The transgenic tomato plants showing the insecticidal activity against the coleopteran insect larvae have been bred to the 4th generation (R₄). The Bacillus thuringiensis subsp. tenebrionis (B.t.t.)-toxin gene and the expression were detected in the R₄ transgenic plants. The expression of the toxin gene conferred a coleopteran insect larvae tolerance to the transgenic tomato plants. The ploidy levels of the R₄ transgenic plants were diploid. The results indicated that the toxin gene was inherrited to the next generation and expressed. Such a molecular breeding can provide a method for a permanent control of insects a agronomic relevance.