Identification and pathogenicity of Botryosphaeriaceae species associated with root and stem rot of sweet potato in Brazil

Abstract The sweet potato ( Ipomoea batatas ) is characterized by the production of tuberous roots rich in starch and is one of the most produced and consumed vegetables in Brazil. Botryosphaeriaceae, among other fungi, are known to cause root and stem rot of sweet potato. However, no representative and accurate study has been performed for the correct identification of these fungal species in sweet potato in Brazil. Therefore, this study aimed to identify the Botryosphaeriaceae species associated with root and stem rot of sweet potato and confirm their pathogenicity. Tuberous roots and stems of sweet potato with rot symptoms were collected in production fields and markets and used for fungal isolations. The identification of fungi was based on the morphology of reproductive structures and phylogenetic analyses of the gene regions ITS, tef1 ‐ α , and rpb2 . The following species were identified: Lasiodiplodia theobromae , L . hormozganensis , Macrophomina phaseolina , M . euphorbiicola , M . pseudophaseolina , and Neoscytalidium dimidiatum . For the pathogenicity test, one representative isolate for each species was inoculated in healthy tuberous roots and in 30‐day‐old healthy seedlings. Black and necrotic lesions on tuberous roots and stems were observed in all replications and resulted in the death of some seedlings. This is the first report of L . hormozganensis , M . pseudophaseolina , and M . euphorbiicola , as causal agents of the stem and root rot of sweet potato and N . dimidiatum as a causal agent of stem rot worldwide.