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Ten years field trial observations of ri-TDNA cherry Colt rootstocks and their effect on grafted sweet cherry cv Lapins

Rugini, Eddo, Silvestri, Cristian, Cristofori, Valerio, Brunori, Elena, Biasi, Rita
Plant cell, tissue, and organ culture 2015 v.123 no.3 pp. 557-568
Rhizobium rhizogenes, adverse effects, cherries, clones, cytokinins, dwarfing, farmers, field experimentation, flowers, fruit quality, genes, genetically modified organisms, girdling, hydrogen peroxide, phenotype, putrescine, reproductive behavior, rooting, roots, rootstocks, scions, transfection, transfer DNA, vegetative growth, vigor
Ten year field trials of ri 1855 T-DNA cherry Colt plants have been examined for their vegetative and reproductive behaviours and for their effect on grafted “Lapins”. These plants have been regenerated in vitro from roots produced after the infection with Agrobacterium rhizogenes wild type. The clones, from different transfection events (A, B and E) showed different morphologies since their first months in pots. This allowed an initial selection for the suitable dwarf rootstocks to fit farmers’ needs. The clones with the most reduced size, clones A and E, showed the typical “hairy root” phenotype more distinctly than clone B. in vitro All the clones’ explant rooting resulted very high even in auxin-free medium, while in vivo, both semi-hardwood cuttings and layering suckers, resulted very low. Neither exogenous treatments with cytokinins, in an attempt to re-establish the hormonal unbalance caused by the bacterial genes, nor putrescine, H₂O₂ and girdling were effective in promoting satisfactory rooting. The ri-TDNA Colt clones, when used as rootstocks, reduced the bi-member plant size by different extents, according to their vigour and did not affect fruit quality. Clones A and E drastically reduced the plant size with a slight reduction of flower density and an extension of vegetative growth in Autumn. Clone B on the other hand, resulted in a promising dwarfing rootstock for sweet cherry since it did not induce any evident negative effect on scion. This work encourages the selection of suitable dwarfing rootstocks among plants originated from several different modified roots, in other species as well. In particular, the work addresses the issue of whether these plants should or should not be subject to the same GMO law.