Submergence Tolerant Rice Varieties Research Articles

Mechanistic Insights and Genetic Approaches for Enhancing Submergence Tolerance in Rice

Rice, a pivotal staple crop, serves as a dietary foundation for approximately half of the global population. Its cultivation, traditionally reliant on submerged conditions, faces significant challenges due to sudden flooding events. The majority of rice varieties are highly sensitive to prolonged submersion beyond a mere seven days, resulting in substantial yield losses. As global climate patterns shift, the occurrence and intensity of flooding are predictable to increase, exacerbating this issue. Therefore, development of rice varieties having enhanced submergence tolerance is critical to sustaining productivity and ensuring food security in flood-prone regions. Understanding the physiological and biochemical mechanisms underlying submergence tolerance is crucial in this context. Key physiological mechanisms include the regulation of carbohydrate reserves for energy during low oxygen availability, ethylene-responsive factors, especially the Sub1A gene to, regulate growth and stress responses, curbing excessive elongation to conserve energy and enhance survival. Additionally, specialized tissues such as aerenchyma and adventitious roots improve oxygen transport and nutrient uptake under flooded conditions. Genetic approaches, including Marker-Assisted Selection (MAS), have been instrumental in the development of submergence-tolerant rice varieties. The integration of the Sub1 QTL, especially the Sub1A gene, into high-yielding rice varieties has led to significant advancements in breeding submergence-tolerant cultivars. These genetic improvements provide a promising solution to mitigate the detrimental effects of flooding on rice production, ensuring the stability and sustainability of this essential crop in the face of changing climate conditions. This review discusses various mechanisms adapted by rice and genetic advancements aimed at enhancing submergence tolerance in rice to secure food production for future generations.

Increasing Farmers Income through Demonstration of Climate Resilient Technology

The project TDC-NICRA (National Innovations on Climate Resilient Agriculture) was initiated in KVK, Dhemaji from 2021-22 in Magurmari village of Simen-Chapori Block under the District Dhemaji. The village was affected by flood every year leaving the villagers in a state of destitute. Majority of the farmers of Magurmari village were marginal farmer. Flood, irrigation, water conservation, diseases infestation on plant and occupational migration were the major problem of the village due to which crop failure occurs which leads low income of the farmers. To establish climate resilient agriculture in Magurmari village Demonstration on submergence tolerant rice variety ‘Ranjit sub-1’, medium duration rice variety Numoli, Cultivation of megha turmeric through organic mulching, cultivation of rabi vegetables using paddy straw as organic mulch and Low cost raised bed vermicompost production interventions were taken up in magurmari village. The study revealed that these climate resililient technology weer provd to be boom in magurmari village which help the farmers to increase the farm production and their income to a great extent.

Halopriming in the submergence-tolerant rice variety improved the resilience to salinity and combined salinity-submergence at the seedling stage

The role of halopriming in alleviating the detrimental effects of salinity and combined salinity-submergence was evaluated using two rice genotypes, “IR06F148” (anaerobic germination + submergence tolerant [Sub1]) and “Salt-star” (salt tolerant) with contrasting levels of tolerance. Nonprimed seeds and those primed with 1% calcium chloride (CaCl2) were germinated, and the seedlings were exposed to salinity (50 or 100 mM sodium chloride [NaCl]) and submergence (nonsaline or saline water). Salinity substantially inhibited plant height, shoot/root dry mass, and leaf area. Priming improved the resilience to 50 mM NaCl by increasing the chlorophyll content and lowering hydrogen peroxide (H2O2) production; and to 100 mM NaCl by increasing the total soluble sugars. However, apparent differences in the responses of primed “Salt-star”, such as an increase in the Na+, K+, and Ca2+ levels, indicated that halopriming differentially affected the response to salt based on the salinity tolerance of the variety. Submergence reduced the shoot biomass, chlorophyll, and photosynthetic efficiency to a greater extent in “Salt-star” than in “IR06F148”. Priming, especially in “Salt-star”, caused a lesser reduction in the chlorophyll (Chl) and maximum quantum yield of photosystem II (Fv/Fm) but increased the total soluble sugars post-submergence, indicating a boost in the photosynthetic efficiency. The responses of the two varieties to submergence depended on their tolerance, and halopriming affected each variety differently. The metabolic and molecular changes induced by halopriming in submergence-tolerant rice may be explored further to understand the underlying mechanisms of improved resilience.

