The writer found an unexpected occurrence of univalent chromosomes in the microsporogenesis of rice-plant in the summer of 1934. Materials were collected from plants cultivated in the glass-house at the Plant Breeding Institute of the Hokkaido Imperial University, Sapporo. All of the three varieties examined showed the same abnormality, the frequency being approximately 40% in average. The fixation numbers given in the tables indicate the varieties used, and the dates on which the fixation was made, as follows : Frequencies of asynaptic cells were counted in three following stages, diakinesis, prometaphase-I and the metaphase-I (Tables 1-4). It was found that the number of asynaptic cells in diakinesis suddenly decreased in prometaphase-I and again increased in metaphase-I. At metaphase-I, the univalents scatter randomly on the spindle, but it was often observed that each two univalents lie in close proximity (Figs. 2, 3, 8, etc.). Distribution of the univalents on the spindle was noted. Some of the univalents lie within the equatorial plate (Figs. 5, etc.), while the others scatter on the spindle. In the cells with two univalent chromosomes, the position of them was studied (Table 5), and it was found that the behaviour of the two univalents was not always at random. Data from Table 5 suggest that the univalents have a tendency to avoid entering the equatorial plate, and that when two univalents which are naturally homologous wander on the spindle, they are apt to take their position in the same side of the plate. These facts as the increase in the frequency of apparently normal cells at the first prometaphase where the repulsion force between chromosomes suddenly decreases, the tendency of each two univalents to lie in close proximity in the spindle and the tendency of two homologous univalents to be in the same side of the equatorial plate rather to lie in the different sides, all may be explained on one and the same hypothesis : the operation of an attractive force between the two homologous but unpaired univalents. The reason why asynapsis is caused in this case is unknown. But it was suggested that it might have perhaps been caused by some environmental conditions. The genetic effect which sometimes brings about asynapsis seems not to be applicable in this case. It is the writer's great regret, however, to mention that his subsequent experiments failed to detect what the very cause may have been. Most of the pollen grains were aborted. Fertility, too, was extremely low as shown below : An extremely bad harvest of rice was recorded in 1934 all other the northern parts of Japan. Besides failure of micro- and macrosporogenetic cytokinesis under low temperatures which was found by the writer (Sakai 1937 a; b, 1939), the unexpected and the cause-unknown asynapsis described above might have played a certain role in the bad harvest of rice of that year.
Since 1938, I have devoted myself to the genetic study of Drosophila montium. So far thirty mutant characters have been found and assigned to three linkage groups. The oogonial chromosome complex consists of four pairs of chromosomes : two large V-shaped pairs, a rod-shaped pair and a pair of small chromosomes which are V-shaped in Race A and rod-shaped in Race B. Presumably the linkage group whose mutant character has not been found, corresponds with the smallest chromosome. A more detailed cytological account will appear in the coming number of Cytologia. The description, locus, date of discovery and the ranking of each character are published. The tentative chromosome maps are shown in Fig.15.
In the present paper a theoretical consideration was made on the problems of differentiation and homology-relationship of the genom. Though tentatively the followings were concluded. (1) In two genoms which are in 'intimate homology', the chromosome pairing is nearly complete, the modal class of number of pairing per nucleus corresponding to the basic chromosome number, n (Fig. 1, a), while in the ease of 'remote homology' the number of pairing is considerably variable, the modal class being 0 (Fig. 1, b). A good example of these extreme pairing ways is found in Trillium Hague (3n=15, K1K2T). The mode of pairing between K1 and K2 represents intimate homology and that between (K1+K2) and T remote one (Fig. 1, the ordinate indicates frequency of PMCs in percentage and the coordinate number or pairing per nucleus. cf. Haga 1937 and Tables 1-2). (2) As a general rule it will be stated that the increase in the degree of genetic differentiation decreases the quantity of pairing proportionally to the grade or quantity of the differentiation. The relative value of the quantity of genetic differentiation will be then expressed by the quantity of pairing which will be adequately given by the following percentage index : 100× (Total number of pairing observed) /n× (Total number of PMCs observed). Theoretically, we can expect all values of the index ranging from 0 to 100. Values of the two modes of pairing. in Trillium Hague were 95.7 for K1-K2 and and 5.6 for (K1+K2) -T, respectively, the former showing the intimate relation and the latter the remote one (Fig. 1, these values are indicated in italics beside the polygons). A more or less continuous variation in this value is evident in a series of diploid hybrids (2n=14) of Aegilops and Triticum (Fig. 2, the ordination and indication of the value are the same as in Figure 1. cf. Table 3). An interesting fact in the present case is that the decrease in