Molecular Genetic Analyses Of The CBF Genes At The Barley Frost Resistance-H2 Locus.

Frost resistance-H2 is one of two major quantitative trait loci that affects freezing toleranceand winter hardiness of barley. Mapping coincident with Fr-H2 is a cluster of more than 14 genesencoding CBF transcription factors. To explore the possibility that the Cbfs may be the underlyingmolecular basis of Fr-H2, we have generated a large mapping population derived from the morefreezing tolerant genotype ‘Nure’, and the less freezing tolerant genotype ‘Tremois’, to both finemap the Fr-H2 interval, and to generate recombinants between the different Cbf genes.Concurrently, we have sequenced most of genetically colinear region encompassing the Cbf genesfrom these two barley genotypes with the goal of uncovering the underlying molecular basisexplaining Fr-H2. Screens for recombinant individuals from F2 populations consisting of morethan 3,698 meiotic events, and their subsequent phenotypic evaluation in F4 lines provided anestimated refined genomic interval of 4.6 cM for Fr-H2. Recombinants between seven of theestimated 14 Cbf genes under Fr-H2 have been identified and showed that the Cbf gene clusterspans 0.81 cM. Sequencing of the colinear genomic region revealed several key moleculardifferences that we hypothesize accounts for the phenotypic differences. Determining whether theCbfs underlie Fr-H2, and which gene or genes confers the capacity for greater freezing tolerancewill require the creation of near isogenic lines differing in their Fr-H2 alleles such thatrecombinants between the different Cbf gene orthologs and paralogs may be analyzed for theirphysiological capacity to survive freezing temperatures.