Development of Submergence Tolerant Rice Variety BRRI dhan79 for Flash Flood Ecosystem of Bangladesh

Tolerance to submergence stress is an important breeding objective for the areas where rice cultivars are subjected to complete inundation for a week or more. Submergence tolerance is an important trait for rice (Oryza sativa L.) in the flash flood-prone ecosystem. The trait is largely controlled by a major gene designated as Sub1 located on chromosome 9. Submergence of rice (Oryza sativa) by flash flooding is a major constraint to rice production in Bangladesh. Quantitative trait loci analyses have revealed that a large portion of this variation in submergence tolerance can be explained by Sub1. A newly released submergence tolerant rice variety namely BRRI dhan79 was developed by hybridization between BRRI dhan49*6/BRRI dhan52 through Marker Assisted Backcrossing and selection method where BRRI dhan52 (submergence tolerant mega variety in Bangladesh) used as Sub1 donor. It can tolerate upto three weeks complete submergence at vegetative stage whereas Sub1 donor mega variety BRRI dhan52 can tolerate on an average two weeks complete submergence condition. It can also tolerate 50-60 cm water stagnation for 15-20 days after de-submergence. The variety has satisfactorily been passed in the proposed variety trial conducted in flash flood prone farmers' field in Bangladesh. As a result, the National Seed Board (NSB) of Bangladesh approved this rice variety for commercial cultivation for the flash flood affected rainfed lowland ecosystem (Transplanted Aman season) in 2017. It meet up all the trait of modern plant likely medium plant heihght (112 cm), strong and stature culm structure, erect flag leaf with stay green leaf at maturity stage and high yield potential with 140 days growth duration (in case of three weeks submergence mature by 160 days). It can produce 5.5 t/ha grain yield under non-stress condition and 4.0-4.5 t/ha yield under three weeks submergence condition. The grain shape of the variety is medium bold. The rice production scenario in flash flood affected region of Bangladesh has been remarkably improved after releasing this rice variety. It has not only change the socio-economic status of farmers but also sustaining food security.

A participatory framework for prioritizing climate-smart agriculture innovations in rice-based systems: A case study of Mali

Alleviating the climate-related constraints faced by agri-food systems in sub-Saharan Africa requires an accelerated adoption of climate-smart agriculture (CSA) innovations by farmers. However, little is known about the best-bet (most appropriate) CSA innovations, and the enabling conditions for their widespread adoption in a given biophysical and socioeconomic context. The objectives of this study were to identify the best-bet CSA innovations and the barriers, incentive mechanisms, and roles of institutions in widespread adoption in the four rice growing environments in Mali (irrigated lowlands, rainfed lowlands, rainfed uplands, and submergence systems). Data were collected from stakeholder's consultations to assess CSA innovations using four climate-smart performance indicators (productivity, income, adaptation, and mitigation) and four implementation feasibility indicators (technology cost, technical feasibility, gender inclusivity, and market demand). The best-bet CSA innovations included drought- and submergence-tolerant rice varieties, perennial rice, and rice-vegetable rotation in irrigated lowlands; drought-tolerant rice varieties, rice-tuber, rice-vegetable, and rice-legume rotations in rainfed lowlands; drought-tolerant rice varieties and mulching in rainfed uplands; and submergence-tolerant rice varieties, perennial rice, and integrated rice-fish in submergence systems. The average perceived adoption level of CSA innovations by farmers in the rice-growing environments was low, ranging from 7 to 19 % due to the lack of finance, technical knowledge, machinery, fertilizer, and quality seeds. Governments, farmers’ organizations, and research and academic institutions were identified as critical actors in the wide spread adoption of CSA innovations. The framework used in this study can be used to identify and invest into locally relevant best-bet CSA innovation packages.

