Responses of wheat to vernalization and photoperiod

The effects of vernalization and photoperiod on times from planting of seedlings to ear emergence were measured in 68 Australian and 49 overseas varieties of wheat, comprising a broad spectrum of genetic material, in a glasshouse in Canberra (latitude 35¦S). Vernalization was carried out by growing germinated seedlings in the dark at 1-2¦C for 6 weeks. Long photoperiods (16 h) separated unvernalized plants into two distinct groups, corresponding to commonly recognized spring and winter types. Responses to vernalization were generally small under natural photoperiods (11-15 h), but much more pronounced in long photoperiods, particularly with winter wheats. In a second experiment, 24 varieties of wheat gave widely different responses to vernalization treatments. With 8 weeks' vernalization and long photoperiods, all varieties reached ear emergence within 66 days, but in some winter wheats 4 weeks treatment had little effect and 6 weeks gave incomplete vernalization. Under the conditions of these experiments, Australian wheats showed a wide range of responses to photoperiod and a narrow range of responses to vernalization compared with overseas varieties. The need to investigate the control of flowering time in obtaining varieties suited to the high-rainfall zone of Australia is discussed.