A LACTUCA-UNIVERSAL-HYBRIDIZER, AND ITS USE IN CREATION OF FERTILE INTERSPECIFIC SOMATIC HYBRIDS

A Lactuca sativa cv. Ardente line heterozygous for a gene encoding res istance to kanamycin, a positive and dominant trait, was crossed with cv. Girelle, which is heterozygous for a recessive albinism marker. Th e resulting seeds yielded 25% albino seedlings, of which 50% were also resistant to kanamycin. Such plantlets (KR, a) grown in vitro were us ed for preparation of universal hybridizer protoplasts, since green bu ds that can develop on kanamycin containing-medium should result from fusion with any wild-type protoplast. To test the practicability of th is selection scheme, we fused L. sativa KR, a protoplasts with protopl asts derived from various wild Lactuca as well as various other relate d species. Protoplast-derived cell colonies were selected for resistan ce to kanamycin at the regeneration stage. Green buds were regenerated after fusion with protoplasts of L. tatarica and of L. perennis. So f ar, 9 interspecific hybrid plants have been characterized morphologica lly. In addition, random amplified polymorphic DNA (RAPD) analysis wit h selected primers confirmed that these plants are indeed interspecifi c hybrids. Some plants are female-fertile and production of backcross progenies with L. sativa is in progress. Since many desirable traits s uch as resistances to viruses, bacteria and fungi (Bremia lactucae) ha ve been characterized in wild Lactuca species, the use of somatic hybr idization in breeding programmes now appears a practical possibility.