The effect of vernalization on the heading of Wimmera ryegrass (Lolium rigidum) and on five cultivars of perennial ryegrass (Lolium perenne)

Abstract

The responses of annual and perennial ryegrass to 0, 6, and 12 weeks artificial seed vernalization were determined by recording the percentages of plants heading and the leaf numbers at heading for populations of 40 plants grown in a glasshouse under continuous light. All plants of the annual L. rigidum headed without vernalization but the vernalized plants headed at a much lower leaf number than did the unvernalized controls. At least six weeks of cold treatment were needed for complete induction of the five cultivars of L. perenne examined. The vernalization responses of cultivars of Mediterranean origin were similar to those of the Australian Colac. It was shown that late heading in L. perenne is not always associated with a large cold requirement and it is suggested that photoperiod may be an important factor controlling heading of ryegrass in southern Australia.