Deepwater Rice Research Articles

Optimization of Vitamin B1, B2, and B6 Absorption in Nang Tay Dum Floating Rice Grains.

As reported by the FAO, in 2022, approximately 735 million people experienced undernourishment, underscoring the critical need for effective strategies to address micronutrient deficiencies. Among these strategies, the mass fortification of staple foods, particularly rice-a dietary staple for half of the global population-has emerged as one of the most effective approaches. Conventional milling processes diminish the nutritional content of rice, necessitating the development of fortification methods to enhance its nutrient profile. This study investigates advanced fortification techniques to improve the nutritional value of rice, focusing on vitamins B1, B2, and B6, with guidelines from the US Institute of Medicine's Dietary Reference Intakes. The results indicate that implementing ultrasonic treatments and optimal soaking conditions (60 °C for 60 min) significantly enhances the absorption of these vitamins. Effective parameters included a concentration of 1500 ppm for vitamin B1 and higher levels for vitamins B2 and B6, with a rice-to-vitamin solution ratio of 1:4. These conditions yielded an absorbed vitamin B1 content of 1050 mg/kg, bringing the fortified rice closer to meeting recommended intake levels. Given the global average daily consumption of 100 g of rice per person, this research demonstrates the feasibility of fortifying rice to address nutrient deficiencies effectively and contribute to improved dietary health worldwide. Further enhancement of vitamin B2 and B6 levels remains essential for optimal fortification, highlighting the potential of fortified rice as a sustainable solution for improving global nutrition.

Understanding natural genetic variation for nutritional quality in grain and identification of superior haplotypes in deepwater rice genotypes of Assam, India

Rice grown under deepwater ecosystem is considered to be natural farming and hence they are considered to be input efficient. Thus, to identify gene responsible for nutritional content under natural conditions, a genome-wide association study (GWAS)was performed. GWAS identified single nucleotide polymorphisms (SNPs) significantly associated with various nutritional quality traits such as Zn (mg/kg), Fe (mg/kg), Protein (%), Oil (%), Amylose (%), Starch (%), Phytic acid (%), Phenol (%) and TDF (%) in 184 deepwater rice accessions evaluated over 2 consecutive years. A total of 278 SNPs distributed across 12 chromosomes were found to be significantly associated with Zn, Oil and Phenol content. Among them, eight high confidence SNPs were significant and identified on chr1 (AX-95933712), chr7 (AX-95957036), and chr8 (AX-95965181) for Zn content. Similarly, on chr2 (AX-95945186), chr8 (AX-95964718), and chr11 (AX-95961099) have been found to be associated with Oil content and on chr3 (AX-95922121) and chr4 (AX-95963889) for Phenol content. Genomic regions of ± 220 kb flanking the three consistent lowest p value containing SNPs for each trait were considered for finding superior haplotypes. These SNPs showed significant phenotypic variations with different identified haplotype blocks. The allelic variations with phenotypes were considered to be superior haplotypes i.e., Block 1: Hap 1 (ACCC) for high Zn content, Block 2: Hap 1 (CT) for high Oil content, and Block 2: Hap 1(CGGG) for low Phenol content. The discovered superior haplotype with high nutritional content could be important for understanding the mechanisms involving nutrient use efficiency. Thus, the present study demonstrated that developing rice varieties with appropriate nutritional quality traits will be possible through the incorporation of such superior haplotypes in breeding programs.

