Plant-growth-promoting rhizobacteria and arbuscular mycorrhizal fungi modify alleviation biochemical mechanisms in water-stressed plants

Abstract

This study examined the effect of inoculation with the plant-growth-promoting rhizobacterium (PGPR) Pseudomonas mendocina Palleroni, alone or in combination with an arbuscular mycorrhizal (AM) fungus, Glomus intraradices (Schenk & Smith) or Glomus mosseae (Nicol & Gerd.) Gerd. & Trappe, on antioxidant enzyme activities (superoxide dismutase, catalase and total peroxidase activities), phosphatase and nitrate reductase activities and solute accumulation in leaves of Lactuca sativa L. cv. Tafalla affected by three different levels of water stress. At moderate drought, bacterial inoculation and mycorrhizal inoculation with G. intraradices, alone or in combination, stimulated significantly nitrate reductase activity. At severe drought, fertilisation and P. mendocina inoculation, alone or in combination with either of the selected AM fungi, increased significantly phosphatase activity in lettuce roots and proline accumulation in leaves. Total peroxidase (POX) and catalase (CAT) activities increased in response to drought, whereas superoxide dismutase activity decreased. Inorganic fertilisation and both combined treatments of PGPR and AM fungus showed the highest values of leaf POX activity under severe drought. The highest CAT activity was recorded in the fertilised plants followed by the P. mendocina-inoculated plants grown under severe stress conditions. These results support the potential use of a PGPR as an inoculant to alleviate the oxidative damage produced under water stress.

Combined inoculation of arbuscular mycorrhizal fungi, Pseudomonas fluorescens and Trichoderma spp. for enhancing defense enzymes and yield of three pepper cultivars

“…Apparently, the combination of these bacteria with AM decreased significantly the activities of all enzymes in relation with its counterpart in Pse inoculation alone ( Table 5). This observation is in accordance with the report of Kohler et al (2008) that combination of Rhizophagus irregularis or Funneliformis mosseae with Pseudomonas mendocina Palleroni dropped SOD, CAT level in leaves of Lactuca saiva L. under severe drought stress. However, POD activity in our results is in contrast to that of the authors.…”

Biological seed priming mitigates the effects of water stress in sunflower seedlings

“…They suggested that PGPR helped in formation of a biofilm around the roots which enhanced the drought tolerance. According to Kohler et al (2008) inoculation helped maintaining higher level of proline, which served as osmolyte. In our opinion proline might have helped maintaining RWC.…”

“…Oxidative stress generates free radicals and toxic derivatives of O 2 such as singlet oxygen and superoxide anions (Smirnoff 1993) and consequent lipid peroxidation during senescence (Ishida et al 1997). An antioxidative defense system comprising of catalase (CAT), peroxidase (POX) and superoxide dismutase (SOD) has been shown to be activated in response to a variety of oxidative stress (Mǿller et al 2007;Kohler et al 2008). These enzymes play various complementary roles in the concerted cellular defense, such as direct scavenging of reactive oxygen species (ROS) for detoxification of the cell (Rubio et al 2002).…”

Agricultural uses of plant biostimulants

“…A wide variety of microorganisms such as Pseudomonas spp. and Acinetobacter spp., Azospirillum ssp., Bacillus spp., and AMF have been reported to increase uptake of Zn (Kohler et al 2008;Yazdani and Pirdashti 2011), Cu, Mn (Liu et al 2000), Ca, Mg (Giri and Mukerji 2004;Khan 2005), and S (Banerjee et al 2006). (Kohler et al 2008) reported that inoculation with a combination of two different microorganisms, Pseudomonas mendocina and the AMF Glomus intraradices, significantly increased uptake of Fe, Ca, and manganese (Mn) in lettuce (Lactuca sativa).…”