Morphological Characteristics and Its Related Gene Expression in Cut Roses with Bent Peduncle Phenomenon

The bent peduncle phenomenon (BPP) causes low production of cut flowers in rose greenhouse cultivation. It is still not easy to avoid the BPP in the field because of unknown mechanisms. To address this challenge, this study was conducted to investigate the morphorogical characteristics including the form of floral organs and floral organ identity-related gene expression of BPP shoots in cut rose plants ‘Beast’. Morphological observation confirmed the fact that BPP was accompanied by the early formation and being phyllody of a specific sepal among five sepals, which gave rise to peduncle bending in the upper part of the phyllody with fasciation. Year-round BPP frequency in ‘Beast’ was in the range of 5% to 20% with seasonal change, increasing rapidly with an average temperature rise in summer. Except bent peduncle, the BPP shoots appeared to grow normally in terms of speed and size of floral development in comparison with normal. However, carbohydrate distribution to the floral part in BPP shoots was significantly reduced. Expression of floral organ identity-related genes was relatively higher at BPP flowering shoots more than normal shoots, which means BPP might be linked with flowering process in the level of its related gene translation. In summary, BPP may be considered by two distinct processes: First a special sepal’s illegal start for cell division in SAM and  affected by environmental factors, esp. heat stress. Second, a special sepal’s phyllody development accompanying with continuous auxin supply to the peduncle, resulted in BPP induction.