quantity of pairing is accompanied by the transposition of the mode of frequency distribution in the direction from the intimate to the remote relation. The most continuous range of variation is obvious in a series of various diploid hybrids (2n=26) in Gossypium. The mean number of bivalents per nucleus shows a complete series from 13 to 2 (v. Skovsted 1937), The pairing relation in the inter- and intra-generic hybrids (2n=14) of Aegilops, Triticum. and Haynaldia is like-wise very suggestive for the present considerations (Fig. 3, only the maximum numbers of bivalents per nucleus are shown after the data compiled by Kihara 1937). (3) The above considerations, will support the inference that : genetic differentiations will express, though superficially, a property of a continuous system. Thus homology is naturally the relation between any two of the genoms differentiated variously in a continuous system. In other words all the relations are included in the term 'homology', which ranges however in quantity of pairing from 0 to 100. Thus it is probable that 'homologous' or 'non-homologous' relation in the cytological sense implys nothing else intonate or remote relation respectively. Theoretically, only the 'identical' relationship-equality in quality, quantity and arrangement of all genes-may be absolute. This consideration naturally leads to the nullification of the critical boundary between auto- and allo-polyploidy. (4) Certain differentiation as a whole of two or more sub-genoms in an allopolyploid would eventually lead to the formation of a new genom, which is no longer indivisible into the ancestral genoms. The new genom is polyploid in chromosome number but functionally diploid.. In the light of the recent knowledge it seems quite probable that the secondary polyploidy is an evolutional product. Then a genom has a potentiality to give rise to a non-pol
(1) In this preliminary note, the author wishes to report an unexpected inheritance in Oryza satira, L. Having in mind the possibility of producing a triploid hybrid, crosses were made between the teraploid strain of rice plant (2n=48) named “TKB” _??_ and the diploid cultivated strain (2n=24) “Taichu 65-Go” _??_. Unexpectedly, all of the F1 hybrids were diploids having the combined characteristics of both parents. (2) The maternal plants, “TKB” are progenies of a tetraploid which has been induced artificially With X-ray radiation by K. Ichijima (1934). Since then, the progenies of this mutant have been cultivated continuously as the stable tetra-ploid strain. (3) In general appearance this tetraploid differed from either its original strain or “Taichu 65-Go”, such characterisitis as rough-arranged panicle, large spikelet and awned glume being, in particular, noticeable. The very low percentage of fertilization (mean, 33.6%) in this plant should be specially mentioned here (Figs. 1, 3 and 4). For the pistillate material, two panicles were chosen from two different tetraploid individuals, i.e. one panicle was used in each plant. (4) “Taichu 65-Go”, or the pollen parent, was known to he a pure cultivated strain. It was clearly different not only from the pistillate parent, above deseribed, but also from the original strain of this tetraploid, in that, the “Taichu 65-Go” has sloping-shouldered and poorly-haired glume, the apicula or which are noticeably colored. (5) In the two crosses, named No. 19 and No. 20, eight and ten spikelets were smeared respectively with pollen of “Taichu 65-Go”. Eleven F1 progenies were obtained in this way from these cross pollinations of these eight plants were obtained to have fully developed. (6) Five of the F1 progenies, i.e. all three from cross No. 19 and two out or the five progenies of cross No. 20, were nearly equal to the pollen parent in general appearance : namely, they have densely-arranged panicles, awnless and smaller spikelets, and deep colored apicula (Figs. 2, 3 and 4). The last characteristic is especially noticeable. It should he further mentioned here, that there is a close resemblance between the diploid hybrid and the pollen parent as regards high percentage of fertilization (mean, 74.2%). On the other hand, the characteristics or these plants were the same as those of the maternal parent, that is to say, the glumes were deeply-haired and broadly-shouldered. (7) The somatic cell divisions at the root tips of these plants were very regular, 24 chromosomes being counted at the metaphase. (8) On the other hand, the remaining three plants in cross No. 20 closely resembled the maternal or the tetraploid parent in general appearance. On examination of the somatic cells at the root tips, all of them were found to be tetraploid (2n=48) as the author had expected. The author considers these tetraploid progenies to have been produced by selling as a result of the failure of pollination. (9) The following three assumptions may be made as a possible explanation of the production of the diploid F1 progenies from the cross of tetraploid _??_×diploid _??_ : (i) Diploid parthenogenetical phenomena may have been due to the stimulation of pollination. (ii) The pistillate plant may be a chimera having diploid and tetraploid shoots, and accidentally the pollination may have been taken place on this diploid shoot. (iii) Elimination !of il. genoin may be carried out during macrogenesis. (10) The first assumption call not suitably explain the author's experimental results, since the diploid hybrids had the characteristics of both parents. (11) According to the results of cross No, 20, the tetraploid progenies were produced by selling, and the diploid ones by crossing on the same panicle. These results can no
