Improved shoot multiplication and development in hybrid hazelnut nodal cultures by ethylenediamine di-2-hydroxy-phenylacetic acid (Fe-EDDHA)

Abstract

Garrison, W., Dale, A. and Saxena, P. K. 2013. Improved shoot multiplication and development in hybrid hazelnut nodal cultures by ethylenediamine di-2-hydroxy-phenylacetic acid (Fe-EDDHA). Can. J. Plant Sci. 93: 511–521. Micropropagation of hybrid hazelnut cultivars is difficult because of their recalcitrant nature. The current study assessed the effect of different iron sources on in vitro shoot multiplication and subsequent plantlet development from nodal explants of the cultivar Geneva. Two chelated forms of iron, ethylenediamine di-2-hydroxy-phenylacetic acid (Fe-EDDHA) and ethylenediamine tetraacetic acid (Fe-EDTA) were tested to determine the effect on shoot development. Shoots were longer and had a higher number of nodes when cultured on a modified NCGR-COR medium supplemented with 230 µM Fe-EDDHA, whereas shoots failed to grow on a medium with 460 or 690 µM Fe-EDTA. All plantlets grown in the presence of Fe-EDDHA had more chlorophyll, larger leaves, and higher dry weights compared with Fe-EDTA. Electron microscopy of in vitro grown tissues revealed that the form of Fe influenced the number of granal and stromal lamellae per chloroplast, the number of thylakoids per granum, and the overall chloroplast structure. Nodal explants originating from the proximal end of stems developed longer shoots with more nodes than those derived from the distal region. The use of double-phase culture medium produced plants with longer shoots and more nodes, although these exhibited hyperhydricity, showed greater morphological variation, and contained less chlorophyll. These results demonstrate the efficacy of the use of Fe-EDDHA in growth medium for improving micropropagation efficiency of hazelnut.