EFFECT OF GROWTH-REGULATORS CONCENTRATIONS ON MORPHOLOGICAL DEVELOPMENT OF MERISTEM-TIPS IN DIOSCOREA-CAYENESIS D-ROTUNDATA COMPLEX AND D-PRAEHENSILIS

The effects of NAA/BA concentrations and GA(3) supply, on the developm ent of meristem-tips excised from microshoots of one Dioscorea cayenen sis-D. rotundata cultivar and of one D. praehensilis genotype, have be en examined. Three NAA/BA concentrations and one addition of GA(3) to one medium were compared after 3, 8 and 11 months of culture without s ubculturing. Culture support was a superimposed agar/agarose (5 v/1v); growth regulators were used in a MS medium with agarose as top layer support. For the two clones, rooting was significantly decreased by th e highest NAA/BA concentrations, and budding was independent of treatm ents. Shoot elongation was more associated with lower NAA/BA concentra tions (Dioscorea cayenensis-D. rotundata) or independent (D. praehensi lis). Callusing appeared more linked to higher NAA/BA concentrations ( D. praehensilis) or independent Dioscorea cayenensis-D. rotundata). GA (3) supply did not improve regeneration. The genotypic differences are marked by a better survival and a better regeneration into rooted pla ntlets for the cultivar.