研究者詳細 - 仲田（狩野）　麻奈

論文 - 仲田（狩野）　麻奈

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Revealing the influences of organic amendment-derived dissolved organic matter on growth and nutrient accumulation in lettuce seedlings (<i>Lactuca sativa</i> L.) Open Access

Sonsri, K; Phankamolsil, N; Kano-Nakata, M; Watanabe, A

OPEN AGRICULTURE 9 巻 ( 1 ) 2024年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Open Agriculture

Although the application of organic amendment (OA) is a well-established agricultural practice, the effectiveness, optimal concentration, and key characteristics of OA-derived dissolved organic matter (DOM) in promoting the growth and nutrient accumulation of lettuce are not fully understood. To gain a better understanding, the effect of OA-derived DOM that was prepared from rapeseed oil cake (ROC) on the growth of lettuce was examined. Lettuce seedlings (7 days old) were transplanted into a hydroponic nutrient solution with varying DOM concentrations (10, 20, and 30 mg C L–1) along with the control treatment (no DOM addition), and shoot and root growth of lettuce was recorded and nutrient accumulation in lettuce was analyzed after 14 days. Compared to the control treatment, the soil and plant analyzer development value, shoot fresh weight, shoot dry weight, and leaf area were significantly greater (P < 0.05) in 20 mg C L–1 DOM concentration, while the maximum leaf width was significantly higher (P < 0.05) in 10 mg C L–1 DOM concentration. The root fresh weight, root dry weight, root length, root surface area, and number of lateral roots were significantly greater (P < 0.05) in 20 mg C L–1 DOM concentration than in the control treatment. DOM concentrations of 20 and/or 10 mg C L–1 also resulted in enhanced carbon, phosphorus, potassium, sulfur, silicon, and boron contents in lettuce. Overall, these findings suggest that ROC-derived DOM can promote growth and nutrient accumulation in lettuce seedlings, with 20 and/or 10 mg C L–1 being suitable concentrations.

DOI： 10.1515/opag-2022-0397

Rice Yield and Grain Quality under Fluctuating Soil Moisture Stress

Deshabandu, KHST; Noda, Y; Marcelo, VAC; Ehara, H; Inukai, Y; Kano-Nakata, M

AGRONOMY-BASEL 14 巻 ( 9 ) 2024年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Agronomy

In rainfed lowlands and water-saving cultivation systems, rice plants are often exposed to soil moisture fluctuation (SMF). Improving yield as well as grain quality is the main target for breeding under water-stressed environments. This study investigated the effects of different water treatment on yield, growth parameters, and grain quality under field conditions in Japan for 2 years. Two rice genotypes, Nipponbare (japonica) and G3-3 (derived from Nipponbare and KDML105, indica), were grown under continuous waterlogging (CWL) and SMF conditions. As the grain quality characteristics, grain appearance, dimension, and taste parameters were evaluated as well as yield and yield components. SMF reduced the yield, and G3-3 showed a higher yield than Nipponbare under SMF, which was attributed to the higher number of spikelets per panicle. G3-3 showed a better taste score (mark) with lower protein and amylose contents compared to Nipponbare. However, G3-3 had a higher percentage of broken grains, indicating a trade-off in grain quality traits. Non-structural carbohydrate dynamics may be involved as one of the grain quality characteristics. G3-3 demonstrated a superior yield under SMF conditions and have potential to show superior grain quality, indicating that the introgressed segments of G3-3 may be responsible for the grain quality traits associated with root plasticity.

DOI： 10.3390/agronomy14091926

Nitrogen-fixing bacterial community in sago palm roots in different soil environments of East Malaysia and South Thailand Open Access

SAGO PALM 32 巻 ( 1 ) 頁： 15 - 29 2024年9月

Dipping vigorous seedling roots in phosphorus-enriched slurry at transplanting efficiently increases lowland rice yields

Rakotoarisoa, NM; Tsujimoto, Y; Oo, AZ; Tashiro, T; Kano-Nakata, M; Ehara, H

CROP AND ENVIRONMENT 2 巻 ( 4 ) 頁： 202 - 208 2023年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Crop and Environment

P-dipping refers to the placement of phosphorus (P) fertilizer at the root system during transplanting of rice by adhering P-enriched slurry to the seedling roots. This approach is beneficial for smallholder farmers in sub-Saharan Africa who apply small amounts of P to highly P-fixing soils. This study aimed to identify the optimum seedling age for maximizing the impact of P-dipping. Pot experiments revealed that the adhered amounts of slurry to the roots with P-dipping increased in a sigmoidal pattern against seedling age. Correspondingly, the effect of P-dipping on the initial biomass was enlarged with older seedlings in a sigmoidal pattern, increasing slowly during the young seedling age (2.9–4.5 leaves), sharply during the intermediate seedling age (4.5–6.3 leaves), and plateauing during the old seedling age (6.3–7.0 leaves). Combining P-dipping with much older seedlings (> 7.0 leaves) resulted in severe transplanting shock and plant death. On-farm trials on 90 fields in Madagascar demonstrated a significant interaction between seedling age and P treatment on grain yield. The highest yield gains over the control from P-dipping were observed in seedlings with intermediate age (1.0 t ha−1), followed by old (0.7 t ha−1) and young (0.6 t ha−1) seedlings. These results suggested that vigorous and intermediate seedlings with higher slurry adherence than young seedlings and a lower risk of transplanting shock than old seedlings benefited most from P-dipping. This finding provides smallholder farmers with practical knowledge on how to apply the P-dipping more efficiently for achieving improved P management for sustainable rice production.

DOI： 10.1016/j.crope.2023.10.002

Specialty Rice (Oryza sativa L.) with High and Stable Grain Yield under Rainfed Lowland Conditions

Agustin, AML; Ordonio, JL; Natividad, MBS; Lucob-Agustin, NB; Suralta, RR; Ehara, H; Mitsuya, S; Kano-Nakata, M

AGRICULTURE-BASEL 13 巻 ( 10 ) 2023年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Agriculture (Switzerland)

This study aimed to identify superior genotypes of specialty rice (SR) with comparable or higher grain yield than the drought-tolerant check variety under rainfed and controlled-drought conditions. A total of 17 SR varieties (six aromatic, six pigmented, five glutinous) and a drought-tolerant check variety with ordinary grain quality were evaluated under rainfed lowland and controlled-drought conditions from 2019 to 2021 at Central Luzon State University in the Philippines. Among the SR varieties, aromatic NSIC Rc344, pigmented Black rice, and glutinous NSIC Rc15 had comparable or higher grain yield than the drought-tolerant check variety under both rainfed and controlled-drought conditions. These selected genotypes were classified as the highest yielding, with a more stable yield than the drought-tolerant check variety across the hydrological conditions based on the BLUPs productivity and stability test and drought tolerance indices. The selected SR varieties had a greater panicle number (NSIC Rc344), more grains per panicle (NSIC Rc15), and a higher 1000-grain weight and harvest index (Black rice). In comparison to a higher yield but with a higher market price due to the superior grain quality of the identified SR than the drought-tolerant check variety, the net income in rainfed lowland conditions significantly increased by 69–108%. These results suggest that planting good-performing SR in rainfed lowlands can increase profitability in this ecosystem due to the higher market price compared to ordinary drought-tolerant varieties.

