To clarify the taxonomical status and the geographical differentiation of pear cultivars in Japan, the occurrence of a species-specific flavonoid in leaf extracts was surveyed on 31 Pyrus species, 171 East Asian pear cultivars, and several uncultivated wild clones located in Japan and other places using paper chromatography. A brilliant yellow spot under UV Iight, with small Rf values 0.04 in BXA (n-BuOH/xylene/HOAc/H20 (6:4: 2:8)) and 0.02 in 2% HOAc (acetic acid) solvent was found in the extracts from the Ussurian pear (Pyrus ussuriensis Max.), native to northern China and northern-central Korea, from Iwateyamanashi (P.aromatica Nakai et Kikuchi) native to Tohoku region in Japan, and from their cultivars, but not from other East Asian Pyrus species, nor from European and Mediterranean species and their cultivars. This spot was confirmed to contain the flavonol aglycone (F-Ar), which seems to be a specific flavonold for the above species, and a useful chemotaxonomical marker in the genus Pyrus. In Japan, the occurrence of F-Ar was restricted to the old native cultivars originating in the Tohoku region and to the wild clones originating in the Kanto and Chubu regions and in Iwate prefecture. It was not contained in the old cultivars native to Kanto, Hokuriku and Kyushu regions. The distribution of cultivars and clones containing F-Ar nearly covered the native area of the Iwateyamanashi (P.aromatica). Most of the recent cultivars lacked F-Ar except for 5 cultivars including Nijisseik-i.

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The possibility of transferring sexually an incomplete chromosome complement between two uncrossable species was investigated. Pollen of Nicotiana tobacum were exposed to 137Cs gamma-rays (5-40kR) and were applied to stigmata of N.rustica. On the 6th or 7th day after the pollination, the ovules were detached from the placentae and were inoculated on solid medium. One hundred and fourteen mature hybrid plants were obtained through the ovule culture and they were classified into the following three groups on the basis of their morphological characteristics; (1) normal hybrids which were not distinguished from the hybrid plants obtained through crossing by unirradiated pollen, (2) anomalous hybrids which were cleglrly different from normal hybrids and (3) maternal hybrids which were not distinguished from the maternal parent. N.rustica and were fertile. More than 50 per cent of the obtained hybrid plants were the anomalous hybrids. The morphology of anomalous hybrids varied from that of haploid mother plants to that of normal hybrids and the chromosomes of these plants varied in number from 24 to 48. These results suggest that an incomplete chromosome complement of N.tabacum (n=24) is transferred into N.rustica (n=24) through the comblned techniques of crossing by irradiated pollen and in vitro culturing of crossed ovules.

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The A5 subunit is the most acidic subunit of soybean 11S globulin. The inheritance of A5 Subunit was studied by analyzing electrophoretically the crude 11S globullns in single seeds of F₁ and F₂ generations of four crosses. A part of these seeds were used to investigate the genetic relationships between A5 subunit and other characters, i, e., basic subunits, 11S globulin composition, 11S/7S ratio and seed protein content. The content of A5 Subunit was under the control of the alleles (Gl1, gl1) at one locus and highest in Gl1Gl1, about half of Gl1Gl1 in Gl1gl1 and zero in gl1gl1. The presence or absence of A5 Subunit and two specific basic subunits was entirely coordinated with each other, therefore, it was suggested that the structural genes coding for A5 subunit and two specific basic subunits were closely linked with each other to constitute Gl1 or the synthesis of these subunits was synchronously controlled by Gl1 and gl1. The presence of these subunits was accompanied by the most acidic 11S globulin molecule which is missing in gl1gl1. 11S/7S ratio was closely related to Gl1 gene dosage and highest in Gl1Gl1, intermediate in Gl1gl1 and lowest in gl1gl1. These results show that Gl1 is responsible for increasing heterogeniety of 11S globulin molecular species and raising 11S/7S ratio. There were no significant differences in protein content among three genotypes and 11S/7S ratio was not correlated with seed protein content so that these genes will have no effect on protein content and increasing 11S globulin may not decrease protein content.

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Three crosses of IRRI's varieties including IR 1905-81-3-1 as a common parent were genetically analyzed in the third generation for their blast resistance with Philippine and Japanese fungus strains. When two Philippine fungus strains were employed for inoculation, the segregations were very complicated. In the cross. IR 1905-81-3-1 × IR 32, the F₃ segregation was explained by two minor genes in P1, one of which had a majorgenic action under some conditions, and one minor gene in P2 controlling a weak resistance. In the second cross. IR 1905-81-3-1 × IR 2071-586-5-6-3, and the third. IR 1905-81-3-1 × IR 36, segregations differing from the first cross were observed although a common parent in the cross and a common fungus strain for inoculation were used. In the second and third crosses, recessive complementary genes were suggested to control resistance of a more reslstant variety, IR 1905-81-3-1. When the second Philippine fungus strain was used, the observed segregation was different from one for the first strain in the first cross. This difference was considered to be due to environmental variation rather than the difference of fungus strains used. After all, it was thought that the resistance of IR 1905-81-3-1 was controlled by three or more genes of which the action greatly varied with the change of environmental conditions and that other varieties used as parents of the crosses had one gene controlling a weak resistance.

