Effect of medium composition and light supply on in vitro shoot proliferation in Ilex paraguariensis (Aquifoloaceae)

In vitro regeneration of shoots from nodal segments (containing one axillar y bud) of 'yerba mate' (Ilex paraguariensis St. Hil.) was studied under def ined nutritional and environmental conditions. Shoot regeneration occurred in several media tested. The best nutrient medium contained the mineral sal ts and vitamins of Murashige & Skoog medium at 1/4 strength, plus 3% sucros e and I mg 6-benzyladenine L-1. The explants were incubated at 27 degrees C , 14 hr photoperiod (116 mu mol m(-2)s(-1)). As much as 60% of the nodal se gments cultured formed multiple shoots (with an average of 2.8 shoots per e xplant). Pretreatment of the donor plants with darkness as well as the cult ure under different light treatments did not modified these results. Rootin g of regenerated shoots was poor and the plantlets regenerated did not surv ived when transferred to soil. The use of this protocol for micropropagatio n of selected clones of Ilex paraguariensis is discussed.