Ovules (undeveloped seeds) unable to mature were taken out from the ripe fruits which were obtained by cross-pollination between L, esculentum as female parent and L.peruvianum or L.glandulosum as male parent. After the jelly-like coatings covering the ovules were removed by washing sufficiently with tap water, the ovules were treated with a 2% sterile antiformin solution for 6 to 12 min. After washing several times with sterilized water, the ovules were plated onto MS agar medium (MURASHIGE and SKOOG, 1962) without phytohormone. The number of ovules germinated per fruit in each combination of the F₁ and BC1 hybrids was as follows ; 0.79 in "Kyoryoku Toko"×L.glandulosum, , 0.48 in "Kyoryoku Toko"×F₁ ("Kyoryoku Toko"×L.glandulosum), 0.76 in "Early Pink×the same F₁, 1.55 in "Kyoryoku Toko"×F₁ ("Kyoryoku Toko"×L.peruvianum). In all the crosses, about 8O% of the germinated ovules grew up to normal plants and most of them were found to be true hybrids by the observation of morphological traits. Thus, each fruit contained about one ovule which was able to germinate when it was cultured in vitro. Furthermore, such an ovule capable of germination could be distinguished from others with a high probability, as its size fell into a limited range and it displayed a characteristic color and shape. Based on these results the in vitro ovule culture is considered to be a convenient and effective method for the production of F₁ and BC1 hybrids between L.esculentum and L.peruvianum or L.glandulosum. On the other hand, the choice of a female parent is also considered to be a main factor in the performance of the cross.

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The relationship between resistance to lysine plus threonine equimolar solution (LT) and free amino acid contents in 10 rice varieties was studied. When seeds were germinated and cultured in 5×l0-4M LT for 7 days, difference in the extents of growth inhibition among the varieties was clearly recognized. Free threonine contents in both seeds and 14-day-old seedlings were. also varied amonb" varieties. In particular, free threonine contents in the seedlings of Shirowase and Binicol, which were classlfied as LT resistant varieties, were extremely hlgher than those of the other varieties. Threonine contents of the two varieties were over 17, 000 nmol/g fresh weight, while the contents of the other 8 varieties were below 8, 000 nmol/g fresh weight. Free lysine contents also increase in the seedlinb"s with increased levels of LT resistance, but not as much as free threonine contents. On the other hand, none of the varieties used in this experiment overproduced free threonine and lysine in the seeds. From these results, it is suggested that LT resistance can be used as a parameter for breeding crops with higher threonine contents.

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Germination speed and germination uniformity were studied in F₁ seeds of diallel crosses of six inbred lines of Nicotiana rustica under nine controlled environments differing in temperature, salt concentration and light condition. There was clear evidence of the additive and non-additive genetic effects on germination speed and germination uniformity. Maternal effects seemed to be involved. The genetic variation in germination speed was not associated with that ingermination uniformity. Rapid and uniform germination was dominant over slow and sporadic germination, respectively, although in some environments the dominance in germination uniformity was ambidirectional. The genotype-environment interactions were also observed. A significant part of the interactions could be explained by Jinear regression and deviations from the regression. The inheritance of linear response to environmental changes and the deviations from the regression were due to additive and maternal effects in both the germination characters. The response of germination speed to environmental changes was genetically independent of the response of germination uniformity.

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The effect of exposure dose and dose rate of gamma radiation on shoot-forming capacity of cotyledon explants of red pepper were investigated. The twelve-day-old seedlings were irradiated by gamma radiation with varying exposure doses of O, 0.5, 0.75, 1.0, 1.25, 1.5, 1.75, 2.0 and 2.5 krad delivered at the dose rates of l, 5 and 10 krad/ hr. After irradiation, cotyledons were excised from the seedlings and cultured on MURASHIGE and SKOOG medium supplemented with benzyladenine at the concentration of 3 mg/l to induce shoot formation. It was found that the percentage of shoot-forming explants and the number of shoots per explant were decreased as the exposure dose increased. Moreover, the increase in exposure dose delayed callus and shoot bud formation and inhibited the development of shoot buds into vigorous shoots. At the same exposure dose, the higher dose rate (10 krad/hr) was more detrimental for shoot formation than the lower ones (1 and 5 krad/hr). The exposure dose which caused 50 percent reduction in the number of shoots per explant (RD50) was around 1.0 krad at the dose rates of 1 and 5 krad/hr whereas RD50 was 0.75 krad at the rate of 10 krad/hr.

