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Cytogenetics of Paspalum urvillei x P. juergensii and P. urvillei x P. vaginatum Hybrids¹

Paspalum urvillei, 2n = 4x = 40, was crossed with P. vaginatum, 2n = 2x = 20, and P. juergensii, 2n = 2x = 20. A morphologically different type of P. urvillei (480) was also crossed with P. vaginatum. Three P. urvillsi x P. vaginatum, five P. urvillei 480 x P. vaginatum and 28 P. urvillei x P. juergensii hybrids were produced. This represents a crossability of 0.7%, 1.3%, and 1.1%, respectively, which is high for this genus. All hybrids were 2n = 3x = 30. Meiosis in P. urvillei x P. vaginatum and P. urvillei 480 x P. vaginatum hybrids was very irregular with numerous laggards and micronuclei. Their mean pairing relationships were 1.89 II, 26.23 I and 1.25 II, 27.50 I respectively. P. urvillei x P. juergensii hybrids had bivalent and univalent chromosome associations at meiosis with some laggards and micronuclei. The mean pairing relationships were 9.89 II and 10.29 I per cell. Chromosome pairing suggests a common genome in P. urvillei and P. juergensii but very little homology between P. urvillei and P. vaginatum. Megasporogenesis was normal in all hybrids. However, the functional megaspore generally deteriorated and an ovule without an embryo sac resulted. Sexual sacs in various stages of development were present in 1% of the ovules observed. None of the hybrids produced seed.

Key Words: Vaseygrass • Dallisgrass • Phylogenic relationship • Megasporogenesis

² Associate Professor of Cytogenetics, Agronomy Department, Mississippi State University and Research Agronomist, Plant Science Research Division, Agricultural Research Service, US Department of Agriculture and Mississippi Agricultural and Forestry Experiment Station.

Received for publication August 23, 1971.