Regulation and quality of flowering in Belgian pot azalea: interaction between genetics, physiology and culture conditions

Pot azalea (R. simsii hybrids) production in the Ghent area (Belgium) accounts approximately 40 million plants per year, generating a value of 45 million Euro. The past decade, growers and their associations have made efforts to improve both the quality of the vegetative as well as the flowering plants; however, suboptimal flowering is often observed. The non uniform opening of flower buds at anthesis when forcing the plants in the greenhouse or flowers that do not entirely open at the consumers place, even when plants are sold in the ideal candle stage, are often observed. Problems related to flowering are detrimental for the good image of azalea as a quality product. Different potential causes have been quoted: year round production schemes, shortening of culture time by use of multiple cuttings per pot and therefore less pinching, increased frequency of application of growth regulators, also around flowering time, use of stronger or more persistent growth regulators or application of assimilation lights when forcing the plants. However, a clear cut direct cause is seldom found; interaction between several elements related to the culture conditions should be at the base.
The main objective of this new research project is to identify influential factors related to flowering quality by an integrated approach focusing on (depending on the stage of the culture) the induction of processes at the level of RNA expression, on plant physiology and/or on experimental variation in culture conditions. In its practical implementation, we will start with the isolation of homeologous candidate genes for regulation of flowering, which will be transformed to expression markers using qPCR. Besides, relevant physiological, biochemical and morphogenetic parameters will be developed. Application of plant growth regulators to induce the transition from vegetative to generative growth under controlled cultured conditions is supposed to interfere with the later flowering process: need for cold, dormancy breaking of the flower buds, anthesis during forcing of the plants in the greenhouse and open flowering at living room conditions at the consumer. Focused experiments based on the currently used culture conditions by the growers are designed for the 3 critical stages (transition, dormancy breaking and anthesis). In a later stage of the project, we want to try to validate the results on batches of plants taken from the azalea growing companies that display abnormalities in flowering.