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

Abstract

Twenty facultative Argentinean commercial wheat cultivars classified as early and late maturity were grown during 2004 and exposed to different sowing dates from June to September under field conditions with the aim of establish how the duration of different pre-and post-flowering phases are affected when plants are exposed to a wide range of temperature and photoperiod regimes. The changes in the duration of the emergence-anthesis phase, measured in thermal time, between early and late maturity groups were mainly associated with differences in the photoperiod sensitivity (in average 74 and 165 ^ˆ C d h^-1 for early and late maturity groups, respectively) without significant differences in the optimum photoperiod (13.4 hs) and/or intrinsic earliness (in average 829 and 907 ^ˆ C d for early and late maturity groups, respectively). Similar responses were observed in the two pre-anthesis phases analyzed. Because of only three cultivars evidenced vernalization requirements this trait seems not appear as an important attribute to be considered by breeding into the Argentinean commercial cultivars, with the aim of lengthening to the pre anthesis phases. The duration of the post-anthesis phase was less variable not only among cultivars, also between early and late maturity groups with an average duration of 450 ^ˆ C d. The data obtained from this study allowed the construction of thermo-photoperiodic models and include this information into friendly software named CRONOTRIGO ^© (www.agro.uba.ar/catedras/cerealicultura/servicios.htm) for predicting the timing of phenological events as the beginning of stem elongation, flowering and physiological maturity