A hidden defense: How native nematode communities and their diversity could limit invasion by Meloidogyne graminicola in soil for cereal crops in France

The rice root-knot nematode Meloidogyne graminicola is an emerging threat in Europe, as demonstrated by recent invasions by this plant-parasitic nematode in Italy. In this context, our study focused on biological invasions in agroecosystems, more specifically the possible threat posed by this nematode to cereal crops in France. M. graminicola has a wide host range, including wheat, an economically important crop in France. Understanding its competitive interactions with native plant-parasitic nematode (PPN) communities is crucial to identify indicators of soil resistance and to predict the risk of its establishment. We carried out two bioassays under controlled conditions with two isolates of M. graminicola , one from Italy and one from Borneo, inoculated onto soft wheat (cv. Chevignon) in soil from Brittany, chosen as representative of cereal systems in France. Interactions with the native PPN community were monitored 35 and 85 days after inoculation at two inoculum levels. Results showed that the endoparasite Pratylenchus fallax was the most effective competitor and a potential indicator of soil resistance, limiting M. graminicola in the roots. Ectoparasites like Dolichodoridae and Tylenchidae also contributed by restricting M. graminicola access to roots. The second bioassay confirmed the presence of P. fallax , validating its competitive role. This work illustrates, for the first time, that the functional diversity of PPN communities in France could constitute a biotic filter to M. graminicola invasion. Our findings point to the use of nematode species like P. fallax as indicators of soil resistance and an integrated and sustainable approach to pest management in the context of gradual withdrawal of nematicides. • Functional diversity of nematodes limits invasion by Meloidogyne graminicola. • Pratylenchus fallax is identified as a soil resistance indicator in wheat French systems. • Bioassays reveal competition between invasive and native nematodes in France. • Findings support ecological indicators for sustainable pest management.