EVIDENCE FOR COMMON GENETIC MECHANISMS CONTROLLING THE TOLERANCE OF SUDDEN SALT STRESS IN THE TRIBE TRITICEAE

Previous studies in several Triticeae species have suggested that salt tolerance is a polygenic trait, but that genes on some chromosomes co nfer better tolerance to salt stress than others. This suggests an int riguing possibility that there may be a similar basis for salt toleran ce in the species of the tribe Triticeae. In this study, chromosomal c ontrol of the tolerance to sudden salt stress, measured as the mean ra te of leaf elongation in solution cultures with a single increment of 200 mM NaCl, was investigated in the genomes of cultivated barley (Hor deum vulgare L.), rye (Secale cereate L.), and Dasypyrum villosum (L.) Candargy by using disomic addition lines of individual pairs of chrom osomes or chromosome arms of each of the three species in the 'Chinese Spring' wheat genetic background. It was observed that the chromosome s of homoeologous groups 3, 4, and 5 in barley, 5 and 7 in rye, and 4 and 6 in D. villosum carry loci with significant positive effects on s alt tolerance. Increased doses of chromosomes of group 2, however, red uce or do not increase the tolerance to salt stress. These results are in agreement with a previous study of the tolerance of this salt stre ss regime in wheat and wheatgrass Lophopyrum elongatum. A ranking anal ysis of the chromosomal effects within each genome of the five Tritice ae species investigated in this and previous studies revealed that the chromosomes of homoeologous groups 3 and 5 consistently confer large positive effects on the tolerance of sudden salt stress, while the chr omosomes of homoeologous group 2 in increased dose have no or negative effects on the tolerance. This strongly suggests that species of the tribe Triticeae share some common genetic mechanisms of tolerance of s udden salt stress. The findings in this study give credence to the pro posal that wild relatives can be exploited in the development of wheat cultivars with greater tolerance to salt stress.