Tomato Carrying MI-1.2 Gene as a Host-Plant to the Two-Spotted Spider Mite (Tetranychus urticae Koch): Results of Laboratory Evaluation

Mi-1.2 gene contributes to the resistance of tomato plants against some species of herbivores (i.e. nematodes, aphids) that are sap-feeders. In this study, two genotypes of tomato (Solanum lycopersicum L. syn. Lycopersicon esculentum Mill.) plants with dominant (Motelle cv) and recessive (Moneymaker cv) Mi-1.2 alleles were evaluated as a host-plant to the two-spotted spider mite (Tetranychus urticae Koch, Acari: Tetranychidae). Plants were grown under glasshouse conditions. The effect of tomato genotypes on T. urticae bionomy was estimated on cut leaflets in controlled photoperiod, temperature and humidity (L/D=16/8 h; D/N temp.=23/20°C; RH=70%). Results of laboratory evaluation showed that both the bionomy and population parameters of T. urticae reached a very similar or even higher value on plants with dominant Mi-1.2 allele than on plants with recessive one. A relatively high value of T. urticae parameters on plants resistant to root knot nematodes indicates that the mite has potential to develop rapidly. This allows the mite population to reach the density causing marked damage to plant in a short time. It is concluded that the presence of Mi-1.2 gene product in tomato plants does not significantly affect the reproductive potential of T. urticae. Therefore, Mi-1.2 gene cannot be a satisfying source of plant resistance to this mite-herbivore generalist.