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ARS Home » Southeast Area » Stoneville, Mississippi » Crop Genetics Research » Research » Publications at this Location » Publication #355968
Title: Occurrence of cotyledon spot on soybean caused by Fusarium oxysporum in China

Author
item LI, YONGGANG - Northeast Agricultural University, China
item JIANG, DAN - Northeast Agricultural University, China
item Li, Shuxian
item JIANG, WANYI - Northeast Agricultural University, China
item WANG, RUITING - Northeast Agricultural University, China
item JI, PINGSHENG - University Of Georgia
item PAN, HONGYU - Jilin University

Submitted to: Plant Disease
Publication Type: Research Notes
Publication Acceptance Date: 4/27/2019
Publication Date: 11/4/2019
Citation: Li, Y., Jiang, D., Li, S., Jiang, W., Wang, R., Ji, P., Pan, H. 2019. Occurrence of cotyledon spot on soybean caused by Fusarium oxysporum in China. Plant Disease. 103(11):2967. https://doi.org/10.1094/PDIS-01-19-0043-PDN.
DOI: https://doi.org/10.1094/PDIS-01-19-0043-PDN

Interpretive Summary: Soybean is an important food and oil crop in Northeast China. During June 2018, the disease cotyledon spot was observed on soybean in Acheng district, Heilongjiang province, China. The disease occurred on approximately 6% of soybean cotyledons in several commercial fields. Initial symptoms were irregular brown sunken spots on soybean cotyledons, which enlarged gradually. A fungus was isolated and identified as Fusarium oxysporum based on its structure and DNA sequences. In greenhouse tests, all plants treated with the pathogen showed disease symptoms, while non-treated plants were healthy. This is the first report confirming F. oxysporum causing cotyledon spot on soybean in China. Soybean is the main oil crop grown in Northeast China and proper disease management practices will be needed to reduce soybean yield losses caused by this new disease.

Technical Abstract: Soybean [Glycine max (L.) Merr.] is an important food and oil crop in Northeast China. During June 2018, cotyledon spot was observed on soybean in Acheng district, Heilongjiang province, China. The disease occurred on approximately 6% of soybean cotyledons in several commercial fields. Initial symptoms were irregular brown sunken spots on soybean cotyledons, which enlarged gradually from small to large (1 to 15 mm in diameter). Infected soybean cotyledon tissues were surface disinfested in 0.5% NaOCl for 3 min, rinsed for 3 times in sterile distilled water and cultured on 2% potato dextrose agar (PDA) at 26°C. Six fungal isolates with identical characteristics were isolated. They produced whitish aerial mycelium with pink to purple pigments on PDA. Based on the morphological characteristics of microconidia, macroconidia, and chlamydospores, the fungal isolates were identified as Fusarium oxysporum. MegaBLAST analysis of the ITS sequences of two single spore isolates showed that it had 99% similarity to a F. oxysporum strain G01 (accession no. KT884661.1). Pathogenicity of a representative isolate Ziye2 was evaluated in greenhouse by inoculating soybean seedling cotyledons (cv. Suinong 25). All inoculated cotyledons showed symptoms identical to those observed in the field. No disease occurred on the control cotyledons without inoculation. The fungus was reisolated from diseased cotyledons and confirmed to be F. oxysporum based on morphological characteristics and pathogenicity tests. To our knowledge, this is the first report confirming F. oxysporum causing cotyledon spot on soybean in China. Soybean is the main oil crop grown in Northeast China and occurrence of the new disease caused by F. oxysporum should give full consideration for the use of proper disease management to reduce soybean yield losses.