Topolins and Red Light Improve the Micropropagation Efficiency of Passion Fruit (Passiflora edulis Sims) ‘Tainung No. 1’

Abstract

Passion fruit is a commercial crop of economic importance worldwide, with recent increases in demand for high-quality plants for commercial production. Plant tissue culture is widely used for the mass propagation of many commercial crops, however its application on passion fruit is challenged by the problem of low reproducibility, leaf chlorosis, and growth retardation resulted from in vitro culture. The aim of this study was to evaluate the effects of cytokinins and light quality on in vitro culture of nodal segments of passion fruit ‘Tainung No. 1’. Three aromatic cytokinins were tested in a modified MS basal medium. The bud proliferation rates of segments initiated on a media containing 1 mg·L−1 meta-topolin riboside (mTR) or benzyladenine (BA) were not significantly different at the same concentration. Buds cultured on medium supplemented with mTR grew and elongated for 4 weeks, while buds on a medium containing BA formed rosettes. After transfer to a medium without plant growth regulators (PGRs), shoots rooted spontaneously within 8 weeks. Furthermore, the effects of continuous propagation under a high proportion of red light affected the subsequent plant growth. Red LED induced an increase in the chlorophyll content (2.71 mg·g−1) compared with other light qualities (1.05–2.63 mg·g−1) and improved plantlet quality. Acclimated plants were grown in the field, and the flower morphology and fruit set were of commercial quality. Findings showed that replacing BA with mTR as the main cytokinin and using a high proportion of red light during the tissue culture induction period produced high-quality plantlets in 3 months. This system is economical and will be further developed for the commercial propagation of passion fruit vines in the future.

Keywords

• passiflora edulis
• aromatic cytokinins
• leds
• propagation
• in vitro