INVOLVEMENT OF CHROMOSOME-5A AND CHROMOSOME-5D IN COLD-INDUCED ABSCISIC-ACID ACCUMULATION IN AND FROST TOLERANCE OF WHEAT CALLI

The relationship between frost tolerance and abscisic acid (ABA) accum ulation was studied in callus cultures of three wheat cultivars differ ing in the level of frost-tolerance, and of the 5A and 5D chromosome s ubstitution lines from the frost-tolerant variety 'Cheyenne' into fros t-sensitive 'Chinese Spring'. Following cold hardening, the increase i n ABA level in the calli of the two frost tolerant cultivars was signi ficantly higher than in those of the frost-susceptible cultivar. Simil arly, in 5A and 5D substitution lines, significantly higher ABA levels were detected than in the recipient 'Chinese Spring'. One week-long A BA treatment at 26-degrees-C induced a significantly higher level of f rost tolerance than that achieved by cold hardening, irrespective of t he frost sensitivity of the examined genotypes.