Abstract
Seed inoculation with microbial cells is one of the potential invigouration techniques for enhancing the emergence and growth of plants. Herein, we approached a new localized delivery of beneficial microbial cells (Methylobacterium) by invigorating seeds with electrospun Polyvinyl alcohol (PVA) nanofibre containing microbial cells. Methylobacterium is a growth promoting bacteria that has recently drawn attention in agriculture, particularly for drought management. PVA was used in this research because of its electrospinnability and biodegradability. Encapsulation study shows effective immobilization of bacteria cells (Methylorubrum aminovorans) in PVA nanofibre. SEM and TEM characterization further confirmed the entrapment of microbial cells. The microbial plating enumeration reveals 6.6 × 105 CFU g−1 of nanofibre to the initial loading population of 1 × 108 CFU. Viability of nanofibre encapsulated bacterial cells under ambient environment found 1.85 × 105 CFU g−1, 2.2 × 104 CFU g−1 and 1.2 × 104 CFU g−1 on 10, 20 and 30 days after storage, respectively. In vitro bio-efficacy study exhibits that the seeds coated by PVA nanofibres containing M. aminovorans recorded higher germination, root & shoot length, seedling vigor, drymatter production, plant biomass, plant root volume, nodule numbers and fresh weight of nodules. The study concludes that microbial cells could be immobilized in electrospun nanofibre for extended shelf-life of microbial cells and as an effective seed coating for localized delivery.
Highlights
Plant growth promoting beneficial soil bacteria that cause a positive effect on plants through direct and indirect mechanisms
We focused to entrap Methylotrophs, they are gram negative bacteria belonging to the genus Methylobacterium capable of colonize nodules and other plant tissue by using their ability to utilize single carbon substrates as a competitive advantage (Sy et al 2005), fixing nitrogen, improving germination and growth (Meenakumari and Shehkar, 2012) by producing plant growth regulators like zeatin, cytokinins and auxins (Ivanova et al 2005), seed inoculation with this microbial cells improves germination and growth even under limited water availability
And physically pure seeds of groundnut variety TMV13, Polyvinyl alcohol (PVA) having molecular weight of 1,15,000 g/mole purchased from M/s
Summary
Plant growth promoting beneficial soil bacteria that cause a positive effect on plants through direct and indirect mechanisms. Nanofibers technology are currently practiced for seed treatment with chemical/biological substances/microbes encapsulation that improve seedling establishment and promote plant growth. Electrospinning is an advanced technology wherein liquid polymer is converted as fibre ranges from few nano to micro meter in diameter with high surface area when exposed to high voltage current (Li and Xia 2004; Bhardwaj and Kundu 2010; Sullivan et al 2014). E-spun fibre has been investigated as effective seed coating for localized and targeted delivery of inputs for improving germination and seedling growth of rice (Castaneda et al 2014), black gram (Raja et al 2020) and groundnut (Raja et al 2020; Raja et al 2017), and for pathogen control in soyabean (Farias et al 2019). The formation of fibre from polymer in electrospinning depends on various properties on various properties like solution parameters, solvent composition, and processing conditions (Yadav et al 2019)
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