Trehalose induces resistance to powdery mildew in wheat

. Reduction in the degree of powdery mildew infection of wheat leaves is ob served after treatments with trehalose, a nonreducing disaccharide commonly found in a wide variety of organisms, including fungi. . Wheat (Triticum aestivum) cv. Sideral plants grown in phytotrons were ino culated with Blumeria graminis f.sp. tritici. In addition to degree of infe ction, the effect of trehalose solution was further investigated using ligh t and fluorescence microscopy and enzyme assays. . Infection in wheat leaves was reduced by 50 and 95% with trehalose soluti on (15 g l(-1)) following a single spraying and three sprayings, respective ly; in a detached leaf assay, trehalose was effective at concentrations as low as 0.01 g l(-1). Trehalose did not inhibit conidial germination and dif ferentiation of appressoria tin vitro or on the leaf epidermis), but enhanc ed papilla deposition in epidermal cells. Trehalose also enhanced phenylala nine ammonia-lyase (PAL) and peroxidase (PO) activities, both markers of pl ant defence responses. However, the level of three cinnamyl alcohol dehydro genase (CAD) activities (conyferyl, p-coumaryl and sinapyl alcohol dehydrog enase) was unchanged. . Trehalose treatment of wheat confers resistance to B. graminis infection by activating plant defence responses (e.g. papilla deposition, PAL and PO activities).