First report of Macrophomina pseudophaseolina causing stem dry rot in cassava in Brazil
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KeywordsBotryosphaeriaceae Manihot Plant pathogens
Cassava (Manihot esculenta Crantz) is a crop of great economic importance in Brazil, with a production of approximately 20 million tons per year. In 2017, cassava stems with symptoms of dry rot were observed in propagation material in a production field in Janaúba, Minas Gerais State of Brazil. The stems contained black necrotic areas with abundant microsclerotia formation, indicative of infection by a member of the Botryosphaeriaceae. One microsclerotium was placed on PDA (potato dextrose agar) producing fast growing gray to black mycelia. Fungus sporulation induction was performed as described in Sarr et al. (2014), however, the isolate produced only black and hard microsclerotia, typical of the genus Macrophomina. The gene regions translation elongation factor 1 α (TEF1- α) and internal transcribed spacer (ITS) were sequenced and deposited in GenBank (accession Nos. MK439948; MK433559). In a Bayesian phylogenetic analysis, the isolate grouped with M. pseudophaseolina CPC21417 (ex-type) (KF952153; NR147351) with 100% of support value. The isolate was deposited in the culture collection “Micoteca URM Profa. Maria Auxiliadora Cavalcanti” at the Universidade Federal de Pernambuco (Recife, Brazil), as URM8032. Pathogenicity tests were performed in cassava stems, using rice grain colonized with the fungus and deposited in superficial wounds made at the base of 20-day-old seedlings. Healthy cassava roots, superficially wounded with a scalpel, were also inoculated with colonized rice grains and maintained for seven days in plastic boxes in a moist chamber. Both tests confirmed the pathogenicity of M. pseudophaseolina in cassava. Recently, this species was reported in several oil crops in Brazil (Machado et al. 2018). However, to our knowledge, this is the first report of M. pseudophaseolina causing disease in cassava in the world.
This study was funded by Fundação de Amparo à Ciência e Tecnologia do Estado de Pernambuco (FACEPE), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq).
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Conflict of interest
The authors declare that they have no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
Informed consent was obtained from all individual participants included in the study.
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