The origin of the semidwarfing gene(s) in the japonica rice cultivar Kinuhikari and its location on chromosome was studied. A quantitative trait locus (QTL) analysis using restriction fragment length polymorphism (RFLR) markers was conducted in the F₂ from the cross Kinuhikari/Koshihikari and B₁F₁ from the cross Koshihikari/Kinuhikari//Koshihikari. Seven RFLP loci showed a polymorphism between Kinuhikari and Koshihikari. A strong QTL reducing culm length when the genotype was of the Kinuhikari-type (homozygous) was detected close to the RFLP loci C86 and C385 on chromosome 1. This QTL explained 74% of the total variation of culm length in the F₂ population. The analysis of polymorphism for the C86 and C385 loci among Kinuhikari and all the cultivars used to breed it showed that the region containing the semidwarfing QTL on chromosome 1 in Kinuhikari was derived from the indica rice cultivar IR8, which is known to harbour a semidwarfing gene sd1 between these two RFLP loci. These results indicate that the semidwarfing gene in this chromosome region in Kinuhikari is sd1. An allelism test using QTL analysis showed that the sd1 in Kinuhikari was different from a semidwarfing gene d49 in Reimei, which had been assumed to be identical with sd1. Another QTL was found near the RELP locus G1073 on chromosome 8. This QTL led to a longer culm when the allelic constitution corresponded to the Kinuhikari-type, and explained about 18% of the total variation of culm length. In the F₂ population from the crosses Kinuhikari/Koshihikari and Kinuhikari/Reimei, the homozygous plants for the sd1 locus showed a transgressive segregation for short culm. The combined effect of the two QTLs could not completely explain the distinct transgressive segregation. It was suggested that other genes modify the effect of sd1 (a recessive allele at the QTL on chromosome 1) in Kinuhikari.

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Most mutants lacking nitrate reductase (NR) activity show a chlorate resistance, but a mutant line M1004, screened based on chlorate resistance, exhibited the same level of NR activity as the wild type Norin 8. Here, we characterized a mutant line M1004 and compared it with a NR deficient mutant line M819 and original cultivar Norin 8. M1004 showed a higher chlorate resistance than M819 at a higher chlorate concentration (1 mM). The same level of NO^-₃ and ClO^-₃ uptake as well as NRmRNA expression was observed in the mutant lines and wild type. NR-mRNA expression was induced in KClO₃ solution although the NR activity was inhibited. M1004 exhibited higher a deactivation velocity of NR than the wild type. The results suggested that chlorate resistance in M1004 was caused by the rapid deactivation of NR. This chlorate resistance was transmitted by a single recessive nuclear gene.

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A dm-type rice mutant DMF-1, which was induced by X-ray irradiation of plants of the rice cultivar Fujiminori (Yamaguchi 1976), showed semidwarfism with an apparently normal growth except for the inhibition of elongation of the 2nd internode. This mutant character was found to be controlled by a dominant gene Ssi1 (short second internode 1)(Wu et al.1997b). The culm of DMF-1 (65.2cm) was significantly shorter than that of Fujiminori (82.1cm) and the semidwarf cultivar Reimei (70.4cm). The F₁ reciprocal hybrids between DMF-1 and Fujiminori tended to show an intermediate culm length between that of their parents. There were no significant differences in agronomic characters such as panicle length and panicle number among the F₁ reciprocal hybrids and their parents. The expressivity of the dm-type (EDM), represented by the percentage of the number of dm-type culms to the total number of culms per plant, was estimated in the F₁ and F₂ from the reciprocal crosses between DMF-1 and Fujiminori. The Ssi1Ssi1 plants exhibited 100% or nearly 100% EDM in all the different cropping seasons. However, in the Ssi1+plants EDM was unstable even in the same season. Therefore, it was assumed that DMF-1 was controlled by an incompletely dominant gene Ssi1. Results of linkage analysis using two morphological marker genes showed that Ssi1 could be located between rl4 (rolled leaf 4) and shr1 (shrunken endosperm 1) on chromosome 1 with recombination values of 10.4 and 10.1%, respectively.

