BRRI Dhan29 Research Articles

EFFECT OF SALINITY ON GERMINATION AND SEEDLING GROWTH OF BORO RICE (Oryza sativa L.) VARIETIES

Germination parameters and seedling growth of three varieties of boro rice (V1 = BRRI dhan28, V2 = Sylhet Boro and V3 = Bere Ratna) were studied in three concentrations of NaCl {S0 = control (distilled water), S1 = 75 mM NaCl and S2 = 150 mM NaCl}. Germination test was performed following Petri dish method with Completely Randomized Design (CRD) in three replications. Data were collected on germination (%) and shoot and root lengths. There was a wide variation in germination parameters and shoot and root growth among the rice varieties. In all the germination parameters Bere Ratna was found superior, followed by Sylhet Boro. Generally shoot length of the rice varieties gradually decreased with increasing salinity. The highest shoot length (5.53 cm) was found in Sylhet Boro in control. The lowest shoot length (1.30 cm) was found in BRRI dhan28 at 75 mM NaCl. However, root growth was not influenced by salinity. Root and shoot length were negatively related to salt levels.

Studies on the Quality and Health Status of T. Aman Rice Seeds Collected From Different Sources

A laboratory experiment was carried out at the Professor GAF Seed Pathology Centre and Laboratory of Department of Seed Science and Technology, Bangladesh Agricultural University (BAU), Mymensingh during the period of July 2018 to January 2019 to determine the effect of seed sources on quality and health status in some Transplanted Aman rice varieties in Bangladesh. Among the seed sources, the moisture content was recorded from 10.40% to 13.37%. In case of purity analysis of seed pure seed ranged from 39.23g to 39.94g. Germination test of rice seeds was recorded and the percentage of total number of germination ranged from 55.75% to 93.0%, normal seedling (51.50 % to 86.50%), abnormal seedling (4.75 % to 10.75%), fresh ingeminated seed (1.75% to15.0%), hard seed (0.0 % to 11.75%), dead seed (2.75% to 21.25%), respectively. Vigour index in the seed sources ranged from (1255.80 to 2089.86). In dry inspection test apparently healthy seeds (17.74gto 28.92g), spotted seeds (9.8g to 17.34g), deformed seeds (0.36g to 5.58g), discolored seeds (0.34g to 3.40g), inert mater (0.00g to 0.38g), insect damaged seeds (0.00g to 0.24g) and chaffy seeds (0.08 g to 1.14g) were recorded(2.75% to 21.25%), respectively. In the seed health study, seven species of fungi were recorded. In the seed health test Alternaria padwickii (1.25 % to 5.50%), Aspergilus niger (0.0% to 1.75%), Bipolaris oryzae (0.0% to 1.50%), Curvularia lunata (0.00% to 1.0%), Aspergillus flavus (0.00% to 1.25%), Penicillium sp. (0.00% to 1.50%) were recorded, respectively. Most of the farmers were failed to obtain the quality and good health status. In this study, BRRI dhan34 in farmer's seed recorded the highest performance in the seed sources and the lowest performance was recorded in BRRI dhan49 in farmer's seed. Among the seed sources BR22 of BADC seed (T8) performed the best in respect of seed quality and seed health.
 Vol. 9, No. 2, August 2022: 103-116

Effect on nitrogen use efficiency and yield of rice variety (BRRI dhan50) under different nitrogen fertilizer rates

Effect on nitrogen use efficiency and yield of rice variety (BRRI dhan50) under different nitrogen fertilizer rates

Can nitrogen fertilizer rates affect the yield response of Boro rice (Oryza sativa L.) variety on the Old Brahmaputra floodplain soil of Bangladesh?

