Caffeine, flavanol and amino acid contents in young leaves of first flush shoots of hybrids and species of section Dubiae in the genus Camellia were investigated. Based on these results, principal component anafysis was performed. All clones of hybrid combinations between C.sinensis and other species such as C.sasanqua and C.japonica contained caffeine, ECG (epicatechin gallate). EGCG (epigallocatechin gallate) and theanine. Since these compounds were not detected in C.sasanqua and C.japonica, they were considered to be suitable chemical markers for hybrids between a species of section Thea and a species of other sections. In chromatographic studies of flavanols, both C, vernalis and C.hiemalis were found to contain high EC (epicatechin) amounts as well as four unidentified components which were detected in C.sasanqua and its hybrids. Therefore, both speciescould be considered to be hybrids resulting from crosses between C.sasanqua and a species of section Calnellia. Chromatogram of C.miyagii and C.tenuiflora did not show these peaks, and there was significant and positive correlation between the flavanol pattern of the latter species and that of C.oleifera. In general, flavanol chromatograms of C.wabisuke with the exception of cv. 'Sukiya' were similar to those of species of the section Camellia. Furthermore, caffeine, EGCG and theanine were not detected in the clones of C.wabisuke. Thus, phytochemically it was difficult to consider that C.wabisuke was related to C.sinensis.

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The presence of polymorphism for α-amylase in germinating barley seeds and in malt in 130 barley varieties was examined by means of isoelectric-focusing gel electrophoresis. These varietles were classified into three types according to the banding patterns of the zymograms that were constantly obtained both in germinating seeds and in malt irrespective of pH of the buffer. Most of Japanese two-rowed varieties have specific banding patterns of the zymograms, i. e. they fall into type-1 and type-3, whereas almost all foreign two-rowed varieties fall into type-2 and type-3. This classificatlon does not agree with the classification based on agar gel zone electrophoresis.

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A mutant with a reduced culm number was found in M₂ population of AC-3 (a strain regenerated from A-5 Akamuro by anther culture) after gamma-ray irradiation of dry seeds. In F₂ population of the crossing between the mutant line, N-133 and the original strain, A-5, it was demonstrated that a single recessive gene, rcn is responslble for the reduced culm number type. A pleiotropic effect showing dwarfness was expressed although the seed fertility was unaffected. In the linkage analysis, it was found that rcn was linked with the genes belonging to the first linkage group such as wx (glutinous endosperm) and C (Chromogen for anthocyanin) in the order of wx-C-rcn. In addition, rcn was epistatic to the dwarf genes, d-2 (ebisu dwarf), d-3, d-4, d-5 (triplicate genes for bunketsu waito) and d-10 (toyohikari-bunwai). As for the relation with d-6 (ebisumochi dwarf), a non-parental dwarf type with a reduced culm number and shorter lower (below the second) internodes occurred as a double recessive genotype. The character expression of the mutant gene, rcn was remarkably affected. by the temperature conditlons during the growth period. Plant height and culm number of the mutant recovered to nearly normal when grown in a plastic house with the application of nitrogen. Since the plant height and culm number were retarded by the treatment with cold water (15°C), it was demonstrated that the gene expression was conditioned by the low temperature.

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Distorted segregations of A (Anthocyanin activator), Pn (Purple node) and d-18n, (hosetsu-waisei) in the third linkage group (Chromosome 3) were detected in F₂ populations of the crosses between H-50 (A, Pn+, lax+, d-18h+) and linkage testers. Reciprocal backcrossings indicated that the excess segregation of Ad or A+ is caused by a gametophyte gene (ga-7(t)), and it was assumed that the shortage segregation of Pn+ is also due to ga-7(t) because of the linkage relation between A and Pn. Further, it was deduced that the shortage segregation of d-18h depends on a gametophyte gene through the backcrossing. Since H-50 carried A and d-18h+, it was obvious that ga-7(t) and the gametophyte gene linked with d-18h are locilted on different loci. In F₂ population in which the distorted segregation of A+ was observed, the segregation of lax indicated a good fitness to the monogenic segregation ratio. Therefore, it was apparent that ga-7(t) is not identical with ga-8. Further, it was estimated that d-18h is arranged in the sequence of lax-A-d-18h, and the gametophyte gene linked with d-18h and ga-8 are located on different loci. Thus, the gametophyte gene linked with d-18h was designated as ga-9. From these results, it was concluded that ga-7 and ga-9 are new gametophyte genes in the third linkage group (Chromosome 3), and the order of the two gametophyte genes was ga-9-d-18h, Pn-A -ga-7-lax.

