Phosphorus (P) is one of the most essential nutrients for rice. In this study, low-P tolerance of 35 chromosome segment substitution lines (CSSLs), derived from japonica cultivar ‘Koshihikari’ as the recipient and indica cultivar ‘Habataki’ as the donor was evaluated at the seedling stage under low-P hydropic conditions. A low-P tolerant substitute line was found, which has a ‘Habataki’ segment on chromosome 6. In QTL analyses, an F₂ population from the cross between japonica cultivar ‘Mizukagami’ and this substitute line was used, and QTLs for tiller number, maximum root length, and shoot fresh weight were detected near a simple sequence repeat (SSR) marker (RM6836) on chromosome 6. Fine mapping of the QTLs revealed that they are closely linked loci. Our results indicated that the ‘Habataki’ QTL alleles conferred low-P tolerance not only on ‘Koshihikari’ but also on ‘Mizukagami’, and would thus contribute to breeding for low-P adaptation for various Japanese cultivars.

View full abstract

To explore alleles for the higher number of spikelets per panicle of a super-extra-heavy panicle cultivar of rice, Tsubumasari, the present study examined the nucleotide sequences of a locus for spikelet number, GN1A, in this cultivar and its parents, Milyang 23 and Nanjing 11, and also Habataki. Results of the sequencing of GN1A showed a total of 50 nucleotide polymorphisms, including substitutions, insertions, and deletions, in the coding sequence and untranslated regions in the group of Milyang 23, Tsubumasari and Habataki, compared with Nipponbare. Nanjing 11, another parent of Tsubumasari, demonstrated all polymorphisms, except for only one substitution of G to A in the second intron found in Milyang 23 and others. Therefore, at GN1A Nanjing 11 had a novel allele differing from Milyang 23. On the other hand, Milyang 23 had the same allele as already reported for Habataki. Moreover, Tsubumasari inherited the allele from Milyang 23 at GN1A. From the results of the recombinant inbred lines derived from Milyang 23/Nanjing 11, the novel allele of Nanjing 11, which can be identified using a CAPS marker, tended to decrease the spikelet number per panicle through a decrease in the number of spikelets on the secondary branches per secondary branch, compared with the allele of Milyang 23.

View full abstract

The modern agriculture has developed markedly with the aid of a large amount of fertilizer and pesticide. Long-term continuous use of a large amount of fertilizer and pesticide, however, brings about soil deterioration of agricultural land, and thus it is pointed out that agriculture itself will become unfeasible if the same situation continues. Practicing a low input sustainable agriculture (LISA), therefore, seems to be of urgent necessity to guarantee the sustainable development of the human. From such a point of view, two of the authors, Takeo and Tanisaka, developed “Takeo and Tanisaka Solution” (abbreviated as “TT-solution”) for the LISA. In the present study, we attempted to verify the promoting effects of TT-solution treatment on the growth of Brassica rapa var. perviridis, B. rapa var. laciniifolia, and B. oleracea var. acephala f. tricolor; consequently, the TT solution treatment was found to enhance the growth of the vegetables markedly, irrespective of the quantity of organic matter included in the soil. The soil microbial diversification and activity value (DGC Technology Inc.) became considerably larger by the TT solution treatment. These results indicate that the TT solution surely diversify the microbial flora in the soil, and thereby decomposes chemical fertilizer and organic matters into small molecule nutrients in the soil, which makes the soil fertile. Based on these results, we concluded that the TT solution would be one of the tools available for LISA.

View full abstract

Making agricultural soil healthy and fertile with the aid of soil microbes, as well as raising cultivars with strong disease and/or pest resistance, and those with high nutrient absorption ability, will be helpful for practicing low input sustainable agriculture (abbreviated as LISA). In the process of examining the effects of the soil-microbial flora activating agent “Takeo-Tanisaka solution” (abbreviated as TT solution), which two of the authors developed in 2006, on the growth of spinach and carrot, it proved not only to promote the growth of the vegetables but also to restrain the outbreak of the soil-infectious rhizoctonia disease caused by a plant pathogenic fungus Rhizoctonia solani. From these results, we conclude that the TT solution diversifies and activates the soil microbial flora, and thereby prevents the outbreak of soil soil-infectious plant diseases, which indicates that the TT solution becomes an effective tool in practicing LISA.

View full abstract

Thirty-one lines of Oryza sativa／Oryza glumaepatula introgression lines (GLU-ILs) were tested for their internodal elongation in responses to gradual submergence. Submergence promoted internodal elongation in 29 GLU-ILs. Among them, GLU-IL135 possessing SNORKEL2 (SK2) and SK2-like genes derived from the donor parent deepwater type accession O. glumaepatula IRGC105668 and GLU-IL110 possessing ACE1 derived from IRGC105668 exhibited the highest internodal elongation rate. However, GLU-IL104 and GLU-IL107 possess SEMIDWARF 1 (SD1) gene derived from IRGC105668 but displayed slight internodal elongation. These results suggest that the SK genes and the ACE1 gene may contribute mainly to internodal elongation under submergence in O. glumaepatula.

