International Rice Research Institute Research Articles

Rice breeding for higher crop productivity (a review)

The main global trends in the breeding of rice cultivars and hybrids are higher plant productivity, adaptability to cultivation conditions, quality of products, and resistance to environmental stressors, including diseases.Efforts of leading breeding centers in the Philippines and China to further increase the rice yield are associated with a change in the plant morphotype: shorter plants with erectoid leaves and large panicles with a high number of grains.The International Rice Research Institute (IRRI) has developed rice cultivars that under favorable conditions in the tropical zone produce a grain yield of up to 10–11 t/ha, with Kecon = 0.5. A heterotic hybrid of rice was obtained in China with a yield of 13.9 t/ha; it has a new plant morphotype (New Plant Type) and a growing season of 163 days. The hybrid is classified as “super rice”.Modern breeding programs are aimed at producing cultivars of “Green Super Rice” using pedigree methods and backcrossing for introgression of target genes through DNA markers, QTL mapping, pyramiding, and recurrent selection.Russian breeders have traditionally produced rice cultivars adapted to local conditions, with a growing season of no more than 125 days. In the 1980s, a program was launched to develop a high-yielding rice cultivar with erectoid leaves for condensed planting. As a result of multiple stepwise hybridization and targeted selection, new source material with target traits of “super rice” was released. Cv. ‘Polyus-5’ with a new plant morphotype was obtained on its basis. This cultivar was included in the State Register and from 2023 approved for commercial production. During the field trials, ‘Polyus-5’ yielded a maximum of 1380 g/m2 over 120 days of the growing season, under the conditions of condensed sowing and increased mineral nutrition.

Association Analysis in Rice Germplasm Lines for High Temperature Tolerance

Background: Relative to other abiotic factors like salinity and drought, breeding rice cultivars that are resistant of high temperatures has received a little attention. The purpose of this study is to find parents and genotypes that are suitable for utilizing in high temperature stress breeding program. Methods: The genetic material for this study comprised of a set of germplasm collections (293 accessions) from different sources such as International Rice Research Institute germplasm. These populations were raised at the Department of Rice, Centre for Plant Breeding and Genetics, Tamil Nadu Agricultural University, Coimbatore. The Heat tolarance Indices (TOL) viz., Heat tolerance index (HTI) and Heat susceptibility index (HSI) and association analysis were estimated among germplasm lines for yield attributes under normal and high temperature stress condition. Result: Out of 293 genotypes, sixty nine genotypes significantly exceeded for both HTI and HSI. Association studies revealed that, single plant yield had highly significant and positive association with panicle exertion, number of total tillers per plant, number of productive tillers per plant, panicle length, number of filled grains per panicle and total dry matter production. Spikelet sterility and high temperature susceptibility index had highly significant and negative association with single plant yield. Number of productive tillers had significant and positive correlation with total dry matter production, panicle length, number of filled grains per panicle, days to maturity, hundred grain weight, grain breadth and high temperature susceptible index. Hence these traits may be considered as selection indices for yield and high temperature tolerance improvement programme. Hence it may be possible to combine single plant yield and heat susceptibility index by specific breeding programme for high temperature tolerance in rice.

Effect of Phosphorus Levels on Early Seedlings of Rice (Oryza sativa) under Varying Moisture Stress Conditions

