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Thomas Debener - One of the best experts on this subject based on the ideXlab platform.
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the tnl gene rdr1 confers broad spectrum resistance to Diplocarpon Rosae
Molecular Plant Pathology, 2018Co-Authors: Ina Menz, Marcus Linde, Jannis Straube, Thomas DebenerAbstract:Black spot disease, which is caused by the ascomycete Diplocarpon Rosae, is the most severe disease in field-grown roses in temperate regions and has been distributed worldwide, probably together with commercial cultivars. Here, we present data indicating that muRdr1A is the active Rdr1 gene, a single-dominant TIR-NBS-LRR (Toll/interleukin-1 receptor-nucleotide binding site-leucine rich repeat) (TNL)-type resistance gene against black spot disease, which acts against a broad range of pathogenic isolates independent of the genetic background of the host genotype. Molecular analyses revealed that, compared with the original donor genotype, the multiple integrations that are found in the primary transgenic clone segregate into different integration patterns in its sexual progeny and do not show any sign of overexpression. Rdr1 provides resistance to 13 different single-spore isolates belonging to six different races and broad field mixtures of conidia; thus far, Rdr1 is only overcome by two races. The expression of muRdr1A, the active Rdr1 gene, leads to interaction patterns that are identical in the transgenic clones and the non-transgenic original donor genotype. This finding indicates that the interacting avirulence (Avr) factor on the pathogen side must be widespread among the pathogen populations and may have a central function in the rose-black spot interaction. Therefore, the Rdr1 gene, pyramided with only a few other R genes by sexual crosses, might be useful for breeding roses that are resistant to black spot because the spread of new pathogenic races of the fungus appears to be slow.
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a draft genome sequence of the rose black spot fungus Diplocarpon Rosae reveals a high degree of genome duplication
PLOS ONE, 2017Co-Authors: Enzo Neu, Jonathan Featherston, Jasper Rees, Thomas DebenerAbstract:Background Black spot is one of the most severe and damaging diseases of garden roses. We present the draft genome sequence of its causative agent Diplocarpon Rosae as a working tool to generate molecular markers and to analyze functional and structural characteristics of this fungus. Results The isolate DortE4 was sequenced with 191x coverage of different read types which were assembled into 2457 scaffolds. By evidence supported genome annotation with the MAKER pipeline 14,004 gene models were predicted and transcriptomic data indicated that 88.5% of them are expressed during the early stages of infection. Analyses of k-mer distributions resulted in unexpectedly large genome size estimations between 72.5 and 91.4 Mb, which cannot be attributed to its repeat structure and content of transposable elements alone, factors explaining such differences in other fungal genomes. In contrast, different lines of evidences demonstrate that a huge proportion (approximately 80%) of genes are duplicated, which might indicate a whole genome duplication event. By PCR-RFLP analysis of six paralogous gene pairs of BUSCO orthologs, which are expected to be single copy genes, we could show experimentally that the duplication is not due to technical error and that not all isolates tested possess all of the paralogs. Conclusions The presented genome sequence is still a fragmented draft but contains almost the complete gene space. Therefore, it provides a useful working tool to study the interaction of D. Rosae with the host and the influence of a genome duplication outside of the model yeast in the background of a phytopathogen.
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the gene diversity pattern of Diplocarpon Rosae populations is shaped by the age diversity and fungicide treatment of their host populations
Plant Pathology, 2017Co-Authors: A K Munnekhoff, Marcus Linde, Thomas DebenerAbstract:Black spot disease caused by the hemibiotrophic ascomycete Diplocarpon Rosae is the most devastating disease of field-grown roses. Although resistance to black spot is an important trait for rose breeding, little information on the diversity of the pathogen is currently available. To date, a number of single-spore isolates have been characterized based on a set of test genotypes of the host. In this study, six polymorphic simple sequence repeat (SSR) markers for D. Rosae were developed and their potential application to single-spore isolates collected from a wide range of geographic locations within and outside Europe discussed. Populations of the fungus were then analysed in different German rose collections/populations. Gene diversity was highest in older rose collections managed without fungicide application, and lowest in the two- to three-year-old testing sites of German rose breeders. Additional analyses of a global collection of single samples and populations revealed no unique alleles from any of the locations, indicating that global trading of rose varieties has led to an admixture of the pathogen.