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Genetic distance was calculated based on random amplified polymorphic DNA (RAPD) analysis among hop varieties. Multiple regression analysis of the amount of the major chemical components in selected hop varieties on their genetic distance from major hop varieties was performed. Regression functions with relatively high multiple correlations were obtained although no prediction could be obtained for farnesene. The regression function was applied to male parent evaluation. THe results of this study suggest that the use of genetic distance for predicting phenotypic values of major chemical components of hop varietiesis suitable. The method presented here should enable to select individuals with stable qualities before cones are produced and male parents for which phenotypic data could not be obtained.

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We examined the pre- and post-fertilization barriers in the interspecific cross of O.sativa, a cultivated Thai rice species and O.minuta, a wild species native to Asia. A 9.6% seed set was obtained from 649 pollinated spikelets. However, the seeds had abnormal embryos with degenerating endosperm. The F₁ hybrid embryos failed to mature on the maternal plants. The pre-fertilization barriers observed were anomalous and stunted growth of pollen tubes in the style. Some of the pollen tubes reached the micropyle and the average rate of fertilization for the interspecific cross was 61.4%. In the interspecific cross, the fastest pollen tube reached the micropyle 10 hours after pollination, while it took only 5 hours in the parents. The major post-fertilization barrier observed was embryo breadkown. The hybrid embryos ceased to develop at the pre-globular, early globular or globular stage within 6-12 days after pollination (DAP). The size of the interspecific hybrid embryo at this stage was equivalent to that of a 1-to 2-day-old self-pollinated embryo. Arrested embryo growth and subsequent abortion around 10-12 DAP was associated with the failure of endosperm development. Only a small amount of free endosperm nuclei or cellular endosperm was observed in the embryo sac. Hybird embryos were rescued by culturing 10-to 14-day-old immature embryos on Murashige & Skoog (MS) agar medium containing 3 mg/l benzylaminopurine, 1 g/l yeast extract, 15% coconut water and 3% sucrose. Active tillering was observed on media supplemented with 0.3% activated charcoal. All the 24 F₁ hybrid plants thus obtained were completely sterile. Colchicine treatment to the hybrids may provide an opportunity to derive some valuable fertile allohexaloids with desirable genes from the wild parent.

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Optimum number of cycles and rate of selection and optimum population size to give the highest cost efficiency in mass selection for allogamous crop plants were investigated. The optimum values of these variables were obtained based on the numerical calculations of a new selection efficiency index, S/C, where S stands for the probability that the desired genetic improvement is achieved in the target population, and C is the cost expended for that end. Selection procedures that maximize S/C will give the greatest opportunity of success under a certain total resource investment. The index S/C was calculated based on Monte Carlo simulations with a model in which the target population was initiated as a hybrid population of two cultivar lines that were genetically fixed for the trait concerned, and populations of a constant size were generated for subsequent selection cycles via random crossing between the plants selected with a constant rate in each cycle. The genes involved were assumed to be inherited independently and have to epistatic interaction. The calculations over practically possible ranges of the related variables led to the following conclusions. If, as would be the case in most selection projecrts for breeding a new commercial variety, the expenditure of time (years) rather than resource expense for managing the selection is important, a few to several cycles of selection with a rate of around 1%, testing a few thousand plants per cycle, should be nearly if not exactly the optimum. If the desired improvement is not achieved in these cycles, the population should be discarded and a new one should be tested. By contrast, if the time expenditure is not important, as in the case of the selection for new breeding stock lines, selection with several or more cycles, a rate in the range of 10 to 20% and a population size smaller than 100 should be costefficient. Dominance is not an important modifier of the optimum values unless the desirable genes are dominant or recessive unidirectionally at the majority of the loci involved.