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Studies were undertaken to locate the gene Bph 1 on the linkage map of rice. The trisomic lines obtained from Kyushu University were crossed with 'Kanto PL1' or 'Kanto PL4', which were the parental lines of japonica type rice resistant to the brown planthopper, and had Bph 1 derived from 'Mudgo'. Segregation ratios observed in the F₂ generation of four crosses with trisomic A, C, G and H proved to be of the disomic type. But segregation ratio in the cross with trisomic E carrying the extra chomosome of 11th did not fit a disomic ratio. The 11th chromosome corresponds to the linkage group II. Among marker genes belonging to the linkage group II, lg and d-11 are independent of Bph 1, and lg and Pl-1 are also independent of bph2(allelic to, or closely linked with Bph 1). However, it was found that bph2 Iinked with d-2 of the linkage group II at the recombination value of 39.4%

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Degrees of sexuality in lowly and highly sexual plants of guineagratss which were isolated by progeny tests in the previous paper of the authors, were investigated by using the simplified embryo sac analysis, and compared with degrees of sexuality by frequency of off-type plants in progenies. In embryo sac analysis, ovules were classified into sexual or apomictic reproduction to detect the type of embryo sacs. Sexual embryo sac was 8-nucleate, and aposporous one was 4-nucleate. As ovules examined kept their original forms intact in pistils, reproductive behavior in polyembryonic ovules was easily identifled by determining the dominant embryo sac in multiple ones. Highly sexual diploid plants were revealed to be completely sexual based upon the embryo sac type. All ovules had single sexual embryo sacs excluding several sterile ones. Highly sexual tetraploid plant, N68/96-8, was also identified to be completely sexual, and its offsprings after open-pollination were segregated in degrees of sexuality. Five out of 10 offsprings were completely sexual, one was obligate apomictic, and the other four were facultative apomictic. Two lowly sexual plants, N68/84-1 and 73/61-9, and their offsprings after self-and open-pollination, were shown to have low frequencies of sexual embryo sacs except N68/84-1 which had rather higher rate of sexual embryo sacs. No plants with high degrees of sexuality were segregated in their offsprings. Both degrees of sexuaiity by embryo sac analysis and progeny test, agreed well excluding degrees in a few facultative apomicts. This analysis was appeared to provide more accurate estimation of degree of sexuallty. Complete sexuality observed in this study was recognized to be useful for producing controlled hybrid plants in sexual X apomictic cross in the first procedure of hybridization breeding in this apomictic grass.

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Effects of pala-fluorophenylalanine (PFP), an amino acid analogue, on callus induction and somatic chromosome reduction were investigated in strawberry plants (2n=56). High concentrations of PEP had an inhibitory effect on callus growth and RD50 was calculated to be 30mg/l for callus induction. Cytological study revealed that several plants which were regenerated from the calluses of several plant organs cultured on the medium containing PFP had the chromosome number of 2n=49. The mechanism of this chemical agent underlying chromosome reduction was also discussed.

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Two experiments were carried out to investigate the mode of inheritance of field resistance (quantitative resistance) to panicle blast in rice plants. The first experiment is the analysis of resistance in F₂ progenies of two sets of diallel crosses. The second is the analysis of resistance in F₃ and F₄ lines derived from the cross of resistant and susceptible parents. In addition to these experiments, resistance of 22 varieties including parental varieties used in the two experiments was evaluated. Materials were subjected to severe natural epiphytotics of panicle blast with races 003 and 007 of blast fungus, and their resistance was evaluated with eleven scores (Table 1). All varieties used carry no major genes for true resistance (qualitative resistance) effective to race 003 or 007, and belong to an early-maturing variety group at Omagari, Akita. First, in a diallel cross among four varieties, mean scores of resistance to panicle blast in F₂ populations were near the values of midparents, and F₂ populations from reciprocal crosses showed no differences in mean scores (Fig. 1). The result indicates the presence of additive effects of genes and no cytoplasmic effects.

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Using hematoxylin staininba method (Table 1), 125 wheat varieties registered in Japan and their 80 ancestral varieties were examined for their aluminum tolerance (Tables 2 and 3). There were no highly tolerant (Score 1) or highly susceptible (Score 9) varieties in the Japanese registered varieties as Shown in Table 2. Among these registered varieties, however, thirteen have fairly high tolerant ability (Score 3). From their pedigree data, it was proved that their Al tolerance was derived from an American variety "Turkey Red II" and/or Japanese local variety "Shiro Sanjaku". Most of these tolerant registered varieties were originated from the northern Ando soil area (Fig.1). Almost all of Japanese field soils are acidic and more or less aluminous, neverthless 88.0% of the reglstered vanetles have Score 5 (Intermedrate) and Score 7 (Susceptible), and the frequency of susceptible varieties have been increasing recently (Fig.2). These results suggest that aluminum tolerance is not a serious problem to the Japanese wheat breeding, because Japanese field soils had been ameriolated. The tolerant (Score 3) varieties were also selected for earliness, dwarfness and highly yielding ability as a result of general soil acidic conditions when soil acidity of their breeding nursery has not yet been improved.

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