T-DNA-tagged chromosome 12 in donor Lycopersicon esculentum × L. pennellii is retained in asymmetric somatic hybrids with recipient Solanum lycopersicoides

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Abstract
Asymmetric somatic hybrid plants were recovered after fusing irradiated mesophyll protoplasts of donor Lycopersicon esculentum × L. pennellii (EP) interspecific hybrid with callus-derived protoplasts of recipient Solanum lycopersicoides. EP plant A54 had been previously transformed by an agrobacterium vector, and the T-DNA insert mapped to the L. esculentum chromosome 12. The T-DNA insert conferred kanamycin resistance to EP that was subsequently used to select cell fusion products and recover asymmetric hybrid plants that retained tagged chromosome 12. Doses of 50- and 100-Gy irradiation promoted the elimination of only a few donor chromosomes. At 200 Gy, the regenerated plants had ploidy levels higher than tetraploid. However, the T-DNA tagged chromosome 12 was always retained in the asymmetric hybrid plants tested. Likewise, all plants from the 100-Gy series, with the exception of number 160, were mixoploid in the root-tip cells. Such mixoploid asymmetric somatic hybrids could be stabilized by inducing adventitious shoots on leaf strips cultured on shoot regeneration medium containing kanamycin. The asymmetric hybrid plants did not produce viable seed when self-pollinated or backcrossed to tomato or S. lycopersicoides.