Identificação e diversidade genética de isolados de Fusarium associados à podridão em melão no nordeste brasileiro

Abstract

Melon is a crop of great prominence in agribusiness in the Brazilian Northeast, being the second most exported fruit. However, there are obstacles to commercialization, such as post-harvest diseases, causing considerable losses. Among the diseases of melon, Fusarium rot outstands by reducing the shelf life of the fruits. This study aimed to prospect Fusarium isolates from melons in the main producing areas of Northeast Brazil, to characterize isolates morphologically, biologically and phylogenetically, to evaluate the pathogenicity of the isolates, as well as to elucidate the genetic diversity of the most recurrent species in the areas. The isolates were obtained through direct and indirect isolations, and submitted to monosporic cultures. Nucleotide sequences of the elongation factor 1-alpha (TEF1) and RNA polymerase II (RPB2) genes were used in maximum likelihood phylogenetic analyzes and Bayesian inference. The sexual compatibility of the FIESC complex species and the genetic diversity of F. falciforme were tested using inter simple sequence repeat (ISSR) markers. A total of 140 isolates of the genus Fusarium were obtained, all pathogenic, belonging to seven different species complexes, among which, two never before associated with melon rot, F. dimerum species complex (FDSC) and F. sambucinum species complex (FSAMSC). There was an association of 23 phylospecies with melon rot, with 16 new world reports. The sexual stage of the species F. sulawesiense and F. pernambucanum was induced in the laboratory, and this is the first time that the sexual reproduction of F. sulawesiense has been observed. Polymorphism was found in the F. falciforme isolates and the formation of 3 distinct clusters directly related to geographic location. It was possible to verify genetic variations between collection sites, high genetic diversity among isolates collected in the states of Rio Grande do Norte and Ceará, with 30 haplotypes. The results of this study proved that several species are associated with Fusarium rot of melons in Northeast Brazil, and so far we are unaware of another pathosystem with so many species associated with the same disease, thus strengthening the importance of a representative sample in studies of the etiology of diseases of plants.