Submergence-tolerant rice varieties and mechanical transplanting for intensification of rice-rice cropping systems in Assam

Variable climate resulting in floods, and labor-intensive manual rice transplanting are the major challenges in rice cultivation in Assam, India. Our study aimed to improve rice-rice systems productivity through submergence-tolerant rice varieties (STRVs) and mechanical puddled transplanted rice (MTR). On-farm experiments were conducted in four rice seasons over two years (2018-19 and 2019-20) in 15 districts where rice-rice is the dominant cropping system. We evaluated best management practices (BMPs- a combination of STRVs and MTR) against farmers practice (FP-local popular varieties and manual puddled transplanted rice (PTR)). The study also carried out mixed model to assess the unequal distributions of treatments, 127 sites under BMPs and 392 sites under FP. Our results showed that BMPs increased rice grain yield by 25% (1.11–1.14 ​t ​ha−1) and net margin by 68–90% (290–320 USD ha−1) over FP across the seasons. The BMPs also had less variable cost by 59–67 USD ha−1 compared to FP. The adoption of BMPs in rice-rice system increased the system productivity by 2.25 ​t ​ha−1 and net margin by 610 USD ha−1. We conclude that rice-rice system productivity can be increased by adoption of BMPs in Assam. However, scaling of BMPs requires awareness and access to seeds of submergence-tolerant rice varieties and mechanical transplanters.

Optimizing the use of submergence and drought tolerant rice varieties to reduce the impact of climate change on swampland

The swamplands are one among the possibe suboptimal land for agriculture. The land consists of tidal swamplands and freshwater land that are wide obstainable in Indonesia. The hydrotopography of tidal swampland is powerfully influenced by tide and neap tide of water, whereas in freshwater land it’s for the most part determined by precipitation. Drought, flooding or deep inundation, and shifts in rainfall patterns as a result of extreme temperature change have an impact on agriculture in decreasing food crop production, significantly for rice in swamplands. One strategy in anticipating the impact of climate change in agriculture, particularly food crops (rice) is to use submergence and drought tolerant varieties still as early maturing rice varieties. Rice varieties tolerant of submergence in swamplands like Inpara 3, Inpara 4, Inpara 5, Inpari 29, and Inpari 30 Ciherang sub1. Whereas drought tolerant varieties such as Inpari 18, Inpari 19, Inpari 20, Inpago 4, Inpago 5, Inpago 6, Inpago-8, and Inpago Lipigo-4. In addition to avoiding drought, early-maturing aged rice varieties such as Hipa 6 Jete, Inpari Si Denuk are often used, Inpari-34 Salin Agritan, Cakra Buana Agritan, Inpari 12 and Inpari 13. The purpose of this paper is to explain how planting submergence and drought-tolerant rice varieties can reduce the effects of climate change on swamp agriculture. It is expected to significantly reduce the effects of climate change for agriculture in swamplands by treating submergence and drought tolerance and early maturing varieties.

Submergence Tolerance in Rice (Oryza sativa L.) Genotypes at the Seedling Stage: A Combined Approach of Morphological and Molecular Characterization

Background: Rice (Oryza sativa L.) is the major cereal crop often suffers from submergence in the rainfed growing situation of India and South East Asia. Developing rice cultivars with tolerance to submergence is the best strategy to circumvent the situation. In Eastern India a vast reservoir of rice genotypes exists grown in diverse agro-climatic situation under rainfed condition. Screening rice genotypes under submergence stressed condition by observing morphological traits combined with molecular marker approach helps to identify the genotypes having innate capacity to survive under flooding condition more precisely than either of the approach alone. The present study was framed to identify the landraces and genotypes having the presence of desired genes which will helpful for future breeding program. Methods: Fifty rice (Oryza sativa L.) genotypes were evaluated for submergence tolerance using both morphological and molecular characterization in the field and laboratory respectively. Six stress indices, namely elongation%, survival%, mortality%, relative growth index, dry mass% and recovery rate, were examined in the field seven days and fourteen days after submergence. The genotypes were screened with SSR markers to identify the presence of the desired gene. Result: Based on morphological and molecular screening, out of all rice genotypes, Brahmabalak, Jaladhi 1-2, Jaldubi, Kerala Sundary, China IRRI, Sonachur, Pravat, Pankaj, Ranjit SUB1 and Bahadur SUB1 showed higher levels of tolerance to submergence than the tolerant control Swarna SUB1. They have one or more loci different from the SUB1 locus, which can be bred to create improved submergence-tolerant rice varieties with high yield in the rainfed lowland agroecosystem.