Development of High Yielding Deep Water Rice Variety MTU 1184 Suitable for Semi-Deep Flooded Ecosystem of South Eastern Region of India

In recent years due to heavy and intense rainfall and cyclonic storms, paddy crop is experiencing damage due to flooding. If the flood water stagnation remains for more than a week the varieties are unable to sustain and there by the yield levels are drastically reduced. Hence, there is a need to develop submergence tolerant variety to minimize the yield losses. Acharya NG Ranga Agricultural University (ANGRAU), Regional Agricultural Research Station, Maruteru has developed flood tolerant variety MTU 1184 through conventional plant breeding using PLA 1100 and BM 71 as parents. The flood tolerant rice culture was extensively evaluated for yield in semi deep water ecosystem at RARS, Maruteru over the years of kharif, 2012 to kharif, 2016 in Station yield trials. The variety recorded superior grain yield (4370 kg/ha) against check PLA 1100 (3811 kg/ha) and yield advantage over check was 14.67%. The entry was tested in AICRIP trials from 2014 to 2017 at RARS, Maruteru and the results revealed that MTU 1184 registered 4650 kg/ha and found to be significantly superior over the national check, Sabitha (3703 kg/ha) and the per cent increase over check was 25.57. The variety recorded a mean grain yield of 4281 kg/ha and found to be significantly superior over the national check, Sabitha (3011 kg/ha) and yield advantage was 1270 kg/ha and per cent increase over national check was 42.17 and zonal check Poornendu in 8 locations of six states of south eastern region. Multi location testing of the variety from 2015 to 2017 revealed that the variety has out yielded (5370 kg/ha) and found superior over the best check PLA 1100 (4290 kg/ha) and the per cent increase over check was 25.18. Minikit testing in 890 locations for a period of three years from 2016 to 2018 revealed that the average mean yield of the variety over three years was 6039 kg/ha against local popular check PLA 1100 (5700 kg/ha) and per cent increase over check was 6.0 when tested in Andhra Pradesh.

Nature’s marvel, Deep water rice

Rice is the most important food crop of India. It is the staple food in most of the North Eastern parts as well as Southern part of India. Therefore, the people of North East India especially Assam is completely dependent on rice cultivation and its production. However, Assam is immensely affected by flood during the monsoon season. During that time of the year, most of the rice varieties are intolerant to water stress by submergence. Therefore, farmers are only able to cultivate deep water rice varieties during this season. Deep water rice shows an incredible tolerance to water-logged condition by escaping or managing to survive during submergence. Due to its fascinating water stress tolerance properties, it has been a major topic of concern. This review aims at encompassing the major studies done to investigate the factors responsible for making the plant tolerant to submergence and to evaluate its phytochemicals and nutritional values. Studying deeper into the plant can help in its biofortification as well as improve its yield through different breeding programs using enhanced varieties and thereby develop its marketing status.

Identification and Regulation of Hypoxia-Tolerant and Germination-Related Genes in Rice.

In direct seeding, hypoxia is a major stress faced by rice plants. Therefore, dissecting the response mechanism of rice to hypoxia stress and the molecular regulatory network is critical to the development of hypoxia-tolerant rice varieties and direct seeding of rice. This review summarizes the morphological, physiological, and ecological changes in rice under hypoxia stress, the discovery of hypoxia-tolerant and germination-related genes/QTLs, and the latest research on candidate genes, and explores the linkage of hypoxia tolerance genes and their distribution in indica and japonica rice through population variance analysis and haplotype network analysis. Among the candidate genes, OsMAP1 is a typical gene located on the MAPK cascade reaction for indica-japonica divergence; MHZ6 is involved in both the MAPK signaling and phytohormone transduction pathway. MHZ6 has three major haplotypes and one rare haplotype, with Hap3 being dominated by indica rice varieties, and promotes internode elongation in deep-water rice by activating the SD1 gene. OsAmy3D and Adh1 have similar indica-japonica varietal differentiation, and are mainly present in indica varieties. There are three high-frequency haplotypes of OsTPP7, namely Hap1 (n = 1109), Hap2 (n = 1349), and Hap3 (n = 217); Hap2 is more frequent in japonica, and the genetic background of OsTPP7 was derived from the japonica rice subpopulation. Further artificial selection, natural domestication, and other means to identify more resistance mechanisms of this gene may facilitate future research to breed superior rice cultivars. Finally, this study discusses the application of rice hypoxia-tolerant germplasm in future breeding research.

