Indole-3-acetic acid (IAA) producing Pseudomonas isolates inhibit seed germination and α-amylase activity in durum wheat (Triticum turgidum L.)

The role of plant-associated bacteria in plant physiology and metabolism is well documented, but little has been known about the roles played by Pseudomonas in durum wheat (Triticum turgidum L. var durum) growth and development. An in vitro experiment was conducted to observe the effect of the inoculation of four indole-3-acetic acid (IAA) -producing Pseudomonas isolates and exogenous IAA on seed germination traits and alpha-amylase activity of durum wheat. The results showed inoculation with all bacterial isolates led to a decrease in the germination percent, although the extent of the depression varied with the isolate. A significant relationship between concentrations of bacterial IAA and the germination inhibition percent in durum wheat seeds by different bacteria strains was observed. The results of this assay showed the effect of bacterial isolates on alpha-amylase activity after six and 8 days of inoculation was significant, while effect of these isolates on alpha-amylase activity after two and 4 days of inoculation was not meaningful. In addition, the exogenously applied IAA displayed a concentration-dependent effect on seed germination attributes and alpha-amylase activity, consistent with the possibility that the inhibitory effect of bacterial inoculation on seed germination was in consequence of bacteria-produced IAA. Therefore, it may suggested that the inhibitory role of IAA in seed germination and alpha-amylase activity should be taken into account during the screening of IAA-producing Pseudomonas isolates for durum wheat growth promoting agents.