A high content of linolenic acid lcads to reduction of keeping quality and frying stability of cooking oil. The present study was conducted to obtain a further reduction of linolenic acid in soybean [Glycine max (L.) Merr.] oil by re-irradiation of M-5 and determine its genetic system. M-5 is a mutant with 4.5% Iinolenic acid content, derived from the cultivar Bay (8.0% Iinolenic acid). A seed lot from line M-5 was treated with X-ray irradiation and M₂ plants were obtained from randomly selected seeds of Ml plants. The M₂ plants were screened for reduced linolenic acid. One plant was found with 3.0% Iinolenic acid content and was named MS382. The M₃ and M₄ generations of this line proved that the character was fixed and significantly lower than the M-5 control. For inheritance studies, MS382 was reciprocally crossed with M-5(fan) and LOLL[fanfanx^a, a recombinant of M-5 (fan)× M24 (fanx^a)]. The F₂ segregation ratio and the segregation of F₃ seeds from F₂ plants of MS382×M-5 indicated that reduced linolenic acid in MS382 was conbindly controlled by fan (M-5) and an additional gene. To determine if this additional gene was similar with the fanxa gene in LOLL, F₂ seeds and F₃ seeds from each F₂ plant of MS382×LOLL were evaluated. No transgressive segregation for linolenic acid was found in this cross, indicating the genes for reduced linolenic acid content in MS382 and LOLL were identical. However, the mutant MS382 was developed by re-irradiation which indicates the practicability of this technique to develop new gene for further reduction of linolenic acid in soybean oil.

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Our previous work on the induction of secondary dormancy at a lower germination temperature showed that evaluation of germinability at a lower temperature was much affected by the secondary dormancy. Here, the effect of temperatures during the ripening stage on the degree of induction of secondary dormancy was investigated for rice seed of two Indica cultivars, Kasalath and Dhenga. In both cultivars, the germination percentage of the seeds ripened under the high temperature condition of 32°C/27°C was lower than that of the seeds under the control condition of 25°C /19°C after low temperature treatment at 15°C for 14 days. In the continued germination test conducted at 25°C for 7 days, the germination percentage was not increased for the seed from both conditions with a lower percentage for the seeds from the high ripening temperature and a higher percentage for the seeds from the control condition. The non-germinated seeds were considered to be induced into secondary dormancy. Thus, the seeds which ripened at a high temperature showed a comparatively deep secondary dormancy. The effect of the temperature at the ripening stage on the wakening of secondary dormancy was also investigated by storing the seed for eight months at 30°C. The germinability of the seeds from the high temperature condition was lower than that of the seeds from the control condition. The difference was gradually decreased in the course of storage. The temperature during the ripening period of seeds affected the wakening of secondary dormancy.

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We determined the chromosomal location of a green rice leafhopper(GRLH) resistance gene, Grh1, using restriction fragment length polymorphism (RFLP) markers. First, we determined the graphical genotype of Norin-PL2, to which Grh1 was introgressed from an indica variety, Pe-bi-hun, and identified four Pe-bi-hun-derived chronrosonral segments on chromosomes 5, 11 and 12. Then, we examined the linkages between Grh1 and RFLP markers located in the four introgressed segments using 108 B₁F₁ plants. The results indicated that the resistance gene Grh1 was located on chromosome 5 and linked to RFLP markers R566, C309, R2558, XNpb260.

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Variation of the vascular bundle system in 83 Asian rice cultivars and its usefulness in the distinction of the 3 types, indica, tropical-japonica and temperate-japonica were investigated. The 83 cultivars were classified into 46 indica and 37japonica cultivars by the discriminant function, D₁, based on the data of phenol reaction, sensitivity to KCI0₃ and apiculus hair length. Next, the 37japonica cultivars were subdivided into 8 tropical- and 29 temperate-japonica using the score of D₂ which was computed from the ratio of length to width of the kernel, alkali digestibility and mesocotyl length. The number of vascular hundles(Vb) in the peduncle and the ratio of Vb to rachis branches(Rb)(V/R ratio) differed among the 3 types; the indica and tropical-japonica cultivars had more Vbs and showed a higher V/R ratio than the temperate-japonica cultivars. Then, the new discriminant function(D₃) for identification of indica and japonica and D₄ for that of tropical- and temperate-japonica were calculated based on Vb, Rb and V/R ratio. D₃ and D₄ improved the precision of distinguishing indica from japonica, and tropical- from temperate-japonica; the probability of misclassification decreased from 1.4%(D₁) to 0.7%(D₃), and from 4.8%(D₂) to 0.4%(D₄), respectively. In conclusion, the variation of vascular bundle system was a highly useful character for identification of Asian rice cultivars.

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We developed a rice (Oryza sativa) transformation system using silicon carbide whiskers (SCW). The scutellar tissues of rice embryos obtained from mature seeds were vortexed in liquid medium containing plasmid DNA and SCW. The embryos treated with a plasmid DNA, pAct1-F containing the β-glucuronidase (gusA) gene, transiently expressed GUS activity at a mean number of 302 spots per 250 mg sample (around 20 embryos) in optimal conditions for DNA delivery. On the other hand, the bialaphos-resistant calli were obtained from embryos treated with two plasmid DNAs, pAct1-F and pDM302 containing the bar gene, of which product confers resistance to bialaphos. Some of the resistant calli also expressed GUS activity. Fertile transgenic rice plants were regenerated from them. The integration and inheritance of bar gene were confirmed by Southern analysis of R₀ and R₁ plants.

