Danila Valentino

The ITS region as a taxonomic discriminator between Fusarium verticillioides and Fusarium proliferatum

The maize pathogens Fusarium verticillioides (Fv) and Fusarium proliferatum (Fp) are morphologically very similar to one another, so Fp isolates have been often mistaken as Fusarium moniliforme (the former name of Fv). The only presently accepted morphological discriminator between these species is the presence/absence of polyphialides. Here, a collection of 100 Fusarium strains, isolated from infected maize kernels on plants grown in north-western Italy, were assigned as Fv or Fp on the basis of the presence/absence of polyphialides. This classification was tested on a subset of isolates by sexual crosses, ITS and calmodulin sequencing and AFLP profiling. An ITS-RFLP assay was extended to the full collection and to a number of Fv and Fp isolates of different geographical origin and hosts. The ITS region is proposed as taxonomically informative for distinguishing between Fp and Fv.

GNOMONIOPSIS CASTANEA sp. nov. (GNOMONIACEAE, DIAPORTHALES) AS THE CAUSAL AGENT OF NUT ROT IN SWEET CHESTNUT

The genus Gnomoniopsis (Gnomoniaceae, Diaporthales) is currently composed of 13 species which are endophytic and/or parasitic to plants in the families Fagaceae, Onagraceae and Rosaceae. Species definition is based on a combination of morphological traits, association with specific plant hosts, and phylogeny. In this paper a new species, Gnomoniopsis castanea sp. nov., is described based on the association with Castanea sativa (a plant species never reported to be infected by fungi the genus Gnomoniopsis), morphology and phylogenetic analysis of the ITS region of ribosomal DNA and on the EF1-a locus. The fungus is consistently associated with nut rot and caused the disease when artificially inoculated to fruits or flowers. Infection incidence varied depending on the orchard and the year and attained up to 83% of the nuts in some areas of north-western Italy. The fungus was also consistently isolated from the bark of symptomless branches in naturally infected chestnut orchards.

DNA-Based Tools for the Detection of Fusarium spp. Pathogenic on Maize

Pink and red ear rot of maize are common diseases in temperate cropping zones. These diseases are caused by toxigenic fungi belonging to the genus Fusarium. Economic losses flow from both reduced yield (shriveled grain) and compromised quality (contamination with mycotoxin). Since the etiology of these diseases is complex and the taxonomy of the genus Fusarium is fluid, there has been a rapid evolution of PCR-based assays for the detection and quantification of toxigenic Fusarium spp. in biological material, and for their assignment to the correct phylogenetic species. Following a brief overview of the symptoms and epidemiology of ear rots in maize, we discuss the toxigenicity of the causal agents and their taxonomy, and finally survey the range of DNA-based tools available for the detection, identification, and quantification of Fusarium spp. pathogenic on maize.

Genome reconstruction in Cynara cardunculus taxa gains access to chromosome-scale DNA variation

The genome sequence of globe artichoke (Cynara cardunculus L. var. scolymus, 2n = 2x = 34) is now available for use. A survey of C. cardunculus genetic resources is essential for understanding the evolution of the species, carrying out genetic studies and for application of breeding strategies. We report on the resequencing analyses (~35×) of four globe artichoke genotypes, representative of the core varietal types, as well as a genotype of the related taxa cultivated cardoon. The genomes were reconstructed at a chromosomal scale and structurally/functionally annotated. Gene prediction indicated a similar number of genes, while distinctive variations in miRNAs and resistance gene analogues (RGAs) were detected. Overall, 23,5 M SNP/indel were discovered (range 6,34 M –14,50 M). The impact of some missense SNPs on the biological functions of genes involved in the biosynthesis of phenylpropanoid and sesquiterpene lactone secondary metabolites was predicted. The identified variants contribute to infer on globe artichoke domestication of the different varietal types, and represent key tools for dissecting the path from sequence variation to phenotype. The new genomic sequences are fully searchable through independent Jbrowse interfaces (www.artichokegenome.unito.it), which allow the analysis of collinearity and the discovery of genomic variants, thus representing a one-stop resource for C. cardunculus genomics.

Do pathogen-specific defense mechanisms contribute to wound-induced resistance in tomato?

A network of shared intermediates/components and/or common molecular outputs in biotic and abiotic stress signaling has long been known, but the possibility of effective influence between differently triggered stresses (co-protection) is less studied. Recent observations show that wounding induces transient protection in tomato (Solanum lycopersicum L.) to four pathogens with a range of lifestyles, locally and systemically. The contribution of ethylene (ET) in basal but also in wound-induced resistance to each pathogen, although dispensable, is demonstrated to be positive (Botrytis cinerea, Phytophthora capsici) or negative (Fusarium oxysporum, Pseudomonas syringae pv. tomato). Furthermore, the expression of several defense markers is influenced locally and/or systemically by wounding and ET, and might be part of that core of conserved molecular responses whereby an abiotic stress such as wounding imparts co-resistance to biotic stress. In this addendum, we speculate on some of the physiological responses to wounding that might contribute to the modulation of resistance in a more pathogen-specific manner.

The Legitimate Name of a Fungal Plant Pathogen and the Ethics of Publication in the Era of Traceability.

When more scientists describe independently the same species under different valid Latin names, a case of synonymy occurs. In such a case, the international nomenclature rules stipulate that the first name to appear on a peer-reviewed publication has priority over the others. Based on a recent episode involving priority determination between two competing names of the same fungal plant pathogen, this letter wishes to open a discussion on the ethics of scientific publications and points out the necessity of a correct management of the information provided through personal communications, whose traceability would prevent their fraudulent or accidental manipulation.