In vitro multiplication and growth improvement of Olea europaea L. cv Canino with temporary immersion system (PlantformT)

Olea europaea L. cv Canino shoots were micropropagated to test two different culture systems: (1)on conventional semi-solid medium in glass jars and (2)in liquid culture in a PlantformT bioreactor. The temporary immersion system, PlantformT, is a new propagation approach that uses liquid culture, where shoots undergo periodic immersion in liquid medium alternated with dry periods, avoiding gas accumulation through forced ventilation. This study proposes a protocol to improve in vitro propagation of olive reducing production costs. Our findings revealed that olive shoots propagated in PlantformT, with an immersion frequency of 8 min every 16 h and additional ventilation, showed good adaptability and better growth rates than those cultured in conventional system. Overall, the PlantformT improves in vitro culture of 'Canino', showing higher proliferation, shoot length and better vigour of shoots. Moreover, the study found no significant differences in shoot length when 5 or 10 µM zeatin was applied in PlantformT (3.04 and 3.13 cm, respectively); it is, therefore, possible to achieve efficient olive proliferation also with half hormone concentration. The positive performance of the bioreactor approach was also confirmed by Relative Growth Rate index. This is the first documented study of the PlantformT technique for olive propagation.