Identification of different cultivars of turf grasses is often very difficult. In a preliminary attempt to identify different cultivars o f Cynodon dactylon (L.) Pers.. random amplified polymorphic DNA (RAPD) analyses of some well-known cultivars used in South Africa, i.e. Bayview. Cape Royal, Florida. Hamsmith. Silverton Blue. Skaapplaas and Titdwart. as well as 10 potential new cultivars, were done. These results were used to determine the genetic distances among cultivars. Only five primers w ere needed to obtain a specific fragment pattern for each cultivar. The degree o f amplification w as used as an additional criterion by including all visible fragments, excluding very faint fragments and only including the brightest fragments. The neighbour-joining trees o f C.  dactylon showed best resolution from the data set w ith all visible fragments included. although fragment intensity did not affect the tree topology. The cultivars Silverton Blue and Bayview exhibited the greatest genetic variation and two potential new cultivars were identified. RAPD analyses can. therefore, be used to distin­guish between different C. dactylon cultivars and to determine the genetic variation between them by calculating genetic distances.

Two main basic chromosome numbers occur in the majority of southern African Chloridoideae, i.e., 9 and 10, the majority being x = 10. Two main evolutionary pathways, one following x = 10 and the other following an aneuploid/dysploid reduction to x = 9 are suggested for the subfamily. Evidence indicates that x = 9, 10 are paleopolyploid basic chromosome numbers, with x = 10 derived from x = 5. This corresponds to the closely related Panicoideae where five is accepted as the basic chromosome number.

Polyploidy is frequent among the grasses. This study indicates that it has a high frequency in the subfamily Chloridoideae, where more than 90% of the studied specimens are polyploids. These levels range from diploid (2n = 20 for x = 10 and 2n = 18 for x = 9) to 16-ploid (2n = 160) for x = 10 in Ctenium concinnum Nees and 20-ploid (2n = 180) for x = 9 in Hilaria mutica Benth. This polyploid trend is seen in southern Africa, as well as worldwide. Analysis indicates that many polyploids are alloploids, suggesting extensive hybridization within this group. This is supported by the presence of apomixis in many mem bers of the subfamily. Both polyploidy and apomixis are thought to be important evolutionary mechanisms in Chloridoideae as well as closely related Panicoideae, and have a high frequency in southern Africa. Due to the stable ecological, geographical and climatological history of Africa, the continent is ideally suited for the stabilization of hybrid complexes by means of apomixis and polyploidization.

Polyploidy is frequent among the grasses. This study indicates that it has a high frequency in the subfamily Chloridoideae, where more than 90% of the studied specimens are polyploids. These levels range from diploid (2n = 20 for x = 10 and 2n = 18 for x = 9) to 16‐ploid (2n = 160) for x = 10 in Ctenium concinnum Nees and 20‐ploid (2n = 180) for x = 9 in Hilaria mutica Benth. This polyploid trend is seen in southern Africa, as well as worldwide. Analysis indicates that many polyploids are alloploids, suggesting extensive hybridization within this group. This is supported by the presence of apomixis in many members of the subfamily. Both polyploidy and apomixis are thought to be important evolutionary mechanisms in Chloridoideae as well as closely related Panicoideae, and have a high frequency in southern Africa. Due to the stable ecological, geographical and climatological history of Africa, the continent is ideally suited for the stabilization of hybrid complexes by means of apomixis and polyploidization.

CHROMOSOME STUDIES ON AFRICAN PLANTS. 17. THE SUBFAMILIES ARUNDINOIDEAE AND DANTHONIOIDEAE

No abstract

THE BASIC CHROMOSOME NUMBER OF THE GENUS PENTAMERIS (ARUNDINOIDEAE)