Effect of wheat (Triticum aestivum L.) seed inoculation with bio-fertilizers on reduction of drought stress damage

In order to study the effects of seed wheat inoculation with VA mycorrhiza and azotobacter bio fertilizers on reduction of late season drought stress damage, an experiment was conducted in agricultural and natural resources research center of Tehran province on 2011-12. Four levels of seed inoculations (non-inoculation, inoculation with VA mycorrhiza fungus, inoculation with azotobacter and combined inoculation (fungus plus bacteria) in a randomized complete block design with three replications were evaluated. Another same experiment (same treatments, same soil type and same planting, cultivation and harvest condition), but in drought stress environment (non-irrigation at start of flowering stage) conducted. Drought stress at start of flowering stage caused a significant decrease by 21.3% on grain yield from 7763 to 6108 kg/ha that was mainly due to significant reduction of number of seed per spike, number of fertile tiller, biological yield and TKW. Seed protein percentage and seed phosphorus percentage increased at stress condition but this was significant only for protein percentage. Effect of seed inoculation with bio fertilizers was significant for all traits except harvest index. All three levels of inoculation increased wheat grain yield significantly, but the positive effect of mycorrhiza was more than the others. The difference between seed inoculation with each one of micro organisms and dual inoculation was not significant. The amount of grain yield for S2I1 treatment (drought stress condition and without inoculation) was 5437 kg/hac, but inoculation with mycorrhiza (S2I2), azotobacter (S2I3) and dual inoculation (S2I4), increased the grain yield to 6463, 6129 and 6403 kg/hac respectively. Protein yield and percentage and phosphorus yield and percentage increased significantly for all three inoculation treatments. Drought stress effect on RWC was not significant but seed inoculation had a significant effect on RWC.