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The inheritance of rice (Oryza sativa L.) panicle types classlfied by the nodal distri-bution pattern of the number of spikelets on the secondary rachis branches was investigated using four varieties belonbaing to different ecospecies. Reimei (a modern cultivar from Japan, japonica) and Stirpe 136 Anthocyane (a large grain variety from Italy) had a large number of spikelets on their secondary rachis branches at the lower rachis nodes and an extremely small number at the upper rachls nodes. Mao-zu-tao (an old cultivar from China, indica) had a large number of spikelets on its secondary rachls branches at the upper rachis nodes ancl a small number at the lower rachis nodes. Panbila (a modern cultivar from U.S. A, , inclica) had a large number of spikelets on the secondary rachis branches at both the lower and upper rachis nodes. The number of spikelets on the primary rachis branch of each rachis node was about 6.0 and showed little change In the parents, t.he F₁ and F₂ generations, indicating the existence of genetical similarity among the parents. In the Mao-zu-tao x Reimei cross, the number of spikelets on the secondary rachis branches at the upper rachis nodes was controlled by four independent dominant genes (Ssp-1, Ssp-2, Ssp-3 and Ssp-4) and that at the lower rachis nodes by a suppressor gene (Su-1). The Su-1 gene was closely linked with Ssp-3 and controlled by Ssp-1, Ssp-2 and Ssp-3. In the Panbila x Stirpe 136 Anthocyane cross, the mode of inheritance of the n.odal distribution pattern of the number of spikelets on the secondary rachis branches ¥vas very s'imi]ar to that of the Mao-zu-tao x Reimei cross. However, in this case, three inclependent clominant genes (Ssp-1. Ssp-2 and Ssp-3) controllecl the number of spikelets on the secondary rachis branches at the upper rachis nodes. A suppressor (Su-2) and a activator (Act) genes, which were closely linked with the Ssp-1 and Ssp-3 genes, respectively, controlled the number of spikelets on the secondary rachis branches at the lower rachis nodes. The Su-1. Su-2 and Act genes were considered to be the regulator genes. It was estimated that they would be stimulated by the Ssp genes and control the structural genes which would express the initiation and barowth of the secondary spikelets at the lower rachis nodes.

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Studies were carried out to identify a new index for the selection of tuber yield in sweet potato breeding. The K2O/N ratio in tubers showed a positive correlation with fresh and dry tuber yield, and a negative correlation with nitrogen content in tubers. Nitrogen content in tubers showed a negative correlation with tuber and starch yield. Dry matter and starch content in tubers showed a negatlve correlation with the K2O content in tubers. Estimate of "heritabllity in the broad sense" of dry matter content, K2O and nitrogen content and K2O/N ratio averaged 89.2, 68.8, 65.9 and 63.3 percent, respectively, in a population of 267 first year clones selected from 711 clones of seedlings derived from polycross seeds. These characters in the 1st year clones were closely related to those of the second year clones. Phenotypic variance in these characters was based on genetic variance. In the seedlings from polycross seeds, the clones selected according to a high K20/N ratio and low nitrogen content induced high tuber yield in the 2nd vear clones. It is concluded that the K20/N ratio and nitrogen content in tubers could be a useful selection index for tuber yield in sweet potato breeding.

