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Identification of genomic regions associated with host specificity and aggressiveness in Ceratocystis species

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

<div>The genus <em>Ceratocystis sensu stricto</em> includes more than 30 species of fungi that are pathogens of fruit and forest trees as well as agronomic crop plants. The type species, <em>C. fimbriata sensu stricto</em>, is host specific and causes black rot on <em>Ipomoea batatas</em>. <em>Ceratocystis manginecans</em> is genetically closely related to <em>C. fimbriata s.s</em>. and causes cankers and wilt on <em>Acacia</em> spp., mango and pomegranate, amongst others, but is not pathogenic to <em>I. batatas</em>. Despite their increasing economic importance, there is a paucity of knowledge regarding the factors that influence the host specificity and pathogenicity of these <em>Ceratocystis</em> spp. In this study, an interspecific cross was made between a <em>C. fimbriata</em> isolate from <em>I. batatas</em> and a <em>C. manginecans</em> isolate from <em>A. mangium.</em> Seventy F<sub>1</sub> progeny isolates were selected to investigate the inheritance of pathogenicity, mycelial growth rate and conidial production. Whole genome-based sequence analysis allowed construction of a linkage map that consisted of 467 SNPs, distributed across eight linkage groups and that spanned 1200 cM. We subsequently identified one highly significant QTL associated with growth rate on MEA, one associated with pathogenicity on <em>A. mangium</em> and two QTLs associated with pathogenicity on <em>I. batatas</em>. Candidate genes present in the QTLs are currently being characterized. These will be identified by investigating the presence/absence of genes in a species or nucleotide variations between the species.</div>