This study observed the yield response to nitrogenous fertilizer for a popular Boro rice variety BRRI dhan29 under silty loam texture soil with satisfactory organic matter (2.96%). Sequential elevated doses of nitrogen (N0, N70, N80, N90, N100, and N110 kg ha-1) along with recommended phosphorus (P), potassium (K), and Sulphur (S) significantly increased grain yield […]

Arsenic accumulation in rice: Alternative irrigation regimes produce rice safe from arsenic contamination

The natural occurrence of arsenic (As) in groundwater & soils and its bioaccumulation in rice grains is a major health concern worldwide. To combat the problem, best combination of irrigation management and suitable rice variety altering As content in grains must be ensured. With this aim, a field trial was conducted with two rice varieties and water management including alternate wetting and drying (AWD) and continuous flooding (CF) irrigation regimes with As contaminated groundwater (AsW) and temporarily stored groundwater (TSG) and river water for only CF (as control). Results revealed that As content in different portions of paddy plant was significantly different (P < 0.001) with irrigation practices and rice varieties. AWD irrigation with TSG accumulated lower As in rice grains compared with CF-AsW for both varieties. Data showed that AWD-TSG practice led to 61.37% and 60.34% grain As reduction for BRRI dhan28 and BRRI dhan29, respectively, compared with CF-AsW. For Principle Component Analysis (PCA), first principle component (PC1) explained 91.7% of the variability and irrigation water As, soil total and available As, straw As, root As and husk As were the dominating parameters. With significant (P < 0.05) variation in yields between the genotypes, AWD increased grain yield by 29.25% in BRRI dhan29 Compared with CF. However, translocation factor (TF) and bioconcentration factor (BCF) for both varieties were less than one for all the treatments. The addition of this study to our knowledge base is that, AWD-TSG with BRRI dhan29 can be an As–safe practice without compromising yields.

Combining Ability Analysis and Marker-Based Prediction of Heterosis in Yield Reveal Prominent Heterotic Combinations from Diallel Population of Rice

Combining ability along with heterosis was elucidated in the 21 F1 hybrid population of rice derived from a 7 × 7 diallel mating design. Furthermore, to formulate a strategy for marker-based prediction of heterosis, the molecular genetic diversity (GD) was then surveyed among the seven parental lines with RAPD markers. Analysis of combining ability revealed significant GCA and SCA variances and the ratio between the aforesaid genetic parameter was more than unity for most of the traits signifying the preponderance of additive gene action. Hybrid combination Double Rice × Pokkali was the best specific combiner for the traits pollen fertility percentage (%), panicle length (cm), filled grains/panicle (no.) and grain yield/hill (g) while Muktagacha × BRRI dhan29 and Basmati × Double Rice were the best specific combiners for grain length (mm) and 1000-grain weight (g), respectively. Regarding the magnitude of heterosis, Double Rice × Pokkali exhibited maximum heterobeltiosis for panicle length (33.33%) and the number of filled grains/panicle (144.01%). Furthermore, Pokkali × Chinigura was verified for producing the highest heterobeltiosis for tillers/hill (173.17%), as well as grain yield/hill (71.05%). The heatmap relying on molecular genetic diversity exposed the highest genetic distance between Chinigura and Pokkali followed by Muktagacha and Pokkali. Unweighted neighbor-joining trees clustered the parental lines into three groups indicating the presence of considerable genetic diversity among those seven parental genotypes. A positive and significant correlation was explored between molecular GD with specific combining ability as well as heterosis for all of the traits revealing the huge potentiality of hybrid performance prediction using RAPD markers with the present set of individuals. Thus, exploration of definite genomic regions underlying the candidate genes for respective traits relying on such RAPD-generated data following an advanced molecular marker approach would pave the path of mining out yielder heterotic combinations.

