Enhancing interaction of recessive intermedium genes of barley in combinations with the six‐row gene hex‐v

The interactive competence of a number of genes promoting lateral floret development in barley was studied with particular reference to the interaction in dihybrid and trihybrid F 2 segregations after crossing involving the six‐row locus hex‐v and the three most frequently mutating recessive intermedium loci. int‐a, int‐c . and int‐e . The former locus was represented by the mutation hex‐v 3 (derived from the two‐row variety ‘Bonus’) and the allelic state hex‐v A in the six‐row commercial variety ‘Agneta’. The latter loci were each represented by three allcles ( ‐a 9 , ‐ a 10 ‐ a 27 ; ‐ c 5 ‐ c 13 ‐ c 29 ; ‐ e 20 ‐e 23 ‐e 65 ) derived from the two‐row varieties ‘Bonus’ or ‘Foma’, whereas ‘Agneta’ contributed the int‐c allele ‐ c A . F 2 data for lateral floret characters (awn length. fertility, seed size) were contrasted to standards considered to provide the phenotypic spectra corresponding to the different genotypic constituents of the F 2 segregations. The analyses of observed data in relation to expectations on various hypotheses for interaction between hex‐v and the recessive int genes led to the following main conclusions. In no case were there indications of total failure to enhance the phenotypic expression above the level of the corresponding standard categories. The degrees of phenotypic enhancement may differ among characters of lateral floret development, among int loci, and among allelic states of the latter, whereas differences between the two representatives of hex‐v were not discernible.