Assessing Deepwater Rice Mutant Populations for Some Morpho-Physiological and Agronomic Traits

Unlike most current rice cultivars, rice produced in the deepwater habitat may live for at least a month in water depths exceeding 50 cm. In this experiment, 30 M6 populations developed by irradiation of Laksmidigha rice seeds utilizing 200 Gy dose of gamma rays were assessed based on morpho-physiological and agronomic traits. Six mutant populations exhibited noticeably longer leaves, with LD-200-1-1-2-6 being the only mutant population to have noticeably more grain weight/hill than the parent. But none of the mutant populations had significantly wider leaf breadth at any of the three points of the flag leaf and average as well. Six mutant populations LD-200-1-3-3-3, LD-200-1-3-3-4, LD-200-1-3-3-5, LD-200-1-3-2-1, LD-200-1-1-2-1 and LD-200-1-1-2-6 produced significantly higher grain yield/hill which also had significantly longer panicle lengths, internode lengths and heavier 1000-grain weight than the parent. It was discovered through a correlation analysis that grain weight/hill was positively and significantly connected with panicle length and 1000-grain weight, whereas its association with internode distance was positively but not significantly correlated. But the correlation of internode distance with 1000-grain weight was significantly positive. The six mutant populations that significantly increased grain yield/hill compared to the parent also had higher levels of total chlorophyll and chlorophyll "a" in their flag leaves. In anatomical studies of roots, it was found that all the 21 cross sections showed damaged cortex with different degrees except LD-200-1-3-3-7 and LD-200-1-1-2-5. Even the parent grown in Chamber-1 showed minimum cortex damage. Also, the grain yield of these two mutant populations did not differ significantly from the parent although chlorophyll “a” and total chlorophyll contents were much higher.

Importance of Red Rice (Deep Water Rice) Production and Its Potential of Export from Dhemaji District of Assam

Red kernelled rice is gaining importance in recent years due to its higher nutritive content as well as health advantages. It is rich in fibre, iron, Vitamin B1 & B2, zinc and calcium. Because of its importance and a good potential for export the present study was undertaken in Dhemaji district of Assam with the objective to find out the economics of production and scope of marketing of red kernelled rice. From the investigation it was found that red kernelled rice is cultivated in deep water areas of the district and 40% of the total rice area is under red kernelled rice. The production very low with an average production of 21q/ha. The benefit cost ratio was found to be 1.29 and only two marketing channels existed in the district. A company viz. Nature Bio Foods Ltd. (NBFL) was the main company which procured all the production of red kernelled rice from the producers in Dhemaji district which has its Office at Gogamukh. About 10000tons of red rice is being exported outside the district every year to other states and even other countries like USA, UK and European countries. The price spread was found to be high though there are few intermediaries in the marketing channel. From the investigation it can be concluded that there is much scope of increasing the area, production and productivity of red kernelled rice in the district provided processing centers are set up in the district so that the farmers can get a better price for their produce.

Climate precarity in rural livelihoods: Agrarian transformations and smallholder vulnerability in Vietnam

AbstractIn recent decades, agrarian transformations in Southeast Asia have resulted in significant environmental and social change, yet insufficient attention has focused on the particular pathways by which these changes have increased vulnerability to climate change. In particular, climate precarity, a situation in which class, social, labour and/or gender inequities amplify negative impacts from climate change, has been on the rise for many smallholders. Using case studies in Vietnam of changes to swidden agriculture in upland areas and the loss of deepwater rice systems in the Mekong Delta lowlands, the paper examines social differentiation and ecological outcomes of these processes and how they have increased climate precarity, particularly for poor households and women. Based on longitudinal fieldwork in affected regions, we identify key changes contributing to climate precarity as farming systems intensify. In particular, loss of flexibility in farmer decision‐making, loss of voluntary engagement with markets, and declining access to social capital and entitlements have increased risks for households and reduced adaptation options. Suggestions are made to more directly address these elements in future agricultural and climate policies, rather than current approaches to climate adaptation that often promote even more intensification of agriculture, which runs the risk of exacerbating precarity.

