title: Abiotic stress QTL in lettuce crop-wild hybrids: comparing greenhouse and field experiments.
abstract: The development of stress-tolerant crops is an increasingly important goal of current crop breeding. A higher abiotic stress tolerance could increase the probability of introgression of genes from crops to wild relatives. This is particularly relevant to the discussion on the risks of new GM crops that may be engineered to increase abiotic stress resistance. We investigated abiotic stress QTL in greenhouse and field experiments in which we subjected recombinant inbred lines from a cross between cultivated Lactuca sativa cv. Salinas and its wild relative L. serriola to drought, low nutrients, salt stress, and aboveground competition. Aboveground biomass at the end of the rosette stage was used as a proxy for the performance of plants under a particular stress. We detected a mosaic of abiotic stress QTL over the entire genome with little overlap between QTL from different stresses. The two QTL clusters that were identified reflected general growth rather than specific stress responses and colocated with clusters found in earlier studies for leaf shape and flowering time. Genetic correlations across treatments were often higher among different stress treatments within the same experiment (greenhouse or field), than among the same type of stress applied in different experiments. Moreover, the effects of the field stress treatments were more correlated with those of the greenhouse competition treatments than to those of the other greenhouse stress experiments, suggesting that competition rather than abiotic stress is a major factor in the field. In conclusion, the introgression risk of stress tolerance (trans-)genes under field conditions cannot easily be predicted based on genomic background selection patterns from controlled QTL experiments in greenhouses, especially field data will be needed to assess potential (negative) ecological effects of introgression of these transgenes into wild relatives.
authors.affiliation: Institute for Biodiversity and Ecosystem Dynamics, Universiteit van Amsterdam Amsterdam, The Netherlands.
authors.forename: Yorike
authors.initials: Y
authors.lastname: Hartman
authors.affiliation: Institute for Biodiversity and Ecosystem Dynamics, Universiteit van Amsterdam Amsterdam, The Netherlands ; NERC, Centre for Ecology and Hydrology Wallingford, UK.
authors.forename: Danny A P
authors.initials: DA
authors.lastname: Hooftman
authors.affiliation: Wageningen UR Plant Breeding, Wageningen University and Research Centre Wageningen, The Netherlands.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Uwimana
authors.affiliation: Institute for Biodiversity and Ecosystem Dynamics, Universiteit van Amsterdam Amsterdam, The Netherlands.
authors.forename: M Eric
authors.initials: ME
authors.lastname: Schranz
authors.affiliation: Wageningen UR Plant Breeding, Wageningen University and Research Centre Wageningen, The Netherlands.
authors.forename: Clemens C M
authors.initials: CC
authors.lastname: van de Wiel
authors.affiliation: Wageningen UR Plant Breeding, Wageningen University and Research Centre Wageningen, The Netherlands.
authors.forename: Marinus J M
authors.initials: MJ
authors.lastname: Smulders
authors.affiliation: Wageningen UR Plant Breeding, Wageningen University and Research Centre Wageningen, The Netherlands.
authors.forename: Richard G F
authors.initials: RG
authors.lastname: Visser
authors.affiliation: Genome Center and Department of Plant Sciences, University of California Davis, California.
authors.forename: Richard W
authors.initials: RW
authors.lastname: Michelmore
authors.affiliation: Institute for Biodiversity and Ecosystem Dynamics, Universiteit van Amsterdam Amsterdam, The Netherlands.
authors.forename: Peter H
authors.initials: PH
authors.lastname: van Tienderen
keywords: Abiotic stress; Lactuca; QTL; Transgene; crop–wild hybrids; environmental risk assessment