Genetical and physiological studies of gibberellic acid insensitivity in semidwarf rye

Because of the breeding value of gibberellic acid (GA 3 ) insensitive semidwarf genotypes in wheat, a screening for GA 3 response within a collection of semidwarf ryes was initiated and up to now four genotypes (‘Moskowskij Karlik’, ‘Gülzow kurz’, ‘R18’, ‘Dwarf C’) were found to be insensitive to applied gibberellic acid. In contrast to wheat, where all of the known alleles for GA insensitivity are (partially) dominant, the genetical studies did show that these four genotypes are carrying recessive alleles. Furthermore, it was found that the alleles of ‘Moskowskij Karlik’ and ‘R18’ seem to have the same locus on chromosome 5R, whereas the GA insensitivity of ‘Giilzow kurz’ and ‘Dwarf C’ is governed by two alleles of a different locus on chromosome 7R. None of the identified alleles was located on chromosome 4R, which could have been expected from the homoeologous relationships to wheat chromosomes 4B and 4D, which are critical for GA insensitivity. Studies on endogenous levels of gibberellins are in accordance with the genetical results, and suggest the GA insensitivity in rye to be caused by a different mechanism, compared to wheat.