Germplasm collections and morphological studies of Andropogon gayanus–Andropogon tectorum complex in southwestern Nigeria

Abstract

Morphological studies were carried out on collections of the Andropogon gayanus–Andropogon tectorum complex from Southwestern Nigeria to provide full characterization of accessions of the two species and elucidate 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. A preliminary morphological description of the accessions was carried out at the point of collection. Garden populations were raised from the vegetative parts and maintained in Botanical Garden of Obafemi Awolowo University, Ile- Ife. The data obtained were subjected to analysis of variance and Principal Component Analysis was carried out to assess relationships among traits of the Andropogon gayanus and Andropogon tectorum. 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; from the northern vegetational zones of Nigeria to the southern ecological zones. The migration of A. gayanus around Igbeti with occasional occurences 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. The plants can spread by means of propagules even if they do not produce sexual or apomictic seeds. This potential for vegetative propagation in addition to the perennial habit confers considerable advantage for colonization by the Andropogon gayanus–Andropogon tectorum complex.