Occurrence of leaf spot caused by Nigrospora oryzae on red elephant grass in Chongqing, China
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Occurrence of leaf spot caused by Nigrospora oryzae on red elephant grass in Chongqing, China Yu-Zhu Han 1 & Zi-wei Fan 1 & Wei He 2 & Jian Zhang 2 Received: 8 October 2019 / Accepted: 6 February 2020 # Società Italiana di Patologia Vegetale (S.I.Pa.V.) 2020
Keywords Leaf spot disease . Nigrospora oryzae . Pennisetum purpureum
Red elephant grass (Pennisetum purpureum Schum. cv. Red) is an important high-yielding forage and an ornamental grass widely cultivated in South China (Li et al. 2015). In September 2018, 10–45% incidence of a leaf spot symptom was observed on red elephant grass in several fields for feeding beef cattle in the Rongchang district and Fengdu County, Chongqing, China. Infected leaves exhibited small, irregular, white to brown spots, measuring 1 to 2 mm in diameter, and gradually increased in size and number with age of the plant. In severe infections, the spots frequently coalesced, causing the leaf to become partial blighted. A fungus like Nigrospora sp. was consistently isolated. The color of the colonies on PDA was white with a regular circular shape at the early stage, becoming grey to darker grey with age. Hyphae were branched, septate, smooth, hyaline, 2–6 μm diam. Conidiophores were flexuous or straight, pale brown, smooth, 3–7 μm diam. Single-celled conidia were in globose or subglobose shape, with a diameter of 10–14 μm. To further confirm identification, ITS region of rDNA, partial TUB2 and EF genes were amplified with primers ITS1/4, Bt-2a/2b and EF1-728F/986R, respectively (Wang et al. 2017). By BLASTn, DNA sequences from ITS and TUB2 were 100% identical to those of N. oryzae (MK311280.1 and KY019605.1). The EF sequence showed 99.6% identity with that of N. oryzae (KY019413.1). The representative sequences Yu-Zhu Han and Zi-wei Fan contributed equally to this work.
were deposited in GenBank (accession No. MK543235, MK550707, MK550708). Based on morphology and nucleotide homology, the associated fungus was confirmed to be N. oryzae. Pathogenicity tests were performed on 10 heathy, 2-month-old potted red elephant grass plants by brush inoculation of a conidial suspension (approximately 106 conidia/ mL). 7–10 days after inoculation, similar symptoms were observed on 90% of inoculated leaves. N. oryzae was consistently reisolated only from inoculated leaves to fulfill the Koch’s postulates. In China, this pathogen was previously reported on wild Pennisetum purpureum in Hong Kong in 2000 and 2001 (Lu et al. 2000; Wong and Hyde 2001). To our knowledge, this is the first report of N. oryzae causing leaf spot on P. purpureum cultivated in Chongqing, China. Funding information National Key research and development Program Grant/Award Number: 2018YFD0501705. Chongqing Pratacultural Engineering Technology Research Center Grant/Award Number: cstc2017yfpt_gcjsyjzx0003.
Compliance with ethical standards Conflict of interest The authors declare that they have no conflict of interest. Ethical approval This article does not contain any studies with human participants or animals perf
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