DOI： 10.3390/agriculture13101985

Growth Performance of Photoperiod-Sensitive Rice (<i>Oryza sativa</i> L.) Varieties in Different Soil Types under Rainfed Condition in Cambodia

Uch, C; Roeurn, S; Ro, S; Kano-Nakata, M; Yamauchi, A; Ehara, H

AGRICULTURE-BASEL 13 巻 ( 8 ) 2023年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Agriculture (Switzerland)

In Cambodia, rice is predominantly produced in areas with rainfed lowland conditions where photoperiod-sensitive varieties are cultivated. A number of varieties have been released for rainfed lowland areas, and the rice grain yield has reportedly increased by approximately 12% over the past ten years. Moreover, great fluctuations in yield performance have been observed across different soil types of the rainfed ecosystems of Cambodia. Therefore, the present study aimed to analyze the grain yield and stability among ten popular varieties that were released for rainfed lowland ecosystems across the four different soil types in Cambodia in two years. The grain yield varied 566 g m−2 as the highest in clay soil and about 220 g m−2 as the lowest in sandy soil. A combined ANOVA revealed significant differences for the main effect of genotype, environment, and genotype-by-environment interaction (GEI) for all yield-related traits and grain yield per square meter. The principal component test results showed that the heterogeneity of grain yield was mainly attributable to the effect of environment, followed by the effect of genotype. In fertile conditions, a higher percentage of filled grains was supported by higher leaf N until the late stage with a wider flag leaf. In conditions of moderate fertility, larger numbers of panicles were supported by a higher percentage of productive culms with higher leaf N until the late stage. In conditions of poor fertility, a higher percentage of filled grains was supported by higher leaf N until the late stage, which is considered to be important for higher grain yield. The variety Phka Rumduol showed these preferable traits and produced higher yields in fertile to poor natural soil fertility conditions with moderate variation. This variety is considered to be more desirable and ideal due to its stability and higher grain yield. The other varieties, namely, Phka Mealdei, Phka Rumdeng, and CAR4, were identified as above-average yielders. Therefore, those varieties potentially may be recommended for cultivation in rainfed lowland rice ecosystems in Cambodia due to their high yields. CAR4 showed moderate variation at the same level as Phka Rumduol. From the point of stability, Phka Rumduol and CAR4 can be expected to excel.

DOI： 10.3390/agriculture13081602

Dry Matter Production of Two Rice Cultivars with Contrasting Root Plasticity Expression Under Different Topographic Conditions Subjected to Soil Moisture Fluctuation

Owusu-Nketia, S; Suralta, RR; Inukai, Y; Mitsuya, S; Kano-Nakata, M; Ofori, PA; Nguyen, DTN; Yamauchi, A

PHILIPPINE AGRICULTURAL SCIENTIST 106 巻 ( 2 ) 頁： 131 - 142 2023年6月

The <i>outstanding rooting1</i> mutation gene maintains shoot growth and grain yield through promoting root development in rice under water deficit field environments 査読有り国際共著

Hasegawa, T; Wainaina, CM; Shibata, A; Lucob-Agustin, N; Makihara, D; Kikuta, M; Menge, DM; Gichuhi, EW; Samejima, H; Kano-Nakata, M; Kimani, JM; Musila, RN; Yamauchi, A; Inukai, Y

JOURNAL OF AGRONOMY AND CROP SCIENCE 208 巻 ( 6 ) 頁： 815 - 829 2022年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Agronomy and Crop Science

Drought is one of the most serious constraints to rice cultivation, even under alternate wetting and drying (AWD), which is a water-saving management practice. In rice, enhanced root development is essential for stable shoot growth, adaptability and productivity under water deficit environments. We identified and characterized outstanding rooting1 (our1) rice mutant using hydroponics. The present study sought to examine morphological root traits of the our1 mutant and the role of the mutation gene in shoot growth and yield under AWD. Thus, we evaluated the growth performance of the our1 rice mutant in pot experiments and under field AWD conditions in Kenya. The experiments were conducted with our1 mutant, its wild type and their progenies under both AWD and continuously waterlogged (CWL) conditions. The our1 mutant possessed a well-developed root system and exhibited particularly enhanced thin root development, which was maintained from the early vegetative stage through the reproductive stage under both pot and field AWD management. This enhanced root development promoted shoot growth through increased water uptake during rewatered conditions between drought periods in AWD. In addition, the our1 mutant showed enhanced shoot growth during the reproductive stage, resulting in the maintenance of yield under AWD fields. Genotypes harbouring our1 mutation gene showed higher yields compared to wild-type genotypes which was attributed to their higher photosynthetic ability as a result of enhanced root activity. These results suggest the important role of a well-developed root system architecture and enhanced root function in stabilizing rice yields under water-limited environments. Our findings indicate that the our1 mutation gene can serve as a novel breeding material to mitigate the impact of transient drought stress on yield under AWD.

DOI： 10.1111/jac.12524

Grain Yield and Gross Return above Fertilizer Cost with Parameters Relating to the Quality of White Rice Cultivated in Rainfed Paddy Fields in Cambodia

Khema, S; Rin, S; Fujita, A; Kong, K; Ngin, C; Kano-Nakata, M; Yamauchi, A; Ehara, H

SUSTAINABILITY 14 巻 ( 17 ) 2022年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Sustainability (Switzerland)

This study aims to compare the grain yield, gross return above fertilizer cost (GRAFC: (paddy sales)–(fertilizer cost)), and several parameters relating to the quality of white rice cultivated with different soil-specific nutrient management in 14 provinces where different soil types are distributed. The grain yield tended to increase with increased fertilizer application; however, the relationship between the fertilization rate and the yield was not linear in areas where clay soil dominates. In cases of popular varieties cultivated from the northern to southern province, the amount of fertilizer applied was up to 163 kg ha−1 (sum of N-P2O5-K2O), and the GRAFC and the fertilization rate showed a nonlinear relationship, with a peak of around 120 kg ha−1 fertilization. The nitrogen concentration recognized as a negative factor for the quality of rice tended to increase with an increasing fertilization rate, and the carbohydrate concentration and carbohydrate/protein ratio that are a positive factor for the quality were related negatively with the fertilizer rate. The amylopectin concentration in white rice was positively related with the carbohydrate concentration, which decreased with an increasing fertilization rate. The levels of fertilizer application required to achieve a higher yield, GRAFC, and the maintenance and improvement of parameters relating to grain quality were different.

