Genetic evaluation of interspecific hybrids between a sexual synthetic autotetraploid P. plicatulum × P. aff. wrightii apomictic tetraploid, of the Plicatula group of Paspalum

Abstract

Paspalum wrightii Hitchc. & Chase, of the Plicatula group of Paspalum, is characterized by vigorous indefinite rhizomes and erect stems. It grows in wet, roadside ditches or periodically flooded areas. It is a multiploid species with 2n = 20 diploid and 2n = 40 tetraploid chromosomes. Cytoembryological reports indicate that the diploid cytotype reproduces sexually, while a representative of the tetraploid cytotype is facultatively apomictic with some potential to generate siblings through sexual means. One botanically unclassified species resembling P. wrightii, named herein P. aff. wrightii, was collected in this geographic region. This accession was determined to be facultative apomictic and was used as the male parent in crossing with a colchicine-induced sexual autotetraploid genotype of Paspalum plicatulum Michx., resulting in 28 interspecific hybrids. The meiotic chromosome pairing behavior of both parents and their hybrids was primarily bivalent and quadrivalent, indicating that the tetraploid P. aff. wrightii is a segmental alloploidy. This was supported by the chromosome-pairing behavior in the hybrids recovered when the accession was crossed with the induced autotetraploid P. plicatulum. The P. plicatulum × P. aff. wrightii hybrids segregated by sexual and apomictic reproductive modes. In general, most interspecific hybrids inherited self-incompatibility from the female parent and others had very low fertility. The presence of sexual and apomictic hybrids in the progeny suggests that gene transfer through hybridization is a feasible tool in breeding programs for forage grass species in the Plicatula group.