Genetic analysis of low-temperature tolerance in winter wheat
Chodaparambil, Sanjay Velandy
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Winter wheat has a higher yield over spring sown wheat and has many ecological and agronomic advantages. However, low temperature (LT) stress is one of the major abiotic factors which limit increased crop production. LT-tolerance in winter wheat is a quantitative trait and molecular and genetic evidence suggest that LT-tolerance is governed by a number of genes with complex interactions. In order to identify and characterize the chromosomal regions conferring LT-tolerance, a doubled haploid (DH) mapping population was utilized from two winter wheat parents Norstar and Cappelle-desprez which have an identical vrn-1 locus but differ in their potential LT-tolerance (Båga et al., 2006a; 2006b). Norstar has an LT50 of -21°C and Cappelle-Desprez has an LT50 of -13°C (Båga et al., 2006a; 2006b). In this study, molecular markers such as simple sequence repeats (SSRs) and amplified fragment length polymorphisms (AFLPs) were used to construct a linkage map of a Norstar x Cappelle-desprez cross and to identify markers and regions associated with LT-tolerance. A linkage map was assembled with a total genetic length of 2292 cM comprising 443 SSR and 197 AFLP markers. A major QTL (Quantitative trait loci- a region of DNA that is associated with a phenotypic trait) for LT-tolerance was identified on chromosome 5A which has been associated with a cluster of C-repeat binding factors (CBFs). The QTL identified in this study is similar to the Fr-2 locus in diploid and hexaploid wheat, also associated with LT tolerance. A previously constructed Norstar BAC library (Ratnayaka et al., 2005) was screened to identify putative CBF clones. Mapping of the CBF positive clones to the major QTL identified on chromosome 5A will help in identifying the key CBF gene(s) contributing to the LT-tolerance trait.