Characterization of the MAT1 locus involved in the sexual behaviour in isolates of Podosphaera xanthii from South Italy

and destructive pathogens of cucurbits in all growing areas. It shows a bipolar heterothallic mating system, with both mating types usually detected in the pathogen populations. The aim of this study was to characterize the mating type (MAT1) locus in P. xanthii to gain more insight into the genetic bases of the sexual behaviour of the pathogen. RNA-Seq data and the reference genomes of strains of opposite mating type were used for structural and functional annotation of the locus. Two mating type genes (MAT1-1-1 and MAT1-1-3) in the MAT1-1 idiomorph and one gene (MAT1-2-1) in the MAT1-2 idiomorph were identified. In both idiomorphs, the cytoskeleton assembly control (SLA2) and DNA lyase (APN2) genes, expected in the regions flanking the MAT1 locus as found in many Ascomycetes, were found far away (121 and 7 kbp, respetively) from the MAT1 genes. Several transposable elements classified by similarity search against Repbase using CENSOR belonging to DNA/Mariner, NonLTR/Tad1 and LTR/Gypsy classes, were identified in the regions included between SLA2 and APN2 gene locations including the MAT1 genes. Re-sequencing of the whole genomes of isolates of opposite mating type of the fungus is in progress to confirm the MAT1 locus architecture obtained by in-silico analysis. This study will contribute to obtain a characterization of mating type locus structure in powdery mildew fungi and a better understanding and possible factors responsible for the broad variation occurring in P. xanthii.