The author (Yagi 1962b, 1963, 1966) previously reported the fact that the quantity of the nile blue granules observed in the fat-body cells of the prepupa of D. melanogaster has the positive correlation with the amount of the brown pigment in the adult eyes. In order to confirm this fact, various experimental crosses were made among five different strains and the resulted F1 hybrids were tested for the quantities of the N.B.G. in relation to their eye colors. In results, it was proved that, whichever type their parents belonged to, the offspring whose prospective adult eye colors were the normal with enough amount of the brown pigment contained the large quantities of the N.B.G. in the prepupae, while the offspring whose prospective eye colors were paler than the normal with the lack or insufficient amount of the brown pigment contained less amount of the N.B.G. These results suggest that the genetic factors controlling the quantity of the N.B.G. and the amount or production of the brown pigment are the common.
The distribution of lost chromosomes in Patau's grouping was studied in cells with 45 normal chromosome complements. A total of 132 metaphase plates were karyotyped from cultured peripheral leukocytes and 35 from bone marrow cells. The pattern of missing chromosomes was found to be significantly different from expectation based on the number of chromosomes per group. Unusually low incidences of missing chromosomes of groups A, B and F were discovered.
In order to make clear the relationships among the B, C and D genomes, this experiment was designed. Eight BF1 hybrids, consisting of the F1 hybrids of the A×BC and A genome and the F1 hybrids of the A×CD and A genome, were studied cytologically. From a large number of flowers pollinated 131 seeds (43 lines) of various degrees of development were obtained. Out of 29 lines (82 seedlings) which grew up to adult plants, 8 were cytologically studied. At MI, the number of bivalents observed ranged from 8 to 16 (mean=11.97 to 13.20) in the BF1 hybrids of the genomic cross-combinations, ABC×A, from 8 to 15 (mean=11.33 to 12.35) in ACD×A. Based on chromosomal behaviors at meiosis, the author postulated that the number of chromosome pairings between B and C or C and D genomes ranges from 0 to 4 (mean=0.56 to 1.75) or from 0 to 3 (mean=0.17 to 0.43) at the maximum, respectively. This fact shows that the most of bivalents formed at meiosis of the F1 hybrids in the genomic cross-combinations, A×BC, or A×CD, arose through the homology or partial homology between A and C genomes.
Dry seeds of a Japanese variety of common wheat (6x), Shinchunaga, were irradiated with 10 to 40 kR of gamma rays from 60Co. No chlorophyll mutations were detected, while various kinds of morphological mutants were found in the X2 through X8 generations. About one third of the morphological mutants were found in the X2, another third in the X3, and the remaining third in the later generations. The lack of any chlorophyll mutation and the frequent occurrence of various morphological mutations are considered to indicate that there is a difference in the extent of differentiation in this polyploid plant between essential genes such as those for chlorophyll production and non-essential genes such as those determining spike length or density. Many speltoid, compactoid, squareheaded, lax-spiked and dense-spiked mutants were found, as well as various other mutants. Cytogenetical investigations were performed on these morphological mutants, and it was found that most of these morphological mutants were caused by various chromosomal aberrations, such as deficiencies, telocentrics, isochromosomes, and various aneuploid constitutions.
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.
Excised pith tissues of tobacco (Nicotiana tabacum, 2n=48) were cultured on the Skoog's nutrient-agar medium containing 2.0 mg/l of indoleacetic acid (IAA) and 0.2 mg/l of kinetin. The first mitosis in parenchymatous cells of the cultured pith took place after 5-7 days of the culture. Chromosome number was already varied between 40 and 215. Frequencies of di- and tetraploid cells were only 12.5% and 17.5%, respectively. About 50% of the cells had more than 100 chromosomes. The in vivo pith tissue of tobacco seems to consist of cells with variable chromosome numbers. At the second mitosis taking place 1-2 days after the first mitosis a similar variation in chromosome numbers was observed, but the frequency of cells with more than 100 chromosomes was greatly reduced (22.7%). Callus tissues, that were derived from a pith segment and subcultured for about one and a half years, grew vigorously on the medium supplemented with 3.0g/l casein hydrolysate. Nearly 70% of their cells had chromosome numbers between 77 and 96. Karyotype of the callus cell also differed from that of the normal root-tip cell. As to chromosome number, the cell population became much more uniform after a long period of subculture.
1. Allohexaploid, minuta-australiensis (2n=72, BBCCEE), was synthesized successfully, treating with 0.05% colchicine the young shoot vegetatively propagated from buds on the node of the F1 hybrid. 2. In MI of PMCs, bivalent chromosomes ranging from 29 to 36, and univalents from 0 to 14 were observed. The average chromosome configuration was 35.12II+1.76I, the mode of bivalents and univalents being 36 and 0 respectively. These bivalents paired tightly. More than a half of univalents observed were assumed to be the result of precocious division of bivalents. 3. In spite of the homogenetic association occurring exclusively in respective three sets of different genomes of the amphiploid, several meiotic irregularities were observed. Accordingly, the fertilities of pollen and seed were unexpectedly low, being 22.8% and 14.4% respectively. Some unknown cause or causes other than the chromosomal homology must have been responsible for such situation. 4. The present amphiploid minuta-australiensis differs from the male-sterile amphiploid sativa-minuta only in its containing E genome instead of A. Therefore, one of the causes of male-sterility of amphiploid sativa-minuta, and perhaps of sativa-latifolia, seems to be found in A genome itself or to be due to the interaction between A and BC or CD genomes. Accordingly, E genome of O. australiensis expressed clearly different effect from A, on the development of anthers in amphiploid level, when brought together with BC genomes. 5. Amphiploid, minuta-australiensis, showed the gigas nature in most characters, and it had fewer tillers and set seeds more sparsely. Under a controlled short-day condition it shot the panicle about 10 days later than the original F1.