Degeneration of embryo, endosperm and suspensor cells in hybrid embryo at 1 to 5 days after interspecific cross pollination in the genus Fagopyrum were studied by using a light microscope and transmission electron microscope (TEM) to determine the nature of the post-fertilization barriers of interspecific hybridization in buckwheat. In comparison with the self-pollinated or legitimate-pollinated embryo, interspecific hybrid embryos showed various post-fertilization ultrastructural abnormal phenomena such as failure of endosperm development, vacuolated embryo cells with degenerated endosperm, degeneration of embryo, endosperm and suspensor cells. Both endosperm and suspensor cells were degenerated. Their degeneration may lead to the loss of normal endosperm nourishing and failure of nutrient transport to the developing embryo and thus may trigger off the observed embryo abortion. Comparatively fewer abnormalities occurred in the hybrid embryo of the cross between F. cymosum and F. esculentum than in that between F. tataricum and F. esculentum. This indicates that the cross combination F. cymosum × F. esculentum may be considered as a breeding material in buckwheat hybridization. The deficiency and degeneration of endosperm that were observed at 2 to 3 DAP may lead to the degradation of hybrid embryo. Therefore, rescue of hybrid embryos at this critical stage (2-3 DAP) by ovule culture may overcome one of the main post fertilization barriers.

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A criterion for evaluating the practical advantage of spatial error control in single plant selection for lowly heritable traits, by either field preparation for environmental uniformity or statistical adjustment using spatial information from surrounding plants, was defined based on the principle of achieving the greatest success with the same long-term resource investment. The criterion was determined in the context of mass selection under practically possible values of the variables concerned, leading to the prediction that spatial error control will be rewarding only in some plants where the cost for error control is low compared to that for care management to raise the test plants. Error control will be of little use in other plants; improving the precision of selection when the population size is reduced is not rewarding. In cross-fertilizing cereal crops, error control for yield is predicted to be useful when the selection is performed in only a few cycles (generations), but the population size is important when the selection is performed in more cycles to best explore the genetic potential of the target population. In self-fertilizing cereal crops, spatial error control will in no case be cost-efficient. In both cross- and self-fertilizing crops, the population size becomes more important with a higher magnitude of the desired genetic advance.

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Using a small-type rice miller, Pearlest, equipped with barley polishing parts, brown rice could be simply and rapidly polished up to the targeted polishing ratio of 70 %. This method was characterized by a low ratio of broken rice, reduction of the loss of moisture content of the samples, and more spherical polishing of rice kernels. Twenty-minute water absorption was clearly enhanced in varieties such as Ipponjime with kernels showing a low hardness, and the nitrogen content was lower compared with the control method. But these tendencies were not considered to hinder the evaluation of relative varietal differences, because it was found that the nitrogen content and 20-minute water absorption ratio of polished rice by this method could be utilized as stable evaluation parameters revealing the intrinsic characteristics of the varieties. Development of this rapid polishing method is considered to be extremely important for efficient selection in breeding programs for brewer’s rice, because it may be possible to evaluate the nitrogen content of 70 %-polished rice and water absorption properties which had not been examined so far in earlier generations.

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By backcrossing to Raphanus sativus cv. ‘Pink ball’, 55 BC₂ plants were obtained from two sesquidiploidal BC₁ plants (MaRR, 2n = 32) between Moricandia arvensis (MaMa, 2n = 28) and R. sativus (RR, 2n = 18). Their somatic chromosome numbers ranged from 2n = 18 to 2n = 23, except for one hyperploid plant with 2n = 44. In the BC₃ generation, 64 plants (2n = 19) were generated from 16 BC₂ plants with 2n = 19~23. Each plant with 2n = 19 exhibited both morphological and physiological characteristics diagnostic for the presence of an added chromosome of M. arvensis genome, and showed predominantly the chromosome pairing type of 9II + 1I at metaphase I of PMCs. They were classified into twelve (a~l) types of monosomic chromosome addition lines (MALs) of alloplasmic (M. arvensis) R. sativus carrying M. arvensis cytoplasm by their morphological, physiological and cytogenetical characteristics. The mean of seed setting in the twelve types of MALs ranged from 2.88 grains (f-type) to 0.51 grains (j-type) per pollinated flower when they were backcrossed to R. sativus cv. ‘Pink ball’. The transmission rates to the next generation through female gametes ranged from 32.5 % (f- and j-types) to 5.5 % (h-type) when smaller seeds were selectively grown. The specific characteristics of each type of MALs were transmitted from the BC₃ generation to the BC₄ and BC₅ ones without any modification. The MALs of the distinctive twelve types were also identified using RAPD markers in the BC₅ generation. Pollen fertility of the twelve types of MALs ranged from 85.6 % (c-type) to 3.4 % (l-type), although four types (g-, h-, i- and j-types) exhibited complete male sterility. Furthermore, alloplasmic (M. arvensis) R. sativus plants (2n = 18) which were derived from male fertile MALs showed complete male sterility. The twelve types of MALs produced in this study should be useful materials to determine the localization of genes for agronomic traits on the individual chromosome of M. arvensis and the alloplasmic (M. arvensis) R. sativus should also be a useful material for the development of a new cytoplasmic male sterility system in R. sativus.

