Damping-off of soybean caused by Pythium myriotylum in Japan
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Damping-off of soybean caused by Pythium myriotylum in Japan Keisuke Tomioka • Toshiaki Takehara Hideki Osaki • Hiroyuki Sekiguchi • Koji Nomiyama • Koji Kageyama
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Received: 20 September 2012 / Accepted: 4 January 2013 / Published online: 5 February 2013 Ó The Phytopathological Society of Japan and Springer Japan 2013
Abstract Severe rotting and blight of seedlings of soybean, Glycine max (L.) Merr., were found in Hiroshima Prefecture in the southwest region of Japan in July 2009. A filamentous microorganism, isolated repeatedly from the diseased seedlings and identified as Pythium myriotylum, was demonstrated to be pathogenic to seedlings of soybean. The disease was new in Japan, and we propose to include this oomycete as one of the pathogens causing damping-off of soybean. Keywords Damping-off Glycine max New plant disease in Japan Pythium myriotylum Soybean
Soybean, Glycine max (L.) Merr., is an important crop for food and agriculture. In Japan, it is deeply rooted in Japanese food culture in products such as soy sauce, miso, tofu and natto. The Western Region Agricultural Research Center of National Agriculture and Food Research Organization is conducting cultivation trials for stable highyields of soybean in open fields in Fukuyama City, Hiroshima Prefecture in the southwestern region of Japan. Soybean as well as rice and wheat had been rotationally All authors contributed equally to this work. K. Tomioka (&) T. Takehara H. Osaki H. Sekiguchi K. Nomiyama Western Region Agricultural Research Center, National Agriculture and Food Research Organization, Fukuyama 721-8514, Japan e-mail: [email protected] K. Kageyama Division of Vegetation Resources and Functions, River Basin Research Center, Gifu University, Gifu 501-1193, Japan
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cultivated in the fields, which were originally rice paddies. Severe rot and blight on seedlings of soybean were found in the fields days after being drenched by a heavy rain during trials in July 2009. The incidence of damaged seedlings varied from 4.8 to 13.5 % depending on the field. We isolated and identified the causal pathogen and reisolated the pathogen from symptomatic host plants after inoculation with the isolate to confirm pathogenicity and characteristics of the causal agent. Water-soaked, dark brown, irregular lesions appeared on stem bases of seedlings that had grew from seeds treated with thiuram as a seed protectant (Fig. 1a–c). The lesions gradually enlarged toward the upper stems, seed leaves and primary leaves (Fig. 1b). The affected seedlings softened and turned dark brown, resulting in early death. Roots of the diseased plants had rotted and mostly disappeared (Fig. 1c). When browned segments of stem bases from diseased seedlings were placed on apricot medium after being surface-disinfected with 70 % ethanol for 30 s, an oomycete with protoplasmic streaming was isolated at the rate of 40 % of the segments, 1 day after incubation at 25 °C in the dark. A representative isolate, GF237 (FOEAS4), of the oomycete obtained by single-hy
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