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a standard set of host differentials and unified nomenclature for an international collection of Diplocarpon Rosae races
Plant Pathology, 2010Co-Authors: Vance M. Whitaker, A V Roberts, Thomas Debener, Stan C. HokansonAbstract:Black spot of rose is distributed throughout the world and is the most serious disease of roses (Rosa spp.) in the outdoor landscape. Resistance breeding has been frustrated by the occurrence of races of the causal pathogen Diplocarpon Rosae. Races from Germany, North America and the UK have been characterized and maintained in a pathogenic state. However, these races were characterized using independent sets of host genotypes and are referenced using different nomenclatures. In the present study, a total of 15 D. Rosae isolates from these locations, as well as Belgium and Italy, were inoculated to a common set of 15 rose cultivars in replicated, detached leaf trials. Baby LoveTM (cv. Scrivluv) was resistant to all isolates except for one originating from the UK. The rose cultivars Mrs Doreen Pike (Ausdor) and Hansa were resistant to all isolates except for one originating from Minnesota, USA. No rose genotype was universally susceptible. A total of 11 pathogenic races were differentiated based on their unique host ranges and were assigned an international race nomenclature. Nine cultivars are proposed as the first standard set of differential genotypes for characterization of D. Rosae races.
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genetic diversity of Diplocarpon Rosae implications on practical breeding
V International Symposium on Rose Research and Cultivation Gifu Japan 24-28 May 2009., 2010Co-Authors: A K Luhmann, Marcus Linde, Thomas DebenerAbstract:The risk of infection by a specific pathogen in a plant population mainly depends on the reproduction system and the gene flow of the pathogenic species. The hemibiotrophic pathogen Diplocarpon Rosae has a predominant asexual reproduction and is distributed by splash water and direct contact. Using D. Rosae specific SSRs, a low genetic diversity among fungal isolates was estimated in young rose plantations or in rose collections often treated with fungicides. In contrast, old and extensive collections of rose species and cultivars have up to three fold higher diversity of D. Rosae. Hence, the pressure of selection for resistance on a three year old rose test field is low compared to samples from older rose gardens. This indicates that active management of D. Rosae genetic diversity in rose test plots could significantly improve the selection of resistant roses in the field. Selection for black spot resistance in test fields of one or two years old roses is a common practice but causes little disease pressure on the tested genotypes. Leaves sampled from disease free plants of these fields showed up to 80% growth of D. Rosae after inoculation with conidia suspensions in the lab which is in agreement with the level of natural infections in the field. In conclusion of these results we propose an early selection for black spot resistance using artificial inoculations. Experiments with artificial inoculations of rose seedlings showed that this could generate a more intensive, faster and reliable selection for black spot resistance in roses. This could lead to cost saving and more efficient breeding of D. Rosae resistant rose cultivars.
Simeon O. Kotchoni - One of the best experts on this subject based on the ideXlab platform.
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Melanization of appressoria is critical for the pathogenicity of Diplocarpon Rosae.
Molecular biology reports, 2010Co-Authors: Emma W. Gachomo, Manfredo J. Seufferheld, Simeon O. KotchoniAbstract:Previous studies have shown the role of melanized appressoria in the pathogenicity of various fungi. Diplocarpon Rosae is a worldwide outdoor fungal pathogen of rose plants causing black spot disease of rose leaves. To fully understand how this fungus colonizes its host, which is critical for the development of an efficient and sustainable disease management program, we studied the fungal (especially the appressoria) structures of D. Rosae in detail at an early stage of infection. Using both microscopic and biochemical analyses, we observed strong melanized appressoria formation localized at the point of D. Rosae penetration, which forms the pathogen-plant interface. Treatment of infected plants with melanin biosynthesis inhibitors (MBIs) prevented melanization of D. Rosae appressoria and positively correlated with significant reductions in black spot disease symptoms, suggesting that melanization of appressoria might be a critical factor for the pathogenicity of D. Rosae. Our findings were confirmed and validated by the lack of melanized appressorial ring formation on an artificial surface and on a D. Rosae-non host plant system, Arabidopsis thaliana. Our findings suggest that localized melanization of appressoria is a crucial factor for the pathogenicity of D. Rosae and treatment of the fungus with MBIs seems to be a promising disease management alternative for black spot disease of roses.
