AUTHOR=Jalal Arshad , Oliveira Carlos Eduardo da Silva , Bastos Andréa de Castro , Fernandes Guilherme Carlos , de Lima Bruno Horschut , Furlani Junior Enes , de Carvalho Pedro Henrique Gomes , Galindo Fernando Shintate , Gato Isabela Martins Bueno , Teixeira Filho Marcelo Carvalho Minhoto TITLE=Nanozinc and plant growth-promoting bacteria improve biochemical and metabolic attributes of maize in tropical Cerrado JOURNAL=Frontiers in Plant Science VOLUME=13 YEAR=2023 URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.1046642 DOI=10.3389/fpls.2022.1046642 ISSN=1664-462X ABSTRACT=Introduction

Plant growth-promoting bacteria (PGPBs) could be developed as a sustainable strategy to promote plant growth and yield to feed the ever-growing global population with nutritious food. Foliar application of nano-zinc oxide (ZnO) is an environmentally safe strategy that alleviates zinc (Zn) malnutrition by improving biochemical attributes and storage proteins of grain.

Methods

In this context, the current study aimed to investigate the combined effect of seed inoculation with PGPBs and foliar nano-ZnO application on the growth, biochemical attributes, nutrient metabolism, and yield of maize in the tropical savannah of Brazil. The treatments consisted of four PGPB inoculations [i.e., without inoculation, Azospirillum brasilense (A. brasilense), Bacillus subtilis (B. subtilis), Pseudomonas fluorescens (P. fluorescens), which was applied on the seeds] and two doses of Zn (i.e., 0 and 3 kg ha−1, applied from nano-ZnO in two splits on the leaf).

Results

Inoculation of B. subtilis with foliar ZnO application increased shoot dry matter (7.3 and 9.8%) and grain yield (17.1 and 16.7%) in 2019-20 and 2020-2021 crop seasons respectively. Inoculation with A. brasilense increased 100-grains weight by 9.5% in both crop seasons. Shoot Zn accumulation was improved by 30 and 51% with inoculation of P. fluorescens in 2019-20 and 2020-2021 crop seasons. Whereas grain Zn accumulation was improved by 49 and 50.7% with inoculation of B. subtilis and P. fluorescens respectively. In addition, biochemical attributes (chlorophyll a, b and total, carotenoids, total soluble sugar and amino acids) were improved with inoculation of B. subtilis along with foliar nano ZnO application as compared to other treatments. Co-application of P. fluorescens with foliar ZnO improved concentration of grains albumin (20 and 13%) and globulin (39 and 30%). Also, co-application of B. subtilis and foliar ZnO improved concentration of grains glutelin (8.8 and 8.7%) and prolamin (15 and 21%) in first and second seasons.

Discussion

Therefore, inoculation of B. subtilis and P. fluorescens with foliar nano-ZnO application is considered a sustainable and environmentally safe strategy for improving the biochemical, metabolic, nutritional, and productivity attributes of maize in tropical Savannah regions.