Genetic diversity in Mediterranean Brassica vegetables: seed phenotyping could be useful for sustainable crop production

The European BrasExplor project aims to explore the genetic diversity present in two economically important Brassica crop species, Brassica oleracea and B. rapa, for sustainable crop production. This diversity is present in wild populations but also in cultivated landraces and has been shaped by contrasting environments. An international consortium of 11 partners has begun to collect and multiply wild populations extending from the French North Atlantic coast to the southern Algerian desert as well as local cultivars from 6 contributing countries in order to characterize the genetic diversity available over a wide soil-climate gradient. A total of 100 populations has been obtained for each species. Identifying the genetic variation and understanding the basis for it will allow the development of breeding strategies for a better adaptation of turnip (Brassica rapa) and cabbage (Brassica oleracea var. capitata) to climate change. One third of the collection has been already phenotyped for its germination traits of native seeds harvested in 2020 for wild populations or of local landraces provided by farmers and seed banks. In favourable conditions, a high diversity in germination capacity and germination rate was observed independently of seed age. The two species have a different germination profile: some turnip seeds can stand higher temperature and lower water potential than most cabbage seeds. Variation in flowering time has also been documented in these plants.