Developmental responses of different hexaploid triticales to temperature and photoperiod

Abstract

The developmental responses to temperature and photoperiod of five hexaploid triticales (X Triticosecale Wittmack) of diverse origin (T64, SPA 69, UM3, Badger, 6TA419) and one wheat cultivar (Olympic) were examined in the field at Werribee, Victoria in 1974. Six times of sowing and the use of supplemental illumination, providing an 18 hour daylength at one of the two sites, created a range of different photoperiod and temperature treatments. The durations of the following phases were taken as the responses to phtoperiod and/or temperature: emergence to ear initiation (El), ear initiation to heading (IH) and anthesis to maturity (AM). The data from the natural and the 18 hour photoperiod regimes were analysed separately by stepwise regression analysis. The introduction of pseudovariables made it possible to study varietal effects. The order in which the varieties reached the various developmental stages changed very little with the successive times of sowing, but differed when the natural daylength was compared with the 18 hour regime. The responses of the triticales to temperature and photoperiod were quantitative. The duration of each phase was shortened by a longer mean daily photoperiod or a higher mean daily temperature, the photoperiod having a greater effect than the temperature. Large varietal differences caused low coefficients of determination of the El phase under natural and 18 hour photoperiod (43.9 and 6.4 respectively), when regression equations were fitted, which were common to all varieties. The values were higher for the IH phase (64.6 and 68.6 respectively), The introduction of the pseudovariables in the analysis resulted in equations accounting for 85.0-96.7 per cent of the variation in both phases under 18 hours or natural daylength. The varietal effect on the duration of the AM phase was small. The coefficients of determination of the regression equations for this phase under both the 18 hour and the natural photoperiodic regime ranged from 88.7 to 94.9. The response of the triticales to a vernalization treatment was small, indicating that vernalizing the seedlings prior to planting would not have greatly improved the predictive value of the regression equations.