Plant Parasitic Nematodes

  • Colour enhanced Scanning Electron Micrograph of the whip-like larva of the root-knot nematode Meloidogyne incognita penetrating a rootColour enhanced Scanning Electron Micrograph of the whip-like larva of the root-knot nematode Meloidogyne incognita penetrating a root
  • “Plant parasitic nematodes cause circa. US$120 billion of crop losses per annum”

Nematodes are microscopic roundworms that attack plant roots and to a lesser extent stems and leaves. They are a major group of crop pathogens and cause worldwide losses estimated at about US$120 billion per annum. Some species retain their worm-like form throughout their life-cycle and browse from cells at the root surface (‘ectoparasites’) whereas others, such as root lesion nematodes, feed from cells inside the root (‘migratory endoparasites’). Other species, such as root-knot and cyst nematodes (‘sedentary endoparasites’), induce the formation of specialised feeding cell structures in roots losing their ability to move and become enlarged egg producing factories.

Plant parasitic nematodes damage host plants by disturbing the water and nutrient conducting systems of the root (diverting nutrients for their own growth and reproduction) and by allowing other pathogens such as soil fungi to enter infected roots. Plants infected with nematodes show symptoms of wilting and water stress, nutrient deficiencies and early senescence.

Strategies to reduce nematode damage have included crop rotation employing resistant or tolerant varieties if available, inter-cropping with non-host plants and the application of nematicides. However, in many cases suitable genetic resistance is not available and over the past decade about three-quarters of frontline nematicides have been banned or subject to limited use mandates (due to their toxicity and persistence in soil and groundwater).

There is now a real need to develop new controls for these plant parasites and to contribute to increasing world food production in a sustainable manner. Nemgenix is meeting this challenge by developing new forms of genetic resistance based on gene silencing technology (‘RNAi) and new classes of environmentally friendly nematicides.