This study investigated the impact of moisture levels and phosphorus applications on different rice varieties. It aimed to: 1. Identify optimal rice varieties for specific moisture and phosphorus combinations. 2. Understand how moisture stress affects seed germination speed and root and shoot development. 3. Analyze the influence of increased phosphorus on root growth, especially under moisture stress. 4. Evaluate if additional NPK application enhances the positive effects of phosphorus. The meticulously controlled experiment, conducted within the International Rice Research Institute (IRRI)'s RGA facility from October to November 2023, utilized five rice varieties, three moisture levels (flooded, ideal, and Drought-like), and varying phosphorus levels. The findings revealed a positive correlation between phosphorus levels and root length across all rice varieties. This emphasizes the crucial role of phosphorus in promoting root development under challenging conditions. Notably, while increased phosphorus significantly enhanced root adhesion under flooding and aided seedling recovery, drought remained a significant barrier to root growth, regardless of phosphorus application. Interestingly, despite general genetic uniformity in germination and root-shoot parameters among the varieties, a clear positive correlation between phosphorus levels and root length was still observed. In conclusion, this study highlights the importance of phosphorus in strengthening root grip during floods, thereby aiding seedling recovery. However, it also emphasizes that drought remains a dominant factor hindering plant growth. The consistency observed across different rice varieties strengthens the findings, and the significant increase in root length with increased phosphorus application underscores its vital role in root development under challenging conditions. This study provides valuable insights for optimizing rice growth strategies by considering specific rice varieties, moisture levels, and phosphorus applications.

“A bloodless social revolution”: Land reform and multiple cropping in Cold War Taiwan, 1950–1979

Societal Impact StatementMultiple cropping, the cultivation of several crops on the same land in a year, occupied an important part of Taiwan's agricultural research from 1950 to 1970. This research originated in the context of Taiwan's land reform and diversification programs and their connections to the government's political ambition to maximize food production. The study of how multiple cropping was politicized and depoliticized by different actors helps to expand the narratives of the Green Revolution in Asia, analyze their legacies, and highlight Taiwan's role in the international exchange of visions of agricultural development during the Cold War.Summary Scholars have recently expanded the history of the Green Revolution to move beyond the narrative of North–South technological diffusion. This article enriches the scholarship with the case of multiple cropping in Taiwan and its connection to Cold War geopolitics. Rice productivity in postwar Taiwan was boosted through a land reform launched by the Sino‐American Joint Commission on Rural Reconstruction (JCRR) in the 1950s. Backed by American aid and staffed by scientists from the Republic of China (ROC) government, the JCRR envisioned to turn tenant farmers into landowners so as to encourage labor input and adoption of seeds and fertilizers. By 1960, the JCRR presented its reform as a “bloodless social revolution” and extended its focus to multiple cropping through a diversification program. The JCRR further created the Asian Vegetable Research and Development Center (AVRDC) in 1971 to spread Taiwan's breeding and cropping techniques. The ROC's diplomatic isolation in the 1970s, however, prompted the center to reinterpret Taiwan's success in multiple cropping from a political achievement to a technological triumph, thus reinforcing the technology‐driven narrative used by the International Rice Research Institute (IRRI). Through Taiwan's influences on IRRI's rice breeding and multiple cropping research, this paper illustrates that the history of the Green Revolution requires more complex narratives. In addition, with Taiwan's political and economic transition since the 1980s, farmers began to reclaim their voice and influence agricultural policies. The case thus highlights the need of democratic participation in agricultural research, a concern that remains relevant today.

Fractionation of stable carbon isotopes during formate consumption in anoxic rice paddy soils and lake sediments

Abstract. Formate is energetically equivalent to hydrogen and thus is an important intermediate during the breakdown of organic matter in anoxic rice paddy soils and lake sediments. Formate is a common substrate for methanogenesis, homoacetogenesis and sulfate reduction. However, how much these processes contribute to formate degradation and fractionate carbon stable isotopes is largely unknown. Therefore, we measured the conversion of formate to acetate, CH4 and CO2 and the δ13C of these compounds in samples of paddy soils from Vercelli, Italy, and the International Rice Research Institute (IRRI) in the Philippines and of sediments from the NE and SW basins of Lake Fuchskuhle, Germany. The samples were suspended in a phosphate buffer (pH 7.0) in both the absence and presence of sulfate (gypsum) and of methyl fluoride (CH3F), an inhibitor of aceticlastic methanogenesis. In the paddy soils, formate was mainly converted to acetate under both methanogenic and sulfidogenic conditions. Methane was only a minor product and was mainly formed from the acetate. In the lake sediments, the product spectrum was similar but only under methanogenic conditions. In the presence of sulfate, however, acetate and CH4 were only minor products. The isotopic enrichment factors (εform) of formate consumption, determined by Mariotti plots, were in the low range of −8 ‰ to −2.5 ‰ when sulfate was absent, and formate was mainly converted to acetate and CH4. However, no enrichment factor was detectable when formate was degraded with sulfate to mainly CO2. The δ13C of acetate was by about 25 ‰–50 ‰ more negative than that of formate, indicating acetate production by chemolithotrophic homoacetogenesis. Hence, formate seems to be an excellent substrate for homoacetogenesis in anoxic soils and sediments, so that this process is competing well with methanogenesis and sulfate reduction.

