Development of durum wheat and triticale cultivars as affected by thermo-photoperiodic conditions

The understanding of the interaction between thermo-photoperiodic condition s and the genetic control of anthesis date is fundamental in explaining the environmental adaptation of durum wheat and triticale cultivars. The devel opment of 8 durum wheat (Triticum turgidum L. var. durum) and 2 triticale ( x Triticosecale Wittmack) cultivars was studied at 3 sowing dates (Septembe r, November, and March) by observations on apex development, number and rat e of leaf appearance, spike fertility, and number and length of elongated i nternodes. Variation in anthesis date was mostly explained by the total number of leav es, which ranged between 8.3 and 15, and hence by the duration of the phase of leaf primordium production. Total leaf number also affected the length of the subsequent phase until flag leaf appearance. The phyllochron was inf luenced by both sowing date and genotype, and was minimum in the March sowi ng (87 degree-days). The genotypic variability in phyllochron was due eithe r to the variations in leaf number or to genotypic intrinsic differences. T ime to terminal spikelet stage was related to the number of spikelets per s pike and to the number of elongated internodes, although stem length depend ed more on internode length than on internode number. The number of spikele ts per spike was associated with leaf number, but their relationship was af fected by the thermal conditions during spikelet primordium initiation. No differences were observed between wheat and triticale cultivars, apart from the number of spikelets per spike.