DOI： 10.3390/su141710708

Waterlogged Conditions Influence the Nitrogen, Phosphorus, Potassium, and Sugar Distribution in Sago Palm (<i>Metroxylon sagu</i> Rottb.) at Seedling Stages

Azhar, A; Asano, K; Sugiura, D; Kano-Nakata, M; Ehara, H

PLANTS-BASEL 11 巻 ( 5 ) 2022年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plants

Sago palm (Metroxylon sagu Rottb.) grows in well-drained mineral soil and in peatland with high groundwater levels until complete submersion. However, the published information on nutrient uptake and carbohydrate content in sago palms growing under waterlogging remains un-reported. This experiment observed sago palm growth performance under normal soil conditions (non-submerged conditions) as a control plot and extended waterlogged conditions. Several parameters were analyzed: Plant morphological growth traits, nitrogen, phosphorus, potassium, and sugar concentration in the plant organ, including sucrose, glucose, starch, and non-structural car-bohydrate. The analysis found that sago palm morphological growth traits were not significantly affected by extended waterlogging. However, waterlogging reduced carbohydrate levels in the up-per part of the sago palm, especially the petiole, and increased sugar levels, especially glucose, in roots. Waterlogging also reduced N concentration in roots and leaflets and P in petioles. The K level was independent of waterlogging as the sago palm maintained a sufficient level in all of the plant organs. Long duration waterlogging may reduce the plant’s economic value as the starch level in the trunk decreases, although sago palm can grow while waterlogged.

DOI： 10.3390/plants11050710

<i>WUSCHEL</i>-<i>related</i> <i>homeobox</i> family genes in rice control lateral root primordium size

Kawai, T; Shibata, K; Akahoshi, R; Nishiuchi, S; Takahashi, H; Nakazono, M; Kojima, T; Nosaka-Takahashi, M; Sato, Y; Toyoda, A; Lucob-Agustin, N; Kano-Nakata, M; Suralta, RR; Niones, JM; Chen, YL; Siddique, KHM; Yamauchi, A; Inukai, Y

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 119 巻 ( 1 ) 2022年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Proceedings of the National Academy of Sciences of the United States of America

The development of a plastic root system is essential for stable crop production under variable environments. Rice plants have two types of lateral roots (LRs): S-type (short and thin) and L-type (long, thick, and capable of further branching). LR types are determined at the primordium stage, with a larger primordium size in L-types than S-types. Despite the importance of LR types for rice adaptability to variable water conditions, molecular mechanisms underlying the primordium size control of LRs are unknown. Here, we show that two WUSCHEL-related homeobox (WOX) genes have opposing roles in controlling LR primordium (LRP) size in rice. Root tip excision on seminal roots induced L-type LR formation with wider primordia formed from an early developmental stage. QHB/OsWOX5 was isolated as a causative gene of a mutant that is defective in S-type LR formation but produces more L-type LRs than wild-type (WT) plants following root tip excision. A transcriptome analysis revealed that OsWOX10 is highly up-regulated in L-type LRPs. OsWOX10 overexpression in LRPs increased the LR diameter in an expression-dependent manner. Conversely, the mutation in OsWOX10 decreased the L-type LR diameter under mild drought conditions. The qhb mutants had higher OsWOX10 expression than WT after root tip excision. A yeast one-hybrid assay revealed that the transcriptional repressive activity of QHB was lost in qhb mutants. An electrophoresis mobility shift assay revealed that OsWOX10 is a potential target of QHB. These data suggest that QHB represses LR diameter increase, repressing OsWOX10. Our findings could help improve root system plasticity under variable environments.

DOI： 10.1073/pnas.2101846119

Utilization of Sensing and Image-processing Devices for Evaluating the Grain Quality of Cambodian Rice Varieties

SRUN Khema, FUJITA Akiko, KONG Kea, NGIN Chhay, NEOU Ratana, ASANO Koki, AUDIA Fitri, YAMADA Shuto, KANO-NAKATA Mana, YAMAUCHI Akira, TASHIRO Toru, EHARA Hiroshi

Tropical Agriculture and Development 66 巻 ( 4 ) 頁： 139 - 149 2022年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Society for Tropical Agriculture

<p>The export of Cambodian milled rice to the international market has been increasing in volume remarkably. Consumer demands for rice in terms of cooking and eating quality are different from country to county. To contribute to the promotion of Cambodian rice exports, evidence-based information about rice quality is very important. This study aims to compare the quality of eight rice samples including six different indica lowland rice varieties from different producers/suppliers in Cambodia. Some sensing equipment analyzers such as a grain scanner (image-processing device), a rice taste analyzer for white rice, and a taste analyzer unit for cooked rice that measures freshness, hardness, and stickiness using a near-infrared transmission sensor were employed with conventional chemical analyses. The percentage of head rice as analyzed by the grain scanner was over 70% in all samples, and they were evaluated as being a higher grade according to the Cambodian standard (≧ 60%). Although the analyzers were developed originally for temperate japonica, short-grain rice varieties, the taste mark detected by the analyzer for white rice showed a negative relationship with the protein and amylose content in white rice. The taste value detected by the analyzer unit for cooked rice showed a highly negative relationship with the nitrogen concentration in white rice and a highly positive relationship with the carbon/nitrogen concentration ratio—the C/N ratio—in white rice and the stickiness/hardness ratio in cooked rice.</p>

DOI： 10.11248/jsta.66.139

Arbuscular Mycorrhizal Communities in the Roots of Sago Palm in Mineral and Shallow Peat Soils

Asano, K; Kagong, WVA; Mohammad, SMB; Sakazaki, K; Abu Talip, MS; Sahmat, SS; Chan, MKY; Isoi, T; Kano-Nakata, M; Ehara, H

AGRICULTURE-BASEL 11 巻 ( 11 ) 2021年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Agriculture (Switzerland)

Communities of arbuscular mycorrhizal fungi (AMF) in plant roots improve host plant growth. In this study, AMF communities in the roots of the sago palm (Metroxylon sagu Rottb.) were investigated in mineral soil (MS) and shallow peat soil (SPS) in Sarawak, Malaysia. MS exhibited lower moisture content (MS, 38.1; SPS, 79.8%), higher pH (H2 O) (MS, 4.6; SPS, 4.1), higher soil bulk density (MS, 1.03; SPS, 0.20 g cm−3 ), and higher nitrogen content (MS, 16.9; SPS, 2.7 kg m−3 ) than SPS at the same soil depth, while the phosphorus (P) content (Bray II) (MS, 1.6; SPS, 1.9 g P2 O5 m−3 ) was similar. The AMF colonization rate was significantly lower in SPS (39.2 ± 12.5%) than in MS (73.2 ± 4.6%). The higher number of AMF operational taxonomic units (OTUs) was detected by amplicon sequencing of the partial small-subunit rRNA gene (MS, 78; SPS, 50). A neighbor-joining tree of obtained OTUs revealed that they belonged to Acaulosporaceae, Ambisporaceae, Claroideoglomeraceae, Gigasporaceae, and Glomeraceae. The lower abundance and diversity of AMF in SPS are possibly caused by abiotic factors, including soil physicochemical properties. Glomus and Acaulospora species detected in SPS might have strong tolerance against acidity and high soil moisture content.

