IDENTIFICATION OF THE CHROMOSOMES CONTROLLING GAMMA-RAY- INDUCED MUTANT CHARACTERS IN A JAPANESE VARIETY OF COMMON WHEAT

Abstract

Identifications of the chromosomes controlling mutant characters were carried out on twelve different strains of gamma-ray-induced mutants of Shinchunaga wheat, utilizing the monosomic and ditelosomic series of Chinese Spring. Speltoid mutants were due to the loss of a part or the whole of the long arm of chromosome 5A, or due to the loss of the whole chromosome. Compactoid-squareheaded mutants were caused by duplications or increased dosages of the long arm or the whole of this chromosome. Squareheaded mutants having no relationship with compactoids were induced by the loss of the short arm of the same chromosome. Lax-spiked mutants were the result of the nullisomic condition of chromosome 6D or of the loss of one of the 6D arms.It was found that, in Shinchunaga, tri-5A, tetra-5A and penta-5A complements produce squareheaded, subcompactoid and compactoid mutants, respectively, whereas, in Chinese Spring, tri-5A and tetra-5A yield subcompactoid and compactoid plants, respectively (Table 1).Mutants implicating chromosome 5A were much more frequently detected than those involving any other chromosomes. However, it is concluded that this result does not indicate any particular high radiosensitivity of this chromosome but it only reflects the fact that this chromosome carries a few genes which loss results in striking phenotypic changes even in hetero- or hemizygous conditions, thus, mutants involving this chromosome were more easily detected.