Wednesday, November 15, 2006
275-5

Reproductive Characterization of Several Natural and Induced Bahiagrass Tetraploids.

Carlos Acuna1, Ann Blount2, Kenneth Quesenberry1, Kevin Kenworthy1, and Wayne Hanna3. (1) University Of Florida, PO Box 110500, Gainesville, FL 32611-0500, (2) University of Florida - NFREC, 3925 Hwy 71, Marianna, FL 32446, (3) University of Georgia, PO Box 748, Tifton, GA 31793-0748

Bahiagrass, Paspalum notatum Flügge, is the predominant pasture and utility turf in Florida and the southern Coastal Plain Region of the USA. All tetraploid cultivars released in the USA for this species were superior apomictic genotypes selected from introduced germplasm. Apomictic bahiagrass improvement was hampered due to this method of reproduction, however variability can now be generated for breeding purposes by hybridizing apomictic and induced sexual tetraploids. Before this breeding approach can be efficiently used, the parental lines need to be carefully characterized for reproductive behavior. The present study examined the mode of reproduction of several natural and artificially induced bahiagrass tetraploids selected for a breeding program. A series of controlled pollination studies, and embryo sac observations were used to determine the reproductive behavior of this group of tetraploid accessions. Twenty artificially induced tetraploids were determined to reproduce sexually. Eighteen of them were classified as highly sexual, showing a single meiotic embryo sac in 100% of their ovules. In contrast, the other two were classified as facultative apomictic with high sexual expression, with more than 80% of their ovules having a single meiotic embryo sac. These 20 accessions were classified as cross-pollinated, setting an average of 2% seed when self-pollinated (range 0 to 6%), and 14% seed when cross-pollinated (range 8 to 35%). Two sexual lines, developed in Argentina, set an average of 21% seed when self-pollinated and 27% seed when cross-pollinated. Four selected ecotypes were determined to be facultative apomictic showing aposporous embryo sacs in more than 80% of their ovules. The cultivars Argentine and Wilmington and the experimental line Tifton 7 were determined to be highly apomictic showing only aposporous embryo sacs in 95% of their ovules. Argentine and Tifton 7 set an average of 32% seed when self-pollinated and 36% seed when cross-pollinated.


Handout (.pdf format, 113.0 kb)