SEXUAL AND SOMATIC HYBRIDIZATION IN THE GENUS LACTUCA

Various genes for disease resistance identified in wild Lactuca are di fficult, even impossible to exploit in lettuce breeding, due to sexual incompatibility between L. sativa and wild Lactuca sp. We adapted two cellular biology techniques to overcome these interspecific barriers: in vitro embryo rescue and protoplast fusion. In vitro rescue of imma ture embryos was used successfully for sexual hybridization between L. sativa and L. virosa. Vigorous hybrid plants were produced between L. sativa and seven accessions of L. virosa. Protoplast fusion permitted the regeneration of somatic hybrids between L. sativa and either L. t atarica or L. perennis. Hybrids between L. sativa and L. tatarica were backcrossed to L. sativa.