B.C. Venuto1, W.D. Pitman2, R.W. Jessup1, B.L. Burson1, K. Renganayaki3, and S.S. Croughan2. (1) USDA-ARS, El Reno, OK 73036, (2) LSU Ag Center, Homer, LA 71040, (3) Department of Soil & Crop Sciences, Texas A&M University, College Station, TX 77843-2474
Common dallisgrass, Paspalum dilatatum, is a pentaploid obligate apomict and efforts to improve this important forage grass have not been successful because of its asexual reproduction and irregular meiosis. An apomictic hexaploid biotype, known as Uruguayan dallisgrass, is a new source of genetic variation that may be useful in improving the dallisgrass. As with common dallisgrass, improvement of this biotype via conventional breeding methods is difficult because of its apomictic reproduction. However, the use of tissue culture to produce somaclonal variation in the Uruguayan biotype has not been attempted and may offer a means for improvement. The objectives of this research were to 1) regenerate plants of Uruguayan dallisgrass through tissue culture, 2) screen the regenerants for somaclones with improved forage production and nutritive value, and 3) determine the genetic relatedness of the regenerants and their explant sources. One hundred and seventy-eight plants were selected from 2,372 regenerants in preliminary screening for higher forage nutritive value. Thirty-seven of these were planted into replicated field plot trials at two locations in Louisiana. None of these regenerants were superior to the Uruguayan biotype for forage nutritive value. However, two regenerants, 3440 and 3441, produced more forage than either the Uruguayan or common biotypes in evaluation tests for three years at one of the two locations. AFLP analyses indicated small genetic variation between two of the Uruguayan accessions and these two regenerants. This could account for the differences in forage yield between 3440 and 3441 and the Uruguayan accessions.
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