In Vitro Culture and Micropropagation of Ryegrass (Lolium spp.)

The ryegrasses (Lolium spp.) can be classified into eight different species. However, since these species are partly or fully interfertile, this classification is not always unequivocal (Breese and Tyler 1986). Two of these species, perennial ryegrass (Lolium perenne L.) and Italian ryegrass (Lolium multiflorum Lam.) are agriculturally very important. Strictly annual forms of Italian ryegrass are often referred to as Westerwolds ryegrass (Lolium multiflorum Lam. ssp. westerwoldicum). Hybrid ryegrass (Lolium × hybridum Housskn.) is derived from artificial or naturally occurring crosses between Italian and perennial ryegrass. Perennial and Italian ryegrass are diploid (2n = 14), outbreeding and self-incompatible species. No naturally occurring tetraploids have ever been found. However, by means of colchicine treatment, tetraploid varieties (4n = 28) have been made artificially (Wit 1959).