title: Intron-length polymorphism identifies a Y2K4 dehydrin variant linked to superior freezing tolerance in alfalfa.
abstract: Breeding alfalfa (Medicago sativa L.) with superior freezing tolerance could be accelerated by the identification of molecular markers associated to that trait. Dehydrins are a group of highly hydrophilic proteins that have been related to low temperature tolerance. We previously identified a dehydrin restriction fragment length polymorphism (RFLP) among populations recurrently selected for superior tolerance to freezing (TF). Analysis of crosses between genotypes with (D+) or without (D-) that RFLP revealed a significant impact on freezing tolerance. In this study, we sought to develop a PCR marker for freezing tolerance based on prior evidence of a relationship between size variation in Y(2)K(4) dehydrins and the RFLP. Results confirm the enrichment of Y(2)K(4) sequences of intermediate size (G2 group) in response to recurrent selection and in the D+ progeny. Analysis of genomic sequences revealed significant intron-length polymorphism (ILP) within the G2 group. G2 sequences with a characteristic short intron were more frequently found in D+ genotypes. Amplification using sequence-characterized amplified region (SCAR) primers bordering the intron confirmed an increase in the number of fragments with small introns in the D+ progeny and in the ATF5 population obtained after five cycles of recurrent selection for superior TF within the cultivar Apica (ATF0). Conversely, there was a reduction in the number of fragments with long introns in the D+ progeny and in ATF5 as compared to ATF0. Recurrent selection for superior tolerance to freezing in combination with ILP identified a sequence variant of Y(2)K(4) dehydrins associated to the phenotypic response to selection.
authors.affiliation: Crops and Soils Research and Development Center, Agriculture and Agri-Food Canada, 2560 Hochelaga Blvd., Quebec, QC, Canada. yves.castonguay@agr.gc.ca
authors.forename: Yves
authors.initials: Y
authors.lastname: Castonguay
authors.forename: Marie-Pier
authors.initials: MP
authors.lastname: Dubé
authors.forename: Jean
authors.initials: J
authors.lastname: Cloutier
authors.forename: Réal
authors.initials: R
authors.lastname: Michaud
authors.forename: Annick
authors.initials: A
authors.lastname: Bertrand
authors.forename: Serge
authors.initials: S
authors.lastname: Laberge
mesh_terms: D000064:Acclimatization / Q000235:genetics*; D000595:Amino Acid Sequence; D001483:Base Sequence; D019295:Computational Biology; D003433:Crosses, Genetic; D017931:DNA Primers / Q000235:genetics; D005615:Freezing; D005838:Genotype; D007438:Introns / Q000235:genetics; D000455:Medicago sativa / Q000235:genetics*; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics*; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic / Q000235:genetics*; D012641:Selection, Genetic; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D017931:DNA Primers; D010940:Plant Proteins; C070556:dehydrin proteins, plant
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