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microscopic and biochemical evidence of differentially virulent field isolates of Diplocarpon Rosae causing black spot disease of roses
Plant Physiology and Biochemistry, 2010Co-Authors: Emma W. Gachomo, Simeon O. KotchoniAbstract:Black spot disease caused by Diplocarpon Rosae is one of the most widespread diseases of roses that are very difficult to control due to the generative reproduction and complex genetic constitution of roses and up to now the control of black spot still requires intensive use of systemic fungicides. Here we report for the first time evidence of differentially virulent field isolates of D. Rosae. Using a combination of fungal structures, disease symptoms and host cells protein expression pattern analysis we here provide direct biochemical evidence that tropical field isolates of D. Rosae are more virulent and caused disease symptoms earlier than their temperate counterparts. The tropical fungal field isolates strongly induced an excessive accumulation of ROS and repressed activity of pathogenesis-related proteins such as peroxidases, chitinase and phenylalanine ammonia lyase compared to their temperate counterparts. These findings bring insights into a hidden pathogenic characteristic of tropical D. Rosae field isolates compared to their temperate counterparts and open a novel dimension of parameters to be considered when controlling black spot disease of roses by fungicides in tropical versus temperate regions. Interestingly, we found that treatment of rose leaves with ROS (H2O2) prior to fungal inoculation promoted plant defense response regardless of the isolate virulence based on protein expression pattern analysis, suggesting that ROS (H2O2) can be efficiently incorporated into black spot disease management.
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detailed description of developmental growth stages of Diplocarpon Rosae in rosa a core building block for efficient disease management
Annals of Applied Biology, 2007Co-Authors: Emma W. Gachomo, Simeon O. KotchoniAbstract:Black spot disease of roses caused by the ascomycetous fungus Diplocarpon Rosae teleomorph (Marssonina Rosae anamorph) is a widespread and devastating disease. Despite considerable progress in the management of black spot disease in the recent years, it is still unclear by which mechanisms this fungus colonises and invades the host system, and without a good knowledge of such infection machineries, it not possible to fully overcome the challenges of D. Rosae infection. By exploring research contributions up to date, we highlight in this review the ultrastructure of D. Rosae infection cycle in the host cell by emphasising on several aspects related to its in vitro and in vivo germinations, the infection mechanisms of the fungus, the different fungal structures formed in the host cells and the optimum storage conditions for D. Rosae to retain its viability and pathogenicity over time. Here, attention is particularly focused on the asexual life cycle of D. Rosae, with the sexual cycle being briefly discussed. In addition, a new dimension of research approaches to effectively control black spot disease of roses, that is, how to accurately use the advanced biotechnology tools to speed up the current state of the disease management, is proposed here.
Stan C. Hokanson - One of the best experts on this subject based on the ideXlab platform.
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evaluation of roses from the earth kind trials black spot Diplocarpon Rosae wolf resistance and ploidy
Hortscience, 2010Co-Authors: David C Zlesak, Vance M. Whitaker, Steve George, Stan C. HokansonAbstract:Regional, replicated cultivar trials of landscape roses are an ongoing component of the Earth-Kind ® program, which was started at Texas A&M University in the 1990s to support environmental landscape stewardship. The rose trials within the Earth-Kind program identify and promote the most regionally adapted rose cultivars and are conducted without fertilizers or pesticides and greatly reduced irrigation. Black spot (caused by Diplocarpon Rosae Wolf) is the most serious disease of outdoor-grown roses worldwide as a result of the potential for rapid leaf yellowing and defoliation. Earth-Kind designated cultivars for the south-central United States and roses under trial in other regions or considered for future Earth-Kind trials (n = 73 roses) and two susceptible control cultivars were challenged with North American Races 3, 8, and 9 of D. Rosae, which were previously characterized at the University of Minnesota. Young expanded leaves were inoculated using detached leaf assays. Lesion length (LL) was measured for susceptible reactions and cultivar ploidy was determined using root tip squashes. Diploid, triploid, and tetraploid cultivars (n = 20, 30, and 23, respectively) were identified, and race-specific resistances and partial resistances were also identified. Race-specific resistance was generally more prevalent in newer rose cultivars and rose cultivars more recently included in Earth-Kind trials. Nine cultivars were resistant to all three races (Brite Eyes™, 'Grouse', Home Run ® , Knock Out ® , Paprika™, Peachy Cream™, Pink Knock Out ® , Rainbow Knock Out ® , and Yellow Submarine™). Blushing Knock Out ® , a sport of Knock Out ® , was susceptible to Race 8. Partial resistance rank for LL was generally consistent across races for roses susceptible to multiple races. The application of these data includes: characterizing the minimum resistance level needed for roses to warrant inclusion in Earth-Kind field trials, the identification of additional race-specific resistance genes, identifying resistance-breaking isolates of D. Rosae, understanding race composition in field trials based on infection patterns of key cultivars, selection of parents for resistance breeding efforts, and continued comparisons between LL and growing bodies of Earth-Kind field resistance data.
