Suspension cultures were initiated from immature leaf-let derived callus of Arachis hypogaea L. in MS Iiquid medium supplemented with 2, 4-D, NAA and BAP. On transfer to MS Iiquid medium supplemented with different concentrations of 2, 4-D, NAA and BAP, Iarge number of somatic embryos differentiated when the suspension was cultured for 7 days in the induction medium. The cells destined to become somatic embryos divided to form spherical of filamentous proembryos. The filamentous proembryo developed into different shapes ofembryos. Somatic embryogenesis began in the proembryo stage and proceeded from globular to dicotyledonary stage. The somatic embryos developed normal morphogenesis. The frequency of somatic embryogenesis was dependent on the genotype and auxin concentration used. Mature plants have been obtained, although the frequency was low with this procedure. This protocol can be used for production of disease resistant and salt tolerant plants from the selected cell lines.

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Isozyme polymorphism was studied for melon cultivars, in order to identify suitable markers for seed purity test of commercial Fl cultivars of Japanese muskmelon. Intraspecific variation was detected by the analysis of acid phosphatase (APS) isozymes. A total of 108 melon cultivars, covering five varieties of C. melo, was classified into five zymogram types according to APS zymogram. As for pure line cultivars, D type was commonly found in all the varieties, while C type was specific to var. inodorus. F₁ cultivars of muskmelon were all classified as A type which was considered to be homozygous at APS Ioci, and thus it was impossible to test seed purity by the analysis of APS isozymes. On the other hand, the analysis of peroxidase (POX) isozymes enabled to classify melon cultivars into three major groups (Px_2A, Px_2B, and hetero-type). Breeding lines for disease resistance belonged mostly to the Px_2A type, and pure line derivatives of a high fruit quality cultivar ‘Earl's Favourite' were all classified as Px_2B type. It was thus suggested that the demand for both fruit quality and disease resistance resulted in the breeding of hetero-type cultivars, which accounted for half of the F₁ cultivars. For hetero-type cultivars, it is possible to detect the contamination by selfed seeds of the female parent by the analysis of a single POX marker, and it takes only nine days for analyzing seed samples. Purity test for seed samples of four commercial F₁ cultivars showed that contamination sometimes occurred at a low frequency. The results clearly indicated that this method is practically applicable to seed purity test for many cultivars of Japanese muskmelon.

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We first characterized the graphical genotype of a japonica rice parental line, Norin-PL6 (Ou-PL1), which was bred to introduce the resistance genes to the green rice leafhopper (Nephotettix cincticeps UHLER: GRL) from an indica rice variety, Lepe-dumai, in order to identify the chromosome loci of resistance genes, using restriction fragment lengtb polymorphism (RFLP) markers. It was observed that two chromosome seg-ments introduced from Lepe-dumai were located on chromosomes 3 and 11, based on the Lepe-dumai RFLP patterns on chromosomes 3 and 11, respectively indicated by neighborly five and two RFLP markers. Moreover, two quantitative trait loci (QTL) with major genic effects and interactive function, were detected in these regions on chromosomes 3 and 11, based on QTL analysis between the degree of resistance to GRL and the RFLP data in seventy-six B₁F₁ plants derived from the combination between the F₁ hybrid of Toyonishiki/Norin-PL6 and Toyonishiki a japonica susceptible variety used as a recurrent parent. Although, It had been already reported that the resistance of Norin-PL6 was controlled by two or three dominant complementary genes, one of them being Crh2, the gene symbol and chromosome location for the other resistance gene(s) had not been determined. It is inferred that the two QTL on chromosomes 3 and 11 corresponded to the dominant complementary genes for resistance. Moreover, no other resistance genes to GRL have been reported on chromosomes 3 and 11. Based on these results, we designates Crh4(t) as one of the complementary resistance genes in Norin-PL6, and confided it as a new gene. We could not determine whether Grh2 and/or Crh4(t) were located on chromosome 3 or 11, but we identified the RFLP markers whicb were linked to these resistance genes. These markers will enable would be useful to develop improved varieties or isogenic lines for resistance to GRL by the application of the marker-assisted breeding method. We will attempt to develop two kinds of isogenic lines which harbour independently each complementary gene for resistance using the RFLP markers, in order to elucidate the genetic mechanism of resistance to GRL and determine the location on chromosomes in Norin-PL6 in detail.

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Plant shape, an important factor in soybean plant breeding, is currently evaluated visually by soybean plant breeders, often making judgment unstable and subjective. The purpose of our study was to create procedure for objectively evaluating soybean plant shape. Features of shape were determined by image analysis. Tree-based models based on recursive partitioning were then used to categorize shapes into three classes -- “good”, “fair” and ”poor”-- or two classes ”good”and ”not good.”Classification results based on tree-based models demonstrated highly acceptable predictability. Although model-based performance attained approximately the same discriminatory level as conventional linear discriminant function, it had the distinct advantage of outstanding interpretability, with shape parameters in the best predictive tree-based model coinciding with those selected empirically by expert breeders.

