The purpose of this study was to enhance the reproducibility of plating efficiency in leaf protoplasts of Lycopersicon peruvianum and determine the optimum concentration of plant hormones for shoot formation from calluses derived from protoplasts. Cell division was constantly induced in leaf protoplasts isolated from the plants grown at a low temperature (20°C) and under an illumination of 2, 500lux (16hr day length), in addition to high humidity conditions and moderate supply of nutrients. Plating efficiency was largely influenced by the leaf age, type of plant hormones, composition of medium and plants for protoplast culture. It is suggested that the effectiveness of medium for protoplast culture depends on endogenous conditions of the plant before the isolation of protoplasts. The optimum concentration of indoleacetic acid (IAA) and benzyladenine (BA) in MS medium (MURASHIGE and SKOOG, 1962) for shoot formation from calluses derived from protoplasts was found to be about 2.0 mg/l BA with or without the addition of a small amount of IAA. Calluses with a shorter period of culture were suitable for achieving a higher rate of normal shoot formation with abundant shoots per callus.

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A method was developed for protoplast isolation and culture from subcultures of apple (Malus pumila MILL. var. domestica SCHNEID.) calluses induced originally by anther culture. Viable protoplasts were obtained by using an enzyme solution containing 2% cellulase "Onozuka" R-10, 0.1% pectolyase Y-23 and 0.7M mannitol (pH5.8) and the optimum incubation time was 2.5hr. Protoplasts thus obtained were cultured in a modified 8p medium containing benzyladenine (BA) instead of zeatin without the use of coconut water. Within 1 week of culture, the protoplasts initiated cell division and the addition of fresh medium induced a marked increase in the number of cell colonies. The optimum plating density was 1-2xl05 protoplasts/ml and higher densities of protoplasts tended to inhibit colony formation. The induced colonies were transferred onto media solidified with agar. The colonies then formed calluses during 1 month, but no shoot or root was formed.

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In the case of irradiation of seeds of self-pollinated and disomic plant materials, the frequency of mutated plants appearing in the M₂ generation divided by the Mendelian ratio is an index, as proposed by Gaul (1960), that enables the direct estimation of the mutation rate, representing the ratio of the number of mutated cells to the number of survived cells after treatment of mutagen. In the case of chronic irradiation of growing plants throughout the entire life cycle from germination to maturity, on the other hand, the mutations induced at the stage preceding the differentiation of the male and female organs appear at the M₂ generation, the but mutations induced after this critical time are observed in the M₂ plants in the heterozygous condition and are detected only at the M₃ generation. Therefore, the mutation rate can not be correctly estimated only on the basis of the frequency of mutants either in the M₂ or M₃ generation. A new method for the estimation of the mutation rate by combining the data of the frequency of mutants and the M₂ and M₃ generation, which is comparable to Gaul's method for seed irradiation, is proposed. Application of this method to the data of acute and chronic gamma-ray irradiation of growing barley revealed that a much higher mutation rate was observed after irradiation at a higher daily exposure rate, when the plants were treated with the same accumulated dose.

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The present study was undertaken to investigate the starch properties and inheritance of a newly induced mutant of rice. The endosperm of the mutant is dull and can be readily distinguished from the waxy as well as nonwaxy endosperms. The amylose content of the dull mutant was half as low as that of the nonwaxy counterpart. No conspicuous differences regarding the distribution of unit chain length of amylopectin existed between dull mutant and the normal counterpart. The starch properties of the dull mutant were determined three weeks after heading. Judging from the genetical analysis for amylose content of the dull mutant, it was considered that amylose production in the dull mutant is controlled by a single recessive gene which is nonallelic to the wx alleles. The amylose content did not decreased proportionally with the number of du alleles, in contrast to the proportional reduction in amylose content with the number of wx alleles. The existence of a low amylose mutant gene makes it possible to improve the eating quality of rice grains.