A Highly Salt-Tolerant Bacterium Brevibacterium sediminis Promotes the Growth of Rice (Oryza sativa L.) Seedlings

Soil salinity has emerged as a serious issue for food security due to global climate change. It is estimated that currently about 62 million hectares or 20 percent of the world’s irrigated land is affected by salinity. Salinity is a serious problem in the coastal areas of Bangladesh. Isolation of salt-tolerant plant growth-promoting bacteria (PGPB) and applying them as bioinoculants in crop plants are considered promising and effective biotechnological approaches to combat soil salinity. This study aimed to screen salt-tolerant PGPB from the root, leaf, and rhizospheric soils of rice plants collected from salt-affected coastal areas including Chattogram, Noakhali, Lakshmipur, and Cox’s Bazar districts of Bangladesh and evaluated their performances on the seedling growth of rice. Out of forty-one salinity-tolerant bacterial isolates screened, Brevibacterium sediminis showed salinity tolerance up to 12% NaCl (w/v). In vitro bioassay revealed that B. sediminis promoted the seedling growth of rice cv. BRRI dhan29 (salinity susceptible) and BINAdhan-10 (salinity tolerant), and the growth-promoting effects were higher in BINAdhan-10. This study for the first time identified B. sediminis strain IBGE3C as a salt-tolerant PGPB from a widely cultivated rice variety, BRRI dhan28 in the Lakshmipur district of Bangladesh. Our results suggest that salt-tolerant PGPB isolated from the root, leaf, and rhizospheric soil of rice plants could be used as a low cost and environmentally friendly option for overcoming the detrimental effects of salt stress on rice plants in the southern coastal regions of Bangladesh. However, further studies are needed for assessing the efficacy of B. sediminis on enhancement of salinity tolerance, and growth and yield of rice under salinity stressed conditions.

Polyethylene glycol mediated drought stress impacts on germination, growth and accumulation of proline in rice (Oryza sativa L.)

Drought is one of the major stress factors affecting the growth and development of plants, and is responsible for considerable crop yield losses worldwide. An experiment was conducted to compare three rice (Oryza sativa L.) varieties (BRRI dhan49, BRRI dhan71 and BRRI dhan75) for drought tolerance based on some growth parameters and physiological status in germination stage. Drought stress was imposed by five levels of polyethylene glycol (PEG) (0%, 10%, 15%, 20% and 25%). Rice varieties showed good germination with PEG concentration up to 15%. At 20% PEG concentration, a sharp reduction in germination percentage was observed and the highest germination percentage (55.53%) was found in the variety BRRI dhan71. Seeds of all the varieties treated with 25% PEG did not germinate. Seedling growth in terms of plumule and radicle length, fresh weight and dry weight decreased with increasing drought stress in all the varieties. Among the varieties, BRRI dhan71 was found to be the best at 20% PEG for seedling growth. Drought stress treatments decreased seedling length and weight vigor index in rice, whereas the highest seedling length and weight vigor index were obtained from BRRI dhan71. Accumulation of proline increased along with the increase of PEG concentration. The highest proline accumulation (3.08 mmol g-1 leaf) was obtained from the BRRI dhan71 at the higher treatment (20% PEG). This result suggests that BRRI dhan71 showed best performance under drought stress because of its own nature of tolerance. SAARC J. Agric., 20(1): 107-119 (2022)

Does solar light trap reduce the cost of pesticides used in rice field?

Pesticide application against insect pest infestation is environmentally unsafe and costly. An attempt was taken to evaluate the solar light trap as ecofriendly and cost-effective approach in Transplanted Aman rice (BRRI dhan32) field at Barhatta Upazila (Sub-district) in Netrokona district of Bangladesh. It was found that rice pest like Rice yellow stem borer, Rice leaf roller, Green leaf hopper, Brown plant hopper, Rice leaf miner, Rice gall midge, White leafhopper, Rice bug, Rice ear cutting caterpillar, White-backed planthopper, Rice caseworm, Grasshopper, Rice skipper and Rice beetle were the major insects that captured under the solar light traps. Some beneficial insects were also attracted by the trap these were Ladybird beetle, Water scavenger, Giant water bug, Ground beetle, Rove beetle, Damsel fly. All the harmful and the beneficial insects were belonging the order of Lepidoptera, Hemiptera, Orthoptera, Coleoptera, Diptera and Odonata. Though the mean yield of rice was statistically insignificant in both fields, the light trap installed fields required the less frequency of pesticides than the control fields which ultimately rendered the low pesticides cost in a great extent. On an average 1,034 BDT was reduced in per hectare. SAARC J. Agric., 20(1): 171-183 (2022)

