Germplasm Collections and Morphological Studies of Andropogon gayanus-Andropogon tectorum Complex in Southwestern Nigeria

Morphological studies were carried out on collections of Andropogon gayanus-Andropogon tectorum complex from Southwestern Nigeria. This is with the view to providing full characterization of the accession of the two species of Andropogon and elucidating their population dynamics. Morphological data from selected accessions of A. gayanus and A. tectorum from different parts of Southwestern Nigeria were collected and characterized using an adaptation of the Descriptors for Wild and Cultivated Rice (Oryza spp), Biodiversity International. Preliminary morphological description of the accessions were carried out at the point of collection. Garden populations were raised from the vegetative parts of some accessions and maintained in Botanical Garden of the Obafemi Awolowo University, Ile-Ife. The data obtained were subjected to inferential tests and Duncans multiple range test. The results revealed a distinct distribution pattern of the two species of Andropogon in the area of study which suggests a south-ward migration of Andropogon gayanus, that is from the northern vegetational zones of Nigeria to the southern ecological zones. The migration of A. gayanus around Igbeti with occasional occurrence of A. tectorum along the roadsides without any distinct phenotypic hybrid, and Budo-Ode in Oyo State is established as the southern limit of the spread of A. gayanus. This migration of A. gayanus to the South is not an invasion but a slow process. There was no A. gayanus encountered in Osun, Ondo, Ekiti and Ogun States. Andropogon gayanus and Andropogon tectorum do not only emerge from the rootstocks rapidly but can also produce independent propagules by rooting at some nodes. The plants can spread by means of these propagules even if it does not produce sexual or apomictic seeds. This potential for vegetative propagation in addition to the perennial habit confer considerable advantage for colonization by the Andropogon gayanus-Andropogon tectorum complex.