| (e) Narrow-leafed and Broad-leafed. The former has narrow long dark-green
leaves, thin and slightly short culms, while the latter possesses remarkably
broad hard light-green leaves, thick and tough culms. The former had 42
chromosomes including one partially deficient chromosome in the heterozygote,
and 42 chromosomes including two partially deficient chromosomes in the
homozygote; while the latter had 43 chromosomes including one fragment in
the heterozygote and 44 chromosomes including two fragments in the homozygote.
From these facts it is assumed that the former type mutants arise from the
partial deficiency of one chromosome bearing broad leaf promoting gene,
and that the latter type are produced by the partial duplication of the
same chromosome. (f) Trough-leafed. This type has short straws and hard dark-green trough-like leaves, the right and left margins of which are bent toward the reverse sides forming crescent-shaped troughs. This type mutants had 41 chromosome in the heterozygote, and the homozygote possessed 42 chromosomes including two partially duplicated chromosomes. These facts show that this type mutants are brought about by the partial duplication of one chromosome bearing trough leaf gene. (g) Short-strawed with normal ear (Type II). This newly found type differs from formerly reported short-strawed mutants. This type plants have thick and remarkably short straws and normal ears. The heterozygote had 42 chromosomes including one chromosome with duplicated long arm, while the homozygote possessed 42 chromosomes including two chromosomes with duplicated long arms. From these findings it is assumed that this type mutants may be caused by the duplication of one long arm of a chromosome which bears the short-straw promoting gene. (h) Other dwarf mutants. Three cytogenetic types of dwarfs are included here. All of them are highly sterile and have the culms shorter by one third than those of normal plants similarly. The first type has normal ear, and was observed to have 41 chromosomes in the heterozygote and 40 chromosomes in the homozygote. This type, therefore, is produced by the deficiency of one chromosome which bears normal straw promoting gene. The second type is very highly sterile and has lax ear. The heterozygote of this type had 40 chromosomes including one partially deficient chromosome, and the homozygote possessed 40 chromosomes including two partially deficient chromosomes. These findings show that the lax ear form of this type is caused by the partial deficiency of one chromosome and dwarfness is originated from the deficiency of one pair of other chromosomes. The third type of dwarf mutants has dense ear. The heterozygote of this type had 40 chromosomes including one partially duplicated chromosome, while the homozygote possessed 40 chromosomes including two partially duplicated chromosomes. These facts show that the dwarfness of this type is caused by the deficiency of one pair chromosome and the dense ear is brought about by the partial duplication of another chromosome. (i) Macurescens. This mutant appears very rarely and yellow spots become visible toward the laster part of March. The heterozygote and the homozygote had both 42 chromosomes and the chromosome behaviors in meiosis of PMC's were very regular. From these facts this mutant is assumed to be caused by minute delation of one chromosome or point mutation. |
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