Study of the three-genome hybridLycopersicon esculentum Mill. -L. chilense Dun. -L. peruvianum var 'humifusum' Mill. and its use as a source for resistance.

L. peruvianum var 'humifusum' is reproductively the most isolated of the species of the genusLycopersicon. It can be crossed with the cultivated tomato usingL. chilense as an intermediary. After a series of backcrosses of the three-genome hybrid F1 (L. esculentum ×L. chilense) ×L. peruvianum var 'humifusum' withL. esculentum, accompanied by selection for resistance to some economically important diseases, several lines were established. One of these lines, Cm 180, which showed resistance toClavibacter michiganensis subsp.michiganensis, was subjected to genetic analysis. This resistance was found to be controlled by a single dominant gene (Cm) that was not allelic to the gene originating fromL. hirsutum f.glabratum. ThisCm gene was genetically mapped on chromosome 4. The germ plasm ofL. peruvianum var 'humifusum' in combination withL. chilense was transferred intoL. esculentum. Different breeding lines possessing resistance to various diseases and pests could be developed from this material.