Oral Technical Session: Fusarium

207-O

Fusarium decemcellulare associated with cushion gall and dieback of tropical trees in Brazil and Mexico.
G. RODRIGUEZ-ALVARADO (1), L. M. Abreu (2), E. A. Guimarães (2), S. S. Costa (2), J. L. Bezerra (3), L. H. Pfenning (2)
(1) Universidad Michoacana de San Nicolas de Hidalgo, Morelia, Michoacan, Mexico; (2) Universidade Federal de Lavras, Lavras, Brazil; (3) Universidade Estadual de Santa Cruz, Ilheus, Brazil

Fusarium decemcellulare is reported as a saprophyte associated with soil and plant material, but also as a pathogen of tropical fruit trees, causing cushion galls or stem dieback. The objectives of this study were to characterize isolates of F. decemcellulare from different hosts and substrates by means of laboratory crosses, phylogenetic analyses, and pathogenicity tests. Among 67 isolates evaluated, nine were homothallic and produced four ascospores per ascus. The mating types of the remaining isolates were determined and those of opposite types were crossed using each isolate as a female and male parent. Approximately 1590 crossings were performed, and 54 were fertile yielding eight ascospores per ascus. Two isolates from Mexico formed fertile perithecia when crossed with three of the Brazilian isolates, showing that there is no reproductive barrier between these populations. Phylogenetic analyses performed with partial sequences of four genes (tef-1α, rpb2, acl1 and ITS+28S rDNA) grouped heterothallic isolates obtained from cocoa, mango and Paullinia cupana in one distinct clade. Homothallic isolates formed four distinct phylogenetic lineages. Selected heterothallic strains, obtained from cocoa and mango, induced gall symptoms in inoculated cocoa plants. Our findings show that isolates associated with galls belong to a distinct phylogenetic and biological species. There is evidence that F. decemcellulare represents a species complex. (Funding: CNPq ED 15/2009)