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In hybrid rice breeding programs, it is the most important to select donors for improving parental lines and to predict the hybrid performance. In this study, AFLP marker technology and a half-diallel method were used to address these related issues in hybrid rice. Based on the representative heterosis characters representing in the F₁ generation, an innovative method was designed to identify the genetic diversity related to heterosis for yielding with the detected AFLP. The results showed that the genetic diversity among the parental lines was certainly related to F₁ heterosis, and a few loci contributed to hybrid vigor. We discovered 11 favorable alleles with different genetic effects significantly contributing to the heterosis in grain yield among 85 AFLP markers, and 8 unfavorable alleles that significantly reduced heterosis. Based on the favorable and unfavorable alleles found, 42 accessions were evaluated for the exploitation potentials of heterosis, as reference for hybrid rice breeding. Moreover, some aspects related to heterosis formation are discussed in this paper.

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We postulate the phylogenetic relationships of section Archelirion (genus Lilium) based on the nucleotide sequence variations of three spacer regions in chloroplast DNA, trnT-trnL, trnL-trnF and atpB-rbcL. The sequences aligned provided a matrix of 1,627 bp, and were analyzed phylogenetically by the maximum parsimony method. Section Archelirion was divided into two major clades, one consisting of L. auratum var. auratum and L. rubellum, and the other consisting of the rest of taxa in Archelirion. The cytoplasm of the former clade was regarded as the rubellum type (eastern type), and that of the latter clade as the japonicum type (western type). Each taxon was monophyletic, but two varieties of L. auratum were belonged to a different clade. The phylogeny of L. auratum var. auratum is different from that of L. auratum var. platyphyllum, and it has a sister-relationship with L. rubellum. These results provide a more convincing phylogenetic relationship within section Archelirion.

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Gibberellin (GA) 3β-hydroxylase catalyzes the final step of active GA synthesis in plants. In rice, the enzyme is encoded by at least two genes (OsGA3ox1 and OsGA3ox2) with differential patterns of expression. Previously, we reported that the OsGA3ox2 gene is identical with the D18 gene. The loss-of-function mutants of D18 designated as d18-AD (Akibare waisei), d18-Id18^h (housetsu waisei), and d18-dy (Waito-C) show severe dwarfism caused by the decrease of the level of active GA, GA₁. The gene encodes GA 3β-hydroxylase that catalyzes the reaction from GA₂₀ to GA₁ and its expression is also regulated by active GA through a feedback mechanism, suggesting that the step catalyzed by the enzyme may be a key step for regulating the level of active GA. To determine the possibility of reducing the height of rice through regulation of the level of active GA, we produced transgenic rice plants expressing the antisense of D18 cDNA. Plants expressing the antisense showed a semi-dwarf phenotype relative to the control plants carrying the vector only. The antisense plants with the semi-dwarf phenotype showed a reduced level of D18 mRNA. In contrast to the reduced level of D18 mRNA, the plants induced a higher expression level of OsGA20ox1, which encodes GA 20-oxidase catalyzing the step from GA₅₃ to GA₂₀ in the GA biosynthetic pathway. These results demonstrate that the height of rice can be controlled by manipulation of the GA 3β-hydroxylase expression through the decrease in the active GA level.

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Tomato plants were transformed with a truncated replicase gene encoded by RNA 2 of cucumber mosaic virus (CMV) strain GT, subgroup II. The truncated replicase gene does not retain a C-terminal region of the gene that contains the GDD amino acid motif and the NTP binding motif. These motifs are considered to correspond to active and/or recognition domains of RNA-dependent RNA polymerase. Upon transformation via Agrobacterium tumefaciens, 137 individual transgenic lines were obtained. Each transgenic line was evaluated for resistance to CMV. About 10 % of the transgenic lines were highly resistant and the remaining 90 % showed a moderate resistance or were susceptible. The 15 lines were selected as resistant lines. Chenopodium amaranticolor was used to analyze the multiplication of CMV in the symptom-less plants. Among the selected lines, three lines did not appear to show any multiplication of CMV in both inoculated and non-inoculated leaves. Based on transgene amplification by PCR and the kanamycin resistance assay, the T₁ progeny of the selected lines harbored the transgene. Several resistant lines of the T₁ generation were resistant to viral inoculation. These resistant lines could become suitable breeding materials for resistance to CMV.

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The random amplified polymorphic DNA (RAPD) technique has been used widely for purposes such as the construction of linkage maps, QTL analysis, evaluation of genetic diversity, and parentage tests. However, some minor bands of RAPD display a low reproducibility and low reliability. We describe a simple and efficient method for making minor RAPD bands clearer. The first step of this method is to synthesize primers with nucleotides (A, T, G, or C) added to the 3′-end of the original primer sequences. The second step is to perform PCR using them and their combinations with the original primer. The final step is to conduct an electrophoresis analysis. The target bands can be emphasized, and needless background bands can be eliminated. The resulting emphasized RAPD (e-RAPD) bands are clearer and show a higher reproducibility than the original bands. This method has four advantages. (1) The developed e-RAPD bands can be used directly for marker-assisted selection (MAS). (2) The amount of DNA in the target band can be increased and, as a result, conversion to an STS marker, if necessary, is easy. (3) There is a lower risk of missing polymorphisms than with conversion to a sequence-tagged site (STS) marker. (4) The method requires only primer synthesis and PCR, and thus after primer synthesis, the process can be completed within several hours. Easy, low-cost and time-saving detection system is a prerequisite for practical MAS for breeding purposes. For practical MAS, the method presented here using RAPD and conversion to e-RAPD is simpler and easier to apply than using amplified fragment length polymorphism (AFLP) markers or conversion to STS markers.

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