The genus Pennisetum is reported to have more than 140 species (Brunken, 1977). However, this may be an overestimation because some taxonomists assigned species names to races. Pennisetum species have base chromosome numbers of x = 5, 7, 8, and 9 with ploidy levels ranging from diploid to octoploid. The base number of most species is x = 9. Species can be annual or perennial and reproduce sexually, by apomixis, or by facultative apomixis. Most species make a contribution to forage production in their native habitats, some with greater potential than others. Pearl millet [Pennisetum glaucum (L.) R. Br.], an annual is described in Chapter 15 (Hanna et al., 2004, this publication), and buffelgrass {P. ciliare (L.) Link [syn. Cenchrus ciliaris L.]}, a perennial, in Chapter 13 (Hanselka et al., 2004, this publication). Napiergrass or elephant grass [P. purpureum Schumach] is valued as a forage crop in the wet tropics. Kikuyugrass (P. clandestinum Hochst. ex Chiov.) provides high-quality pastures and turf at higher altitudes in the tropics and subtropics. Flaccidgrass (P.flaccidum Griseb.) and P. orientate L.C. Rich. make important contributions to pasture and forage production in some parts of the world (Jauhar, 1981) and along with kikuyugrass is described by Stapf and Hubbard ( 1934) and Turpe (1983). These three are small-seeded, polyploid, apomictic, and have the basic chromosome number of 9. Breeding can be difficult in these apomictic species, but low levels of sexuality can be found which allows for the production of new genotypes by hybridization. Even in obligate apomictic species, Bashaw et al. (1992) showed that new hybrid types can be produced through fertilization of unreduced eggs.
