Short-day and Low-temperature Induction in Lolium

The requirements for floral induction of several outbreedingpopulations of Lolium perenne, L. multiflorum, and L. rigidumhave been studied. Floral induction can be brought about byeither low temperature (0–30° C.) or short day (8hr.) independently, but short day is ineffective at low temperatures. The exact inductive requirement varies with the population.The summerannual Westerwolds ryegrass needs neither cold norshort day, the winter-annual Wimmera ryegrass shows a quantitativeresponse, while the perennial varieties from north-west Europehave an obligatory requirement for either cold or short daybefore floral induction. This relation between the annual orperennial habit and the inductive requirement was confirmedin a number of Mediterranean collections of L. perenne and L.rigidum. Considerable genetic variation in inductive requirement couldbe detected within each outbreeding population, and rapid responseto selection proved possible in Wimmera, Irish, and Kent ryegrass.