Response to increasing rates of boron and NaCl on shoot proliferation and chemical composition of in vitro kiwifruit shoot cultures

The in vitro response of kiwifruit (Actinidia deliciosa) to increasing concentrations of boron (B) and NaCl in the culture medium was studied. Kiwifruit shoot cultures were grown in vitro for 12 weeks on an MS medium containing two B concentrations (0.1 and 2 mM) combined with five NaCl concentrations (0, 10, 20, 40 and 80 mM). Kiwifruit produced the longest shoots with 2 mM B when NaCl concentration was 0--20 mM. More shoots were produced with 2 mM B for all NaCl treatments. More shoots were produced with 2 mM B and 10 and 20 mM NaCl. High B concentrations in the culture medium significantly increased shoot proliferation. Explants exhibited a moderate chlorotic appearance with 40 mM NaCl and shoots died with 80 mM NaCl. With 2 mM B, the B concentration of explants was 5--9X greater for the various NaCl treatments compared to the control. Increasing the NaCl concentration from 10 to 80 mM, resulted in higher Na and Cl concentrations in explants for all B treatments, while K and Ca concentrations decreased. Phosphorus concentration in the explants was significantly increased by increasing the NaCl concentration reaching a maximum value at 80 mM NaCl for the two B concentrations.