Geographic differences and variation of functional components of brown rice in 690 mini-core collections from global germplasms

ObjectiveTo understand the geographic differences and variations in the functional components of brown rice cores collected from global rice germplasms. MethodsFour functional components, γ-aminobutyric acid (GABA), resistant starch (RS), total flavonoids, and alkaloids, in brown rice from 690 mini-core collections from 31 countries from five continents and the International Rice Research Institute, were analyzed using a spectrophotometry colorimetric method, and the results were statistically validated. ConclusionThe highest average amounts of functional components were obtained in Asian germplasms, except for GABA, and total flavonoids were highest in brown rice from Europe and Oceania, followed by Asia. The highest coefficient of variation for GABA was observed in Asia; that for RS and total flavonoids was observed in Africa, followed by Asia; and that for alkaloids was observed in America, followed by Asia. Overall, Asian countries were the most prominent and representative zones with the highest genotypic potential for functional components of brown rice. Forty-one rice accessions with enriched functional components originated mostly from biodiversity-rich areas in China, followed by those in the Philippines. Late sowing favored the enrichment of these components in brown rice. The current study provides a reference for rice breeding with enriched functional constituents, and guidelines for screening functional rice that could be used for human chronic disease research.

Solving the mystery of Obake rice in Africa: population structure analyses of Oryza longistaminata reveal three genetic groups and evidence of both recent and ancient introgression with O. sativa.

The undomesticated rice relative Oryza longistaminata is a valuable genetic resource for the improvement of the domesticated Asian rice, Oryza sativa. To facilitate the conservation, management, and use of O. longistaminata germplasm, we sought to quantify the population structure and diversity of this species across its geographic range, which includes most of sub-Saharan Africa, and to determine phylogenetic relationships to other AA-genome species of rice present in Africa, including the prevalence of interspecific hybridization between O. longistaminata and O. sativa. Though past plant breeding efforts to introgress genes from O. longistaminata have improved biotic stress resistance, ratooning ability, and yield in O. sativa, progress has been limited by substantial breeding barriers. Nevertheless, despite the strong breeding barriers observed by plant breeders who have attempted this interspecific cross, there have been multiple reports of spontaneous hybrids of O. sativa and O. longistaminata (aka "Obake") obtained from natural populations in Africa. However, the frequency and extent of such natural introgressions and their effect on the evolution of O. longistaminata had not been previously investigated. We studied 190 O. longistaminata accessions, primarily from the International Rice Research Institute genebank collection, along with 309 O. sativa, 25 Oryza barthii, and 83 Oryza glaberrima control outgroups, and 17 control interspecific O. sativa/O. longistaminata hybrids. We analyzed the materials using 178,651 single-nucleotide polymorphisms (SNPs) and seven plastid microsatellite markers. This study identified three genetic subpopulations of O. longistaminata, which correspond geographically to Northwestern Africa, Pan-Africa, and Southern Africa. We confirmed that O. longistaminata is, perhaps counterintuitively, more closely related to the Asian species, O. sativa, than the African species O. barthii and O. glaberrima. We identified 19 recent spontaneous interspecific hybrid individuals between O. sativa and O. longistaminata in the germplasm sampled. Notably, the recent introgression between O. sativa and O. longistaminata has been bidirectional. Moreover, low levels of O. sativa alleles admixed in many predominantly O. longistaminata accessions suggest that introgression also occurred in the distant past, but only in Southern Africa.

