Percentage of successful pod setting in the intersubgeneric hybridization between G.max(2n=40, maternal) and G.tomentella(2n=80, paternal) was estimated to be 2.5 to 7.6% Germinability of the G.tomentella pollens of G.max stigmas, elongation of the pollen tube in the style and arrival of the pollen-tube tips at the ovules were detected by SEM and fluorescence microscopy. Aneuploidy (2n=64) of the hybrid embryo cells and peroxidase zymogram pattern specific to the hybrid-derived calli were observed by light microscopy (smear method) and polyacrylamide gel electrophoresis, respectivly. Moreover, histlogecal observation of the hybrid embryo was carried out to investigate the extant of the hybrid embryo growth. It was concluded that morphologically normal growth may continue at least until heart or a more advanced developmental stage, but markedly retarded growth accompanies it and eventually it ceases growing and death of the hybrid embryo results. Though, we couldn't get intact hybrid plant, all of the facts revealed proved formation of the genuine hybyid embryos between G.max and G.tomentella.

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Peroxidase isozyme activities were examined to compare the usefulness of various tissues under different environments for estimating interspeclfic differences between two potato species. Solanum pinnatisectum and S.multidissectum. A total of sixteen peroxidase isozyme bands were distinguished in the two species. The expression of these bands changed depending on species and tissue sources as well as environmental conditions. The environmental effect was larger in leaf tissues than in tuber tissues, and larger in S.multidissectum than in S.pinnatisectum. S.pinnatisectum and S.multidissectum had four and two species-specific bands, respectively, of which four were unique either to leaves or tubers and the remaining two were common to both tissues. These species-specific bands are useful to distinguish between the two species. Based on total band activities including non-specific ones, a mean Euclidean distance was utilized to estimate an interspecific difference between them. Both tuber and leaf tissues gave significant interspecific differences under the controlled environment. Our study thus indicates that leaf tissues, like tubers, can provide a useful material in peroxidase isozyme analysis in Solanum species.

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Dormancy in cereal seeds of oat, barley and rice is usually broken by a higher oxygen tension. In this experiment, however, the inhibitory effect of high oxygen tension on seed germination was observed in the seeds of japonica rice, unlike in those of indica and wild type rices. Standard dehusking, which increases the supply of oxygen to the embryo of a seed and the increment of the oxygen tension in the atmosphere surrounding an intact seed strongly inhibited germination of rice for a certain period of time after harvest. This inhibition was not observed under anaerobic conditions, such as in water and at a low oxygen tension. The inhibitory effect was especially recognizable in japonica rice seeds with a high water content irrespective of whether they were dormant or non-dormant cultivars, but not in indica or in wild rice (O. perennis MOENCH and O.sativa f.spontanea ROSCHEY).

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In order to define the role of anther on the pollen embryogenesis in anther culture of tobacco, the presence or absence of starch granules, amount of soluble sugars and content of free amino acids in cultured anthers were investigated through comparing with those in in vivo anthers. Starch granules in the tissues of cultured anthers disappeared rapidly, and the amount of soluble sugars also decreased soon after the onset of culture. Only a very small amount of soluble sugars was detected during the first 6 days of culture although sucrose was supplemented to the medium. On the 8th day of anther culture, the amount of soluble sugars, especially sucrose increased. It is known that pollen embryogenesis of tobacco can be induced under condition of sugar starvation in the culture medium. These results indicate that in the initial period of culture, the conchtions of the anther loculus are favorable for the induction of pollen embryogenesis. From the results of free amino acid analysis of cultured anthers, it was revealed that large amounts of glutamine and asparagine were present in cultured anthers on the 10 th day of culture when cell division leading to embryo formation began in cultured anther, although no amino acid was supplemented to the medium. It has been reported that certain amino acids such as glutamine and asparagine were essential to undergo cell dlvision leading to embryo formation from pollen grains of tobacco. Therefore, the results indicate that the amino acids required for embryo formation are supplied to pollen grains by cultured anthers. The present results revealed that the factors required for the process of pollen embryogenesis were successively provided to pollen grains by cultured anthers. It is concluded that satisfactory conditions of cultured anthers are the key points of the efficient formation of pollen embryos in anther culture of tobacco.

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As a part of a series of investigations on enlarging the genetic variability in commorl wheat by using alien cytoplasms, the effects of five fertile, alien cytoplasms on (1) performance and interplant variabllity of the parental lines, (2) heterosis and interplant variability of the F₁ generation, (3) performance and variability of the F₂ generation, and (4) heritability, in its broad sense, of agronomically important characters were studied by making reciprocal crosses between a euplasmic line of Triticum aestivum cv. Norin 61 (abbrev. N61) and a euplasmic and five alloplasmic lines of another cultivar, Norin 26 (N26). The alien cytoplasms used were of Aegilops longissima, Ae. squarrosa, Ae. vavilovii, Ae. speltoides and Ae. kotschyi, each representing the B, D, D2, S and Sv plasma types, respectively. All the seven parental lines. F₁ hybrids of 12 cross combinations, and 12 F₂ populations obtained by self-pollinatlon of the F₁'s were grown in the randomized blocks with four replications. The number of plants grown in each replication is lO, 4 and 50 for the parental, F₁ and F₂ lines, respectively. Thirteen characters were observed for all plants. The main results obtained are as follows ;

