The fungus Diplocarpon rosae (anamorph = Marssonina rosae Lind.) is the causal organism of rose black spot, which is the most damaging disease of rose worldwide (Dobbs, 1984). Symptoms include lesions on leaves and stems as well as frequent leaf yellowing and defoliation that significantly compromise plant growth and appearance. Consequently, numerous topical and systemic fungicides are used by homeowners and landscapers to combat this disease. Diplocarpon rosae is classified as an ascomycete in the family Dermateaceae and is a hemibiotrophic fungus that is restricted to the genus Rosa L. (Blechert and Debener, 2005). It is spread primarily through waterborne, two-celled asexual spores (conidia) that require free water to germinate. Visual symptoms may develop in susceptible cultivars in as little as 4 d after spore germination and penetration. The sexual stage of this fungus has been reported only twice in North America and twice in England (Horst, 1983), although frequency of sexual recombination in D. rosae populations has not been determined.
Phenotypic variability among single-conidial isolates suggests that D. rosae is a genetically diverse pathogen (Wenefrida and Spencer, 1993). Pathogenicity tests have revealed the presence of numerous races. Five races were discovered in Germany (Debener et al., 1998) among 15 isolates, four have been found in England (Yokoya et al., 2000), four were described in Ontario, Canada (Svejda and Bolton, 1980), and seven races were described in Mississippi (Spencer and Wood, 1992a, 1992b). Although it is not known whether any of these races from different studies are the same, the occurrence of multiple races in each location suggests a large total number of races in the world. The Mississippi isolates were collected from a seven-county area demonstrating diversity in pathogenicity within a relatively narrow geographic range. Considerable variability in conidial size and colony color among single-conidial isolates has also been documented (Wenefrida and Spencer, 1993).
Genetic diversity has been documented in D. rosae using molecular marker analyses. Lee et al. (2000) examined 10 isolates using restriction fragment length polymorphism (RFLP) analysis of the internal transcribed spacer region of rDNA. Distinct RFLP patterns were observed and isolates clustered into three groups. Initial studies by British researchers with simple sequence repeat and amplified fragment length polymorphism (AFLP) indicated that AFLP was the more reproducible and sensitive marker system for their isolates, although final results of their work have not yet been published (Drewes-Alvarez, 2003). Carlson-Nilsson (2002) conducted a randomly amplified polymorphic DNA analysis of 15 D. rosae isolates collected from locations in Sweden, Canada, France, and the United States, which were roughly separated by geographic origin in a cluster analysis. The survey did not allow in-depth analysis of geography, host of origin, pathogenic race, fungicide selection, or other factors on genetic similarity among isolates, although diversity among isolates was demonstrated. The current lack of knowledge about such factors and their influence on diversity complicates host resistance breeding efforts.
The objective of this study was a preliminary examination of the genetic diversity present in 50 single-spore isolates of D. rosae collected from eastern North American using AFLP analysis (Vos et al., 1995) and the manner in which diversity was distributed in relation to geographic origin, host of origin, or pathogenic race structure of the isolates under study. Such information is useful for the screening and evaluation of host resistance in rose germplasm targeted for North American markets.
Blechert, O. & Debener, T. 2005 Morphological characterization of the interaction between Diplocarpon rosae and various rose species Plant Pathol. 54 82 90
Broad Institute, Massachusetts Institute of Technology 2005 Status of FGI projects. Fungal genome initiative 1 Oct. 2005<www.broad.mit.edu/annotation/fgi/status.html>
Carlson-Nilsson, U.B. 2002 Variation in Rosa with emphasis on the improvement of winter hardiness and resistance to Marssonina rosae (blackspot) Swedish University of Agricultural Sciences Alnarp PhD Diss
