Seed Bio-priming of wheat with a novel bacterial strain to modulate drought stress in Daegu, South Korea

Abstract

Wheat is one of the major cereal crop grown food worldwide and, therefore, plays has a key role in alleviating the global hunger crisis. The effects of drought stress can reduces crop yields by up to 50% globally. The use of drought-tolerant bacteria for biopriming can improve crop yields by countering the negative effects of drought stress on crop plants. Seed biopriming can reinforce the cellular defense responses to stresses via the stress memory mechanism, that its activates the antioxidant system and induces phytohormone production. In the present study, bacterial strains were isolated from rhizospheric soil taken from around the Artemisia plant at Pohang Beach, located near Daegu, in the South Korea Republic of Korea. Seventy-three isolates were screened for their growth-promoting attributes and biochemical characteristics. Among them, the bacterial strain SH-8 was selected preferred based on its plant growth-promoting bacterial traits, which are as follows: abscisic acid (ABA) concentration = 1.08 ± 0.05 ng/mL, phosphate-solubilizing index = 4.14 ± 0.30, and sucrose production = 0.61 ± 0.13 mg/mL. The novel strain SH-8 demonstrated high tolerance oxidative stress. The antioxidant analysis also showed that SH-8 contained significantly higher levels of catalase (CAT), superoxide dismutase (SOD), and ascorbic peroxidase (APX). The present study also quantified and determined the effects of biopriming wheat (Triticum aestivum) seeds with the novel strain SH-8. SH-8 was highly effective in enhancing the drought tolerance of bioprimed seeds; their drought tolerance and germination potential (GP) were increased by up to 20% and 60%, respectively, compared with those in the control group. The lowest level of impact caused by drought stress and the highest germination potential, seed vigor index (SVI), and germination energy (GE) (90%, 2160, and 80%, respectively), were recorded for seeds bioprimed with with SH-8. These results show that SH-8 enhances drought stress tolerance by up to 20%. Our study suggests that the novel rhizospheric bacterium SH-8 (gene accession number OM535901) is a valuable biostimulant that improves drought stress tolerance in wheat plants and has the potential to be used as a biofertilizer under drought conditions.

Keywords: drought; germination; newly isolated strain; seed biopriming; wheat.

Figure 1

(A) Exopolysaccharide production, (B) phosphate solubilization, (C) siderophore production, and (D) indole acetic acid production by the novel bacterial isolate SH-8.

Figure 2

The phylogenetic tree of Klebsiella aerogenes SH-8 was constructed from 16S rRNA sequences using the ML method with the aid of the MEGA X program.

Figure 3

Abscisic acid and sucrose quantification in SH-8 cultured on Luria–Bertani broth. Each data point is the mean of five replicates. Error bars represent the standard error.

Figure 4

Production of significant amounts of superoxide dismutase (A); catalase (B), and ascorbic peroxidase (C) in the SH-8 culture broth media and cell pellet. Error bars represent the standard error.

Figure 5

Growth of SH-8 with different concentrations of PEG 6000. Each data point is the mean of five replicates. The error bar represents the standard error. Different lowercase letters indicate significant difference in treatment.

Figure 6

Scanning electron microscopy at a different resolution. The arrows indicate the presence of the biofilm and surface characteristics of bacterial isolate SH-8.

Figure 7

Effect of various concentrations of PEG 6000 and biopriming with SH-8 on the seed vigor index, germination rate index, germination energy, and germination potential of wheat seeds. PEG, polyethylene glycol. Different lowercase letters indicate significant difference in treatment.

Figure 8

In vitro seed biopriming with different concentrations of the polyethylene glycol: (A) normal control; (B) microbial pellet; (C) microbial pellet + 5% PEG (D) microbial pellet + 10% PEG; (E) microbial pellet + 15% PEG; (F) microbial pellet + 20% PEG; and (G) microbial solution. PEG, polyethylene glycol.