Effect of Sulphur and Boron on Growth and Yield of Boro Rice in Calcareous Soil of Bangladesh

The experiment was constructed with Sulphur (S) and Boron (B) with three doses of each, i.e., S0: without Sulphur (control), S20: 20kg S/ha, S30: 30kg S/ha and B0: without Boron (control), B2: 2kg B/ha, B3: 3kg B/ha to study the effect on Boro rice (cv. BRRI dhan-28). In case of Sulphur, the treatment S20 obtained the maximum plant height (97.811cm), maximum tillers hill-1 (26.184) at harvest, highest panicle length (24.98cm), maximum grains panicle-1 (167.37), maximum 1000-grain weight (27.57 g), maximum grain yield (5.46t/ha) and straw yield (5.71t/ha), maximum biological yield (11.17t/ha) and HI (48.88%). Whereas, maximum filled grains panicle-1 (147.37) and minimum unfilled grains panicle-1 (17.89) were found in S30. In case of Boron, the highest plant height (96.378 cm) was found in B3. Highest number of total tiller hill-1 (25.149), longest panicle (24.17 cm), highest number of total grains panicle-1 (165.78), filled grains panicle-1 (144.04) and minimum unfilled grains panicle-1 (21.74), maximum 1000-grain weight (25.24 g), highest grain, straw and biological yield (4.84, 5.43 and 10.27t/ha, respectively) and highest HI (47.13%) were found in B2.The treatment combination S20B2 performed the best response than other treatments. Plant height was highest (100.30 cm) in S20B3 treatment combination at harvest. However, the maximum tillers hill-1 (28.78) at harvest, highest panicle length (26.94 cm), maximum grains panicle-1 (177.57), maximum filled grains panicle-1 (150.27) and minimum unfilled grains panicle-1 (27.30), highest 1000-grain weight (29.75 g), highest grain, straw and biological yield (6.30, 5.91 and 12.21t/ha, respectively) and higher HI (51.60%) were found in S20B2 treatment combination.

Assessing Silicon-Mediated Growth Performances in Contrasting Rice Cultivars under Salt Stress.

Silicon (Si) application has great potential to improve salt tolerance in a variety of crop plants. However, it is unclear how Si influences the responses of contrasting rice cultivars when exposed to excessive salt. Here, we investigated the functions of Si in alleviating the negative effects of salt stress on two contrasting rice cultivars, namely BRRI dhan48 (salt-sensitive) and Binadhan-10 (salt-tolerant). Rice seedlings was pre-treated with three doses of Si (as silicic acid; 0, 1 and 2 mM) for 14 days at one-day interval before being exposed to salt stress (10 dSm−1) in a sustained water bath system. The results demonstrated that the seedlings of BRRI dhan48 and Binadhan-10, respectively exhibited substantial reductions in shoot height (16 and 9%), shoot fresh weight (64 and 43%) and shoot dry weight (50 and 39%) under salinity. Intriguingly, BRRI dhan48 pre-treated with 1 and 2 mM Si, respectively, showed a higher increase in shoot height (SH) (by 25.90 and 26.08%) as compared with Binadhan-10 (by 3 and 8%) under salt stress compared with their respective controls. Data revealed that a comparatively higher improvement in the growth performances of the salt-induced Si pre-treated BRRI dhan48 than that of Binadhan-10. For example, 1 and 2 mM of Si treatments significantly attributed to elevated leaf relative water content (RWC) (13 and 22%), proline (138 and 165%), chlorophyll a (42 and 44%), chlorophyll b (91 and 72%), total chlorophyll (58 and 53%) and carotenoids (33 and 29%), and recovery in the reductions of electrolyte leakage (13 and 21%), malondialdehyde content (23 and 30%) and shoot Na+/K+ ratio (22 and 52%) in BRRI dhan48 compared with Si-untreated control plants under salt stress. In addition, we found salt-tolerant Binadhan-10 also had enhanced RWC (9 and 19%), proline (12 and 26%) with pre-treatment with 1 and 2 mM of Si, respectively, under salt stress, while no significant differences were noticed in the case of photosynthetic pigments and Na+/K+ ratio. Our results showed that Si supplementation potentiated higher salt-tolerance ability in the salt-sensitive BRRI dhan48 as compared with salt-tolerant Binadhan-10. Thus, Si application could be highly beneficial in the growth recovery of the salinity-affected salt-sensitive high yielding rice cultivars in the saline-prone areas.

