THE KARYOTYPE ANALYSIS AND ORIGIN OF CHROMOSOME 4A AND GENOMES B AND G OF WHEAT GENERA

Karyotypes and Giemsa N-banding patterns of 9 hexaploid species,8 tetraploid species and 2 diploid species, and the probable donor of B genome, Aegilops sharonensis,have been studied by means of new method of preparing mitotic chromosome specimen in plant and N-banding technique. The results obtained show that all chromosomes of Triticum are metacentric and submetacentric The karyotype has "2A" type, and the asymmetry increases as plpidy rises. The karyotypes among species have definite differences. All chromosomes of B and G genomes and 4A show N-bands, but the other chromosomes show no N-bands or only weak centromeric bands. The banding patterns of B genome of hexaploid wheats are basically same, but N-bands have definite differences among species of B genome of tetraploid wheats. The number and distribution of the bands of G genome of T.timopheevi wheat and B genome have distinct differences. The karyotype and the banding pattern of Ae.sharonersis are similar to B genome, and it might be the donor of B genome. Diploid species show no Nbands and have no chromosome correspondent to 4A according to banding patterns. Therefore, further study on the origin of 4A chromosome is needed.