Development and evaluation of the first automated irrigation system for alternate wetting and drying technique in rice cultivation in Bangladesh

Rice stands as one of the most water-intensive crops in agriculture, demanding a substantial volume of water annually for cultivation in Bangladesh. To address this considerable water requirement, the International Rice Research Institute (IRRI) introduced the alternate wetting and drying (AWD) irrigation method. This approach necessitates consistent manual oversight to maintain the desired water levels in the field. In pursuit of reducing this manual effort, a study was conducted at Bangabandhu Sheikh Mujibur Rahman Agricultural University. The study aimed to develop an automated version of the AWD irrigation system, assess its impact on plant growth and yield-contributing factors, and investigate water use efficiency through using that automated system. The automated AWD system incorporated water level controllers, solenoid valves, and water level detection probes to regulate water levels in the paddy field. The experiment followed a Randomized Complete Block Design (RCBD) with three treatments: T1 (Conventional Irrigation - CI), T2 (AWD), and T3 (Automated Alternate Wetting and Drying - AAWD), each replicated four times. The findings indicated minimal variation in growth and development parameters of the rice plants between the CI and AWD treatments. Likewise, yield components demonstrated no significant differences among the various treatments. Notably, the treatment with automated alternate wetting and drying (AAWD), namely T3, displayed the highest water use efficiency (WUE) at 65.20 kg/ha/cm, while the lowest WUE of 52.56 kg/ha/cm was observed in the conventional irrigation (CI) treatment T1. The results underscore the clear advantage of adopting an automated AWD system, yielding a 20% reduction in irrigation water usage compared to the conventional approach. This transition also minimizes the need for labor-intensive interventions in the paddy fields of Bangladesh, illustrating the potential for more efficient and sustainable rice cultivation practices.

Physical Screening of Resistance on Selected Rice Accessions against Rice Leaf Folder – Cnaphalocrocis medinalis Guenee (Pyralidae: Lepidoptera) under Screen House Condition

The experiment was carried out at screen house III, Department of Entomology, Faculty of Agriculture, Annamalai University, Chidambaram. India. Total 13 numbers of rice accessions were concerned along with one susceptible check (TN-1) to picked up to quantify the most prominent resistant accessions on different selected rice genotypes by showing their resistance characters against the rice leaf folder, Cnaphalocrocis medinalis during Kharif 2022. Among which, based on the morphological traits viz., plant height, length and width of flag leaves, productive tiller numbers, peduncle length, panicle length and trichome density, only one accession (BA-207) was recorded as highly resistant and five (BA-18, BA-31, BA-187, BA-193 and BA-266) of them were reported as resistant accessions. The observations were made at 60 days after transplanting. All the results are given based on the standard evaluation system (SES) build up by International Rice Research Institute. Three of accessions exhibit moderate resistance viz., BA-30, BA-116 and BA-243. Three numbers of accessions were noted as moderately susceptible, which are BA-5, BA-80 and BA-91. At the same time, TN-1 was noticed as highly susceptible. A detailed report given in this research article is based on 13 rice accessions that were tested under screen house conditions. In the farmers point of view, susceptible varieties should replaced with resistant accessions to decrease the pest incidence and enhance the grain productions.

