Title: Morphological characterization of the interaction between Diplocarpon rosae and various rose species
Authors: O. Blecherta (a) and T. Debener(b)
Authors affiliation: (a) Federal Centre for Breeding Research on Cultivated Plants, Institute for Ornamental Plant Breeding, Bornkampsweg 31, 22926 Ahrensburg: and (b) University of Hannover Faculty of Horticultural Sciences, Department of Applied Genetics, HerrenhJuser Str 2, D-30419 Hannover, Germany
Published in: Plant Pathology, volumn 54, pages 82-90, (2005).
Abstract: Blackspot, caused by Diplocarpon rosae, is the most severe and ubiquitous disease of garden roses, but information is lacking about genotype-specific forms of resistance and susceptibility of the host. Macro- and microscopic analyses of 34 rose genotypes with a defined monoconidial culture black spot inoculum identified susceptible and resistant rose genotypes and further genotype-specific subdivisions, indicating the presence of partial forms of resistance and different resistance mechanisms. In total, eight interaction types were characterized, five representing compatible (types 1-5) and three representing incompatible interactions (types 6-8). The incompatible interactions were characterized by the lack of any visible fungal structures beneath the cuticle (type 8), single-cell necroses (type 7) or necroses of larger cell clusters (type 6), the latter two types with penetration hyphae and haustoria in epidermal cells.
The following is part of Table 1 from the full paper (the last number in each row is the blackspot rating:
Rosa acicularis CIN 4
R. Arkansana CIN 5
R. Arvensis SYN 3
R. Blanda CIN 3
R. Canina CAN 4
R. Carolina CAR 4
R. Caudata CIN 6
R. Corymbifera CAN 4
R. Foetida PIM 2
R. Foliolosa CAR 3
R. Gallica GAL 6
R. Hugonis PIM 2
R. Jundzillii CAN 6
R. Longicuspis SYN 2
R. Majalis CIN 8
R. Monis CAN 1
R. Moyesii CIN 8
R. Multibracteata CIN 8
R multiflora SYN 7
R. Nitida CAR 8
R. Nutkana CIN 7
R. Obtusifolia CAN 4
R. Omeiensis PIM 8
R. cv. Pariser Charme HT 1
R. Pendulina CIN 5
R. Pisocarpa CIN 5
R. Roxburghii PLA 7
R. Rubiginosa CAN 4
R. Sweginzowii macrocarpa CIN 8
R. Tomentosa CAN 1
R. Villosa CAN 1
R. Virginiana CAR 7
R. Wichurana SYN 7
R. Woodsii CIN 7
All species except R. roxburghii (subgenus Plathyrhodon) belong to the subgenus Rosa. Sections within the subgenus Rosa: CIN, Cinnamomeae; SYN. Synstylae; CAN, Caninae; CAR, Carotinae; PIM, Pimpinellifoliae; HT, cultivar (hybrid tea).
The following is from the results section:
"Results
Interactions between 34 different rose genotypes inoculated with black spot conidia and examined macroscopically after 7 days’ either resulted in the formation of acervuli and were classified as compatible (18 rose genotypes), or resulted in no reproductive structures and were considered to be incompatible (16 genotypes) (Table 1). Based on additional information, such as occurrence of necrotic spots and the microscopic investigation of different hyphal structures, the two reaction types were further subdivided.
The compatible interactions were subdivided into a strongly susceptible group designated as interaction types 1 and 2, and a weakly susceptible group (interaction types 3, 4 and 5). Incompatible interactions were designated as interaction types 6, 7 and 8. The classification was based on three independent inoculation experiments in which no qualitative variation could be observed. Only minor differences in the amount of fungal structures developed over the observation period were observed."
“Compatible” means infected (1 and 2) greatest, (3, 4, and 5) lesser extent.
“Incompatible” means very little (6 or 7) or zero infection (8).