Screening of fungal diseases in offspring from crosses between Rosa sections Caninae and Cinnamomeae

Roses constitute one of the most important ornamental plant crops. Recently an increasing interest has been noted also for the fruits; rose hips. Plant breeding of dogroses (section Caninae) is complicated by their unique meiosis with an unequal distribution of chromosomes, which results in strongly matroclinal offspring. Disease resistance was evaluated for blackspot, leaf spot, powdery mildew and rust in 649 field-grown offspring from eleven families. One genotype of Rosa dumalis and two of R. rubiginosa were used as pistillate parents and six selected genotypes derived from open pollination of 'Uralskij Champion' were used as pollinate parents. Blackspot was the most serious disease, followed by leaf spot, whereas powdery mildew and rust were rare. Significant differences between families with different staminate parents were found for blackspot, leaf spot and powdery mildew, indicating the possibility to select for resistance to these diseases in seedlings from crosses involving section Caninae in spite of the Canina meiosis.