Exogenous Trehalose Induces Defenses in Wheat Before and During a Biotic Stress Caused by Powdery Mildew

Tayeh, C., Randoux, B., Vincent, D., Bourdon, N., and Reignault, P. 2014. Exogenous trehaloseinduces defenses in wheat before and during a biotic stresscaused by powdery mildew. Phytopathology 104:293-305. Powdery mildewwould be one of the most damaging wheat diseaseswithout the extensive use of conventional fungicides. Some of the alternative control strategies currently emerging are based on the use of resistance inducers. The disacharride trehalose(TR) is classically described as an inducer of defenses in plants to abiotic stress. In this work, the elicitoror priming effect of TR was investigated in wheat both before and during a compatible wheat– powdery mildewinteraction through molecular, biochemical, and cytological approaches. In noninoculated conditions, TR elicited the expression of genes encoding chitinase(chi, chi1, and chi4 precursor), pathogenesis-related protein1, as well as oxalate oxidase(oxo). Moreover, lipid metabolism was shown to be altered by TR spraying via the upregulation of lipoxygenase (lox) and lipid-transfer protein (ltp)encoding gene expression. On the other hand, the protection conferred by TR to wheat against powdery mildewis associated with the induction of two specific defense markers. Indeed, in infectious conditions following TR spraying, upregulations of chi4 precursor and lox gene expression as well as an induction of the LOX activity were observed. These results are also discussed with regard to the impact of TR on the fungal infectious process, which was shown to be stopped at the appressorial germ tubestage. Our findings strongly suggest that TR is a true inducer of wheat defense and resistance, at least toward powdery mildew.