Chromosome-mosaics Observed in a Variety of Wheat, “Shirahada”

抄録

1) A variety of wheat, “Shirahada”, showed an abnormal meiotic behavior, “chromosome-mosaics”. In every plant selected at random there were to be seen aneuploid PMC's such as “hypo-” or “hyper-” cells mixed together with euploid ones in the same anther-loculus. Especially the “hypo-” cells with less than 2n chromosome number were frequently noticed. Such aberrant PMC's are usually characterized by a relatively large number of unpaired chromosomes.
2) In euploid PMC's there were often observed one or two pairs of univalents while multivalent chromosomes such as trivalent or tetravalent were rarely discovered. On an average about 18% of aneuploid PMC's observed had such irregularities. Laggards and bridges were also frequently observed in both 1st and 2nd anaphase, especially so in 1st division.
3) An upset in mitosis which was induced by gene-controlled spindle abnormalities just before meiosis seems to be the probable cause of the origin of these hypo- and hyper-cells.
4) As a result of such irregularities in the meiotic division, there appeared frequently in the progenies various types of aneuploids, especially monosomics (2n=41). In the self-pollinated progenies of a plant with the lowest seed fertility, a series of aneuploids having 2n=39, 40 and 41 chromosome numbers were found together with euploids (2n=42).