The extensive experiment on rice responses to its environmental conditions has been studied at a great number of agricultural experimental stations throu-ghout Japan since 1948. The analysis of these data gives many useful informations to both rice breeders and research workers on rice. This report is a part of this kind of analysis, especially from the standpoint of rice breeder. The analysis of variance on data which are derived from experiments in Tohoku, Hokuriku and Kanto districts shows us following interesting informations.

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The methods of mutation breeding were applied on six rowved barly in three ways. The dormant seeds were treated with 15 Kr of X-rays. Method A : After 3 ears were havested from each X₁ Plant and one grain was removed from each ear, these grains were planted in bulk at X₂ Mlethod B : After one ear was harvested from each X_l plant, the grains were planted separately as ear progenies at X₂Method C : After 3 ears were harvested from each Xi Plant, the grains were planted separately as plant progenies at X₂ Method A was compared with B and C. The eharacters mainly analyzed were earliness and stems;shortness. The selection of such aberrants was carried out in X₂ (Table 1), and these were confirmed as mutants in X₃ (Tables 2 and 3) . In the case of method A-ll (Table 1), selection was made by measuring stem length at X₂ generation. In the case of other methods, selection was made by observation. 1) By using method A, the mutant types found n X₂ Were more frequently observed compared with the other two methods and the mutant much deviated from the parent type were involved.This result was compatible with the theoretical consideration of YOSHIDA (1962). 2) Much better selection of short stem mutants was made in X₂ by method A (I+II) than by methods B and C. This result demonstrates that the individual selection using this measurement was made much better than the pedigree selectian through observation.

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Eight test varieties were chosen and were crossed with each of 47 varities (30 upland rice and 4 'red rice' from Japan and 13 Eastern Asian countries) to examine mutual sexual affinity among rice varieties. The sexual aflimity was measured by the percentage of viable pollen in F₁ hybrids. The results are summarized as follows : 1. No difference was found between reciprocal crosses (Fig. 1). 2. The pollen fertility of the F₁ hybrids was different with the combination of parental varieties and ranged discontinuously from about 100% to O% (Table 2) . 3. It seemed that F₂ variation for intervarietal hrybrid sterility was discontinuous and that the modes observed in F₂ variation were coincident with those in intervarietal combinations (Table 3). The intervarietal hybrid sterility could be accounted for by duplicated genes (Table 4) . 4. From the observation of anomalous segrega-tions for anthocyanin pigmentation and glutinuous character, it. was assumed that the duplicated genes belonged frequently to "wx"-group (Table 6) . 5. By separating the varieties with similar affmity to each of the test varieties, Japanese upland rice was divisible in to three groups. Group I, to which most varieties belonged, was again classified into two types, corresponding to 'Lowland Type' and 'Upland Type' respectively (Fig. 2).

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The present paper deals with observations on the seedling mutations, which appeared in Rˆ1₃. of r-ray on dormant seeds of a veLrlety "Kogen Mugl" of slx rowed barley 21% (35 strains) of Rˆ1₄ ' Rˆ2₂_3- and Rˆ2₃_4-strains after doses of 30, OOOr chlorophyll mutated strains were found out, in a total (164 mutated strains), indicating abnormal ratios of segregation. Such abnormalities may be caused by chromosomal changes, especially chromo-somal deficiency. This fact is of great importance in relation to the method of finding mutated strains and that of treating mutated ones which indicate abnormal ratios of segregation (Table 1). The kinds and frequencies of chlorophyll mutations vary with environmental conditions such as temperature and light resulting from differences in seeding seasons and fields. This fact is of important in relation to find out mutant characters, especially physiological ones (Table 5). As to the induction of mutants, repeated irradia-tion for two successive generatibns is more efficient than that for one generattion only, since mutation breeding should be based on the higfhest mutation rate possible. In mutation breeding, the ears exhi-biting' best fertility among all the plants as well as ears of the same plant should be selected to increase muta tion rate (Tables 3-4). The various categorories of chlorophyll mutants were obtairned in the sarne relative frequencies as observed by earlier workers (Table 2) . Seedling mutatior that difEered from chlorophyll mutations were also found. Thee seemed to be caused by chromosomal changes (Table 6) .

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For the purpose of obtaining inbred lines of sugar beet for F₁ hybrid production, the authors studied selfing from la.52 to 1954. Self-fertilization of sugar beet is ordinarily very rare since sugar beet is self-sterile. In oLlr experiments, however, successful set resulted from crosses between two clonal parts of a longitudinally divided beet root. At the early bolting stage, one part was treated with leaf clip-ping or with covering by black cotton cloth and a marsh reed curtain, and the other part lvas not treated. The highest seed setting rate was observed under short day (15.6% for the all treated flowers) and seed set was always higher in the SD treated parts. Noticeable differences were seen in the oxidation-reduction potential of treated and untreated parts of the same root of male (anther) and female (ovary) flowers. Differences in nutrient status (N, P, K) determined by petiole test in fresh plants were also observed. From the experimental results the conclusion was drawn that this method might prove useful for obtaining inbred lines successfully.

