PLANT-REGENERATION FROM CALLUS AND PROTOPLASTS IN MEDICAGO-POLYMORPHA

Seventeen ecotypes of the wild species Medicago polymorpha adapted to a Sardinian (Italy) environment have been evaluated for their response to tissue culture. The accession Samughero-Albi was the more respondent for callus induction and, together with Usassai, showed the highest regeneration capacity on media containing 1 mg l-1 2iP and 0.1 mg l-1 IAA. The morphogenetic response was also affected by the explant source. The hypocotyl-derived-calli were the best regenerating tissues. Regenerated plantlets were difficult to root and it was possible to obtain plants with a well developed root system only after 5-7 weeks of culture on media containing 2iP and IAA both at 0.2 mg l-1. Mesophyll cells were the best protoplast yielding source but only those isolated from roots were able to divide and to regenerate plants. Results are discussed in relation to the genotype specificity for the morphogenetic response and the feasibility of using M. polymorpha in the somatic hybridization with M. sativa.