Identificação de espécies fúngicas associadas à cultura da pitaia

Abstract

The dragon fruit (Hylocereus sp.) is a fruit that belongs to the Cactaceae family, which has approximately 100 genera and 1,500 species. The diversity of exotic fruits such as dragon fruit has been gaining ground in the national market. The increase in demand for the product, fruits with a high selling price and access to updated cultivation information favor the growth of the activity in the country. However, some diseases have been associated with this crop, especially fungal etiological agents that cause anthracnose and rot. These diseases are associated with cladodes and dragon fruit fruits. However, knowing the etiological agent is essential for effective disease control. Therefore, the objective of the work was to identify fungal species that affect dragon fruit crops through molecular, morphological and cultural characteristics. Dragon fruit cladodes were collected in the state of Alagoas, in commercial plantations and in an experimental area located on the Engineering and Agricultural Sciences Campus of the Federal University of Alagoas. The fungal isolates were obtained from samples of cladodes with symptoms of anthracnose and rot, using the indirect isolation method and cultivated on potato-dextrose-agar medium. After seven days, the fungal isolates were previously identified to the genus level, using taxonomic keys existing in the literature. To test the pathogenicity of the isolates, asymptomatic dragon fruit cladodes were used. The isolates considered pathogenic were subjected to molecular, morphological and cultural characterization studies of fungal genera. Firstly, DNA extraction and amplification of partial sequences of the ITS region and of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and β-tubulin genes were carried out for Colletotrichum isolates and translation elongation factor 1-α (TEF -1α) and RPB2 for Fusarium isolates. A total of 36 fungal isolates were obtained, of which 14 belong to the genus Colletotrichum and 22 to the genus Fusarium. Colletotrichum cultures presented mycelium varying between shades of gray, orange and white, with hyaline, non-septate, cylindrical conidia and round ends. Fusarium isolates produced mycelium in shades of white, pink and orange, with hyaline macro- and microconidia and the presence of chlamydospores. The observation of morphological and cultural characteristics together with phylogenetic analyzes allowed the Colletotrichum isolates to be grouped into the C. gloeosporioides and C. truncatum complexes. Fusarium isolates were grouped with species from the F. incarnatum–equiseti complex, F. fujikuroi and F. oxysporum. Key words: Cactaceae; Fungal diseases; Pathogenicity; Colletotrichum; Fusarium.