A temporary immersion system for mass micropropagation of pitahaya (Hylocereus undatus)

Abstract

Scaling-up techniques in temporary immersion systems are an alternative for commercial micropropagation. In vitro propagation of pitahaya (Hylocereus undatus) using temporary immersion with liquid culture medium improves micropropagation efficiency compared to the conventional method in semisolid medium. The objective of this work was to evaluate the efficiency of traditional culture and temporary immersion during micropropagation of pitahaya to facilitate the rapid establishment of new commercial plantations of high genetic and phytosanitary quality. Semisolid culture, liquid media in partial immersion and temporary immersion in an Ebb-and-Flow bioreactor were evaluated. Also, in temporary immersion, different immersion frequencies (every 4, 8, 12, and 16 h) and culture densities (5, 10, 15 and 20 explants per bioreactor) were evaluated. For the multiplication stage, new shoots and length were recorded per explant at 45 d of in vitro culture and in the acclimatization stage, the survival percentage was determined at 30 d of greenhouse cultivation. A temporary immersion of 2 min every 4 h and 15 explants per bioreactor was the best culture system, obtaining on average 10.7 shoots per explant with a length of 1.9 cm. No significant differences were observed among treatments during acclimatization, obtaining survival percentages of 98%-100%. This study reports for the first time a protocol for scaling-up techniques in temporary immersion for commercial micropropagation of pitahaya (and for any species of the Cactaceae family) and its establishment in a productive plantation.

Keywords: Bioreactor system; Cactaceae; Dragon fruit; In vitro culture; Semisolid medium.

Fig. 1

Ebb-and-Flow bioreactor used in this study. a stand by period, plants stay in the upper flask while medium stand in the storage tank, (b) during immersion period air pressure is applied to the medium storage tank and the liquid medium is moving to the culture bottle and c after immersion period, solenoid valve prevents the passage of air and the medium is draining out by gravity

Fig. 2

Effect of culture system, immersion frequency and explant density in TIS on in vitro multiplication of Hylocereus undatus cv Write after 45 days of culture. a Semisolid medium, (b) liquid medium in partial immersion, and c temporary immersion. d–g Temporary immersion for 2 min every 4, 8, 12 and 16 h, respectively. h–k Explant density: 5, 10, 15 and 20 explant per bioreactor, respectively. Bar = 1 cm

Fig. 3

In vitro derived Hylocereus undatus cv Write plants. a Acclimatized plantlets obtained from Ebb-And-Flow Bioreactor after 30 d of ex vitro culture under greenhouse conditions, (b) Flowering plant after 24 months of ex vitro culture, and c–d productive plant and fruit quality of tissue-cultured plants