Gene interaction of induced intermedium mutations of two-row barley: I. Double mutant recombinants

Abstract

From 69 induced intermedium mutants isolated from three Svalof commercial varieties of two-row spring barley, ‘Bonus’, ‘Foma’, and ‘Kristina’, and localized to 9 different int loci, double mutant recombinants were available in 1384 of the 1879 possible combinations among non-allelic mutants. These double mutant segregates, without exception, showed an apparent, strong degree of synergistic intreraction between mutant genes that by themselves cause rather modest changes in the normal two-row spike. They rank in three groups in their spike development: six-rowed. irregular, and deformed. There are apparent differences, not only among int loci, but also among alleles in the ability to co-operate for six-rowed spikes in double mutants. A complex pattern of factors promoting the six-rowed spike development in double mutants is indicated: the ranking among phenotypes for individual int alleles; the particular int locus serving as partner to a series of alleles to form double mutants; the state of the allele, as more flexible or more rigid. Success seems to depend on the particular constellation of loci and alleles.