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United States Department of Agriculture

Agricultural Research Service

Research Project: REDUCING SOYBEAN YIELD LOSSES THROUGH GENETIC IMPROVEMENT Title: First report of Phomopsis Seed Decay of soybeans caused bt Phomopsis longicolla in South China

Authors
item Shan, Zhihui -
item Li, Shuxian
item Liu, Yan -
item Yang, Zhonglu -
item Yang, Cunyi -
item Sha, Aihua -
item Chen, Haifeng -
item Chen, Shuilian -
item Zhou, Xin-An -

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 19, 2012
Publication Date: November 1, 2012
Citation: Shan, Z., Li, S., Liu, Y., Yang, Z., Yang, C., Sha, A., Chen, H., Chen, S., Zhou, X. 2012. First report of Phomopsis Seed Decay of soybeans caused bt Phomopsis longicolla in South China. Plant Disease. 96 (11):1693.

Interpretive Summary: Soybean Phomopsis seed decay (PSD) causes poor seed quality and suppresses yield in most soybean-growing areas in the world. The disease is caused primarily by a fungus (mold). During the spring of 2010, soybean seeds without symptoms were planted in the fields but had poor emergence in South China. Randomly collected seeds from three locations in Guangzhou, Nanchang and Wuhan were examined for morphology and DNA sequences of the mold obtained from the seed. Results showed that seed was infected by the PSD-causing fungus. In addition, greenhouse tests were performed to confirm the fungus causes the disease. All seedlings inoculated with the fungus showed browning, stem wilt, and lesions, while non-inoculated seedlings were healthy without symptoms. This is the first report of Phomopsis seed decay of soybean in South China.

Technical Abstract: Soybean Phomopsis seed decay causes poor seed quality and suppresses yield in most soybean-growing areas in the world. The disease is caused primarily by Phomopsis longicolla. During the spring of 2010, soybean seeds without symptoms were planted in the fields but had poor emergence in South China. Randomly collected seeds from three locations in Guangzhou, Nanchang and Wuhan were surface-disinfected with 1% sodium hypochlorite for 12 minutes, rinsed in sterile distilled water for 3-4 times, placed on 2% agar, and then incubated at 26°C under 16/8h photoperiod for 3-4 days. About 10-20% of the seeds produced white hyphae that spread rapidly and covered the whole seed. The hyphae from three fungal isolates was transferred to potato dextrose agar (PDA), and incubated at 26°C in dark. Conidia formed in 3-4 weeks, were elliptical with two oil drops at both ends and hyaline, the size was 6.2-7.2 × 2.6-3.2 µm. The cultural morphology of the isolates fit the description of Phomopsis longicolla Hobbs. The ribosomal internal transcribed spacer (ITS) from three isolates were sequenced. BLAST analysis of the obtained ITS sequences showed that the isolates had 100% nucleotide sequence identity with P. longicolla (GenBank Accession No. AY857868.1, FJ462759.1, and HQ130441.1). Pathogenicity tests were conducted on 2-weeks-old soybean seedlings. All inoculated seedlings showed browning, stem wilt, and the lesions extended to hypocotyls. The non-inoculated seedlings were healthy without symptoms. P. longicolla was reisolated from the infected seedling tissues. P. longicolla has been reported in U.S. and Northeast China. This is the first report of P. longicolla causing Phomopsis seed decay of soybean in South China.

Last Modified: 12/19/2014
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