Bangladesh Rice Research Institute Research Articles

Study of Genetic Diversity of Aromatic Rice Genotypes Using Random Amplified Polymorphic DNA Markers

The study of genetic variation in aromatic rice is necessary for enhancing and preserving its genetic makeup. In this study, we amplified four Random Amplified Polymorphic DNA (RAPD) markers from the genomes of 11 different aromatic rice genotypes in order to evaluate the genetic variation and relatedness in aromatic rice. The genotypes were collected from different sources- five of which were obtained from the Bangladesh Rice Research Institute, one from the Bangladesh Institute of Nuclear Agriculture, and the remaining five were local genotypes. In RAPD profiling, twenty-seven of the thirty-six bands that were generated by the four primers were polymorphic, resulting in an estimated average polymorphism of 47.22 percent. The average value of the polymorphic information content was 0.309 with a range from 0.165 to 0.456, indicating that the primers were effective to detect genetic diversity between the genotypes. The genetic diversity and Shannon information index across all of the genotypes and primers were 0.176 and 0.260, respectively, which indicated that there was a certain amount of genetic variation in the studied aromatic rice genotypes. Kalizira and Binadhan-9 genotypes had the smallest genetic distance (0.057), while it was the highest (0.406) between the BRRI dhan 34 and BRRI dhan 50. The genotype pairs BRRI dhan 38 vs BRRI dhan 34, BRRI dhan 38 and Kalizira, and Zirakatari and Kalizira had also a higher level (0.365) of genetic distances. The genotypes were grouped into two main clusters in the UPGMA dendrogram. Cluster I included five genotypes: BRRI dhan 34, Basmoti, Atashail, Kalizira, and Binadhan-9. Cluster II included remaining six genotypes: BR5, BRRI dhan 38, BRRI dhan 50, Uknimodhu, BRRI dhan 37, and Zirakatari. Documentation of the genetic variation and relatedness among the aromatic rice genotypes under this investigation could be useful for future research into the development of aromatic rice and related fields. J Bangladesh Agril Univ 22(3): 277-284, 2024

Morpho-molecular characterization of fungi associated with seeds of hybrid rice varieties in bangladesh

Rice, as the dominant crop in Bangladesh, is vulnerable to various fungal pathogens. Many of these pathogens infect the seeds, which can later transmit diseases and serve as an efficient means for spreading seed-borne pathogens over long distances. In this study, seven hybrid rice varieties, specifically BRRI Hybrid Dhan 101 through BRRI Hybrid Dhan 107, were collected from the Bangladesh Rice Research Institute (BRRI) to detect and identify seed-borne fungi using both morphological and molecular techniques. Fourteen fungal species were isolated from the selected rice varieties using “Tissue planting method” and “Blotter method”, of which 4 fungal isolates were identified by molecular techniques. Molecular characterization of the isolates was conducted based on the sequence information of internal transcribed spacer (ITS) regions. The sequences obtained using the ITS1 and ITS4 primers were compared with those in the NCBI GenBank using BLAST analysis. Hybrid rice is comparatively more advantageous than inbreed rice because of its high yield, shorter plant life, and higher assimilation translocation. Therefore, it is crucial to identify and manage the pathogenic fungi associated with the seeds to ensure good seed quality, which can contribute to improving the economy of Bangladesh. Bangladesh J. Bot. 53(3): 511-518, 2024 (September)

Development of Iron and Zinc Biofortified Rice Variety for Nutrition Improvement in Bangladesh