DOI： 10.3390/agriculture11111161

Mutation of OUR1/OsbZIP1, which encodes a member of the basic leucine zipper transcription factor family, promotes root development in rice through repressing auxin signaling 査読有り国際誌

Hasegawa, T; Lucob-Agustin, N; Yasufuku, K; Kojima, T; Nishiuchi, S; Ogawa, A; Takahashi-Nosaka, M; Kano-Nakata, M; Inari-Ikeda, M; Sato, M; Tsuji, H; Wainaina, CM; Yamauchi, A; Inukai, Y

PLANT SCIENCE 306 巻頁： 110861 - 110861 2021年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plant Science

A well-developed root system is essential for efficient water uptake, particularly in drought-prone environments. However, the molecular mechanisms underlying the promotion of root development are poorly understood. We identified and characterized a rice mutant, outstanding rooting1 (our1), which exhibited a well-developed root system. The our1 mutant displayed typical auxin-related phenotypes, including elongated seminal root and defective gravitropism. Seminal root elongation in the our1 mutant was accelerated via the promotion of cell division and elongation. In addition, compared with the wild type, the density of short and thin lateral roots (S-type LRs) was reduced in the our1 mutant, whereas that of long and thick LRs (L-type LRs) was increased. Expression of OUR1, which encodes OsbZIP1, a member of the basic leucine zipper transcription factor family, was observed in the seminal root tip and sites of LR emergence, wherein attenuation of reporter gene expression levels controlled by the auxin response promoter DR5 was also observed in the our1 mutant. Taken together, our results indicate that the our1 gene promotes root development by suppressing auxin signaling, which may be a key factor contributing to an improvement in root architecture.

DOI： 10.1016/j.plantsci.2021.110861

Root system characteristics under different water regimes in three cereal species 査読有り国際共著

Natsumi Ueda, Shiro Mitsuya, Akira Yamauchi, Maria Corazon J. Cabral and Mana Kano-Nakata

PLANT ROOT 15 巻頁： 9 - 17 2021年4月

Morpho-physiological and molecular mechanisms of phenotypic root plasticity for rice adaptation to water stress conditions

Lucob-Agustin, N; Kawai, T; Kano-Nakata, M; Suralta, RR; Niones, JM; Hasegawa, T; Inari-Ikeda, M; Yamauchi, A; Inukai, Y

BREEDING SCIENCE 71 巻 ( 1 ) 頁： 20 - 29 2021年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：日本育種学会

Different types of water stress severely affect crop production, and the plant root system plays a critical role in stress avoidance. In the case of rice, a cereal crop cultivated under the widest range of soil hydrologic conditions, from irrigated anaerobic conditions to rainfed conditions, phenotypic root plasticity is of particular relevance. Recently, important plastic root traits under different water stress conditions, and their physiological and molecular mechanisms have been gradually understood. In this review, we summarize these plastic root traits and their contributions to dry matter production through enhancement of water uptake under different water stress conditions. We also discuss the physiological and molecular mechanisms regulating the phenotypic plasticity of root systems.

DOI： 10.1270/jsbbs.20106

The <i>promoted lateral root 1</i> (<i>plr1</i>) mutation is involved in reduced basal shoot starch accumulation and increased root sugars for enhanced lateral root growth in rice 国際誌

Lucob-Agustin, N; Sugiura, D; Kano-Nakata, M; Hasegawa, T; Suralta, RR; Niones, JM; Inari-Ikeda, M; Yamauchi, A; Inukai, Y

PLANT SCIENCE 301 巻頁： 110667 - 110667 2020年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plant Science

Lateral roots (LRs) are indispensable for plant growth, adaptability and productivity. We previously reported a rice mutant, exhibiting a high density of thick and long LRs (L-type LRs) with long parental roots and herein referred to as promoted lateral root1 (plr1). In this study, we describe that the mutant exhibited decreased basal shoot starch accumulation, suggesting that carbohydrates might regulate the mutant root phenotype. Further analysis revealed that plr1 mutation gene regulated reduced starch accumulation resulting in increased root sugars for the regulation of promoted LR development. This was supported by the exogenous glucose application that promoted L-type LRs. Moreover, nitrogen (N) application was found to reduce basal shoot starch accumulation in both plr1 mutant and wild-type seedlings, which was due to the repressed expression of starch biosynthesis genes. However, unlike the wild-type that responded to N treatment only at seedling stage, the plr1 mutant regulated LR development under low to increasing N levels, both at seedling and higher growth stages. These results suggest that plr1 mutation gene is involved in reduced basal shoot starch accumulation and increased root sugar level for the promotion of L-type LR development, and thus would be very useful in improving rice root architecture.

DOI： 10.1016/j.plantsci.2020.110667

A GWAS approach to find SNPs associated with salt removal in rice leaf sheath

Neang, S; de Ocampo, M; Egdane, JA; Platten, JD; Ismail, AM; Seki, M; Suzuki, Y; Skoulding, NS; Kano-Nakata, M; Yamauchi, A; Mitsuya, S

ANNALS OF BOTANY 126 巻 ( 7 ) 頁： 1193 - 1202 2020年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Annals of Botany

Background and Aims: The ability for salt removal at the leaf sheath level is considered to be one of the major mechanisms associated with salt tolerance in rice. Thus, understanding the genetic control of the salt removal capacity in leaf sheaths will help improve the molecular breeding of salt-tolerant rice varieties and speed up future varietal development to increase productivity in salt-affected areas. We report a genome-wide association study (GWAS) conducted to find single nucleotide polymorphisms (SNPs) associated with salt removal in leaf sheaths of rice. Methods: In this study, 296 accessions of a rice (Oryza sativa) diversity panel were used to identify salt removal-related traits and conduct GWAS using 36 901 SNPs. The sheath:blade ratio of Na+ and Cl- concentrations was used to determine the salt removal ability in leaf sheaths. Candidate genes were further narrowed via Gene Ontology and RNA-seq analysis to those whose putative function was likely to be associated with salt transport and were up-regulated in response to salt stress. Key results: For the association signals of the Na+ sheath:blade ratio, significant SNPs were found only in the indica sub-population on chromosome 5. Within candidate genes found in the GWAS study, five genes were upregulated and eight genes were downregulated in the internal leaf sheath tissues in the presence of salt stress. Conclusions: These GWAS data imply that rice accessions in the indica variety group are the main source of genes and alleles associated with Na+ removal in leaf sheaths of rice under salt stress.

