Alleviation of drought stress in pulse crops with acc deaminase producing rhizobacteria isolated from acidic soil of northeast india

The agricultural crops are often affected by the scarcity of fresh water. Seasonal drought is a major constraint on Northeast Indian agriculture. Almost 80% of the agricultural land in this region is acidic and facing severe drought during the winter period. Apart from classical breeding and transgenic approaches, the application of plant-growth-promoting bacteria (PGPB) is an alternative strategy for improving plant fitness under stressful conditions. The 1-aminocyclopropane-1-carboxylate (ACC) deaminase-producing PGPB offer drought stress tolerance by regulating plant ethylene levels. The aim of the present study was to evaluate the consortium effect of three ACC-deaminase producing rhizobacteria - Ochrobactrum pseudogrignonenseRJ12, Pseudomonas sp.RJ15 and Bacillus subtilisRJ46 on drought stress alleviation in Vigna mungo L. and Pisum sativum L. Consortium treatment significantly increase seed germination percentage, root length, shoot length, and dry weight of treated plants. An elevated production of reactive oxygen species scavenging enzymes and cellular osmolytes; higher leaf chlorophyll content; increase in relative water content and root recovery intension were observed after consortium treatment in comparison with the uninoculated plants under drought conditions. The consortium treatment decreased the ACC accumulation and down-regulated ACC-oxidase gene expression. This consortium could be an effective bio-formulator for crop health improvement in drought-affected acidic agricultural fields

Community Profiling of Culturable Fluorescent Pseudomonads in the Rhizosphere of Green Gram (<i>Vigna radiata</i> L.)

<div><p>Study on microbial diversity in the unexplored rhizosphere is important to understand their community structure, biology and ecological interaction with the host plant. This research assessed the genetic and functional diversity of fluorescent pseudomonads [FP] in the green gram rhizophere. One hundred and twenty types of morphologically distinct fluorescent pseudomonads were isolated during vegetative as well as reproductive growth phase of green gram. Rep PCR, ARDRA and RISA revealed two distinct clusters in each case at 75, 61 and 70% similarity coefficient index respectively. <i>16S rRNA</i> partial sequencing analysis of 85 distantly related fluorescent pseudomonads depicted <i>Pseudomonas aeruginosa</i> as the dominant group. Out of 120 isolates, 23 (19%) showed antagonistic activity towards phytopathogenic fungi. These bacterial isolates showed varied production of salicylic acid, HCN and chitinase, 2, 4-diacetylphloroglucinol (DAPG), phenazine-1-carboxylic acid (PCA) and pyoluteorin (PLT). Production efficiency of inherent level of plant growth promoting (PGP) traits among the 120 isolates demonstrated that 10 (8%) solubilised inorganic phosphates, 25 (20%) produced indoles and 5 (4%) retained ACC deaminase activity. <i>Pseudomonas aeruginosa</i> GGRJ21 showed the highest production of all antagonistic and plant growth promoting (PGP) traits. In a greenhouse experiment, GGRJ21 suppressed root rot disease of green gram by 28–93% (p = 0.05). Consistent up regulation of three important stress responsive genes, i.e., <i>acdS</i>, <i>KatA</i> and <i>gbsA</i> and elevated production efficiency of different PGP traits could promote GGRJ21 as a potent plant growth regulator.</p></div

Phylogenetic analyses of fluorescent pseudomonads based on the nucleotide sequence of <i>16S rRNA</i>.

<p>The multiple sequence alignment was done in CLUSTALW program embedded in MEGA version 5.10. The pair-wise evolutionary distances were calculated using Kimura-2 parameter model. The phylogenetic tree was constructed by Neighbor-Joining (NJ) method with 1000 replicates using bootstrap. A total of 5 reference fluorescent pseudomonad strains were used for the tree construction. Bar, .0.005 shows the substitutions per nucleotide position.</p

Antagonostic activity of fluorescent pseudomonads against phytopathogenic fungi. Activity was monitored on the basis of inhibition zone.

<p>Means within a column sharing same superscript are not significantly different according to Turkey’s test at p = 0.05; ± means standard deviation (SD) and - means no activity.</p><p>Antagonostic activity of fluorescent pseudomonads against phytopathogenic fungi. Activity was monitored on the basis of inhibition zone.</p

Effect of <i>Pseudomonas aeruginosa</i> GGRJ21 on root rot disease suppression of green gram during infection with <i>Rhizoctonia solani</i>.

<p>Means within a column sharing same superscript are not significantly different according to Turkey’s test at p = 0.05; ± means standard deviation (SD).</p><p>Effect of <i>Pseudomonas aeruginosa</i> GGRJ21 on root rot disease suppression of green gram during infection with <i>Rhizoctonia solani</i>.</p

Primers for real time PCR: sequences, final concentration, product size, T_m and Efficiency of PCR amplification.

<p>T_m means melting temperature; ±SD means standard deviation of the mean value.</p><p>Primers for real time PCR: sequences, final concentration, product size, T_m and Efficiency of PCR amplification.</p

Relative gene expression level of, a) <i>acdS</i>, b) <i>katA</i> and c) <i>gbsA</i> in <i>P</i>. <i>aeruginosa</i> (GGRJ21) growing in different osmotic stress condition.

<p>A-GGRJ 21 grown in normal NB medium, B-GGRJ21 grown in –0.3<b> </b>mPA, C-GGRJ21 grown in 0.49<b> </b>mPA and D-GGRJ21 grown in –0.73<b> </b>mPA.</p