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Soybean 〔Glycine max (L.)Merr.〕 cultivars with smaller area and lanceolate leaves have shown better light distribution through their canopy and a higher photosynthetic rate than those with larger leaf area and oval leaf shape. However, very little information has been published about leaf characteristics in relation to yield potential and inheritance which would assist breeding effects to develop new cultivars with optimum leaf area and leaf shape. Gene action and heritability for leaf area, leaf shape, and other reproductive characteristics were studied in a diallel cross including nine parents with large, medium, and small leaf area. Most progenies from crosses among parents with different leaf areas had larger mean leaf area, longer flowering, and later maturity than the midparent and both parents, suggesting transgressive segregation for these traits. General combining ability (GCA) and specific combining ability (SCA) for leaf area and leaf shape were significant in populations. Ratios of GCA to SCA were 0.96% for leaf shape and 0.89 for leaf area, indicating that GCA effects were more important than SCA. Genetic gain for leaf area and shape may be possible through selections. Narroow sense heritability estimated on the basis of variance components was 43.4% for leaf area, 63.2% for leaf shape, and 29.1% for maturity, which were lower than days to flowering and flowering period due to large error variances (σ²E) caused by field environmental factors. This study indicated that it is possible to optimize leaf area and leaf shape related to photosynthetic rate and subsequently yield, because of relatively large and significant GCA effects for these traits. The predominance of additive effects should improve the effectiveness of selection based on performance of individual cultivars.

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For AFLP analysis of grapes, three different concentrations of restriction enzymes were examined to reduce artifact bands due to incomplete digestion or star activity of the restriction enzymes. Differences among band intensities were neglected, and all the detected bands were used in the analysis. A phenogram of 12 cultivars of Vitis vinifera, two cultivars of V.labrusca and two wild species, V.ficifolia var.lobata (V.thunbergii, Ebizuru) and V.coignetiae (Yamabudou) was obtained by UPGMA (unweighted pair group method arithmetic averages) based on the percentage of unshared AFLP bands of each sample pair, using four primer pairs. This phenogram revealed a clear separation of the tested species and proles with high bootstrap probabilities, except for the clusters with a longer phenetic distance in the Oriental cultivars of V.vinifera. The cluster of Occidental cultivars split into a cluster consisting of Cabernet Sauvignon and Cabernet franc, and another cluster consisting of Pinot noir, Pinot blanc, Chardonnay and Riesling. Among the Oriental cultivars, two Japanese cultivars, Koshu and Koshu-Sanjaku, formed a cluster. Thus, this phenogram agreed well with the classification based on morphological properties and geographical location.

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The changes in the content and composition of anthocyanin in the developing storage root of 10 purple-fleshed sweet potato clones were investigated in order to elucidate the pattern of anthocyanin accumulation between clones with a high and low anthocyanin content. At the 3rd week after transplanting, in most clones, anthocyanins were detected in the young thick roots that had the potential to develop into storage roots. The pattern of anthocyanin accumulation was characterized into three distinctive phases: (1) an initial rapid increase during the 3rd to 6th week, (2) no change or a slight decrease during the 6th to 12th week, and (3) a slight increase during the 12th to 17th week. Northern blot analysis indicated that mRNA levels of dihydroflavonol 4-reductase (DFR), one of the key enzymes of the anthocyanin biosynthetic pathway, was expressed throughout the stage of storage root development. In addition, DFR mRNA appeared to be the most abundant at the 6th week, and reduced an the 9th week, which coincides with the change in anthocyanin content. These results suggest that anthocyanin is synthesized throughout the stage of storage root development, but not in a steady manner, and that anthocyanin accumulation in sweet potato could be related to the transcriptional regulation of anthocyanin biosynthetic genes. The rate of increase in anthocyanin content during the 3rd to 6th week was significantly higher in clones with a high anthocyanin content than in clones with a low anthocyanin content. It may be possible to screen clones after the 9th week when the percentage of peonidin, which is an index for anthocyanin composition in purple-fleshed sweet potato, become constant, and the large storage roots (more than 20 mm in diameter) are produced in most clones.

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