POWDERY MILDEW RESISTANCE IDENTIFICATION OF WILD ROSA GERMPLASMS

Powdery mildew caused by Podosphera pannosa is a major disease of roses causing large amount of losses especially in greenhouse production. To identify the powdery mildew resistance of wild Rosa species for providing resistant genetic resources for rose disease-resistant breeding, we evaluated 50 accessions from nine botanical sections, including nine ancestor species of modern roses and ten endemic species to China, by a spore-suspension inoculation method. With a set of fifty different Rosa genotypes, all five tested isolates from diverse host genotypes could be identified as different races. The results showed that six genotypes R. laevigata, R. longicuspis, R. luciae, R. banksiae and its two varieties were immune to P. pannosa. Twelve accessions of section Pimpinellifoliae, R. rubus, R. rugose, etc. were highly resistant to this pathogen. The results indicated that the three sections Pimpinellifoliae, Laevigatae and Banksianae were obvious more resistant to P. pannosa than others. The immunized and highly resistant species were characterized either by thick and shiny young leaves or by rugose young leaves with prominent veins. The study provides useful information for utilizing these resistant germplasm in rose disease-resistant gene isolation and new cultivar breeding.