Seit 1937 habe ich über die Geschlechtsvererbungsverhältnisse bei Rumex hastatus zyto-genetische Studien ausgeführt. Das Material wurde durch das Entgegenkommen von Herrn Dr. Bhargava in Agra, Indien, zum Geschenk erhalten. Die bisher erlangten Ergebnisse seien hier kurz zusammengestellt. 1. Bei R. hastatus finden sich hinsichtlich des Geschlechtes zweierlei Individuen vor, nauml;mlich rein weibliche und zwittrige. Diese Pflanzen bluhen in Sendai regelmässig zweimal im Jahre, im Frühjahr und im Herbst (Tabelle 1). 2. Fig. 2 stellt die Blütenstände eines Weibchens und eines Zwitters dar. Alle Blüten des Weibchens sind rein weiblich und normal (Fig. 3a). Die Blüten des Zwitters sind alle zwittrig and enthalten sowohl Antheren als auch Karpelle. Die Karpelle der Zwitterblüten weisen aber mehr oder weniger eine verkümmerte Entwicklung auf, dagegen sind die Antheren ganz normal ausgebildet (Fig. 3b-c). 3. Der Ansatz bei den Weibchen ist vollständig, wenn wir mit den Pollen des Zwitters bestäuben. Die Zwitter setzen aber in Sendai bei Freibestäubung keine oder im allgemeinen geringe und schlechte Früchtchen an (Fig. 4). Die Frequenz der Pflanzen mit verschiedenen Ansatzgraden ist in Tabelle 2 zu ersehen. 4. R. hastatus hat 18 diploide Chromosomen. Fig. 5a-c stellen die Kernplatten der weiblichen und der zwittrigen Pflanzen dar. Die Chromosomensatze bestehen aus 4 i- und 14 v-förmige Elementen; aber zwischen den Karyotypen beider Geschlechter können wir einen deutlichen Unterschied nicht bemerken. Bei der Reduktionsteilung in PMZ von Zwitter werden mit Sicherheit 9 Bivalente beobachtet (Fig. 5d-e). 5. Um die Vererbungsverhaltnisse beider Geschlechtstypen von R. hastatus kennen zu lernen, babe ich die Kreuzungen zwischen Weibchen und Zwitter vorgenommen. Von etwa 200 F1-Pflanzen haben bis jetzt 146 geblüht, 78 waren weiblich und 68 zwittrig (Tabelle 4, 5). Das gilt im Zahlenverhaltnis ca. 1 : 1. Also kann man theoretisch annehmen, dass in Bezug auf die Geschlechtsfaktoren eins der Geschlechter hetero- und das andere homogametisch ist. 6. Die Frage, welcher Geschlechtstyp heterogainetisch ist, kann entweder zytologisch oder experimentell gelöst werden. Leider war der zytologische Beweis erfolglos. Darum babe ich anderseits das Selbstbestaubungsexperiment bei einem Zwitter angestellt. Das Resultat ist in Tabelle 6 enthalten. Wie aus dieser Tabelle ersichtlich, können wir in der Nachkommenschaft nicht nur Zwitter, sondern auch Weibchen im Verhältnis 60 : 12 bekommen. Daraus folgt, dass in Bezug auf die Geschlechtsfaktoren der. Zwitter nicht homogametisch, sondern heterogainetisch ist.
This paper deals with the results of investigation on the varietal difference of resistance to brown blight in tea plants, with special reference to significance of the fact upon the tea breeding. After analysis of the leaves of each variety, it was found in general that the leaves of resistant verieties contained more tannin and less nitrogen than those of the susceptible ones, and further that the relative content of tannin and nitrogen compounds in leaves, especially their balance with one another, might he most important in determining the development of the pathogen in the leaf tissues. Such a relationship as relatively high tannin and low nitrogen would bring the resistance to the disease and the reversal the susceptibility. This presumption was proved by the culture of blight fungus (Guignardia Camelliae (Cooke) Butler). Growth of the fungus was inhibited markedly in the culture media made of juice from leaves of the resistant varieties, while good growth was obtained in the culture with juice from susceptible plants; but when the leaf-juice, from which tannin was removed, was used as media the growth of fungus was influenced only by the quantity of nitrogen in leaves. Furthermore, several kinds of chemical substances, added to the Hopkins' culture media, indicated to have various effects upon the growth of fungus; for instance, tannin and caffein act to inhibit the growth and most of the water soluble nitrogen compounds, on the contrary, promote the development of the fungus. It may be probable that the just same phenomena would happen within vital leaves. Caffein is, however, contained in the tea leaves much less than tannin and other nitrogen compounds, so that caffein has little interest upon the fungus development within the tissues of leaves. It may safely concluded that the relative concentration of tannin and nitrogen compounds in tea leaves and their balance with one another play very important roles on the resistance to brown blight disease. We could decide therefore the degree of resistance to the disease with the results of the quantitative analysis of tea leaves in each variety and also estimate contrariwise the relative amount of tannin and nitrogen in tea leaves, judging from the degree of resistance to the disease. The latter relation may be called a “biological method” of determining the tannin and nitrogen content of leaves. Besides both the tannin and nitrogen content of leaves have very intimate relation not only to the resistance to the disease, but also to the tea quality, so the relation found in this experiment can be said to have a great value on the breeding of tea plants. Especially this disease relation will be useful for the discrimination or selection of young plants.