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a standard set of host differentials and unified nomenclature for an international collection of Diplocarpon Rosae races
Plant Pathology, 2010Co-Authors: Vance M. Whitaker, A V Roberts, Thomas Debener, Stan C. HokansonAbstract:Black spot of rose is distributed throughout the world and is the most serious disease of roses (Rosa spp.) in the outdoor landscape. Resistance breeding has been frustrated by the occurrence of races of the causal pathogen Diplocarpon Rosae. Races from Germany, North America and the UK have been characterized and maintained in a pathogenic state. However, these races were characterized using independent sets of host genotypes and are referenced using different nomenclatures. In the present study, a total of 15 D. Rosae isolates from these locations, as well as Belgium and Italy, were inoculated to a common set of 15 rose cultivars in replicated, detached leaf trials. Baby LoveTM (cv. Scrivluv) was resistant to all isolates except for one originating from the UK. The rose cultivars Mrs Doreen Pike (Ausdor) and Hansa were resistant to all isolates except for one originating from Minnesota, USA. No rose genotype was universally susceptible. A total of 11 pathogenic races were differentiated based on their unique host ranges and were assigned an international race nomenclature. Nine cultivars are proposed as the first standard set of differential genotypes for characterization of D. Rosae races.
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Partial resistance to black spot disease in diploid and tetraploid roses: general combining ability and implications for breeding and selection
Euphytica, 2009Co-Authors: Vance M. Whitaker, Stan C. HokansonAbstract:Black spot disease, incited by the fungus Diplocarpon Rosae Wolf, is the most important disease of roses ( Rosa hybrida L.) in the outdoor landscape. Though partial resistance exists in cultivated germplasm, the genetic basis of this trait has not yet been elucidated. Six diploid and six tetraploid rose cultivars were crossed in two factorial combining ability arrays. Whole plant and detached leaf inoculation methods were used to assess partial resistance under two different disease pressures using a characterized single-spore isolate. Parents from both arrays had significant general combining ability effects across multiple inoculation methods and environments. Specific combining ability was not significant for either array. Parent per se performance was highly correlated with progeny performance on a family mean basis. High positive correlations among whole plant and detached leaf inoculation methods indicate that detached leaf assays can substitute for whole plant assays. Based on these results, a breeding strategy including parental selection and early, among-family selection is proposed. To our knowledge, this is the first investigation of combining ability for disease resistance in rose.
