ABSTRACT
Selection (MAS) ........................................................................................ 447
9.6.5.4 Advances in Phenotyping Procedures....................................................... 448
9.6.5.5 Cell and Tissue Culture............................................................................. 448
9.6.5.6 Transformation .......................................................................................... 448
9.7 Conclusions .......................................................................................................................... 449
Acknowledgments ........................................................................................................................ 453
References .................................................................................................................................... 453
9.1 INTRODUCTION
Lettuce (Lactuca sativa L.) is a member of the family Asteraceae, the largest of the dicotyledo-
nous families (Judd et al. 1999). The genus includes about 100 species (Lebeda, Dolez
ˇ
alova
´
, and
Astley, 2004a, 2004b). Nearly all of these are not compatible with cultivated lettuce. However,
three species: L. serriola, L. saligna, and L. virosa, are compatible, to different degrees (Zohary
1991). L. serriola (prickly lettuce, compass lettuce or common wild lettuce), is found worldwide
(Lebeda, Pink, and Mieslerova
´
, 2001c, 2004a). It is completely compatible with lettuce and is
considered by some to be the same species and a direct progenitor of cultivated lettuce (de Vries
1997; Koopman et al. 1998). L. saligna is primarily a Mediterranean species, occurring in Europe,
northern Africa, and the Mideast (Zohary 1991; Lebeda et al. 2004b). It is less closely related to
L. sativa than is L. serriola. Crosses are most easily made when L. saligna is used as the female
parent. L. virosa is also a Mediterranean species. In Europe it is distributed more towards the
south and west than L. saligna (Fera
´
kova
´
1977; Lebeda, Dolez
ˇ
alova
´
, and Astley 2004a). It is the
least closely related of the three to L. sativa. Crosses with cultivated lettuce are very difficult and
F
plants are highly sterile.