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The chromosome complements of two cytotypes of Vicia macrocarpa were investigated and it was observed that the karyotypes changed in relation to the position of centromere, length of chromosome arms and number and nature of nucleolar chromosomes. At the same time changes in some morphological and physiologlcal characters of the plants were also observed. In addition, the two chromosome complements were studied for their banding pattern at the mitotic prophase and metaphase. It was evident that the two cytotypes also showed differences in the amount and distribution of heterochromatin. One of the cytotypes (12E) exhibited a larger number of C-bands than the other (12C). It is concluded that the evolution of V.macrocarpa has been towards a decrease of the amount of heterochromatin, along with the changes of the karyotype. Various multivalents ranging frorn trivalents to hexavalents were observed in some cells at the meiosis in the F₁ and F₃ of 12Cxl2E. It was thus d.emonstrated that the two cytotypes differed by the presence of two reciprocal translocations. It was possible to identify the parent-derived individual chromosomes at both the mitotic stages and meiosis of the F₃ plants based on the differences in the heterochromatic bands ancl centromere position. The extra-chromo some of a trisomic plant in the F₃ was identified at the mitotic prophase as well as the chromosomes involvecl in the multivalents at the meiosis of the hybrids.

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Leaf protoplasts were prepared from the plants grown in the phytotron with artificial illumination. Cytoplasts were obtained by ultracentrifugation of leaf protoplasts on the top of Percoll iso-osmotic discontlnuous density gradiants as described by LbRZ-et al. (1981). After centrifugation, the cytoplasts fraction was pipetted off from the top of the gradiant. According to microscopic observation, cytoplasts were highly vacuolated. chloroplast-poor cells and could be easily distinguished from the green leaf protoplasts. The number of cytoplasts and protoplasts in the cytoplast fractions was counted by Fuchus-Rosenthal haemocytometer. The optimal conditions for isolation of cytoplasts were determlned from a relationship of centrifugation speeds and running time. The yield of cytoplasts was decreased with increasing the diameter of leaf protoplasts. Cytoplasts isolated from Shiga's Cytoplasmic Male Sterile (CMS) rape (Brassica napus) were fused with leaf protoplasts of it's maintainer (B.napus cv. Bronowski) In the presence of polyethylene glycol. The Lusion process was observed with the passage of time by the color laser microscope. Cytoplasts and protoplasts were Lused immediately after their attachment.

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The plants obtained by crosses between C₃ and C₄ species in Atriplex were determined to be hybrids in views of morphology and δ^l3C values. One F₁ plant of A, triangularis (C3, n=9) x A, rosea (C4, n=9) and one of the reciprocal cross had good pollen and seed fertilities. No prominent differences were observed between these reciprocal Fis in morphological characters. Most of the F₂ plants showed a high pollen fertility (more than 70%), and 19 out of the 20 plants so far examined formed normal bivalents. A, triangularis has an opposite phyllotaxis, while A. rosea has an alternate one. Segrega-tion of the F₂ for the phyllotaxis was accounted for by assigning two recessive genes to the alternate form. The bundle sheath cells of F₂ were many in number but small in size. A very small number of chloroplasts were sporadically observed in the bundle sheath cells in a few plants. Photosynthetic properties of the F₂ were examlned in terms of light-photosynthetic curves, transpiration rates and carbon isotope discrimination values (δ^l3C). In some F₃ plants observations were made on the C0₂ compensation points, photo-respiration activities and several enzyme activities relating to the C₄ photosynthesis. No plants with C₄-like photosynthetic activities have been found in the F₂ nor F₃, so far. Possible reasons why no C₄-Iike plants were found in the F₂ were discussed.

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Barley varieties classified into three isozyme patterns by isoelectric-focusing of high pla-amylase were crossed. F₂ and F₃ segregation for the banding patterns of a-amylase indicated that the three types showed basically co-dominant relationships. In the cross-combination of type lxtype 2 ('Haruna NijoxKlages' and 'Haruna Nijox Clipper'), new banding patterns were observed with a low frequency. It was estimated that the gene coding for the band detected only in type I was transferred from type l to type 2 with the genetic recombination. The estimates of the recombination values were 5.3:tl.8% ('Haruna NijoxKlages') and 9.7:i:3.1% ('Haruna NijoxClipper'), respectively. F3 segregation for (x-amylase activity in germinating seeds was also examin" ed. The results revealed that the differences in the structural genes were not definitely related to the activity of a-amylase, and that the variety Haruna Nijo harboured a few genes with dominant effects relating to a-amylase activity.

