Title: Interactions of four pathotypes of Diplocarpon rosae with species and hybrids of Rosa
Authors: Allum, J. F.; Bringloe, D. H.; Roberts, A. V.
Authors affiliation: School of Health and Bioscience, University of East London, Romford Road, London E15 4LZ, UK
Published in: Plant Pathology, Volume 59, issue 3 (June 2010), pages 516-522.
Abstract: "The interactions of four pathotypes of Diplocarpon rosae with 34 species and hybrids of Rosa were compared in an ongoing search for criteria of potential relevance to rose breeding. There were greater similarities in the resistance-susceptibility interactions of these roses to the pathotypes DA1, CW1 and ZM1, than to a fourth pathotype, DA2. Among the species roses, only those of the section Cinnamomeae were susceptible to DA2 and this susceptibility was transmitted in several cases to hybrid progeny. CW1 had the greatest pathogenicity of the four pathotypes. In a cross between R. rugosa cv. Scabrosa, which was resistant and R. rugosa f. alba, which was susceptible to all pathotypes, the progeny were tested for resistance to pathotypes DA1, CW1 and ZM1. Each of the 20 progeny was susceptible to all three pathotypes. This shows that, unlike the well characterized Rdr1 gene for resistance to D. rosae, the resistance of R. rugosa cv. Scabrosa is not determined by a dominant major gene. The diploid hybrid, R. rugosa cv. Martin Frobisher
I will have to get to the library to read this whole thing. But from the abstract it suggest that you should not throw away first generation crosses until you first try to back cross or grow out open pollinated seed just because of black spot. Because the resistance maybe recessive.
How do you think R. rugosa cv. Martin Frobisher
Ive always felt like the disease resistance in rugosas could be partially mechanical rather than based solely on genetic resistance. In other words, I wonder how much the actual cells, their structure and how rigid and thick they harden applies in terms of disease resistance. So, what happens when this component is changed in rugosas and their hybrids? And how different was the MF x MQ induced hybrid from the original in terms of pure mechanics?
In the article linked below they studied different ways of reaction to blackspot by rose species. Interaction type 8 showed no penetration of the cuticle by fungal structures. This could mean the cuticle was resisting penetration mechanically. Other interaction types showed penetration, but the growth of the fungus was stopped by epidermal cells dying off (self-destruct) or other means.
Species with interaction type 8 to the specific strain tested were: R. majalis, R. moyesii, R. multibracteata, R. nitida, R. omeiensis and R. sweginzowii marcocarpa.
R. rugosa was not tested.
Rob
Link: www3.interscience.wiley.com/journal/118688206/abstract?CRETRY=1&SRETRY=0
So how exactly do they isolate different strains of black spot, store it for future use, and what is the best way to infect leaves? How feasible would it be for somebody at home to do this? I have been wondering for a while how one could do this. I have virtually no blackspot to speak of here but I still would like to test for it? Granted I would have to get some blackspot but I do not know how the best way to do things would be. Any ideas?