Molecular studies have shown that several genes with various functions are induced by environmental stresses such as drought, high-salinity and low temperature in plants. Most of the dehydration responsive genes are induced by the plant hormone abscisic acid (ABA), but others are not. Expression analyses of dehydration-responsive genes have provided at least four independent regulatory systems (regulons) for gene expression in a model plant Arabidopsis thaliana. The cis-acting elements in the promoters of some genes that have a typical stress-inducible expression profile and the transcription factors that affect the expression of these genes have been analyzed. Transcription factors that bind to a DRE/CRT (dehydration-responsive element / C-repeat) cis-acting element were isolated and termed DREB1/CBF (DRE-binding protein 1/ C-repeat binding factor) and DREB2 (DRE-binding protein 2). Overexpression of DREB1/CBF in transgenic Arabidopsis plants increased tolerance to freezing,drought and high salt concentrations. The DREB1/CBF genes have been successfully used to improve abiotic stress tolerance in a number of different crop plants. Studies on the other transcription factors associated with stress response are in progress. We collaborate with many research groups to improve stress tolerant crop plants utilizing regulon biotechnology. We hope the results of these collaborative studies will contribute to the sustainable food production in developing countries and help to prevent the global-scale environmental damage.

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Since 1985, the Genebank project has been implemented as a national program to collect, characterize,evaluate, rejuvenate, conserve and use plant, microorganism and animal genetic resources for food and agriculture. NIAS has functioned as a center-bank of the project in cooperation with other agricultural public and private sectors. This national network on genetic resources for food and agriculture currently preserves approximately 233,000 accessions of crop germplasm and wild relatives of about 1,450 species involving 45,000 accessions of clonal crops. Among them 205,000 accessions are conserved as base collection, while 129,000 accessions, as active collection, are distributed for research purposes under the regulation of MTA between NIAS Genebank and recipients worldwide. We have undertaken international collaboration focusing on exploration for collecting genetic resources under the regulation of MOU or MOA with collaborating parties and on in situ conservation and on farm management of plant genetic resources in several Asian countries. Research highlights on conservation and utilization of plant genetic resources will be discussed in this report.

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Development of varieties with high resistance to blast disease had been an urgent need for rice production in the 1960s and 1970s, since blast epidemics prevailed on excellent varieties with resistance derived from some Chinese, U.S.A. and Philippine varieties. Our breeding project introduced high resistance from typical Indica varieties into the genetic backgrounds of Japanese varieties by backcross breeding, and developed Toride 1, Toride 2 and BL1 to BL7. Toride 1 and Toride 2 inherited Piz-t gene for resistance from Indian varieties, and BL1 to BL 7 inherited Pib gene from Indonesian and Malaysian varieties. Although Piz-t and Pib distributed widely among Indica varieties of South Asian countries showed resistance to a number of blast races in Japan, they were vulnerable to naturally-occurring virulent mutants. This paper reviews how Piz-t and Pib were introduced, identified, and utilized in the breeding and genetic researches conducted by the author and co-workers since 1960.

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There is an increasing interest in the extraction of DNA from soil, since molecular techniques facilitate the analysis of the microbial community including unculturable microorganisms. Though various methods of direct DNA extraction have been devised, it still remains difficult to extract DNA from some soils. We developed an improved method to extract DNA from such “recalcitrant soils”. Andisol, volcanic ash soils are recalcitrant in this context. Skim milk increased the efficacy of DNA extraction from such soils, when added to the extraction buffer as an adsorption competitor to soil particles. This method is applicable to molecular community analysis of soils which strongly adsorb DNA.

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The objective of this study was to clarify the relationship between amylose content and the gelatinization, retrogradation, and gelation properties of starch using wheat starches differing in amylose content. Starches were prepared by reciprocal crossing between waxy and non-waxy wheat, and mixing waxy and non-waxy wheat starch. Gelatinization temperature and endothermic enthalpy measured by differential scanning calorimetry correlated negatively with amylose content. Mixed starches showed significantly lower gelatinization onset and peak temperature than F₁ starches with the same amylose content. Rapid Visco Analyser measurement showed that F₁ starches had a higher peak viscosity than waxy and non-waxy wheat starches, and mixed starches had characteristic profiles with two low peaks. The rheological properties of 30% and 40% starch gels were measured using mixed starches with an amylose content of 5, 10, 18, 20, 23, and 25%. The slight difference in amylose content contributed greatly to the elastic component in starches forming a gel network. For 40% starch gels, mixed starch with lower amylose rapidly developed rigidity and had a higher rate constant of starch retrogradation. The proportion of waxy starch in the mixture played a major role in starch gel properties. Some of the gelatinization and gelation properties differed between mixed starch and simple starch isolated from cultivars, even though they have similar amylose content.

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The subject of this study was to examine a method of multiple texture measurement of cooked milled-rice grains and to develop techniques for quality evaluation on the basis of the method. The low-and high-compression (LHC) test, which measures surface and overall texture properties (25% and 90% compression ratios for the single grain thickness after cooking), was effective in enhancing the classification accuracy of the texture. A multiple regression model based on surface texture properties indicated higher prediction accuracy for palatability than that with using overall texture properties. The surface adhesion distance was adopted for distinguishing stickiness. Concerning the effect of protein content on texture among the samples of the same cultivar given different amounts of nitrogen fertilizer, the protein content showed a higher correlation with surface hardness than with overall hardness. Surface hardness was a more reliable indicator of protein content and palatability in the same cultivar. It revealed that the surface texture can be used as a key quality index. A multiple regression model of the LHC test was able to predict amylose content more precisely than using the conventional method. It was possible, using the single-grain method with the LHC test, to evaluate not only grain texture but also many other qualities such as protein content, palatability and amylose content.

