The phenetic variations in seed polypeptides as revealed by SDS-PACIE electrophoretic profiles of 58 Brazilian rice varieties were analyzed. Cluster and discriminant functions analyses applied to the electrophoretic data allowed ten affinity groups to be distinguished which showed several correlations with the geographical distribution. This indi-cates that the electrophoretic analysis of seed proteins can be used to estimate the genetic relationship among rice varieties and to study the variability even among those of similar genetic background.

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Rice lines MR114, MR118 and MR119 were resistant to rice tungro disease (RTD) at Permatang Bendahari, Penang, Peninsular Malaysia during the off season of 1989. However, MR118 was rated as susceptrble at Bukit Merah, Penang in 1990 and at Kuala Muda, Kedah and Bumbong Lima, Penang in 1991. The mechanism of resistance involved in MR118 was suspected to the resistance to green leaffLopper (GLH) that was similar to that of IR42. IR42 which was generally cultivated as RTD resistant variety in the Peninsular Malaysia since 1981 also lost its resistance at Kuala Muda in 1991. Therefore, the break-down of MR118 before its official release was believed to be due to the development of the GLH population which acquired infestivity on IR42, resulting from the prolonged large scale planting of IR42 in the area.

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The influence of planted area of replaced host genotype on the types and patterns of nonrandom associations between avirulence loci in the pathogen was examined by a method of sitnulation. The influence of area occupied by replaced genotypes on the difference between observed frequencies obtained with simulations and expected frequencies under the assumption that Inutation to virulence occurs depending on avirulence genes was shown. The replaced genotype is called new genotype (or receptor) and the variety in cultivation before replacement is called old genotype (or donor). The shapes (Figs. I and 2) of curves of differences (x2) between observed values obtained from simulations and expected values from random association varied with the nuniber of susceptibility genes in the new and old host genotypes. Furthermore, fitness values given to the viru-lence genes influenced greatly on the shapes.

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Soybean is not well accepted as a human food source in the West because of its flavor. Isoflavones have been suggested as the cause of soybean bitterness and astringency. The isoflavone content of 22 Brazilian cultivars of different maturity groups was analysed by using High Performance Liquid Chromatography (HPLC). The content of daidzin and genistin in the Brazilian cultivars showed a consider-able variability among cultivars of the same and different maturity groups and between consecutive years (1990 and 1991). Insect-resistant cultivar IAC-100 exhibited the highest isoflavone content in both years, while cultivar BR-36 had the lowest.

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Immature pollen grains of an Indica type rice cultivar IR24 were isolated and cultured to regenerate green plants without preculture of anthers. Either low-temperature pretreatment of panicles at 10'C in the dark or exposure to sugar starvation in the beginning of culture were necessary for induction of cell division of the grains. Low-temperature pretreatment was more effective treatuent than exposure to sugar starvation. It was found that there was a complementary relationship between the effects of low-temperature pretreatuent and of exposure to sugar starvation the pollen grains required shorter period of exposure to sugar starvation to start cell division as low-temperature pretreatnent was prolonged. The optimal condition for induction of cell division of the pollen grains was 21 days of the pretreatuent with I day of sugar starvation or 28 days of the pretreatment without sugar starvation. Though 2, 4-D was not necessary for induction of cell division, the development of the derived colonies followed by shoot regeneration was observed only in the presence of 2, 4-D. Reduced nitrogen source in the induction medium also affected the frequency of both colony formation and plant regeneration. The medjum containing 20mM KN03 and 5mM glutamine as nitrogen sources gave the highest frequency of colony formation at 0.20/0 and its frequency reached 2.0 times higher than the control R2 medium containing 40mM KN03 and 2.5mM (NH4)2S04. On the other hand, the calli which were formed in the medium containing 20mM KN03 and 5mM alanine had the highest regenerating ability. In addition, the calli which were formed in the medium containing 20mM KN03 and 5mM alanine showed marked higher frequency of green plant regeneration than ones in any other media tested, when 21 days of low-temperature pretreatment without exposure to sugar starvation was applied as induction condition.

