Mi-1.2 gene, expressed in tomato plants, contributes to endogenous resistance against nematodes and some Hemiptera insects. The aim of this study was to screen the presence of dominant/recessive locus of the Mi-1.2 gene in tomato cultivars with different allelic combination using Mi23 SCAR method and to assess the capacity of the local potato aphid (Macrosiphum euphorbiae Thomas) population to develop on different tomato cultivars (dominant and recessive homozygotes in Mi-1.2 locus). The results showed that both Mi23 marker and potato aphid performance are relevant methods in screening tomato cultivars with a different allelic combination of Mi-1.2 gene. The assessment of biological potential of M. euphorbiae proved that, in comparison with control (tomato plants with recessive alleles of Mi-1.2 gene), the aphid mortality increased 9- and 4 - fold (in the first and second experimental series, respectively) and the female longevity decreased 3 - fold when fed on tomato cvs with dominant alleles of Mi-1.2 gene. Furthermore, the resistance against aphids manifests as an antibiosis mechanism in tomato plants carrying dominant alleles.
