Temperature‐Sensitive Mutants in Hordeum vulgare L.¹

Chlorophyll content in the primary leaf of 76 viable chlorophyll‐deficient barley ( Horedum vulgore L.) mutants was determined in seedlings grown at 10 and 26 C. The ratio of chlorophyll content at 10 C to that at 26 C (10/26 ratio) ranged from 0.05 to 8.00 in the mutants. The 28 mutants with ratios of 0.5 or less were considered to be cold‐temperature sensitive ( cts ) and the 16 mutants with ratios of 2.0 or greater were considered to be high‐temperature sensitive ( hts ). The remaining 32 mutants were classified as temperature‐insensitive ( ti ). Thirty‐four of the mutant genes have been located on specific chromosomes. Of these, 10 were cts , 8 ti , and 6 hts . The 10 cts mutant genes appeared to be widely distributed among the 7 chromosomes with all but chromosome 6 having at least 1 mutation. The six hts mutant genes were located on chromosomes 1, 2, and 5. The 18 ti mutant genes were located primarily on chromosomes 1, 2, 3, and 4 with chromosomes 5 and 6 having only 1 mutant gene each. Five of the mutant genes showed cytoplasmic inheritance. Of these, three were cts and two hrs. The cts mutants EMS 18, S 1, and Coast V, grown at 10 C, and the hts mutant, dES 26, grown at 26 C, were as lethal as albino seedlings grown at the same temperatures.