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Sixteen soybean varieties were sown on 8 different sowing times from Sept. 30 to Feb.5 through 1981 to 1982 in the field of Regional Center of Agricultural Research. Paraguay. The mean day length during the period from sowing to flowering was the longest when the plants were sown in Nov. The largest number of stem nodes was realized also by sowing in Nov. The increasing rates of the node number owing to the photoperiod were estimated by means of the exponential regression to compare the varietal difference in the photosensitivity for flowering. Two varieties which were adaptable to early sowing exhibited the lower photosensitivity than the others. The later was the sowing time, the shorter became the period from flowering to maturity due to decrease of the mean day length during maturation. The limits of optimum photoperiod for maturation as well as the retardation rates of maturation with excessive photoperiod were estimated for each of the varieties by means of the linear regression. A tendency was observed that later varieties had longer limit of the optimum photoperiod and higher rate of the retardation of maturation with the excessive photoperiod. When the plants were sown early, the pod setting of late varieties was delayed probably due to long photoperiod at the time of flowering.

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Seedlings of six rice cultivars, IR 8 and Taichung Native 1 (indlca), Yukara (japonica), and Yushin Milyang 21 and Milyang 23 (indica×japonica lines) were grown with an adequate supply of nutrients and water in a natural light chamber with a day/night temperature of 23/18°C for 28 to 33 days, then the seedlings were grown in a 17/22°C chamber (Low Temperature Treatment, LT) or in a 30/25°C chamber (High Temperature Treatment, HT). The photosynthetic rate, leaf area and the contents of water, dry matter, chlorophyll, nitrogen, total soluble sugars and starch of the second expanded leaves from the top were measured after three and seven days of LT and after three days of HT.

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Factors contributing to lodging resistance i.e. culm stiffness and the related characters were examined by field experiments of 26 rice cultivars. Cultivars Koshihikari and Sasanishiki, which are known to have a taste quality, showed early start of and heavy degree of lodging at low as well as heavy fertilizer levels (Table 1, Fig.1). Semi-dwarf rice cultivars IR 8, IR 127 and IR 269 showed no sign of loding even at the high fertilizer livels. Fujiminori and Inabawase were found to have an intermediate lodging resistance, but the response to fertilizer levels and the time of start of loging differed with each other (Tables 2 and 3). Fujiminori lodged even at the low fertilizer levels, but showed no conspicuous increase in the degree of lodging at the high levels. Inabawase, on the contrary, lodged heavily at the high levels inspite of no lodging at the low levels. Start of lodging was earlier in Fujiminori than in Inabawase. The degree of lodging did not increase until maturity in the former, while abrupt lodging just before maturity was recognized for the latter. Culm type index and culm moment was defined by d/l and (d2/l)2, respectively, where d is external diameter of basal culm and l culm length. Culm length, culm moment and, particularly, culm type index showed a high correlation with degree of lodging at both and high fertilizer levels (Tables 4 and 5).

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A critierion for evaluating the practical merit of intermating before selection was defined based on the probability that desirable genotypes are obtained with a given amount of breeding cost. Some general trends about the efficiency of intermating were derived from numerical computations. A special consideration was made on the effects of some non-additive gene actions which have been little investigated in the past studies. Intermating in segregating populations is not always useful for increasing genetic variance, although effective in promoting gene recombination. Selfed or partially intermated populations have in many cases larger genetic variance than intermated populations. In the presence of non-additive gene effects, selfing causes a larger change in population mean than intermating. Intermating can be very efficiently applied to break undersirable tight linkages. The efficiency is especially large in the presence of duplicate epistatic interaction, there being little difference among the cases of additive, dominance, and complementary eplstatic interaction. Intermating seems to be more effective in less heritable characters.

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The phenotypic expression for a quantitative character of a genotype grown in an environment can be evaluated by two different statistics, namely, mean value and variation of individual plants. The former is a measure of the magitude or the performance of the character and the latter is a measure of the inter-plant variation. As well as the performance itself the inter-plant variation is the important property in breeding programs, for example mechanization in agriculture or the quality of harvested crops. The purpose of the present paper is to investigate the relationships between the plant height of a genotype and its inter-plant variation by growing 12 inbred lines of rustica tobacco (Nicotiana rustica L.) under 14 different environmental conditions which were combined by years, transplanting dates (seeding dates) and plant densities (Table 1). The inter-plant variation was measured by the square root of standard deviation of ten plants with the same genotype within a plot.

