Breeding for blackspot resistance background material

Looks like one will have to look at the actual article to see which ones were “best” (“One species and one hybrid were resistant to all pathotypes”). Does anyone have this information?

Title: Resistance of roses to pathotypes of Diplocarpon rosae

Authors: Yokoya K, Kandasamy KI, Walker S, Mandegaran Z, Roberts AV

Published in: ANNALS OF APPLIED BIOLOGY, volumn 136, pages 15-20, (2000)


“Colonies of Diplocarpon rosae derived from single conidia were isolated on malt extract agar, multiplied (at 23 degrees C) and stored (at -20 degrees C) on surface-sterilised leaf discs of a universally susceptible rose, ‘Frensham’. The resistance of 16 species and cultivars of Rosa to different isolates of D. rosae was assessed using surface-sterilised leaf discs. Four pathotypes of D. rosae were distinguished on the basis of host range. One species and one hybrid were resistant to all pathotypes. Two species and two cultivars were susceptible to all pathotypes. Four species and six cultivars were interpreted as having vertical resistance because they were strongly resistant to some but not all pathotypes. Only species and hybrids of the section Cinnamomeae were resistant to the pathotype identified as CW1 whereas only roses of other origins were resistant to the pathotype DA2.”

Title: Identification of molecular markers linked to Rdr1, a gene conferring resistance to blackspot in roses

Authors: von Malek B, Weber WE, Debener T

Published in: THEORETICAL AND APPLIED GENETICS, volumn 101, pages 977-983, (2000).


“Blackspot resistance in the tetraploid rose genotype 91/100-5 had been characterised previously as a single dominant gene in duplex configuration. In the present study a tetraploid progeny (95/3) segregating for the presence of the blackspot resistance gene Rdr1 were screened with 868 RAPD and 114 AFLP primers/primer combinations. Seven AFLP markers were found to be linked to Rdr1 at distances between 1.1 and 7.6 cM. The most closely linked AFLP marker was cloned and converted into a SCAR marker that could be screened in a larger population than the original AFLP and was linked at a distance of 0.76 cM. The cloned fragment was used as an RFLP probe to locate the marker on a chromosome map of diploid roses. This is the first report of markers linked to a resistance gene in roses, and the possibilities of using them for a marker-assisted selection for blackspot resistance as well as for map-based cloning approaches are discussed.”

Title: Resistance to Marssonina rosae in Rosa L. seedlings obtained from controlled crosses including germplasm L83

Author: Carlson-Nilsson BU

Published in: ACTA AGRICULTURAE SCANDINAVICA SECTION B-SOIL AND PLANT SCIENCE, volumn 50, pages 176-182, (2001).


“Blackspot is a serious disease on cultivated roses and resistance is rare; however, some wild Rosa species exhibit a high level of resistance. Disease incidence in field-grown offspring from three seedling families was evaluated as percentage of infected leaves (regardless of the size and number of spots) on each plant. Dolly, Queen Elizabeth and Friesia were used as pistillate parents and the resistant germplasm L83 (derived from the amphidiploid R. X kordesii) was the staminate parent. Assessments were performed during 3 years. Relative tolerance was seen in 71, 54 and 87%, respectively, of the individuals from the three different seedlings families. The infection pattern corresponded well to environmental factors such as precipitation. The importance of timing and duration of assessments over several years, as well as the correlation between blackspot infection and winter hardiness, are discussed.”


Thanks for the information you regularly shares with us all, Mr Kuska.

About blackspot, and after years growing many different roses, I wonder if the “breeding resistant roses” is not simply a bad answer to a good question . I had many “resistant” ones, that did very badly after 5 years without problems. As if the infection “learned” how to catch the place. It’s the same problem as with the antibiotics in medicine.

The other way, I have some Roses known to be very sensible to BS. After some years, the problem tends to vanish.

I’m thus here with some modern “resistant” roses full of BS

and others like “Baron Girod de l’Ain”, “Arthur de Sansal” and others “fragile” roses (Roger Lambellin!) without any problems more.

Best wishes,


Published in: ISHS Acta Horticulturae 547: III International Symposium on Rose Research and Cultivation


Authors: T. Debener, B. von Malek, L. Mattiesch, H. Kaufmann


“A large collection of rose genotypes was screened for resistance to blackspot caused by Diplocarpon rosae. To date 28 genotypes which display a high level of resistance could be identified. In parallel the interaction between blackspot and roses was investigated genetically. After characterising six physiological races a single dominant resistance gene against one of the races was characterised and several closely linked markers were identified.”


Pierre wrote:>

If sprayed and with single clone large plantings (or inbred crops) you are right. Vegetable breeders dot think like you do when a new resistance leads to more virulent desease strains prevalence.

There are several answers to this problem.

First is avoid spraying in order not to favor the more virulent (sneller developing and often more damaging) desease strains.

Another is avoid single clone plantings that allows easier virulent desease strains selection.

A strategy is to plant succeptible vars next to the resistant ones large planting.

Then breed for more steady tolerance factors. Resistance is specific when tolerance is not

as you can see with species and Teas.

Friendly yours

Pierre Rutten

Hello Mister Rutten,

I grow 200 different varieties of roses,and moreover there are other plants as companions.

And I never spray my roses.

According to what you wrote, this could be the reasons why I have very few problems.

But I believe to convince the normal gardeners to change their landscaping habits will be a tough job…

Thanks and best wishes,

Pierre Lauwers.

Where is the problem?

A wellknown showroses guru aggressed me on a forum when I wrote about breeding desease resistant roses a few years ago. He wrote that as I did not wanted to spray I was a poor rose lover and that such roses would be “boring” in his opinion.

Obviously for him Kordes, Meilland or lately Austin are making a big mistake when breeding desease resistant roses.

Evidently such roses will be more appraised by the no spray or reluctant to spray gardeners majority than by such rose experts.


Pierre Rutten

Hello Mr Rutten,

I believe roses shows and collections like mine to be two different worlds.

I would not even mind attend a show with my beautifulest roses.

Thus maybe the breeding process must follow a clear choice between the two from the very start. This is already the case with the distinction made with the roses breed for the cut flower market.

But in this the “Rosiers-paysage” is not sufficient, we must have refined individual flowers too.

Best wishes,

Pierre Lauwers.