Genetic diversity of INGER rice genotypes based on morphological charac-ters and bacterial blight resistance

Bacterial blight disease (causal organism: Xanthomonas oryzae pv. oryzae) is an economically significant menace to rice cultivation in Bangladesh as well as in the world, which reduces significant yield loss in rice and hampers food security. The most sustainable strategy to fight this disease is the adoption of disease-resistant cultivars. The morphological trait and nature of diversity of 92 bacterial blight-resistant INGER (International Network for Genetic Evaluation of Rice) genotypes collected from the International Rice Research Institute (IRRI, Philippines) were analyzed to explore for sources of resistance. Artificial inoculation by BXO9, a virulent race of Xoo was used to evaluate and screen those genotypes in the field. Twelve genotypes, out of 92 had resistance, and another twelve had moderately resistance. Eleven morphological traits including disease data of each genotype were recorded and found noticeable diversity among the genotypes. Pearson’s correlation analysis among genotypes revealed that yield per hill is positively correlated with number of tiller per hill, number of effective tiller per hill, number of spikelets per panicle, number of filled spikelets per panicle and thousand grain weight. In cluster analysis, 15 major groups were obtained in ninety-two rice genotypes by using Euclidean distance and the UPGMA method. Cluster-1 comprises single genotypes SVIN310 which showed resistant reaction to bacterial blight disease had the highest tiller number, effective tiller number, number of spikelets per panicle, filled spikelets per panicle and thousand-grain weight. In PCA analysis, the first four principal components narrated around 77.32% variation. Among ninety-two genotypes, G1 (SVIN310), G23 (SVIN018), G70 (SVIN012), G75 (SVIN054), G33 (SVIN007), G48 (SVIN006), G80 (SVIN049), G90 (BRRI dhan84), G30 (SVIN290) near to the vector line of yield per hill are highly and positively responsive to the yield per hill. Considering all of these, cluster-1 having genotype SVIN310 with resistant phenomena would be the potential genotype for further use in a breeding program. Bangladesh Rice J. 26 (1): 17-31, 2022

Impact of Rice Seed Production, Processing, and Distribution Training on the Stakeholders in Bangladesh

The study examined the impact of rice seed production, processing, and distribution training on the rice seed stakeholders. Ten one-day training events were conducted by Bangladesh Agricultural Development Corporation (BADC) and funded by the International Rice Research Institute (IRRI). Sample size of trainees included 199 rice seed dealers, 62 rice growers, and 29 dealers cum growers across four divisions of Bangladesh. The perceived impact of training was determined by employing a t-test. Almost all of the stakeholders showed improvement in their learning of the subjects designed and the correlation between their knowledge before and after training sessions were highly correlated.. Dealers expressed their views of moderate use of the training outcomes in determining seed demand, storage, and sale, whereas growers and dealer cum growers were highly optimistic about using their knowledge and skills obtained in seed production, processing, storing, and marketing in a better way. Significant changes in knowledge and skills and favorable perceptions were observed among all the stakeholders for better production, processing, and utilization of rice seed.

Evaluation of Methane Emission Reduction Potential of Water Management and Chinese Milk Vetch Planting in Hunan Paddy Rice Fields

In order to explore the methane reduction potential with two scenarios of water management and Chinese Milk Vetch return, we calculated the methane emissions of Hunan Province rice fields in 2019 using the SECTOR tool based on Excel and released by the International Rice Research Institute. Thus, we preliminarily established an agricultural carbon emissions monitoring, reporting, and verification (MRV) system. The results showed that: (1) There was significant spatial variation in methane emissions in Hunan rice fields, with higher emissions in both the south and north and lower emissions in the east and west. Late rice was the main contributor to methane emissions, and the cities of Changde, Hengyang, Yueyang, and Shaoyang were high-emission areas due to differences in rice planting types and areas. Compared with flooding (1275.75 Gg), optimized water management measures (mid-drainage and AWD irrigation) reduced methane emissions by 29~45% (905.79 and 701.66 Gg, respectively). (2) Under the same nitrogen input conditions, compared with a solely straw return (375.24 Gg), combining green manure with straw return could partially reduce methane emissions from Hunan super hybrid rice (327.63 Gg). Compared with the control fertilizers (404.28 Gg), the reduction rates of winter-planted Chinese Milk Vetch, the return of rice straw, and the incorporation of both Chinese Milk Vetch and straw were 7.19%, 13.01%, and 18.96%, respectively. Based on scientific accounting tools, a preliminary MRV system for rice field carbon emissions was established. Under the national demand for reducing fertilizer use and increasing efficiency, equal nitrogen organic amendments could effectively contribute to the development of green, low-carbon, and high-quality agriculture.

