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Intron-length polymorphism identifies a Y<inf>2</inf>K<inf>4</inf> dehydrin variant linked to superior freezing tolerance in alfalfa

Castonguay, Y., Dubé, M.P., Cloutier, J., Michaud, R., Bertrand, A., Laberge, S. (2012). Intron-length polymorphism identifies a Y<inf>2</inf>K<inf>4</inf> dehydrin variant linked to superior freezing tolerance in alfalfa, 124(5), 809-819. http://dx.doi.org/10.1007/s00122-011-1735-0

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 Y2K4 dehydrins and the RFLP. Results confirm the enrichment of Y2K4 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 Y2K4 dehydrins associated to the phenotypic response to selection. © 2011 Her Majesty the Queen in Rights of Canada, as represented by the Minister of Agriculture and Agri-Food Canada.

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