Effects of Seed Priming with Proline and Glycine Betaine on Germination, Seedling Growth, and Photosynthetic Pigments of Rice (Oryza sativa) under Chilling Stress

Aims: Rice grown in late Rabi season frequently results poor germination and establishment because of exposure to extreme low temperature or chilling stress. Seed priming is an effective seed treating technique for uniform and good germination in various crops under different abiotic stresses. The present study was undertaken to assess the role of different seed priming agents in seed germination and seedling growth of rice (BRRI Dhan 29) under chilling stress (CS).&#x0D; Place and Duration of Study: a pot experiment was carried out at the Department of Seed Science and Technology, Bangladesh Agricultural University during Late November – Mid December 2021.&#x0D; Methodology: The rice seeds (BRRI Dhan 29) were soaked in different priming agents (hydro-priming, 20 mM proline and glycine betaine) for 30 min. The primed seeds were exposed to cold stress (under 5°C) in the refrigerator. The untreated seeds were used as control.&#x0D; Results: The outcomes shown that proline (Pro) and glycine betaine (GB) priming had a favorable effect on germination and survival rate, shoot and root length, shoot and root weight, and photosynthetic pigments of leaves under CS. Among the treatments, Pro and GB at 20 mM and warm water performed better; while priming with tap water and Pro and GB at a concentration of demonstrated insignificant performance over control but considerable over stress in the majority of the parameters. The findings showed that seed priming generally has a favorable effect on germination and survival, shoot and root length and weight, and leaf chlorophyll content.&#x0D; Conclusion: Proline, betaine, or warm water priming (at 45°C for 5 min.) can be thought of as a lasting priming agent. This means that priming may be an efficient strategy to boost seed germination and better seedling growth of rice under chilling stress.

Evaluation of Aus rice genotypes grown under rainfed and irrigated conditions

Bangladesh must keep increasing the production of rice (Oryza sativa L.), which is consumed by more than half of the world's population in order to ensure a steady supply of food for everyone. A field experiment was conducted to select short durated with high yield potential Aus rice genotypes under rainfed condition in a split plot design with three replications. Two water regimes (irrigated and rainfed) were imposed into main plot and 39 Aus rice genotypes were assigned into sub plots. In order to categorize the genotypes into various groups, multivariate studies including cluster analysis, principal component analysis (PCA), and discriminantfunction analysis (DFA) were carried out using fifteen quantitative plant traits. Results based on agronomic traits, the genotypes were grouped into six clusters. Early maturing genotypes are represented in cluster II, and genotypes with outstanding yield performance under irrigation are grouped in cluster III. Additionally, clusters III and IV indicate genotypes that mature quickly and a high yield potentiality under rainfed conditions, respectively. Biological yield played a very vital role under both irrigated and rainfed conditions. PCA revealed that PC 1, 2, 3, 4, and 5 described 84.90% variation under irrigated and 84.83% variation in rainfed condition, altogether. Stepwise DFA showed function 1 and 2 accounted for a cumulative of 95.40% of total variance in irrigated and of 92.3% variance in rainfed condition. BR24, Rupsail, Kachilon, Kachiloon2, Darial, Katak-Tara2, BRRI dhan43, Bowalia, BRRI dhan55 and BR14 showed the best performance under rainfed condition. The genotypes like Laksmilota, Loroi, Dhala Saita-3 and Kala manik can be used for further study as early maturing genotypes. Ann. Bangladesh Agric. (2022) 26 (1) : 91-111