Performance of Submergence Tolerant Shallow Lowland Rice Variety Swarna sub-1 under Frontline Demonstrations in East and South Eastern Coastal Plain Zone of Odisha, India

Frontline demonstrations on rice crop in 15.4 ha area using submergence tolerant variety Swarna sub-1 were carried out in participatory mode in farmers’ field during Kharif season of 2016, 2017 and 2018 at Ranapur village of Khordha district under East and South Eastern Coastal Plain Zone of Odisha by University Extension Block programme (UEBP) of Odisha University of Agriculture and Technology, Odisha, India. Major constraints of traditional rice cultivation are low productivity in shallow lowland areas due to lack of knowledge and partial adoption of recommended package of practices by rice growing farmers. Therefore, present demonstration programmes have been undertaken to popularize/introduce stress tolerant rice var. Swarna sub-1 in flood prone and shallow lowland areas of Khordha district of Odisha, India. The present study revealed that there was 20.4% increase in average yield of demonstrated field over the farmers practice field of rice crop. An average yield of 45.68 q ha-1 was recorded in demonstration as compared to 37.84 q ha-1 in farmers practice during consecutive three years demonstrations. It might be due to considerable variation in the extent of adoption of improved/recommended technology which was resulted lower yield in farmers practice. Average technology gap, extension gap and technology index was found 12.32 q ha-1, 7.84 q ha-1 and 28.39%, respectively. The demonstrations with improved practice gave higher net return of Indian Rupee (INR) 18180, 26538 and 35605 ha-1 as compared to farmers practices with INR 12987, 16361 and 17294, respectively during Kharif seasons of 2016, 2017 and 2018. The benefit cost ratio (B:C ratio) of rice cultivation under improved practices were found to be 1.42, 1.60 and 1.80 as compared to 1.31, 1.38 and 1.39 under farmers practices. Moreover, the demonstration practice showed maximum 105.88% increase in net returns over farmers practice.

Resilient Fertilization Strategies to Enhance Rice Productivity in Submergence-Prone Areas

Previous efforts to mitigate the negative impacts of submergence on rice production have focused mainly on varietal improvement. Synergistic effects of submergence-tolerant rice varieties and appropriate fertilizer management strategies are critical to enhance resilience of rice to submergence.

Smallholder adaptation to flood risks: Adoption and impact of Swarna-Sub1 in Eastern India

Climate change and the consequent increase in the incidence of drought and flood will remain a major threat to smallholders. Hence, it is crucial to adopt an appropriate adaptation strategy to overcome this threat and increase farmers’ income. Because seed is a primary input, the adoption of stress-tolerant rice varieties is a potential mitigation strategy to combat climate risks. In this context, the present study is carried out among paddy farmers in the flood-prone region of Eastern India to understand the adoption and impact of submergence-tolerant rice variety Swarna-Sub1 on yield and income. The study reveals that the adoption of Swarna-Sub1 varies significantly across eastern India. Education, primary occupation, credit, social group, cultivated land, and access to information on stress-tolerant rice varieties significantly influence the adoption decision. Endogenous switching regression estimates revealed that the expected paddy yield of Swarna-Sub1 adopters in an actual scenario and for non-adopters in a counterfactual scenario is significantly higher than for their counterparts. The average treatment effect confirms that the benefit of cultivating Swarna-Sub1 is much higher in submergence conditions than in normal conditions. An additional 19.0% and 48.2% of paddy yield and income is obtained respectively by cultivating Swarna-Sub1 in flooded conditions.

Does wet seeding combined with Sub1 varieties increase yield in submergence prone lowlands of West Africa?

Early season flash flooding and submergence greatly impair rice production in the rainfed lowlands of West Africa. Here, rice establishment is by transplanting into puddled soil. Crops established during the early part of the rainy season are adversely affected by submergence, while delaying transplanting until the flood waters have receded results in the use of old seedlings and terminal drought stress. While the use of submergence tolerant (Sub1) rice varieties can greatly reduce the yield loss caused by 1–2 weeks of early season submergence, changing to wet seeding at the start of the rainy season may confer additional advantages. Elsewhere, wet seeding has been shown to enable more timely (earlier) crop establishment and more rapid early growth, and thus the potential to provide greater resilience to submergence. Therefore, the objective of this study was to assess the performance of two Sub1 varieties developed for West Africa (FARO 66, FARO 67) under transplanted and wet seeded conditions, in comparison with the predominant local variety (WITA 9). On-station experiments were carried-out over three seasons (dry 2018, wet 2019, dry 2019) at Mbé Research Station of the Africa Rice Center, Bouake, Cote d′Ivoire. The fields were submerged for 1–2 weeks at 5–7 weeks after seeding, and the wet season crop was sown at the beginning of the rainy season. Yield of the Sub1 varieties was 1.1–4.5 t ha −1 higher than that of WITA 9, depending on season and establishment method. Wet seeding resulted in much higher yields of WITA 9 than transplanting in the wet season, but yield of the Sub1 varieties was not affected by establishment method in any season. However, tiller survival and biomass production of the wet seeded Sub1 crops were less affected by submergence than the transplanted crops. Wet seeding also reduced labour requirement and cost, and increased profitability. Furthermore, establishment of the wet season crop at the beginning of the rainy season would facilitate intensification to two crops per year. Therefore, the adoption of Sub1 varieties, could enable significant progress towards the goal of self-sufficiency in rice production in West Africa. Combining Sub1 with wet seeding would provide further benefits in terms of increased profitability and resilience to flash flooding. • We compared wet seeded and transplanted local and Sub1 rice submerged for 1–2 weeks • Sub1 varieties sown at start of the wet season out yielded WITA 9 by 2.2–4.5 t ha −1 • Yield of Sub1 varieties was not affected by establishment method • Wet seeding reduced labour and increased profit of Sub1 by 445–660 USD ha −1

