Variation among hexaploid Paspalum dilatum Poir. regenerants from tissue culture.

Authors: Venuto, Bradley; CROUGHAN, SUE - LSU AGCENTER; PITMAN, W - LSU AGCENTER; Jessup, Russell; RENGANAYAKI, K - TEXAS A&M; Burson, Byron

Submitted to: Australian Journal of Experimental Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/4/2007
Publication Date: 8/6/2007
Citation: Venuto, B.C., Croughan, S.S., Pitman, W.D., Jessup, R.W., Renganayaki, K., Burson, B.L. 2007. Variation among hexaploid Paspalum dilatum Poir. regenerants from tissue culture. Australian Journal of Experimental Agriculture. 47:1109-1116.

Interpretive Summary: The perennial warm season grass, known as paspalum in Australia and ‘common’ dallisgrass in the U.S.A., is an important forage grass for livestock producers in the southern Gulf coast region of the United States. Producers in this region have expressed a desire for improvements in this grass and an improved cultivar of dallisgrass would be welcomed. However, due to the unique manner in which dallisgrass reproduces, efforts to improve the grass through traditional methods have not been successful. A close relative to common dallisgrass, known as Uruguayan dallisgrass, is a new source that may be superior to common dallisgrass. As with common dallisgrass, improvement of this new type through conventional breeding methods is also difficult because of its method of reproduction. However, the use of tissue culture to produce variation in the Uruguayan dallisgrass 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 regenerates for useful agronomic variation and evaluate their forage potential and nutritive value, and 3) determine the genetic relatedness of the regenerates and their parental source. One hundred and seventy-eight plants were selected from 2,372 regenerates in preliminary screening for higher forage nutritive value. Thirty-seven of these were planted into replicated field plot trials at two locations. None of these regenerates were superior to the parental Uruguayan dallisgrass for forage nutritive value. However, two regenerates, 3440 and 3441, produced more forage than either the Uruguayan or common dallisgrass in evaluation tests for three years at one of the two locations. Data from molecular analyses indicate genetic variation among these two regenerants and the Uruguayan dallisgrass. This study supports the superior performance of the Uruguayan dallisgrass compared to the widely grown common dallisgrass, documents some improvement in the Uruguayan dallisgrass, and demonstrates potential for further improvement.

Technical Abstract: The common biotype of Paspalum dilatatum, called paspalum in Australia and dallisgrass in the U.S.A., is a pentaploid obligate apomict and efforts to improve the 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 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 reported, and may offer a means for improving the species. The objectives of this research were to 1) regenerate plants of Uruguayan dallisgrass through tissue culture, 2) screen the regenerates for useful agronomic variation and evaluate their forage potential and nutritive value, and 3) determine the genetic relatedness of the regenerates and their explant sources. One hundred and seventy-eight plants were selected from 2,372 regenerates in preliminary screening for higher forage nutritive value. Thirty-seven of these were planted into replicated field plot trials at two locations. None of these regenerates were superior to the parental Uruguayan biotype for forage nutritive value. However, two regenerates, 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. Data from AFLP analyses indicate small genetic variation between two of the Uruguayan accessions and these two regenerants which could account for the differences in forage yield between 3440 and 3441 and the Uruguayan accessions.