Direct regeneration of transformed plants from stem fragments of potato inoculated with Agrobacterium rhizogenes

Abstract

Mannopine and cucumopine straios of Agrobacterium rhizogenes were used for genetic transformation in two cultivars of potato (Solanum tuberisum L.). An overnight pretreatment of internodes with c~-naphthaleneacetic acid prior to bacterial infection was found to strongly inhibit shoot formation. On the contrary, infection with bacterial strains enhanced the frequency of shoot formation, compared with the controls, except for the strain 15834 which completely inhibited shoot formation in both potato cultivars. Shoots developed directly from the upper part of both inoculated and control explants, at a frequency ranging from 1 to 5 shoots per fragment. Among 93 shoots regenerated, 9 were found to be opine positive, and exhibited an altered phenotype with shortened internodes. Histological study revealed that the transformed shoots developed directly from cells of the internode sections, and not from induced roots. When grown in an insect-proof tunnel, the transformed plants had both altered and normal phenotypes and were able to produce tubers.