Submitted to: International Journal of Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/1999
Publication Date: N/A
Citation: Interpretive Summary: Hairy seeded paspalum (Paspalum pubiflorum) is a warm-season grass that is native to the southern U.S., including Texas. It is related to dallisgrass and bahiagrass. Even though it normally grows in low wet areas, it is found in some of the dry arid areas of Texas and appears to have more drought tolerance than most Paspalum species. Because of this, we were interested in determining if drought tolerance could be transferre from this grass to dallisgrass. Hairy seeded paspalum was crossed with different paspalum species, including dallisgrass. Unfortunately, all hybrids were small weak plants that lacked forage potential. The plants were not vigorous enough to determine if the genes for drought tolerance were transferred. The relationship between hairy seeded paspalum and the other species was determined by examining the chromosome pairing in the hybrids. It was determined that this grass and two different dallisgrass types have some chromosomes in common but more of their chromosomes were not similar. These findings indicate that dallisgrass and hairy seeded paspalum are not closely related and this lack of relatedness explains why hairy seeded paspalum can not be used to improve dallisgrass for drought tolerance or any other traits. These findings provide a better understanding of the relationship between dallisgrass and other Paspalum species.
Technical Abstract: This study reports the meiotic chromosome pairing behavior and method of reproduction of three Paspalum pubiflorum accessions and their F1 hybrids with P. juergensii (2n=2x=20; JJ), P. intermedium (2n=2x=20; II) and two P. dilatatum biotypes (yellow-anthered, 2n=4x=40, IIJJ and Uruguayan, 2n=6x=60, IIJJXX). The P. pubiflorum accessions were sexual hexaploids with 60 chromosomes which paired as 30 bivalents during meiosis. The yellow-anthered x P. pubiflorum F1 hybrids had 50 chromosomes with a mean pairing behavior of 36.62 I + 8.70 II, suggesting that one P. pubiflorum genome is homologous with either the I or J genome in the yellow-anthered biotype. F1 hybrids between P. pubiflorum and P. juergensii and P. intermedium had 40 chromosomes. Mean chromosome pairing behavior for the P. pubiflorum x P. juergensii hybrids was 24.05 I + 7.97 II + 0.12 III and 35.26 I + 2.37 II for the P. pubiflorum x P. intermedium hybrids. Paspalum mpubiflorum also was crossed with hexaploid Uruguayan dallisgrass and the hybrid had 60 chromosomes with a mean pairing frequency of 40.52 I + 9.74 II. These findings indicate that the common genome between P. pubiflorum and dallisgrass is the J genome. There also is some residual homology between the I genome and another genome from P. pubiflorum and appears to be limited pairing between a few members of the X genome in the Uruguayan biotype and members of a third P. pubiflorum genome. In most hybrids, the sporogenous tissue in the ovules deteriorated resulting in ovule abortion; however, the P. pubiflorum x Uruguayan dallisgrass hybrid was apomictic.