Determination of the best culture medium for establishment, propagation and conservation in vitro of citrus rootstocks

In micropropagation and in vitro conservation various nutrient media have been used for regeneration of citrus rootstocks. In this respect, the present study was conducted to define, among three culture media, one of common use (MS) and two developed for arboreal species (RMAN and WPM), the best formulation for the establishment, propagation and conservation in vitro. Plantlets from 10 citrus rootstocks grown in the three media were micropropagated and conserved in vitro for 18 months, during which they were submitted to three subcultures at six-month intervals. The RMAN and WPM formulations provided the highest seed germination percentages, but the analysis of the morphogenetic response during the subcultures revealed that the composition of RMAN resulted in loss of the regenerative capacity of the explants in the second subculture. As occurred for RMAN, there was reduced development of the plants cultivated in MS with each new subculture. The plants grown in WPM, maintained or increased their regenerative capacity during the subcultures. Among the media studied, WPM was the most efficient for micropropagation and in vitro conservation, while the RMAN limited the in vitro germination of the rootstocks.