, 2000; Park et al., 2003; Tanaka, 2004; Wanner, 2006; St-Onge et al., 2008; AG-014699 in vitro Zhao et al., 2008). Scab disease harms a broad range of root crops, including potato, sweet potato, radish, carrot, sugar beet, and burdock (Loria et al., 1997), with potato scab disease especially causing large economic losses. Diseased potato tubers exhibit characteristic dark-brown, corky lesions. The ugly symptoms of the disease reduce the market value of crops,

causing economic difficulties for potato producers. The causative agents of potato scab disease are multiple species of the genus Streptomyces. Streptomyces scabiei, Streptomyces acidiscabiei, and Streptomyces turgidiscabiei are the most studied and well-known causal agents (Lambert & Loria, 1989a, b; Miyajima et al., 1998; Kers et al., 2005). To date, these are the only three species of potato scab pathogens reported in Japan. Recent studies

have shown a correlation between the amounts of these pathogens in soils and the incidence of the disease (Koyama et al., 2006; Manome et al., 2008), suggesting that decreasing the quantity of the pathogens in soils could mitigate scab disease damage. Over the decades, physicochemical approaches have been applied to control pathogens and scab disease. For example, methods to reduce soil pH were conventionally used to suppress the disease by inhibiting pathogen growth (Lacey & Wilson, 2001). Soil fumigation using agents Epigenetics Compound Library clinical trial such as chloropicrin (trichloronitromethane), which is detrimental to animal and human health (Ristaino & Averre, 1992), was also adopted to control potato scab disease. Biological control using antagonistic microorganisms is a sustainable and environmentally acceptable management method for numerous pathogens (Punja & Utkhede, 2003; Tian et al., 2007). In the case of potato scab disease, previous studies have mainly focused on antagonists against S. scabiei. Several Streptomyces sp. have cAMP been shown to inhibit the growth of S. scabiei (Hayashida et al., 1988; Lorang et al., 1995; Beausejour et al., 2003). Bacillus sp. was also revealed to inhibit the growth and sporulation

of S. scabiei by secreting extracellular compounds (Han et al., 2005). McKenna et al. (2001) reported biological control using a bacteriophage infecting S. scabiei. However, there has only been one report of antagonists against S. turgidiscabiei (Hiltunen et al., 2009), and little is known about antagonists against S. acidiscabiei. In addition, as far as we know, no reports have revealed a fungal antagonist against potato scab pathogens. Fungi are common inhabitants of soil environments, and are generally easy to handle and mass-produce. For this reason, many biological agents using fungi are commercially available for the control of plant diseases, although potato scab disease is not one of them (Punja & Utkhede, 2003; Fravel, 2005; Han et al., 2005). It is also significant that fungi tend to be more resistant than bacteria to acidic conditions (Thompson et al.