It is sugcrested that cultivated pears in Japan are improved from the wild pears, Pyrus serotina Rehder, or that original pears had been introduced from China and or Korea to ancient Japan. Besides P. serotina, two wild pear species, P. hondoensis Nakai et Kikuchi, and P. aromatica Kikuchi et Nakai, grow in Japan. Therefore, there may have been hybridizations among the three above-mentioned species and also Chinese pears. So, there is still a problem in the taxonomical position of cultivated pears in Japan.

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From the tissue cultures of syncarp, slip, crown and axillary bud of Ananas comosus (L.) Merr., cultivar Smooth Cayenne, 448 plants were established. To exarnine the two possible merits of this technique on self-incompatible plants of vegetative propagation, mass-production of non-variants and induction of variants useful in breeding, the variations among the redifferentiated plants were investigated. Many variants regarding spine, leaf color, wax secretion on leaf surface and foliage density were found among the established plants. There were a few variarlts with narrow leaves or albino stripes. Organ-to-organ differences were found in the fre-quencies and the modes of distribution of these variations. Syncarps and a slip developed variants in high frequencies, while crowns and axillary buds did only in low frequencies. The variants from syncarps included the characters on leaf color, spine, wax and foliage density, but the ones from a slip, crowns and axillary bu.ds were almost confined in spine characters. From these present findings, it is considered possible to apply the tissue culture technique on the rapid propagation of non-variant plantlets and the induction of useful variants, if proper kinds of organs are chosen for the respective purpose.

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This study aims at investigating how temperature affects the growth of rice embryo developlng under three temperature conditrons (30-25°C, 25-20°C 20°C) As expected the increase in length and in cell number was delayed as the temperature fell. But the cell number at the start of exponential growth and that at the changing point of the rate of increase in cell number did not vary with the temperature. Also, the coef-ficient of allometry between the length and thickness changed at definite embryo lengths irrespective of the variation in temperature. The modification in embryo shape, esti-mated by the residual variance in the coefficient of allometry and by the coeficient of variation in the ratio of the thickness to length, was wide at the globLllar stage irrespective of the temperature conditions and inceased as the temperature foll. Treatment consisting of exposure to low temperature of 20°C was applied at various developmental stages when embryos were developing at 30-25°C. Embryo growth was delayed by about 12 hours immediately after such treatment. This delay was observed in every treatment until the embryo had almost reached maturity. Therefore, the pat-tern of embryo growth curve is considered to be stable. On the other hand, the shape of the embryo varied more widely than that of the control after exposure to a temperature of 20°C at the globular stage (especially in the late period). When such treatment was applied after the second leaf had differentiated, the variation in embryo shape was not wider than in the control. These results indicate that embryo shape is unstable at the globular stage and become stable after the embryo is differentiated morphologically.

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The purpose of this study was to grope the hormonal requirements for the differentiation of complete plantlet from hypocotyl and hypocotyl callus of Cucumis sativus L.cv. 'Shinko Fushinari No.10'. At first, segments of hypocotyl (1 cm) in young seedling were inoculated on the agar media (MURASHIGE & SKooG's basal medium) with various combinations of auxin (NAA) and cytokinin (BA) concentration. Subsequently, half of the cultures were untouchedly cultured on the same media, not transferring hypocotyl callus to another medium. The callus formed from other half hypocotyl were transferred to another media, that is two kinds of media with 1.0ppm BA alone and in the absence of NAA and BA, being di-vided into the small mass the size of an adzuki bean. Callus formation from hypocotyl required alternative or both addition of auxin and cytokinin at O.1ppm or higher levels of concentration, although callus was favourably fcrmed for the most part. Root formation was observed at the media with the combination of O-10.0ppm NAA and O-1.0ppm BA and the ratio of root formation generally increased as BA concentration becomed lower. On the other hand, shoot formation was observed at a low frequency on the media with BA concentration either higher than or equal with NAA concentration, that is, with the combination of O-1.0ppm NAA and 1.0ppm BA. However, only a few of the shoots continued to develop and one complete plantlet was finally obtained at the medium with O.O1ppm NAA and 1.Oppm BA. Shoot formation from the transferred callus was observed at a low frequency only when calluses produced on the medla wlth the combinatron of O.O1-1Oppm NAA and 1.Oppm BA were transferred to the two kinds of media for redifferentiation. It appeared from this result, as lettuce and tomato, that whether shoot was formed from callus or not was destined by the relative concentration between auxin and cytokinin in the medium for callus induction. Complete plantlets were obtained at a low frequency on the meium in the absence of NAA and BA. Root formation was Observed only when shoot vv-as L0rmed on the media in the absence of NAA and BA.

