Exploring competitiveness and genetic variation in the nematophagous fungusPochonia chlamydosporia var. chlamydosporia and its significance for biological control

Abstract: The fungus Pochonia chlamydosporia var. chlamydosporia is a potential biologicalcontrol agent of plant endoparasitic nematodes. Factors affecting control efficacy include fungusnematodeinteractions, competition between isolates and intra-specific variation withinP. chlamydosporia. All require further investigation. PCR-based DNA fingerprinting techniquescan provide rapid means to examine the genetic variation of fungal isolates from variousgeographical regions and nematode hosts, and also to monitor biocontrol agents after their releaseinto the soil. A series of experiments were conducted under glasshouse and in vitro conditions toassess competitiveness for rhizosphere colonization and egg parasitism of selected Pochoniaisolates of the root-knot (Meloidogyne spp.) and cyst (Globodera spp., Heterodera spp.)nematode biotypes as well as their compatibility for anastomosis. The abundance of Pochoniaisolates in two Portuguese sites under long-term cultivation of horticultural crops (tomato) wasdetermined by plating soil onto selective agar or quantitative PCR with species specific primers;genetic diversity was assessed from ERIC-PCR profiles. Both sites showed a limited diversity ofthe fungus but there were also different parasitic abilities. Isolate biotype selection and theirrelevance to the management of nematode populations are discussed.