Assessment of the plant growth promotion abilities of six bacterial isolates using Zea mays as indicator plant

Abstract

Zea mays, one of the most important cereals worldwide, is a plant not only with food and energy value, but also with phytoremediation potential. The use of plant growth promoting (PGP) rhizobacteria may constitute a biological alternative to increase crop yield and plant resistance to degraded environments. In search for PGP rhizobacteria strains, 6 bacterial isolates were isolated from a metal contaminated site, screened in vitro for their PGP characteristics and their effects on the growth of Z. mays were assessed. Isolates were identified as 3A10 T , ECP37 T , corresponding to Chryseobacterium palustre and Chryseobacterium humi, and 1ZP4, EC15, EC30 and 1C2, corresponding to strains within the genera Sphingobacterium, Bacillus, Achromobacter, and Ralstonia, respectively. All the bacterial isolates were shown to produce indole acetic acid, hydrogen cyanide and ammonia when tested in vitro for their plant growth promoting abilities, but only isolates 1C2, 1ZP4 and ECP37 T have shown siderophore production. Their further application in a greenhouse experiment using Z. mays indicated that plant traits such as root and shoot elongation and biomass production, and nutrient status, namely N and P levels, were influenced by the inoculation, with plants inoculated with 1C2 generally outperforming the other treatments. Two other bacterial isolates, 1ZP4 and ECP37 T also led to increased plant growth in the greenhouse. These 3 species, corresponding to strains within the genera Ralstonia (1C2), Sphingobacterium (1ZP4), and to a strain identified as C. humi (ECP37 T) can thus be potential agents to increase crop yield in maize plants.

Rhizobacteria isolated from a metal-polluted area enhance plant growth in zinc and cadmium-contaminated soil

“…In this study, several isolates (1AP2, EC 34, 3ZP2 and EC 10) with high ability to produce IAA promoted white clover root biomass which suggests a relation between both parameters. There results were corroborated by Marques et al (2010) who reported a positive correlation between IAA-producing rhizobacteria and Zea mays root biomass promotion and by Khalid et al (2004) who showed that bacterial strains which produced the highest amount of IAA also increased growth of wheat. Promotion of root growth is one of the major markers by which the beneficial effect of PGPR is measured (Glick et al 1995).…”

“…Ammonia production is another common trait in tested rhizobacteria (Table 1). NH 3 production by bacterial isolates may enhance plant growth, which was also seen by Marques et al (2010) that demonstrated a positive correlation between bacterial ammonia production and root and shoot elongation of Zea mays plants. Only 2 strains (ECX16 and 3C5) belonging to Arthrobacter genus showed ability to solubilize phosphate.…”

“…Several studies demonstrated that siderophore-producing rhizobacteria improve plant growth by increasing iron availability to plants or by limiting iron for phytopathogenic organisms (Sahu and Sindhu 2011). Marques et al (2010) showed that bacterial siderophore production influenced plant traits, evidencing positive correlations with nutrients assimilation (N and P) and Z. mays growth. Hydrogen cyanide production is another possible way by which rhizobacteria may suppress plant pathogens.…”

Impact of Pseudomonas aeruginosa MAJ PIA03 affecting the growth and phytonutrient production of castor, a primary host-plant of Samia ricini

“…reproduced under field, semi-field or even greenhouse conditions as the interaction between the associative PGPR and plants could be unstable (Marques et al, 2010;Zhender et al, 1999 et al, 2000).…”

“…Pseudomonads also play a decisive role in plant growth promotion through reduction of ethylene production by synthesizing 1-aminocyclopropane-1-carboxylate (ACC) deaminase. The ACC deaminase enzyme modulates the level of ethylene by hydrolyzing ACC in ammonia and α-ketobutyrate (Marques et al, 2010). Pseudomonas fluorescens strain Psd solubilizes inorganic zinc and produces nitrate reductase along with certain antioxidant enzymes such as glutathione reductase and peroxidase which eventually supports the growth of wheat (Sirohi et al, 2015).…”