Molecular characterization of Fusarium spp. causing peanut brown root rot and strategies for their biocontrol

GANUZA M.; PASTOR, N.; CASASNOVAS, F.; REYNOSO M.M.; ROVERA, M.; TORRES A.M.

Berlin

Congreso; XVIII International Plant Protection Congress; 2015

German Society for Plant Protection and Plant Health

Argentina is a major peanut-producing country. During the 2011/12 season, peanut production exceeded 680 000 tons. Most of the peanuts are exported to the European Union and the USA. Diseases caused by soil pathogenic fungi limit peanut production. Peanut brown root rot (PBRR) was first described in Argentina in 1992. The etiological agent responsible was reported as Fusarium solani (Mart.) Appel and Wollenweber, but the pathogen was not well described. Koch?s postulates were completed with strains from this group to show that these strains are responsible for this disease. We used a combination of morphologicaland molecular markers, amplified fragment length polymorphism (AFLPs), and molecular sequence analysis of internaltranscribed spacer region (ITS) of the translation elongation factor 1-alpha gene (TEF-1α), and the α-tubulin gene in 15 Fusarium isolates obtained from peanut plants exhibiting symptoms of root rot, to characterize strains of this pathogen in the Fusarium solani species complex (FSSC). Also, evaluation of the efficacy of bioagents application against PBRR disease incidence was carried out under greenhouse conditions. The evaluated bioagents were Trichoderma harzianum ITEM 3636 and/or Pseudomonas sp. RC-93 alone and in co-inoculation. The disease was significantly reduced at all treatments comparing with untreated plants. Based on unique pathogenic capabilities, the genetically close relationship identified with the AFLPs, and the evidence of a monophyletic clade in the phylogenetic analysis, we conclude that Fusarium solani strains causing PBRR formed part of a distinct lineage previously known to be associated with soils, FSSC 3+4, to which the name F. falciforme has been associated. Recently, and due to the fact that these two groups are not well supported individually in phylogenetic analysesthey have been combined provisionally into a single phylogenetic species, FSSC 3+4, in the absence of strong support for their respective distinctiveness. Since both T. harzianum ITEM 3636 and Pseudomonas sp. RC-93 exhibited several traits beneficial to the plant host and showed promising results when applied as bioinoculants, they may be used to develop new, safer and effective formulations as an alternative or supplement to chemical fungicides and/or fertilizers.