Depleting micronutrients such as iron and zinc poses a serious risk to a population’s health in regions where nutrient-rich meals are unavailable, such as Bangladesh. We can engross the essential minerals using biofortified rice varieties enriched with essential minerals. We experimented to develop and evaluate a new high-yielding rice variety, Advanced Chemical Industries (ACI) dhan1, specifically for the rainy season in Bangladesh. We used high-yielding rice parent lines with high iron and zinc in the hybridization process, then grew and selected the resulting breeding lines during the rainy season of Bangladesh to identify the most suitable rice lines for the rainy season. The plant height and days to maturity traits were the same as shown in both cultivars, ACI dhan1 and Bangladesh Rice Research Institute (BRRI) dhan62 (standard check), which are 104 cm and 103 days, respectively. On the other hand, ACI dhan1 produced 6.05 tons per hectare, and BRRI dhan62 yielded 4.33 tons per hectare. A quality analysis of the grain quantified that ACI dhan1 contained 8.21% protein and 25.12% apparent amylose. Similarly, ACI dhan1 had very high levels of Zn (24.8 ppm) and Fe (9 ppm). We observed a more than 70% improvement in milling capabilities and head rice recovery. In proposed variety trials, the Seed Certification Agency of Bangladesh identified an average yield advantage of more than 10% for ACI dhan1 in 10 locations. National Seed Board, Bangladesh, released it as a candidate for high-iron and zinc-enriched rice variety and approved its extensive cultivation in Bangladesh. Due to its high micronutrient content, excellent agronomic performance, and non-sticky cooking quality, ACI dhan1 presents itself as a variety of choice in Bangladesh’s pursuit of food and nutrition security. Thus, the present study demonstrates the large achievement of biofortification by ACI dhan1 and hence promises to be a strong weapon in the battle against malnutrition.

Impact of Harvesting Time on Grain Yield, Physicochemical Attributes, and 2-Acetyl-1-pyrroline Biosynthesis in Aromatic Rice

Achieving a consistent grain yield while preserving persistent aroma remains a substantial challenge in aromatic rice production in Bangladesh. To address this challenge, a field experiment was conducted at the agronomy research area of Sher-e-Bangla Agricultural University, Dhaka-1207, between 15 June 2022, and 25 November 2022 (Aman season). This study aimed to evaluate the influence of harvesting time on aromatic rice performance. The experiment, following a randomized complete block design with three replications, involved two factors: factor 1 comprised various rice varieties [Bangladesh Rice Research Institute (BRRI) dhan34, BRRI dhan70, BRRI dhan80, and Tulshimala], and factor 2 comprised three harvesting times [3, 4, and 5 weeks after flowering (WAF)]. Results revealed significant impacts of variety and/or harvesting time on grain yield, physicochemical characteristics, and aroma of aromatic rice. Notably, Tulshimala and BRRI dhan80 exhibited superior milling quality, biochemical properties, and aroma characteristics among the aromatic rice types. BRRI dhan70 and BRRI dhan80 displayed higher grain yield when harvested at 5 WAF. However, Tulshimala and BRRI dhan80 showed superiority in grain 2-acetyl-1-pyrroline (2-AP) concentration when harvested 3 or 4 WAF. Earlier harvesting at 3 and 4 WAF resulted in higher percentages of grain 2-AP (60.22% and 53.96%, respectively) compared with later harvesting at 5 WAF (used as check). In conclusion, varying harvesting times markedly impact the yield, physiochemical characteristics, and aroma of aromatic rice varieties, with earlier harvesting beneficial for aroma retention in Tulshimala and BRRI Dhan80 and later harvesting for increased economic yield in BRRI dhan70 and BRRI dhan80.

Effective multidimensional treatment identification of different chemical fertilizers: Response of insect dynamics and rice production

