Genetic polymorphism in Lactuca aculeata populations and occurrence of natural putative hybrids between L. aculeata and L. serriola

The wild lettuce, . Lactuca aculeata Boiss, is a robust and very prickly annual plant geographically restricted to the Near East and the Anatolian plateau. Israel is within the conjectured centre of origin of . L. aculeata, which is closely related and fully interfertile with cultivated lettuce, . Lactuca sativa L. Twenty-eight . L. aculeata, five . Lactuca serriola, and three putative hybrids . L. aculeata × . L. serriola, i.e. total 36 accessions, representing 13 populations from Israel and 3 from Jordan, were studied. Material originated from various elevations (222-968 m a.s.l.) and habitats. Seeds (achenes) were collected from individual plants, generally separated by at least 2 m to avoid collection of duplicated material, at different sites across Israel. The material was regenerated and taxonomically validated at the Department of Botany, Palacký University in Olomouc, Czech Republic. Morphological characterization showed that the Israeli populations of . L. aculeata do not exhibit broad morphological variability. Eight enzymatic systems were analysed for their polymorphism (esterase, glutamate-oxaloacetate transaminase, leucine aminopeptidase, malic enzyme, NADH dehydrogenase, phosphogluconate dehydrogenase, phosphoglucomutase, glucose-6-phosphate isomerase). In total, nine of 21 loci scored for the entire set of . Lactuca spp. samples exhibited polymorphic character. A highly homogeneous group of the 28 (ca 75%) . L. aculeata accessions were grouped in one compact cluster, while the remaining accessions formed additional two smaller clusters with higher values of genetic distance indices. The five . L. serriola accessions constituted the most distant cluster. Three accessions exhibiting a phenotypically intermediate character between . L. aculeata and . L. serriola, grouped together. They are considered natural putative hybrids of . L. aculeata × . L. serriola. The origin and evolutionary consequences of these hybrids are discussed.