Bread wheat can be grown all over the world due to its broad genetic diversity. Detailed knowledge of the physiological and genetic factors influencing the start and length of the flowering period could contribute to the breeding of genotypes with better adaptation to present and future changes in the environment. The global climatic changes could influence the distribution of the average temperature and the pattern of rainfall in the future. These environmental components determine basically the volume of food production and the support of domesticated animals of the biosphere.

Central Europe including Hungary is located at the meeting point of the Oceanic, Continental and Mediterranean climatic zones resulting in special climatic conditions, due to the year-to-year fluctuation in intensity with which these three climatic zones influence weather in overlapping or mixed forms.

Cereals are able to adapt to these variable climate conditions as a result of the wide range of genetic diversity present in these species. One of the most important components of adaptation is flowering time, which is determined to a great extent by gene groups that regulate the vernalization requirement, i.e. the cold period that induces the transition from the vegetative to the generative phase (VRN genes), the photoperiod sensitivity (PPD genes) and the earliness per se (EPS) genes. Several gene families (VRN1, VRN2, VRN3 and VRN4) take part in the vernalization requirement. Based on the phenotyping data and gene expression patterns it has been proved that there are epistatic interactions between the VRN1, VRN2 and VRN3 genes; therefore, it is difficult to determine the primary regulation gene in the vernalization process. However, VRN to have a main role. In wheat, PPD-A1, PPD-B1 and PPD-D1 are the most important genes regulating photoperiod sensitivity. It is generally accepted that the most intense genetic effect is exerted by the dominant PPD-D1a allele, followed by the dominant PPD-B1a and PPD-A1a alleles. Allelic variation of EPS genes may result in differences of a few days in flowering time, independently of environmental stimuli. In this review our aim is to summarize the molecular-genetic aspects of these three regulating systems.

Keywords: vernalization genes (VRN), photoperiod response (PPD), earliness per se (EPS) genes