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The morphological characters of a dwarf common buckwheat line, G410, its dwarf stability under different growth conditions and mode of inheritance were investigated. Dwarfism of G410 is the result of reduction in length in the first four internodes, especiaHy in the second- and the third internodes from the soil. The other internodes and organs were not reduced in size. Therefore, G410 shows the brachysm type dwarfism, which is valuable for both root lodging- and stem lodging resistance. Although buckwheat is sensitive to growth conditions and its stem elongates longer under long day or high nitrogen conditions, the morphological characters of G410 were unaffected by seeding date, planting density and nitrogen conditions. F₁ plants of G410 crossed with a normal variety, Botan-soba, appeared intermediate and segregation ratios in the F₂ and BC₁F₁ generations fitted a single gene model. Therefore, dwarfism of G410 was controlled by a single incompletely dominant gene, probably which is a new gene because all dwarfing genes reported previously are recessive. Under this inheritance system it is possible to distinguish genotypes by phenotype and to select dwarf homozygotes. These results indicate that G410 is a material worth further investigation for breeding lodging resistance in common buckwheat.

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The rice plant Oryza sativa L. has four separate loci coding for fructose-1, 6-bisphosphate aldolase (aldolase). One codes for chloroplast aldolase (AldP), and the other three for the cytoplasmic counterparts, AldC-a, AldC-1, and AldC-2. In the present study, we examined the occurrence of structural variations in the aldolase gene regions among different ecotypes and cultivars of rice. Southern blot hybridization showed that the structure of the AldP and AldC-1 gene regions did not differ among eight rice cultivars examined here, based on restriction fragment length polymorphism. However, the AldC-a and AldC-2 Ioci exhibited four and two types of variations, respectively. The variations enabled to distinguish five different groups of rice cultivars including so-called red, green and black rice in addition to japonica and indica cultivars. Thus, these variant gene regions may be used as markers for the classification of rice cultivars.

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It is generally recognized that the pollen-ovule (P/O) ratio is correlated with the breeding system of plant species; the higher the P/O ratio, the lower the autogamy among species. Evaluation of breeding systems before flowering is useful for the selection of predominantly autogamous breeding materials from heterogeneous incomplete autogamous plants. We analyzed the correlation between the hreeding system and P/O ratio in a Thai mustard cv. Knock out with low autofertility (AF). Automatic self-pollination ability (ASPA) ranged from 29.4% to 52.8%, and ASPA of a line S₆-3 was significantly higher than in the original population. Among 8 S₆ Iines derived from one S₀ Plant by recurrent seed growing after automatic self-pollination, we observed significant negative linear regression equations between AF and the P/O ratio as well as between ASPA and the P/O ratio. These results indicate that the higher AF, particularly ASPA, the lower the P/O ratio even within the selected lines in a local mustard cultivar. Consequently, evaluation of the P/O ratio in flower buds before flowering is a promising method for the selection of breeding materials with high ASPA from hetero-geneous incomplete autogamous or allogamous plants with a similar self-compatibility.

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Sweet potato is one of the ten most important crops for human consumption in the world. Recently, due to the detection of radical scavenging and antioxidative properties, it has been considered that commercial varieties of purple-fleshed sweet potato may play a role in the preservation of health in hunran beings. In this study, anthocyanin content and composition of 19 purple-fleshed sweet potato clones were investigated to identify the genetic factors responsible for the variation in paste color ranging from reddish purple to bluish purple. The paste color was evaluated based on the color reflectance value L* (related to brightness) and b*/a* ratio (index for red blue color). Sweet potato clones were classified into two groups based on the b*/a* ratio of the paste:(1) a blue dominant group with a ratio below -1.4, and (2) a red- dominant group with a ratio above -1.1. Analysis of the anthocyanins extracted from steamed roots by spectrophotometry and high-performance liquid chromatography (HPLC) revealed considerable differences in the color value and anthocyanin composition among the clones. Based on the peonidin/cyanidin ratio, the sweet potato clones were classified into two groups: cyanidin and peonidin types. The reflectance value L* of the paste was negatively correlated with the color value, while no correlation was found between the b*/a* ratio and the color value. Furthermore, a significant posittve correlation was observed between the L* value, b*/a* ratio and peonidin/cyanidin ratio. Especially, the blue domi-nant clones showing a b*/a* ratio below -1.4 all belonged to the cyanidin type. These results indicate that in the peonidin types the increase in the peonidin/cyanidin ratio increased the degree of redness of the paste, and in the cyanidin type, the blue color predominated. These findings suggest that it is possible to predict the anthocyanin content and composition roughly by the analysis of the paste color without HPLC investigations. The b*/a* ratio of the paste could be used for the selection of the peonidin type, to obtain a paste with a bright and reddish purple color in sweet potato.

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The location of the 18S ribosomal RNA gene (rDNA) was studied by fluorescence in situ hybridization (FISH) on peach (Prunus persica (L.) Batsch) cv. ‘Ohatsumomo'(2n=16) chromosomes. The 18S rDNA Ioci were detected at the satellites, termini, and in the proximal regions of the respective two chromosomes. The 18S rDNA Ioci corresponded to chromomycin A₃ (CMA)-positive and 4'-6-diamidino-2-phenylindole (DAPI)-negative bands of the chromosomes.

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