Key message Transcriptomic analysis resulted in the upregulation of the genes related to common defense mechanisms for black spot and the downregulation of the genes related to photosynthesis and cell wall modification for powdery mildew. Abstract Plant pathogenic fungi successfully colonize their hosts by manipulating the host defense mechanisms, which is accompanied by major transcriptome changes in the host. To characterize compatible plant pathogen interactions at early stages of infection by the obligate biotrophic fungus Podosphaera pannosa, which causes powdery mildew, and the hemibiotrophic fungus Diplocarpon rosae, which causes black spot, we analyzed changes in the leaf transcriptome after the inoculation of detached rose leaves with each pathogen. In addition, we analyzed differences in the transcriptomic changes inflicted by both pathogens as a first step to characterize specific infection strategies. Transcriptomic changes were analyzed using next-generation sequencing based on the massive analysis of cDNA ends approach, which was validated using high-throughput qPCR. We identified a large number of differentially regulated genes. A common set of the differentially regulated genes comprised of pathogenesis-related (PR) genes, such as of PR10 homologs, chitinases and defense-related transcription factors, such as various WRKY genes, indicating a conserved but insufficient PTI [pathogen associated molecular pattern (PAMP) triggered immunity] reaction. Surprisingly, most of the differentially regulated genes were specific to the interactions with either P. pannosa or D. rosae. Specific regulation in response to D. rosae was detected for genes from the phenylpropanoid and flavonoid pathways and for individual PR genes, such as paralogs of PR1 and PR5, and other factors of the salicylic acid signaling pathway. Differently, inoculation with P. pannosa leads in addition to the general pathogen response to a downregulation of genes related to photosynthesis and cell wall modification.Keywords Black spot · Powdery mildew · MACE analysis · High-throughput qPCR · WRKY genes · PR genes Enzo Neu and Helena Sophia Domes have contributed equally to this work. Electronic supplementary materialThe online version of this article (https ://doi.

Phosphorous starvation in plants has been reported to have contrasting effects on the interaction with pathogens in different plant pathogen systems and plant species. Both increases and decreases in susceptibility have been observed in numerous reports. Here, we analysed black spot infection and the leaf expression of two plant phosphate transporters and one defence marker gene in roses after phosphorous starvation. We varied three factors: phosphate starvation versus full supply of phosphorous, black spot infection vs. mock inoculation, and different susceptible and resistant progeny of a biparental rose population. Black spot susceptibility or resistance was not significantly changed upon phosphate starvation in either compatible or incompatible interactions. The expression of phosphate transporters was strongly induced upon starvation, but in some genotypes, expression was altered by black spot interaction as well. The marker for pathogenic interactions was exclusively induced by interaction with black spot, but the expression was altered by a combination of phosphate starvation and interaction with the fungus in some genotypes. In summary, phosphate starvation has clear effects on the gene expression of phosphate transporters in rose leaves, and the interaction with a hemibiotrophic leaf pathogen is strongly genotype dependent.

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