Ultrastructural and biochemical changes at the preinfection stage of mycorrhizal formation by two isolates of Pisolithus tinctorius F. Lapeyrie, J. Lei, N. Malajczuk and J. DexheimerAnn. For. Sci., 46 Supplement (1989) 754s-757sDOI: https://doi.org/10.1051/forest:198905ART0168