Effective management of fertilizers is essential in influencing the prevalence of insects in rice (Oryza sativa L.) fields. Over two years (2019-20 and 2020-21), an experiment conducted at Bangladesh Rice Research Institute (BRRI), Habiganj, during the boro season aimed to identify the most effective multidimensional treatment (EMT) by testing various combinations of chemical fertilizers and its effect on rice insects. The goal was to optimize rice grain yield while minimizing harmful insect infestation and supporting natural enemies. Eight different chemical fertilizer applications were used as follows: T1 contained a full mix of nitrogen (N), phosphorus (P), potassium (K), and sulfur (S); T2 had PKS but lacked N; T3 had NKS but lacked P; T4 had NPS but lacked K; T5 had NPK but lacked S; T6 had KS but lacked N and P; T7 had PS but lacked N and K; and T8 lacked all four elements - N, P, K, and S.The relationship between the dynamics of harmful insects and natural enemies was highly positively correlated (r = 0.72 to 0.97). In two consecutive growing years, the 2020-21 season exhibited notably higher counts of harmful insects, with Rice Leafroller (RLR) dominating in the booting stage and White Backed Planthopper (WBPH) in mid-tillering, while Green Mirid Bug (GMB) prevailed among natural enemies across both stages, surpassing insect pest counts, notably GMB, Lady bird beetle (LBB), Carabid beetle (CDB), and Staphylinid (STD). However, the yield was notably higher in the 2019-20 growing season despite these pest pressures. Throughout the mid-tillering and booting stages, T1 consistently exhibited the highest average populations of harmful insects and natural enemies, while T7 demonstrated the lowest count of harmful insects, followed by T2 at both growth stages. Additionally, the highest grain yield (GY) was consistently recorded in T1, followed by T5, T6, and T3, with yields of 7.98 t/ha, 7.63 t/ha, 7.38 t/ha, and 7.33 t/ha, respectively. In both stages, beneficial insects prevailed over harmful ones in all fertilizer applications, with significant declines noted in T2 and T7. Factor analysis showed successful selection for EMT in the MGIDI index for all variables except INT and GY during the 2019-20 season, with selection differentials (SD) ranging from −0.10 to 8.29. However, in 2020-21, selection was achieved for all variables with SD ranging from 0.37 to 6.08. According to the MGIDI index, the top-ranked EMTs were identified as T4 and T3 for the 2019-20 period, and T3 and T5 for the 2020-21 period. The EMT shared in both years, T3, proved effective because of its positive impact on enhancing natural enemies throughout both periods (with SD ranging from 4.76 to 8.29 for 2019-20 and 3.03 to 6.08 for 2020-21), and its notable contribution to rice grain yield (SD = 0.37) in 2020-21. This study uniquely integrates EMT to optimize rice grain yield while simultaneously managing harmful insect infestations and supporting natural enemies, addressing a critical need in sustainable rice cultivation. The suggestion is to give preference to fertilizer application T3, which omits P but contains N and K, to improve rice grain yield and boost natural enemies, thereby reducing harmful insect infestation. Moreover, future investigations should concentrate on refining fertilizer blends to strike a harmony between maximizing yield and fostering ecological robustness in rice cultivation.

E2ETCA: End-to-end training of CNN and attention ensembles for rice disease diagnosis1

Rice is one of the most important crops worldwide. Diseases of the rice plant can drastically reduce crop yield and even lead to complete loss of production. Early diagnosis can reduce the severity and help efforts to establish effective treatment and reduce the usage of pesticides. Traditional machine learning approaches have already been employed for automatic diagnosis. However, they heavily rely on manual preprocessing of images and handcrafted features, which is challenging, time-consuming, and may require domain expertise. Recently, a single end-to-end deep learning (DL)-based approach was employed to diagnose rice diseases. However, it is not highly robust, nor is it generalizable to every dataset. Hence, we propose a novel end-to-end training of convolutional neural network (CNN) and attention (E2ETCA) ensemble framework that fuses the features of two CNN-based state-of-the-art (SOTA) models along with those of an attention-based vision transformer model. These fused features are utilized for diagnosis by the addition of an extra fully connected layer with softmax. The whole procedure is performed end-to-end, which is very important for real-world applications. Additionally, we feed the extracted features into a traditional machine learning approach support vector machine for classification and further analysis. To verify the effectiveness of our proposed E2ETCA framework, we demonstrate it on three publicly available datasets: the Mendeley Rice Leaf Disease Image Samples dataset, the Kaggle Rice Diseases Image dataset, the Bangladesh Rice Research Institute dataset, and a combination of these three datasets. On the basis of various evaluation metrics (accuracy, precision, recall, and F1-score), our proposed E2ETCA framework exhibits superior performance to existing SOTA approaches for rice disease diagnosis, which can also be generalizable in similar other domains.

