ISOLATION AND CHARACTERIZATION OF LONG-TERM EMBRYOGENIC LINES IN ASPARAGUS-OFFICINALIS L

Somatic embryogenesis was obtained from 14 Asparagus officinalis L. ge notypes by in vitro culture of different explant types such as cladoph ylls, apices and isolated mesophyll cells. Explants first induced on a culture medium containing growth regulators produced calli and develo ped few somatic embryos when transferred on a hormone-free medium. Dur ing this development phase, we isolated a new type of friable tissues that produced abundant somatic embryos. The frequencies of emergence o f these highly embryogenic tissues were estimated between 10(-5) and 1 0(-6). These tissue were habituated; being established as long-term em bryogenic lines by repeated subcultures on hormone-free medium, contin uously they produced numerous somatic embryos, some of them converting to whole plants. Histological data showed these long-term embryogenic lines to grow by recurrent embryogenesis arising, from single epiderm al cells of preexisting embryos.