Genetic structure and evolutionary diversity of mating-type (MAT) loci in Hypsizygus marmoreus

The mating compatibility in fungi is generally governed by genes located within a single or two unlinked mating type (MAT) loci. Hypsizygus marmoreus is an edible mushroom in the order Agaricales with a tetrapolar system, which contains two unlinked MAT loci-homeodomain (HD) transcription factor genes and pheromone/pheromone receptor genes (P/R). In this study, we analyzed the genetic structure and diversity of MAT loci in tetrapolar system of H. marmoreus through sequencing of 54 heterokaryon and 8 homokaryon strains. Although within the HD loci, the gene order was conserved, the gene contents were variable, and the HD loci haplotypes were further classified into four types. By analyzing the structure, phylogeny, and the HD transmissibility based on the progeny of these four HD mating-type loci types, we found that they were heritable and tightly linked at the HD loci. The P/R loci genes were found to comprise three pheromone receptors, three pheromones, and two pheromone receptor-like genes. Intra- and inter-specific phylogenetic analyses of pheromone receptors revealed that the STE3 genes were divided into three groups, and we thus theorize that they diverged before speciation. Comparative analysis of the MAT regions among 73 Basidiomycete species indicated that the diversity of HD and P/R loci in Agaricales and Boletales may contribute to mating compatibility. The number of HD genes were not correlated with the tetrapolar or bipolar systems. In H. marmoreus, the expression levels of these genes at HD and P/R loci of compatible strains were found higher than in those of homonuclear/homokaryotic strains, indicating that these mating genes acted as switches for mating processes. Further collinear analysis of HD loci in interspecific species found that HD loci contains conserved recombination hotspots showing major rearrangements in Coprinopsis cinerea and Schizophyllum commune, suggesting different mechanisms for evolution of physically linked MAT loci in these groups. It seems likely that gene rearrangements are common in Agaricales fungi around HD loci. Together, our study provides insights into the genomic basis of mating compatibility in H. marmoreus.

MATING TYPE CHARACTERIZATION OF FUSARIUM CULMORUM STRAINS CAUSING WHEAT CROWN ROT IN IRAQ

Fusarium crown rot (CR) of wheat is one of the most important diseases known from regions of the world where cereal crops are produced. In this study, we examined the mating types of F. culmorum CR strains isolated across Iraq, including more arid regions within the country. The result showed two mating compatibility (MAT) type idiomorphs of F. culmorum are present in Iraq, with 27.6% of the isolates examined representing the MAT-1 type and 72.4% representing the MAT-2 type. The MAT-1 type was commonly found among isolates from the mid-latitudes of Iraq, this being a warmer and drier region as compared to the country’s northern region; however, it was also detected from one isolate from a northern site. The MAT-2 type, however, was more broadly distributed across Iraq and was also detected among many isolates from the mid-latitude region. Thus specific biogeographic patterns were not apparent for mating compatibility idiomorphs. The mating types characterized here were also compared to chemotypes known for these same isolates and characterized in a previous study. This comparison revealed the MAT-1 type was found only among DON chemotype isolates, while the MAT-2 type was found among both DON and NIV chemotype isolates. Thus, there does not appear to be a direct correspondence between chemotype and mating compatibility idiomorphs within Iraq. Overall, a broader sampling across the country with more isolates being examined at each site is advised.

Ophiostoma pehueninum, a new species associated with Araucaria araucana in Chile

During a survey of fungi on Araucaria araucana in Chile, a species of Ophiostoma morphologically different to O. araucariae was collected in the Andean region. Morphological characteristics and phylogenetic analyses of ITS, β-tubulin and EF-1α sequences confirmed that this species represents a novel taxon. This taxon is described here as Ophiostoma pehueninum sp. nov. The sexual morph of O. pehueninum was characterized by long neck and peridial hyphae around the bases, and allantoid ascospores surrounded by a gelatinous sheath. In culture a hyalorhinocladiella-like asexual morph was observed. Mating compatibility tests indicated that the species is heterothallic.

Biological characterization and mating compatibility of Helicoverpa gelotopoeon (D.) (Lepidoptera: Noctuidae) populations from different regions in Argentina

Helicoverpa gelotopoeon, the South American bollworm, is a polyphagous pest of the Heliothinae complex that causes damage to soybean, cotton, and chickpea crops. Some species within this complex have developed resistance to genetically modified crops and insecticides, which has led to increased interest in their genetic diversity and population structure. The objective of this study was to characterize biological and reproductive parameters of two populations of H. gelotopoeon collected in two different provinces of Argentina. Intra- and inter-population crosses revealed that H. gelotopoeon populations from both regions of Argentina did not present evidence of pre-zygotic and post-zygotic incompatibility, suggesting that Tucumán and Córdoba populations of H. gelotopoeon belong to a single wide-ranging species. Our data support the occurrence of substantial gene flow between H. gelotopoeon populations, probably due to the widely documented, long-range migratory capacity of Heliothinae species.