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Two intergeneric hybridizations through protoplast fusion between the embryogenic callus cells of 'Seminole' tangelo (Citrus reticulata Blanco X C. paradisi Macf.) and leaf cells of Indian atalantia (Atalantia monophylla DC.) or Chinese box-orange (Severinia buxifolia (Poir.) Tenore) were performed to overcome the genetic incompatibility. We were successful in regenerating whole plants of 16 somatic hybrids between 'Seminole' tangelo and Indian atalantia, and 46 somatic hybrids between 'Seminole' tangelo and Chinese box-orange, and hybridity was confirmed by Southern blot hybridization with rDNA. The mitochondrial DNA (mtDNA) of the somatic hybrids between 'Seminole' tangelo and Indian atalantia was identical to that of 'Seminole' tangelo, when rrn 26 and cox I were used as probes. However, when atp A was used as a probe, a 'Seminole' tangelo-specific fragment was found missing besides an Indian atalantia-specific fragment. The band pattern obtained by chloroplast DNA (CpDNA) analysis was identical to that of Indian atalantia. On the contrary, somatic hybrids between 'Seminole' tangelo and Chinese box-orange showed the mtDNA band pattern identical to that of 'Seminole' tangelo, when atp A and cox I were used as probes. However, analysis by rrn 26 probe showed the presence of a part of a Chinese box-orange-specific band in addition to a 'Seminole' tangelo-specific band. The cpDNA of the somatic hybrids was identical to that of Chinese boxorange. These results suggest the occurrence of mitochondrial recombination between parents

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Leaflet shape of thirty-nine soybean cultivars/strains selected to cover the possible diversity of leaf shape, was quantitatively evaluated by principal components scores based on the elliptic Fourier descriptor of contours. After central leaflets of fully expanded compound-leaves of the cultivars/strains were videotaped, binary images of the leaflets were obtained from those video images by image processing. Then, the closed contour of each leaflet was extracted from the binary images and chain-coded by image processing. Because the first twenty harmonics could sufficiently represent soybean leaf contours, 77 elliptic Fourier coefficients were calculated for each chain-coded contour. Then, the Fourier coefficients were standardized so that the coefficients were invariant of the size, rotation, shift and chain-code starting-point of any contour. The principal component analysis about the standardized Fourier coefficients, showed that the cumulative contribution at the fifth principal component was about 96 o/o' Moreover, the effect of each principal component on the leaf shape was clarified by drawing the contours of leaflets using the Fourier coefficients inversely estimated under some typical values of the principal component scores. Consequently, it was indicated that the principal components scores about the standardized elliptic Fourier coefficients gave us powerful quantitative measures to evaluate soybean leaf shape. The analysis of variance and multiple comparison indicated that the genotypic differences on the first, the second and the fifth principal components were significantly large. Because the variations of those principal components were con-tinuous, the effects of the polygenes on the (size-invariant) shape were also suggested.

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Anthranilate synthetase (AS) and tryptophan synthase (TS) enzymes were analyzed for characterization of 5-methyltryptophan (5MT) resistant mutant plants (MR 1) in maize. There were no significant differences in the level of AS activity between MR I and control seedlings when grown on MS medium without 5MT. However, the level of AS was 2 times higher in MR I seedlings grown on MS medium with 25 ppm 5MT than in control seedlings. The activity of AS from control seedlings was 50 o/o inhibited by 5 pprn tryptophan added to extract, while the enzyme from MR I seedlings was 50 o/o inhibited by 4 times higher concentrations (20 ppm) of tryptophan. The level of TS activity in MR I was 4 times higher than that in control seedlings when cultured on MS medium. For a more detailed study on TS, the gene encoding the tryptophan synthase B subunit (TSB) was isolated from maize and sequenced. The gene showed high homology to TSB isolated from other organisms. Northern hybridization analysis indicated that the gene expressed in MR I seedlings grown on MS medium at a higher level than in control seedlings. From the results, it was found that MR I plants showed differeces in the character of AS, as reported previously in cell lines resistant to 5MT, and also notable diversity regarding TS activity when compared to control plants.