Epidemiology of Rice Blast (Pyricularia oryzae) Disease in Central Punjab, Pakistan

Rice blast disease (RBD) is mostly controlled by fungicides by the farmers of central Punjab, Pakistan. However, the use of fungicides by the farmers is excessive and ill-advised, resulting in the emergence of new resistant strains of Pyricularia oryzae. The ill-advised employment of fungicides can be timed exploring the role of environmental factors favourable for this disease. The objective of current study was to determine the most favourable weather conditions for RBD in central Punjab, Pakistan, where this crop is mostly cultivated. Environmental factors including maximum and minimum temperatures (max and min temp), rainfall (Rf), relative humidity (Rh) and wind speed (Ws) conducive for RBD were characterized during this study. For this purpose, eight years (2009-2016) RBD severity data of susceptible to highly susceptible genotypes together with environmental data (max and min temp, Rf, Rh and Ws) was collected from Kala Shah Kako (KSK), Rice Research Institute (RRI), Punjab, Pakistan. The genotypes were being cultivated for eight years in randomized complete block design (RCBD), and data was kept on recording during the months of high disease pressure. Data was collected after ten days interval using disease scoring scale developed by International Rice Research Institute (IRRI) during 1996. Simple linear regression models were used to determine the relationship of environmental factors with RBD severity. The variation in RBD severity due to environmental factors was determined using coefficient of determination (R2). In present study, the relationship of max temp, Rf, Rh and Ws with RBD severity was positive, significant and linear, however, the relationship of min temp with RBD severity was negative. Max temp 40-42°C, min temp 21-23°C, Rf 2-3mm, Rh 50-70% and Ws 9-11 Km/h were found to be most favourable environmental conditions for RBD severity. The current research disclosed the significant role of all five environmental factors in the spread of RBD. Thus, future predictive models could be established using these five environmental factors for more accurate prediction of this disease in rice belt of Punjab, Pakistan, to time the application of fungicides.

Screening of recombinant inbred lines for resistance to bacterial leaf blight pathotypes in rice (Oryza sativa L.)

In the present investigation 16 recombinant inbred lines (RIL’s) developed from the intra-specific cross between YH3 and AKDRMS 21-54 through Marker Assisted Pedigree Breeding Method were screened along with their parents and the checks, namely, BPT 5204, TN1 and Improved Samba Mahsuri (ISM) against IxoPt-20 pathotype at the ICAR-Indian Institute of Rice Research, Hyderabad during Rabi 2021-22 and a new pathotype of Xanthomonas oryzae pv. oryzae causing Bacterial Leaf Blight disease in rice at Regional Agricultural Research Station, Maruteru during Kharif 2022 to identify pathotype specific resistant sources. Morpho-Molecular screening was adopted to evaluate the recombinant inbred lines over two locations in the consecutive seasons of Rabi 2021-22 and Kharif 2022. Based on per cent diseased leaf area, the genotypes were scored and categorised as per the Standard Evaluation System (SES) scale provided by International Rice Research Institute (IRRI). The results revealed all 16 RIL’s to be either resistant (10) or moderately resistant (6) to IxoPt-20 pathotype. However, only five RIL’s were found to be resistant, while four RIL’s were moderately resistant for the new virulent pathotype. Seven RIL’s with resistant to moderately resistant reaction for IxoPt-20 pathotype, showed moderately susceptible reaction for the new virulent pathotype. Among the resistant RIL’s identified for each pathotype, BPT-1901-72-10-6, BPT-1901-108-4-1 and BPT-1901-111-3-2 were found to be uniformly resistant, while, BPT-1901-45-8-6 and BPT-1901-163-1-18 were uniformly moderately resistant to both IXoPt-20 and the new virulent pathotype at Hyderabad and Maruteru, respectively, indicating their potential as genetic stocks for development of new cultivars resistant to bacterial leaf blight disease.

