Summary Most plants have the ability to establish a symbiosis with arbuscular mycorrhizal ( AM ) fungi, which allows better plant nutrition. A plant signaling pathway, called the common symbiosis signaling pathway ( CSSP ), is essential for the establishment of both AM and root nodule symbioses. The CSSP is activated by microbial signals. Plant receptor(s) for AM fungal signals required for the activation of the CSSP and initial fungal penetration are currently unknown. We set up conditions to use virus‐induced gene silencing ( VIGS ) in Solanum lycopersicum to study the genes potentially involved in AM . We show that the lysin motif receptor‐like kinase Sl LYK 10, whose orthologs in legumes are essential for nodulation, but not for AM , and Sl CC a MK , a component of the CSSP , are required for penetration of the AM fungus Rhizophagus irregularis into the roots of young tomato plants. Our results support the hypothesis that the SILYK 10 ancestral gene originally played a role in AM and underwent duplication and neofunctionalization for a role in nodulation in legumes. Moreover, we conclude that VIGS is an efficient method for fast screening of genes playing major roles in AM .