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Four aneuhaploids (2n = 13) and 5 tetrasomics (2n = 26) of rice (Oryza sativa L.), which were obtained through anther culture of trisomics (2n = 25), were examined by Southern hybridization analysis to identify their extra chromosomes, to test their genetic stability, and to demonstrate their utility in genome alaysis. Twenty-one RFLP markers located on 9 chromosomes were used as probes. Extra chrounosome identification was conducted by observing dosage changes of the probes in the aneuhaploids and tetrasomics. The results indicated that the extra chromosomes of the aneuhaploids and tetrasomics were identical to their parental trisomics. The aneuhaploids and tetrasomics used in the study are genetically stable, except the aneuhaploid plant derived from the trisomic with an extra chromosome 5. This plant showed clear DNA variation. Chromosome assignment of unnrapped DNA clones was tried by using the identified aneuploids. The result showed that aneuhaploids and tetrasomics are useful materials for genome analysis in rice to assign cloned DNA fragments to specific chromosomes.

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In order to establish an efficient regeneration system re-quired for production of transgenic plants in the genus lpomoea, several culture media and methods were tested for embryogenic callus induction and plant regeneration in diploid I. tritida, the closest relative of sweet potato. Both of the two 2, 4-D-containing media resulted in the formation of embryogenic calli from shoot meristems, although at slightly different rates (40-56 o/o ). Genotype differences in embryogenic potential were found, with lines HI04-28 and H45-14 giving relatively high frequencies of embryogenic calli. In HI04-28, plant regeneration from embryogenic calli was achieved either through immediate transfer of calli to regeneration medium or through transfer of calli first to ABA-containing embryo production medium then to regeneration medium. Considerable number of plants were obtained in both methods, but immediate transfer of calli to regeneration medium gave a higher rate of plant regeneration. All the different MS-based regeneration media tested, whether hormoneless or containing NAA, were able to regenerate whole plants. The regeneration rates obtained froun the embryogenic calli were among the highest rates so far obtained from in vitro culture of lpomoea.

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We analyzed the genotype of the rice variety 'Norin-PL8', which harbors the genes for cool tolerance at the booting stage derived from a highly cool-tolerant javanica rice variety, Silewah. As a result, we detected the chromosomal segments introgressed from Silewah into Norin-PL8. Furthermore, we analyzed the quantitative trait loci (QTLS) for cool tolerance using RFLP markers on the introgressed segments. The results indicated that at least the introgressed segments on chromosomes 3 and 4 are responsible for the cool tolerance.

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Fifteen diploid (haploid X wild species) F1 families were generated at Huancayo, Peru in 1987. Haploid parents are adapted to long day tuberization conditions, while wild species clones were originated from short day conditions. First selection was made for tuberization under short day conditions and for tuber appearance in 517 F1 seedlings which were grown in a field at 3, 000 m above the sea level. Evaluation for 2n pollen production was conducted using acetocarmine glycerol stain, at least once at Huancayo (high land), San Ramon (subtropical), and Lima (irrigated desert) in Peru, and 60 clones were selected. These clones from First Division Restitution (FDR) 2n pollen via modified microsporogenesis. These 60 clones were evaluated for resistance to potato tuber moth, root-knot nematode, bacterial wilt and/or potato virus Y. Fifteen clones were selected from 2n pollen producing plants based on at least one resistance trait. Preliminary trials were made on 4x X 2x families using the selected diploid clones as males to determine the level of transmission of the quantitatively inherited resistances for root-knot nematode and potato tuber moth. The present work indicated that small population size at the diploid level could be used for simultaneous selection on adaptation for tuberization, 2n pollen, and resistance traits. Furthermore, it appears that selection of progeny from unadapted parents with respect to short day tuberiza-tion was effective if the selection is made on tuber forming ability rather than yield components.

