Variability in aggressiveness of a Fusarium guttiforme subpopulation associated with pineapple fusariosis in the North region of the state of Rio de Janeiro, Brazil

The genus Fusarium is largely known due to its economical relevance, affecting several agronomically important crops. The pineapple fusariosis, caused by F. guttiforme, is among the most important diseases in pineapple (Ananas comosus var. comosus (L.) Merrill Cppens & Leal) worldwide, causing seedling and fruit losses estimated in 20% and 40%, respectively. Because this pathogen can potentially induce 100% production losses, studies seeking efficient and long-lasting disease management strategies are required. This study aimed to assess the Fusarium species diversity associated with pineapple fusariosis in the North region of the state of Rio de Janeiro, Brazil. Symptomatic pineapple fruit were collected from different producing areas, and 20 Fusarium isolates were obtained through indirect isolation. The proper fungal species identification was carried out based on nucleotide sequences of the translation elongation factor 1α (tef1) and β-tubulin (tub2) genomic regions. Also, the aggressiveness of Fusarium isolates was evaluated through inoculation of fruit and leaves of the susceptible pineapple cultivar Pérola. The Bayesian phylogenetic analysis reinforced that Fusarium guttiforme was the only species identified infecting pineapple in the North of Rio de Janeiro, with the new isolates forming a monophyletic group with a previously reported F. guttiforme isolate. Although the close genetic relationship observed among tef-1α and β-tub2, at 99.1-100.0% nucleotide identity, differences in aggressiveness were observed. All isolates of F. guttiforme caused lesions on leaves and fruits; however, nine isolates stood out as more aggressive towards fruit, and two as more aggressive on the leaves. The F. guttiforme isolates identified here can be used as inoculum sources to evaluate putative genetic resistance in pineapple breeding programs.