Continued from the previous report(Mizushima and kondo, 1959) results of test crosses between F₃ (Surjamkhi (C^BSp)×Norin No. 1 (C^BSp^a)) and Japanese tester varieties were reported. 24 colorless offsprings, which were originated form the colorless F₂ segregants unexpectedly obtained between colored parents and considered presumably to lack either C or Sp grene locus, were crossed to 3 tester varieties of known genotype in respect to apiculus color (C^BrSp, C^BSp⁺ and C^Bp Sp⁺) and the mode of segregation in 16 of their F₂ strains was investigated (Table 1). C and Sp are the fundamental genes responsible for the production of anthocyanin, the former producing chromogen and the latter turning it into anthocyanin. Theoretical segregation ratios were calculated on the assumption that the position of C-locus of the parental varicties was different either by criptic translocation or by included inversion (recombination value 56%) and that of Sp-locus by included inversion (recom. va., 93%) based on the results already reported (Tables 2, 3 and 4). Comparison of the actual segregntion ratios with the theoretical ones was made (Tables 5 and 6). From the results of the test of goodness of fit of single segregation ratio (Table 5) as well as of their summed one (Table 6), it was confirmed that the parental F₃ plants of the 3 F₂ strains (F₂-4, -5 and -7) contained exclusively the C-locus of Norin N0.1 origin (C_j) that of strain (F₂-6) only the C-locus of Surjamkhi origin (C_i) and those of the 3 strains (F₂-1.-2 and -19) both C_j and C_i, e., duplicated C-loci. From these facts it has been concluded that, as far as the C-locus is concerned. there is structural difference of chromosomew between the Japanese and Indian vareties used. However, the mnechanism which caused the different structural differentiation cannot be determined exactly, because the theoretical segregation ratios calculated on both bases of criptic translocation and included inversion are nearly equal and the actual ratios observed fitted them almost equally.

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1) A detailed description is given in this paper, on the morphological characteristics of polyhaploid plants of S. tuberosuem (variety Deodara) (2n=24), in comparison with those of the maternal plants (2n=48) from which they arose. 2) The polyhaploids differ from Deodara in most of the characters examined, but the degree of difference varies in different characters, indicating that it is low in the qualitative characters related to shape and color and high in the quantitative ones concerned with size, number and weight. 3) It is discussed that this study gives certain suggestions for detecting polyhaploid plants of S. tuberosum from the F₁ populaticns involving this species as one of the parents, and to consider the polyploid nature of S. tuberosum and the morphological relationships of the polyhaploids to wild diploid Solamum species.

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A rice variety widely grown in Taiwan, Taichung No. 65, belonging to the “Horai” or Japonica type and suseptible to the blast desease(caused by Piricularia oryzae), was used for this irradiation experiment. The kinds and dosages of radiation used were gamma-ray (form Co⁶⁰ source, 11 Kr), X-ray (20Kr and 25Kr), and thermal neutron (15hrs. and 20hrs. ). Thc dormant seeds were treated. The process of irradiation was carried out either at the National Institute of Genetics of Japan (Co⁶⁰ treatment) or at the Brookhaven National Laboratory of U.S.A. (the other treatmcnts), through the kindness of the authorities concerncd. The treated plants were grown in Taichung Agricultural Improvement Station for two to four gencrations without artificial selection. 572 lines belonging to the R₅ generation of gamma-ray treatment and bulk populations of thc R₃ generation of the other treatments were tested, together with the non-treated contros, in the experimental field at Tonshu, Taichung Prefecture, Taiwan, where the disease was an epidemic both in the first and second crop seasons. Data were collected on an individual plant basis with a series of index-numbers showing the degree of susceptibility to leaf blast. As shwn in Table 2 and Fig.1, irradiated populations generally showed wider ranges of variation in the susceptibility than controls. The variation. caused by irradiation appeared to be continuous and tended toward high resistaucc. Plants in the control plots were seriously damaged and almost killed by the disease, while a part of plants or lines in the irradiated plots showed resistance and survived. The plants selected from a similar experiment in the first crop season for high resistance were found to be resistant in the second crop scason, indicating that the induced variation was heritable (Table 3). The heritability values in this case were estimated to be 13% to 24%. A resistant line was established from this experiment. Based on these experimental results, suggestions were made that the genetic variation in disease resistance found in ilrradiated plots might be due to induced polygenic mutations, and that irradiation might be useful tool for an improvement of blast disease resistance in rice.

