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An anomalous mode of segregation in respect to apiculus anthocyanin pigmentation observed in a fertile hybrid between a Japancse (Norin No. 1)and an Indian rice variety (Surjamkhi) was described. The apiculus color of Norin No. 1 is red and that of Surjamkhi is dark purple, whose genotypes havebeen determined as C^B Sp^a A and C^B SpA respectively after the gene symbols designated by NAGAO and TAKAIIASHI. C is a gene responsible for the production of chromogen and Sp, acting complementarily, turns it into anthocyanin. Both C and Sp form a mnultiple allelic scries, C^Bt>C^Br>C⁺ and Sp>Sp^dSp⁺. F₁ hybrid between them shows dark purple apiculus color. Its seedbearing fertility is nearly perfect (96%), though it shows a certain degree of pollen abortion (14%). In F₂ it segregated individuals with colorless apiculus which came up to about 30 per cent of the total, instead of showing the expected segregation ratio of 3 dark purple : I red, i.e., 3 Sp : 1Sp^d, accompanying remarkable decrease of individuals with red apiculus color (Table 2). A large part of the colorless plants showed tawny coloration in their apiculus at ripening, showing the effect of C^B observed when Sp or Sp^d is absent. The apiculus color at ripening of the remaining colorless plants was straw white, showing on effect of C^B. Segrefation of partial sterility also occurred in F₂ as shown in Table 3, in which one can detect no clear relation between the partial sterility and the types of apiculus coloration. The similar distribution of partial sterility in each of the classes is taken to show that the gametes of f₁ bearing noncoloredness were equally functional as those bearing coloredness in bringing forth the F₂ progeny. The mode of segregation of apiculus color observed in 83 F₃ strains originated from randomly taken F₂ plants, including 48 colored and 34. colorless ones, was various (Table 4 and 5 ). Some strains showed mono- and dihybrid segregation ratios, but others did rather complex ratios which could not tion between the partial sterility and the apiculus color was observed. Discussion was madd as to the mechanism which resulted in the segregation of individuals with colorless apiculus in F₂. Since the frequency of the appearance of colorless plants in F₂ was remarkably high, the mechanism due to autonomous mutations, C^B→C⁺, and Sp^d→Sp⁺, was concluded to be out of qucstion. It was suggested that the anomalous segregatisn might bc due to minor structural differences of chromosomes between the parental varieties which did not affect directly the parental varieties which did not affect directly the viability of gametes produced of F₁ hybrid. Though there were found some F₃ plants which seemed to be deficient in the gene loci in question by crossing them with tester varieties of known genotype, the authors could not attain to a definite conclusion as to the mechanism under issue.

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The authors intended to examine how the environmental factors affect the seed developmcnt of soybean, and more-over how the influence varv according to varietal diffcrences. Soy-bean varieties used were Kizaya(IIa), Norin No. 2(IIb) and lwate No. 2 (IIc). In natural condition, the ripening period of Kizaya, Norin No. 2 and lwate No. 2 was 48, 66 and 87 days, respectively. By the microscopic observation, it was ascertained that the speed of embryo development was slower in the order of Kizaya, Norin No. 2 and Iwate No. 2. For example, the date of cotyledon emergence was about the 10 th, 15th and 25th day from blooming, respcctively. Under short-day condition, the ripening period was shortened and the degree of shortening was larger in the order of Kizaya, Norin No. 2 and Iwate No. 2. From the the microscopic observation, it was found that there were two stages which were easily affected by short-day condition. The first one was the early period of ripening or the early stage of embryo development, that is from proembryo developmental stage II to first simple leaf deveiopmental stage III, and the second one was the late period of ripening from sccd-length maximum to wholly ripening. in which stock nourishment accumulated in cotyledon. High temperature also hastened seed ripening but the effect of temperature was less than short-day. The elongation of seed- and pod-length was also accelerated by short-day and high temperature, and as a whole, the degree of acceleration was larger in the order of Kizaya, Norin No. 9 and Iwate No. 2.

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1. Following the previous report (KAWASE and MURATA 1958), five experiments were conducted as a part of the series of fundamental researches on the relationship between day-length and the action of genes E₃, E₄ and E₅ controlling heading date with the aim of obtaining some information on rice breeding. 2. Seven strains which possess E₃, E₄ and E5 in different combinations homozygously (Table 1. ) were maintained under various photoperiodical treatments and the variation in heading date and ear primordium differentiation were observed. 3. The findings concerning the function of genes E₃, E₄ and E₅ for the response to day-length treatments are nearly the same as those obtained with the genes E₁ and E₂ (KAWASE and MURATA 1958) and summarized as follows : The period necessary for acquiring short-day sensitivity are nealy the same for all strains (35-40 days after sowing), and thus the genes E₃, E₄ and E₅ have little cefect on this period. In the sensitivity to the 12-13 day-length treatment after acquiring short day sensitivlty, there were no differences among the seven strains. But genotypic differences come out distinctly under the 14-16 day-length treatment. The effect of gene E₄ on the response to day-length treatment is larger than those of gene E₃ and E₅. This relationship between the effects is unchangeable in all four plant ages examined. Under the common environment of rice culture where the photoperiod decreases gradually, the time of ear primordium differentiation is determined mainly by the genotypically specific "critical-day-length". The effect of gene E₄ on the shortening of the critical-day-length is larger than those of genes E₃ and E₅. The heading clate is ddlayed when the dominant alles of E₃, E₄ zind E₅ are included and the day-length is longer. It is physiologically due to the increase in the nulnbers of days from photoperiod treatment to differentiation of ear primordium and from this time to heading. Furthermore, the effect of short-day treatment on ear emergcnce is lesser in the young plant than the old. From these findings and the fact that the genes E₃, E₄ and E₅ giv'e some influence on plant height, it was supposed that these genes are controlling the synthesis or metabolism of auxins in plant in some way.

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[in Japanese]

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[in Japanese]

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