Estimating the optimum dose of nitrogen fertilizer with climatic conditions on improving Boro rice (Oryza sativa) yield using DSSAT-Rice crop model

This study was conducted at Hajee Mohammad Danesh Science and Technology University, Dinajpur, Bangladesh using the DSSAT-Rice crop model for estimating the nitrogen fertilizer dose of the rice varieties BRRI dhan 28, BRRI dhan 29 and BR16. Three different varieties such as CL448, Basmati-515 and KS-282 were used to calibrate the model. The research used 2 years (2020–2021) weather data and soil data of different layers (0–60 cm). Four different nitrogen fertilizer treatments i.e., nitrogen (N) @ 50 kg/ha; N @ 100 kg/ha; and N @ 150 kg/ha along with control (no nitrogen) were used for running the simulation process. Result showed that BRRI dhan 29 was the best performed variety and the yield was 6000 kg/ha @ 150 kg/ha N fertilizer treatment. In addition, 1:1 graph showed highest simulated grain yield observed 6050 kg/ha with 150kg/ha N fertilizer treatment for BRRI dhan 29. RMSE, nRMSE and d stat values showed tiller number, grain weight, leaf area index and harvest index had excellent performance with the simulated data for the 150 kg N fertilizer treatments. The study revealed that DSSAT crop model could be useful to estimate optimum N dose to obtain the best variety with climate changing.

Genetic evaluation of boro rice (Oryza sativa L.) genotypes under irrigated and rainfed conditions

Drought is a major abiotic constraint for growing rainfed rice in Bangladesh. A set of 18 boro rice genotypes were evaluated under irrigated and rainfed conditions to identify the high yielding and stress tolerant genotypes. The experiment was conducted by using randomized complete block design with three replications. Significant variations were observed among the genotypes both in irrigated and rainfed conditions. The genotypes BRRI dhan55, Gopal Deshi and Soilerpona showed the superior performance in terms of grain yield and yield contributing characters under rainfed condition. Based on stress tolerance index (STI) value, the genotypes BRRI dhan55, BRRI dhan58, Soilerpuna and Gopaldeshi were graded as drought tolerant genotypes. Under rainfed condition, yield per plant showed the positive and significant correlation with flag leaf length, number of primary branches per panicle, number of secondary branches per panicle, number of grains per panicle and thousand-seed weight. Path analysis revealed that the number of primary/secondary branches per panicle, and number of unfilled grains per panicle showed the highest positive and direct effect on grain yield under irrigated condition while Plant height, panicle length and thousand-seed weight had the highest direct but negative effect on grain yield.Thousand seed weight, number of primary branches per panicle and number of unfilled grains per panicle showed the highest positive and direct effect on grain yield under rainfed condition. Based on the results, seven genotypes from among the eighteen tested namely BRRI dhan36, BRRI dhan55, BRRI dhan58, BRRI dhan59, Soilerpona, Gopal Deshi and Borail were identified as drought tolerance genotypes with high yield potential. Bangladesh J. Agri. 2019-2021, 44-46: 77-87

Nitrogen management in boro rice using chlorophyll meter (SPAD) under sub-tropical condition

