Phylogenetic relationships among Lactuca (Asteraceae) species and related genera based on ITS‐1 DNA sequences

Abstract

Internal transcribed spacer (ITS-1) sequences from 97 accessions representing 23 species of Lactuca and related genera were determined and used to evaluate species relationships of Lactuca sensu lato (s.l.). The ITS-1 phylogenies, calculated using PAUP and PHYLIP, correspond better to the classification of Feráková than to other classifications evaluated, although the inclusion of sect. Lactuca subsect. Cyanicae is not supported. Therefore, exclusion of subsect. Cyanicae from Lactuca sensu Feráková is proposed. The amended genus contains the entire gene pool (sensu Harlan and De Wet) of cultivated lettuce (Lactuca sativa). The position of the species in the amended classification corresponds to their position in the lettuce gene pool. In the ITS-1 phylogenies, a clade with L. sativa, L. serriola, L. dregeana, L. altaica, and L. aculeata represents the primary gene pool. L. virosa and L. saligna, branching off closest to this clade, encompass the secondary gene pool. L. virosa is possibly of hybrid origin. The primary and secondary gene pool species are classified in sect. Lactuca subsect. Lactuca. The species L. quercina, L. viminea, L. sibirica, and L. tatarica, branching off next, represent the tertiary gene pool. They are classified in Lactuca sect. Lactucopsis, sect. Phaenixopus, and sect. Mulgedium, respectively. L. perennis and L. tenerrima, classified in sect. Lactuca subsect. Cyanicae, form clades with species from related genera and are not part of the lettuce gene pool.

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.…”

“…(b) Beneficial -L. serriola is a potentially valuable source of genes for cultivated lettuce breeding programs (Zohary 1991;Koopman et al 1998). A gene for downy mildew resistance from L. serriola was incorporated into L. sativa cultivars Calmar and Valverde (Ryder and Whitaker 1976).…”

Shift of the western boundary of the distribution area of Micromeria cristata (Hampe) Griseb. and Steptorhamphus tuberosus (Jacq.) Grossh

“…Grossh.). Molecular analysis based on ITS-1 DNA sequences (KOOPMAN et al 1998), has not supported a distinction between Lactuca and Steptorhamphus. Nevertheless, these investigations were not sufficient for a revised delimitation of Lactuca and related genera (KILIJAN 2001).…”

“…Material is also compared with herbarium specimens preserved in the herbarium collection of the Institute of Plant Sciences in Graz. Due to the diverse taxonomic treatments of Micromeria and Steptorhamphus genera a short taxonomic overview is given (BALL and GETLIFFE 1972;CHATER and GUINEA 1972;[ILI] 1979;DAVIS 1982;GREUTER et al 1986;WAGSTAFF et al 1995;PRATHER et al 2002;TRUSTY et al 2004;BRÄUCHLER et al 2005;KOOPMAN et al 1998;STEBBINS 1937;TUISL 1968;FERÁKOVA 1977;KILIJAN 2001;LEBEDA et al 2001LEBEDA et al , 2004. In order to avoid confusion with similar plants in our flora, some important morphometric features are specified, such as length of the flower and verticillaster peduncle (Micromeria) and the presence of an outer minute pappus row (Steptorhamphus).…”