The Relationship Between Powdery Mildew Resistance Induced By Methyl Jasmonate And The Expression Of Nine Disease Resistance Related Genes In Wheat

Powdery mildew caused by Blumeria graminis (DC.) E.O. Speer f. sp. tritici(Bgt), is one of the most severe wheat (Triticum aestivum L.) diseases in China and manyother countries in the world. Developing resistant varieties is the most economic andeffective way to control this disease. However, powdery mildew isolates mutatefrequently, new isolates often make the resistant cultivars lose their resistance to thedisease. Therefore, investigation on the signal molecules and signaling pathway of wheatresistance may reveal the resistant mechanisms of the host plant, so as to providetheoretical basis for wheat resistance breeding. It can also develop new ways to improvewheat resistance to powdery mildew disease and provide further information for selectionof resistant cultivars to control the outbreak of wheat disease.It is unclear that whether jasmonic acid is a signal molecule for powdery mildewresistance of wheat. In this study, powdery mildew susceptible cultivars"Chinese Spring","Pumai 9"and"Zhoumai 18"were used to study wheat powdery mildew resistanceactivated by methyl jasmonate (MeJA). The reaction types of powdery mildew wereevaluated by detached leaf assay. Real time quantitative RT-PCR was used to determinethe expression patterns of 9 disease resistance related genes of PR1 (PR1.1), PR2 (β,1-3glucanase), PR3 (chitinase), PR4 (wheatwin1), PR5 (thaumatin-like protein), PR9(TaPERO, peroxidase), PR10, TaGLP2a (germin-like) and Ta-JA2 (jasmonate-inducedprotein) in leaves of the three cultivars. The results are as follows.1. The relationship between concentration of MeJA and induced powdery mildewresistance: the results demonstrated that MeJA application enhanced the powdery mildewresistance of"Chinese Spring","Pumai 9"and"Zhoumai 18". The powdery mildewresistance was associated with the concentration of MeJA. The activated powdery mildewresistance was not obvious when induced with MeJA of 100μmol/L or 250μmol/L, but itcould be detected when the concentration of MeJA reached to 500μmol/L, and theresistance was significantly induced by MeJA of above 1.0 mmol/L.2. The relationship between time and powdery mildew resistance induced by MeJA:the induced powdery mildew resistance could be detected from 12 h to 96 h after MeJA treatment, and the top value was at 24 h. MeJA induced wheat powdery mildewresistance has obvious time characteristics.3. The expression of disease resistance related genes induced by MeJA: though therewere differences between the three cultivars, MeJA significantly affect the expression of8 disease resistance related genes except TaGLP2a, and the top values were at 12 h, 24 hor 48 h after treatments. The strongest activation of MeJA was on PR9 and PR1 that theirexpression could reach more than 100 times than untreated samples. MeJA stronglyactivated PR2,PR4,PR5,PR3,PR10 and Ta-JA2, their expression could reach 10 to 70times, and there was almost no activating effect on TaGLP2a.4. The correlation analysis of MeJA induced powdery mildew resistance and theexpressions of disease related genes: the expression of the 8 disease resistance relatedgenes and disease index of 3 wheat cultivars displayed negative correlation, andTaGLP2a displayed positive correlation to disease index. That is to say, TaGLP2a has nocontribution to MeJA induced resistance, expression of the other 8 disease-resistantrelated genes have the varied degree contributions.The induced powdery mildew resistance positively correlated with the inducedexpressions of the disease related genes. Jasmonate signaling plays a role in defenceagainst Blumeria graminis f. sp. tritici. Future manipulation of this pathway may improvepowdery mildew resistance in wheat.