New cases of somatic conversion (paramutation) in tomato (Lycopersicon esculentum Mill.)

The genetic behaviour of three chlorophyll variegated F1 tomato plants, derived from irradiated gametophytes, was analyzed over several generations of selfing and backcrossing. The results suggest that irradiation has put genes, different in all three mutants, into a labile state, n*, remaining so after fertilization. This state had the power of converting the associated wild allele N into a deficient form.'Somatic conversion' was soon followed, in Plant C11 always and nearly always in Plant C12, by stabilization of both alleles in a conversion-inactive recessive state, genetically similar, and stable except in special conditions.In the other type, found seldom in C12, always in C6, the n* state was permanent and transmissible. Conversion occurred with a certain frequency determined by developmental and genotypic influences, and the converted allele also acquired conversion power, so that gametes from an N n* plant were of three kinds: N, n* and n'*. This process corresponds to 'paramutation' (Brink 1958).Results were compared and contrasted with other published data.