Impact of phosphate fertilization and arbuscular mycorrhiza on the development, nutrition and quality of micropropagated walnut rootstocks.

The English walnut (Juglans regia L.) is the main species cultivated for the production of edible nuts. Due to heterozygosis, the characteristics of agronomical interest of walnut cultivars are not inherited via seed propagation. In vitro plant tissue culture thus plays a key role in mass propagation of high-quality walnut rootstocks. Micropropagation of walnut explants needs an ex vitro acclimatization phase to repair the in vitro induced abnormalities, and further requires a post-acclimatization growth in greenhouse conditions when plantlets become photoautotrophic. However, poor survival and slow growth rates are common difficulties encountered in nurseries when establishing micropropaga…