An ovule culture method was used to produce interspecific hybrids between kura clover (Trifolium ambiguum M. BIEB.) and white clover (Trifolium repens L.). Culture of fertilized ovules from the cross hexaploid T.ammguum (2n=6X=48)×diploid T.repens (2n=32) began 5 days after pollination. After 15∼20 days in culture, hybrid ovules were transferred to a fresh medium, where development into plants occurred. Four interspecific hybrid plants were established in soil. One of these plants has produced flowers. The morphology of the plant was generally intermediate. Root tip cells of the plant possessed the expected somatic chromosome number of 40. The plant possessed the major bands of leaf peroxidase and esterase isozymes derived from the staminate parent as well as from the pistillate parent. A virus assay on Chenopodium amaranticolor indicated that the plant was virus-free. However, it was highly sterile with the absence of viable pollen. The ovule culture method represents the successful production of Trifolium interspecific hybrids via some form of embryo rescue. It appears that this technique can be applied to other interspecific hybrid combinations in the Trifoliutn species.

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Influence of cycloheximide and 6-methylpurine on germination and synthesis of protein and nucleic acids was studied in heterotic F₁ hybrid (Oh545×W22), non-heterotic F₁ hybrid (Oh545xOh45) and their parental inbred lines of maize. Each inhibitor-treatment differentially reduced germination ; the extent of reduction was the least in heterotic F₁ hybrid and the most in non-heterotic F₁ hybrid. In the presence of each inhibitor, the amount of incorporation of 3H-leucine into protein, 3H-tymidine into DNA and 3H-uridine into RNA, was greater in heterotic F₁ hybrid than its parental inbreds. On the other hand, the amount of 3H-leucine incorporated in non-heterotic F₁ hybrid under cycloheximide treatment was much the same as that of maternal parent. It is concluded that higher tolerance of heterotic F₁ hybrid to exogenous inhibitors is due to more active synthesis of protein and nucleic acids in embryonic cells.

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This paper describes the relationships between embryo and endosperm weights and seedling growth parameters, the characteristics of seedling growth and the relationships of the seedling growth parameters with alpha-amylase activity in 36 rice cultivars belonging to three ecospecies, japonica, indica and javanica. The embryo weight was positively and significantly correlated with the endosperm weight in the javanicas, but not in the japonicas and indicas. The entries with the heavier embryo and endosperm weights developed larger top dry weights (TDWs) and leaf areas (LAs) in the javanicas, but not in the japonicas and indicas. Four cultivar groups were classified on a plane defined by the first and second principal components for the seedling growth parameters at different growth or sampling stages of the three ecospecies. The factor loadings of the growth parameters, i. e. top dry weight (TDW), leaf area (LA), relative growth rate (RGR), net assimilation rate (NAR) and top dry weight : leaf area ratio (TLR) varied with the growth or sampling stages of the three ecospecies. The first and second principal components included the different growth parameters depending on the growth or samplin*" stages of the three ecospecies. However, the parent-offspring cultivars and the brewer's cultivars were found to belong to the same cultivar groups throughout the sampling or growth stages. Furthermore, some of the cultivar groups or cultivars developed high TDWs through the increase of RGRS and NARS together with the increase of LAS and TLRS at the different sampling or growth stages in the three ecospecies except for the japonicas at the second sampling or growth stage. In the laboratory experiments, the alpha-amylase activity was positively and significantly correlated with the shoot and root fresh weights 3 and 6 days after seed incubation in the japonicas and javanicas, and only nine days after seed incubation in the indicas. However, the laboratory performance of integrated alpha-amylase activity during nine days was not correlated with the glasshouse performance of the TDW and RGR in the three ecospecies. Instead, the principal component analyses indicated that one cultivar group displayed a high integrated alpha-amylase activity together with a high TDW 10 days after sowing and a high RGR at this stage in the japonicas and indicas. However, the cultivar groups with a high integrated alpha-amylase activity and RGR exhibited a low TDW in the javanicas.

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Cytoplasmic effects of the four Aegilops species, i.e., Ae.squarrosa, Ae.kotschyi, Ae.speltoides and Ae.longissima, on the genetic variability of agronomic characters of wheat were investi**ated using a total of 460 F₃ lines which were randomly derived from the cross combinations of allo- and euplasmic Norin 26 with euplasmic Norin 61. It was observed, coincidently with the trend observed in the F₂ populations (TSUNEWAKI et al. 1985), that cytoplasm of Ae.kotschyi caused the most prominent effect. The cytoplasm increased, statistically significantly and/or consistently with the F₂ result, the genetic variability of the seven out of ten characters examined. Cytoplasm of Ae.speltoides showed the second most appreciable effect, enlarging the genetic variability of the length of internodes, culm and spike. Cytoplasmic effects of Ae.squarrosa and Ae.longissima were neither distinct nor desirable. The principal component analysis revealed that none of the alien cytoplasms tested substantially modified the phase or structure of character association, though they more or less changed the genetic variability of individual characters. Cytoplasms with a larger genetic distance from wheat cytoplasm (TSUNEWAKI 1980) caused a wider range of effects, suggesting that new and desirable nucleo-cytoplasmic interactions may occur in a combination of relatively distantly related cytoplasmic and nuclear genomes rather than closely related ones.

