Cronartium Comparative Genomics: Understanding the Canker Causing Basidiomycete Genomes

Cronartium ribicola JC Fisch, causal agent of white pine blister rust, is an obligate basidiomycete responsible for the decline of five needle pines across the North American landscape. A non-native pathogen, most likely originating from Asia, C. ribicola was first introduced into eastern North America from Europe. Multiple introductions have been recorded on the Eastern seaboard, whereas, a single introduction was described in the Pacific Northwest region. By decimating the natural stands of western white pines, C. ribicola has played a significant role in shifting the dominant tree species in the northwestern US. We have sequenced the C. ribicola genome using next-gen sequencing technology, along with two other rust pathogens, C. comandrae and Peridermium harknessii. Native to North America, C. comandrae is found on two- and three-needle pines and causes the comandra blister rust disease. Both C. ribicola and C. comandrae are heteroecious, i.e. these require two different plant hosts to complete their life cycle. On the other hand, P. harknessii, the western gall rust pathogen occurring on two- and three-needle pines, is an autoecious rust, requiring only one host for its survival. Through sequence analyses of the C. ribicola genome and comparative studies with the related rust pathogens, we aim to explore and understand the underlying factors that determine the differences among these three rust species at the genomic level. This will help answer some fundamental questions about the biology, host preference and etiology of these closely related rust pathogens and eventually understand the evolutionary significance of these attributes.