**4. Future prospect (potential of biological control agents for SCN and other complex diseases)**

Fungi traditionally known for their entomopathogenic characteristics, such as *Beauveria bassiana* and *Lecanicillium* spp., have recently been shown to engage in plant-fungus interactions (Vega, 2008; Vega et al., 2008), and both have been reported to effectively suppress plant disease (Goettel et al. 2008; Ownley et al., 2004, 2008). Biological control of plant pathogens usually refers to the use of microorganisms that reduce the disease causing activity or survival of plant pathogens. Several different biological control mechanisms against plant pathogens have been identified. The biocontrol organism is directly involved in some mechanisms such as antibiosis, competition, and parasitism. With other modes of biological control, such as induced systemic resistance and increased growth response, endophytic colonization by the biocontrol organism triggers responses in the plant that reduce or alleviate plant disease (Ownley et al., 2010).

*Lecanicillium* spp. have activity against numerous phytopathogenic fungi including powdery mildews (Verhaar et al., 1997, 1998; Askary et al., 1997, 1998, 1999; Dik et al., 1998; Miller et al., 2004), rusts (Spencer and Atkey, 1981; Leinhos and Buchenauer, 1992) green molds (Benhamou and Brodeur, 2000) and *Pythium* (Benhamou and Brodeur, 2001). Fungi that may control phytopathogenic fungi can act through antibiosis and mycoparasitism (Kiss, 2003). Some *Lecanicillium* isolates act as mycoparasites, attaching to powdery mildew mycelia and conidia, producing enzymes such as chitinase, that allow penetration of the mildew spores and hyphae, killing the pathogen (Askary et al., 1997). Leinhos and Buchenauer (1992) demonstrated that several *Lecanicillium* spp. were able to penetrate and colonize uredial sori of *Puccinia coronata*. In *Penicillium digitatum*, the mode of action was attributed to changes in host cells prior to contact by the *Lecanicillium* spp. (Benhamou and Brodeur, 2000) while in *P. ultimatum*, in addition to mycoparasitism of the plant pathogen, the mode of action was linked to colonization of host plant tissues, triggering a plant defense reaction (Benhamou and Brodeur, 2001). Hirano et al. (2008) found that applying *L. muscarium* blastospores to cucumber roots induced systemic resistance. *L. muscarium* pre-inoculated plants suffered significantly fewer lesions and reduced disease severity compared with non-inoculated plants. Kusunoki et al. (2006) and Koike et al. (2007b) found that root treatment with *L. muscarium* reduced disease incidence and wilting score in other soil-borne disease combinations such as tomato—*Verticillium dahliae*, Japanese radish—*V. dahliae*, and melon— *Fusarium oxysporum* f.sp. *melonis.* 

In the case of soilborne pathogens, further opportunities exist for interactions with other microorganisms occupying the same ecological niche. The significant role of nematodes in the development of diseases caused by soilborne pathogens has been demonstrated in many crops throughout the world. In many cases, such nematode–fungus disease complexes involve root-knot nematodes (*Meloidogyne* spp.), although several other endoparasitic (*Globodera* spp., *Heterodera* spp., *Rotylenchulus* spp., *Pratylenchus* spp.) and ectoparasitic (*Xiphinema* spp., *Longidorus* spp.) nematodes have been associated with diseases caused by soilborne fungal pathogens (Back et al., 2002). In the case of SCN, Sudden Death Syndrome (SDS) caused by *F. solani* is a major disease of soybean which, among other symptoms, induces root rot, crown necrosis, interveinal chlorosis, defoliation and abortion of pods (Rupe, 1989; Nakajima *et al*., 1996). Recent research on SDS has focused on identifying genes for dual resistance against both nematode and fungus (Chang *et al*., 1997; Meksem *et al*., 1999; Prabhu *et al*., 1999).

It is known that entomopathogenic *Lecanicillium* spp. have antagonistic effects to soil-borne fungi such as *Fusarium oxysporum*, *F. solany*, *Pythium* spp. and *Verticillium dahlia* (Koike et al., 2006, Goettel et al., 2008). Therefore, it might be possible to develop *Lecanicillium* hybrid strains with potential for biological control of a complex of plant diseases, plant parasitic nematodes and insect pests.
