Genetic variability in populations of Chrysoporthe cubensis and Chr. puriensis in Brazil

Chrysoporthe puriensis, a sibling species of the well-known Eucalyptus canker pathogen Chr. cubensis, has recently been described from Brazil. Both species are thought to be native to South America, but previous population genetic analyses were conducted prior to the ready availability of robust markers such as microsatellites to test this hypothesis. The objective of this investigation was to analyse the structure and genetic variability of Chr. cubensis and Chr. puriensis populations from non-native Myrtaceae and native Melastomataceae hosts in Brazil, using microsatellite markers developed for this purpose. The fungal isolates were obtained from Eucalyptus species, Corymbia citriodora and Tibouchina species in different regions of the country. Isolates were separated into sub-populations based on host families (Melastomataceae and Myrtaceae) and on region of origin. There was high genetic variability in all sub-populations with the highest levels detected within, rather than among sub-populations. Gene and genotypic diversities were higher for the isolates from the Melastomataceae than the Myrtaceae isolates. High levels of gene flow were found between sub-populations based on host and geographic distribution of the sub-populations. The presence of genetically diverse Chr. cubensis and Chr. puriensis populations on native hosts in Brazil supports a Latin American centre of origin for the two pathogens. Both undergo sexual and asexual reproduction and have a high potential for gene flow.