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

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.