Cytotaxonomic relationships in the genera Pennisetum and Cenchrus and the manipulation of apomixis

Abstract

The cytotaxonomic relationships of buffelgrass and birdwoodgrass were investigated to provide information for taxonomic classification and as a basis for a breeding program with these species. The relationship of these grasses to other species of Cenchrus Pennisetum was also considered. Buffelgrass x birdwoodgrass hybrids were used to study the inheritance of mode of reproduction and to predict the genotype of the birdwoodgrass parent. The results of the cytotaxonomic study indicate that these species are as closely related as individual ecotypes within either species. The parents were found to be completely cross fertile and their hybrids were as fertile as S₁ segregates from the sexual parent. Morphologically there was a rather complete intergradation between the parents. Both parents have the same chromosome number and their meiotic behavior and karyotype appear to be identical. Meiotic behavior in the F₁ hybrids was similar to the parents and there was no loss of chromosomes in advanced generations. Typical buffelgrass type plants were recovered in the advanced generations hybrids with birdwoodgrass type characters were recovered but not in combination to reconstitute the true birdwoodgrass type. Based upon these results the merging of birdwoodgrass and buffelgrass in a single species, Cenchrus ciliaris L. link, is recommended. Birdwoodgrass and hybrids with birdwoodgrass type inflorescences should be designated C. ciliaris var. setigerus (Vahl.) Maire. ...