Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 12, 2009
Publication Date: June 1, 2009
Citation: Greer, S.P., Rinehart, T.A. 2009. In Vitro Germination and Dormancy Responses of Hydrangea macrophylla and Hydrangea paniculata Seeds to Ethyl Methane Sulfonate and Cold Treatment. HortScience. 44(3):764-769. Interpretive Summary: For more than four decades, DNA alkylating agents like ethyl methanesulfonate (EMS) have been used to increase allelic diversity in plants and generate breeding lines. Recent reverse genetic advances such as TILLING (Targeting Induced Local Lesions IN Genomes) have broadened the application of EMS to plant science, empowering scientists to screen for specific mutant alleles in the absence of a mutant phenotype, even when very little genome sequence information exists. In addition to providing functional genomic information, genetic variations created by chemical mutagenesis and/or discovered by TILLING are exempt from regulatory approval requirements for transgenic crops. In spite of similarities regarding DNA end-products of EMS exposure, rates of chemical mutagenesis are known to differ significantly between plant species and even within species . As a result, proper application of chemical mutagens most often requires protocols to be independently established for targeted species, cultivars, and ecotypes. To our knowledge, there are no published parameters for EMS application to Hydrangea macrophylla or Hydrangea paniculata and there are no published reports as to the relative effectiveness of this mutagen in these species. In addition, nothing is known about the effects of EMS upon the viability, dormancy, or germination of Hydrangea seed. To remedy this lack of information, we performed a series of experiments using increasing EMS dosage in an effort to estimate the range of damage tolerated by Hydrangea seed and to elucidate intraspecific cultivar variation in terms of viability, dormancy, and germination.
Technical Abstract: In order to determine the optimal conditions for mutagenesis of Hydrangea macrophylla and Hydrangea paniculata, stratified and non-stratified seeds from representative cultivars were treated with 0.5%, 2.5%, and 5% ethyl methanesulfonate (EMS). In the M1 generation, most non-stratified H macrophylla seeds treated with 2.5 and 5% EMS had substantially lower germination percentages; H. paniculata overall seed germination percentages did not differ from controls until EMS concentration reached 5% EMS. Stratification of H. macrophylla and H. paniculata seed made germination more tolerant to all concentrations of EMS tested, even increasing germination of seed from most H. macrophylla cultivars substantially above control levels at lower dosages; overall germination of stratified seed from H. paniculata cultivars rose substantially above control levels even at the highest dosages. EMS effects on Hydrangea seed dormancy and viability mirrored those seen in overall germination; increasing dosage caused declines in dormancy and viability of non-stratified seed versus controls, while application of these same doses to stratified seed caused marked increases or relatively minor change in dormancy and viability versus controls.