Cytometry

Author
item KELLEY, ALICIA - UTAH STATE UNIVERSITY
item JOHNSON, PAUL - UTAH STATE UNIVERSITY
item Waldron, Blair
item Peel, Michael

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/25/2009
Publication Date: 7/1/2009
Citation: Kelley, A.M., Johnson, P.G., Waldron, B.L., Peel, M. 2009. A Survey of Apomixis and Ploidy Levels Among Poa L. (Poaceae) Using Flow Cytometry. Crop Science 49:1395-1402

Interpretive Summary: Poa, commonly known as bluegrass, includes over 500 species including Kentucky bluegrass which is the most common turf grass in the US. Poa is complex, both in reproductive mode and genetics, with many species apomictic (reproduction without sexual recombination) and highly variable in chromosome number. Crossing different species within Poa has potential to improve stress tolerance in common turf grass. This study was conducted to identify individuals/species that are sexually reproducing and of similar ploidy (chromosome number) level. A total of 83 Poa accessions representing 33 species from the National Plant Germplasm System were analyzed for reproductive mode and ploidy level using flow cytometric techniques. Overall, sixty percent of the species had at least one apomictic or facultative apomictic accession. The remaining 40% were sexual. Thirty-three percent of the species had no sexual accessions. These results of reproductive mode and ploidy level analysis, including some species not studied before, emphasize the wide variabiliy in Poa, both among and within species. This information will be useful to plant breeders and allow more success in making crosses among the Poa species.

Technical Abstract: Poa, commonly known as bluegrass, includes over 500 species of which at least 40 have agronomic importance. Poa is complex, both in reproductive mode and genetics, with many species apomictic and highly variable in chromosome number. In order to more efficiently develop improved varieties of Poa, identifying sexually reproducing individuals, and utilizing species of similar ploidy levels will yield the greatest interspecific breeding success. To address these needs, we examined apomixis frequency and ploidy levels in a collection of Poa species. A total of 83 Poa accessions representing 33 species from the National Plant Germplasm System were analyzed for reproductive mode and ploidy level using flow cytometric techniques. Overall, sixty percent of the species had at least one apomictic or facultative apomictic accession. The remaining 40% were sexual. Thirty-three percent of the species had no sexual accessions. Autonomous apomixis was newly identified in P. bactriana and P. bulbosa in addition to it being previously reported in Poa nervosa. Poa annua and P. trivialis were identified as obligate sexual, and P. nervosa as obligate apomictic. Two of four P. palustris accessions exhibited facultative apomixis. Ploidy levels among sexually reproducing Poa accessions ranged from 2n=2X=14 to 2n=12X=84 with most accessions between 2n=3X=21 to 2n=8X=56. Among apomictic accessions, ploidy levels ranged from 2n=3X=21 to 2n=10X=70 with most between 2n=4X=28 and 2n=10X=70. These results of reproductive mode and ploidy level analysis, including some species not studied before, emphasize the wide variability in Poa, both among and within species.