Infectivity and effectiveness of different species of arbuscular mycorrhizal fungi in micropropagated plants of Mr S 2/5 plum rootstock P. Fortuna, S. Citernesi, S. Morini, M. Giovannetti and F. Loreti Agronomie, 12 10 (1992) 825-829 DOI: 10.1051/agro:19921015