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distribution of rose black spot Diplocarpon Rosae genetic diversity in eastern north america using amplified fragment length polymorphism and implications for resistance screening
Journal of the American Society for Horticultural Science, 2007Co-Authors: Vance M. Whitaker, Stan C. Hokanson, James M BradeenAbstract:ADDITIONAL INDEX WORDS. AMOVA, dendrogram, fungal isolate, Jaccard's coefficient, pathogenic race, principal component analysis ABSTRACT. Black spot, incited by the fungus Diplocarpon Rosae Wolf, is the most significant disease problem of landscape roses (Rosa hybrida L.) worldwide. The documented presence of pathogenic races necessitates that rose breeders screen germplasm with isolates that represent the range of D. Rosae diversity for their target region. The objectives of this study were to characterize the genetic diversity of single-spore isolates from eastern North America and to examine their distribution according to geographic origin, host of origin, and race. Fifty isolates of D. Rosae were collected from roses representing multiple horticultural classes in disparate locations across eastern North America and analyzed by amplified fragment length polymorphism. Considerable marker diversity among isolates was discovered, although phenetic and cladistic analyses revealed no significant clustering according to host of origin or race. Some clustering within collection locations suggested short-distance dispersal through asexual conidia. Lack of clustering resulting from geographic origin was consistent with movement of D. Rosae on vegetatively propagated roses. Results suggest that field screening for black spot resistance in multiple locations may not be necessary; however, controlled inoculations with single-spore isolates representing known races is desirable as a result of the inherent limitations of field screening.
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resistance of 12 rose genotypes to 14 isolates of Diplocarpon Rosae wolf rose blackspot collected from eastern north america
Plant Breeding, 2007Co-Authors: Vance M. Whitaker, Kathryn J Zuzek, Stan C. HokansonAbstract:Blackspot disease, caused by the fungus Diplocarpon Rosae Wolf, is the most serious disease problem of roses worldwide. From a breeding perspective, the documented occurrence of races in the pathosystem necessitates the characterization of the race structure for the pathogen, identification of resistance genes in rose germplasm, and determination of the nature of genetic resistance to breed stably resistant rose cultivars. The objective of this study was to characterize the diversity of eastern North American races of D. Rosae and to simultaneously determine the degree to which partial resistances existed in rose hosts. Twelve rose genotypes were inoculated with 14 single-conidial isolates collected from eastern North America. Three distinct D. Rosae races were identified based on presence/absence of infection in the differential array. There were five distinct reaction patterns across pathogen isolates among the 12 rose genotypes. The partial resistance components of leaf area with symptoms, lesion length and incubation period were evaluated for all inoculated plants. Variation for expression of partial resistance was noted, and partial resistance appears to behave in a race-specific manner for some rose genotypes. Early defoliation differed between genotypes and may prove to be another component of partial resistance.
U Steiner - One of the best experts on this subject based on the ideXlab platform.
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Efficacy of triazoles and strobilurins in controlling black spot disease of roses caused by Diplocarpon Rosae
Annals of Applied Biology, 2009Co-Authors: E W Gachomo, H W Dehne, U SteinerAbstract:Black spot disease is an important disease of roses with worldwide occurrence. It is caused by Diplocarpon Rosae, an ascomycetous fungus and its control relies on fungicides. The effects of strobilurins and triazoles on D. Rosae development within the host and on disease symptoms have not been well studied. Strobilurins completely inhibited germination of conidia when applied protectively I week before inoculation or on the same day with the inoculum. They were, however, not effective in eradicating the disease when applied after the fungus was established in the host. Triazoles reduced the germination rate of the conidia when applied protectively and they inhibited disease symptom development when applied after the fungus was established in the host but before symptom expression. Application of triazoles after symptom development suppressed further development of the disease, but in the case of treatment with myclobutanil yellowing and defoliation still occurred. Post-infection application of triazoles led to the apparent breakdown of subcuticular mycelia, intercellular mycelia, and hyphae in the epidermal cells, while the effects of strobilurins were limited to the subcuticular mycelia. Triazoles were more effective than strobilurins because they are more systemic.
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microscopic evidence for the hemibiotrophic nature of Diplocarpon Rosae cause of black spot disease of rose
Physiological and Molecular Plant Pathology, 2006Co-Authors: E W Gachomo, H W Dehne, U SteinerAbstract:The development of Diplocarpon Rosae was not fully understood and reports on the mode of nutrition in its rose host were conflicting. This report describes the ultrastructure of D. Rosae haustoria, and clarifies the developmental stages at which necrotrophic intracellular hyphae are formed. Evidence suggests that the mode of nutrition for this pathogen differs according to stages of its development and that D. Rosae is a hemibiotroph. It has a biotrophic phase characterized by haustoria and a necrotrophic phase characterized by necrotrophic intracellular hyphae.
