Wednesday, November 15, 2006
249-5

Generation and Evaluation of Tetraploid Hybrids in Bahiagrass.

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

Cattle production systems of the southeastern USA are mainly based on warm-season grasses. Bahiagrass, Paspalum notatum Flügge, is well adapted to these systems because of its marked persistence under heavy grazing conditions. More productive bahiagrass cultivars are needed in order to improve productivity in these systems. The tetraploid race of this species reproduces by apomixis, which can be an attractive trait for the enhancement of crop species. Apomixis mediates the formation of large genetically uniform populations and perpetuates hybrid vigor through successive seed generations. The objectives of our work were 1) to generate segregating bahiagrass populations by hybridizing selected sexual and apomictic bahiagrass tetraploids, 2) to evaluate these populations, and 3) to select superior hybrids for further evaluations. A segregating population containing 823 hybrids was generated by crossing eleven 4x sexual lines as females with four 4x apomictic lines as males. Field evaluation of these progeny showed a large amount of variability among progeny in terms of growth habit, reproductive expression, regrowth at end of the season, and frost resistance. A selection index was developed and the top 20% of progeny plants was identified based on the index. Apomictic male parents, Argentine and Tifton 7, and sexual female parents 106, 2-2-7, 4‑36-1, and Q4188, resulted in a higher proportion of superior progeny. A 3:1 ratio between sexual and apomictic (facultative + obligate apomictic) plants, and a 9:1 ratio between others (facultative apomictic + sexual) and obligate apomictic plants were found in the progeny. Selected apomictic lines will undergo additional evaluations and superior sexual plants may be used as female parents in future crosses.


Handout (.pdf format, 93.0 kb)