GENOME RELATIONS BETWEEN PASPALUM CONSPERSUM AND TWO DIPLOID PASPALUM SPECIES

Abstract

Paspalum conspersum Schrad. ex Schult., 2n = 4x = 40, was crossed with P. intermedium Munro ex Morong, 2n = 2x = 20, and P. jurgensii Hackel, 2n = 2x = 20, and the hybrids were studied cytologically to determine the relationship between these species. Thirteen P. intermedium × P. conspersum hybrid plants were produced; however, only eight survived. They had a chromosome number of 2n = 3x = 30. Meiosis was irregular with a chromosome pairing relationship of 19.87 univalents, 5.03 bivalents, and 0.03 trivalents per cell. These findings suggested that the two species have a partially homologous genome. The two hybrids obtained from the cross between P. jurgensii and P. conspersum had a chromosome number of 2n = 3x = 30. The mean chromosome pairing in these hybrids was 10.12 univalents. 9.86 bivalents, 0.08 trivalents, and 0.004 quadrivalents. The close bivalent pairing and a mean frequency of 9.86 bivalents suggested that the P. jurgensii genome was homologous to one genome of P. conspersum. Limited autosyndetic pairing of the P. conspersum chromosomes was also detected in both groups of hybrids. A standardization of genome formulas for the genus was proposed in which P. intermedium, P. jurgensii, and P. conspersum were represented by genome formulas of II, JJ, and I2I2 JJ, respectively. The genome relationships and formulas were discussed for other related Paspalum species.