Issue Information

New PhytologistVolume 238, Issue 4 p. 1333-1336 Cover and Issue InformationFree Access Issue Information First published: 12 April 2023 https://doi.org/10.1111/nph.18238AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Graphical Abstract Cover Legend Scanning electron micrograph of emerging aquatic adventitious root from the stem of deepwater rice (false-coloured image). Image courtesy of Chen Lin (Lin et al., pp. 1403–1419). Volume238, Issue4May 2023Pages 1333-1336 RelatedInformation

Characterization of Rice Genotypes for SNORKEL1 (SK1) and SNORKEL2 (SK2) Gene

The present study was performed in kharif (June-December) 2019 at Bihar Agricultural College, Sabour, Bhagalpur, Bihar, India to screen gene specific markers developed from SNORKEL1 (SK1) and SNORKEL2 (SK2) gene and identify the rice genotypes for the presence of SNORKEL genes. A total of 13 rice genotypes were used out of which 8 genotypes Vaidehi, RYC743, FR13A, Desaria, Dudhi, Birar, Kalaladora and Kajargod indicated the presence of both SNORKEL1 (SK1) and SNORKEL2 (SK2) gene using SK1-1, SK1-2, SK2-1 and SK2-2 markers. Therefore, these genotypes have tolerance ability of deep water flooding due to higher rates of elongation where water stagnates for longer than two weeks. However, results from the present study also revealed that the genotype Desaria and RYC743 had higher rates of elongation and Satyam, Sudha, Purnendu, FR13A, Pansoradhan and Swarna Sub1 had lower shoot elongation rate compared to other genotypes. This study provides gene specific markers for the identification of varieties/donors tolerant to deep water flooding as well as donors to be used in deep water rice breeding programs. Thus, the marker developed and validated in this study will aid rice breeders in quickly and efficiently identifying and introgressing the SNORKEL genes. The results would be a helpful in the development of rice varieties with both submergence tolerance and elongation ability in order to improve the yield stability in flood-prone areas.

The leaf sheath promotes prolonged flooding protection by giving rise to specialized adventitious roots.

This article is a Commentary on Lin et al. (2023), 238: 1403–1419.

Performance of Six Generations on Two Rice Crosses under Submergence Stress and Non-stress Conditions

Submergence tolerance has long been regarded as an important breeding objective for rain-fed lowland and deep water rice area. Despite this recognition, there has been limited success in developing rice with improved submergence tolerance in Africa. The present research was aimed at assessing performance of crosses under submergence stressed and non-stressed conditions in Nigeria. Six generations of the crosses were evaluated under optimum and submerged conditions in a complete randomized block design with three replications. Submergence screening was performed in controlled conditions that allowed flooding at a water depth of 1.0 meter for a period of 14 days. The results revealed that significant difference among the generations of the two crosses evaluated. The observed survival rate (%) in Cross I of the generations ranged between 0.00% - 100% while in Cross II, it ranged between 0.00% and 95.24%. The Phenotypic Coefficients of Variation (PCV) and the Genotypic Coefficient of Variation (GCV) for 100 grain weight were moderate to high under the two conditions. Low to moderate PCV and GCV coefficients of variation were observed for the grain width and grain length under both conditions in the two crosses. High heritability (0.96% respectively) and high genetic advance as percentage of mean were recorded for the grain yield and grain weight in the two crosses. The variability observed among the generations was optimum however, advancement of the segregating generations coupled with adequate selection criteria could lead to identification of superior and stable genotypes for farmers’ use.

Exploration of eQTLs regulating transcript for internode elongation under deep water treatment employing haplotype network in diverse deep water rice landraces of Assam, India

Exploration of eQTLs regulating transcript for internode elongation under deep water treatment employing haplotype network in diverse deep water rice landraces of Assam, India

A quantitative trait locus conferring flood tolerance to deepwater rice regulates the formation of two distinct types of aquatic adventitious roots.

