Induction of Hypersensitive Response to a Compatible Race of Phytophthora infestans by Pre-treatment of Potato Leaves with DNA Extracted from a Resistant Cultivar

Abstract

Hypersensitive flecks were induced by a compatible race of Phytophthora infestestans on the leaves of potato cultivar Irish Cobbler (gene r) which had been rubbed with nuclear DNA from a resistant hybrid (cv. Greta, R₁R₃R₄ genes) prior to inoculation. The hybrid nuclear DNA combined with propidiumiodide (PI) or 4'-6-diamidinophenylindole (DAPI) was taken up into potato cell nuclei 1 hr after rubbing on the epidermis, while chloroplast DNA was not incorporated into nuclei. DNA of molecular weight range 1, 750-2, 550kd separated by electrophoresis had ability to induce fleck formation. In order to know the size of DNA required for inducing fleck response against compatible race DNA was treated with restriction enzymes, EcoRI, SalI and/or KpnI. The EcoRI-SalI-treated DNA induced hypersensitive flecks and the EcoRI-KpnI-treated one did not.