Fusarium solani f. sp. piperis the causal agent of fusariosis of black pepper in Brazil is a distinct phylogenetic and biological species in the FSSC
L. H. PFENNING (1), A. B. Vaz (1), S. S. Costa (1), L. M. Abreu (1), J. A. Ventura (2). (1) Universidade Federal de Lavras, Lavras, Brazil; (2) Instituto Capixaba de Pesquisa, Assistencia Tecnica e Extensao Rural INCAPER, Vitoria, Brazil
The main disease of <i>Piper nigrum</i> in Brazil is caused by <i>Fusarium solani</i> f. sp. <i>piperis</i> (FSP). Disease symptoms include leaf chlorosis, blight of stems, root and foot decay. The objectives of this study were to investigate whether this form corresponds to a biological and phylogenetic species within the <i>Fusarium solani</i> Species Complex - FSSC. One hundred and four isolates with characteristics of <i>F. solani</i> were obtained from diseased plants collected in the main producing areas and characterized by means of laboratory crosses, phylogenetic analyses, and pathogenicity tests. Tests for homothallism and crossings of isolates of opposite mating types identified 10 homothallic isolates and a set of 25 heterothallic intercrossing strains. In phylogenetic analyses conducted with 44 isolates using partial sequences of the genes TEF, RPB2 and ITS-LSU rDNA, the sexually compatible isolates formed a single clade (100% bootstrap support) together with a reference strain of FSP, and distinct from other species and forms in the FSSC. Remaining isolates were grouped in 10 different lineages in a phylogenetic tree based on TEF sequences. In pathogenicity tests repeated twice with 35 isolates, only isolates of FSP induced disease symptoms on inoculated plants. According to our results, the pathogen represents a phylogenetic and biological species in the FSSC. Other heterothallic and homothallic isolates of <i>F. solani</i> occur in association with black pepper, but do not cause disease.
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