抄録
The segregation ratio of heterozygous fatuoids with 20II+c, type b in the II-series, is found to be very variable, correlating with their different fertility (Tables 1 and 2). Dwarf homozygous fatuoids having 40 chromosomes (2n-2c), where the synapsis usually fails, are produced in a high proportion with the increase of the fertility of the parents, while, on the contrary, heterozygous fatuoids (20II+c) are found in less frequency. Notwithstanding the variation of fertility normal plants (20II+cc) are obtained almost in the same proportion (2.38-3.86%). Besides, in rare cases heterozygous fatuoids produce some aberrant segregates with exceptional chromosome combinations, which contain one or two of the segments, s1 and s2 of the c-chromosome.
(1). A few of homozygous fatuoids are found to have 20II+s1 and 20II+s1s1. They are dwarf and highly sterile, looking like those with 40 chromosomes (2n-2c).
(2). The somatic chromosome number of semi-dwarf and highly sterile heterozygous fatuoids is clearly counted to be 40+s2, in which the chromosome conjugation is usually lacking.
(3). A heterozygous fatuoids with 20II+cs1 is obtained in the progeny of homozygous fatuoid (20II+s1)×normal plant (20II+cc), with those having 20II+c.
From the correlation between the chromosome combination and morphological characters of these plants given above, the author has reached the conclusion that the genes for the cultivated type of the grain are carried in the shorter arm of the c-chromosome, s2 and a gene or genes for the synapsis in its longer arm, s1.
