RESEARCH ON BLACKSPOT PATHOGEN DIPLOCARPON ROSAE (MARSSONINA ROSAE) AND RESISTANCE IN ROSA

Blackspot is the most important rose disease world-wide and affects nearly all existing cultivars. The results often differ because of different races of the fungi and different environmental conditions. Two identical field trials has been established in 1995/96 at one cool and humid site (Balsgärd, Sweden) and one hot and dry (Morden, Canada) to study the influence of genotype and environment on blackspot. The preliminary results demonstrate significant differences between the two sites regarding survival, hardiness and blackspot infection. Morden appears to have a more favourable climate according to the higher survival percentage, while Balsgärd had a better result regarding the hardiness (assessed on a scale 0 to 10). Plants with severe blackspot infection in the summer of 1996 appear to suffer more winter damage during the winter 1996/97.