FUNGUS-RESISTANT ROSES: FACT OR FAKE?

Breeding fungus resistant rose varieties is urgent, but unpopular among breeders. Of three possible strategies to breed genotypes resistant to black spot (Diplocarpon rosae) and mildew (Sphaerotheca pannosa), the use of horizontal resistance from traditional varieties may offer fastest results. In spite of probable good durability of horizontal resistance, plants may be not completely without symptoms, while inbreeding can hardly be circumvented. Therefore, the introduction of resistant germplasm via interspecific crosses may offer better results. Interspecific crosses fit into a long-term strategy. Introduction of resistance genes into existing varieties by genetic modification, may offer broad spectre resistance, but create essentially derived varieties that contain industrially patented genes.