DOI： 10.1093/aob/mcaa139

Tissue-specific expression analysis of Na<SUP>+</SUP> and Cl<SUP>-</SUP> transporter genes associated with salt removal ability in rice leaf sheath 国際誌

Neang, S; Goto, I; Skoulding, NS; Cartagena, JA; Kano-Nakata, M; Yamauchi, A; Mitsuya, S

BMC PLANT BIOLOGY 20 巻 ( 1 ) 頁： 502 - 502 2020年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：BMC Plant Biology

Background: A significant mechanism of salt-tolerance in rice is the ability to remove Na+ and Cl− in the leaf sheath, which limits the entry of these toxic ions into the leaf blade. The leaf sheath removes Na+ mainly in the basal parts, and Cl− mainly in the apical parts. These ions are unloaded from the xylem vessels in the peripheral part and sequestered into the fundamental parenchyma cells at the central part of the leaf sheath. Results: This study aimed to identify associated Na+ and Cl− transporter genes with this salt removal ability in the leaf sheath of rice variety FL 478. From 21 known candidate Na+ and Cl− transporter rice genes, we determined the salt responsiveness of the expression of these genes in the basal and apical parts, where Na+ or Cl− ions were highly accumulated under salinity. We also compared the expression levels of these transporter genes between the peripheral and central parts of leaf sheaths. The expression of 8 Na+ transporter genes and 3 Cl− transporter genes was up-regulated in the basal and apical parts of leaf sheaths under salinity. Within these genes, OsHKT1;5 and OsSLAH1 were expressed highly in the peripheral part, indicating the involvement of these genes in Na+ and Cl− unloading from xylem vessels. OsNHX2, OsNHX3, OsNPF2.4 were expressed highly in the central part, which suggests that these genes may function in sequestration of Na+ and Cl− in fundamental parenchyma cells in the central part of leaf sheaths under salinity. Furthermore, high expression levels of 4 candidate genes under salinity were associated with the genotypic variation of salt removal ability in the leaf sheath. Conclusions: These results indicate that the salt removal ability in rice leaf sheath may be regulated by expressing various Na+ or Cl− transporter genes tissue-specifically in peripheral and central parts. Moreover, some genes were identified as candidates whose expression levels were associated with the genotypic variation of salt removal ability in the leaf sheath. These findings will enhance the understanding of the molecular mechanism of salt removal ability in rice leaf sheath, which is useful for breeding salt-tolerant rice varieties.

DOI： 10.1186/s12870-020-02718-4

Plasticity in Nodal Root Hardpan Penetration, Deep Soil Water Uptake, and Shoot Dry Matter Production under Soil Moisture Fluctuations Using Chromosome Segment Substitution Lines of Rice

Nguyen, DTN; Suralta, RR; Kano-Nakata, M; Mitsuya, S; Owusu-Nketia, S; Yamauchi, A

PHILIPPINE AGRICULTURAL SCIENTIST 103 巻 ( 3 ) 頁： 214 - 234 2020年9月

<i>WEG1</i>, which encodes a cell wall hydroxyproline-rich glycoprotein, is essential for parental root elongation controlling lateral root formation in rice

Lucob-Agustina, N; Kawai, T; Takahashi-Nosaka, M; Kano-Nakata, M; Wainaina, CM; Hasegawa, T; Inari-Ikeda, M; Sato, M; Tsuji, H; Yamauchi, A; Inukai, Y

PHYSIOLOGIA PLANTARUM 169 巻 ( 2 ) 頁： 214 - 227 2020年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physiologia Plantarum

Lateral roots (LRs) determine the overall root system architecture, thus enabling plants to efficiently explore their underground environment for water and nutrients. However, the mechanisms regulating LR development are poorly understood in monocotyledonous plants. We characterized a rice mutant, wavy root elongation growth 1 (weg1), that produced higher number of long and thick LRs (L-type LRs) formed from the curvatures of its wavy parental roots caused by asymmetric cell growth in the elongation zone. Consistent with this phenotype, was the expression of the WEG1 gene, which encodes a putative member of the hydroxyproline-rich glycoprotein family that regulates cell wall extensibility, in the root elongation zone. The asymmetric elongation growth in roots is well known to be regulated by auxin, but we found that the distribution of auxin at the apical region of the mutant and the wild-type roots was symmetric suggesting that the wavy root phenotype in rice is independent of auxin. However, the accumulation of auxin at the convex side of the curvatures, the site of L-type LR formation, suggested that auxin likely induced the formation of L-type LRs. This was supported by the need of a high amount of exogenous auxin to induce the formation of L-type LRs. These results suggest that the MNU-induced weg1 mutated gene regulates the auxin-independent parental root elongation that controls the number of likely auxin-induced L-type LRs, thus reflecting its importance in improving rice root architecture.

DOI： 10.1111/ppl.13063

Root and shoot responses of upland New Rice for Africa varieties to fluctuating soil moisture conditions as affected by different levels of nitrogen fertilization

Menge, DM; Kano-Nakata, M; Yamauchi, A; Suralta, RR; Makihara, D

JOURNAL OF AGRONOMY AND CROP SCIENCE 206 巻 ( 3 ) 頁： 322 - 337 2020年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Agronomy and Crop Science

Drought cycling and soil re-watering trends due to intermittent rainfall patterns are key stress factors that influence rice growth and yield under upland cultivation conditions. However, upland rice adaptation responses to fluctuating soil moisture conditions remain poorly understood. This study investigated root and shoot responses of upland New Rice for Africa (NERICA) varieties to episodic drought and re-watering during growth. We examined root and shoot growth of NERICA 1 and NERICA 4 compared with those of IR72, an improved lowland variety, and Dular, a traditional drought-tolerant variety, in terms of soil moisture fluctuations with different levels of nitrogen fertilization under field conditions that impeded deep root development. During soil moisture fluctuation, all varieties reduced shoot dry weight compared with well-watered plants, regardless of nitrogen fertilization levels. However, total root length for the three upland varieties was enhanced by soil moisture fluctuations at moderate and high nitrogen fertilization, while that of the lowland variety was reduced. Comparing root development during water fluctuations revealed that NERICA 1 had a greater root system than NERICA 4, which was attributed to lateral root development. Furthermore, we found that NERICA varieties increase lateral root mass during soil desiccation under adequate nitrogen fertilization, while Dular and IR72 reduced their root growth rate during drought and increased it after re-watering. Both root growth patterns developed, from around maximum tillering to heading. The analysis of regression between root elongation and shoot growth with fluctuating soil moisture indicated that an enhanced root system during drought, on adequate nitrogen fertilization, can contribute to shoot growth when sufficient water becomes available, specifically around the maximum tillering to the heading growth stage of rice.

DOI： 10.1111/jac.12390

Enhanced Root System Development Responses of a Newly Identified Mutation Gene Promoting Lateral Root Development to Various Nitrogen Conditions in Rice. 査読有り国際共著

Lucob-Agustin, N., Hasegawa, T., Jinno, K., Suralta, R. R., Niones, J. M., Kano-Nakata, M., Yamauchi, A. and Inukai, Y.

Journal of International Cooperation for Agricultural Development 18 巻頁： 48 - 55 2020年3月

Morphological and histological differences among three types of component roots and their differential contribution to water uptake in the rice root system

Watanabe, Y; Kabuki, T; Kakehashi, T; Kano-Nakata, M; Mitsuya, S; Yamauchi, A

PLANT PRODUCTION SCIENCE 23 巻 ( 2 ) 頁： 191 - 201 2020年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plant Production Science

The rice root system consists of three types of roots; main root, L-type and S-type lateral root (LR). These component roots are morphologically and histologically different, which is termed as heterorhizy. Root system hydraulic architecture is related to the unique features of component roots. We hypothesized that each component root contributes in different degrees to water uptake of the whole root system. Rice varieties IRAT 109 and Taichung 65 were grown in pots filled with soil under continuous waterlogged (CWL) and drought (CD) conditions until two weeks after heading. Morphology and histological structures of roots, which may regulate radial water movement, were compared among the three component roots. Moreover, hydraulic conductivity (Lpr) of the root system, which represents the water uptake ability, were measured with a pressure chamber. Based on a model that Lpr of the whole root system is a product of Lpr of each of the component roots and their surface areas, we found that the differences in Lpr between the two varieties and the plants grown under different soil water conditions for any of the component roots did not support the corresponding differences in the measured Lpr of the whole root system. In contrast, a significant and positive correlation was found between Lpr of the whole root system and the percentage of surface area of S-type LR but not for the other component roots. These results indicate S-type LR might have a higher contribution to Lpr of the whole root system than the other component roots.