Emma W. Gachomo - One of the best experts on this subject based on the ideXlab platform.
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Melanization of appressoria is critical for the pathogenicity of Diplocarpon Rosae.
Molecular biology reports, 2010Co-Authors: Emma W. Gachomo, Manfredo J. Seufferheld, Simeon O. KotchoniAbstract:Previous studies have shown the role of melanized appressoria in the pathogenicity of various fungi. Diplocarpon Rosae is a worldwide outdoor fungal pathogen of rose plants causing black spot disease of rose leaves. To fully understand how this fungus colonizes its host, which is critical for the development of an efficient and sustainable disease management program, we studied the fungal (especially the appressoria) structures of D. Rosae in detail at an early stage of infection. Using both microscopic and biochemical analyses, we observed strong melanized appressoria formation localized at the point of D. Rosae penetration, which forms the pathogen-plant interface. Treatment of infected plants with melanin biosynthesis inhibitors (MBIs) prevented melanization of D. Rosae appressoria and positively correlated with significant reductions in black spot disease symptoms, suggesting that melanization of appressoria might be a critical factor for the pathogenicity of D. Rosae. Our findings were confirmed and validated by the lack of melanized appressorial ring formation on an artificial surface and on a D. Rosae-non host plant system, Arabidopsis thaliana. Our findings suggest that localized melanization of appressoria is a crucial factor for the pathogenicity of D. Rosae and treatment of the fungus with MBIs seems to be a promising disease management alternative for black spot disease of roses.
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microscopic and biochemical evidence of differentially virulent field isolates of Diplocarpon Rosae causing black spot disease of roses
Plant Physiology and Biochemistry, 2010Co-Authors: Emma W. Gachomo, Simeon O. KotchoniAbstract:Black spot disease caused by Diplocarpon Rosae is one of the most widespread diseases of roses that are very difficult to control due to the generative reproduction and complex genetic constitution of roses and up to now the control of black spot still requires intensive use of systemic fungicides. Here we report for the first time evidence of differentially virulent field isolates of D. Rosae. Using a combination of fungal structures, disease symptoms and host cells protein expression pattern analysis we here provide direct biochemical evidence that tropical field isolates of D. Rosae are more virulent and caused disease symptoms earlier than their temperate counterparts. The tropical fungal field isolates strongly induced an excessive accumulation of ROS and repressed activity of pathogenesis-related proteins such as peroxidases, chitinase and phenylalanine ammonia lyase compared to their temperate counterparts. These findings bring insights into a hidden pathogenic characteristic of tropical D. Rosae field isolates compared to their temperate counterparts and open a novel dimension of parameters to be considered when controlling black spot disease of roses by fungicides in tropical versus temperate regions. Interestingly, we found that treatment of rose leaves with ROS (H2O2) prior to fungal inoculation promoted plant defense response regardless of the isolate virulence based on protein expression pattern analysis, suggesting that ROS (H2O2) can be efficiently incorporated into black spot disease management.
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detailed description of developmental growth stages of Diplocarpon Rosae in rosa a core building block for efficient disease management
Annals of Applied Biology, 2007Co-Authors: Emma W. Gachomo, Simeon O. KotchoniAbstract:Black spot disease of roses caused by the ascomycetous fungus Diplocarpon Rosae teleomorph (Marssonina Rosae anamorph) is a widespread and devastating disease. Despite considerable progress in the management of black spot disease in the recent years, it is still unclear by which mechanisms this fungus colonises and invades the host system, and without a good knowledge of such infection machineries, it not possible to fully overcome the challenges of D. Rosae infection. By exploring research contributions up to date, we highlight in this review the ultrastructure of D. Rosae infection cycle in the host cell by emphasising on several aspects related to its in vitro and in vivo germinations, the infection mechanisms of the fungus, the different fungal structures formed in the host cells and the optimum storage conditions for D. Rosae to retain its viability and pathogenicity over time. Here, attention is particularly focused on the asexual life cycle of D. Rosae, with the sexual cycle being briefly discussed. In addition, a new dimension of research approaches to effectively control black spot disease of roses, that is, how to accurately use the advanced biotechnology tools to speed up the current state of the disease management, is proposed here.