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Rice breeding for true resistance to blast disease caused by Pyricuralia oryzae Cavara, should be based on the correct knowledge of true resistance genotypes of parental varieties used for crossings, in order to utilize new true resistance gene (s) from introduced varieties. A rapid method of estimating the true resistance genotypes of rice varieties was developed in Japan by using specific reaction patterns of varieties against several fungus races. The method is, however, inapplicable to introduced varietles having unknown true resistance gene(s). The conventional method of gene analysis using F₂ and F₃ generations requires laborious works to estimate the true resistance genotypes in those introduced varietles.

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Using microspectrophotometer, light absorption of colored vacuole and plastid was examined on intact cells of twenty plant species containing various kinds of pigments. Based on their spectral curves, colored cells were classified into six groups according to the type of curves, the location of absorption maxima and number of peaks. Some characteristic features were observed between major pigments and the groupings divided by intact spectra, as follows: In group I, no absorption peak in the visible region (Fig.1 a) as seen on vacuoles of all white flowers (cacti), yellow flowers (dahlia) and dark brown eye in petals (broad bean), showing the presence of flavonols, chalcones plus aurones, and melanins, respectively. In group II, one spectral peak appearing on vacuoles of red and red-purple organs in the region, 534-552 nm (Fig.1 b), which were due to anthocyanins (stock flower, etc.) or betacyanins (common four o'clock flower, etc.). In group III, two peaks on the vacuoles of yellow, orange or red organs (Fig.1 c), in which betaxanthins alone (flowers of common portulaca etc.) or both betacyanins and betaxanthins (flowers of cacti) are contained. In group IV, three or more spectral peaks appeared on the vacuoles of blue day-flower petals (Commelina communis L.) and orange tritonia flowers (Tritonia crocosmaeflora Lemoine) (Fig.1 d). The former blue is due to the metal or co-pigment complex of anthocyanin, while the latter to both water-soluble carotenoid and anthocyanin. In group V, two or more peaks appeared on the plastids of yellow, red or green organs (Fig.1 e), showing the presence of carotenoids (red pepper fruit) or chlorophylls (amaranth leaf), but none in the vacuoles. In group VI, two or more peaks appeared on the plastid and one on the vacuole of red flowering cactus (Brasilicactus haselbergii Backbg., Fig.1 L). Among these peaks, those of plastids were due to carotenoids, and another peak of vacuole was betacyanin. Accordingly, it becomes evident that the characteristics of absorption curves of intact cells are sufficiently indicative of a series of major pigment components in colored plant organs.

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Genetic behavior of kernel weight and frequency of white belly rice was studied using hybrid populations of four crosses. Base populations were maintained by single seed descent method until F8 (H-347×Yukara and its reciprocal) or F₃ (Shin 2×Sesia and Shin 2×Fusayoshi). The top and bottom 5% for the above two characters were selected in each F₂∼F₇ (only F₂ in tlle latter two crosses) generation of the base populations and the selection responses were evaluated in the following generations. Heritability estimates were obtained by the equation, h2=R/S, where R and S stand for selection response and selection differential, respectively. Genetic correlation coefficient was calculated with the formula rGAGB=(CRA/RA) × (hA/hB), where CR is correlated response. Frequency distributions for kernel weight were nearly normal in all populations but those for white belly frequency were highly skewed except for F₂ of Shin 2×Fusayoshi (Figs.2, 6 and /7). In the populations examined, 1, 000-kernel weight ranged from 17 to 37g and frequency of white belly rice varied from O to 100%.

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It was pointed out that the genotypic frequency in a population after generations can not be obtained through the traditional method, i.e., through multiplication of gene frequency and inbreeding coefficient utilized in population genetics.

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Leaf discs of Prunus lannesiana Wils. were cultured on a medium supplemented with 10-5M 2, 4-dichlorophenoxyacetic acid (2, 4-D) and l0-6M 6-benzylaminopurine (BA). After one month culture, the initiated callus was transfcrred to the medium supplemented with various concentrations of BA (10-4-10-7M), and to a hormone-free medium. Adventitious buds were induced after about three weeks culture from transfer. Root formation of the differentiated shoots occurred after transfer to a hormone-free medium.

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