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The mode of inheritance of lipoxygenase-2 (L-2) in soybean seeds was determined from progeny of a cross between PI 86023 (L-2-less) and Suzuyutaka (normal) soybeans. Immunological and electrophoretic analyses of F₂ and F₃ seeds from the cross indicated that the absence of L-2 isozyme was due to a single allele recessive to an allele controlling the presence of the isozyme. The gene symbols. Lx2 and lx2 are assigned to the alleles for the presence and absence of L-2 isozyme, respectively. Electrophoretic analysis of a total of 474 F₂ seeds from the reclprocal crosses between PI 86023 (L-2-less) and Tohoku N0.74 (L-3-less) indicated that the Lx2 locus is independent of the Lx3 locus. Electrophoretic analysis of a total of 157 F₂ seeds from the cross between PI 86023 and a L-1 ?? -3-less double mutant line indicated that the Lx3 locus is independent of the Lx1 and Lx2 loci, respectively, being consistent with the no linkage between the Lx2 and Lx3 loci indicated by the analysis of F₂ seeds from the former reciprocal crosses. In this study, two types of double mutant seeds were identified that lacked both L-1 and L-3, and both L-2 and L-3 isozymes at the same time. However, no double mutant seeds were identified that lacked both L-1 and L-2 isozymes, so far. The L-1.L-3-less and L-2.L-3-less double mutant seeds germinated, grew and matured normally to produce F₃ seeds that lacked both L-1 and L-3, and both L-2 and L-3 isozymes, respectively.

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Seven soybean varieties, five from low latitude regions and two from Japan, were treated by various photoperiod ranging from 12 to 14 h. Number of days to flowering (NDF) as well as number of stem nodes (NSN) was increased exponentially with the increase of photoperiod. Thus, NDF and NSN at 12h photoperiod (N12) and increasing rate (IR) of NDF and NSN due to photoperiod were estimated by means of exponential regression. No substantial difference was found in IR between Japanese and low latitude adapted varieties. On the contrary, Japanese varieties exhibited smaller N12 than low latitude adapted varieties. Five soybean varieties, three from low latitude regions and two from Japan, were sown at the interval of 20 days from May 21 to August 9. NDF and NSN decreased as the plants were sown later. Daily natural photoperiod was averaged during the period from emergence to flowering for obtaining "mean photoperiod" for each variety and for each sowing date. NDF and NSN increased exponentially with the increase of the mean photoperiod. NDF and NSN under the mean photoperiod of 14 h (Nl4) and IR were estimated for each of the varieties. As in the case of the previous experiment, no substantial difference was found in IR between low latitude adapted varieties and Japanese ones, whereas low latitude adapted varieties exhibited larger N14 than Japanese varieties. The significance of IR and N12 or N14 in photoperiodic response was discussed in relation to the adaptability of soybean varieties. The larger N12 or N14 of low latltude adapted varletles observed in the present experiment indicated that adequate vegetative growth could be ensured in those varieties even under short photoperiod in low latitude regions.

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Interspecific hybrids between Nicotiana tabacum (=) and N.rustica can not be obtained by conventional crossing because of cross-incompatibilit.y. Two techniques, test-tube pollination and ovule culture, were combined to overcome cross-incompatible combination. Whole placentae with intact ovules of N.tabacum were pollinated in vitro by dusting pollen grains of N.rustica. Developed ovules were excised from the placentae and transferred to ovule culture. Finally, 12 hybrid plants were obtained by the combination of these two techniques. The hybrid plants were intermediate between their parents in their morphological appearance and had 48 chromosomes which were the additive sum of the haploid chromosomes of the parents. They failed to produce fertile pollen and were completely self-sterile. A fertile chromosome-doubled hybrid was obtained by colchicine treatment. From the results, it is considered that the combination of two techniques, test-tube pollination and ovule culture, is useful for overcoming cross-incompatibility between distantly related species.

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The upland rice variety Sensho has a high field resistance (quantitative resistance) to leaf blast that seems to be stable in response to the c.hanges in the pathogenicity of the blast fungus (Pyricularia oryzae CAv.). Some resistant cultivars of paddy rice have been developed using varieties derived from Sensho, but their resistance levels are not as high as that of Sensho. For further use of the high field resistance, it is necessary to study the mode of inheritance of the resistance. In the present study, linkage groups of the resistance genes of Sensho were studied using linkage testers with marker genes (Table 1). Leaf blast resistance and marker genes were investigated in F₃ lines derived from twelve crosses between the linkage testers and Sensho. Leaf blast resistance was estimated by nursery tests and marker genes were stuclied by using the phenotype of F₃ lines in paddy fields. F₃ lines were divided into three groups ; tester type group (example, la), segre-gating group (la/+) and Sensho type group (+). Linkage relation was tested by t-test for the difference of means of leaf blast score between the tester type group and the Sensho type group.

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Panicles of rice were cultured in a shaking liquid medium, and calli were obtained from individual anthers leading to the formation of a cell suspension. Transplantation of calli onto a regeneration medium after separating them according to their size revealed that the small calli induced many green spots and two green plantlets. The application of this technique may enable to avoid the laborious procedure involved in excised anther culture. The cell suspension in the AA medium, that contained amino acids as the sole nitrogen source, was finely dispersed and contained small cell aggregates that readily released a large number of protoplasts.

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