Culture in vitro d'embryons isoles de noyer commun (Juglans regia L. )

French. La technique in vitro de production de pousses à partir des axes embryonnaires de noyer dépend successivement de deux facteurs : - la concentration en saccharose qui, utilisée à 20 ou 40 g/1, permet d’obtenir des plantules enracinées sur un milieu simple de KNOP dilué de moitié, après 60 jours de culture ; - la N6-benzylaminopurine à 1 mg/1 qui déclenche après 30 jours de culture la formation de pousses axillaires sur des épicotyles excisés des plantules précédentes et ensemencés sur le milieu de MILLER à 20 g/1 de saccharose.

English. The main objective of the walnut improvement program of the Forest Tree Improvement Station (INRA-Orléans) is the vegetative propagation of hybrids created by controlled cross. For that purpose, establishment of an in vitro micropropagation technique from embryos could save much time. In this work, we present the technique used to obtain good development of isolated embryos of Juglans regia L. Two main factors studied were the concentration of sucrose in the culture medium and the effect of N6-Benzylaminopurine. 1) Sucrose effect. Naked embryos were transferred from disinfected nuts to Knop’s medium supplemented with sucrose at 0, 10, 20, 40, 80 and 160 g/1. After 50 days of culture (tabl. 1 and fig. 1) the best growth of epicotyls and roots was obtained with 20 g/1 of sucrose. Low concentration (less than 40 g/1) promoted epicotyl growth whereas high concentration (80 g/1) increased root growth. When sucrose was absent or at too high concentration (160 g/1) embryo development did not occure. In all treatments the epicotyls of embryos formed a terminal bud and 10 to 16 lateral buds in two rows. None of those buds flushed. 2) Effect of N6-Benzylaminopurine. The developed embryos obtained on the medium showing the best growth (knop 1 /2 and sucrose 20 g/1) were transferred, with and without roots to the medium of Miller supplemented or not with BAP 1 mg/1 or BAP 1 mg/1 and GA3 10 mg/1. Flushing of at least one bud per plant occured only if there is BAP in the medium (tabl. 2). On BAP alone the mean number of buds elongated per explant was about 2 times greater on excised epicotyls than on whole embryos. There was a depressive effect of GA3 on elongation of buds particularly on excised epicotyls. Apparently there is a strong effect of roots on the development of buds. With this technique, we are able to establish directly walnut embryos in in vitro culture, the first step for a mass micropropagation process.