Studies on development in vitro of excised ovaries in the interspecific crosses between Brassica campestris L.ssp. pekileensis (Lour.) Olsson cv. Nozaki-hakusai and Brassica oleracea L.var. capitata L. cv. Nozaki-wase and cv. Nozaki-nakate, and in the sibmates of the two species were carried out. Development ile vitro of the ovaries excised fcur days after pollination was studied at various culture media with yeast extract and casein hydrolysate, which were added either separately or in various combinations. (1) In the sibmate of B. campestris, many seeds Results obtained were as follows. (2) In the sibmate of B. oleracea, seed set in were obtained in all the media used. the capsules was low in all the media used. (3) In the interspecific crosses of B. caleapestris x B. oleracea (Nozaki-hakusai x Nozaki-wase and Nozaki-hakusai x Nozaki-nakate), seeds and well developed naked-embryos protruded from undeveloped seed coat were obtained in the capsule. Production of seeds and the naked-embryos was best in the medium with 300mg/l of casein hydrolysate. These naked-embryos were also obtained in the basic medium. Developmental stale of the naked-embryos obtained in the capsule was from torpedo-shaped to full-grown embryo. Seven of 49 embryos further cultured and were proved to be hybrid. Two of 7 seeds obtained grew and also showed hybrid. No difference in morphological characteristics of leaf and inflorescence was observed among them.(4) In the reciprocal cross, B. oleracea x B. campestris (Nozaki-wase x Nozaki-hakusai and Nozaki-nakate x Nozaki-hakusai), no seeds and no developed naked-embryos were obtained in all ovaries cultured. (5) Culture in vitro of excised ovaries is useful as a new technique for production of interspecific hybrids in Brassica campestris x Brassica oleracea.

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In order to pinpoint some morphological characters which would be easy to measure and would be helpful for the effective selections for root weight and sugar content of sugar beets, selections for the rapidity of leaf differentiation and size of a lamina were made. The former foliar trait showed a strong parent-offspring correlations with itself, root weight and sugar content. The latter trait showed a lower heritability than the former one, and no parent-offspring correlations with the root characters were seen. However, a detailed inquiry revealed that the latter foliar trait might be also useful as a criterion for selection. A concomitant improvement in root characters was not realized by the selection of these foliar traits, but some suggestions regarding the objective were obtained.

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Associations of stomatal frequency with heading date and leaf characters were studied. Nine six-rowed barley cultivars differing in stomatal f.requency were planted in the field in the fall of 1975. Stomatal frequency, dry weight, total nitrogen content, Ieaf vein frequency and leaf area of flag leaf were determined. Leaves were taken from the primary culm of each plant. The values of stomatal frequency, heading date, specific leaf weight(SLW), total nitrogen content per unit leaf area (N/LA), Ieaf vein frequency (LVF), ratio of SLW (1eaf thickness) to the distance between veins(SLW><LVF) (following KHAN and TSUNODA 1971), and leaf area (LA) of the nine cultivars are shown in Table 1. Correlation coeflicients were computed between stomatal Lrequency and other characters, and are presented in Table 2. SLW and N/LA, which are known to correlate with photosynthesis, had no positive correlations with stomatal frequency (Fig.1 and Table 2) . Correlation coefficients between stomatal frequency and LVF and also SLWXLVF were 0.24 and -0.05 respectively. So, LVF or SLWLVF, as the component of the efflciency 0L transport system for the products of photosynthesis, had no strong relationship with stomatal frequency. In conclusion, it appears that the correlation existing between stomatal frequency and photosynthesis is not because of the thick, nitrogen rich and well developed transport system in high stomatal frequency leaf but because of the effect of stolnatal frequency itself on photosynthesis.

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In order to study the effects of competition and cooperation among individuals carring the different genotypes, eight lines of sugar beets were grown in pure stands and incomplete diallel combination of mixtures of between-row. Row component data were collected from center rows grown between the same or different lines. Competitive abilities and cooperating effects of lines were defined in following ways : Competitive ability= (M-P) + (P'-M'), Cooperating effect= (M-P) - (P'-M'), where M and P stand for the mean performances of the line at mixture and at pure stand. respectively, and M' and P' the mean performances of the associate at mixture and at pure stand, respectively. There were statistically signiflcant differences in competitive ability and cooperating effect among the lines. And no relationship was observed each other on performance at pure stand, competitive ability and cooperating effect. These results in sugar beets suggest that competitive ability and cooperating effect would be under the genetic controls and be independent from the plant type and/or growth vigour. respectively, and M' and P' the mean performances of the associate at mixture and at pure stand, respectively. There were statistically signiflcant differences in competitive ability and cooperating effect among the lines. And no relationship was observed each other on performance at pure stand, competitive ability and cooperating effect. These results in sugar beets suggest that competitive ability and cooperating effect would be under the genetic controls and be independent from the plant type and/or growth vigour.

