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

Abstract

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.

Genetic diversity and population structure of Chrysoporthe deuterocubensis isolates from Melastoma and Eucalyptus in Malaysia and Indonesia

“…remain plausible candidates for the native hosts of C . deuterocubensis in Asia and this would be consistent with the study of Oliveira et al (2022) who showed clear evidence of a Melastoma sp. in Brazil as a native host of both C. cubensis and C. puriensis .…”

“…The same sub‐clades for isolates of C . deuterocubensis have also been noted in previous studies (Myburg, Gryzenhout, Heath, et al, 2002; Oliveira et al, 2022). It is not unusual of find such differences in gene regions for a single species, especially where the populations are large (Milgroom, 1996 ), and we believe that it is reasonable to treat the isolates used in this study as those of C. deuterocubensis .…”

“…of expected genotypes at the smallest sample size based on rarefaction ± Standard error) (Grünwald et al, 2003). ies (Myburg, Gryzenhout, Heath, et al, 2002;Oliveira et al, 2022).…”

“…However, this hypothesis was contested in a recent study showing that a member of the Melastomataceae is most likely a native host of C . cubensis in South America and that a host shift to Eucalyptus has occurred (Oliveira et al, 2022; Rodas et al, 2005; Van der Merwe et al, 2013). A similar situation has apparently occurred with C .…”

“…For many years, C. cubensis on Eucalyptus in Brazil was believed to have originated on Syzygium aromaticum L. (clove) in Indonesia (Hodges et al, 1986). However, this hypothesis was contested in a recent study showing that a member of the Melastomataceae is most likely a native host of C. cubensis in South America and that a host shift to Eucalyptus has occurred (Oliveira et al, 2022;Rodas et al, 2005;Van der Merwe et al, 2013). A similar situation has apparently occurred with C. austroafricana, which occurs naturally on various native Syzygium spp.…”