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.

The most efficient control methods are synthetic pesticides, which, however, have only a temporary effect on nematode populations and high environmental toxicity. For this reason, they 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.

In recent years, it has been revealed that nematodes communicate and alter their behavior through small-molecule compounds – the ascarosides. The ascarosides used by nematodes are also captured by plant roots, leading to an increased response of their natural defences against nematodes.

In the Handler project, we propose 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 evolves over time. This research also aims to contribute for a better understanding of the development of virulence in root-knot nematodes, which are always more virulent in agricultural 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 ascarosids, and the ability of plants to respond to these signals, will be critical to nematode competition and virulence, and could be explored in the development of new control strategies.