In addition to its role in vernalization, temperature is an important environmental stimulus in determining plant growth and development. We used factorial combinations of two photoperiods (16H, 12H) and three temperature levels (11, 18 and 25 °C) to study the temperature responses of 19 wheat cultivars with established genetic relationships. Temperature produced more significant effects on plant development than photoperiod, with strong genotypic components. Wheat genotypes with PPD-D1 photoperiod sensitive allele were sensitive to temperature; their development was delayed by higher temperature, which intensified under non-inductive conditions. The effect of temperature on plant development was not proportional; it influenced the stem elongation to the largest extent, and warmer temperature lengthened the lag phase between the detection of first node and the beginning of intensive stem elongation. The gene expression patterns of VRN1, VRN2 and PPD1 were also significantly modified by temperature, while VRN3 was more chronologically regulated. The associations between VRN1 and VRN3 gene expression with early apex development were significant in all treatments but were only significant for later plant developmental phases under optimal conditions (16H and 18 °C). Under 16H, the magnitude of the transient peak expression of VRN2 observed at 18 and 25 °C associated with the later developmental phases.

Studies on plant development phases and yield component patterns of wheat are essential for a better understanding of adaptation in wheat. Our main aim was to carry out detailed phenological analyses of 18 wheat genotypes in three sowing times for determining the effect of sowing date on individual phenophases, and yield components. Sowing date had the single greatest effect on the start of intensive stem elongation. The longer vegetation period had a favourable effect on main spike length and on the spikelet number per spike, but had no influence on thousand-kernel weight and grain number per spike. The time between the first node appearance and start of intensive stem elongation had a significant effect on the number of reproductive tillers. A close association (R 2 = 0.191) was observed during the second phase of intensive stem elongation between the boot stage-to-heading interval and the number of spikelets per spike. Two-way analysis of variance on the yield components showed that the sowing date, as a main factor, had a weaker effect on the phenophases than on morphological and developmental parameters. The insensitive allele of the Ppd-D1 gene shortened the time required for first node appearance and heading both in autumn and spring sowing.