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We investigated the usefulness of the promoter of a gene for tobacco elongation factor 1α protein (EF1 α) for transgene expression in the chrysanthemum (Chrysanthemum morifolium Ramat.). The EF1 α promoter was fused to the β-glucuronidase gene (gus) and introduced into the chrysanthemum. We obtained 238 putative transformants and GUS assay of the leaves of the in vitro plants revealed that 29.0% (69/238) of the putative plants were GUS-positive. The plants in the greenhouse that were 20 months after regeneration still showed a GUS activity in their leaves and petals. The tobacco EF1 α promoter expressed the transgene more efficiently than the 35S promoter of Cauliflower mosaic virus and could be used for transgene expression in chrysanthemum.

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The plant-pathogenic prokaryote Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial blight, one of the most important diseases of rice. The bacterium is a model organism for the analysis of plant-pathogen interaction, because more than 30 races differing in virulence and 25 resistance genes in rice have been reported to date. We present here the complete genome sequence of Xoo strain MAFF 311018. The size of the genome was 4,940,217 bp, in a single circular chromosome. The genome structure of Xoo MAFF 311018 was characterized by large numbers of effector (avr) genes of the avrBs3/pth family and insertion sequences (ISs). RFLP analysis of diverse strains using ISXo1 as a probe suggests that the prevalence of mobile elements in this species, which can bring about genome inversions and rearrangement, may have played a major role in generating the high degree of genetic diversity and race differentiation characteristic of this pathogen. The Xoo MAFF 311018 sequence was also highly similar to those of X. axonopodis pv. citri and X. campestris pv. campestris with the exception of the large number of effectors and IS elements, and numerous inversions and rearrangements.

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Five rhodesgrass (Chloris gayana Kunth) cultivars (Asatsuyu, Hatsunatsu, Katambora, Osumi-5, and Osumi-7) were evaluated for forage yield in a 3-year field experiment in the main island of Okinawa located in the subtropical region of Japan. The new cultivar Asatsuyu was significantly higher than the widely used commercial cultivar Katambora in dry matter yields at spring, fall and winter harvests during the second and third harvest years. Asatsuyu had significantly higher annual dry matter yields than Katambora and Hatsunatsu in the second and third harvest years. It was also significantly higher than Katambora and Hatsunatsu in total dry matter yield for 3 years. Annual dry matter yield showed significant positive correlation coefficients with dry matter yields harvested from winter to spring and from fall to early winter, suggesting that improvement of plant growth under low temperature conditions increases annual dry matter yield in rhodesgrass. In a growth room experiment at the National Institute of Livestock and Grassland Science in Tochigi, Asatsuyu was significantly higher in plant heights at 2, 3 and 4 weeks after seedling emergence and in dry matter weight at 4 weeks after seedling emergence than Katambora and Hatsunatsu at a low temperature (21/16ºC, day/night temperature). These results indicate that Asatsuyu has better performance than the other 2 cultivars at low temperatures. The results obtained in the field and growth room experiments show that the new cultivar Asatsuyu is superior to the other 2 commonly used cultivars Katambora and Hatsunatsu in seedling growth and forage production under low temperature conditions. The cultivar Asatsuyu can increase forage productivity and would extend periods of grazing and hay production in subtropical regions.

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The production of volatile sulfur compounds in modified atmosphere of packaged broccoli was investigated. Broccoli heads were sealed in 0.03-mm-thick low density polyethylene film and held at 10, 20 or 30ºC for 72 h. Nonpackaged heads were also stored at the same temperatures. In the package held at 30ºC, O₂ and CO₂ concentrations were less than 1% and more than 19%, respectively, and methanethiol was detected within 6 h. In the package held at 20ºC, O₂ and CO₂ concentrations were less than 0.4% and more than 17%, respectively, and methanethiol was detected within 18 h. The percentage of electrolyte leakage from packaged broccoli held at 20ºC and 30ºC increased to a greater extent than that of nonpackaged broccoli during storage. However, storing the packaged broccoli at 10ºC created a favorable modified atmosphere condition of around 3% O₂ and 10% CO₂ inside the package. In this condition volatile sulfur compounds were not detected and no significant change was observed in percentage of electrolyte leakage. At all temperatures, total chlorophyll contents were higher in packaged broccoli than in nonpackaged broccoli. These results indicate that, volatile sulfur compounds such as methanethiol were formed when the atmosphere inside the package had extremely low O₂ and high CO₂ even if broccoli was green and the visual quality had not deteriorated.

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To identify suitable cultural methods for seedlings of Acacia mangium Willd., the most important tree species for reforestation in the humid tropics of Southeast Asia, we studied the survival, growth, biomass, and yield of plantations of bare-root and container seedlings. The study was conducted at the Forest Research Centre Sabah in Malaysian Borneo for 14 years after planting. Survival rates did not differ significantly between seedling types. Individual height growth and stem weight increment were slightly larger for container seedlings for at least the first year after planting, but thereafter there was no significant difference in growth between the two types of seedlings. Biomass did not differ significantly between seedling types over the 14-y study period. As well, yield (estimated from the number of stems potentially usable as timber) did not differ significantly between seedling types over 7- and 14-y rotation periods. Bare-root seedlings have lower production costs than container seedlings and are easier to transport in large numbers. These advantages would make bare-root seedlings an important alternative to container seedlings, which are commonly used for the production of A. mangium in large-scale reforestation programs, at least as far as our research site is concerned.

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