Fusarium species pathogenic to Urochloa brizantha in the north de Minas Gerais, Brazil

Abstract In Brazil, the sudden death disease of Marandu grass (Urochloa brizantha cv. Marandu) has caused grassland degradation. In the north of Minas Gerais state, a disease has been reported in pastures with similar symptoms to the sudden death of grasses. Thus, the objectives of this study were (i.) to identify Fusarium species associated with the sudden death disease of Marandu grass using molecular phylogeny and morphological markers and (ii.) to test the pathogenicity of Fusarium isolates on Marandu and Xaraés cultivars. All isolates used in this work were obtained from typical cultures of the genus Fusarium, grown from isolated tissues of Marandu grass with symptoms of the disease, collected in the North region of Minas Gerais, Brazil. Twelve phylogenetic species were identified among the 17 isolates based on comparing partial sequences of the elongation factor 1-α gene (TEF-1-α). These species belong to the F. fujikuroi (FFSC, n = 10) and F. oxysporum (FOSC, n = 5) species complexes. In the pathogenicity test, the isolates induced symptoms of leaf yellowing, shoot drying, and stem rot in the cultivars Marandu and Xaraés, especially the isolates belonging to the FFSC. The Fusarium sp. 4 strain will be described and elevated to the species level, representing a new phylogenetic species in the FFSC. Our study has shown that several species of Fusarium cause pathogenicity to Marandu and Xaraés grasses, which can serve as an inoculum source for crops of great agricultural significance. However, this pathosystem can also harbor new species of Fusarium. In our work, we demonstrated for the first time the pathogenicity of Fusarium species in the cultivars Marandu and Xaraés.