Root knot nematodes

Root-knot nematodes (RKN) are plant parasitic nematodes belonging to the genus Meloidogyne. They have a worldwide distribution and are polyphagous; it is estimated that overall they can parasitize all plants. They negatively affect plants feeding on root cells and interfering with the normal structure and function of plant roots. In horticultural crops, especially in greenhouses, they cause major damage and may lead to 100% production losses. Most RKN species can infect, feed and multiply in tomato roots thus tomato is considered an universal host.

In recent years it has been realized that nematodes can communicate with each other and alter their behaviour through the compounds they produce – the ascarosides. The nematode-produced ascarosides are also captured by plant roots that, in response, increase their natural defences against nematodes.

The Handler project, aims to investigate whether the use of partially resistant rootstocks affects competition between nematodes of different species, ie whether rootstocks act as a selective force, and how this phenomenon develops over time. This research will also contribute for a better understanding the development of virulence in root-knot nematodes, which are always more virulent in agricultural systems than in natural systems. A second objective of the project is to understand how ascarosides shape nematode-nematode and plant-nematode interactions. It is anticipated that communication between nematodes via ascarosides, and the ability of plants to respond to these signals, will be critical for nematode competition and virulence phenomena and could be explored in the development of new management strategies.

The most efficient methods of control are the use of synthetic pesticides which, however, have only a temporary effect on nematode populations and high environmental toxicity. For this reason these compounds have been banned in Europe, which has motivated the investigation of alternative forms of control. Regarding tomato plants, grafting is an alternative control strategy that has become increasingly popular. Several commercially rootstocks are available, but none of them are fully resilient. Thus, the use of grafting may act as selective pressure, increasing nematode virulence, that is, increasing nematode populations ability to infect plants.