THE CHOICE OF AGROBACTERIUM STRAIN FOR TRANSFORMATION OF KIWIFRUIT

The choice of Agrobacterium strain is one of the key parameters required for development of an efficient Agrobacterium-mediated transformation. Leaf strips from in vitro grown kiwifruit plants were transformed using three avirulent Agrobacterium tumefaciens strains (GV3101, EHA105 and LBA4404) and one virulent strain (A281). Each strain harboured the pART27-10 binary vector which encodes an nptII gene for kanamycin resistance and the uidA gene for histochemical GUS staining. Over 70% of calli derived from the three avirulent strains regenerated shoots and all these shoots initiated roots. However, less than 20% of calli from the virulent A281 strain produced normal shoots and roots. The highest efficiency was obtained with strain EHA105. GUS activity was detected in all calli and the transgenic nature of regenerated plants was confirmed by PCR and Southern blot analysis. Agrobacterium-mediated transformation using EHA105 is currently being used for high-throughput functional genomic studies in the genus Actinidia. More than 700 transgenic plants in four Actinidia species have been produced during the last three years.