Variability on Photoperiod Responses in Argentinean Wheat Cultivars Differing in Length of Crop Cycle

Abstract

Twenty facultative Argentinean commercial wheat cultivars classified asearly and late maturity were grown during 2004 and exposed to differentsowing dates from June to September under field conditions with the aimof establish how the duration of different pre-and post-flowering phasesare affected when plants are exposed to a wide range of temperature andphotoperiod regimes. The changes in the duration of theemergence-anthesis phase, measured in thermal time, between early andlate maturity groups were mainly associated with differences in thephotoperiod sensitivity (in average 74 and 165 degrees C d h(-1) forearly and late maturity groups, respectively) without significantdifferences in the optimum photoperiod (13.4hs) and/or intrinsicearliness (in average 829 and 907 degrees C d for early and latematurity groups, respectively). Similar responses were observed in thetwo pre-anthesis phases analyzed. Because of only three cultivarsevidenced vernalization requirements this trait seems not appear as animportant attribute to be considered by breeding into the Argentineancommercial cultivars, with the aim of lengthening to the pre anthesisphases. The duration of the post-anthesis phase was less variable notonly among cultivars, also between early and late maturity groups withan average duration of 450 degrees C d. The data obtained from thisstudy allowed the construction of thermo-photoperiodic models andinclude this information into friendly software named CRONOTRIGO((c))(www.agro.uba.ar/catedras/cerealicultura/servicios.htm) for predictingthe timing of phenological events as the beginning of stem elongation,flowering and physiological maturity.