FIRST REPORT OF SWEET POTATO LEAF SPOT CAUSED BY NEOPESTALOTIOPSIS ELLIPSOSPORA IN GUIZHOU PROVINCE, CHINA

Abstract

During May to September 2015, sweet potato [Ipomoea batatas (L.) Lam.] plants with leaf spot symptoms were observed in Guizhou Province, China, at 25°12'06.8"N 107°57'25.3"E with about 15% incidence. The disease first appeared as small, round, yellow specks on leaves. Successively, the affected areas became necrotic and gradually enlarged to 3-9 mm in diameter. The fungal species present on the sample was isolated onto PDA using a single spore culture technique as described in Chomnunti et al. (2014). Colonies on PDA attained 30–40 mm in diameter after 7 days at 25°C, producing a dense aerial mycelium on the surface. Conidia were ellipsoid, 4-septate, 20.0–26.0 × 5.0–7.5 μm. Apical and basal cells were hyaline, whereas the three median cells were versicolored. Each apical cell had 3 tubular apical appendages, 7–24 μm long. The conidial dimensions of these isolates correspond to Pestalotiopsis ellipsospora Maharachchikumbura & K.D. Hyde (Maharachchikumbura et al., 2012). Sequence data for the rDNA internal transcribed spacer (ITS), Beta tubulin (TUB) and partial translation elongation factor 1-alpha (TEF) of three N. ellipsospora isolates were deposited in GenBank under the accession Nos. KU500017 to KU500019 (ITS), KU500010 to KU500012 (TUB) and KU500013 to KU500015 (TEF). A BLAST search showed 100% similarity with N. ellipsospora isolate (CBS 115113) sequences deposited in GenBank. The disease was reproduced on sweet potato healthy leaves inoculated using either 3-day-old mycelial discs or inoculum (1× 106 conidia/ml) prepared by scraping conidia from 10-day-old cultures on PDA plates. To our knowledge this is the first report of Neopestalotiopsis causing leaf spot on sweet potatoes in the world.