Geospatial Assessment of Flood-Tolerant Rice Varieties to Guide Climate Adaptation Strategies in India

Rice is the most important food crop. With the largest rain-fed lowland area in the world, flooding is considered as the most important abiotic stress to rice production in India. With climate change, it is expected that the frequency and severity of the floods will increase over the years. These changes will have a severe impact on the rain-fed agriculture production and livelihoods of millions of farmers in the flood affected region. There are numerous flood risk adaptation and mitigation options available for rain-fed agriculture in India. Procuring, maintaining and distributing the newly developed submergence-tolerant rice variety called Swarna-Sub1 could play an important role in minimizing the effect of flood on rice production. This paper assesses the quantity and cost of a flood-tolerant rice seed variety- Swarna-Sub1, that would be required during the main cropping season of rice i.e., kharif at a district level for 17 major Indian states. The need for SS1 seeds for rice production was assessed by developing a geospatial framework using remote sensing to map the suitability of SS1, to help stakeholders prepare better in managing the flood risks. Results indicate that districts of Bihar, West Bengal and Uttar Pradesh will require the highest amount of SS1 seeds for flood adaptation strategies. The total estimated seed requirement for these 17 states would cost around 370 crores INR, less than 0.01 percent of Indian central government’s budget allocation for agriculture sector.

Scenario of Plant Breeding in Nepal and Its Application in Rice

Rice, the number one staple food crop of Nepal, contributes nearly 20% to the agricultural gross domestic product, almost 7% to gross domestic product, and supplies with 40% of the food calorie consumption of Nepalese people. Despite of increasing production, the national demand of rice cannot be fulfilled, and billions of rupees are spent yearly for importing rice from India. This article reviews history, recent scenario, prospects, and importance of rice breeding research in Nepal for self-sufficiency. Though plant breeding inception point in Nepal was 1951, the systematic research in rice was started from 1972 after the establishment of the National Rice Research Program. Introduction and evaluation of high yielding exotic germplasm of rice was the initial rice breeding activities. After analysing several foreign materials, CH-45 variety of rice was first recommended in 1959. Nepal Agriculture Research Council (NARC), the leading organisation for rice varietal improvement to date, has been doing rice research activities such as germplasm conservation, exchange, varietal development, verification of technologies, and knowledge updates in collaboration with various organizations. International Rice Research Institute (IRRI), since 1966, has been playing an important role in Nepal’s rice research. Major plant breeding achievements are introduction of exotic materials and their evaluation, local landraces identification, collection and analysis, crossing of local landraces with exotic genetic materials, heterosis breeding, tissue culture technology, genetic marker technology, and National Genebank. RAPD and SSR, DNA-based markers, are mostly used for diversity appraisal and selecting desirable genotypes. Integration of advanced tools such as genetic engineering, bioinformatics, protoplast fusion, and SNP markers could not be still applied in rice research and development. Hence, emphasis should be given to improve the capacity and abilities of the rice scientists and should release more short duration, drought, and submergence-tolerant rice varieties by optimum utilisation of local landraces combining modern and conventional breeding.

