CHROMOSOMAL CONTROL OF THE TOLERANCE OF GRADUALLY AND SUDDENLY IMPOSED SALT STRESS IN THE LOPHOPYRUM-ELONGATUM AND WHEAT, TRITICUM-AESTIVUML, GENOMES

The facultatively halophytic Lophopyrum elongatum, closely related whe at, Triticum aestivum, and their amphiploid tolerate salt stress bette r if they are gradually exposed to it than if they are suddenly stress ed. Lophopyrum elongatum has greater tolerance of both forms of salt s tress than wheat, and its genome partially confers this tolerance on t heir amphiploid. Chromosomal control of the tolerance of both stress r egimes in the L. elongatum and wheat genomes was investigated with dis omic and ditelosomic addition lines and disomic substitution lines of L. elongatum chromosomes in wheat and with wheat tetrasomics. The tole rance of the sudden salt stress is principally controlled by L. elonga tum chromosomes 3E and 5E and less by 1E, 2E, 6E, and 7E and the toler ance of gradually imposed salt stress principally by chromosomes 3E, 4 E, and 5E, and less by chromosome 1E and 7E. Ditelosomic analysis indi cated that genes conferring the tolerance of sudden stress are on chro mosome arms IEL, 5ES, 5EL, 6EL, 7ES and 7EL and those controlling the gradual stress regime are on 1ES, 1EL, 5ES, 5EL, 6ES, 7ES, and 7EL. In wheat, chromosomes in homoeologous groups 1, 3, and 7 and chromosomes in homoeologous groups 1, 4, and 6 were shown to enhance the toleranc e of suddenly and gradually imposed stress, respectively. The arms of chromosome 3E individually conferred tolerance to neither stress regim e. Chromosome 2E and wheat chromosomes 2B and 2D reduce the tolerance of both stress regimes in a hyperploid state. In 2E this effect was as sociated with arm 2EL. A potential relationship between the tolerance of these stress regimes and the expression of the early-salt-induced g enes is examined.