F. Piola et al., CONTROLLED MYCORRHIZAL INITIATION AS A MEANS TO IMPROVE ROOT DEVELOPMENT IN SOMATIC EMBRYO PLANTLETS OF HYBRID LARCH (LARIX X EUROLEPIS), Physiologia Plantarum, 95(4), 1995, pp. 575-580
This study represents the first report of in vitro mycorrhization of s
omatic embryo-derived plantlets. Effects of fungi on the rooting of pl
antlets as well as on their ultrastructure were studied. Embryo-derive
d plantlets of a hybrid larch (Larix x eurolepis Henry) were grown ase
ptically in the presence of four ectomycorrhizal fungi. One month afte
r inoculation with Laccaria laccata, Hebeloma cylindrosporum and Pisol
ithus tinctorius, the number of plantlets which had developed a well-g
rowing root system was significantly improved compared with controls.
Furthermore, root branching was strongly stimulated by L. laccata and
H. cylindrosporum, which were more efficient species than P. tinctoriu
s and Suillus grevillei. Development of the root system was concomitan
tly accompanied by an enhancement of shoot growth, except for plantlet
s inoculated with S. grevillei, which died after three to six months.
At the ultrastructural level, cross-sections of lateral roots made six
months after inoculation, showed the presence of a Hartig net in the
case oft. laccata and H. cylindrosporum, whereas no such net was obser
ved with the two other fungi. With S. grevillei, some perforating: hyp
hae penetrated the cortical cells and resulted in cell death. Evidence
of a relationship between structure and efficiency of the association
was found.