Little Researched, But Interesting Wild Lettuce Variety Now Available

Lactuca aculeata is a wild lettuce species with potentially interesting properties such as disease resistance and drought tolerance. Five years after the collecting expedition in Jordan, CGN is making seed of this and other wild lettuce varieties available for breeding, research and education.

Breeders are very interested in wild lettuce varieties. They contain properties that can be an enrichment for cultivated lettuce, such as resistance to diseases and pests, tolerance to drought and robust growth. “However, you cannot just cross everything with a cultural species. We divide the gene pool into three categories: easily crossable, difficult to cross and only crossable with special techniques such as embryo rescue. Kompass lettuce is widely used in breeding, but there are other easily cross-breedable wild species, such as Lactuca aculeata , that are rarely found in gene banks," says Rob van Treuren, responsible for CGN's lettuce collection.

That is therefore a reason to significantly increase the number of accessions of L. aculeata . A difficult point is that the areas of origin of this species are largely located in countries that are not accessible for collecting expeditions.

Cooperation with Jordan
But fortunately the species is also widely distributed in Jordan. In collaboration with the Jordanian research institute NCARE, CGN was able to set up a collection mission in 2017. The expedition was partly paid for by five breeding companies. They have also largely taken care of the propagation of the collected seed. In return, an embargo has been imposed so that the financiers can have exclusive use of the genetic material for a while. That embargo has now ended and other interested parties can now also request seeds from CGN.

A material transfer agreement (MTA) was agreed with Jordan at the time for access and use of the material. Van Treuren: “This agreement deviates somewhat from the Standard Material Transfer Agreement (SMTA) of the International Treaty on Plant Genetic Resources for Food and Agriculture (ITPGRFA), an agreement that is currently used by most gene banks (including CGN). For that reason, the material from Jordan is in a 'special collection'.

Genetic variation
During the mission in Jordan, gatherings took place in a large area. “After all, you want a lot of genetic variation. Then multiple areas of origin are necessary. We also pay attention to differences in size, shape and visible disease resistances to obtain variation. You collect ripe seeds, which you then try to propagate. We aim for at least 20 grams of seed, which is about 20,000 seeds,” says Van Treuren.

After propagation and determination of germination capacity (at least 60%), the seed is divided into several portions: “We save part for propagation and determination of germination capacity in the future. Backup samples also go to a fellow gene bank and to the Global Seed Vault in Svalbard. Then there are the user bags with one hundred seeds per accession, intended for distribution. And whatever is left, we store it in bulk,” he says.

Climate change
L. aculeata is easy to cross with cultivated lettuce and may contain interesting properties such as resistance to downy mildew (Bremia), a fungal disease that causes a lot of damage in lettuce cultivation. “It is a little-researched species, so we don't know much about it yet. But it is expected that it will have many useful features,” Van Treuren thinks.

In addition, a number of other wild lettuce species have been collected on a limited scale, such as L. orientalis and L. undulata . These are more difficult to cross with cultivated lettuce, but because they were collected in desert areas they may contain interesting properties such as drought tolerance. These are characteristics that are becoming increasingly important as the climate changes.

Request seeds
Interested parties can request seeds from the special collection from Rob van Treuren, curator of the lettuce collection at CGN.