Non-pathogenic Staphylococcus strains augmented the maize growth through oxidative stress management and nutrient supply under induced salt stress

Shahid Masood Shah,Muhammad Shahid,Muhammad Rizwan Javed,Muhammad Tariq Javed,Temoor Ahmed,Muhammad Tahir,Muhammad Noman

doi:10.1007/s13213-019-01464-9

Abstract

The present study was conducted to elucidate the role of phytobeneficial bacteria to control the cellular oxidative damage in maize (Zea mays L.) plants caused by salinity. Bacteria were isolated from the rhizosphere of kallar grass (Leptochloa fusca L.) through serial dilution method and taxonomically identified on the basis of their 16S ribosomal RNA gene sequencing. In vitro phosphate solubilization, indole-3-acetic acid (IAA) synthesis, and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity were evaluated by solubilization index measurement, colorimetric method, and turbidity assay, respectively. In the pot experiment, the impact of single and mixed inoculation of these strains at four levels (0, 50, 100, and 200 mM) of salt stress was evaluated in terms of growth and physiological response of maize plants to salinity. The bacterial strains (STN-1, STN-5, and STN-14) were taxonomically classified as Staphylococcus spp. At 5% NaCl level, the strains demonstrated substantial potential for phosphate solubilization, ACC deaminase activity, and IAA production both with and without tryptophan. The inoculation of strains STN-1, STN-5, and mixed inoculation resulted in substantial growth improvement of maize plants along with increased antioxidant enzyme activity and decreased levels of reactive oxygen species. In addition, single inoculation of STN-1 and STN-5 along with mixed inoculation augmented the uptake of N, P, K, and Ca+2 and reduced Na+ uptake. Current results demonstrated that the strains STN-1 and STN-5 modulated stress-responsive mechanisms and regulated ion balance in induced salinity to promote maize growth.

Highlights

Salinity is a worldwide issue with devastating impacts on soil health and crop production (Shahbaz and Ashraf 2013)
The strains STN-1, STN-5, and STN-14 were taxonomically identified as Staphylococcus spp. on the basis of BLASTn and phylogenetic analysis of their 16S rRNA gene sequence analysis (Table 2, Fig. 1)
Bacterial ACC deaminase activity synthesis is a characteristic with utmost importance in stress tolerance induction in plants when bacteria is in association with roots or aerial parts due to cleavage of ACC into α-ketobutyrate and ammonia in plant cells by the activity of this enzyme (Glick 2014; Mahmood et al 2017)

Summary

Introduction

Salinity is a worldwide issue with devastating impacts on soil health and crop production (Shahbaz and Ashraf 2013). Pakistan is located in the ecological zone where rates of evapotranspiration are high causing the salinity problem (Zafar et al 2016). Salinity causes ion toxicity in plants due to the increased concentration of Na+ and Cl− in the root zone. Under such conditions, plants are subjected to cellular oxidative stress which is harmful for its survival and sustainability (Mayak et al 2004). Plants are subjected to cellular oxidative stress which is harmful for its survival and sustainability (Mayak et al 2004) Such stressful conditions initiate the cellular ion imbalance and synthesis of harmful molecules in plants

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Discussion

Conclusion