Intensive Management Reduces Genetic Diversity of Dactylis Glomerata in Swiss Permanent Grassland.

Genetic diversity, i.e. the diversity within species and populations, is an important component of biodiversity which may substantially contribute to the productivity, adaptability and sustainability of grassland ecosystems. Although the importance of grassland habitats as a reservoir of genetic resources is generally recognized, little is known about the effect of environmental factors and agricultural land use on genotypic and phenotypic diversity.

This study aimed to investigate orchard grass (Dactylis glomerata), a perennial forage grass well adapted to a broad range of temperate environments as a model species to (i) assess the effect of management practices and habitat characteristics on genetic diversity, and to (ii) establish a relationship between habitat diversity, species and genetic diversity.

Twenty orchard grass populations were sampled from alpine, permanent grassland habitats, contrasting in respect to organic and conventional farming systems, management intensity and environmental conditions. Genetic diversity was analyzed using 29 simple sequence repeat markers (SSRs) and 11 morpho-physiological traits evaluated in a field experiment.

Nei’s unbiased gene diversity (H_E) revealed a high genetic diversity (0.50 – 0.55). Most of the genetic variation resided within populations (97.9%). Genetic diversity was significantly influenced by intensification of management resulting in a decrease of genotype diversity within sites (r = -0.50, p = 0.02). Furthermore, phenotype evaluation revealed significant influence of management on Dactylis glomeratapopulations based on selected traits. However, within- and between-population genotypic and phenotypic diversity was neither correlated with faming systems, nor with plant species diversity within and among sites. Habitat characteristics and environmental conditions showed no significant effect.

Facing uncertain climatic changes and an increasing need for sustainable management of resources, the insights gained may be particularly valuable for the in situ conservation of valuable genetic resources of grassland species. Furthermore, they support the improvement and targeted selection of ecotypes for breeding programs.