Stemphylium leaf spot of asparagus caused by Stemphylium lycopersici
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Stemphylium leaf spot of asparagus caused by Stemphylium lycopersici Keisuke Tomioka1 · Daigo Abe2 · Akira Kawaguchi1 · Akira Kawakami1 · Akira Masunaka1 · Shinsuke Mori1 · Koji Nomiyama1,3 · Hiroyuki Sekiguchi1 Received: 6 April 2020 / Accepted: 29 May 2020 © The Phytopathological Society of Japan and Springer Japan KK, part of Springer Nature 2020
Abstract Cercospora blight caused by Cercospora asparagi routinely developed on asparagus in certain plastic hoop houses in Hiroshima Prefecture in western Japan every July to November. Stemphylium lycopersici was repeatedly isolated with C. asparagi from the blighted leaves in September 2016 and shown to be another causal agent of the blighting and added as another pathogen causing Stemphylium leaf spot of asparagus. Keywords Asparagus · New disease · Stemphylium leaf spot · Stemphylium lycopersici We occasionally observed an already-known disease, Cercospora blight caused by Cercospora asparagi Sacc., on asparagus (Asparagus officinalis L.) in certain plastic hoop houses in Hiroshima Prefecture in western Japan every July to November. In September 2016, we repeatedly isolated another fungus from the blighted leaves and confirmed that it was also pathogenic to asparagus. Parts of this paper were presented elsewhere (Tomioka et al. 2017, 2019). The main symptom after natural infection was blighting of leaves (strictly “phyllodes or cladophylls), on main stalks grown for development of roots and crowns (Fig. 1a–c). Yellowish to brownish lesions on leaves gradually enlarged and coalesced, resulting in early blight and fall of the affected leaves. Conidiophores and conidia of not only Cercospora sp. but also Stemphylium sp. frequently appeared on the lesions under moist conditions (Fig. 1d, e). Both fungi were often isolated from the same lesions. The Cercospora species was identified as C. asparagi, already known as a pathogen of Cercospora blight, called kappan-byo in Japanese * Keisuke Tomioka [email protected] 1
Western Region Agricultural Research Center, National Agriculture and Food Research Organization, Fukuyama 721‑8514, Japan
2
Western Region Agricultural Research Center, National Agriculture and Food Research Organization, Zentsuji 765‑8508, Japan
3
Present Address: Institute of Vegetable and Floriculture Science, National Agriculture and Food Research Organization, Tsu 514‑2392, Japan
(Goto 1925; Han et al. 2013; Hay et al. 2017; Takimoto 1921; The Phytopathological Society of Japan 2020). Representative isolate SOasp2 of Stemphylium sp., obtained from a lesion by single-conidium isolation, formed dark olivaceous colonies with grayish, aerial mycelia on potato dextrose agar (PDA) at 5–35 °C in the dark with maximum growth of 4.7 mm/day at 28 °C (Fig. 1f, g). Conidiophores and conidia of the isolate were formed on V-8 juice agar (V8) under 12 h/day irradiation of black light (FL20SBLB, peak emission 352 nm, TOSHIBA, Tokyo, Japan) for more than 5 days (Fig. 1h–j), and their morphologies were same as those on lesions after natur
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