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Evaluation of soybean plant shape in breeding is empirical and based on visual judgment, making it unstable and inefficient and pointing up the need for a quantitative alternative. Previous studies successfully applied evaluation by linear discriminant function, fuzzy logic or neural network, but these models required definition and selection of important features for judging shape. We developed a method based on a multilayer perceptron (MLP) with direct image input of binary soybean images which does not require any shape features. An MLP is a kind of neural networks, and can exhibit good performance in pattern recognition. A neural network is composed of units being simple processors, and connections between the units carrying numeric data from one unit to another. Units of an MLP are arranged on the layers, and connected each other between the adjoined layers. We used 326 soybean plant images judged either”Good” ”Fair” or ”Poor” by expert soybean breeders. The images were divided into supervisor and test data sets. We studied 175 different MLP structures, varying the number of layers, units and connections. After training each MLP with the supervisor data set, we evaluated matches between MLP output and breeder judgment with the test data set. The MLP with three layers, 8×8 input units, 16 hidden units and three output units proved to be the superior structure. Although performance in judgment was no higher than that of previous ones, our method has the decided advantage of not requiring definition and extraction of the shape features and may be applicable to other crops. We should note that the MLP structure is too complicated for us to understand the n]anner of breeders' empirical judgment through this model; that is, the MLP is almost a black box for us for the time being.

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Effects of the male sterile cytoplasm on twelve yield and agronomic characters of F₁ Japonica hybrid rice (Oryza sativa L.) were investigated. Two sets of isonucleo alloplasmic male sterile lines (A Iines) of “Nankeng 11 A”and “Nankeng 34 A”with four different cytoplasms from India cultivar Chinsurah BoroII(BT), Yunnan cultivar Eshandabaigu(D), wild abortion (WA) from a pollen sterile wild plant (O. sativa f. spontanea) found in Hainan Island and wild cultivation (WC) from a red awned wild plant (O. sativa f. spontanea) and their maintainers (B Iines), four restorers (R Iines) of “77302-1”, “Ninghui 3-2”, “C57”and“C Bao”were used to make hybrids of A × R (aF₁) and B × R (bF₁) Iines. Cytoplasmic effects were determined by the difference of aF₁-bF₁. Significant negative effects on plant height (PH), panicle neck length (PNL), number of seeds per panicle (NSP), seed setting percentage (SSP), harvest index (HI) and grain yield per plant (GY) and significant positive effects on number of panicles per plant (NP), spikelet number per panicle (SNP), 1000-grain weight (GW) and dry weight per plant (DW) were observed. Cytoplasmic effects significantly varied with different male sterile cytoplasms, which may be explained by the different restoring ability of R Iines for the four male sterile cytoplasms. BT and D type cytoplasms which had proper R Iines showed positive effect on grain yield, and their hybrids showed midparent heterosis and heterobeltiosis with an average value higher than 20%. Also, cytoplasmic effects significantly varied with different nuclear genetic background of B and R Iines and their interaction. These results suggested that it would be possible to minimize the negative cytoplasmic effect so as to obtain a hybrid with marked heterosis on grain yield by the proper selection of the male sterile cytoplasm, B and R Iines.

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In order to understand the genetic variation and relationship of taro, Colocasia esculenta (L.) Schott, isozyme analyses were initiated using fertile diploid taro accessions. Polyacrylamide gel electrophoreses were performed on leaf tissue of wild or cultivated taro accessions from Nepal and Thailand, and their progeny to determine genes controlling four enzyme systems: alcohol dehydrogenase, esterase, Ieucine aminopeptidase and phosphoglucomutase. A total of nine loci with two or three alleles were discovered encoding the four enzymes in leaf tissue among the materials used in this study. The isozymes at the two loci of alcohol dehydrogenase and esterase were in a dimeric form. Observed segregation ratios were generally not significantly different (P>.05) from expected Mendelian segregation ratios; however, distortions were observed at some loci and possible causes were discussed. These findings suggest the presence of allelic variants in other enzyme systems and precise classification of a wide range of diploid taro based on allozyme variations. Most of taro cultivars are triploids, which are considered to have evolved from fertilization of unreduced gametes of a diploid. The genetic analyses of isozymes on the diploids will provide useful information to investigate genetic variation, genetic relationship and evolution of not only diploid but also triploid taro.

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Morphological analysis was carried out in sweetpotato and its closely related lpomoea species. Based on the principal component analysis of 110 accessions×50 morphological characters, corolla size, corolla shape, sepal size, sepal color, sepal texture, plant pubescence, star shape inside of corolla tube bottom, and external nectary were recognized as key characters for taxonomical classification, and the accessions were classified into 3 groups. However, sweetpotato and the closest species, I. trifida, could not be separated clearly. RAPD analysis applied to the two species did not define their differences either. These results suggested that sweetpotato and I. trifida were very closely related to each other from viewpoints of the morphological and genetical variations, and they might be considered as one taxon.