AGRO-MORPHOLOGICAL CHARACTERIZATION AND GENETIC DIVERSITY ASSESSMENT OF NINETEEN BRRI-RELEASED RICE VARIETIES

Knowledge on genetically determined several growth parameters including morpho- physiological and developmental parameters are essential for rice breeding programs. Genetic divergence helps in the development of superior recombinants, which is prerequisite in any crop improvement program. The aim of the present study was to characterize 19 rice varieties based on agro-morphological descriptors and genetic diversity. The experiment was conducted at Bangladesh Rice Research Institute farm, Gopalganj, using a randomized complete block design with three replications. Both the qualitative and quantitative agro-morphological traits were diversified. The observed variations in the qualitative data were primarily accounted for by the blade pubescence, anthocyanin color of the leaf sheath, lemma-palea color, grain tip color, and awning. The top five axes of PCA contributed 81.04% of the total variation. The varieties were divided into five groups based on the cluster. With six genotypes, Cluster IV was the largest group, whereas Cluster I was the lowest with just one genotype. Cluster IV had the greatest intra-cluster distance, whereas clusters IV and I had the greatest inter-cluster distances. Contrarily, cluster IV had the highest cluster means for most of the quantitative characteristics noticed. Once more, grain length was the trait that contributed most to divergence. While considering results from genetic distance, the varieties under cluster IV (BRRI dhan29, BRRI dhan89, BRRI dhan92 BRRI dhan97, BRRI hybrid dhan3, BRRI hybrid dhan5) might be selected for additional breeding after taking the results of the genetic distance into consideration.

Grain yield, cooking quality, and aroma of fragrant rice as affected by nitrogen source and method of application

<p>One constraint is the incapacity of existing agronomic studies on rice yield, aroma, and cooking quality to fully assess the effects of various applications and sources of nitrogen (N) fertilizer. It is challenging for us to understand how different N inputs impact rice's sensory and cooking qualities in addition to crop productivity because of this research gap. So, a two-year pot experiment was conducted at Sher-e-Bangla Agricultural University, Dhaka, under an open field plastic net house from July 15 to December 4 in 2020 and 2021. The study used Bangladesh Rice Research Institute (BRRI) dhan70 as the test crop. The experiment examined two factors: the methods and source of N application. Three methods of N application were tested: 100% soil application (NM<sub>1</sub>), 2% foliar spray at tillering and booting stages (NM<sub>2</sub>), and a combination of 50% soil application and 2% foliar spray at the booting stage (NM<sub>3</sub>). Three sources of N were also evaluated: Urea (NS<sub>1</sub>), ammonium nitrate (NS<sub>2</sub>), and ammonium sulfate (NS<sub>3</sub>). Total 41.0 kg N ha<sup>−1</sup> was applied considering the nitrogen content in Urea (46%), ammonium nitrate (35%), and ammonium sulfate (21%). The experiment followed a randomized complete block design (RCBD) with three replications. The results indicated that the application of N significantly influenced most of the studied parameters. The combined application of N as a foliar dose and soil application, along with ammonium nitrate and ammonium sulfate, showed improved results for various parameters such as gelatinization temperature, gel consistency, protein content, cooking time, imbibition ratio, 2-AP content, grain aroma, and taste of BRRI dhan70 compared to 100% soil application of N. The highest grain yield and 2-AP was observed in the NM<sub>3</sub>NS<sub>3</sub> treatment (35.437 g·pot<sup>−1</sup> and 0.137 µg·g<sup>−1</sup>, respectively) which was statistical similar with NM<sub>3</sub>NS<sub>2</sub> treatment while the lowest yield and 2-AP was recorded in NM<sub>1</sub>NS<sub>1</sub> (24.877 g·pot<sup>−1</sup> and 0.076 µg·g<sup>−1</sup>, respectively).</p>

Determination of Economic Nitrogen Rate for Transplanted Aus Rice Varieties of Bangladesh

