Molecular evidence of the influence of light length on the differences in the flower development of rose varieties in summer and autumn

Rose flowers are small in summer, which restricts their industrial development. Light regulates flower organ development in summer, but the underlying molecular mechanisms remain unknown. Changes in flower bud differentiation and flower morphology were observed between rose varieties and seasons; the flower size of ‘Corolla’ was compared under different light intensity treatments, and transcriptome data analysis and qPCR verification were conducted to identify responsible genes. Summer flowers and cell numbers and sizes were smaller than autumn flowers. In summer, the change in the flower size of ‘Corolla’ under different light intensities was not significant, but differences occurred between the 8- and 12-h groups, and flower bud differentiation started 7 days after treatment initiation in these groups. Transcriptome analysis indicated that auxin regulatory genes (RhARF8, RhSAUR72, and RhATL3) are key genes in summer flower development. A model of molecular mechanisms involved in regulating summer flower development through light length was constructed.