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The majority of the cultivated species and cultivars of hexaploid Camellia studied showed complete and normal pairing at metaphase I in meiosis, while their hybrids showed various meiotic chromosome configurations and chiasma frequencies at metaphase I. Thus, the predominant formation of bivalents and the high chiasma frequency per bivalent at metaphase I in meiosis shown in the population of hexaploid clones of cultivated Camellia taxa might be due to stable, fertile combinations derived from allohexaploids and segmental allohexaploids in which a large amount of homologous segments might be distributed throughout the genomes. Since such heterozygous chromosome complexes are carried in the hexaploid Caleeellia taxa, no distinct dividing line could be found between so-called homologous and non-homologous genomes, and one genome might merge into the others. Observations on metaphase chromosome pairing in meiosis I in hybrids between hexaploid Camellia taxa have stressed the difficulty of making genome formulas and drawing phylogenetic relationships of Camellia taxa. The presence of sterility and partial sterility shown in hexaploid Camellia taxa and their hybrids might be due to both genetic and chromosomal differences as well as de-veloping petaloidy.

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Vigorous, comparatively high fertile F₁ hybrids were easily obtained from H.radiatus x H.acetosella and they showed almost complcte chlomosome panlng and gave rlse to the vrgorous fertlle F₂. Almost all characteristics of the hybrids were either intermediate between or similar to one of the parents. Apparently the parental species have similar genome constitutions and are closely related.

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Peroxidase isc.zymes of leaf blades were determined at the pH ranging from 5.0 to 7.0 for 240 mulberry varieties by the thin-layer gel isoelectric focusing. A total of 10 kinds of the isozyme bands was found in these varieties (Figs.4 and 5). The varieties were roughly classified into 5 types concerning the isozyme patterns by visual inspection, according to the existence or absence and the stainlng intensity of 6 anodal bands such as A-4, A-5, A-6, A-7, A-8 and A-9. Type I, II, III, IV and V were composed of 38, 46, 13, 2 and 1 per cent of the total number of the varieties used, respectively. Since the experiment was carried out using leaf blades with various leaf age(Fig.1), tree age and planting location, an additional experiment was performed concerning these points and it proved that they had no effect on isozyme variation (Figs.-2 and 3). Varietal afEinities were evaluated from principal component analysis in which the data concerning the staining intensity of 6 anodal bands, namely, A-1, A-5, A-6, A-7, A-8 and A-9, were used (Tables 1 and 2). Both of the 1st and the 2 nd principal components consisted of 59 per cent of the whole of the information. The scatter diagram of scores of these 2 principal components suggests that the varieties of the same type most closely resemble each other, that the varieties of Type II show closer afiinity with those of Types I and III, and that the varieties of Types lv and V show a rather low affinity with those of the other types (Fig.6). Most botanists agree that the majority of the 240 mulberry varieties examined are involved in 3 species, namely, Morus bombycis KOIDZ., M. alba L. and M. latifolia POIRET, depending on the difference in morphological characteristics. Within limits of the experiment, the relationship between those 3 species and the 5 types of isozyme patterns is not yet clarified.

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Dry and pre-soaked seeds of rice were separately treated for 5, 10 and 20 hours with different inhibitors, known to inhibit oxidative phosphorylation and synthesis of protein and DNA and to be a chelating agent, immediately after irradiation with O-30 kR of ⁶^0Co gamma-rays at 10⁴ R/hr. And the potentiating effect by these agents of damage, expressed as seedling height at the 10 th day after irradiation, was surveyed. In dry seeds, the effect of caffeine and chelating agent reached the maximum within the first 5 hours of post-treatment, while that of DNP and agent inhibiting protein synthesis was time-dependent up to 20 hours. Furthermore, inhibitor potentiation was considerably lower in pre-soaked seeds than in dry seeds and its degree became to be less pronounced in the progress of germination with all the post-treatments. Consequently, it is concluded that physiological reversion, which occurrs in relation to the metabolic status of irradiatcd seeds, plays a significant role in lecovery process in an early stage of germination.

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Accumulation of minor genic effects toward an aimed direction througll recombinations is the genetic basis in the breeding for quantitative traits. One of the approaches toward effective use of recombination can be to initiate selection at a later generation after possible recombination and fixation. In this connection, such a procedure as single seed descent has drawn breeders' attention. The purpose of the present paper is by means of a computer simulation to visualize the polygenic recombination among linked genes when linkage acts negatively for desirable recombinations. Stochastic behaviour of a number of loci linked at given reccuTibination values was manipulated to construct a kind of two dimensional quasi-continuous distribution which could respond to selection, reflecting the generation-dependent changes of genetic parameters. Through this simulator, flrst, the change of genetic correlation coeffrcient was examined in the course of selfing as an indicator of the advance of recombination. A functional relationship between the coefflcient and the recombination value was pointed out in an infinite population. Whereas in sample finite populations, the coefticient was found to be subjected to considerable fluctuation and did not seem to be a grood measure of the advance of recombination. Second, the number of individuals which resulted from most frequent recombination was count:ed througrh generations as a measure of the advance of recombination. The increase of this number was evident up to F₄, confirming the advantage of so-called delayed selection. Third, in this simulation population plant selections by a severe criterion were conducted on one of two correlated traits at F₂, F₃ and F₄ under larger environmental variances. As the results increased genetic advance with rcduced correlated response of unselected trait was found in the selection initiated at F₄' Although a larger number of good recombinants were retained in the selection initiated at later generation, no significant difference was detected as to this number, because of wider stochastic fluctuations among trials as well as larger environmental variations.

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