Phanerochaete chrysosporium strain B-22, a nematophagous fungus parasitizing Meloidogyne incognita.

The root-knot nematode Meloidogyne incognita has a wide host range and it is one of the most economically important crop parasites worldwide. Biological control has been a good approach for reducing M. incognita infection, for which many nematophagous fungi are reportedly applicable. However, the controlling effects of Phanerochaete chrysosporium strain B-22 are still unclear. In the present study we characterized the parasitism of this strain on M. incognita eggs, second-stage juveniles (J2), and adult females. The highest corrected mortality was 71.9% at 3 × 108 colony forming units (CFU) mL-1 and the estimated median lethal concentration of the fungus was 0.96 × 108 CFU mL-1. Two days after treatment with Phanerochaete chrysosporium strain B-22 eggshells were dissolved. A strong lethal effect was noted against J2, as the fungal spores developed in their body walls, germinated, and the resulting hyphae crossed the juvenile cuticle to dissolve it, thereby causing shrinkage and deformation of the juvenile body wall. The spores and hyphae also attacked adult females, causing the shrinkage and dissolution of their bodies and leakage of contents after five days. Greenhouse experiments revealed that different concentrations of the fungal spores effectively controlled M. incognita. In the roots, the highest inhibition rate for adult females, juveniles, egg mass, and gall index was 84.61%, 78.91%, 84.25%, and 79.48%, respectively. The highest juvenile inhibition rate was 89.18% in the soil. Phanerochaete chrysosporium strain B-22 also improved tomato plant growth, therefore being safe for tomato plants while effectively parasitizing M. incognita. This strain is thus a promising biocontrol agent against M. incognita.