Nitrogen deficiency in rice has so far received limited attention in Bangladesh. Balanced fertilization is a pre-requisite for better rice production and it is necessary to determine optimum combination of fertilizer dose and varieties. The field experiment was carried out during the period from November 2020 to May 2021 at the Agronomy Field Laboratory, Bangladesh Agricultural University (BAU), Mymensingh to study the SPAD value and yield performance of boro rice varieties at different nitrogen levels. The experiment comprised of four boro rice varieties viz., BRRI dhan28, BRRI dhan58, BRRI dhan74, BRRI dhan81 and four level of nitrogenous fertilizers viz. 50 kg N ha-1, 100 kg N ha-1, 150 kg N ha-1 and 200kg N ha-1. The experiment was laid out in a randomized complete block design with three replications. SPAD value ranged from 34.01 to 42.12 for variety and 37.81 to 42.15 for nitrogen application, while leaf nitrogen ranged from 2.98 to 3.67 % for variety and 2.94 to 3.48%. The yield contributing parameter varied significantly with variety and nitrogen rate. The highest grain yield (6.13 t ha-1) was found in BRRI dhan58 and the lowest (3.89 t ha-1) was observed in BRRI dhan28. In terms of fertilizer management, the highest grain yield (5.35 t ha-1) was obtained due to the application of 150 kg N ha-1 and the lowest grain yield (4.72 t ha-1) was recorded from50 kg N ha-1. The interactive effect of variety and fertilizer application exerted that the yield of BRRI dhan58 with 150 kg N ha-1 was the highest (6.59 tha-1) and the lowest performance (3.42 tha-1) in grain yield was found in BRRI dhan28 with 50 kg N ha-1. Thus, the variety BRRI dhan58 with 150 kg N ha-1 was superior for attaining the highest yield.

Genetic Mapping to Detect Stringent QTLs Using 1k-RiCA SNP Genotyping Platform from the New Landrace Associated with Salt Tolerance at the Seedling Stage in Rice

Rice is the world’s most important food crop, providing the daily calorie intake for more than half of the world’s population. Rice breeding has always been preoccupied with maximizing yield potential. However, numerous abiotic factors, such as salt, cold, drought, and heat, significantly reduce rice productivity. Salinity, one of the major abiotic stresses, reduces rice yield worldwide. This study was conducted to determine new quantitative trait loci (QTLs) that regulate salt tolerance in rice seedlings. One F2:3 mapping population was derived from a cross between BRRI dhan49 (a popular but sensitive rainfed rice variety) and Akundi (a salt-tolerant rice landrace in Bangladesh used as a donor parent). The 1k-Rice Custom Amplicon (1k-RiCA) single-nucleotide polymorphism (SNP) markers were used to genotype this mapping population. After removing segregation distortion and monomorphic markers, 884 SNPs generated a 1526.8 cM-long genetic linkage map with a mean marker density of 1.7 cM for the 12 linkage groups. By exploiting QGene and ICIM-ADD, a sum of 15 QTLs for nine traits was identified in salt stress on seven chromosomes. Four important genomic loci were identified (qSES1, qSL1, qSUR1 and qRL1) on chromosome 1. Out of these 15 QTLs, 14 QTLs are unique, as no other study has mapped in the same chromosomal location. We also detected 15 putative candidate genes and their functions. The ICIM-EPI approach identified 43 significant pairwise epistasis interactions between regions associated with and unassociated with QTLs. Apart from more well-known donors, Akundi serves as an important new donor source for global salt tolerance breeding initiatives, including Bangladesh. The introgression of the novel QTLs identified in this study will accelerate the development of new salt-tolerant varieties that are highly resistant to salt stress using marker-enabled breeding.

Adoption Trend of Climate-Resilient Rice Varieties in Bangladesh

Rice is a major crop in Bangladesh that supports both food security and livelihoods. However, a need remains for improved productivity and adaptation to the risks associated with climate change. To accomplish this, the increased adoption of climate-resilient and high-yielding rice varieties can be beneficial. Therefore, we conducted a study in Bangladesh over three consecutive years: 2016, 2017, and 2018. The scope of the study included the major cropping season (wet), Aman. The yield advantages of climate-resilient rice varieties were evaluated and compared with those of the varieties popular with farmers. We included new stress-tolerant varieties, such as submergence-tolerant rice (BRRI dhan51 and BRRI dhan52) and drought-tolerant rice (BRRI dhan56 and BRRI dhan71), along with farmer-chosen controls, in the study. We conducted the evaluation through on-farm trials to compare the varieties in both submergence- and drought-affected environments. The seasonal trials provided measured results of yield advantages. The participating farmers were also studied over the three-year-period to capture their varietal adoption rates. We calculated both the location estimated yield advantages (LEYA) and the location observed yield advantages (LOYA). The results revealed that, under non-stress conditions, the grain yields of climate-resilient varieties were either statistically similar to or higher than those of the farmer-chosen controls. Our study also revealed a year-to-year progressive adoption rate for the introduced varieties. The study suggests that the wide-scale introduction and popularization of climate-resilient varieties can ensure higher productivity and climate risk adaptation. The close similarity between LOYA and LEYA indicated that the observational and experiential conclusions of the host farmers were similar to the scientific performance of the varieties. We also found that comparison performed through on-farm trials was a critical method for enhancing experiential learning and obtaining an accurate estimation of yield advantages.

