Variation among hexaploid Paspalum dilatatum Poir. regenerants from tissue culture

Abstract

The common biotype of Paspalum dilatatum Poir. (dallisgrass) 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: (i) regenerate plants of Uruguayan dallisgrass through tissue culture, (ii) screen the regenerants for useful agronomic variation and evaluate their forage potential and nutritive value, and (iii) determine the genetic relatedness of the regenerants and their explant sources. In total, 178 plants, selected from 2372 regenerants in preliminary screening, were evaluated for forage nutritive value. Thirty-seven of these were planted into replicated field plot trials at two locations. 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 3 years at one of the two locations. Data from AFLP analyses indicate genetic variation between two of the Uruguayan accessions and these two regenerants. This variation could account for the differences in forage yield between 3440 and 3441 and the Uruguayan accessions.