CYTOLOGICAL VARIATION OF (AAG)7 REPEAT ON LETTUCE CHROMOSOMES BY FLUORESCENCE IN SITU HYBRIDIZATION (FISH)

Cytological studies using fluorescence in situ hybridization (FISH) technique provides phylogenetical information in closely related taxa and have been widely applied for karyotyping and studying chromosomal organization and evolution in plant species. In the present study, FISH using a microsatellite sequence of (AAG)7 as the probe was performed in order to discriminate the chromosomes in four Lactuca species, i.e., L. sativa, L. serriola, L. saligna, and L. virosa. The experiment was carried out in April to September 2018 at Laboratory of Genetic and Plant Breeding of Breeding of Graduate School of Horticulture, Chiba University, Japan. Different distribution patterns of (AAG)n signals were shown on the chromosomes in the four Lactuca species studied, In L. sativa and L. serriola, FISH with (AAG)7 sequences revealed dispersed distribution patterns with one pair of bright signals, respectively. While in L. saligna and L. virosa, distinct signals with different intensities were observed in two pairs of chromosomes of L. saligna and five pairs of chromosomes of L. virosa. In conclusion, the AAG repeat signals could be used as cytogenetic landmarks for chromosome identification in Lactuca species.

Molecular Diversity in Lactuca Species Using Isozymes and RAPD Markers

Background: understanding molecular diversity in Lactuca species is substantial for the management, improvement and efficient uses of their accessions. Therefore, this work aimed to evaluate molecular diversity among and within Lactuca species. Methods and Results: the molecular diversity was assessed using isozymes and RAPD analyses that gave 87.09% and 100% polymorphic percentages respectively, indicating a high genetic variation within and among Lactuca species. The number of alleles were higher in the wild species compared to the cultivated species, reflecting a reduction in the richness of alleles in the cultivated species due to domestication that caused a reduction in genetic diversity to meet the demand for high crop productivity. Isozymes and RAPD clustering dendrogrames: (1) separated, L. sativa accessions in more than one cluster confirming their polyphyletic origin; (2) collected the accessions of L. viminea in one cluster revealed its homogeneity; and (3) divided the accessions of L. saligna in two clusters varied in the number of alleles, particularly “A” form. The corresponding analysis associated the accessions of the wild species based on “B” form of the alleles of the tested isozymes, and the cultivated species on the forms “A” and “C”, suggesting that: (1) allele “B” might be the primitive form of these loci that can tolerate the environmental stresses which prevails in the habitats of the wild species, and (2) forms “A” and “C” could be the derived forms. Conclusions: These results are of great interest for the management of Lactuca germplasm and for future breeding programs of lettuce.

Sedative Effects of Latexes Obtained from Some Lactuca L. Species Growing in Turkey

Lactuca L. species belong to the Asteraceae family and these plants are traditionally used for therapeutic purposes around the world. The dried milky latex of L. serriola is known as “lettuce oil” and is used as a sedative in Turkey. This study aimed to evaluate the sedative effects and analyze the chemical compositions of latexes obtained from some Lactuca species growing in Turkey. The sedative effects were evaluated through various behavioral tests on mice. For this purpose, latexes were obtained from L. glareosa Boiss., L. viminea (L.) J. Presl and C. P, L. mulgedioides (Vis and Panćić) Boiss. and Kotschy ex. Boiss., L. saligna L., and L. serriola L. The latex from L. saligna showed the highest sedative effects, whilst L. serriola and L. viminea latexes also displayed significant sedative effects compared to the control group at a dose of 100 mg/kg. However, the latexes from L. glareosa and L. mulqedioides did not exhibit any sedative effects on mice. Characteristic sesquiterpene lactones (lactucin, lactucopicrin, 11,13β-dihydrolactucin, and 11,13β-dihydrolactucopicrin) were determined qualitatively and quantitatively by high-performance liquid chromatography (HPLC). Lactucin was identified as the main component.

Sequence Analysis of the Internal Transcribed Spacer (ITS) Region of the Nuclear Ribosomal DNA (nrDNA) and Chloroplast trnL-F Region (cpDNA) of Some Lactuca L. (Asteraceae) Species in Turkey

In the current study, sequence analysis of some Turkish Lactuca L. species using nrITS DNA and trnL-F cpDNA sequences were performed to elucidate phylogenetic relationships among the taxa under study. Hieracium umbellatum was used as an outgroup. Different plant materials of Lactuca were collected from different parts of Turkey during excursions of summer 2013. Plant materials were either kept in silica gel or kept fresh for immediate DNA isolation. Both phenol chloroform-isoamyl alcohol method and commercial kits were used to extract genomic DNA for PCR reactions. ITS4 and ITS5A primers were utilized for ITS region, while trnLe and trnLf primers were used to amplify the trnL-F region. Obtained DNA sequences were edited both manually and by using BioEdit 7.0.4.1. Sequencing data were aligned via ClustalW program and analyzed using PAUP 4.01b10 software. nrITS sequences varied from 639 nucleotides to 735 nucleotides. Average nucleotide composition for nrITS was 22.1% (T), 27.9% (C), 23.2% (A) and 26.8% (G). It was also found that divergence values differed between 0.0000 and 0.10290. The trnL-F sequences varied from 296 nucleotides to 385 nucleotides. Average nucleotide composition of trnL-F sequences was 34.1% (T), 18.4% (C), 31.6% (A) and 16.0% (G). It was also found that divergence values differed between 0.0000 and 0.09674. Neighbour Joining (NJ) trees were constructed in order to identify the relationships among Lactuca species. Phylogenetic trees based on ITS region were found to be more useful than phylogenetic trees based on trnL-F region. After analysis of the results obtained, the data suggest that Lactuca contains 2 clades, with clade 1 having 2 subclades. These results support the prior phylogenetic studies on Lactuca and hence provide an up to date review of Turkish Lactuca species.