View full abstract

The X-ray CT Measuring, for the rice seed aggregate excavated from the Daifuku remains and Thung Noi Lam remains and the rice straw aggregate excavated from the Karako-Kagi remains and Dainakanokominami remains, was carried out on the measurement condition of pixel size of 25.1μm and 12.04μm in SPring-8, and the two-dimensional consecutive images with clear microstructure of the panicle axis and the elongated internode of aggregate were obtained. By analyzing these images, the panicle neck node was distinguished from the node of the panicle axis and the elongated internode by the shape of the bract on the node. Based on the shape of the bract of the distinguished panicle neck node and the part which the primary rachis-branch connected to panicle axis, the panicle neck internode to be connected to the bottom end of the panicle neck node was identified. As a result, the number of the large vascular bundle of the panicle neck internode was evaluated using the cross section image of the panicle axis and the elongated internode of rice seed aggregate and rice straw aggregate excavated from the remains.

View full abstract

When seedlings of the japonica rice cultivar Nipponbare (NPB) and the indica rice cultivar Habiganj Aman II (HA II) were incubated in the dark, “upper roots” that emerged from the upper portion of the nodal region of the coleoptile grew obliquely upward, and “lower roots” that emerged from the lower portion of the nodal region grew obliquely downward. In light, the upper roots turned their growth direction below the horizontal regardless of the irradiation from above and below. The trait of the upper roots growing upward in darkness and downward in light may lead to growth of the roots near the surface in the soil, contributing to the formation of the root system of rice, which has a higher proportion of roots distributed in shallower layers than other crops. The growth direction of the upper roots in the dark changed obliquely downward by excision of the seminal root. This excision significantly promoted the elongation of crown roots in HAII, but not in NPB. This difference might reflect the difference in root system depth of these cultivars.

View full abstract

Gamma-aminobutyric acid (GABA) with hypotensive and stress-reducing effects should be consumed daily. Due to the increased GABA content of germinated brown rice, we considered that normal polished rice should be replaced with polished rice from germinated brown rice. In the present study, 20 varieties and 23 variants of rice were investigated to identify genetic variations involved in the production and endosperm transfer of GABA due to germination. Variations between cultivars or strains were observed both in the production and in the endosperm transfer of GABA due to germination. And, the GABA content in brown rice and the rate of increase in GABA due to germination were inversely proportional. So, it is considered that the GABA content in brown rice is not an appropriate selection marker for breeding GABA-enriched white rice varieties. In order to perform the selection, it is necessary to investigate the production of GABA during germination.

View full abstract

Finding countermeasures to combat climate change is an urgent issue for human prosperity. Crop science contributions could prevent a climate crisis by reducing greenhouse gas emissions or through the development of flexible crop cultivation techniques to cope with the increasing variability of weather conditions. In this mini-review, exploratory cultivation techniques we have developed are discussed by comparing these methods with conventional cultivation techniques. Firstly, the possibility of methane reduction using ultra-fine bubbles is described as a contribution to mitigate the climate change. Next, the close mixed-planting technique that can cope with the continuous occurrence of floods and droughts, which are expected to increase with climate change, are briefly explained. Finally, one of the possible cultivation techniques is raised based on the soybean cultivation in an upland field converted from paddy in the near future in an advanced climate change scenario.

View full abstract

Global warming is undoubtedly progressing. It is an important issue to develop biological production systems that can adapt to such environmental changes. As an example of research targeting this issue, this paper describes the background, contents, and challenges of the heat- and drought-tolerant wheat breeding project currently underway in the Republic of Sudan, Africa.

View full abstract

Changes in rain precipitation due to global climate change are expected to be a limiting factor in crop production because they will cause damage to crops by flooding or drought stress. To ensure stable crop production in the future, it will be important to improve the waterlogging or drought tolerance of crops. Since roots are the first organ to be affected by flooding or drought stress, it is important to consider the root design necessary for adaptation to waterlogged or dry soil, focusing on the root system and the anatomies of roots such as the aerenchyma, the radial oxygen loss (ROL) barrier, and the cortex／stele ratio.

View full abstract

In the field of soil science and plant nutrition, soil preparation and fertilizer application improvement are the main measures against climate change. The effects of soil preparation on climate change are various, including improve of soil fertility, sustainable crop production, and soil carbon storage in the soil. In paddy fields in Shiga Prefecture, soil fertility is declining not only due to global warming but also due to cultivating in upland field converted from paddy field. This indicated that investigating soil fertility in detail and soil preparation by organic matter such as cattle manure. We suggested topdressing method at the ear stage for high quality paddy rice Koshihikari production as an example. This method clearly reduced the occurrence of white immature kernels under high temperature conditions.

View full abstract

Biomass utilization can significantly contribute to carbon neutrality as biomass can be used as feedstock for petrochemical products and to generate bioenergy. In this review, we introduce sorghum, which has attracted much attention among biomass crops in recent years. In addition, we propose a rapid and effective crop breeding method based on hybrid vigor.

View full abstract

Global warming and associated changes in precipitation patterns caused by greenhouse gas emissions affect food production and availability, utilization, and stability of food security. Food systems, defined as the collective systems covering the activities and processes involved in food production, distribution, processing, and consumption, are a significant source of greenhouse gas emissions. This paper introduces recent studies on the impact of anthropogenic climate change on agricultural production and the actual status of greenhouse gases from food systems and discusses necessary research directions for the food system under future climate change.

View full abstract