The nature and genetic control of gibberellin insensitivity in dwarf wheat grain

Abstract

Eight dwarf and semi-dwarf varieties, covering a range of genetic sources of dwarfism, and four tall varieties of wheat were tested for their response to a range of GA concentrations by release of the enzyme a-amylase. The two dwarfs, Minister Dwarf and Tom Thumb, were found to be insensitive compared with the remaining 10 varieties; among the latter, differences in minimum levels of sensitivity were found that were unrelated to height phenotype. Transplant experiments, in which embryos of one genotype were grown on the endosperm of another, showed that the lack of response was a function only of the endosperm tissue and that GA release from the embryos of insensitive varieties during germination was similar to that of sensitive genotypes. The close relationship between coleoptile length and endosperm GA- insensitivity indicated that this character was controlled by the Gat 3 locus previously located on chromosome 4A. In some crosses the character displayed a pattern of inheritance that would be expected in a triploid tissue for a single gene. However in crosses of varieties carrying Gai 3 with Norin 10-Brevor 14, which has a GA-sensitive endosperm, a more complex inheritance was found, indicating that Norin 10-Brevor 14 also carried a gene or genes which can increase GA-insensitivity. © 1975 The Genetical Society of Great Britain.