A field experiment was conducted at the Agronomy field, Bangladesh Rice Research Institute, Gazipur, Dhaka, from April to September 2019 to determine the economic nitrogen rates for popular transplanted Aus varieties. The experiment was carried out in a randomized complete block design (RCBD), with two factors. Factor A: three varieties as- BR26, BRRI dhan48, and BRRI dhan82; and Factor B: five levels of nitrogen rates as- 0, 40, 60, 80, 100 kg ha−1. The experimental data show the individual effect of variety and nitrogen (N) rate was significant in the case of N concentration, N uptake in grain and straw, and nitrogen harvest index (NHI). Overall, increasing N rate increases grain and straw's concentration irrespective of varieties. But higher N concentration and uptake were observed in the N rate of N60-N100 kg ha−1 in all varieties. Among the varieties, BRRI dhan82 observed higher N uptake (61.23 kg ha−1) in grain. Higher total N uptake was also observed in BRRI dhan48 at 80 kg N ha−1. NHI ranged from 55 to 72 % in different N levels, indicating 55 to 72% of the absorbed N translocated to the grains, and 45% to 32% remained in the dry matter within varieties. The estimated economic nitrogen dose for maximum yield was determined by regression analysis, and found that N rates of BR26, BRRI dhan48, and BRRI dhan82 were 97, 95, and 55 kg ha−1, respectively. The findings of this study indicated that the response of different N rates on three Aus varieties was linear up to 80 kg N ha−1 might be owing to better N uptake that made yield increase after that decreasing.
 Bangladesh Agron. J. 2023, 26(1): 84-95

EFFECT OF FREE-FLOATING PLANTS ON WEED EMERGENCE, GROWTH, AND YIELD OF TRANSPLANTED AMAN RICE VARIETIES

At Sher-e-Bangla Agricultural University’s agronomy field in Dhaka, Bangladesh, a study was carried out from July to December 2019 to determine the suppressing capacity of floating weeds in T. aman rice (Oryza sativa L.). The experiment consisted of two factors, namely, rice varieties (three), including Tulshimala, BR11(Mukta), and Bangladesh Rice Research Institute (BRRI) hybrid dhan6, and weed management (five), including weedy check (control), integrated weed management (IWM) (Pretilachlor 6% + pyrazosulfuron 0.15% and one hand weeding), spreading of Pistia stratiotes, Lemna minor, and Salvinia molesta in 0.5 m2 area in a split-plot design with three replications. The ranking of the relative rate of spreading over the experiment was L. minor > S. molesta > P. stratiotes. A total of six weed species representing five families were found from the transplanting to the later stage of rice growth, where the occurrence of weed infestation related to rice variety and crop growth. BRRI hybrid dhan6 significantly suppressed weeds in related plots. Although weed biomass was significantly reduced, the morphological and biomass characteristics of T. aman rice varieties got disadvantages when grown with P. stratiotes and S. molesta. Cultivation of BRRI hybrid dhan6 and weed control through IWM gave the highest grain yield (5.92 t ha-1). However, the spreading of L. minor facilitated optimal weed control, and good yields were harvested without significant differences, irrespective of varieties. Therefore, competitive weed variety should be considered along with the spreading of L. minor to reduce herbicide loads in the environment and to the evolution of cross-resistant weed populations.

Pesticidal effect of naphthalene and different Botanicals against anguimous grain moth (Sitotroga cerealella)

A lab experiment was conducted during June to October 2021 at Bangladesh Rice Research Institute (BRRI), regional station Rangpur, laboratory to assess the effectiveness of some botanicals i.e., neem (Azadirachta indica), tulsi (Ocimum tenuiflorum) and ginger (Zingiber officinale)) and chemicals (naphthalene) for the management of Anguimous grain moth (Sitotroga cerealella) of rice. The experiment was carried out Complete Randomized Design (CRD) with nine treatments (T1=Control, T2=5 whole dried neem leaf, T3=0.25 ml neem oil, T4=0.25 g ginger powder, T5=0.25 g neem leaf powder, T6= 0.25 g mixture of neem leaf powder and ginger powder, T7=0.25 g Naphthalene, T8= 5 whole tulsi leaf and T9= 0.25 g neem seed powder) and three replications. Study among the nine treatment indicated that T9 (0.25 g naphthalene) showed better performance in case of insect mortality and no F1 emergence followed by T3 (0.35 ml neem oil), T9 (0.25 g neem seed powder) and T6 (0.25 g mixture of neem leaf powder and ginger powder). Moderate performance was found T5 (0.25 g neem leaf powder), T2 (5 whole dried neem leaf) in case of insect mortality and number of F1 emergence. But in case of seed germination T5 (0.25 g neem leaf powder) showed better performance followed by T7 (0.25 g naphthalene), T9 (0.25 g neem seed powder), T6 (0.25 g mixture of neem leaf powder and ginger powder) and T3 (0.25 ml neem oil). So, naphthalene, neem oil, neem seed powder and neem leaf powder considered as the best treatment among nine treatments for the management of the most destructive Anguimous grain moth. Bangladesh J. Sci. Ind. Res. 58(3), 155-162, 2023

