Evaluation of somaclones of tomato under tropical conditions Morales C . , Santana N . , and Xiques S . National Institute of Agricultural Sciences, Havana, CUBA . Most of the focus of crop improvement in our country has been based fundamentally on selection practised on indigenous varieties, the introduction of exotic varieties and the hybridisation of the two types .   In recent years new techniques have been incorporated for the creation of genetic variability, and agricultural biotechnology holds much promise in the development of horticultural cultivars (Gómez and Depestre, 1992) . Starting from the variety Campbell - 28, (C - 28) belonging to the Lycopersicon esculentum cv . Mill, grown under conditions of cultivation in vitro, the somaclones selected were SC - 7, SC - 8, SC - 10, SC - 36, SC - 37, (for their good characteristics) all coming from the same callus, obtained from the National Institute of Agricultural Sciences (INCA); and the behaviour of these and the donor were analysed in the third generation . Variables of agricultural interest, the internal quality of the fruit, as well as the disease incidence under our conditions were evaluated .   In Table 1 the analysis of variance of the characters of agricultural interest is shown, and data given for the internal quality of the fruits, where there were significant differences between the genotypes studied for the polar and equatorial diameter, and the mass average of the fruits . In the results of the test of multiple ranges of Duncan for these characters it was observed that the greater values were for SC - 36, C - 28 SC - 37, which do not show significant differences among each other .   Table 1 also shows significant differences between genotypes for the total soluble solids and content of vitamin C .   The results of the test of multiple ranges of Duncan (Table 1), show that the cultivar containing greater soluble solids was SC - 10, followed by C - 28, SC - 36 and SC - 7, with no significant differences between them;   for the content of vitamin C, the somoclones SC - 8, SC - 10, and C - 28 gave the best results . Table 2 presents the response of the above genotypes to the diseases in this study . It was observed that all the somaclones presented resistance to the Phytophthora infestans virus, however only SC - 8 and SC - 37 were resistant to Xanthomonas vesicatoria .   Another aspect of supreme interest is the tolerance of the fields of SC - 37 and SC - 8 to Alternaria solani , Phytophthora parasitica , and also to Xanthomonas vesicatoria .   In the end, SC - 37 displayed better behaviour in the field in the face of the evaluated disease . These results show the feasibility of the use of somaclonal variation as an alternative method in the programs of improvement of the cultivation of tomato, with this example demonstrating the potential use in improving complex characters such as disease resistance . Literature cited: Gomez O . Y T . Depestre (1992) Mejoramiento genetico de Hortalizas