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For analyzing the host-parasite interaction of Fusarium head blight in wheat and barley caused by Fusarium spp., a total of 104 Fusarium strains were inoculated to two varieties each of wheat and barley (Exp. 1), half of the strains were reexamined. in the next year (Exp. 2), and 12 strains were inoculated to ten varieties each of wheat and barley (Exp. 3) . Cut-spike inoculation method developed by the authors was adopted and the infection rate was evaluated based on the percentage of infected florets (barley) or infected spikelets (wheat) . Correlation coefficient for the infection rate between two years was exceeded 0, 6 indicating the stable expression of the disease reaction. In Exp. I and 2, analysis of variance for the infection rate revealed that the host-pathogen interaction was statistically significant. But the strain X within barley and strain X within wheat interaction was very small and almost statistically insignificant, indicating that differentiation of thepathogenicity within the host species was not appreciable. Although the interaction of strain X (barley vs. wheat) was statistically significant, its variance ratio was as small as about 2. The correlation coefficients between the hosts were very high (more than O.8), and the principal component analysis revealed that the first component showing the general pathogenicity accounted for more than 89 % of the total variation whereas the second principal compo-nent reflecting the specific pathogenicity between barley and wheat accounted for only 5-6% of the total variation.

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To identify varietal diverity of seed glucosinolates content in Japanese rape (Brassica napus L.), total amount and composition of seed glucosinolates content were analysed on 65 Japanese rape and 11 European and North American low glucosinolates rape (Table 1) by means of Palladium-glucosinolate complex method and high-performance liquid chromatography (HPLC) method. The average of total amount of glucosinolates of Japanese cultivars varied from 60. 5 μmol/g of Norin 18 to 161. 4 1lmol/g of Norin 12 (Fig. 1) . In 50 Japanese cultivars, Norin 18 (60. 5 pmol/g) and Norin 16 (65. 4 μmol/g) showed the lowest glucosinolates contents. On the other hand, glucosinolates content of Norin 12 (161.4μImol/g) and Isuzunatane (150.9 μmol/g) were the highest. These four cultivars were originated from interspecific crossing of B. napus X B. campestris. HPLC analysis of seed glucosinolates revealed that rapeseed had 10 main peaks (Fig. 2) . In these peaks, 9 glucosinalates were identified by high-performance liquid chromatography/mass spectrometry. Low gluco-sinolates contents in Norin 18 and Norin 16 resulted from the reduction of Progoitrin and Gluconapin which are Aliphatic glucosinolate. Though, Japanese cultivars have been bred by three different breeding methods, e. g. pure line selection, varietal crossing (B. napus X B. napus) and interspecific crossing (B. napus X B. campestris), each glucosinolate content was not related to the breeding method (Table 2)

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A rice mutant lacking alcohol dehydrogenase (ADH) was isolated by screening the M2 Iines of the rice cultivar Kinmaze that had been treated with N-methyl-N-nitrosourea. The mutant seedling lacked all of three isozymes of ADH, and was estimated to carry a single recessive mutation. Germination of mutant seeds was severely suppressed when seeds were submerged. However, mutant seedling survived under submergence for seven days and grew normally when transferred to aerobic conditions. These results indicate that ADH is essential for germination under anaerobic conditions but is not a prerequisite for growth under aerobic conditions.

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Restriction fragment length polymorphism (RFLP) analysis was carried out to determine the location on the chromosome and the locus of the resistance gene to brown planthopper, Bph-1, on the linkage Inap of rice, Oryza sativa L.. Our results showed that Bph-1 was not located on chromosome 4 but on chromosome 12, that is, Bph-1 was linked at the recombination value of 10.7 % with a RFLP marker XNpb 248 on chromosome 12. Based on the recombination value between Bph-1 and RFLP markers, the arrangement was as follows ; Bph-1 -XNpb 248 -XNpb 336. This is the first report on the tagging of a resistance gene to brown planthopper in rice.