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Two kinds of genotype-environment interactions were estimatecl in Barred Plymouth Rocks. Variances attributable to sire family-location interaction were of no importance either for egg production or days to sexual maturity. On the other hand, comparison of sire families under different hatching periods supports the contention that the genotype for hen-housed egg production within one hatching period can not be identified with that within another. Statistical analysis showed that the variance due to interaction was highly significant for egg production, while it was not significant for sexual maturity. Implications of this phenomenon and discussions with regard to current poultry breeding techniques are also presented.

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[in Japanese]

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A hybrid population between a Japanese rice "No-rin 36" and a chinese rice "Reishiko" was treated by each of the 3 systems of breeding method, pedigree, mass-selection and bulk. In pecligree system 5, 000 plants were grown and 248 individuals were selected from F₂ population. Selection and pedlgree culture were repeated in eclch generation from F₂ to F₆ as in ordinary way. In mass-selection system, also, 5, 000 plants were grown for individual selection in F₂ and their seeds were mixed in groups. Individual selection and bulk of seeds were repeated in each follwing generation untill the F₆. Populations in bulk system were raised in 3 Iocations from F₂ to F₆ where the climatic and biological environmental conditions were different. The number of plants used in bulk system were 1, 500 in F₂ and 5000 in each following generation at each location. In F₆, individual selection was done in each location. In F₇ and F₈ generation, the performance test was conducted for all selected lines from each 3 systems of breeding method to compare the effectiveness of selection between these systcms. The results show that the pedigree system had more ones with high yield, strong culm or early maturity as compared to the bulk system. The inferiority of the bulk system in the effectiveness of selection may mainly due to: ( 1 )the weakness of individuals with good characters in the compctition of bulk population, ( 2 ) the shortage of number of individuals in F₆ generation and that of lines in F₇ used in bulk system and ( 3 ) the effectiveness of individual selection for the grain-weight paralleled with plant-type in F₂ of the pedigree system. By the mass-selection system, on the other hand, there were many heterozygous lines in F₇ though they were good in growth and yield. They indicated that the individual selection in heterozygous hybrid population had a high possibility to select heterozygous plants with heterosis and it was difficult to fix them in homozygous conditicn without pcdigree culture. The results also revealed that : ( 1 ) the parentoffspring correlation coefficients between individual and line (F₂-F₃, F₅-F₆), and that between line to line (F₃-F₄, F₆-F₇) calculated in the pedigree system were large for heading-time, culm-length, spikelength, quality of brown rice and disease resistance and small for grain-weight and number of spikes, ( 2 ) the natural selection for the agronomical characters, especially for heading-time and disease resistance, in bulk populations was different for the environ mental conditions of locations where the hybrid population were grown. From the result, it was recognized that environmental conditions of breeding station had significant effects on the effeciency of selection in breeding work, espccially in the bulk system.

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Water requirement and water economy of varieties were studied accurately by water culture, in the years 1955 and 1956.The resutts of these experiments are summarized below : - 1. The total amount of water absorbed by each of the 9 varietieS was determined at different growing stages. There was a considerable annual variation in water absorption among the varieties tested between 1955 and 1956. 2. The water economy of each variety was calculated, by diviving the total amount of water absorbed by the amount of dry weight procluced. The order of varieties determined by the value of water economy did not coinside with that of calculated by the total amount of water absorbed. 3. As a whole these oat varineties may be classified Into several groups in accordance with the values of their water economy. By using Trukey's procedure, the varieties were statistically classified into four groups according to their respective water economies. The first group is higher in water economy, including two vanetres and the fourth group lower, inclucllng a single vanety 4. Correlation coefflcients between the total amounts of water absorbed and some characteristics, were calculated. Correlation coefficients between total amnount of water absorbed and forms of juvenile plant growth habits are significant. Number of tillers is positively correlated with water requirement, though it was not statistically significant. Thus it may be concluded that the varieties with more tillers and of prostrate type tend to absorb more water than those with fewer tillers ancl of erect type.