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The gametocidal inhibitor gene (Igc1) and β-amylase isozymes of Asian common wheat cultivars were ana-lyzed to investigate a possible transmission route of common wheat to China and the eastern Asia. Frequency of lgc1 was clearly different between areas, being frequent in East China, Sichuan and Southwest Japan, and sporadic in Northeast China, Inner Mongolia, Xinjiang, Tibet and the westwards. In the bordering regions, both carriers and non-carriers of lgc1 were observed. Common wheat cultivars in east Asia can be, therefore, clearly characterized by this gene. A unique zymogram type J of β-amylase distributed only in Xinjiang, Northwest China, East China and Southwest Japan but not in the other regions. These specific distributions of adaptively neutral characters suggested the transmission route of common wheat to East China and Japan: It was introduced from Xinjiang to North-west China through so-called ‘silk-road'. During transmission, the population size must have once decreased, and plants with less genetic variation became founders of common wheat in East China, Sichuan and Southwest Japan. On the other hands, the cultivars in Northeast China, Inner Mongolia and Tibet were introduced through different ways.

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A novel procedure for rapid and cyclic clonal propa-gation of garlic (Allium sativum L.) through in vitro bulblet formation was developed. In contrast to the previously employed micropropagation methods that make use of a single shoot tip, basal plate or bulb scale explant per clove, we have used more than 40 root tips per clove of the garlic‘White roppen' as starting material. Use of roots as explants gave the unique opportunity of a continuous bulblet formation. One cycle of the process was consisted of three steps: (a) shoot initiation from root tips cultured on MS medium containing 1μM NAA and 10μM BA, (b) shoot proliferation on MS medium supplemented with 0.5μM BA, and (c) bulblet formation on MS medium containing 12% sucrose. After completion of one cycle, in vitro roots were used as secondary explants. One cycle was completed within 4 months, and 316 bulblets were produced from the roots of one clove in the first cycle. This method has potential for the production of 5, 838 bulblets from a single clove after two cycles completed within 10 months.

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We evaluated a method for testing the spiral growth of seminal roots in order to increase the seedling establishment rate of direct-seeded rice on the soil surface in flooded paddy fields. For the morphological observation of seminal roots, we used 1/2 MS medium supplemented with 10g/l sucrose and 2g/l gellan gum, and placed sterilized dehulled rice seeds on the medium. When ion exchange water was poured onto the medium (3cm depth), varietal differences in the frequency of the spiral root type were observed. Since seminal roots penetrated easily into the gellan gum medium at a low concentration, we used 0.25g/l gellan gum medlum and attempted to parametrize the spiral growth of seminal roots (Fig.1). Value of α/β was assumed to represent the degree of spiral growth of seminal roots. The α/β value (average within lcm of seminal root length) was closely related to the seedling establishment rate in paddy fields (r=0.967, P<0.OO1). Thereafter, to determine the measuring points, we projected the α/β value on a fixed point with linear interpolation and extrapolation. The α/β value for 9mm of semlnal root length on a fixed point showed the highest positive correlation with the seedling establishment rate (r=0.941, P<0.O1). Consequently, it was considered that the use of gellan gum medium at a low concentration was effective for the development of on in vitro testing method to increase the establishment rate of direct-seeded rice on the soil surface in flooded paddy fields.

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We investigated the relationship between the C hordein-genotype of Japanese malting barley and malting quality. The purpose was to evaluate the selection of malting quality by C hordein genotype. The C hordein genotypes of 115 Japanese malting barley varieties were classified into 6 types by the SDS-PAGE band pattern. Five types of them were known as standard alleles, which were Br, Cl, Ha, Ma and Pr, and one type was identified as new allele, Mi (Fig.1, 2, 3). 41.7% of these 115 varieties were Pr type, and lines bred recently in Fukuoka and Tochigi were predominantly Cl type (Table 1, 2). The varietal differences were significant at the malting quality such as kohlbach index, diastatic power, apparent final attenuation and total score among the C hordein genotypes (Table 3, 4). Varieties with Br or Cl genotypes appeared to have high malting quality. In addition, C hordein subunits composed of Br and Cl genotypes were related to high malting quality (Table 5). Furthermore, the relationship between C hordein genotype and malting quality was examined In 37 doubled haploid lines produced from an F₁ hybrid (Mi genotype × Cl genotype) by the bulbosum technique. The lines of the Cl genotype were significantly higher In diastatic power than those of Mi genotype (Table 6). These result suggested that selection of malting quality by the C hordein genotype could be used for the breeding of malting barley .

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Screening through the observation of root character-istics was performed in foreign rice varieties to widen the genetic diversity for drought tolerance of upland rice in Japan. A total of 255 varieties were cultivated in upland fields and their root distribution and characteristics were observed. Trench method was applied for direct observation of roots by digging a ditch at a depth of about 60cm after harvest. The root volume and thickness of each accession were evaluated at a depth of every ten or 15cm from the soil surface. The root volume or thickness at a 40 or 45cm depth showed a significant correlation with the recovery from drought exposure of seedlings. Therefore, deep-rooted varieties were expected to be more tolerant to drought. Some varieties originating from Africa, China, India and IRRI had deeper or thicker roots. IR3646, IRAT1O, IRAT109, IRAT110, JC81, SE319C and Nam Sugai 19 were selected as candidates for cross-parent in breeding for drought tolerance.

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