In vitro adventitious budding on Pinus pinaster cotyledons and needles

Adventitious budding can be induced on two types of Pinus pinaster Ait. organs. Cotyledons (10‐mm‐long), derived from 8 to 10‐day‐old seedlings, show morpho‐genetic response when an appropriate mineral solution is used (NH4+/K+= 1). Of the various cytokinin concentrations added to this optimal mineral medium, 0.8 μM BAP (6‐benzylaminopurine), with 5 nM NAA (1‐naphtaleneacetic acid), promoted organogenesis best. Buds were induced from outer mesophyll layers. Short shoots and the elongating needles (70‐mm‐long) were collected from cuttings of a mature tree (10‐years‐old). These cuttings benefited from physiological advantages of a well‐developed root system (by heating the substrate). In order to stimulate in vitro organogenesis, they had been sprayed every week from March to May with 10 μM BAP. When cultivated in the presence of 10 μM BAP and 25 nM NAA, 79% of the explants produced buds from dome‐shaped meristematic cell clusters that pre‐existed at the top of the short shoots. Moreover, among these, 42% gave rise to adventitious buds induced from proliferating mesophyll cells at the needle base. The morphologies of the two kinds of shoots were similar. Adventitious budding on these two different explants should allow vegetative multiplication of selected seedlings and elite trees.