Abstract
In order to improve knowledge on the role of the mycorrhizal and rhizobial symbiosis in salt
stress tolerance of Acacia saligna and Lotus creticus plants, examine if the symbiotic
performance of AMF in salt stress condition is related to their adaptation to salinity or it depend
on specificity with host plant, a study of mycorrhizal status was undertaken in two salt sites and
in the rhizosphere of indicated plants (two dunes) to isolate and select efficient isolates for
subsequent use in inoculation of Acacia saligna and Lotus creticus plants.
A difference is noted between salt and dune sites. In dune plant species, mycorrhizal
colonization level is significantly more important than in halophyte plants. Saline soils were the
richest in AM spores, suggesting that salinity affect negatively AM spore germination and root
colonization of host plants, causing an accumulation of spores in soils. The morphological
characters of spores highlighted a diversity of glomale which is higher in dune soils. Thanks to
this characterization, 45 morphotypes originated from saline soils and from the rhizospere of A.
saligna and L. creticus are collected. Moreover, results obtained shows that edaphic and soil
conditions affect behavior, diversity and distribution of AM fungi.
Monospecific cultures of one spore representative of each morphotype were conducted to
produce inoculum of 42 morphotypes. Then, morphotypes performance under combined drought
and salinity stresses was tested and five AM isolates were selected (one isolate from each site) :
AT6, LT3, LB2, SST5 et 3S6.
Growth and biochemical parameters were measured in A. saligna and L. creticus plants
inoculated with already selected AM isolates, a mixture of AMF isolated during this work and a
combination of this mixture and a strain of rhizobium and subjected to NaCl (150 mM and 300
mM respectively). All parameters showed that salinity has adversely affected the development of
A. saligna and L. creticus seedlings. However, inoculation helped the seedlings to withstand the
negative effect of salt. The best tolerance is shown in plants inoculated with rhizobia- mixture of
AMF, on the other side, simple inoculation, with AMF isolated during this work, had no effect
on A. saligna and L. creticus seedlings tolerance. This results show also that, for A. saligna,
AMF efficiency appears to be unrelated to their adaptation to salt or to the plant host so that it is
linked to the host plant in the case of L. creticus.
Keywords: Mycorrhizal symbiosis, rhizobial symbiosis, tolerance, Acacia saligna, Lotus
creticus, abiotic stress.