Evaluation of salt-tolerant Azospirillum spp and its role in improvement of wheat growth parameter

Abstract

Eighteen isolates of Azospirillum were collected from different sites at Kafrelsheikh Governorate. The isolates were cultivated on nitrogen-free malate (NFM) medium supplemented with different NaCl gl-1 concentrations (Zero, 0.7 and 1.5%) and tryptophan to study the salt tolerant in vitro and indol acetic acid production. Pots were used to evaluate the most salt-tolerant and efficient species and soils of this experiment had artificially salinized with different salinity levels. The most salt-tolerant A10 and A11 species were genetically identified by 16S rRNA sequencing and the results revealed to be closest matched at 99% A. lipoferum strains and selected to inoculate wheat plants. The investigated A. lipoferum species had variable divergence growth at different salinity levels. Actually, increased salinity had deleterious effect on IAA production. In addition, salinity had deleterious effect on dry weights of plants, number and dry weight of branches, total chlorophyll, sodium and potassium% with increasing salinity levels. But, inoculation with associative nitrogen fixation A. lipoferum isolates enhanced the previous parameters. Thus, inoculation with the salt-tolerant A.lipoferum isolates decreased the deleterious effect of salt stress on wheat plants.