Functional characterization of nanoparticle-rhizobia interactions in cowpea (Vigna unguiculata L.)
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Date
2018
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Punjab Agricultural University, Ludhiana
Abstract
Analyzing and identifying the positive impact of nanomaterials (NM) on rhizobacteria is quite essential. Extensive research aimed at deciphering the beneficial as well as the ecotoxic aspects of nanoparticle(NP)-soil-plant microbe system interactions under environmental conditions is necessary to pave nano-interventions in agriculture. This study was aimed at understanding the NM-cowpea rhizobia interactions leading to alterations in their functional characteristics. Ninety-three isolates were obtained from the root nodules of nineteen genotypes of cowpea, out of which three best performers viz. CP-11-MAM-N1, CP-13-KK-N3-C1 and CP-VAR4-N1 were selected on the basis of qualitative and quantitative analysis of their functional traits. These were then evaluated for alterations in their growth and functional characteristics on supplementation of YEM broth with pre-determined concentrations of copper nanoparticles (CuNPs), nano-hydroxyapatite (nano-HA) and multi-wall carbon nanotubes (MW-CNT) along with two reference cultures. Maximum increase in growth, protein content and functional traits was reported for CP-VAR4-N1, CP-11-MAM-N1 and Burkholderia seminalis CP-RN-4 isolates with all three NMs. The best working concentrations for the three NMs were deduced i.e., CuNPs (20 μg mL-1), nanoHA (100 μg mL-1) and MWCNT (50 μg mL-1). Further, these cultures also exhibited high exopolysaccharide production compared to their growth in non-NM supplemented broth. The alginate encapsulation of the best NM+Culture/isolate was performed. In hydroponic study, these formulations enhanced vegetative parameters, protein content and root tip viability on inoculation. Maximum increase in these parameters was recorded for alginate-microbead containing CP-11-MAM-N1+CuNPs and nano-HA. Further, a field trial of these nano-biofertilizer formulations with 100% RDF indicated significant improvement in the soil chemical properties, total microbial population, soil enzymatic activities, vegetative growth and yield of cowpea cv. S-263.The total pod yield and pod quality were greatly enhanced with the alginate-microbead encapsulating Burkholderia seminalis CP-RN-4+nano-HA, giving highest protein content (776.79 mg g-1) and pod yield (20.59 t ha-1). Hence, the nano-biofertilizer combinations of CP-11-MAM-N1 and Burkholderia seminalis CP-RN-4 with CuNPs and nano-HA can be implemented for enhancing soil health, plant growth and yield parameters without any eco-nano-toxicity complications.
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