Detection and biocontrol potential of Verticillium leptobactrum parasitizing Meloidogyne spp.

Three isolates of Verticillium leptobactrum proceeding from egg masses of root-knot nematodes(RKN) Meloidogyne spp. and soil samples collected in Tunisia were evaluated against second-stage juveniles (J2) and eggs of M. incognita, to determine the fungus biocontrol potential. In vitro tests showed that V. leptobactrum is an efficient nematode parasite. The fungus also colonized egg masses and parasitized hatching J2. In a greenhouse assay with tomato plants parasitized by M. incognita and M. javanica, V. leptobactrum was compared with isolates of Pochonia chlamydosporia and Monacrosporium sp.,introducing the propagules into nematode-free or naturally infested soils. The V. leptobactrum isolates were active in RKN biocontrol, improving plants growth with a significant increase of tomato roots length, lower J2 numbers in soil or egg masses, as well as higher egg mortalities. In a second assay with M. javanica, treatments with three V. leptobactrum isolates reduced egg masses on roots as well as the density of J2 and the number of galls. To evaluate the fungus capability to colonize egg masses a nested Real-time polymerase chain reaction (PCR) assay,based on a molecular beacon probe was used to assess its presence. The probe was designed on a V. leptobactrum ITS region, previously sequenced. This method allowed detection of V. leptobactrum from egg masses, allowing quantitative DNA and fungal biomass estimations.