ORIGINAL RESEARCH article
Front. Plant Sci.
Sec. Crop and Product Physiology
Volume 16 - 2025 | doi: 10.3389/fpls.2025.1661290
Effects of foliar-sprayed bio-fertilizer with N-fixing Methylobacterium symbioticum on morpho-physiological traits of maize under varying N fertilization rates
Provisionally accepted
Pranay Kumar Bolla1
Anna Panozzo1*
Edoardo Minozzi1Francesco Valente1Silvia Potestio2
Giovanna Visioli2
Isabel Martinez-Sañudo1
Teofilo Vamerali1- 1University of Padua, Padua, Italy
- 2Universita degli Studi di Parma, Parma, Italy
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Nitrogen (N) fertilization remains a critical challenge in sustainable agriculture. Plant growth-promoting bacteria offer a promising strategy to enhance nitrogen use efficiency and improve cereal crop productivity while reducing reliance on synthetic inputs. This open-field study evaluated the morpho-physiological effects of foliar application of Methylobacterium symbioticum (MS) on maize in NE Italy. Following a baseline application of liquid digestate (300 kg N ha⁻¹) to all plots, four treatments were compared: N300 (digestate only, serving as the control); N300 + MS (digestate with MS); N350 (digestate with 50 kg ha⁻¹ chemical N); and N320 + MS (digestate with 20 kg ha⁻¹ chemical N and MS). ESEM imaging confirmed colonization of leaf surfaces by M. symbioticum. Its application significantly promoted aboveground growth and delayed leaf senescence by improving chlorophyll retention, increasing seasonal average SPAD from 46.9 in control to 49.4 (+5.3%, N300 + MS) and 48.8 (+4.1%, N320 + MS), likely mediated by the ascertained ACC-deaminase activity of MS. Root electrical capacitance showed treatment-specific effects, with the highest readings under the N320 + MS treatment (+54% vs. control at flowering). Yield responses were non-linear with respect to N dose, with N300 + MS showing a 12% (1,364 g/m²) and N320 + MS a 6% nonsignificant increase vs. control. MS-treated plants also exhibited a non-significant 5% increase in grain protein content, but significantly higher aboveground N accumulation. It is concluded that, this microbial inoculation strategy can enhance N use efficiency, particularly under reduced synthetic fertilization, presenting an environmentally-friendly and sustainable agricultural strategy for maize cultivation.
Keywords: ACC deaminase, nitrogen fertilization, grain yield and quality, Leaf stay-green, Rootelectrical capacitance, Plant growth promoting bacteria (PGPB)
Received: 07 Jul 2025; Accepted: 19 Aug 2025.
Copyright: © 2025 Bolla, Panozzo, Minozzi, Valente, Potestio, Visioli, Martinez-Sañudo and Vamerali. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Anna Panozzo, University of Padua, Padua, Italy
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