DIRECT GENE-TRANSFER TO PROTOPLASTS OF 2 GENOTYPES OF ASPARAGUS-OFFICINALIS L BY ELECTROPORATION

Callus-derived protoplasts of two genotypes of asparagus (Asparagus of ficinalis L.) were electroporated to introduce the beta-glucuronidase gene (GUS). The level of GUS transient gene expression and the viabili ty of the protoplasts were influenced by the voltage and duration of t he electric pulse. The transient expression level was enhanced by incr easing the plasmid DNA concentration and by the presence of polyethyle ne glycol (PEG) in the electroporation medium. A considerable increase in GUS activity was observed in presence of both PEG and upon heat-sh ock treatments compared to PEG treatment alone. An optimal level of GU S activity was obtained after electroporation with a capacitive discha rge of 500 V/cm and 94 ms duration in both genotypes. The two genotype s differed in their responses to in vitro culture and also showed vari able levels of transient expression. The present technique was found t o be suitable to obtain transgenic plants as the histochemical GUS ass ay revealed GUS activity in the protoplast-derived micro-colonies as w ell as in callus tissues.