The effect of combination of air and water temperatures (29, 23 and 17±2°C respectively) on the number of days to heading, the rate of leaf development and the total number of plant leaves were investigated by using three japonica rice cultivars (Oryza sativa L.) which differ in the length of their basic vegetative phases (BVP) and photoperiod-sensitive phases (PSP). The name of cultivars were Norin 20 (short BVP and short PSP), Norin 1 (long BVP and short SPS), and Zuiho (short BVP and long PSP). The results are summarized as follows : 1) In the weakly photoperiod-sensitive cultivar Norin 2, compared with higher temperature (23/23 or 29/29°C : air/water temperature) the number of days to heading under low temperature due to a retardation of (17/17°C) slightly increased. This was the rate of leaf development. The total numbers of leaves in each treatment remained fairly constant despite varying air and water temperatures. 2) In the strongly photoperiod-sensitive cultivar Zuiho, the number of days to heading under low temperature remarkably increased not only because of a retardation of the rate of leaf development but also because of an increase in the total number of leaves. This leaf increase was determined more by a low air ternperature than by a low water temperature. 3) In the weakly photoperiod-sensitive cultivar Norin 1, the number of days to heading under low temperature did not increase as much as Zuiho. By retarding the rate of leaf development under low temperature the number of days to heading decreased in relation to the decrease in the total number of leaves. This leaf number decrease was determined more by low water temperature than by low air temperature. The general conclusion that can be drawn from these results is that the variation among the cultivars with respect to the effect of temperature on the number of days to heading can not be attributed to the rate of leaf development. Instead it can be attributed to total number of leaves which is determined by the interaction between the air and water temperatures.

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Protoplasts isolated from nucellar callus of 'Trovita' orange (Citrus sinensis Osbeck) wvere cultured in a MURASHIGE and TUCKER'S medium containing 0.15 M sucrose, 0.45 M glucose, and 0.6% agar, but lacking phytohormones. Colonies with 26.3% plating efficiency were observed after 6 weeks culture. When the protoplasts were cultured in the presence of exogenous phytohormones, reduction in colony formation was observed. Some colonies developed to green embryoids, which eventually formed plants.

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The adventitious buds and globular embryoids were obtained from a nucellar seedling of a trifoliate orange by the use of two kinds of plant hormones, i. e., α-naphthaleneacetic acid (NAA) and 6-benzyl aminopurine (BA). The highest frequency of induction of the adventitious buds was obtained, when 1.0 mg/l NAA and 5.0 mg/l BA were supplemented to the culture medium. Adventitious root formation was promoted by the supplement of 2.0mg/l NAA to the culture medium. A micropropagation scheme for a trifoliate orange was put forward.

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Protoplasts from suspension cultured cells of Petunia hybrida. whlch had lost the ability to regenerate shoots were fused with protoplasts from leaf mesophyll cells of P.parodii which could not grow beyond a small colony stage. Fused protoplasts showed a more vigorous growth pattern than the parental protoplasts, and formed colonies which could regenerate shoots. On the contrary, parental colonies could not regenerate shoots. The hybrid nature of regenerated plants was confirmed by the color of their flower buds, their characteristic isozyme patterns and the morphology of the regenerated plants. Also, from the fact that the plants could be regenerated from hybrid cells between two different protoplasts each of which could not regenerate shoots, it was confirmed that they were somatic hybrids. Cytological analysis revealed that suspension cultured cells had 24 chromosomes in contrast with 14 chromosomes of root tip cells of both parents. On the other hand, somatic hybrid calli mostly consisted of cells which had 44 chromosomes. Somatic hybrid plants had distorted leaves and all flower buds deteriolated prematurely. These phenomena were partially attributed to higher chromosome numbers of cells of somatic hybrid plant compared to those of parental plants.

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Effects of gibberellic acid (GA3) on Culm internodes were observed in the rice dwarf mutant, Fukei 71, and its original cultivar, Fujiminori. Although plant heights in the vegetative growth period, panicle number and elongated internode number of culm were greatly affectecd by GA3 repeated treatments at 3 to 4 days intervals in Fukei 71 and Fujiminori, no significant difference was detected in the responses of these characters to GA3 between both cultivars. On the contrary, a marked difference was observed in the response of culm elongation to GA3 between two lines. Under the greenhouse or high temperature (30°C-25°C) condition, the culm elongation of Fujiminori was strongly promoted, while Fukei 71 did not respond as strognly to GA3 as Fujirninori. Especially, it is noteworthy that Fukei 71 showed the similar responses at three levels of GA3 concentration. However, it was observed that under low temperature (23°C-18°C) condition the response of culm elongation to GA3 in Fukei 71 restored very nearly to that of Fujiminori. The parenchyma cells in the elongated internodes caused by GA3 treatments in Fukei 71 had an abnormal form compared with those of Fujiminori, and the form resembled to that of parenchyma cells in the upper internodes of Fukei 71 as shown in the previous work (KITANO and FUTSUHARA 1982). Gibberellin-like substances were ascertainecl by the bioassay with Tangin-bozu and Waito-C in the acidic ethyl acetate fraction of 70 percent aceton extracts from the culm, panicle and leaves of Fukei 71 and Fujiminori at various growth stages. The similar level of GA activities was cletected in Fukei 71 only Tangin-bozu assay, compared with Fujiminori. No GA activity was detected in both culitivars with Waito-C assay

