Improved Postharvest Quality of Inflorescences of fbp1::etr1-1 Transgenic Burrageara 'Stefan Isler Lava Flow'

Flowers of the complex orchid hybrid Burrageara 'Stefan Isler Lava Flow' had been shown previously to react sensitively to ethylene. Via Agrobacterium tumefaciens, the mutant ethylene receptor ETHYLENE RESPONSE 1 (etr1-1) from Arabidopsis thaliana under the control of the flower-specific promoter FLOWER BINDING PROTEIN 1 (fbp1) from Petunia hybrida was transferred to Burrageara. One single-copy event was analyzed in this study aiming to investigate the expression of the fbp1::etr1-1 transgene in different plant and flower organs by quantitative RT-PCR and the reaction of flowers and inflorescences to ethylene. It was shown that the heterologous promoter led to high expression levels in the perianth of the orchid flowers compared to low levels in leaves and roots. The expression shift to the first whorl (sepals) described here corresponds to extended expression of endogenous B class MADS box homeotic genes in orchids in general. The transgenic plants grew and developed similar to the wild-type plants, except for slightly faster rooting in vitro and smaller flowers. Flower longevity was improved by 7 days in 10 ppm ethylene. Moreover, bud drop starting at day 5 of incubation of inflorescences in 10 ppm ethylene in the wild-type was efficiently prevented for at least 19 days in the fbp1::etr1-1 transgenic plants. The function of the tissue-specific promoter fbp1 and the mutant receptor etr1-1 was shown for the first time in a monocotyledonous plant.