Identification and Characterization of a QTL for Growth of Fusarium circinatum on Pine-Based Medium

Fusarium circinatum is an economically important pathogen of pine and resides in the Fusarium fujikuroi species complex. Here we investigated the molecular processes underlying growth in F. circinatum by exploring the association between growth and the nutritional environment provided by the pine host. For this purpose, we subjected a mapping population consisting of F. circinatum X F. temperatum hybrid progeny to an analysis of growth rate on a pine-tissue derived medium. These data, together with the available genetic linkage map for F. circinatum, were then used to identify Quantitative Trait Loci (QTLs) associated with growth. The single significant QTL identified was then characterized using the available genome sequences for the hybrid progeny’s parental isolates. This revealed that the QTL localized to two non-homologous regions in the F. circinatum and F. temperatum genomes. For one of these, the F. circinatum parent contained a two-gene deletion relative to the F. temperatum parent. For the other region, the two parental isolates encoded different protein products. Analysis of repeats, G+C content, and repeat-induced point (RIP) mutations further suggested a retrotransposon origin for the two-gene deletion in F. circinatum. Nevertheless, subsequent genome and PCR-based analyses showed that both regions were similarly polymorphic within a collection of diverse F. circinatum. However, we observed no clear correlation between the respective polymorphism patterns and growth rate in culture. These findings support the notion that growth is a complex multilocus trait and raise the possibility that the identified QTL contains multiple small-effect QTLs, of which some might be dependent on the genetic backgrounds. This study improved our current knowledge of the genetic determinants of vegetative growth in F. circinatum and provided an important foundation for determining the genes and processes underpinning its ability to colonize its host environment.

IMA Genome-F 9: Draft genome sequence of Annulohypoxylon stygium, Aspergillus mulundensis, Berkeleyomyces basicola (syn. Thielaviopsis basicola), Ceratocystis smalleyi, two Cercospora beticola strains, Coleophoma cylindrospora, Fusarium fracticaudum, Phialophora cf. hyalina, and Morchella septimelata

Draft genomes of the species Annulohypoxylon stygium, Aspergillus mulundensis, Berkeleyomyces basicola (syn. Thielaviopsis basicola), Ceratocystis smalleyi, two Cercospora beticola strains, Coleophoma cylindrospora, Fusarium fracticaudum, Phialophora cf. hyalina and Morchella septimelata are presented. Both mating types (MAT1-1 and MAT1-2) of Cercospora beticola are included. Two strains of Coleophoma cylindrospora that produce sulfated homotyrosine echinocandin variants, FR209602, FR220897 and FR220899 are presented. The sequencing of Aspergillus mulundensis, Coleophoma cylindrospora and Phialophora cf. hyalina has enabled mapping of the gene clusters encoding the chemical diversity from the echinocandin pathways, providing data that reveals the complexity of secondary metabolism in these different species. Overall these genomes provide a valuable resource for understanding the molecular processes underlying pathogenicity (in some cases), biology and toxin production of these economically important fungi.