Identifying variation in red raspberry MLO genes thought to provide resistance to powdery mildew

J.D. Zurn, R. Meiers, J. Ward, C.E. Finn, M. Dossett, N.V. Bassil
Mutations in MLO genes have been shown to confer durable broad-spectrum resistance to powdery mildew in many plant species. Very little work has been done to characterize the genetics underlying resistance to powdery mildew (PM) in red raspberry (Rubus idaeus L.) caused by Podosphaera aphanis var. aphanis. Powdery mildew of raspberry has the potential to become more of a problem in the Pacific Northwest in the near future. To better characterize red raspberry MLO genes, 95 accessions from the USDA-ARS red raspberry germplasm collection housed at the National Clonal Germplasm Repository in Corvallis, OR were screened for natural genetic variation. MLO candidate genes from the 'Heritage' genome assembly thought to be associated with mlo-mediated powdery mildew resistance were identified by comparing red raspberry sequences to known MLO genes from other plant species. Two red raspberry MLO candidate genes, RedRasp_17904t and RedRasp_26700t were identified to potentially be associated with mlo-mediated resistance. Sequencing of the exons in these genes revealed 22 SNPs in RedRasp_17904t that would result in 11 single amino acid substitutions. In RedRasp_26700t, 23 SNPs were found that would result in eight amino acid substitutions. Phylogenetic analysis indicated that accessions with previously reported PM resistance have closely related haplotypes for RedRasp_17904t. Additional work is needed to determine if any of these mutations can result in mlo-mediated powdery mildew resistance.
Zurn, J.D., Meiers, R., Ward, J., Finn, C.E., Dossett, M. and Bassil, N.V. (2020). Identifying variation in red raspberry MLO genes thought to provide resistance to powdery mildew. Acta Hortic. 1277, 25-32
DOI: 10.17660/ActaHortic.2020.1277.4
Podosphaera aphanis, Rubus idaeus, EcoTILLING, germplasm

Acta Horticulturae