Plant production of walnut Juglans regia L. by in vitro multiplication

Lateral-bearing varieties of walnut require the use of vigorous rootstocks. For that reason, in 1988, Ctifl started an experimental programme which continues to day, to select new walnut rootstocks that are vigorous and tolerant to cherry-leaf roll virus (CLRV) from seedlings of J. regia L. Walnut propagation using traditional techniques like cuttings or layers is very difficult or impossible. So, in order to multiply the identified clones, the conditions of plant production by micropropagation have been investigated and clearly defined. Micropropagation, actually well mastered for J. regia L. allowed the production of numerous and very homogeneous plants, not only with clones selected as rootstocks but also with varieties, which allows to envisage the suppression of the rootstock, subject to the good behaviour of own-rooted varieties (study in progress).