Seed biostimulant Bacillus sp. MGW9 improves the salt tolerance of maize during seed germination

Heqin Li,Haiwang Yue,Li Li,Jianhua Wang,Yu Liu,Haiyan Zhang,Xuwen Jiang

doi:10.1186/s13568-021-01237-1

Abstract

Crop performance is seriously affected by high salt concentrations in soils. To develop improved seed pre-sowing treatment technologies, it is crucial to improve the salt tolerance of seed germination. Here, we isolated and identified the strain Bacillus sp. MGW9 and developed the seed biostimulant MGW9. The effects of seed biopriming with the seed biostimulant MGW9 in maize (Zea mays L.) under saline conditions were studied. The results show that the strain Bacillus sp. MGW9 has characteristics such as salt tolerance, nitrogen fixation, phosphorus dissolution, and indole-3-acetic acid production. Seed biopriming with the seed biostimulant MGW9 enhanced the performance of maize during seed germination under salinity stress, improving the germination energy, germination percentage, shoot/seedling length, primary root length, shoot/seedling fresh weight, shoot/seedling dry weight, root fresh weight and root dry weight. Seed biostimulant MGW9 biopriming also alleviated the salinity damage to maize by improving the relative water content, chlorophyll content, proline content, soluble sugar content, root activity, and activities of superoxide dismutase, catalase, peroxidase and ascorbate peroxidase, while decreasing the malondialdehyde content. In particular, the field seedling emergence of maize seeds in saline-alkali soil can be improved by biopriming with the seed biostimulant MGW9. Therefore, maize seed biopriming with the seed biostimulant MGW9 could be an effective approach to overcoming the inhibitory effects of salinity stress and promoting seed germination and seedling growth.

Highlights

Soil salinization is an increasingly serious agricultural problem in the world
The characteristics of the strain MGW9 cultured under the condition of 12% NaCl mainly include the following three aspects: (i) Nitrogen fixation: the strain MGW9 was streaked on nitrogen-free medium and cultured in a dark incubator at 30 °C for 4–6 days, and MGW9 colonies were found on the plate. (ii) Phosphorus dissolution: the transparent circle of MGW9 could be observed on the third day after inoculation in the organic phosphate and inorganic phosphate medium, and the size of the transparent circle tended to be stable until the seventh day
The harmful effects of NaCl on seed germination and seedling emergence are caused by the decrease in water use efficiency and nutrient supplement ability when sodium accumulates in soil and the toxic effects of sodium and chloride ions on plants occur (Parida and Das 2005; Munns and Tester 2008; Deinlein et al 2014; van Zelm et al 2020)

Summary

Introduction

Soil salinization is an increasingly serious agricultural problem in the world. It greatly affects the growth and development of crops, resulting in a significant loss of productivity. Salt stress leads to chloroplast damage, decreased photosynthetic rate and increased photorespiratory rate, accumulation of reactive oxygen species (ROS), decreased enzyme efficiency and activated SOS gene expression (Hoshida et al 2000; Teixeira and Pereira 2007; Zhang et al 2019). Most plants have developed the ability to reduce the negative effects of salinity through the regulation and compartmentalization of ions, synthesis of compatible solutes, induction of antioxidant enzymes, induction of phytohormones, and alteration of photosynthetic pathways (Rojas-Tapias et al 2012)

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