Science - October 2, 2009

Island hopping uncovers wild leeks for breeders

Dutch breeders have long wanted to make their leek varieties more resistant to diseases and pests. Gene bank CGN's Greek island expedition successfully ferreted out more than a hundred different wild leek plants.

No waters are too high for Elias Polenis, Greek colleague of Chris Kik, when he spots a wild leek species on an uninhabited island.
Dr. Chris Kik was involved last summer in an expedition in Greece, where the ancestors of our current leek plants come from. His search for wild leek took him to places which could be featured in holiday brochures. Kik scouted round the islands of Karpathos, Crete, Andros, Kythira and Lesbos. He foraged the coasts of the Peloponnesus. He clambered up steep mountain slopes in search of wild leek, and explored little uninhabited islands off the coast accessible only by swimming.
Kik works at the Dutch Centre for Genetic Resources (CGN) in Wageningen. It was high time for such an expedition, he says, as there are too few 'accessions' of wild leek stocked in the gene banks. An accession is a place of origin or the place where the plant is found - the more varied the places, the bigger the genetic diversity of the plants. There are has 98 accessions of the wild leek species Allium ampeloprasum stored in gene banks, while only one accession of the wild species A. bourgeaui is available worldwide. Worse than that, the accession for the Allium commutatum species which grows in the wild is not available at all.
Breeders, however, need these wild species for inbreeding in order to produce useful characteristics in commercial leek varieties. 'Breeders fail to make headway with the existing limited genetic diversity, says Kik. He and his Greek colleagues found wild leeks in 103 different areas. All in a month's time. He found 63 accessions of Allium ampeloprasum and brought home 21 and 19 different samples respectively of the rare A. bourgeaui and A. commutatum. He considers this 'quite a success'. The wild plants will be examined in the coming years at the CGN and the breeding companies. 'The companies will breed and test the wild leek species, and we will process the information', says Kik. The breeders look, for example, for genes which can make leek resistant to diseases and pests. Raising the resistance is necessary as fungicides and pesticides are being increasingly banned in vegetable cultivation.
Kik also thinks that the wild species can withstand drought and salty conditions better. These are desired characteristics in the light of climate change. 'Since the Greek islands do not have much rainfall, I expect that the A. bourgeaui found on steep rocky walls is fairly drought tolerant. Most of the small islands off the coast are less than two metres high, and often flooded by salt water. A. commutatum, the leek species which grows here, will perhaps have developed salt tolerance.' The challenge for the breeders is to find the genes responsible for these characteristics. And then to produce new varieties. The efforts to obtain better leek varieties have been going on for almost ten years, says Kik.