The purpose of this study was to develop a model system for studying tomato genetics. Agronomic, genetic, and molecular data are presented which show that the miniature Lycopersicon esculentum cultivar, Micro‐Tom (Micro tomato), fulfills the requirements for such a model. It grows at high density (up to 1357 plants/m−2); it has a short life cycle (70–90 days from sowing to fruit ripening); and it can be transformed at frequencies of up to 80% through Agrobacterium‐mediated transformation of cotyledons. Moreover, it differs from standard tomato cultivars by only two major genes. Therefore, any mutation or transgene can be conveniently studied in Micro‐Tom’s background and, when needed, transferred into a standard background. We took advantage of Micro‐Tom’s features to improve the infrastructure for mutagenesis in tomato. A screening of 9000 M1 and 20 000 M2 EMS mutagenized plants is described. Mutants with altered pigmentation or modified shape of leaves, flowers and fruits were found. In addition, an enhancer trapping and a gene trapping system, based on the Ac/Ds maize transposable elements, were transformed into Micro‐Tom and found to be active. In summary, Micro‐Tom opens new prospects to achieve saturated mutagenesis in tomato, and facilitates the application of transposon‐based technologies such as gene tagging, trapping and knockout.

SummaryWe describe new tools for functional analysis of the tomato genome based on insertional mutagenesis with the maize Ac/Ds transposable elements in the background of the miniature cultivar Micro-Tom. 2932 F 3 families, in which Ds elements transposed and were stabilized, were screened for phenotypic mutations. Out of 10 families that had a clear mutant phenotype, only one mutant was Ds-tagged. In addition, we developed promoter trapping using the ®re¯y luciferase reporter gene and enhancer trapping, using b-glucuronidase (GUS). We show that luciferase can be used as a non-invasive reporter to identify, isolate and regenerate somatic sectors, to study the time course of mutant expression, and to identify inducible genes. Out of 108 families screened for luciferase activity 55% showed expression in the¯ower, 11% in the fruit and 4% in seedlings, suggesting a high rate of Ds insertion into genes. Preferential insertion into genes was supported by the analysis of Ds¯anking sequences: 28 out of 50 sequenced Ds insertion sites were similar to known genes or to ESTs. In summary, the 2932 lines described here contain 2±3 Ds inserts per line, representing a collection of approximately 7500 Ds insertions. This collection has potential for use in high-throughput functional analysis of genes and promoter isolation in tomato.