Analysis of allelic variants of RhMLO genes in rose and functional studies on susceptibility to powdery mildew related to clade V homologs.

Rose has 19 MLO genes. Of these, RhMLO1 and RhMLO2 were shown to be required for powdery mildew infection, which suggests their potential as susceptibility targets towards disease resistance. Powdery mildew, caused by Podosphaera pannosa, is one of the most serious and widespread fungal diseases for roses, especially in greenhouse-grown cut roses.

Interaction of roses with a biotrophic and a hemibiotrophic leaf pathogen leads to differences in defense transcriptome activation.

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. 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.

Isolation, Molecular Characterization, and Mapping of Four Rose MLO Orthologs.

Powdery mildew is a major disease of economic importance in cut and pot roses. As an alternative to conventional resistance breeding strategies utilizing single-dominant genes or QTLs, mildew resistance locus o (MLO)-based resistance might offer some advantages. In dicots such as Arabidopsis, pea, and tomato, loss-of-function mutations in MLO genes confer high levels of broad-spectrum resistance.

Evolution of the Rdr1 TNL-cluster in roses and other Rosaceous species.

Background: The resistance of plants to pathogens relies on two lines of defense: a basal defense response and a pathogen-specific system, in which resistance (R) genes induce defense reactions after detection of pathogen-associated molecular patterns (PAMPS). In the specific system, a so-called arms race has developed in which the emergence of new races of a pathogen leads to the diversification of plant resistance genes to counteract the pathogens' effect. The mechanism of resistance gene diversification has been elucidated well for short-lived annual species, but data are mostly lacking for long-lived perennial and clonally propagated plants, such as roses.

Mining disease-resistance genes in roses: functional and molecular characterization of the rdr1 locus.

The interaction of roses with the leaf spot pathogen Diplocarpon rosae (the cause of black spot on roses) is an interesting pathosystem because it involves a long-lived woody perennial, with life history traits very different from most model plants, and a hemibiotrophic pathogen with moderate levels of gene flow. Here we present data on the molecular structure of the first monogenic dominant resistance gene from roses, Rdr1, directed against one isolate of D. rosae.

Molecular markers from a BAC contig spanning the Rdr1 locus: a tool for marker-assisted selection in roses.

We constructed a BAC contig of about 300 kb spanning the Rdr1 locus for black spot resistance in Rosa multiflora hybrids, using a new BIBAC library from DNA of this species. From this contig, we developed broadly applicable simple sequence repeat (SSR) markers tightly linked to Rdr1, which are suitable for genetic analyses and marker-assisted selection in roses. As a source for the high molecular weight DNA, we chose the homozygous resistant R.