Methodology of gene transfer by homoeologous recombination into Triticum turgidum: transfer of K+/Na+ discrimination from Triticum aestivum

Triticum aestivum (2n = 6x = 42) differs from T. turgidum (2n = 4x = 28) by superior ability to exclude Na+ and accumulate K+ under salt stress. Chromosome 4D has a major affect on the enhancement of this trait in T. aestivum. To transfer this trait to T. turgidum, T. turgidum chromosome 4B was targeted for homoeologous recombination with chromosome 4D in the genetic background of T. turgidum, utilizing recessive mutant ph1c to enhance meiotic heterogenetic chromosome pairing. Since the basis of the genetic control of this trait by chromosome 4D was not known, a large population of random recombinant lines involving the alien chromosome and the wheat chromosome had to be produced. It was hypothesized that assaying lines in such a population for the trait would facilitate identification of those in which the gene or genes controlling the trait were incorporated into the T. turgidum chromosome. Forty lines with recombinant chromosomes were obtained. Thirty-nine recombination events involving chromosome 4D involved the targeted chromosome 4B. The ratio of K+/Na+ in leaves of plants grown under salt stress was determined for 27 lines. Nine lines showed enhanced K+/Na+ ratios. Evidence is presented that this trait is controlled by a single gene locus, designated here as Kna1. The locus is distal to the subterminal C-band in the long arm of chromosome 4D.Key words: wheat, linkage map distortion, salt stress tolerance.