Characterizing the photosynthetic ability of the submergence-tolerant rice variety of Inpari30 via maximum quantum yield performance during transient flooding stress and recovery

Submergence is an environmental challenge for crop cultivation which causes physiological perturbation and yield loss. Tolerant genotypes are characterized by the ability to maintain physiological processes, especially photosynthesis, minimizing the negative effects of flooding stress. This experiment was aimed to examine the photosynthetic ability during submergence and a recovery period in rice variety of Inpari30 (carrying gene Sub1) compared to IR72442 (an elongation type) under control and submergence treatment. A randomized complete block design was employed in this experiment with three replications. The first factor was the environmental condition consisting of control and submergence. The second factor was rice varieties consisting of Inpari30 and IR72442. Fourteen-day-old seedlings were submerged under 35 cm of water depth for 6 days and re-aerated by lowering the water level up to the stem base for 6 days of recovery. Measurement of plant height, SPAD, Fv/Fm and photosynthetic rate were taken continuously from the same plant sample following the experimental stage. The results showed that shoot length increased significantly more in IR72442 than in the quiescent Inpari30. The noticeable decline was observed in the photosynthetic rate of both varieties during submergence with chlorophyll content and chlorophyll fluorescence (Fv/Fm) decreased more severely in IR72442 than in Inpari30. After flooding, Inpari30 adapted quickly to the aerobic environment, as shown by a recovery in Fv/Fm and accumulated dry weight more quickly than IR72442. We concluded that the Sub1 genotype of Inpari30 confers the ability to maintain maximum quantum yield of PSII under conditions of limiting gas exchange for photosynthesis for adapting post submergence

Interéaction of submergence tolerance and drought yield QTLs (Sub1 and qDTYs) enhances morpho‐physiological traits and survival of rice (Oryza sativa L.) under submergence

AbstractClimate change has caused increasing incidences of the extreme flooding around the world, which has impacted rice production, especially in rainfed ecosystems. Breeding for submergence tolerant rice varieties has been conducted to mitigate the adverse effects and help farmers to reduce yield loss. The present study was carried out to introgress the submergence tolerance QTL (Sub1) from IR64‐Sub1 into drought‐tolerant lines; UKM5 and UKM91 possessing the drought yield quantitative trait loci (qDTYs), viz. qDTY12.1 and qDTY3.1, and to evaluate the effects of the combination of these QTLs in improving the morpho‐physiological traits and survival under submergence. UKM5 and UKM91 were selected as the recipient of the Sub1 locus because of the intermediate submergence tolerance they possessed even though they only have qDTY/s. Therefore, the introgression of Sub1 into these lines was hypothesised to enhance survival. Submergence stress was given for 14 days to BC1F4 lines from the two breeding populations. Lines with better survival than the tolerant check, IR64‐Sub1 were selected and evaluated under 18 days of submergence stress. Generally, lines with Sub1 and qDTYs from UKM5*/IR64‐Sub1 and UKM91*/IR64‐Sub1 populations had higher survival rate (SR) of 90–100%, lower shoot elongation percentage (EP) and a smaller percentage of chlorophyll content change (CCC) than IR64‐Sub1. The selected lines also showed a low percentage of non‐structural carbohydrate change (NSCC) which related to the ability to recover after submergence. In both populations, the interaction of qDTY3.1 with Sub1 proved to give the best improvement on EP and CCC. This experiment provides novel findings; that is, the combinations of Sub1 + qDTY12.1 + qDTY3.1 showed high survival rate in the population of UKM5*/IR64‐Sub1, while qDTY3.1 improved SR of the lines from UKM91*/IR64‐Sub1 population to 100%. These results proved that the action of Sub1, qDTY/s and their interaction differ in contrasting population or background. The QTL combinations showed a consistent effect in both submergence experiments and proved the effectiveness of Sub1 and qDTYs combinations in enhancing the morpho‐physiological traits and survival.

Evaluation of excess water tolerant rice varieties Swarna sub-1 and CR-1009 sub -1 under Head to Head Project in East and South- Eastern Coastal Plain zone of Odisha

Flash flood or submergence is a common phenomenon in rice growing rainfed lowland areas that seriously affects crop establishment leading to severe yield losses. A few submergence–tolerant rice varieties have been developed by introgression SUB -1 gene into mega rice varieties of South Asia. Performance of this variety can be further enhanced through adoption of appropriate management practices. Farners Participatorty trials were conducted using Swarna- sub-1 and CR 1009 sub-1 during kharif, 2017 in three adopted villages at Erasama, Kujanga and Raghunathapur blocks of Jagatsinghpur district. Results of this experiment revealed that at recommended doses of N:P:K @ 80-40-40 Kgha-1, transplanting of 30 days aged seedlings and additional N-dose of 20kg/ha at 7 days after receding of flood water resulted in better post submergence recovery and maximum yield. Maximum number of tillers m-2 was recorded in CR 1009 sub -1 followed by Pooja and Swana Sub -1. Rice variety Swarna Sub –I rerecorded an yield of 55.23 q ha -1 which was 14.5% higher as compared to farmers variety Swrana 48.2 q ha -1. The Swarna Sub-1 and CR 1009 sub-1 survived in the flood and gave higher yield under submergence condition in the coastal flood prone area

