Genetic Relationship between Lactuca georgica and Five Other Lactuca subsection Lactuca Species as Revealed by TRAP Markers

Lettuce, Lactuca sativa, is one of the most popular and economically important leafy greens.  Wild relatives of lettuce have been and continue to be explored as a source of valuable traits such as disease resistance for this crop.  The genus Lactuca L. contains approximately 100 species, with L. serriola, L. altaica, L. saligna, L. virosa, L. aculeata, L. scarioloides, L. azerbaijanica, L. georgica, and L. dregeana being placed in section Lactuca L. subsection Lactuca L. along with cultivated lettuce.  All of these species have been placed in the primary gene pool for the crop with the exception of L. saligna and L. virosa which have been placed in the secondary and tertiary pools, respectively.   L. georgica has not been included in previous studies assessing the genetic relationships among these species. As a result, the relationship of L. georgica to other species is not known.  We genotyped 236 plants from 63 accessions representing six species, L. georgica, L. virosa, L. aculeata, L. saligna, L. serriola, and L. sativa with the target region amplification polymorphism (TRAP) technique.  Based on 50 polymorphic markers, these species were grouped in four distinct clusters: L. serriola, L. sativa and L. aculeata; L. virosa; L. georgica; and L. saligna.  It seems L. georgica is most closely related to L. virosa.