A key trait conferring flood tolerance is the ability to grow adventitious roots as a response to submergence. The genetic traits of deepwater rice determining the development and characteristics of aquatic adventitious roots (AAR) had not been evaluated. We used near-isogenic lines introgressed to test the hypothesis that the impressive shoot elongation ability of deepwater rice linked to quantitative trait loci 1 and 12 also promote the development of AAR. The deepwater rice genotype NIL-12 possessed expanded regions at the stem nodes where numerous AAR developed as a response to submergence. Two types (AR1 and AR2) of roots with distinct timing of emergence and large differences in morphological and anatomical traits formed within 3 (AR1) to 7 (AR2) d of submergence. The mechanical impedance provided by the leaf sheath caused AR2 to emerge later promoting thicker roots, higher elongation capacity and higher desiccation tolerance. Upregulation of key genes suggests a joint contribution in activating the meristem in AAR enhancing the development of these in response to submergence. The morphological and anatomical traits suggested that AR2 is better adapted to long-term flooding than AR1. We therefore propose that AR2 in deepwater rice functions as an evolutionary defence strategy to tackle periodic submergence.

Molecular mechanism of internode elongation in rice.

Rice plants that form ventilated tissues, such as aerenchyma in the leaves, stems, and roots, allow for growth in waterlogged conditions (paddy fields), but they cannot breathe and drown in flooded environments where the whole plant body is submerged. However, deepwater rice plants grown in flood-prone areas of Southeast Asia survive in prolonged flooded environments by taking in air through an elongated stem (internode) and leaves that emerge above the water surface, even if the water level is several meters high and flooding continues for several months. Although it has been known that plant hormones, such as ethylene and gibberellins, promote internode elongation in deepwater rice plants, the genes that control rapid internode elongation during submergence have not been identified. We recently identified several genes responsible for the quantitative trait loci involved in internode elongation in deepwater rice. Identification of the the genes revealed a molecular gene network from ethylene to gibberellins in which internode elongation is promoted by novel ethylene-responsive factors and enhances gibberellin responsiveness at the internode. In addition, elucidation of the molecular mechanism of internode elongation in deepwater rice will help our understanding of the internode elongation mechanism in normal paddy rice and contribute to improving crops through the regulation of internode elongation.

Evaluation of morphologically important traits of deep water rice from advanced backcross families

Local germplasm of deep water rice possesses low yield productivity. Our studies showed that grain yield in Laxmi Digha can be increased significantly through backcross program with the high yielding rice variety Binadhan-18. Advanced backcross progenies (Laxmi Digha x Binadhan-18) exhibited higher values for most of the yield and yield-related traits analyzed in comparison with the parent. Number of tillers plant-1 and filled grains panicles-1 are positively correlated to yield and those resulted in higher grain yield in backcross families. In S103, S104, S105, S106 and S111 families, yield increase ranges from 52.97 to 84.1% when compared to Laxmi Digha parent. Five families, viz., S103, S104, S105, S106 and S111, were identified through yield increase analysis as most promising genotypes for cultivar development and processes variation in special characteristics viz. aerial root number and Knee capacity. The backcross families will be used to develop a deep water rice variety and efficient source of genetic diversity for future breeding programs.

Deepwater response in the African cultivated rice Oryza glaberrima

ABSTRACT Partial submergence of Oryza sativa deepwater rice elicits enhancement of internodal elongation, referred to as deepwater response, conferred by three types of genes, SNORKEL1/2 (SK1/2), SEMIDWARF1 (SD1), and ACCELERATOR OF INTERNODE ELONGATION 1 (ACE1). We investigated the presence and expression of these genes in the African cultivated rice Oryza glaberrima and the relationship between these genes and the deepwater response of O. glaberrima. In 49 of the 50 accessions tested, one or two SK genes were identified, which could be divided into three types of SK1 and four types of SK2. The accessions with the SK2 type whose expression was induced by submergence demonstrated rapid internodal elongation under submergence. In most of these accessions, submergence also increased the expression of SD1 and ACE1 genes. However, the accessions did not possess the haplotype of SD1 that is associated with high deepwater response in O. sativa. In contrast, they possessed the type of ACE1 gene similar to that in O. sativa deepwater rice. These results indicate that the molecular mechanisms underlying induction of deepwater response in O. glaberrima are similar to that found in deepwater rice of O. sativa and suggest that most O. glaberrima cultivars, including upland cultivars, can exhibit rapid internodal elongation under submergence.

