Genome Relations Between an Intraspecific Paspalum Dilatatum Hybrid and Two Diploid Paspalum Species

An intraspecific dallisgrass, Paspalum dilatatum, hybrid (2n = 45) was crossed with P. notatum (2n = 20) and P. juergensii (2n = 20). Four hybrids of the P. notatum × intraspecific dallisgrass hybrid cross were studied cytologically and had 30 chromosomes. Meiosis was irregular and the mean pairing relationships at metaphase I were 27.37 I and 1.31 II. Of 22 hybrids obtained from the intraspecific dallisgrass hybrid × P. juergensii cross, 21 hybrids had 30 chromosomes and 1 had 31. Meiosis was relatively regular with an average of 10.38 I and 9.81 II per cell. These findings indicate that the dallisgrass hybrid and P. notatum are not closely related, whereas the dallisgrass hybrid and P. juergensii apparently have a common genome. It was also shown that yellow anthered dallisgrass can generally be substituted cytologically for common dallisgrass. Megasporogenesis was normal in all hybrids. However, the sexual tissue generally deteriorated, resulting in complete abortion of the female gametophyte.