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Besides the ordinary six-rowed and two-rowed barley forms, there is another small group of varieties named 'irregulare (labile)', which occur only in Ethiopia and the North India-Pakistan districts. In the 'irregulare' type, central florets are completely developed like in the normal six-rowed forms, but the lateral florets of some triplets are missing, although rachillae and empty glumes are present (Fig. l). The percentage of missing laterals in the irregulare type varies widely, ranging from O to 90%.In this study, a diallel analysis of the percentage of missing laterals was carried out using ten 'irregulare' varieties from Ethiopia. 10x1O diallel F₁'s, including their reciprocals, and the parents were grown in the field with two replications. Three plants per plot were harvested and ten ears per plant 1'vere used to determlne the percentage of misslng laterals. The percentage of missing laterals was expressed by the ratio of the (number of missing lateralsx1OO)/ (number of tripletsx2). In the statistical analysis the ratio was transformed to angle. The percentabae of missing laterals of the parental varieties varied from O to 35% (Table 1). Additive as well as dominance effects of the genes were significant. No reciprocal difference was observed (Table 2). Epistasis of the genes seemed to be non-significant (Tables 3 and 4). The W_r/V_r graph suggested that the genes were incompletely dominant and the epistasis was absent (Fig.2). As shown in Table 6, broad and narrow sense heritabilities were O.83 and O.74, respectively. The number of effective factor pairs was 4-6 the domlnant genes belng more frequent than the recesslve ones. A high positive correlation between W_r/V_r and the percentage of missing laterals of the corresponding parents indicated that those varieties with a high percentage of missing laterals involved more recessive genes (Fig.3). Although the ratio of the dominance (√H₁/D) was O.5 on an average, the dominance level markedly varied with the cross combinations (Fig.4) .

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The effect of growth rate (dry-matter increment per plant per day) at internode-elongation stage on the elongation of internodes was investigated, using a rice variety Gimbozu and 15 mutants of the variety, which differed in culm-length and/or heading time. The materials were grown in two cropping seasons in randomized block design with two replications. Every two weeks after transplanting, seven plants per plot were sampled and measured for top dry-matter weight per tiller. With 18 other standing plants, top dry-matter weight was estimated each by multiplying its tiller number by the top dry-matter weight per tiller. Then, Pearl-Reed's quadratic equation was fitted to thus estimated values, and the growth rate at any stage was evaluated through the equation. Heading date, culm length and internode length were also measured. The following results were obtained.

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In Brassica crops there are various inter- and intra-specific diversity of pollination requirement to set seeds, ancl the insect pollination enhances seed set percentage not only in monogenomic Brassica species, B. campestris and B.oleracea (FREE 1970), but also in digenomic Brassica species, B.napus and B. juncea (OLSSON 1960, OHSAWA and NAMAI 1987). However, there is no cletailed information on pollen flow correlated with behavior of insect pollinators within a Brassica crop population. Accordingly, we studied the pollen fiow associated with visiting behavior of insect pollinators and estimated the promising planting pattern f'or hybrid seed production in Brassica napus using cytoplasmic male sterility (cms). In the Ist experiment, the correlation between pollination behavior of insect pollinators and cross-pollination efficiency was clarified. Twenty plants of cms B. napus cv. Isuzu-natane as seed parent were grown in isolation cage (L 3.4 m xW 1.4 m XH 1.6 m) without insects. The pollen parents, B.napus cv. Bronowski and cv. Waseaburana were grown in pots and carried together into the cage at the onset of the experiment. Artificially reared Shimahanaabu (Eristalis cerealis) was used as insect pollinators and released one by one into the cage. The visiting behavior of the insects were observed continuously and the visiting time lengths of each Shimahanaabu were recorded from 9:OO to 11:30 a.m. for 6 days during the period from May 5 to May 10. Each Shimahanaabu was compelled to visit the pollen parent first before visiting the seed parent. The flowers visited by Shimahanaabu were sampled immediately after Shimahanaabu left, and pollen grains deposited on each stigma were counted.

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Wheat callus and suspension cultures were initiated from 22 immature haploid embryos obtained from intergeneric crosses with Hordeum bulbosum L. using an F₁ wheat hybrid. Two different callus lines were induced after 10 weeks of suspension culture. One line consisted of compact and friable callus clusters which proliferated rapidly in a liquid medium. A few of the calli transferred onto the solid medium were regenerated to green plants through somatic embryogenesis. The other line, growing slowly, consisted of somatic embryoids which were successfully regenerated to green plantlets, but in most of the cases failed to undergo further development. The difference in the behaviour of wheat suspension cultures was discussed.

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