Optimizing quantitative trait loci introgression in elite rice germplasms: Comparing methods and population sizes to develop new recipients via stochastic simulations

AbstractThis study compared three strategies to develop new recipients for quantitative trait loci (QTL) introgression (background recovery [BG], selective sweep [SS] and breeding value [BV]) in a short‐term rice breeding programme (over five breeding cycles). Furthermore, we evaluated two different numbers of recipients (10 and 20) in the introgression process and how they influence the population performance and the QTL fixation over cycles. Finally, we used the International Rice Research Institute (IRRI) rice breeding framework as the model to perform the stochastic simulations. Each strategy was simulated and replicated 100 times. Regardless of the selection strategy used, the QTL introgression resulted in substantial penalties in yield performance. However, introducing fewer new parents to the augmentation process minimized this effect. Conversely, the time required to achieve fixation of target QTLs showed substantial differences, with selection for BV during augmentation outperforming other methods. Overall, the BV_10 strategy (10 parents selected based on genomic estimated BV) displayed the best trade‐off between reduced penalty from introducing new QTLs with a reasonable speed at which those QTLs can achieve fixation over subsequent breeding cycles.

Alleviating drought stress in rice plant through intervention of Trichoderma spp.

Aim: Trichoderma provides resistance to abiotic stress by generating a variety of secondary metabolites, phytohormones, through nutrient solubilization. The current study was conducted to determine whether Trichoderma could be used to alleviate drought stress in rice. Methodology: Three distinct isolates of Trichoderma harzianum [94 (A),T-14, IRRI-2] obtained from the International Rice Research Institute India, as well as two native isolates of Trichoderma asperellum (OT-3) and Trichoderma harzianum (0T-8) obtained from the farmlands of OUAT through serial dilution, were inoculated through seedling root dip treatment. Different morphological (days to active tillering, plant height, panicle initiation, root length, leaf rolling score, number of unfilled and filled grains per panicle) and biochemical data (Total phenolic content, malondialdehyde, proline, hydrogen peroxide, lignin and peroxidase) were estimated to determine the stress due to drought. Results: In-vivo studies on plant height, root length, number of filled grains, grains per panicle and leaf rolling that are positively associated with grain yield revealed that the application of Trichoderma had increased the grain yield. The effect of various biochemical characteristics, such as increase in phenol, peroxidase, lignin and cell membrane stability, which are known to alleviate drought stress through a variety of mechanisms were observed in this study. Inoculation of Trichoderma reduced the levels of oxidative chemicals such as proline, malondialdehyde, and hydrogen peroxide. Interpretation: The biochemical and morphological changes found in this study support the hypothesis that Trichoderma had a positive impact on yield and drought stress. Key words: Drought, Rice, Stress-related enzymes, Trichoderma spp

Don't panic any more: MORE PANICLES 3 increases rice yield at elevated CO2 levels.

Don't panic any more: MORE PANICLES 3 increases rice yield at elevated CO2 levels.

Candidate miRNAs from Oryza sativa for Silencing the Rice Tungro Viruses

Rice tungro disease (RTD), caused by Rice tungro bacilliform virus (RTBV) and Rice tungro spherical virus (RTSV) is one of the most prominent viral diseases in Asian countries. This virus disease problem seems to have been accentuated in those countries by causing a series of outbreaks over the years after being first reported in International Rice Research Institute (IRRI), Philippines, in 1963. One of the effective ways to combat viruses is through RNA silencing. microRNA is an important player in the RNA silencing mechanism. Genome sequences analysis shows RTBV-SP isolate (8 Kb) is composed of four open reading frames (ORF 1, ORF 2, ORF 3, and ORF 4), meanwhile, RTSV-SP (12 Kb) consists of one open reading frame encoded by seven different polyproteins (P1, CP1, CP2, CP3, NTP, Pro, and Rep). Therefore, this study investigated possible rice-encoded miRNAs targeted on RTBV and RTSV using in silico analysis. Five bioinformatics tools were employed using five different prediction algorithms: miRanda, RNA22, RNAhybrid, Tapirhybrid, and psRNATarget. The results revealed each RTBV and RTSV can be silenced by three potentially best candidate rice-encoded miRNA. For RTBV, osa-miR5510 (accession no. MIMAT0022143), osa-miR3980a-3p (accession no. MIMAT0019676), and osa-miR3980b-3p (accession no. MIMAT0019678) are being predicted by all five algorithms. Meanwhile, for RTSV, three miRNAs predicted are osa-miR414 (accession no. MIMAT0001330), osa-miR5505 (accession no. MIMAT00221138) and osa-miR167a-3p (accession no. MIMAT0006780). The predicted data provide useful material for developing RTBV and RTSV-resistant rice varieties.