Caujapé-Castells, J. & Baccarani-Rosas, M. 2004 Transformer-2: A program for the analysis of molecular population genetic data Jardín Botánico Canario ‘Viera y Clavijo’ and Instituto Tecnológico de Canarias, Las Palmas de Gran Canaria Spain
De Riek, J. , Calsyn, E. , Everaert, I. & Van Bockstaele, E. 2001 AFLP based alternatives for the assessment of distinctness, uniformity and stability of sugar beet varieties Theor. Appl. Genet. 103 1254 1265
Debener, T. , Drewes-Alvarez, R. & Rockstroh, K. 1998 Identification of five physiological races of blackspot, Diplocarpon rosae Wolf, on roses Plant Breed. 117 267 270
Douhan, G.W. , Peever, T.L. & Murray, D. 2002 Multilocus population structure of Tapesia yallundae in Washington state Mol. Ecol. 11 2229 2239
Drewes-Alvarez, R. 2003 Disease: Black spot 148 153 Roberts A.V. , Debener T. & Gudin S. Encyclopedia of rose science Elsevier Academic Press Oxford, UK
Felsenstein, J. 2004 Phylogeny inference package ver. 3.65 Department of Genome Sciences and Department of Biology, University of Washington Seattle
Kiprop, E.K. , Baudoin, J.P. , Mwang'ombe, A.W. , Kimani, P.M. , Mergeai, G. & Maquet, A. 2002 Characterization of Kenyan isolates of Fusarium udum from pigeonpea [Cajanus cajan (L.) Millsp.] by cultural characteristics, aggressiveness and AFLP analysis J. Phytopathol. 150 517 525
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Kiprop, E.K. Baudoin, J.P. Mwang'ombe, A.W. Kimani, P.M. Mergeai, G. Maquet, A. 2002 Characterization of Kenyan isolates ofJ. Phytopathol. Fusarium udumfrom pigeonpea [ Cajanus cajan(L.) Millsp.] by cultural characteristics, aggressiveness and AFLP analysis 150 517 525 10.1046/j.1439-0434.2002.00798.x
Koopman, W.J.M. , Zevenbergen, M.J. & Van den Berg, R.G. 2001 Species relationships in Lactuca s.l. (Lactuceae, Asteraceae) inferred from AFLP fingerprints Amer. J. Bot. 88 1881 1887
Lee, H.T. , Shin, H.D. , Hong, S.B. & Go, S.J. 2000 rDNA RFLP analysis of Marssonina coronaria and M. rosae Mycobiology 28 211 (Abstr.)
Lopes, M. , Rainieri, S. , Henschke, P.A. & Langridge, P. 1999 AFLP fingerprinting for analysis of yeast genetic variation Int. J. Syst. Bacteriol. 49 915 924
Majer, D. , Mithen, R. , Lewis, B.G. , Vos, P. & Oliver, R.P. 1996 The use of AFLP fingerprinting for the detection of genetic variation in fungi Mycol. Res. 100 1107 1111
Schneider, S. , Roessli, D. & Excoffier, L. 2000 Arlequin ver. 2.000: A software for population genetics data analysis Genetics and Biometry Laboratory, University of Geneva Switzerland
Spencer, J.A. & Wood, O.W. 1992a Response of selected old garden roses to seven isolates of Marssonina rosae in Mississippi J. Environ. Hort. 10 221 223
Spencer, J.A. & Wood, O.W. 1992b Resistance of selected rose cultivars to variants of Marssonina rosae in Mississippi J. Environ. Hort. 10 235 238
Svejda, F.J. & Bolton, A.T. 1980 Resistance of rose hybrids to three races of Diplocarpon rosae Can. J. Plant Pathol. 2 23 25
Taylor, J.W. , Jacobson, D.J. & Fisher, M.C. 1999 The evolution of asexual fungi: Reproduction, speciation and classification Annu. Rev. Phytopathol. 37 197 246
Urbanitez, A. & Dunemann, F. 2005 Isolation, identification and molecular characterization of physiological races of apple powdery mildew (Podosphaera leucotricha) Plant Pathol. 54 125 133
Von Malek, B. & Debener, T. 1998 Genetic analysis of resistance to blackspot (Diplocarpon rosae) in tetraploid roses Theor. Appl. Genet. 96 228 231
Vos, P. , Hogers, R. , Bleeker, M. , Reijans, M. , van de Lee, T. , Hornes, M. , Frijters, A. , Pot, J. , Peleman, J. , Kuiper, M. & Zabeau, M. 1995 AFLP: A new technique for DNA fingerprinting Nucleic Acids Res. 23 4407 4414
Wenefrida, I. & Spencer, J.A. 1993 Marssonina rosae variants in Mississippi and their virulence on selected rose cultivars Plant Dis. 77 246 248
Whitaker, V.M. , Zuzek, K. , Bradeen, J. & Hokanson, S.C. 2007a Culturing and long-term storage of virulent races of the rose blackspot pathogen, Diplocarpon rosae Wolf Acta Hort. 126 83 88
Whitaker, V.M. , Zuzek, K. & Hokanson, S.C. 2007b Resistance of twelve rose genotypes to fourteen isolates of Diplocarpon rosae (rose blackspot) collected from eastern North America Plant Breed. 126 83 88
Yokoya, K. , Kandasamy, K.I. , Walker, S. , Mandegaran, Z. & Roberts, A.V. 2000 Resistance of roses to pathotypes of Diplocarpon rosae. Ann. Appl. Biol. 136 15 20