Abstract:
Most legumes in natural
conditions form a symbiosis with arbuscular
mycorrhizal (AM) fungi. AM fungi in saline
soils have been reported to improve salinity
tolerance and growth in plants. In the
present study, interaction between
mycorrhizal fungus, Glomus mosseae, and
salinity stress in relation to plant growth,
nitrogen fixation, and nutrient accumulation
was evaluated in alfalfa (Medicago sativa).
Two alfalfa cultivars (Bami and Yazdi)
were compared under different levels of
salinity with and without mycorrhizal
inoculations. Salt stress resulted in a
noticeable decline in shoot and root dry
matter accumulation, resulting in a decline
in the shoot to root ratio (SRR) in all plants.
However, Bami was found to be more
tolerant to salinity than Yazdi. Inoculated
plants exhibited better growth and biomass
accumulation under stressed as well as
unstressed conditions. Mycorrhizal
colonization (MC) was reduced with
increasing salinity levels, but the
mycorrhizal dependency (MD) increased,
which was more evident in Yazdi.
Nodulation was completely inhibited under
salt stress conditions for both non - AM
inoculated alfalfa varieties. Nodulation only
occurred in inoculated plants. Nitrogenase
activity was reduced with increasing salt
concentrations. AM inoculated plants had
considerably higher nodule numbers, dry
weights, and nitrogenase activity under
nonsaline environments. Bami had a
comparatively lower Na+ concentration and
higher K+ and Ca2+ concentrations than
Yazdi. Although nitrogen (N) and
phosphorus (P) contents declined with
increasing salinity, Bami had higher levels
of N and P, as compared with Yazdi. Plants
inoculated with Glomus mosseae had better
plant growth and nitrogen fixation under salt
stress.
