Special collection of 470 SSD lines of Lactuca spp.

Collection of 470 Lactuca single seed descent (SSD) lines, mainly derived from CGN’s regular collection.


The collection was largely developed within the framework of the TKI project, entitled ‘International Lactuca Genomics Consortium’ (ILGC). For this project a cross section of the lettuce gene pool, comprising nearly 500 accessions, was selected for DNA resequencing purposes. Resequencing of the lines was initiated in 2017 within the framework of the ILGC and continued in 2018 in a cooperation between CGN and the Beijing Genomics Institute (Shenzhen, China). Access to DNA sequencing data will be provided in due time. Large-scale metabolomics data were generated for part of the collection and are made available on this webpage. Results of this research are described in the journal Metabolomics (2018). The collection is currently being used for transcriptomics research and phenotypic analyses in the NWO-TTW research program "LettuceKnow, Science-Based Improvement of Salad", which started in 2019.

Documentation of the collection

Information about the collection can be found in the following spreadsheets:


  • The sheet ‘Line data’ contains information that is specific for the lines. Links are provided to pictures of the lines, while it is also indicated which lines have been used for DNA resequencing and metabolomics research.
  • The sheet ‘Accession data’ contains information about the accessions from which the lines were derived. Basic passport data are included, and links are provided to access more detailed information about the accessions. The sheet also includes morphological data recorded during field trials and accession regeneration, and trait data obtained in collaboration with the user community.
  • The sheet ‘Variety registration data’ includes morphological and trait data from published variety descriptions for part of the cultivated lettuces.


  • Data on the relative abundance of 2026 phytochemicals revealed by untargeted metabolic profiling of part of the collection, with annotations provided as far as possible.

Sample information

In 2016, a single individual per selected accession was raised in the greenhouse facilities at Wageningen Plant Research. These individuals were used for tissue sampling, and plants from autogamous species were maintained for seed production by selfing. Due to the absence of flowering in 2016 seed production for some lines took place in 2017. Second generation SSD lines were produced in 2018 in case of low seed yield. Plants with virus symptoms were tested for LMV, but test results were negative. Prior to seed set, all plants belonging to wild Lactuca species were covered in perforated plastic bags to protect the lines from contamination. Seed samples were cleaned, and dried at 15 °C and 15% RH to reach a seed moisture content of 3-7%. All lines were checked for sample purity. Some off-types, most probably resulting from contamination during post-harvesting procedures were detected and subsequently removed from the sample. It cannot be ruled out that some lines may contain off types that could not be identified based on seed characteristics, but obviously this probability is low. Neither can we rule out the possibility of genetic impurities due to heterozygous loci in maternal plants. No germination tests were performed on the samples. Germination rates of newly regenerated Lactuca samples are typically high. Since dormancy is not uncommon for wild Lactuca species, it is recommended to apply dormancy-breaking procedures, such as cold-treatment, when using wild material. Seed samples are stored in vacuum-sealed bags and maintained at -20 °C in the genebank facilities of CGN. 

Distribution procedures

Distribution bags contain 20 seeds per line. Seeds are distributed as Plant Genetic Resources for Food and Agriculture (PGRFA) under development using a Standard Material Transfer Agreement (SMTA) and an accompanying contract governing the transfer of seed samples of the special collection. Contract issues and payment conditions are to be arranged with the responsible curator Rob van Treuren (contact details presented below). 


CGN does not accept any liability for the incorrect identity of the material, insufficient germination or the presence of diseases. 

Contact for further information and ordering of seed samples

Rob van Treuren, curator leafy vegetables

Centre for Genetic Resources, the Netherlands (CGN), Wageningen University and Research, Droevendaalsesteeg 1, 6708 PB Wageningen