Plant Genome III Conference

THE MAPPING OF THE WHEAT K+/Na+ DISCRIMMINATOR LOCUS, KNA1, AND THE SUBSEQUENT CONSTRUCTTON OF MOLECULAR MARKERS FOR ITS SELECTION IN SEGREGATING POPULATIONS.

Triticum aestivum (2n=6x=42) and Triticum turgidum (2n=4x=28) are two of the most important wheat species as regards to food production. Triticum aestivum is better than T. turgidum at preventing the uptake of sodium while still allowing the utilization of potassium in its surrounding root environment under salt stress. This leads to a higher K+/Na+ ratio within the leaves of T aestivum than within the leaves of T turgidum, and higher salt tolerance. Chromosome 4D of T aestivum exerts a major effect on this trait. Targeted homoelogous recombination between T aestivum chromosome 4D and T turgidum chromosome 4B showed that the long arm of chromosome 4D (4DL) controls K+/Na+ discrimination. Segregation analysis indicates that there is a single locus in 4DL that controls K+/Na+ discrimination, and this locus was designated Knal. Field trials tested the significance of this locus for salt tolerance. Plants containing Knal had higher K+/Na+ ratios, and a higher tolerance of salinity as measured by yield, than those which did riot contain Knal. Several restriction fragment length polymorphic (RFLP) markers were shown to be completely linked to the Knal locus. Genomic clones of these markers were sequenced and PCR primers designed, The linked RFLP markers and PCR primers can now be used as tags for Knal, making it possible to follow the Knal locus in segregating populations, thus allowing the creation"on of more salt tolerant varieties of T turgidum.