Heterologous expression of genes mediating enhanced fungal resistance in transgenic wheat

Three cDNAs encoding the antifungal protein Ag-AFP from the fungus Aspergil lus giganteus, a barley class II chitinase and a barley type I RIP, all reg ulated by the constitutive Ubiquitin1 promoter from maize, were expressed i n transgenic wheat. In 17 wheat lines, stable integration and inheritance o f one of the three transgenes has been demonstrated over four generations. The formation of powdery mildew (Erysiphe graminis f. sp, tritici) or leaf rust (Puccinia recondita f. sp, tritici) colonies was significantly reduced on leaves from afp or chitinase II- but not from rip I-expressing wheat li nes compared with nontransgenic controls. The increased resistance of afp a nd chitinase II lines was dependent on the dose of fungal spores used for i noculation. Heterologous expression of the fungal afp gene and the barley c hitinase II gene in wheat demonstrated that colony formation and, thereby, spreading of two important biotrophic fungal diseases is inhibited approxim ately 40 to 50% at an inoculum density of 80 to 100 spores per cm(2).