The effects of fungal strains with biocontrol potential on the motility and reproduction of Meloidogyne incognita

MSc (Integrated Pest Management), North-West University, Potchefstroom Campus

Root-knot nematodes (Meloidogyne spp.) pose a global threat to grain crop production since it causes major yield losses which results in less food sources for animals and humans. Since classical nematicides are continually withdrawn from markets, safer nematode management alternatives are gaining popularity. This includes the use of biological agents, viz. fungi and bacteria in particular, for the management of major nematode pests such as Meloidogyne spp. During this study strains of Trichoderma asperellum, Trichoderma asperellum kd, Trichoderma harzianum, Trichoderma virens and Clonostachys rosea together with two formulated products containing spores of C. rosea (CR) and T. asperellum strain kd (Eco-T®) as active ingredients and supplied by Andermatt Plant Health Products (Pty) Ltd. were tested for their adverse effects on the biology of M. incognita. In vitro trials were conducted to determine the effects of the spores of the fungal isolates and formulated products on the motility of second-stage juveniles (J2), while in vivo trials investigated their effects on female reproduction. The first set of in vitro studies, during which the fungal strains were propagated on potato dextrose agar, resulted in non-optimal growth and spore production. Follow-up in vitro trials using a bran-based substrate as growth medium for the fungal strains, resulted in the highest concentrations of 108 spores/mℓ being the most effective (>70%) in reducing J2 motility of all strains. Unfortunately the efficacy of the two formulated products in reducing J2 motility was inferior (<30%). In vivo glasshouse experiments, conducted for all five strains applied at concentrations of 107 and 108 spores/mℓ, as either seed treatments or direct soil applications, were able to reduce M. incognita life-stage densities 48 days after planting and inoculation between 10% - 45%; T. harzianum having the lowest and C. rosea having the highest reduction respectively. Reduction in M. incognita root galling ranged from 15% -47% with T. harzianum having the lowest and T. virens having the highest. Insignificantdecreases of M. incognita J2 numbers in soil as well as increases in plant growth parameters were obtained for soybean in this South African study. Similarly to the in vitro results obtained in this study, the efficacy of the two formulated products in reducing M. incognita life-stage numbers and root galling were mostly insignificant, while similar trends were evident for non-significant increases in plant growth parameters. Field experiments should be done to evaluate the fungal strains and formulated products under natural, prevailing environmental conditions, while improved formulation and seed-coating approaches should be investigated to optimize the efficacy of these biological products showing potential bionematicide activity.

Masters