Phanerochaete chrysosporium strain B-22, a parasitic fungus infecting Meloidogyne incognita

Abstract

We characterized the parasitism by strain B-22 of Phanerochaete chrysosporium on the eggs, second stage juveniles (J2), and adult females of the root-knot nematode (Meloidogyne Incognita). Strain B-22 had a strong lethal effect against M. incognita J2. The highest corrected mortality was 71.9% at 3 x 108 conidia mL-1. The estimated LC50 value was 0.96 x 108 conidia mL-1. Strain B-22 parasitized M. incognita eggs 2 days after treatment, causing the depression and dissolution of egg shells. The fungal spores parasitized J2 by gathering in the body wall, germinating to develop hyphae, and crossing the juvenile cuticle to dissolve it, thereby causing the 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 in 5 days. Results of greenhouse experiments showed that different concentrations of P. chrysosporium effectively controlled different life stages of M. incognita and root knot symptoms in tomato plants. Moreover, the control efficacy increased with increasing conidial concentration; the best results were achieved with 3 x 108 cfu mL-1. In the roots, the highest inhibition rate was 84.61% for adult females, 78.91% for juveniles, 84.25% for the egg mass, and 79.48% for the gall index. The highest juvenile inhibition rate was 89.18% in the soil. Meanwhile, strain B-22 improved the plant growth. Thus, P. chrysosporium strain B-22 is safe for tomato plants while effectively parasitizing M. incognita, making it a promising biocontrol agent against M. incognita.