Breeding for resistance to American gooseberry mildew, Sphaerotheca mors-uvae, in the gooseberry (Ribes grossularia)

Strong resistance to American gooseberry mildew (Sphaerotheca mors-uvae) occurred in eight out of ten F₁ progenies from crosses of resistant North American Eugrossularia species with European gooseberry cultivars or seedlings. Bimodal segregations in four of these F₁'s and in one F₁ derived from the wild European Ribes grossularia uva-crispa suggested that each donor carried a major dominant resistance gene. Such a gene, Sph₁ was identified in a first backcross from R. oxyacanthoides. Accessions of R. oxyacanthoides, R. leptanthum and R. watsonianum proved the most promising donors of resistance to mildew and leaf spot (Pseudopeziza ribis).