Caracterização de espécies homotálicas no complexo Fusarium solani

Abstract

The Fusarium solani species complex - FSSC (teleomorph Haematonectria, Hypocreales, Ascomycota) is an assemblage of pathogens of various plants of agricultural importance, especially in tropical and sub-tropical regions. The objective of this study was to evaluate the presence of homothallic biological species from a collection of 238 isolates of Fusarium solani, obtained from different host plants through homothallism tests and phylogenetic analysis of TEF and RPB2 regions. It was also evaluated if homothallic isolates are pathogenic and show specificity with regard to the host plant. To test for homothallism, single spore isolates were transferred to Petri dishes containing SNA culture medium and complete medium and kept at room temperature for about 60 days with weekly evaluations. Phylogenetic analysis was performed with partial sequences of the gene encoding elongation factor 1α and second largest subunit of RNA polymerase, including sequences from reference strains belonging to several species of the FSSC. Pathogenicity tests were performed on host plants of F. solani such as Passiflora edulis, Solanum melongena, Cucumis melo and Pisum sativum. Seventeen isolates were homothallic, of which nine form a clade together with other homothallic reference strains known as Fusarium striatum, representing a distinct phylogenetic species within the Fusarium solani species complex. The homothallic isolates did not induce symptoms of root rot in any of the plants analyzed, and may be associated to plants as saprophytes. According to the analysis of morphological characteristics no marker which distinguishes the homothallic isolates from other FSSC species could be detected. Both nomenclature of homothallic forms as well as phytopathogen status should be reviewed.