The filamentous fungi Trichoderma spp. is currently developed as biocontrol agents against many plant pathogens. Recent studies have shown that these fungi are able to infect nematode eggs and juveniles. In this research, biological control of root-knot nematode (Meloidogyne javanica) by Trichoderma harzianum BI was investigated in greenhouse and laboratory experiments. Results showed that different concentrations (102–108 spores/ml) of T. harzianum BI decreased nematode infection and other parameters significantly, compared to control. T. harzianum BI was able to penetrate nematode egg mass matrix and significantly decreased nematode egg hatching level. Specific activities of resistance-related enzymes, namely peroxidase (POX), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) increased significantly in T. harzianum BI inoculated plants. Maximum activities of POX, PPO and PAL were observed at the 5, 5 and 6 days after inoculation, respectively. Chitinase activity was also increased in culture filtrates of T. harzianum BI grown on wheat bran moistened with salt solution supplemented with colloidal chitin or nematode eggs. Maximum activity of chitinase was recorded at the 4 days after inoculation, in media supplemented with colloidal chitin (1.15 U/min per ml) and nematode eggs (0.85 U/min per ml). Results suggested that direct parasitism of eggs through the increase in extracellular chitinase activity, which would be indicator of eggs infection capability, and inducing plant defense mechanisms leading to systemic resistance are two main suppression mechanisms used by T. harzianum BI against nematode.

Biological control of the root-knot nematode Meloidogyne javanica by Trichoderma harzianum

The nematophagous fungus Lecanicillium psalliotae (syn Verticillium psalliotae) is a well-known biocontrol agent In this study, a chitinase gene Lpchi1 was isolated for the first time from L psalliotae using degenerate primers and DNA-walking technique The cloned gene Lpchi1 encoding 423 amino acid residues shares a high degree of homology with other pathogenicity-related chitinases from entomopathogenic and mycoparasitic fungi The complementary DNA sequence of the mature chitinase was amplified via reverse transcription polymerase chain reaction and expressed well in Pichia pastoris GS115 Through gel filtration, the recombinant chitinase was purified as a protein of ca 45 kDa with an optimal activity at pH 70 and 376°C The purified chitinase LPCHI1 was found degrading chitinous components of eggs of the root-knot nematode Meloidogyne incognita and significantly influence its development Moreover, our results also demonstrate that the protease Ver112 and the chitinase LPCHI1 from the same fungus interacted on the egg infection

Cloning of the gene Lecanicillium psalliotae chitinase Lpchi1 and identification of its potential role in the biocontrol of root-knot nematode Meloidogyne incognita.

Purification and characterization of a serine protease and chitinases from Paecilomyces lilacinus and detection of chitinase activity on 2D gels.

Distribution and economic importance. Morphology and ultrastructure. Evolution, phylogeny and systematics. Taxonomy and identification. Survey, surveillance and crop loss assessment. Extraction, culturing, and microscopy. Biology. Hatch and emergence. Host finding, invasion and feeding. Pathogenicity and damage levels. Interrelations with other microorganisms and pests. Development of resistant and tolerant varieties. Genetics of resistance and parasitism. Mechanisms of resistance. Natural parasites and biological control. Management. Genetic engineering.

The cyst nematodes

Control plant-parasitic nematodes with Trichoderma species and nematode-trapping fungi: The role of chi18-5 and chi18-12 genes in nematode egg-parasitism

Ultrastructure of Heterodera glycines cysts, eggs, and juveniles parasitised by Arkansas fungus 18 (ARF18) was studied with transmission and scanning electron microscopy. Transmission electron microscopy revealed that parasitised cysts, eggs, and first-stage juveniles in eggs were filled with ARF18 fungal hyphae. Numerous pores, apparently caused by fungal penetration, were found below the sclerotiumlike structures on the cyst cuticles. The cyst cuticles at the site of the sclerotiumlike structures appeared to have been dissolved. These results suggest that ARF18 penetrates the cyst cuticle enzymatically (...)

D. G. Kim

Papers

Ultrastructure of Heterodera glycines parasitized by Arkansas fungus 18