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[in Japanese]

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Anthocyanin coloration in stigma and stem internode of the rice plant was considered by Nagao (1951) to be due to the two basic genes responsible for the production of the pigment, C and A. Takahashi (1958) has, however, confirmed in variety that coloration in stigma i-s controlled by a gene, Ps, Ivhich distributes the piglnent produced by C and A to the site. Although he had found the Ps-gene, he stated that sometimes stigma coloration could occur without its presence. If the genotype for the basic gene is either C^BA or C^BpA in the presence of the dominant P-gene, colored stigma is dis played. The results of the present experiment has, however, shown that Ps is indispensable for colored stigma and another gene, Pin, for colored stem internode. It has also been proved that even a weak basic gene constitution, C^BrA, presents colored stigma in the presence of Ps, which is determined as colorless by Takahashi (1958) .

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ldentification of the genotypes with respect to anthocyanin coloration of eight rice varieties of Japanese and Indian origin which had been determined beforehand by the phenotypes of F₁ hybrids obtained in the testcrosses between them and thirteen tester varieties of known genotype (Kondo, 1963) was made by examining the mode of segregation in their F₂ populations. Twenty-three F₂ Strains each including 130-300individuals were investigated. The varieties which were used as parents in the crosses are listed in Table 1. From the patterns of segregation shown in Tables 2, 3, 4 and 5 it has been proved that the genotype of each variety determined previously by the F₁ phenotypes is valid.

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Following the previous papers (SYAKUDO, K.and KAWABATA, S. 1961 and 1962a), it is the chief purpose of this paper to report the underlyinginformation on the utilization of hybrid vigor in Renge breeding. Results obtained are summarized as follows 1) A considerable variation is found in forage yields of 28 F₁ hybrids of all possible combinations among 8 inbred lines, ranging from 289. 2g to 488.5g in average yields per plant and from 163.8g to 368.9g in F₁ ?? P (MP : Mid-parent). As previously noted, this fact suggests that it is important to select inbred lines showing high combining ability. Decline of fcrage yields due to inbreeding is, on the average, recovered in the F₁ plants among inbred lines. Accordingly, the F₁ hybrid having significantly higher yields than the mean yield of F₁ Iines tested seems to produce superior yields to an original open-pollinated variety. 2) A positive high correlation is found in forage yields between open-pollinated and diallel crossed progenies. It indicates that general combining, ability may be evaluated by open-pollinated D. roge-lries, too. 3) Genic male sterility and incompatibility do not occur in Renge. Therefore, the breeder can not produce hybrid seeds by utilizing therse phenomena. As this legume is highl cross-pollinated, the breeder can, however, easily produce hybrid seeds by means of a mixed planting of some inbred lines, permitting mixing of some selfed or sibbed seeds into hybrid seeds. By this method the authors, obtained hybrid seeds and then compared the performance of these hybrid seeds with that of the leading commercial variety, Gifu-Daibansei. As a result of this test, significantly b.igher yielding hybrids than Gifu-Daibansei were found with rela-tively high frequency. 4) According to this method for producing hybrid seeds, a certain percentage of self.ed or sibbed seed from the parent plants is carried into the hybrid seed. Consequently, the competition between hybrid and parent plants comes into question as a factor in determining the yields. To study this problem, mixtures of parent and hybrid Renge seeds, together with pure seeds of the parents and hybrids, were planted at three different seeding rates. The forage production of the 80% hybrid mixture planted in the congested condition, does not differ significantly from that of the pure hybrid. These results suggest that any seed mixtures may be expected to yield about as much as pure hybrid seeds do. 5) From these findings, it is concluded that the utilization of hybrid vigor is very promising for Renge breeding.