DOI： 10.1080/1343943X.2020.1730701

Plasticity in root system architecture of rice genotypes exhibited under different soil water distributions in soil profile

Kano-Nakata, M; Nakamura, T; Mitsuya, S; Yamauchi, A

PLANT PRODUCTION SCIENCE 22 巻 ( 4 ) 頁： 501 - 509 2019年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plant Production Science

The root system architecture (RSA) has been reported to be determined by several root traits such as branching, elongation, and growth angle. This study aimed to evaluate the genotypic variation of plasticity in RSA in response to different soil water distributions in a soil profile. IR64 (shallow root system), YTH183 (adapted to rainfed lowland conditions due to high plasticity in root elongation), and Kinandang Patong (KP–deep root system) were grown in PVC root boxes for 34 days under continuously waterlogged conditions and with soil moisture fluctuations (SMF). For SMF, watering was done from the top of the root box (TI-SMF) or from the bottom of the root box (BI-SMF). A water gradient was observed more clearly in BI-SMF than in TI-SMF, while mean soil moisture content in the root box was kept at around 23% (v/v) after first irrigation in both SMF treatments. RSA changed drastically with SMF in all cultivars, all of which tended to shift root distribution to deeper soil layers in response to SMF. Such changes in RSA resulted from different degrees of plasticity exhibited mainly in nodal root and L-type lateral root development. YTH183 showed a greater ability to change its root growth angle and thus its root distribution in the deeper soil layer compared to IR64 and KP under SMF, indicating that YTH183 could help to improve RSA in cultivars adapted to SMF.

DOI： 10.1080/1343943X.2019.1608836

Evaluation of rice grain yield and yield components of Nona Bokra chromosome segment substitution lines with the genetic background of Koshihikari, in a saline paddy field 国際誌

Mitsuya, S; Murakami, N; Sato, T; Kazama, T; Toriyama, K; Skoulding, NS; Kano-Nakata, M; Yamauchi, A

AOB PLANTS 11 巻 ( 5 ) 頁： plz040 2019年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AoB PLANTS

The ability to tolerate salt differs with the growth stages of rice and thus the yield components that are determined during various growth stages, are differentially affected by salt stress. In this study, we utilized chromosome segment substitution lines (CSSLs) from Nona Bokra, a salt-tolerant indica landrace, with the genetic background of Koshihikari, a salt-susceptible japonica variety. These were screened to find superior CSSLs under long-term saline conditions that showed higher grain yield and yield components in comparison to Koshihikari. One-month-old seedlings were transplanted into a paddy field without salinity. These were allowed to establish for 1 month further, then the field was flooded, with saline water maintained at 7.41 dS m-1 salinity until harvest. The experiments were performed twice, once in 2015 and a targeted study in 2016. Salt tolerance of growth and reproductive stage parameters was evaluated as the Salt Effect Index (SEI) which was computed as the difference in each parameter within each line between control and saline conditions. All CSSLs and Koshihikari showed a decrease in grain yield and yield components except panicle number under salinity. SL538 showed a higher SEI for grain yield compared with Koshihikari under salinity throughout the two experiments. This was attributed to the retained grain filling and harvest index, yet the mechanism was not due to maintaining Na+, Cl- and K+ homeostasis. Few other CSSLs showed greater SEI for grain weight under salinity compared with Koshihikari, which might be related to low concentration of Na+ in leaves and panicles. These data indicate that substitution of different Nona Bokra chromosome segments independently contributed to the maintenance of grain filling and grain weight of Koshihikari under saline conditions.

DOI： 10.1093/aobpla/plz040

'Kasalath' Allele in Nipponbare Background is Responsible for the Plasticity in Lateral Root Development of Rice under Soil Moisture Fluctuation Stress

Niones, JM; Suralta, RR; Inukai, Y; Kano-Nakata, M; Yamauchi, A

PHILIPPINE AGRICULTURAL SCIENTIST 102 巻 ( 3 ) 頁： 188 - 198 2019年9月

Soil Compaction Enhanced the Expression of Root Plasticity, Water and Nitrogen Uptake of Rice under Mild Drought with High N Fertilization

Tran, TT; Suralta, RR; Takeda, M; Mitsuya, S; Kano-Nakata, M; Yamauchi, A

PHILIPPINE AGRICULTURAL SCIENTIST 102 巻 ( 3 ) 頁： 199 - 210 2019年9月

Effect of nitrogen application on the expression of drought-induced root plasticity of upland NERICA rice 査読有り国際共著

Menge, D.M., Onyango, J.C., Yamauchi, A., Kano-Nakata, M., Asanuma, S., Thi, T.T., Inukai, Y., Kikuta, M., Makihara, D.

PLANT PRODUCTION SCIENCE 22 巻 ( 2 ) 頁： 180 - 191 2019年1月

Fundamental parenchyma cells are involved in Na<SUP>+</SUP> and Cl<SUP>-</SUP> removal ability in rice leaf sheath

Neang, S; de Ocampo, M; Egdane, JA; Platten, JD; Ismail, AM; Skoulding, NS; Kano-Nakata, M; Yamauchi, A; Mitsuya, S

FUNCTIONAL PLANT BIOLOGY 46 巻 ( 8 ) 頁： 743 - 755 2019年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Functional Plant Biology

Salt sensitivity in rice plants is associated with the accumulated amount of Na+ and Cl- in shoots and, more significantly, in photosynthetic tissues. Therefore, salt removal ability at the leaf sheath level is an important mechanism of salt tolerance. In the present study we attempted to determine whether rice leaf sheaths excluded Cl- as well as Na+, and to identify the tissues that were involved in the removal ability of both ions. In two rice genotypes, salt-tolerant FL478 and -sensitive IR29, leaf sheaths excluded Na+ and Cl- under NaCl treatment as estimated using their sheath: blade ratios. The sheath: blade ratio of Na+ but not of Cl-, was increased by NaCl treatment. Under NaCl treatment, Na+ concentration was higher in the basal leaf sheath, whereas Cl- concentration was higher in the middle and tip parts. At the tissue level, fundamental parenchyma cells of leaf sheaths retained the highest amounts of Na and Cl when treated with high amount of NaCl. These results imply that the leaf sheath potentially functions to remove excess Na+ and Cl- from xylem vessels in different locations along the axis, with the fundamental parenchyma cells of leaf sheaths being involved in over-accumulation of both Na+ and Cl-.

