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Whole genome comparisons of the host specific species Ceratocystis fimbriata sensu stricto and C. manginecans

Arista Fourie: Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria

<div>The fungus <em>Ceratocystis</em> <em>manginecans</em> is a devastating pathogen of trees in fruit orchards and forestry plantations world-wide. It causes canker and wilt disease on a broad range of species, including mango, pomegranate and wattle, but has never been isolated from tuber crops. In contrast, the closely related species <em>C. fimbriata sensu stricto</em> infects only sweet potato where it causes black rot. In this study, the genome sequences of three <em>C. manginecans</em> isolates and one <em>C. fimbriata</em> isolate were determined and compared, to identify genetic differences associated with host specificity. Results showed that <em>C. manginecans</em> has a marginally larger genome size (32Mb vs 30Mb), which could be attributed to a higher repetitive element content (18% vs 13%), but the species had similar gene numbers (~7200). Only 1% of the genes was unique to a species, of which many were hypothetical proteins or putative secreted effectors. Equivalent catalogues of CAZYs, peptidases, lipases and secondary metabolite biosynthetic gene clusters were detected in both species. Genome alignments identified exclusive genomic regions containing genes that were only present in <em>C. manginecans</em>. Future functional characterization should reveal the roles of the identified unique genes in the biology of these fungi and their ability to thrive in their niches.</div>