Rooting and weaning of apple rootstock YP

Summary — Rooting and weaning of the Finnish apple rootstock YP were studied. Rooting was affected by carbohy-drate type of the in vitro medium and age of the shoots. The highest rooting rate was achieved when either 30 g/l su-crose or glucose was used in the rooting medium and shoots were maintained for 5-7 wk on proliferation medium. Shoots> 7 wk rapidly lost their ability to root. In preliminary experiments VA-mycorrhizal inoculation had a positive ef-fect on growth during weaning and subsequent development in the greenhouse. in vitro rooting / Malus / carbohydrates / VAM inoculation Résumé — L’enracinement et le sevrage du porte-greffe de pommier finnois YP. L’enracinement et le sevrage du porte-greffe finnois YP ont été étudiés. L’enracinement est influencé par le glucide du milieu et l’âge des tiges. L