Diazotrophic diversity in the rhizosphere of two exotic weed plants, Prosopis juliflora and Parthenium hysterophorus

Abstract

This study is aimed at assessing culturable diazotrophic bacterial diversity in the rhizosphere of Prosopis juliflora and Parthenium hysterophorus, which grow profusely in nutritionally-poor soils and environmentally-stress conditions so as to identify some novel strains for bioinoculant technology. Diazotrophic isolates from Prosopis and Parthenium rhizosphere were characterized for nitrogenase activity by Acetylene Reduction Assay (ARA) and 16S rRNA gene sequencing. Further, the culture-independent quantitative PCR (qPCR) was performed to compare the abundance of diazotrophs in rhizosphere with bulk soils. The proportion of diazotrophs in total heterotrophs was higher in rhizosphere than bulk soils and 32 putative diazotrophs from rhizosphere of two plants were identified by nifH gene amplification. The ARA activity of the isolates ranged from 40 to 95 nmol ethylene h(-1) mg protein(-1). The 16S rRNA gene analysis identified the isolates to be members of alpha, beta and gamma Proteobacteria and firmicutes. The qPCR assay also confirmed that abundance of nif gene in rhizosphere of these two plants was 10-fold higher than bulk soil.

Molecular Profiling of Rhizosphere Bacterial Communities Associated with Prosopis juliflora and Parthenium hysterophorus

“…Hence, it is hypothesized that the rhizosphere of these two plants should also harbor some novel bacterial communities in their rhizosphere with adaptability to severe drought, high salinity, and nutritionally poor conditions. In our earlier study, we have demonstrated the diversity potential of rhizosphere soils of Prosopis and Parthenium in terms of diazotrophic bacterial communities [10].…”

A review on weeds as source of novel plant growth promoting microbes for crop improvement

“…Many rhizospheric and endophytic bacteria are reported to have antagonistic activity against a variety of plant pathogens. Cibichakravarthy et al (2011) reported that Bacillus subtilis isolated from the Parthenium rhizosphere has the ability to suppress the plant pathogens such as Macrophomina phaseolina, Sclerotium rolfsi, Lasiodiplodia theobromae, Colletotrichum gloeosporioides and Alternaria solani.…”

“…In another study, the isolates of Parthenium (B. subtilis, Azospirillum sp., A. brasilense and Bacillus sp.) has the ability to solubilise the minerals such as phosphorus, potassium and zinc (Cibichakravarthy et al, 2011).…”

“…Rhizosphere bacteria of weedy grass (Brachiaria reptans, Cenchrus glaucus, Saccharum spontaneum, Panicum repens, Cyperus rotundus, Dactyloctenium aegyptium, Chloris barbata, Cyanodon dactylon and Setaria verticillata) was able to produce under invitro conditions . Cibichakravarthy et al (2011) mentioned that A. brasilense from Prosopis julifera was able to produce the siderophore.…”

“…Plant growth promoting rhizobacterial isolates from the rhizosphere of two arid weed plants prosopis julifera and parthenium hysterophorus were evaluated in aerobic rice (PMK 3). The elite strains showing multifaceted beneficial activities including nitrogen fixation, mineral solubilisation, phytohormaone production, against soil pathogens were inoculated to aerobic rice Cibichakravarthy et al (2011) …”