In vitro shoot multiplication of Juglans spp.: the effect of different iron chelates and cytokinins

The effect of three different iron chelated forms on shoot multiplication and chlorosis of in vitro cultures of Juglans regia, 'Chandler', was evaluated. FeEDTA contained in DKW medium was replaced by NaFeEDTA or FeEDDHA, at the same iron concentration. Furthermore, NaFeEDTA or FeEDDHA were added to the DKW standard FeEDTA concentration to increase iron concentration to 10.1 mg L^-1. All the media were gelled with 5.7 g L^-1 agar or a combination of 3.5 g L^-1 agar and 8.0 g L^-1 pectins. In J. microcarpa the effect on shoot multiplication of the natural cytokinin, meta-Topolin (mT) (from 0.5 to 3 mg L^-1), in comparison with N⁶ benzyladenine (BA), was evaluated. In 'Chandler' no differences in shoot multiplication were found among the 3 chelated forms but the replacement of FeEDTA by FeEDDHA reduced chlorotic symptoms. Increasing iron content by a combination of FeEDTA and NaFeEDTA in medium gelled with the combination of agar and pectins was more effective in reduction of chlorosis and increasing shoot multiplication than the control and the addition of FeEDDHA. J. microcarpa shoot multiplication was positively influenced by the substitution of BA with mT in the culture medium.