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A rice cultivar Shin 2 derived from a cross combination, Kameno-o 1×Kairyo Kikoku, develops notched grains with high percentage especially under low temperature condition, whereas their parental cultivars produce notched grains very little. Thus, Shin 2 canbe regalded as a transgressive type in respect of grain-notching. To clarify how the grain-notching line has been derived from the 'normal' parents is the main purpose of this study. The flrst experiment was performed using F₂ and F₃ plants of a Kameno-o 1×Kairyo Aikoku cross. After a preliminary test of F₂ and F₃ plants, a total of 918 F₂ plants, and tneir parents and Fl plants as well, were investigated for notched grain frequency and caryopsis length in 1976. About a half of the F₂ plants developed notchecl grains with a maximum frequency of 36%. The top and bottom 5% of the F₂ population were selected for grain-notching, and the F₃ lines were evaluated in 1977. Heritability value of the noched grain frequency estimatecl from the selcction response was 0.67. The hibohest mean value of notched grain frcquency was 39% in F₃ lnes evaluated (Fig 1).

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In order to obtain basic and necessary information for more effective potato breeding, this study was conducted to investigate the following : the relationships among characters by inferring genetic parameters of agronomic characters on fields with low, standard and high levels of fertilizer application; the factors determining starch yield (SY) and their contributory ratios to SY (path-coefiicient analysis); the effectiveness of indirect selection for the varieties most suitable for each cultivating condition (correlated response).

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Studies were carried out to consider from the viewpoint of isozyme analysis some genetical relationships among Brassica genome types and to examine whether the isozyme method could be applied in identifying hybrids at an early stage of growth. Several varieties were selected from each Brassica genome type. Seeds were sown in pots at the end August. Plants at the 4th leaf stage of each genome type were collected and the stems were used as the material. In this experiment, peroxidase and esterase isozymes were analyed by starch gel electrophoresis. The starch gel was prepared in 0.03M borate buffer (pH 8.5), using hydrolyzed potato starch. The samples, approximately 1g in fresh weight, were ground with a homogenizer. The homogenate was placed on a filter paper strip, and the strip was inserted into the gel at a disttance of 8cm from the cathodal edge.

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Genetic analysis was carriecl out on eight quantitative characters in the silkworm by diallel crosses of eight varieties differing widely in each character. As the results of the estimation of genetic variances and of the regression analysis of Wr (parent-offspring covariances) on Vr (array variances), additive effects (D) were larger than dominance ones (H1) in five characters: growth rate at the 5th instar, raw silk percentage, length of cocoon filament, size of coccon filament and reelability, and thus these characters were recognized as incomplete dominance. However, two characters: pupation rate and cocoon weight, were recognized as overdominance, because dominant effects were larger than additive ones. Cocoon shell weight was further recognized as complete dominance. Epistatic effects were observed in four characters: pupation rate, cocoon weight, size of coccon filament and reelability. Cytoplasmic effects were also observed in pupation rate and size of cocoon filament. Reciprocally different values were observed in growth rate at the 5th instar, perhaps caused by the effect of the sex-linked Lm-alleles.

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The analytical results of chromosome composition of substltutional triticale lines spontaneously derived from octoploid triticales showed that all five lines examined had chromosome 2D. Preferential chromosome substitution of the 2D-2R in triticale may be due to selection advantage of the 2D for seed fertility. A genetical model on the relation between fertility and wheat chromosomes of homoeologous group 2 with 2D was presented.

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A very early-maturing, intermediate plant height, long-grain rice variety, "Callfornla Bell" (NFD-69), and a very early-maturing, short-stature, pearl rice variety, "Calpearl" (NFD-62 C), were developed by hybridization. Yield trials were carried out with California long-grain, medium-grain and short-grain check varieties. Averaging three years' seeding dates in the Firebaugh breeding nursery, one year's small plot adaptation test in four different rice-growing areas, and one year in a large commercial-scale field of a major rice-growing area, Calpearl came out in the first class with significantly higher yields (>10%) than all check varieties. Averaging early, mid-season and late plantings, Calperal yielded more than 11 tons dried paddy per hectare. California Belle ranked in the second class, but there was no significant yield difference as compared with M-101, a very early-maturing short-stature check variety. Three early-maturing check varieties were included in the third class after Duncan's test. Calpearl had especially high produc-tivity after delayed planting, which makes it attractive as a second crop following winter crops of barley or wheat. Calpearl has a larger grain size than the California short-grain varieties and is the first pearl-type rice with attractive translucent kernels without white belly or chalkiness. California Belle has slender grain, translucence, also without white belly or chalkiness. Chemical analysis on milled rice starch showed that both Californla Belle and Calpearl were typical and met U. S. long-grain and short-grain standards, respectively. Cboked California Bell rice is extremely white with favorable texture and taste. The success of long-graln breeding introduces a new phase in the California rice industry. Indica genes incorporated in Japonica rice have made the highly-productive Calpearl possible.

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