Innovations and investments for transforming India’s rice economy: Submergence tolerant rice varieties in rainfed lowlands of North-Eastern Uttar Pradesh

The present study provides a brief overview of India’s R&D program and orientation of the public and private research portfolio and investments in reference to the rice research. The farm level and aggregate potential economic benefits from the adoption of improved submergence tolerant rice varieties (Swarna Sub 1, Samba Masuri Sub 1) in the rainfed lowland region of India were estimated based on a field survey conducted in rainfed lowlands of the northeastern region of Uttar Pradesh state. At farm-level, the submergence tolerant varieties had not only 39% higher yield advantage and 63% higher net returns as compared to other popularly grown varieties in the region, but also showed lower yield risk under the prevailing conditions. At the aggregate level, potential benefits from the adoption of these stress-tolerant varieties were also estimated. Farmers’ perception showed that Swarna Sub 1 and Samba Masuri Sub 1 rice varieties are preferred mainly because of their better tolerance to the submergence conditions prevailing in the area during the rainy season. Sarjoo-52 is an old variety but still preferred due to its taste, yield and resistance to pests and diseases. The results amply indicate that farmers’ perception of crop varietal attributes influences largely their choice of varieties at the farm level.

Submergence Tolerance in Rice: Review of Mechanism, Breeding and, Future Prospects

Flooding or submergence is one of the major environmental stressors affecting many man-made and natural ecosystems worldwide. The increase in the frequency and duration of heavy rainfall due to climate change has negatively affected plant growth and development, which eventually causes the death of plants if it persists for days. Most crops, especially rice, being a semi-aquatic plant, are greatly affected by flooding, leading to yield losses each year. Genetic variability in the plant response to flooding includes the quiescence scheme, which allows underwater endurance of a prolonged period, escape strategy through stem elongation, and alterations in plant architecture and metabolism. Investigating the mechanism for flooding survival in wild species and modern rice has yielded significant insight into developmental, physiological, and molecular strategies for submergence and waterlogging survival. Significant progress in the breeding of submergence tolerant rice varieties has been made during the last decade following the successful identification and mapping of a quantitative trait locus for submergence tolerance, designated as SUBMERGENCE 1 (SUB1) from the FR13A landrace. Using marker-assisted backcrossing, the SUB1 QTL (quantitative trait locus) has been incorporated into many elite varieties within a short time and with high precision as compared with conventional breeding methods. Despite the advancement in submergence tolerance, for future studies, there is a need for practical approaches exploring genome-wide association studies (GWA) and QTL in combination with specific tolerance traits, such as drought, salinity, disease and insect resistance.

Introgression of bacterial blight resistance gene Xa7 into popular Indonesian rice varieties through backcross and molecular breeding

Bacterial blight (BB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of major diseases in rice production. The BB resistance gene Xa7 is one of effective genes against Xoo strains in Indonesia. This study aimed to introgress BB resistance gene Xa7 into submergence tolerant rice variety Inpara 5 (IR64 Sub1) and brown plant hopper (BPH) resistant rice variety Inpari 13. Stable BB resistant rice lines have been successfully developed after three backcrossing and four generations of fixation (BC3F4). Screening for BB resistance were conducted in generative stage using Xoo strains IV and VIII. The reaction pattern of the backcross lines against these two Xoo strains were similar to the BB resistant parent Conde. The introgression of the Xa7 gene in Inpara 5 and Inpari 13 genome have been confirmed by using SSR markers RM20589 and RM20590; and Xa7 gene specific marker Xa7-LD34. Agronomic characters and grain quality properties of the backcross lines were comparable to the recurrent parents. Other desirable traits from recurrent parents including submergence tolerance and BPH resistance retained in the selected backcross lines. The BB resistance rice lines with popular rice varieties genetic background developed through this study have potential to be released for farmers adoption.