Diversidade fúngica com ênfase na família Botryosphaeriaceae associadas às manivas-semente de mandioca

Abstract

Cassava (Manihot esculenta Crantz) is considered of great importance in food security, with a tuberous root, rich in starch, and high caloric value. Root and stem rot are diseases that compromise the crop, causing major losses, due to direct losses in production and the spread of pathogens, respectively. Studies have revealed the occurrence of a diversity of phytopathogenic fungi, standing out those of the Botryosphaeriaceae family, associated with stem rot. This work aimed to identify fungal diversity with emphasis on the Botryosphaeriaceae family, associated with cassava seed stems, after disinfection and induction of rot. Fungal isolations were carried out by serial dilution, of the rotten cuttings from Alenquer, Belterra, Curuá, Faro, Itaituba, Juruti, Mojuí dos Campos, Prainha and Santarém municipalities, followed by DNA extraction using the Wizard® Genomic DNA Purification kit. (Promega). To study diversity, identification was carried out by amplification of the ITS region with the universal primers ITS1 and ITS4 and subsequent sending for sequencing, using the Sanger method. The electropherograms were trimmed and edited so that the contigs could be used for identification. Molecular identification was initiated by using Blast and subsequent comparison with standard sequences of the species of the associated genus/section/complex. Phylogenetic analysis of species from the Botryosphaeriaceae family was carried out in the gene regions of the translation elongation factor (TEF 1 – α), RNA polymerase subunit II (rpb2) and internal transcribed spacer (ITS). Eleven genera were identified in the fungal diversity in cassava cuttings (Lasiodiplodia, Neoscytalidium, Fusarium, Penicillium, Aspergillus, Cladosporium, Hyphopichia, Trichoderma, Clonostachys, Diaporthe and Phomopsis). The genus Lasiodiplodia was the most frequent, with at least the species Lasiodiplodia theobromae, L. brasiliensis, L. euphorbiaceicola and L. pseudotheobromae detected, in addition to the species Neoscytalidium dimiditum, distributed differentially among the different communities and municipalities in the western region of Pará, and all isolates of Lasiodiplodia and Neoscytalidium were capable of causing lesions in cassava roots and were reisolated, confirming its pathogenicity. These data demonstrate the importance of healthy propagation material, as pathogens can be disseminated even when asymptomatic and with superficial disinfection treatments.