Bioreactor Design for Plant Propagation

Plant tissue culture provides a means to proliferate plants without the requirement of going through seeds, thus enabling the rapid propagation of superior plants such as sterile hybrids or disease resistant varieties. We are developing this technology for increasing the productivity of cultivated plants including fungal resistant Theobroma cacao (Chocolate Tree) via embryogenesis and seedless watermelon varieties via organogenesis. Four untested watermelon varieties were compared to select the variety most amenable to shoot proliferation. Productivity of this variety was compared in temporary immersion bioreactors (TIBs) relative to the standard protocol on solid media. Cotyledon explants were dissected from germinated seedlings and cultured on MS media supplemented with benzylaminopurine (BAP) and indoleacetic acid (IAA), inducing shoot formation. Media was refreshed every three weeks. The cotyledon explants in TIBs developed much slower than their solid media counterparts, with some evidence of budding along the cut edges. The waxy coating on the cotyledon explants may have prevented the absorption of the liquid media. In contrast, secondary shoot proliferation was successful in TIB culture. This work establishes the feasibility of utilizing bioreactors for watermelon propagation while setting the stage for future process scale-up and the analysis of oxygen mass transfer limitations in the developing tissues.