Phenotypic and Molecular Characterization of Rice Genotypes’ Tolerance to Cold Stress at the Seedling Stage

Rice plants are affected by low-temperature stress during germination, vegetative growth, and reproductive stages. Thirty-nine rice genotypes including 36 near-isogenic lines (NILs) of BRRI dhan29 were evaluated to investigate the level of cold tolerance under artificially induced low temperature at the seedling stage. Three cold-related traits, leaf discolouration (LD), survivability, and recovery rate, were measured to determine the level of cold tolerance. Highly significant variation among the genotypes was observed for LD, survivability, and recovery rate. Three NILs, IR90688-74-1-1-1-1-1, IR90688-81-1-1-1-1-1, and IR90688-103-1-1-1-1-1, showed tolerance in all three traits, while IR90688-118-1-1-1-1-1 showed cold tolerance with LD and recovery rate. IR90688-92-1-1-1-1-1, IR90688-125-1-1-1-1-1, IR90688-104-1-1-1-1-1, IR90688-124-1-1-1-1-P2, IR90688-15-1-1-1-1-1, and IR90688-27-1-1-1-1-1 showed significantly higher yield coupled with short growth duration and good grain quality. Genetic analysis with SSRs markers revealed that the high-yielding NILs were genetically 67% similar to BRRI dhan28 and possessed cold tolerance at the seedling stage. These cold-tolerant NILs could be used as potential resources to broaden the genetic base of the breeding germplasm to develop high-yielding cold-tolerant rice varieties.

Effect of Nitrogen on the Growth and Yield of Local Aman Rice Cultivar

To identify suitable nitrogen management practices for local fine and aromatic rice cultivars an experiment was carried out at Farmer’s field at Jointapur, Sylhet region of Bangladesh during the period from August 2017 to December 2017. The experiment was replicated thrice in randomized complete block design assigning factor A: rice cultivars viz. Beruin (V1), Moinasail (V2), Nagrasail (V3) and, BRRI dhan49 (Control, check variety) (V4) and factor B: N sources viz. N 100% chemical (F1) , 50% N from FYM + 50% from Urea (F2) , 50% N from Vermicompost+ 50% from Urea (F3) and farmers practice (F4). Nutrients P,K, S and Zn (100%) were supplied from chemical sources of triple super phosphate, muriate of potash, gypsum and zinc sulphate, respectively. Only N was supplied from different organic and inorganic (urea) sources. Fertilizers were applied at the rate of 140-33-38 kg ha-1 of NPK for farmers’ practice, 90-15-60-12-1 kg ha-1 N, P, K, S and Zn for the variety of BRRI dhan49 and 45-9-33-9-1 kg ha-1 N, P, K, S and Zn for 3 local rice varieties. The results indicate that, BRRI dhan49 (V4) gave the highest yield (2.97 t ha-1) among the varieties. Among the local varieties Nagrasail (V3) gave the highest yield (2.24 t ha-1). In case of farmers practice, highest grain yield was obtained F4 (3.50t ha-1) followed by F1 (2.32 t ha-1). Interaction effect also revealed, the highest grain yield (3.23 t ha-1) in (V4× F4). Among the local varieties Nagrasail gave highest grain yield (2.58 t ha-1) along with F4. Farmer’s practice fertilizer management is a promising option, and Nagrasailis the best one for local T. aman cultivars cultivation in Sylhet region of Bangladesh.