The reduced arbuscular mycorrhizal (AM) colonization mutant of tomato (rmc) is a single locus recessive mutation with different colonization phenotypes for different AM fungi. To test broader specificity and gain possible functional insights, we compared host status of rmc and near isogenic parent (Rio Grande 76R) for three root parasites. No significant colonization differences were found for bulb-and-potato aphid. However, root knot nematode (RKN) grew significantly better on rmc root cultures. Also, rmc was significantly more susceptible than 76R to Fusarium wilt. Our results indicate that the Rmc locus may have dual roles in symbiosis and parasitism.