DOI： 10.1071/FP18318

Root plasticity for maintenance of productivity under abiotic stressed soil environments in rice: Progress and prospects

Suralta, RR; Kano-Nakata, M; Niones, JM; Inukai, Y; Kameoka, E; Tran, TT; Menge, D; Mitsuya, S; Yamauchi, A

FIELD CROPS RESEARCH 220 巻頁： 57 - 66 2018年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Field Crops Research

Roots play a number of important roles in crop adaptation to various abiotic stresses such as water stress. However, traits responsible for such adaptation may differ with environments. This paper reviews recent progress in our research on the functional roles of important root traits. We have been paying special attention to drought as well as to soil moisture fluctuations as prevailing water stresses, and the ability of the plant to change its development as environmental conditions change, which is known as phenotypic plasticity. We have been using various rice accessions/mapping populations such as the OryzaSNP panel, chromosome segment substitution lines (CSSL) derived from a Nipponbare and Kasalath cross, and IR64 introgression lines. The results consistently showed that, in addition to deep roots, the plasticity of root system development is a key trait for plant adaptation to water stress. We found that plasticity in the development of the entire root system as a function of the plasticity in lateral root development is important under progressive drought, while plasticity in lateral root development that is associated with aerenchyma formation is important under transient drought-to-waterlogged conditions. We quantitatively showed the contributions of root plasticity to dry matter production and yield through enhanced water uptake under such water stress. We also identified quantitative trait loci (QTLs) that are responsible for root plasticity. The importance of explicitly characterizing the nature of the stresses in the target areas is discussed in relation with designing an ideal root system, which is a primary requirement to define an actual breeding target for improving productivity in abiotic stress-prone soil environments.

DOI： 10.1016/j.fcr.2016.06.023

Plasticity in nodal root elongation through the hardpan triggered by rewatering during soil moisture fluctuation stress in rice

Suralta, RR; Niones, JM; Kano-Nakata, M; Tran, TT; Mitsuya, S; Yamauchi, A

SCIENTIFIC REPORTS 8 巻 ( 1 ) 頁： 4341 2018年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scientific Reports

Rainfed lowland (RFL) rice fields have hardpans and experience soil moisture fluctuations (SMF) stress, which influence root system development. Here, we clarify the expression and timing of the plasticity in nodal root elongation through the hardpan under SMF and its contribution to shoot growth using a shallow-rooting IR64 and its deep-rooting introgression line, YTH304. Under SMF, soil moisture content had negative relationship with soil penetration resistance, regardless of hardpan bulk densities. YTH304 had greater root system below the hardpan than IR64 in hardpan with 1.50 but not in 1.70 g cm-3 bulk density (BD). YTH304 had greater plasticity in nodal root elongation through the hardpan than IR64 under SMF, which was clearly expressed during rewatering. YTH304 also had greater soil water uptake below the hardpan during drought and greater shoot growth than IR64. The results imply that deep root system development during SMF was due to the plasticity in nodal root elongation through the hardpan expressed during rewatering rather than during drought periods. This is against the long standing belief that active root elongation through the hardpan happens during drought. This also implies a need to revisit current root screening methods to identify rice lines with good hardpan penetration ability.

DOI： 10.1038/s41598-018-22809-5

Functional roles of root plasticity and its contribution to water uptake and dry matter production of CSSLs with the genetic background of KDML105 under soil moisture fluctuation

Owusu-Nketia, S; Siangliw, JL; Siangliw, M; Toojinda, T; Vanavichit, A; Ratsameejanphen, N; Ruangsiri, M; Sriwiset, S; Suralta, RR; Inukai, Y; Mitsuya, S; Kano-Nakata, M; Nguyen, DTN; Takuya, K; Yamauchi, A

PLANT PRODUCTION SCIENCE 21 巻 ( 3 ) 頁： 266 - 277 2018年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plant Production Science

Soil moisture fluctuation (SMF) stress due to erratic rainfall in rainfed lowland (RFL) rice ecosystems negatively affect production. Under such condition, root plasticity is one of the key traits that play important roles for plant adaptation. This study aimed to evaluate root plasticity expression and its functional roles in water uptake, dry matter production and yield under SMF using three chromosome segment substitution lines (CSSLs) with major genetic background of KDML105 and a common substituted segment in chromosome 8. The CSSLs showed greater shoot dry matter production than KDML105 under SMF, which was attributed to the maintenance of stomatal conductance resulting in higher grain yield. The root system development based on total root length of the CSSLs were significantly higher than that of KDML105 due to the promoted production of nodal and lateral roots. These results implied that the common substituted segments in chromosome 8 of the 3 CSSLs may be responsible for the expression of their root plasticity under SMF and contributed to the increase in water uptake and consequently dry matter production and yield. These CSSLs could be used as a good source of genetic material for drought resistance breeding programs targeting rainfed lowland condition with fluctuating soil moisture environments and for further genetic studies to elucidate mechanisms underlying root plasticity.

DOI： 10.1080/1343943X.2018.1477509

Genotypic variations in the plasticity of nodal root penetration through the hardpan during soil moisture fluctuations among four rice varieties

Nguyen, DTN; Suralta, RR; Kano-Nakata, M; Mitsuya, S; Owusu-Nketia, S; Yamauchi, A

PLANT PRODUCTION SCIENCE 21 巻 ( 2 ) 頁： 93 - 105 2018年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plant Production Science

Rainfed lowland rice fields are characterized by soil moisture fluctuations (SMF) and the presence of hardpan that impedes deep rooting and thus limits water extraction from deep soil layer during the periods of drought. In this study, we used rootboxes with three layers; shallow layer, artificial hardpan, and deep and wet layer below the hardpan, to evaluate differences in the plasticity of nodal roots elongation through the hardpan and promote root branching below the hardpan in response to SMF among four rice varieties; Sasanishiki, Habataki, Nipponbare, and Kasalath. Experiments were conducted during the summer and autumn seasons. Plasticity was computed as the difference in root traits within each variety between the SMF and continuously well-watered treatments. In both experiments, Habataki consistently tended to exhibit higher root plasticity than the other three varieties by increasing number of nodal roots that penetrated the hardpan during rewatering period in SMF, when the soil moisture increased and penetration resistance decreased. This root plasticity then contributed to greater water use at the deeper soil during the subsequent drought period and overall shoot dry matter production. Habataki had significantly higher δ13C value in roots at deep layer than roots at the shallow and hardpan layers under SMF, which may indicate that these were relatively newly grown roots as a consequence of root plasticity. This study also indicates that CSSLs derived from Sasanishiki and Habataki varieties may be suitable for the analysis of QTLs associated with root plasticity expression in rainfed lowland with hardpan and experiencing SMF.