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Correlations among resistances to the bacterial groups I to V and the phenol reaction were investigated, and an effective method of selection for, the resistance was presented. The analysis of linkage relation showed that three loci, Xa-1, Xa-kg and Ph, were closely linked with one another. Experimental results indicated that the quantitative resistance to the bacterial groups II, III and IV was correlated with the qualitative resistance to the bacterial group I, which is controlled by Xa-1h, and accordingly the degree of attack by the bacterial groups II, III and IV was inversely proportional to the dosage of the genes controlling the qualitative resistance. This finding could also be applied to the correlation between the qualitative resistance to the bacterial group V, which is controlled by Xa-kgh or the phenol reaction, which is controlled by Ph, and the quantitative resistance to the bacterial groups Il, III and IV. Experimental results showed that the quantitative resistance derived from IR28 was also effective against the bacterial groups I and V as well as the groups II, III and IV. Selection experiments in the F₂ generation revealed that the selection based on the combination of resistance to the bacterial group III and the phenol reaction was the most suitable method for efficient selection of the resistance originating from IR28, and it was sugbaested that this selection made it possible to omit the inoculation of bacterial groups I, II, IV and V. It was further suggested that the above conclusions on selection methods could also be applied to a hybrid population derived from the cross having IR 29 as a resistance-donor parent.

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Agronomic performances of the male sterile tobacco (Nicotiana tabacum cv. Consolation 402) obtained by protoplast fusion between Consolation 402 and X-irradiated N.debneyi were evaluated. A majority of the male sterile lines in the BC1 generation exhibited almost equivalent field performances to the selfed lines of normal fertile Consolation 402, and stable performances of these male sterile lines were also recorded in the following generation. In the BCI generation, however, there were a few lines showing late maturity and smaller stature. These lines did not carry a specific type of chloroplast genom.e, thus suggesting little participation of chloroplast genomes in the observed deviations. Also, such deviated traits appeared to be recovered in the subsequent generations of backcrosses. This indicates that the deviated traits are resulted from mutational events in the nuclear genome during in vitro culture. None of the male sterile lines segregeted any fertile plants. The observed stability of fusion-derived male sterile tobacco both in agronomic traits and in the male sterility indicates that the protoplast fusion method can be incorporated into a practical breeding program as an alternative for obtalning male sterile tobacco.

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In cereal crops uniformity of heading time of the tillers within a variety, or synchrony of heading, is necessary for simultaneous ripening. On the other hand, to avoid the environmental stress at anthesis, excessive synchrony of heading is not desirable. Thus, a proper level of synchrony in a variety ought to be achieved by breeding. In this study synchrony of heading in 60 Japanese rice varieties (Table 1) has been analysed in relation to their earliness and panicle number. However some of the very early varieties, designated as 'VE' in Table 1, were excluded from statistical analysis, because those main culms showed unexpectedly early heading in comparison with the other tillers in respective plants (Figure 2). Four or eight plants of each variety, grown in pots were placed in a glasshouse, and synchrony of heading was evaluated with these materials. Five plants of each variety were also grown in a paddy field to investigate their agronomic traits. Regression coefflcient of heading date of each tiller on the order of heading, which had been deflned as the synchrony index by PARODA (1971) was not a suitable indicator of the synchrony of heading when the number of panicles showed significant variations (Table 3). Therefore, synchrony of heading was expressed by the standard deviation of heading date of individual tillers within each plant.

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A new technique of ovary culture was applied in Lilium, resulting in the formation of a lot number of plantlets in vitro. Ovaries of Lilium formosanum WALLACE, sampled 20 days after self-pollination, were sliced into disks 2mm thick. They were inoculated on 32 kinds of modified MS agar media. The arrangement of those media was based on the L 32 table of orthogonal arrays, and 15 medium elements with 2 levels each, including pH, sucrose, major salts, minor salts, vitamins and several hormones, were combined with one another. Ovules grew well and became recognizable as seeds 40 or 50 days after inoculation. They germinated successively in the test tubes. Higher pH value (6.3) and sucrose concentration (8%) gave better results than lower ones, and the use of IAA (1 ppm) inhibited seed maturation. Standard concentration of the major salts was preferable to a lower one, while the inhibitory effect of hormones tended to decrease 170 days after inoculation.

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Interspecific crosses involving the yellow-flowered Camellia chrysantha (diploid) have proved unsuccessful in the establishment of hybrid plants. In our hybridization program, five controlled pollinations between C.vietnamensis (hexaploid) and C. chrysantha successfully produced two mature capsules which contained three viable seeds. Mature cotyledons of these viable seeds cultured in vitro proliferated slowly for approximately six months on Murashige and Skoog (MS) medium containing 3.0mg/l benzyl-adenine and 1.0mg/l α naphthalene acetic acid. After they were transplanted on MS medium supplemented with 10% coconut milk and 1mg/l gibberelin(GA3), the whole surface of the cotyledons formed numerous yellowish or greenish organs. Only 4.3% (6/138) of the generated buds formed shoots longer than 5cm with leaf development and grew up to plantlets. Karyomorphological characteristics in root meristematic cells indicated that these new plants (tetraploid) were true hybrid individuals between C.vietnalnensis and C.chrysantha.

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