In vitro selection of actinidia deliciosa clones tolerant to nacl and their molecular and in vivo ecophysiological characterisation

Throughout the world salinity reduces horticultural yield. We examined the possibility to obtain kiwifruit somaclones tolerant to NaCl through in vitro selection of calli and their regeneration. Selected calli were obtained from leaf pieces of in vitro grown plants of Actinidia deliciosa (cv Tomuri) in the presence of NaCl (85.5mM). Calli were induced to regenerate and 5 tolerant shoot lines, in presence of NaCl maintained multiplication ability and did not show chlorosis, vitrification or leaf curling. RAPD analyses showed polymorphisms in 2 of the 5 selected clones. Eco-physiological characterisation was performed in a climatic chamber on acclimatised plants. Gas exchange measurements performed in vivo on the control and on one of the 2 tolerant clones revealed a decrease in photosynthetic activity, stomatal conductance and leaf transpiration as consequence of the salt treatment, however, a higher recover was obtained for the tolerant clone in net photosynthesis over time. Measurements of leaf fluorescence of chlorophyll-a demonstrated a significant decrease in the quantum photochemical yield (FvFm-1) in the salt treated control, while the selected clone maintained values similar to the untreated plants. The different response of the selected clone to salt stress conditions was confirmed from preliminary field tests. Our experiments suggest that somaclonal variation induced by in vitro organogenesis under selective pressure can be useful to select Actinidia deliciosa lines tolerant to NaCl.