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In the process of constructing a detailed genetic map of rice using two cultivars, Nipponbare and Kasalath, 79 DNA probes (approximately 6.1 o/o of total DNA markers) showed two or more RFLP bands in Southern hybridization and were mapped at duplicate or triplicate loci over the 12 chromosomes. Thirty-three DNA probes were mapped in the distal regions of rice chromosomes 11 and 12. Thirteen among 33 DNA probes were detected at duplicate loci. Linkage alignment of these 13 markers on both chromosomes agreed perfectly within a distance of ca. 12 CM from the distal ends of chrounosomes 11 and 12. However, the other 20 DNA probes were mapped only on either chromosome 11 or chromosome 12, because the other bands were monomorphic between Nipponbare and Kasalath. These results indicate that the regions on rice chromosomes 11 an 12 are highly conserved as a duplicated chromosomal segment. Such highly conserved segments were not found anywhere else in the other chromosomes in our map.

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The endosperm of a common wheat produced by genetic elimination of waxy (Wx) protein turned red-brown by iodine staining in F3 and F4 generations, indicating the presence of a waxy phenotype. Measurement with an autoanalyzer revealed that the F3 and F4 generations of variant wheat contained 0.6 - 0.7 o/o amylose in the endosperm starch, values comparable to those of a waxy rice variety (O o/o amylose), suggesting that the waxy phenotype is inherited in a stable manner. In the waxy common wheat, both A max and the blue value of endosperm starch indicated a marked reduction in the content of amylose. These results confirmed that wheat deficient in the Wx proteins lacked amylose. The production of a waxy wheat may be a significant step toward genetic modification of starch composition in wheat flour.

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The F₁ plants between an indica strain with semidwarf-ing gene sd-6 and a japonica glutinous strain with gene sd-1 gave a high spikelet fertility. The F2 distribution of fertility appeared to correspond to a 9 : 6 : I : seg-regation. F₂ Iines selected for high fertility ( > 80 % ) breed true in later generations. The F₂ seeds showed maternal effect on size L/W ratio and partial dominance for short grain. When compared with data for rice kernels excavated from Homudu, China, the F₂ seed-size data showed close similarity, with some difference only in the mode of variation. The seed size of the japonica and indica parents came close to the extremity of variation of Homu-du kernels as well as to the t, ails of the F₂ population. A number of elite lines of various grain types which carried desirable traits of both japonica and indica were obtained. Discussion was ext, ended to increasing genetic diversity and disease toler, ances of rice cultivars to meet with changeable natural environment by using fer-tile japonica -indica crosses. The differentiation of Keng and Hsien types in China wolLtld possibly have proceeded from their diversified progenitors after their spreading, some 3, 000 years ago. A review of historical events, archaeological and biological studies were also pre-sented in this paper.

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Yunnan province in China is located in the center of genetic diversity of cultivated rice, an area which in-cludes East Nepal, Bhutan, Assam in India. Myanmar, Laos and Northern Thailand (Chang, 1976; Nakagahra and Hayashi, 1977). Several studies on genetic variation and differentiation of the Yunnan rice varieties based on isozyme analyses (Hu et al., 1981; Nakagahra, 1984; Zhu et al., 1984; Xiong et al., 1987; Nagamine et al., 1992) have been conducted, indicating that allelic varia-tions at the isozyme loci increase from north to south in the province and that genetic diversity is the highest in the varieties from the southern and/or southwestern re-gions of the province. Geographically, this region is bordered by Myanmar. Laos and Vietnam and is located in the northeastern part of the center of genetic di-versity for cultivated rice. However, the sampling sites of the varieties used in previous reports were apparent-ly rather limited; the materials from the northern region of the province were particularly scarce. To reconfirm that the rice varieties from the southern or southwest-ern region in the province show the highest genetic di-versity, a larger number of indigenous varieties, collected from almost all counties in the province, were analyzed for isozyme variation at the county level.

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