Research on Salt Stress in Rice from 2000 to 2021: A Bibliometric Analysis

This study aimed to assess global trends in research on salt stress in rice and provide new directions for future studies. The subjects in this study are a plain text file with full records and cited references (Web of Science core collection as the database, “rice” and “salt” as the retrieved title with the date range from 1 January 2000 to 31 December 2021). The bibliometric method was used in this study, and the results were visualized using Scimago Graphica, VOSviewer, and CiteSpace. The results showed that China, India, and Japan contributed most of the literature in this field, and the institutes with the largest academic output were the Chinese Academy of Science, the International Rice Research Institute, and Nanjing Agriculture University. This study argues that research on salt stress in rice has been conducted in three main areas: phenotypes, response mechanisms, and remediation strategies. Inoculation of rhizosphere bacteria, ion homeostasis, soil remediation, and gene editing will be popular topics in rice salt stress research in the future. This study aimed to provide a potential theoretical direction for research on salt stress in rice as well as a reference for feasible studies on the exploitation of saline–alkali lands.

Spectral characterization and severity assessment of rice blast disease using univariate and multivariate models.

Rice is the staple food of more than half of the population of the world and India as well. One of the major constraints in rice production is frequent occurrence of pests and diseases and one of them is rice blast which often causes yield loss varying from 10 to 30%. Conventional approaches for disease assessment are time-consuming, expensive, and not real-time; alternately, sensor-based approach is rapid,non-invasive and can be scaled up in large areas with minimum time and effort. In the present study, hyperspectral remote sensing for the characterization and severity assessment of rice blast disease was exploited. Field experiments were conducted with 20 genotypes of rice having sensitive and resistant cultivars grown under upland and lowland conditions at Almora, Uttarakhand, India. The severity of the rice blast was graded from 0 to 9 in accordance to International Rice Research Institute (IRRI). Spectral observations in field were taken using a hand-held portable spectroradiometer in range of 350-2500 nm followed by spectral discrimination of different disease severity levels using Jeffires-Matusita (J-M) distance. Then, evaluation of 26 existing spectral indices (r≥0.8) was done corresponding to blast severity levels and linear regression prediction models were also developed. Further, the proposed ratio blast index (RBI) and normalized difference blast index (NDBI) were developed using all possible combinations of their correlations with severity level followed by their quantification to identify the best indices. Thereafter, multivariate models like support vector machine regression (SVM), partial least squares (PLS), random forest (RF), and multivariate adaptive regression spline (MARS) were also used to estimate blast severity. Jeffires-Matusita distance was separating almost all severity levels having values >1.92 except levels 4 and 5. The 26 prediction models were effective at predicting blast severity with R2 values from 0.48 to 0.85. The best developed spectral indices for rice blast were RBI (R1148, R1301) and NDBI (R1148, R1301) with R2 of 0.85 and 0.86, respectively. Among multivariate models, SVM was the best model with calibration R2=0.99; validation R2=0.94, RMSE=0.7, and RPD=4.10. The methodology developed paves way for early detection and large-scale monitoring and mapping using satellite remote sensors at farmers' fields for developing better disease management options.