Induction of resistance to spot blotch in Hordeum vulgare L. by exogenous methyl jasmonate

Abstract

Abstract [Objective] The study aims to investigate the differential efficacy of anti-leaf spot in barley (Hordeum vulgare L.) of various concentrations of exogenous methyl jasmonate (MeJA) and understand the underlying mechanisms, thereby providing a foundation for the application of MeJA in controlling barley leaf spot. [Methods] We used ‘Mengpimai 3’ (MP3) seedlings as materials and conducted three different treatments: Inoculating the barley leaves with sterile water without any Bipolaris sorokiniana (the causal agent of the disease), inoculating the barley leaves with sterile water after treatment, and treating the barley leaves with different concentrations (0.5, 1.0, 1.5, 2.0, 2.5 mmol/L) of methyl jasmonate (MeJA) before inoculation with the pathogen. The disease incidence was investigated at the three-leaf stage based on disease index to determine the optimal MeJA concentration. We measured antioxidant enzyme activities, anti-disease-related enzyme activities, malondialdehyde, proline, soluble sugar, and soluble protein contents, and the expression levels of related genes under no inoculating treatment, inoculation treatment, and inoculating + optimal MeJA concentration treatment. [Results] (1) Exogenous application of MeJA enhanced MP3 resistance against spot blotch, particularly at 1.5 mmol/L where there was a significant reduction of 19.03% (P <0.05) in disease index compared with control plants, indicating the most effective induction of resistance. (2) In comparison with inoculating treatment, barley leaves treated with 1.5 mmol/L MeJA exhibited significantly increased activities of superoxide, peroxidase, catalase, chitinase, and β-1,3-glucanas. Additionally, there was a significant decrease in malondialdehyde content as well as proline, soluble sugar, and soluble protein levels. Furthermore, the expression of MeJA-regulated transcription factors and genes encoding disease resistance-related enzymes were significantly upregulated. [Conclusion] Exogenous application of 1.5 mmol/L MeJA enhanced resistance against spot blotch in barley by regulating the activity of disease-related enzymes and the content of osmotic regulatory substances, as well as modulating the expression of genes encoding the disease-resistant enzymes and key transcription factors involved in jasmonic acid signaling pathway.

Keywords

• hordeum vulgare l.
• methyl jasmonate
• spot blotch
• induced resistance
• defense enzymes