De Novo assembly and characterization of the transcriptome of susceptible and resistant rose species in response to powdery mildew

Abstract Powdery mildew caused by Podosphera pannosa was a major disease in cut and potted roses. There were some rose species represent resistance to powdery mildew, others have susceptibility. However, the unclear resistance/susceptibility mechanism of wild Rosa to powdery mildew and the lack of related resistant genes have been limiting the utilization of wild Rosa in the genetic improvement of modern rose cultivars. In this study, we sequenced and assembled the transcriptome of the susceptible Rosa gigantea and the resistant Rosa longicuspis using de novo sequence assembly. Aims of the study were to preliminarily revealed their PM resistance/susceptibility mechanisms and find several genes which play important roles in Rosa-powdery mildew pathogen interactions. Our results indicating that: (1) the active response to P. pannosa infection in R. gigantea (susceptible wild species) occurred later than that in R. longicuspis (highly resistant wild species), and their responses also differed; (2) the regulatory network of R. gigantea in response to P. pannosa infection was more complex and diverse than that of R. longicuspis; (3) find two MLO members RgMLO6 and RlMLO7 which likely play important roles in interaction of Rosa-powdery mildew pathogen. These results will provide us data support for the functional evolution of disease resistance/susceptibility genes. Furthermore, they will provide us new ideas and gene pool for breeding new varieties of powdery mildew resistant rose.