The genetic diversity of wild and cultivated cornflower populations: implications for conservation

International audienceThe cornflower, Cyanus segetum Hill, 1762 (formerly Centaurea cyanus L.) is an iconic arable plantthat was historically widespread in Western Europe, but has shown a marked demographic declinesince the mid-20th century. The species is distinctively attractive due to its large blue-colouredflowers and is an important source of nectar for pollinating insects. For these reasons, populationsfrom horticultural or cultivated origins are frequently sown within flower fallows and flower strips.However, cultivated populations may be of non-local origin and have a reduced and/or divergentgenetic variation. Therefore, replacement of local populations by cultivated ones or gene flow fromcultivated populations to wild populations may represent a threat for the in situ conservation of wildcornflower.In this study, we described and compared the genetic diversity and genetic structure of wildpopulations sampled throughout France with that of plants sampled in flower fallows and fromcommercial seed lots. Plants originating from more than fifty wild populations, seven flower fallowsand twelves commercial seed lots were genotyped with seven microsatellite markers.A large genetic diversity and relatively low genetic differentiation (Fst = 0.128) was revealed amongwild populations, indicating a rather low genetic impact of demographic regression and populationfragmentation on cornflower. Most horticultural populations had a different genetic makeup thanwild populations. Flower fallows were genetically intermediate, suggesting that genetic mixingbetween wild and horticultural sources takes place within them. As this may negatively impact thelocal adaptation of wild populations, we advocate that cornflower seeds of wild, local origin areused in seed mixtures for flower fallows and flower strips