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Radiation injuries caused bv acute irradiation were studied in potted rice plants (varie.ty Gimbozu) exposed to X-rays (doses: 0.5-30 kr, dose rates: 12-llO r/min.) at several stages of plant development from about five weeks to a few days before heading. The experiments were conducted in 1960, 1961, and 1962, and three experimental sections different in the method of plant culture were prepared in 1961. As similar results were obtained in each year and among three sections in 1961, those from a section in 1961 are mainiy reported here, in which the heading date (usually Sept, 1) was delayed about ten days by long-day treatment. For the long-day treatment section in 1961, X-ray irradiation was administered on five different dates from Aug. Il to Sept.8 with one week interval. The irradiated groups were designated as I to V in the order of the irradiation date. Developmental stages of panicles of main tiller in each group at the irradiatior; were estimated as follows: I, panicle not yet differentiated; II, differentiating stage of first bract prillrlordium; III, differentlating stage of secondary branch primordia to beginning stage of flower primordia differentiation; IV, Iate differentiating stage of flower primordia to differentiating stage of PMC; and V, extine formation stage to ripe stage of pollen. After irradiation, various injuries lvere found on the irradiated plants according to the dose of X-rays and the developmental stage at the irradiation. (1) The occurrence and degree of injury varies with the developmental stage as well as with the character observed. In the above experimental section, the highest radiation sensitivity was observed in the irradiated groups II and III for heading behavior, in I for plant height, in 11 for cuhrl length, in I-III fcr number of florets per panicle, in IV for seed fertility, in 111 and IV for shape of panicle, and in 111 for shape of floret. (2) The degree of injury in each character increases linearly with the dose of X-rays in all the irradiated groups. The dose that brings about easily detectable injuries in the above characters is generally more than 5 kr. The experimental results suggest that the seed sterility may be caused not only by chromosomal aberrations but even more frequently by extrachromosomal or physiological effects of radiation. The malformed floret with degenerate inner glume can be easily induced only at the beginning stage of flower primordia differentiation of a panicle, indicating that the primordium of inner glume may have a marked sensitivity to radiation. These results suggest that acute irradiation may be effectively utilized for histological analysis of plants and also for tracing induced mutations.

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In thc previous paper of this series (Yamagata and Syakudo 1963b), it was reported that radiation injuries observed on the X-irradiated plants varied with the dose of X-rays and the developmental stage of plants at the irradiation. In the present study, the progeny (X₂) of the irradiated plants was examined to obtain information on effective incduction of mutations. The seeds obtained from the long-day treatment section in 1961 were mainly used. The X₁ panicles of each irradiated group ( I to V) were further classifred into "developmental-stage groups" based on the nunrber of days required for heading after irradiation. ( 1 ) The decrease of sprouting ability of X₂ seeds obtained from X₁ panicles irradiated with high doses (more than 10kr) of X-rays at postmeiotic stages was gleatel than at premeiotic stages. Almost no sprouting was observed in the seeds from X₁ panicles irradiated with 20kr after meiosis. It was revealed however, that low-dose (1kr) irradiation at some stages before meiosis caused remarkabiy low sprouting abilities. ( 2 ) In the X₂ generation, there were observed chlorophyll mutant seedlings such as albina, xan-tha, and viridis ; partially or complctely sterile plants ; early or late maturing plants ; tall or dwarf plants ; and plants with slender or round glumes, etc. i ) The frecluencies of the above mentioned aberrants tended to increase linearly with the dose of X-rays irrespective of irradiated stages. ii ) The frequencies of sterile X₂ plants were ten times higher in the X₁ panicles irradiated after meiosis than in those irradiated before meiosis. Unexpectedly, the frequencies of chlorophyll mutants and other aberrants did not vary with the developmental stages of X₁ panicles at the irradiation. iii) No specific relations were found between the aberration spectrum in X₂ and the developmental stage of X₁ panicle at the irradiation or the kind of X₁ injury. The possible cause of anomalous sprouting due to low-dose irradiation has been discussed, and the frequency and spectrum of induced aberrations examined from the viewpoint of plant breeding.

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The fruit productivity of the eggplant hybrids was analysed in relation to their vegetative growth. Six commercial varieties which differcd in maturity, fruit and other charactcrs (Table 1) were diallelcrossed without reciprocals. An F₂ population was examined in the combination of thc early variety "Minden" with the late variety "Kurumenagn". All the F₁ hybrids except one showed heterosis for fruit yield(Table 2). The average fruit weight, one component of fruit yield, was larger in the F₁ mean than in the parent mean (Table 3), although fruits were hanvested in nearly same size. This may be attributed to the fruit growth rate of F₁ hybrids surpcrior to that of parents during the succesive harvest of two or three days interval. The number of fruits, the other component of fruit yield, also gencrally showed heterosis (Table 4). For the purpose of examining the relation of fruit yield to vegetative growth, the fruit yield of each variety and F₁ was plotted against thc weight of vegetative part shown in Table 5. It was ascertained from Fig.1 that thc varieties and thc F₁ hybrids fall into two fairly distinct groups ; one of those includes all six members of the constant parent array of "Minden", so that it may be called"Mindengroup"and the other is "general group" of all other varieties and F₁ hybrids.

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