Species relationships in Lactuca s.l. (Lactuceae, Asteraceae) inferred from AFLP fingerprints

Abstract

An AFLP data set comprising 95 accessions from 20 species of Lactuca s.l. (sensu lato) and related genera was generated using the primer combinations E35/M48 and E35/M49. In phenetic analyses of a data subset, clustering with UPGMA based on Jaccard's similarity coefficient resulted in the highest cophenetic correlation, and the results were comparable to those of a principal coordinates analysis. In analyses of the total data set, phenetic and cladistic analyses showed similar tree topologies for the well-supported parts of the trees. The validity of cladistic analysis of AFLP data is discussed. The results do not support a distinction among the serriola-like species L. sativa, L. serriola, L. dregeana, and L. altaica, which is in line with previous results. Therefore, we postulate that these species are conspecific. The serriola-like species L. aculeata occupies a clearly separate position, making it an ideal outgroup for studies of the closest relatives of L. sativa. The subsect. Lactuca as a group is well supported by our data, but the positions of L. saligna and L. virosa relative to the serriola-like species remain unclear. The close relationship between the sect. Mulgedium species L. tatarica and L. sibirica is corroborated by the present AFLP results and by additional crossability data.

The biology of Canadian weeds. 122. Lactuca serriola L.

“…They found that L. sativa and L. serriola shared all alleles at 36% of their loci, and that L. sativa was a complete subset of L. serriola at 67% of its loci. Koopman et al (1998Koopman et al ( , 2001, using ITS (internal transcribed spacer) sequences and AFLPs (amplified fragment length polymorphisms) as markers, confirmed many of the infrageneric boundaries suggested by Feráková (1977), and concluded that L. sativa and L. serriola are conspecific. They considered L. sativa the correct name for both species because of nomenclatural priority.…”

“…Ryder and Whitaker (1976) summarized the early and recent history of L. sativa, and referred to a sativa-serriola complex that was "large, polymorphic and capable of free interchange of genes with little, if any, reduction in fertility". The origin of cultivated lettuce is still contentious, but recent molecular work supports the view that it originated directly from L. serriola through selection (Kesseli et al 1991;Koopman et al 1998Koopman et al , 2001. Kesseli et al (1991) examined variation in RFLPs (restriction fragment length polymorphisms) in cultivated lettuce accessions and five Lactuca species, and concluded that L. sativa was closely related to L. serriola, but not to L. saligna or L. virosa.…”

“…This is likely because of the high degree of autogamy within these species (Feráková 1977). Nevertheless, Ryder and Whitaker (1976) suggested that there has been introgression between L. serriola and cultivars of lettuce, and Kesseli et al (1991) and Koopman et al (2001) identified several landraces thought to be intermediate between L. sativa and L. serriola. Thompson et al (1958) reported that the rate of out-crossing among different cultivars of L. sativa was 2.8%.…”

Hybridization rates between lettuce (Lactuca sativa) and its wild relative (L. serriola) under field conditions

“…Crop lettuce differs from prickly lettuce only for characters connected to domestication, like rapid growth, short life-cycle, absence of dormancy, and generally absence of prickles on the leaves and on the stem (Frietema de Vries et al, 1994). Both species are diploid, and their chromosome length and genetic background are equivalent (Koopman et al, 2001;Lindqvist, 1960a). Selffertility prevails in L. serriola (Mejias, 1994) and is commonly regarded as being complete in L. sativa (Jones, 1927).…”

Description of morphological characters of wild Lactuca L. spp. genetic resources (English-Czech version)

“…The recent information about taxonomy and relationships within the genus Lactuca L. was summarized by KOOPMAN et al (1998), LEBEDA (1998), KOOPMAN (1999) and LEBEDA and ASTLEY (1999), KOOPMAN et al (2001), LEBEDA et al (2001a). Precise taxonomical delimitation and uniform classification of this genus is limited by absence of data on morphology, anatomy, karyology, biochemical and molecular variability (LE-BEDA et al 1999).…”