外源茉莉酸甲酯诱导大麦叶斑病抗性研究

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

【目的】探讨不同浓度外源茉莉酸甲酯(MeJA)诱导大麦抗叶斑病效应差异及其分子机制,为应用MeJA防治大麦叶斑病提供理论依据。【方法】以‘蒙啤麦3号’大麦品种幼苗为材料,设置不接菌(无菌水处理叶片)、接菌(无菌水处理叶片接种麦根腐平脐蠕孢菌)和接菌+MeJA(0.5,1.0,1.5,2.0,2.5mmol/LMeJA喷施叶片后接菌)3组处理,于三叶期调查叶斑病发病情况,并据此筛选最适MeJA浓度,然后测定不接菌、接菌及接菌+MeJA(最适浓度)下不同处理时间叶片的抗氧化酶、抗病相关酶活性、丙二醛含量、渗透调节物质含量以及相关基因表达水平。【结果】(1)叶面喷施外源MeJA提高了大麦对叶斑病的抗性,1.5mmol/LMeJA处理叶片的病情指数较对照显著降低19.03%,诱导抗性效果最佳;(2)与单独接菌处理相比,1.5mmol/LMeJA处理大麦叶片超氧化物歧化酶、过氧化物酶、过氧化氢酶、几丁质酶和β-1,3-葡聚糖酶活性均显著提高,而其丙二醛、脯氨酸、可溶性糖和可溶性蛋白含量显著降低,同时受MeJA调控转录因子及编码抗病相关酶的基因表达量显著上调。【结论】外源喷施1.5mmol/LMeJA通过调节抗病相关酶活性和渗透调节物质含量,以及调控抗病相关酶基因及茉莉酸信号途径关键转录因子基因表达,进而提高大麦植株的叶斑病抗性。

[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 bar-ley leaf spot.[Methods]We used‘Mengpimai 3’(MP3)seedlings as materials and conducted three differ-ent 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 en-zyme activities,anti-disease-related enzyme activities,malondialdehyde,proline,soluble sugar,and solu-ble 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 sig-nificant 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,andβ-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.