Identification of wild-species introgressions in the Mi-1 region of tomato breeding lines using a simple polymerase chain reaction-based method

A polymerase chain reaction (PCR) marker, PMIF/PMIR (tightly linked to the Mi-1.2 gene, which provides resistance to the root knot nematode) was developed. PCR primers were designed in intron 1 of the Mi-1.2 gene. PCR using these primers produced six different profiles for different tomato lines. These profiles allowed discrimination among lines of Solanum lycopersicum with no introgressions from wild species in the Mi-1.2 gene region and lines with introgressions from S. peruvianum, S. chilense and S. habrochaites. Furthermore, these PCR profiles distinguished between resistant (Mi/Mi, Mi/+) and susceptible hybrids (+/+) of root knot nematode. Sequences of the 780-bp PCR-amplified fragment had 99% identity with intron 1 of the Mi-1.2 gene, which confirmed the tight linkage of the markers to the studied locus. The information generated by these primers could be used in tomato breeding programs for detection of introgressions from wild species in the Mi-1.2 region of chromosome 6.