Post-harvest sour rot in sweet potato is caused by Geotrichum candidum in Brazil

The sweet potato ( Ipomoea batatas (L.) Lam) is a common crop species in Brazil. Factors limiting its cultivation include root rot. Sweet potato roots showing rot symptoms were collected from the state of Pernambuco in Northeastern Brazil. Soft necrotic lesions along the roots, with the presence of white mycelium under the lesions and a strong odor were noted. Seven fungal isolates were obtained which showed white mycelia with hyphae fragmenting into arthroconidia. To determine the identity of the fungi, DNA was extracted and used in PCR reactions. PCR products were sequenced from the gene regions D1/D2 in 26S rRNA and compared to sequences in GenBank using BLASTn. Based on molecular results and phylogenetic analyses, the fungi were identified as Geotrichum candidum . Pathogenicity tests were performed which confirmed Koch's postulates. This study represents the first report of Geotrichum candidum causing sweet potato sour rot in Brazil.