Contrasting Genomic Diversity in Two Closely Related Postharvest Pathogens:Penicillium digitatumandPenicillium expansum

Abstract

Penicillium digitatum and Penicillium expansum are two closely related fungal plant pathogens causing green and blue mold in harvested fruit, respectively. The two species differ in their host specificity, being P. digitatum restricted to citrus fruits and P. expansum able to infect a wide range of fruits after harvest. Although host-specific Penicillium species have been found to have a smaller gene content, it is so far unclear whether these different host specificities impact genome variation at the intraspecific level. Here we assessed genome variation across four P. digitatum and seven P. expansum isolates from geographically distant regions. Our results show very high similarity (average 0.06 SNPs [single nucleotide polymorphism] per kb) between globally distributed isolates of P. digitatum pointing to a recent expansion of a single lineage. This low level of genetic variation found in our samples contrasts with the higher genetic variability observed in the similarly distributed P. expansum isolates (2.44 SNPs per kb). Patterns of polymorphism in P. expansum indicate that recombination exists between genetically diverged strains. Consistent with the existence of sexual recombination and heterothallism, which was unknown for this species, we identified the two alternative mating types in different P. expansum isolates. Patterns of polymorphism in P. digitatum indicate a recent clonal population expansion of a single lineage that has reached worldwide distribution. We suggest that the contrasting patterns of genomic variation between the two species reflect underlying differences in population dynamics related with host specificities and related agricultural practices. It should be noted, however, that this results should be confirmed with a larger sampling of strains, as new strains may broaden the diversity so far found in P. digitatum.

A multidisciplinary approach to study virulence of the entomopathogenic fungus Beauveria bassiana towards malaria mosquitoes

“…For instance, Ghikas et al (2010) described seven phylogenetic clusters in B. bassiana that consisted of isolates which did not show any geographic distribution but had common climate characteristics, and studies from Meyling et al (2009) found isolates that were distributed in five clusters in a particular hedgerow habitat. Furthermore, a comparative genomic study of seven isolates of the plant pathogen Penicillium expansum showed that the genetic diversity found was between 1.27-7.13 SNPs/kb (Julca et al, 2016), while in two isolates of Aspergillus niger it was on average 7.8 SNPs/kb (Andersen et al, 2011). In both cases, the genetic diversity observed was lower than the level found in this study (2.85-16.81 SNPs/kb).…”

Penicillium expansum strain isolated from indoor building material was able to grow on gypsum board and emitted guttation droplets containing chaetoglobosins and communesins A, B and D

“…Penicillium expansum is a ubiquitous filamentous fungus causing the serious postharvest disease known as blue mould in harvested apples, peaches and hazels (Julca et al 2015). It is known to produce the potent mycotoxins communesins, chaetoglobosins and patulin when growing on fruits (Andersen et al 2004;Nielsen et al 2004;Tannous et al 2016).…”

Comparative genomics of Beauveria bassiana: uncovering signatures of virulence against mosquitoes

“…One study [61] described seven phylogenetic clusters in B. bassiana that consisted of isolates which did not show any geographic distribution but had common climate characteristics, while a different study [48] described isolates that were distributed in five clusters in a particular hedgerow habitat, however, genetic distances were not determined on a genome-wide scale in these studies. A comparative genomic study of seven isolates of the plant pathogenic fungus Penicillium expansum revealed a genetic diversity between 1.3 and 7.1 SNPs/kb [62], while between two isolates of Aspergillus niger it was 7.8 SNPs/kb [63]. In both these cases, the genetic diversity was lower than observed in this study (2.9–16.8 SNPs/kb).…”