DOI： 10.1080/1343943X.2018.1439757

Root plasticity under fluctuating soil moisture stress exhibited by backcross inbred line of a rice variety, Nipponbare carrying introgressed segments from KDML105 and detection of the associated QTLs

Owusu-Nketia, S; Inukai, Y; Ohashi, S; Suralta, RR; Doi, K; Mitsuya, S; Kano-Nakata, M; Niones, JM; Nguyen, DTN; Takuya, K; Makihara, D; Yamauchi, A

PLANT PRODUCTION SCIENCE 21 巻 ( 2 ) 頁： 106 - 122 2018年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Plant Production Science

In rainfed lowland rice ecosystem, rice plants are often exposed to alternating recurrences of waterlogging and drought due to erratic rainfall. Such soil moisture fluctuation (SMF) which is completely different from simple or progressive drought could be stressful for plant growth, thereby causing reduction in yield. Root plasticity is one of the key traits that play important roles for plant adaptation under such conditions. This study aimed to evaluate root plasticity expression and its functional roles in dry matter production and yield under SMF using Nipponbare, KDML 105 and three backcross inbred lines (BILs) and to identify QTL(s) associated with root traits in response to SMF at two growth stages using Nipponbare/KDML105 F2 plants. A BIL, G3-3 showed higher shoot dry matter production and yield than Nipponbare due to its greater ability to maintain stomatal conductance concomitant with greater root system development caused by promoted production of nodal and lateral roots under SMF. QTLs were identified for total nodal root length, total lateral root length, total root length, number of nodal roots, and branching index under SMF at vegetative and reproductive stages. The QTLs detected at vegetative and reproductive stages were different. We discuss here that relationship between root system of G3-3 and the detected QTLs. Therefore, G3-3 and the identified QTLs could be useful genetic materials in breeding program for improving the adaptation of rice plants in target rainfed lowland areas.

DOI： 10.1080/1343943X.2018.1446759

Quantitative evaluation of plastic root responses to contiguous water gradient in rice 査読有り

Kano-Nakata M., Inukai Y., Siopongco J.D.L.C., Mitsuya S., Yamauchi A.

Plant Root 11 巻 ( 0 ) 頁： 70 - 78 2017年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：根研究学会

Root plasticity is the key trait for plant adaptation to environmental stresses. To quantify phenotypic plasticity to its full extent in potential, it needs to be evaluated under contiguous environmental changes. For that purpose, we used the combination of chromosome segment substitution lines (Nipponbare/Kasalath CSSLs) and line source sprinkler (LSS) system of irrigation. For analysis, we first attempted to apply the coefficient of variation (CV) and norm of reaction that have been used as the conventional approaches, and then propose a new approach for quantification of root plasticity. Results revealed that CV was not linked to root plasticity under contiguous water gradient in this study. In contrast, norm of reaction was linked to root plasticity and better explained with curve than linear, especially for CSSL50 (the most plastic genotypes) under such gradient. Based on the norm of reaction with curve, root plasticity was calculated using the difference in total root length between CSSLs and the recurrent parent, Nipponbare. Further analysis of root plasticity in relation to dry matter production was also done. By applying the new approach, we confirmed that root plasticity expression was affected by the intensities of drought stress and genotypes, indicating that such root plasticity is genetically controlled. In addition, root plasticity effectively contributed to the dry matter production under the drought conditions and maximized at around 20% of soil moisture content (–0.04 MPa). By using CSSLs and LSS system, we successfully evaluated root plasticity under contiguous water gradient.

DOI： 10.3117/plantroot.11.70

Rice cultivation in Bangladesh: present scenario, problems, and prospects 招待有り査読有り国際共著

Shelley, I. J., Takahashi-Nosaka, M., Kano-Nakata, M., Haque, M. S., and Inukai, Y.

Journal of International Cooperation in Agricultural Development 14 巻頁： 20 - 29 2016年3月

Drought-induced root plasticity of two upland NERICA varieties under conditions with contrasting soil depth characteristics. 査読有り国際共著

Menge, D.M., Kameoka, E., Kano-Nakata, M., Yamauchi, A., Asanuma, S., Asai, H., Kikuta, M., Suralta, R.R., Koyama, T., Tran, T.T., Siopongco, J.D.L.C., Mitsuya, S., Inukai, Y. and Makihara, D.

Plant Production Science 19 巻頁： 389 - 400 2016年

Evaluation of Cold Tolerance in NERICAs Compared with Japanese Standard Rice Varieties at the Reproductive Stage 査読有り国際共著

C. M. Wainaina, Y. Inukai, P. W. Masinde, E. M. Ateka, H. Murage, M. Kano-Nakata, Y. Nakajima, T. Terashima, Y. Mizukami, M. Nakamura, T. Nonoyama, N. Saka, S. Asanuma, A. Yamauchi, H. Kitano, J. Kimani and D. Makihara

Journal of Agronomy and Crop Science 201 巻頁： 461 - 472 2015年

Root plasticity and its functional roles were triggered by water deficit but not by the resulting changes in the forms of soil N in rice 査読有り国際共著

Thiem Thi Tran, Mana Kano-Nakata, Roel Rodriguez Suralta, Daniel Menge, Shiro Mitsuya, Yoshiaki Inukai and Akira Yamauchi

Plant and Soil 386 巻頁： 65 - 76 2015年

Effect of Various Intensities of Drought Stress on δ13C Variation among Plant Organs in Rice: Comparison of Two Cultivars 査読有り国際共著

Kano-Nakata, M. , Tatsumi, J. , Inukai, Y. , Asanuma, S. and Yamauchi, A.

American Journal of Plant Sciences 5 巻頁： 1686 - 1693 2014年5月

Nitrogen application enhanced the expression of developmental plasticity of root system triggered by mild drought stress in rice 査読有り国際共著

Thiem Thi Tran, Mana Kano-Nakata, Moe Takeda, Daniel Menge, Shiro Mitsuya, Yoshiaki Inukai and Akira Yamauchi

Plant and Soil 378 巻頁： 139 - 152 2014年

Functional roles of the plasticity of root system development in biomass production and water uptake under rainfed lowland conditions 査読有り国際共著

Kano-Nakata, M., Gowda, V.R.P., Henry, A., Serraj, R., Inukai, Y., Fujita, D., Kobayashi, N., Suralta, R.R. and Yamauchi, A.

Field Crops Research 144 巻頁： 288 - 296 2013年

Enhanced nitrogen uptake and photosynthesis of rice grown with deep and permanent irrigation method: Possible mechanism for chalky grain reduction. 査読有り

Hayashi, M., Hayashi, T., Kuno, C., Tani, T., Endo, I., Higashino, A., Kano-Nakata, M. and Yamauchi, A.

Plant Production Science 16 巻頁： 309 - 316 2013年

Root plasticity as the key root trait for adaptation to various intensities of drought stress water stresses in rice. 査読有り

Kano, M., Inukai, Y., Kitano, H. and Yamauchi, A.

Plant and Soil 342 巻頁： 117-128 2011年

Root development and water uptake, and shoot dry matter production under water deficit conditions in two CSSLs of rice: Functional roles of root plasticity. 査読有り国際共著

Kano-Nakata, M., Inukai, Y., Wade, J.L., Siopongco, J.D.L.C. and Yamauchi, A.

Plant Production Science 14 巻頁： 307-317 2011年

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