Microprotoplast fusion technique: A new tool for gene transfer between sexually-incongruent plant species.

Various aspects of a microprotoplast fusion technique and the strategies followed for intergeneric partial genome transfer (one or a few chromosomes) and alien genes from sexually-incongruent donor species to recipient species are described. The essential requirements of the microprotoplast fusion technique are the induction of micronuclei at high frequencies, as well as the isolation and enrichment of sub-diploid microprotoplasts in donor species, efficient fusion of the donor microprotoplasts with normal recipient protoplasts and stable regeneration of plants from fusion products. The results on the production of microprotoplast hybrid plants between the transformed donor lines of Solanum tuberosum and Nicotiana plumbaginifolia carrying various genetic markers, and a recipient line of Lycopersicon peruvianum or Nicotiana tabacum, and on the transfer and expression of alien genes (kanamycin resistance, β-glucuronidase) are presented. The data obtained on microprotoplast hybrid plants between S. tuberosum and L. peruvianum showed that many of the hybrids contained one potato chromosome carrying nptll and GUS, and 24 or 48 L. peruvianum chromosomes (monosomic additions), and that they were male- and female-fertile. Various applications of chromosome transfer by this technique, especially for economically-important traits (e.g. disease or stress resistance) from sexually-incompatible wild species, for construction of chromosome-specific DNA libraries through microdissection and microcloning of chromosomes, or by flow-sorting of chromosomes for genome analysis, are discussed.