Hydropriming and Osmotic Priming Induce Resistance against Aspergillus niger in Wheat (Triticum aestivum L.) by Activating β-1, 3-glucanase, Chitinase, and Thaumatin-like Protein Genes

Abstract

Priming is used as a method to improve plant growth and alleviate the detrimental effects of pathogens. The present study was conducted to evaluate the effects of different priming methods in the context of resistance to Aspergillus niger in wheat (Triticum aestivum L.). Here, we show that different priming treatments—viz., hydropriming, osmotic priming, halopriming, and hormonal priming techniques can induce disease resistance by improving the biochemical contents of wheat, including chlorophyll, protein, proline, and sugar. In addition, physiological parameters—such as root length, shoot length, fresh and dry root/shoot ratios, and relative water content were positively affected by these priming methods. In essence, hydropriming and osmotic priming treatments were found to be more potent for enhancing wheat biochemical contents, along with all the physiological parameters, and for reducing disease severity. Hydropriming and osmotic priming significantly decreased disease severity, by 70.59−75.00% and 64.71−88.33%, respectively. RT-PCR and quantitative real-time PCR analyses of potentially important pathogenesis-related (PR)-protein genes (Thaumatin-like protein (TLP), chitinase, and β-1,3-glucanase) in primed plants were evaluated: β-1,3-glucanase was most highly expressed in all primed plants; Chitinase and TLP exhibited higher expression in hormonal-, halo-, osmotic-, and hydro-primed plants, respectively. These results suggest that the higher expression of β-1,3-glucanase, TLP, and chitinase after hydropriming and osmotic priming may increase disease resistance in wheat. Our study demonstrates the greater potential of hydropriming and osmotic priming for alleviating stress caused by A. niger inoculation, and enhancing resistance to it, in addition to significantly improving plant growth. Thus, these priming methods could be beneficial for better plant growth and disease resistance in other plants.

Keywords: Aspergillus niger; TLP; chitinase; priming; qRT-PCR; wheat; wilting; β-1,3-glucanase.

Figure 1

Biochemical contents of wheat under hydropriming, osmotic priming, halopriming, and hormonal priming: (A) proline content, (B) protein content, (C) sugar content, (D) chlorophyll content. The mean values with different letter(s) indicate significant differences at p ≤ 0.05. Vertical bars represent standard deviation of means (n = 3). Sys. inoculation: Systemic inoculation.

Figure 2

Physiological parameters of wheat under hydropriming, osmotic priming, halopriming, and hormonal priming: (A) relative water content (RWC); (B) shoot length; (C) root length; (D) fresh root/shoot ratio; (E) dry root/shoot ratio. The mean values with different letter(s) indicate significant differences at p ≤ 0.05. Vertical bars represent standard deviation of means (n = 3). Sys. inoculation: Systemic inoculation.

Figure 3

Effects of different priming methods on the growth of wheat plants. (A) (I): control; (II): hydropriming; (III): osmotic priming; (IV): halopriming, (V): hormonal priming. (B) Disease severity after foliar inoculation. (I): control vs. hydropriming; (II): control vs. osmotic priming; (III): control vs. halopriming; (IV): control vs. hormonal priming. (C) Disease severity after systemic inoculation. (I): control vs. hydropriming; (II): control vs. osmotic priming; (III): control vs. halopriming; (IV): control vs. hormonal priming.

Figure 4

Disease severity analysis of wheat plants in response to hydropriming, osmotic priming, halopriming, and hormonal priming. (A) Disease severity analysis after foliar inoculation of A. niger. (B) Disease severity analysis after systemic inoculation of A. niger. (C) Disease severity comparison between foliar and systemic inoculation. The mean values with different letter(s) indicate significant differences at p ≤ 0.05. Vertical bars represent standard deviation of means (n = 3).

Figure 5

Measurement of disease severity after foliar and systemic inoculation, by visual assessment of wilting. Different wilting conditions are described as normal (N), slightly wilted (SlW), wilted (W), severely wilted (SeW), nearly dead (ND), and dead (D).

Figure 6

Expression profiling of TLP, Chitinase, and β-1, 3-glucanase by RT-PCR.

Figure 7

Relative expression of TLP, Chitinase, and β-1,3-glucanase, obtained through quantitative real-time PCR analysis. The mean values with different letter(s) indicate significant differences at p ≤ 0.05. Vertical bars represent standard deviation of means (n = 3).