Evaluation of Mutual Effect of Ectoine(s) producing Streptomyces and wheat at salt conditions

Soil microorganisms with potential for alleviation of salt stress in combination with plant growth promotion would be a promising approach in sustainable agriculture. In the present study, interaction of two varieties of bread wheat (Triticum aestivum L.), Pishtaz and Zarrin and three salt tolerant ectoines producing bacteria including S. Cellulosae, S. rimosus C-2012 and Streptomyces Strain S2 was undertaken in normal and salt conditions. Diversity and distribution of 16S rRNA gene of rhizospheric bacteria in soil inoculated with Streptomyces in salt and normal conditions were studied by denaturing gradient gel electrophoresis (PCR-DGGE) method. Results showed that bacterial cell free extract of all strains reduced root length but S2 and C-2012 increased plant dry weight related to control. Soil treatment with strain C-2012 increased Pishtaz root and shoot fresh and dry weight and Zarrin root fresh and dry weight in normal conditions. At salt conditions, plant growth promotion of C-2012 limited to increase Pishtaz root fresh and dry weight and Zarrin leaf area. Root extract of wheat plantlets increased C-2012 population (cfu) and decreased mycellial aggregation. The effect of Pishtaz root extract on bacterial cfu was more than Zarrin. Based on PCR-DGGE data, the diversity of 16S rRNA gene in rhizosphere changed when Streptomyces or salt was added to soil. PCR-DGGE profiles of 16S rRNA gene in rhizosphere of wheat varieties were also different. Our observations certify that beneficial role of salt tolerant Streptomyces for wheat growth promotion at normal or saline conditions is plant variety dependent.