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A number of lines homozygTous for reciprocal translocations were selected from the progeny of X-rayed plants of two rice varieties, Peiku (108) and Kisshin (521) as reported by the writer (CHANG 1955). Seme of them were crossed with glutinous rice varieties with different combinations of the genes for apiculus coloration (C and Sp). to investigate the linkage relation of translcations to these genes. The relation between F₂ segregation and fertility was examined. As the results, it was found that in one of 9 strains of Peiku, and in two of 5 strains of Kisshin, the translocations might, be linked with the glutinous gene, g1. The recombination values between the interchange points and the glutinous gene were estimated to be 25% to 38%. Coloration at the apiculus did not show a significant relation with thosc translocations. The variations in heading date and plant height were compared between fertile and semi-sterile classes of F₂ plants to see if genes for these quantitative characters are involved in the translocations under observation. In one strain of Peiku, a gene or genes controlling headingr date appeared to be linked with the translocation carried by the strain. In the other strain of Peiku and a strain of Kisshin, genes controlling plant height appeared to be linked with the translocation.

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The effects of nitrogen, phosphorus and potassium on the panicle diffcrcntiatlon and the time of heading were investigated cyto-histologically, using "Aichi Asahi" a variety. of paddy rlce. The sand culture was carried out, using the Dr. KASUGAI's complete culture solution for rice plants as the standard solution, and following seven plots were provided, i. e. l. 4NPK, 2. N4PK, 3. NP4K, 4. PK, 5. NK, 6. NP and 7. NPK, the control. The results obtained in the experiment are as follows. ( 1 ) The different conditions of mineral nutritions have some effects upon the form and structure of vegetative shoot apices, and among others, the effects of nitrogen and phosphorus form a strong contrast. Though nitrogen has a tendency to increase the number of tunica layers, but on the contrary, phosphorus tends to inhibit the stratification in the tunica, and high nitrogen supply makes the apex rather a flat dome, a typical form of the vegetative phase, and high phosphorus supply makes it a long and somewhat of cylindrical form. ( 2 ) Nitrogen and phosphrous have also opposlte effects on the leaf inception. Whereas high nitrogen supply hastens a plastochrone and increases the number of leaves, high phosphorus supply not only tends to delay a plastochrne but also decrcase the number of leaves. ( 3 ) The period of panicle diffcrentiation is influenced by the dirferent conditions of mineral nutrition, and it is the earliest in the plot of high phosphorus supply and the latest in that of high nitrogen supply. The time of heading also shows the same tendency as that of panicle differentiation. ( 4 ) Considering the histological changes of shoot apex in the transition stage from the vegetative to reproductive phase, high nitrogen supply seems to strengthen the vegetative growth and delay the transition to the reproductive phase and on the contrary high phosphorus supply seems to diminish vcgctative growth and induce the reproductivc phase. ( 5 ) As regards the potassium, its effect is not so clear as that of nitrogen or phosphorus, but generally spcaking, it is rather slmilar to that of nitrogen.

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This paper deals with the results of various competition experiments with rice. The results are summarized below:- 1. Varieties of the Indica or the Continental type generally have higher competitive abilities than those of the Japonica or the Insular type. 2. Among lines derived from hybrids between distantly related varieties, those from bulk propagation of hybrid populations tenaed to have a higher competitive ability than those from pedigree propagation. This indicates that genotypes with high competitive ability increase in hybrid populations. 3. Among hybrid-derived lines, the competitive ability shoeed no significant correlation with various agronomic characters. However, the characters differentiating the Indica and Japonica types were found to be correlated with competitive ability in the way that lines resembling in a character the Indica type tended to have a higher competitive ability than those resembling the Japonica type. This may be explamed by the tendency generally recognizable toward restriction of character recombination in hybrids between distantly related rice varieties. 4. The inheritance of competitive ability in an intervarietal cross was investigated by using Mather's method of partitionin variance components. The results indicate that competitive ability might be controlled by Mendelian genes. 5. An Indica and a Japonica variety were mix-propagated for three generations under different growing conditions. It was found that the competitive ability of one a variety to the other might become higher under conditions rather unfavorable to it. 6. Varieties of the Indica or Continental type showed higher competitive ability or resistance against weeds than those of the Japonica or Insular type.

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