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The process of embryogenic induction in pollen grains of tobacco was investigated through direct pollen culture. Pollen grains at the late unicellular to middle bicellular stages could develop into seedlings through a process of embryogenesis when they were cultured in sucrose-free medium for several days and then transferred into Nitsch's liquid medium containing sucrose, as described by GHANDIMATHI (1982) and IMAMURA et al. (1982). Based on microscopic observations of cultured pollen grains and experiments where 3H-thymidine was incorporated into the pollen grains, it was revealed that pollen grains accumulated starch granules resulting in pollen germination and that DNA was synthesized only in the generative nucleus, sugbaesting that they continued their gametophytic development in the medium containing sucrose. On the other hand the gametophytic development was markedly suppressed in the sucrose free-medium. These finidings indicate that the initial event of embryogenic induction is the suppression of the gametophytic development of the pollen grains and that embryogenic induction proceeds successfully in the absence of sucrose in the medium. Furthermore, the results of 3H-thymidine incorpora-tion showed that DNA synthesis in the vegetative nucleus, which was assumed to be the DNA synthesis leading to pollen embryogenesis, occurred soon after the suppression of the gametophytic development caused by the absence of sucrose. Since cultured cells generally do not undergo the phase of DNA synthesis when starved of sugar, it is inferred that pollen grains of tobacco have the inherent ability to synthesize DNA in the absence of sugar. It is concluded that the process of embryogenic induction in pollen embryogenesis consists of two phases, namely, the suppression of the gametophytic development caused by sugar starvation and DNA synthesis leading to pollen embryoogenesis which proceeds depending on the inherent properties of pollen grains.

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In wheat a successful embryo culture technique is essential for the development of haploid plants following the intergeneric cross with tetraploid Hordeum bulbosum L. To investigate the optimum procedure, embryo development of wheat pollinated with H.bulbosum and plant regeneration from cultured embryos were studied. Immature embryos with ca. 1.4 mm long at two weeks after pollination developed into haploid plants at a very high frequency. When the embryos with overgrown scutellums were excised after three weeks and later, frequencies of regenerated plants abruptly decreased to 20-30% of cultured embryos. One of the regenerated plants proved to be an aneuhaploid having 22 chromosomes. These results suggest that the developmental stage of immature embryo at the time of excision is critical with respect to plant regeneration.

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Varietal differences in the number of stigma-hairs and the effect of cold treatment oll the character were studiecl in several Japanese paddy rice varieties ancl in the F₂ of the hybrids between the vafieties Kinmaze and Somewake. ' As it ¥vas difficult td count the number of stigma-hairs uncler a microscope, stigmas wer'e' reconstructed from serial transverse section. The length of both arither and stigma was less by ten percent tharL that 0L the control aLter cold treatment (day temperature 17'C and night temperature 12'C for 5 days) at the meiotic stage. Two fl6ral characters (anther ancl stigma length) of the control and plants subjected to the cold treatment were both negatively correlated with the sterility index, arcsin /percent of sterility

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The days to heading of 93 native rice cultivars collected from various locations in Japan weret examined under a short-day (30°C phytotoron, in winter, natural day-length), and a long-day (a paddy field, in summer, natural day-length and temperature) condition. From the clata, varietal variations in the periods of basic vegetative phase (BVP) as shown, by days to heading in shortday condition and in photosensitive phase (PSP) as shown by the difference in days to heading between longday and shortday conclitions were surveyed, so as to learn about the mode of differentiation of early-maturing cultivars in Japan. The cultivars tested were divisible into two groups with a long (75-90r days) and a short (38-75 days) BVP. Among the cultivars with short BVPs, the distribution of PSP, varying from O to 72 days, was trimodal. Among those from areas north of 32N in latitude, PSP decreasecl with increasing latitude of collection site. But no cor-relation between PSP and latitude was found among cultivars from the southwest islands. The early-maturing cultivars (with short BVP and short PSP) distributed throughout Japan alt*nough they were infrequent. The pattern of distribution of native rice cultivars vvith varying BVP and PSP periods seems to reflect the variations in environrnental condition anc'i cropping system under which they have been cultivated so far.

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The combination of 2 techniques, i, e., pollination after the destruction of chromosomes in pollen grains with ionizing radiations and in vitro culture of crossed ovules, was applied to interspecific hybridization between N.repanda and N. tabacum in order to investigate the possibility of overcoming hybrid inviability in the cross-combinations. By using these techniques, it became possible to obtain aneuploid hybrids, which had never been reported previously.

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