Previous work has demonstrated that glycerol-3-phosphate (G3P) and
oleic acid (18:1) are two important signal molecules associated with plant resistance to fungi. In this article, we provide evidence that a 3%
glycerol spray application 1-2 days before powdery mildew
infection and subsequent applications once every 4 days was sufficient to stimulate the plant defense responses without causing any significant damage to wheat leaves. We found that G3P and
oleic acid levels were markedly induced by powdery mildew
infection. In addition, TaGLI1 (encoding a
glycerol kinase) and TaSSI2 (encoding a stearoylacyl
carrier protein fatty acid desaturase), two genes associated with the
glycerol and
fatty acid (FA) pathways, respectively, were induced by powdery mildew
infection, and their promoter regions contain some fungal response elements. Moreover, exogenous application of
glycerol increased the G3P level and decreased the level of
oleic acid (18:1).
Glycerol application induced the expression of pathogenesis-related (PR) genes (TaPR-1, TaPR-2, TaPR-3, TaPR-4, and TaPR-5), induced the generation of
reactive oxygen species (ROS) before powdery mildew
infection, and induced
salicylic acid (SA) accumulation in wheat leaves. Further, we sprayed
glycerol in a wheat field and found that it significantly (p < 0.05) reduced the severity of powdery mildew disease and lessened disease-associated kernel
weight loss, all without causing any noticeable degradation in wheat seed quality.