The Relationship Of Jasmonic Acid And Wheat Powdery Mildew Resistance

Abstract:It is unclear that whether jasmonic acid is a signal molecule for powdery mildew resistance in wheat. Now it is a hot item to study signaling in plant disease resistance. In this study, powdery mildew susceptible cultivars "Chinese Spring","Pumai9" and "Zhoumai18" were used to study the relationship of JA pathway with wheat powdery mildew resistance. The induced powdery mildew resistance activated by exogenous methyl jasmonate (MeJA) had been assessed, the concentration fluctuation of JAs in wheat leaves after Bgt infection been quantified by LC/MS (Liquid Chromatography-Mass Spectrometry), and the expression profiles of four disease resistance related genes of PR1(PR1.1), PR2(β,1-3glucanase), PR3(chitinase) and PR4been taken out by real time quantitative RT-PCR. The results are listed as following.1. The relationship between concentration of MeJA and induced powdery mildew resistance. MeJA application enhanced the powdery mildew resistance of "Chinese Spring","Pumai9" and "Zhoumai18". The powdery mildew resistance was associated with the concentration of MeJA. The activated powdery mildew resistance was not obvious when induced with MeJA of100μmol/L or250μmol/L, but it could be detected when the concentration of MeJA reached to500μmol/L, and the resistance was significantly induced by MeJA of above1.0mmol/L.2. The concentration of jasmonic acid in wheat leaves are inceased by Bgt infection. The JAs concentration was increased significantly at30min after pathogen infection (api), reached the top value at3-5h api, then decreased rapidly, and the concentration at96h api was almost the same as that of un-inoculated control. The rapidly increased endogenous JAs in leaves after pathogen infection was consistent with the exogenous MeJA induced powdery mildew resistance. Though there are some difference, the trends of concentration fluctuation of jasmonic acid in different varieties were consistent. Zhoumai18with good field resistance had a relatively higher level accumulation of jasmonic acid than that in more susceptible varieties Chinese spring and Pumai9after Bgt infecion. It is supposed that higher endogenous jasmonic acid (JA) concentration is binifit for keeping higher resistance.3. Exogenous MeJA activated the expressions of four disease resistance related genes. Though there were differences between the three cultivars, MeJA significantly affect the expression of4disease resistance related genes, and the top values were at12h,24h or48h after treatments. The expression profiles of the4PR-genes were negatively related with the disease indexes of the3cultivars, respectively. The ruslts demonstrated that the expression of the4PR-genes contributed to the MeJA induced resistance.4. It is proved that the rapidly increased endogenous JAs in leaves after pathogen infection was consistent with the exogenous MeJA induced powdery mildew resistance. This demonstrated that JAs are the signal molecules in wheat powdery mildew reaction.