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Twelve seed collections of tobaccos growing wild in the Okinawa district were evaluated for certain morphological characters and disease resistance. CG, nsiderable variations in morphological features and disease reactions were noted among these collections. Plant height ranged from 95.3cm to 171.9cm, the number of leaves from 9.8 to 17.3 and leaf shape index from O.471 to O.764. There were two types in the shape of leaf-base, sessile and petioled, and three types in flower color, white, pink and white/pink variegation. Most of the collectibns were highly susceptible to bacterial wilt, but moderately or slightly resistant to black root rot and powdery mildew. There were large differences in their reactions to black shank; sorne of them were highly or moderately resistant and the others were highly susceptible. The collections which were rated resistant were considered to be useful as a source of black shank resistance.

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The present study was carried out to find out the inter- and intra-specific relationships in the genus Camellia. Isozymes of peroxidase, esterase and acid phosphatase in leaf blades of Camellia species, mainly C.japonica, C.sasanqua and C.sinensis, were investigated by polyacrylamide gel electrofocusing method. Zymobcrram patterns detected in these enzymes were not species-specific. Many different zymograms were found within a single species, some of which were in common with other species (Table 2). Some bands common to all species were also detected in each enzyme species (Fig.1). In acid phosphatase isozymes, distinct differences among species were not observed. Data obtained were treated by the technique of pattern analysis (HAYASHI 1956) to obtain an integrated picture, because the assortment of species by zymograms was difficult due to the wide variation within the species (Fig.2). In the scatter diagrams for peroxidase, distribution areas of C. sinensis, C.japonica and C. wabiske were overlapped and that of C, sasanqua was placed distantly from them. On the other hand, in the scatter diagrams for esterase, distribution areas of C.japonica and C.sasan-qua were overlapped and that of C, sinensis was placed distantly. Therefore, it was con-sidered that the evolutionary trend of each enzyme species was independent. The measure of divergence (Table 3) showed a similar trend to that obtained by the pattern analysis.

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In order to estimate the degree of genetic recombinate on and genetic homogeneity in the interspecific hybrid progenies between Vicia alephicarpa, true (female) and V. macrocarpa (male), amylase isozyme patterns were analyzed by disc electrophoresis. Each parental species has three amylase bands, of which two ai-amylase (a₁ and a₂ band) were common, but one B (B₁ or B₂) was not. B₁ band was detected in male and B₂ in female parent. Both F₁ and F₂ Showed fcur bands derived froni the parents. Zymograms detected in the F₃ and F₄ were assembled in ten groups according to the pattern. These groups were characterized by the presence or absence of both parental bands. The frequency of male parental-band (type I) was higher in F₄ than F₃, and that of F₁ band (type VIII) was lower in F₄

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In order to elucidate the variation in Persea americana complex (avocado) and ta know the genetical relationships among strains and among races, morphological characters of 61 different avocado strains were analyzed statistically. The analyses of variance on 30 morphological characters at four-months-old seedling stage so far recorded in these materials clearly demonstrated a great genetic diversity of the germ plasms. The great diversity agrees well with earlier studies. The analyses of variance also showed that 15 out of the 30 characters examined were useful in characterizing, at least, strains, and that 14 out of the 15 such characters were also useful to distinguish races of P. americana. When six scattering diagrams were drawn based on six pairs of two characters which showed high F values arnong races and exhibited different extents of correlation to each other, it was found that Mexican-race strains tended to have smaller sizes than Guatemalan- or West Indian-race strains. Closer relationships were observed in the scattering diagrams between Guatemalan- and West Indian-race strains. Thus the genetic relatedness between Mexican and other races was concluded to be less closer, as compared with that between Guatemalan and West Indian races.

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[in Japanese]

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