Liquid culture production of microsclerotia of Purpureocillium lilacinum for use as bionematicide

The production of microsclerotia by Purpureocillium lilacinum in liquid culture for use as a biocontrol agent for management of root-knot nematode, Meloidogyne incognita, has not been described. To investigate the potential for microsclerotia production, P. lilacinum strain CQPL01 was cultured in liquid media containing various concentrations of ferrous sulphate. Under these conditions mycelia began to form microsclerotia. The maximum yield (11.8 x 10(4) microsclerotia ml(-1)) was obtained in medium containing 0.2 g l(-1) ferrous sulphate and the greatest production of conidia (1.3 x 10(8) conidia g(-1)) was obtained by the culture of air-dried microsclerotia in aqueous agar medium. Subsequently, the viability of microsclerotia, including stress resistance, storage stability and pathogenicity against M. incognita, was investigated. The microsclerotia exhibited excellent nematophagous ability and greater thermotolerance and UV-B radiation tolerance compared to conidia. These results suggested that microsclerotia propagules might be superior to the use of conidia in P. lilacinum biocontrol products.