Opportunities beyond CO2 for climate mitigation

Opportunities beyond CO2 for climate mitigation

Evolution of different rice ecotypes and genetic basis of flooding adaptability in Deepwater rice by GWAS

BackgroundRice is the world’s second largest food crop and accelerated global climate change due to the intensification of human activities has a huge impact on rice. Research on the evolution of different rice ecotypes is essential for enhancing the adaptation of rice to the unpredictable environments.ResultsThe sequencing data of 868 cultivated and 140 wild rice accessions were used to study the domestication history and signatures of adaptation in the distinct rice ecotypes genome. The different populations had formed distinct rice ecotypes by phylogenetic analyses and were domesticated independently in the two subspecies of rice, especially deepwater and upland rice. The domestication history of distinct rice ecotypes was confirmed and the four predicted admixture events mainly involved gene flow between wild rice and cultivated rice. Importantly, we identified numerous selective sweeps that have occurred during the domestication of different rice ecotypes and one candidate gene (LOC_Os11g21804) for deepwater based on transcriptomic evidence. In addition, many regions of genomic differentiation between the different rice ecotypes were identified. Furthermore, the main reason for the increase in genetic diversity in the ecotypes of xian (indica) rice was the high proportion of alternative allele frequency in new mutations. Genome-wide association analysis revealed 28 QTLs associated with flood tolerance which contained 12 related cloned genes, and 20 candidate genes within 13 deepwater QTLs were identified by transcriptomic and haplotype analyses.ConclusionsThese results enhanced our understanding of domestication history in different rice ecotypes and provided valuable insights for genetic improvement and breeding of rice in the current changing environments.

Life cycle greenhouse gas emissions from five contrasting rice production systems in the tropics

Carbon Footprints (CFs) quantification of major rice production systems (RPSs) is a prerequisite for chalking out strategies for climate change mitigation in agriculture. Total life cycle greenhouse gas emissions (LC-GHGs) from production to consumption could provide precise CFs for RPSs. Therefore, to address this issue, we assessed all the three segments of LC-GHGs for five major contrasting RPSs in India, such as, aerobic rice (AR), shallow lowland rice (SLR), system of rice intensification (SRI), deep water rice (DWR), and zero-tilled direct-seeded rice (ZTR)) to determine the CFs. The CF was found to be lowest in ZTR but the LC-GHGs were found to be lowest in case of AR, which recorded higher CF than that of ZTR. So, for short-term reduction of greenhouse gas (GHG) emission, aerobic rice (AR) is a good option. However, ZTR with lowest CF among all, could be prompted with incentives for long-term strategy. Among the segmental LC-GHGs, the ‘on-farm’ emission contributed less compared to the other two segments. The post-harvest to consumption segment contributed the maximum (54%–69%) of total LC-GHGs, followed by ‘cradle-to-farm’ (21%–27%), and on-farm operations (11%–23%). These findings suggest that post-harvest components that contribute maximum GHG emissions must be tackled scientifically with proactive policy initiatives. However, the data on this segment is limited and scattered. Therefore, real-time assessment of GHG emissions during post-harvest activities and transportation of inputs from cradle to farm require more precise quantification. Although the CF in SRI was found to be more, yet this system has the potential to fetch higher yields and better soil carbon storage. So, SRI could be encouraged for food security and long-term sustainability perspectives by reducing greenhouse gas emissions by 3-to-4 times.