Response of Yield and Agronomic Output of Bangabandhu dhan100 under Varying Sowing Window in Cold Prone Rangpur Region

Background: Selection of a suitable planting time is one of the key factors for obtaining a desirable rice grain yield. This study focuses on the effect of planting date on the key agronomic traits and provides useful information on optimal planting window to maximize grain yield of Bangabandhu dhan100 in the cold-prone Rangpur region, Bangladesh. Methods: The study was conducted at the Rangpur regional station farm of the Bangladesh Rice Research Institute from October 2021 to June 2022. The selected cultivar was seeded on eight different dates at a 15-day interval, starting on October 16. Time series data on agronomic parameters including seedling biomass, leaf number of seedlings and tiller number per plant were collected at a 15-day interval. Result: A good relationship was found between accumulated GDD (growing degree days) and the associated leaf number per plant and the highest leaf number was observed with early seeding. Similarly, seedling biomass yield depended on accumulated GDD and it was found to be higher at early seeding than late seeding. The tillering pattern of Bangabandhu dhan100 was influenced by planting dates and reached its peak at 60 days after planting for all seeding dates. The highest tiller number (368/plants) was found when the cultivar was seeded on December 1. Total biomass showed an increasing trend after planting and reached its maximum of 13.9 t/ha with December 1 seeding. Planting time significantly influenced the grain yields and the highest yields were observed during seeding between 1 and 16 December; yields gradually decreased with the advancement of seeding dates. This finding provided a good idea for the selection of an optimal planting time for Bangabandhu dhan100 to maximize grain in the Rangpur region, Bangladesh.

Fabrication and Field Performance of Power Weeder for Mechanized Rice Cultivation in Bangladesh

A study was aimed at modifying and manufacturing a power weeder at the local workshop using locally available material and evaluating its performance in the condition of Bangladesh. The Bangladesh Rice Research Institute's Farm Machinery and Post-harvest Technology (FMPHT) division (BRRI) took the initiative to fabricate a power weeder using locally available materials. In the wetland of the BRRI research field and farmer's field at Jogitola of Gazipur district, the developed power weeder was tested during the boro season of 2017-2018. The average weeding efficiency of the power weeder was 80.38% and 81.43% at the research and farmers' field respectively. The percent of tiller damage was observed 2.78% and 2.81% respectively. 910 m2 h-1 (0.091 ha h-1) was the average effective field capacity of the power weeder. After 5 days, the percentage of weeds revived for power weeder was observed at 32.26% and 34.90% at the BRRI research and farmers' fields, respectively. Weed biomass was found 35.43 gm m-2 in a farmer’s field and 30.88 gm m-2 in the BRRI research field, Gazipur. This machine can be run by one man/woman easily. The weight of the complete weeder is 18.3 kg. The benefit-cost ratio of the weeder is 1.85. Farmers can use this weeder in wetland conditions. In the line transplanted wetland field conditions, the power weeder was found suitable for controlling weeds with minimum standing water. Bangladesh Rice J.26 (1): 47-57, 2022

Recent advances in population improvement through RGA under Irrigated Boro rice breeding program in Bangladesh

Development of new high yielding varieties needs highly accelerated breeding approaches to meet the demand of increased rice production now a days. To address this issue, Rapid Generation Advance (RGA) of segregating rice population and Line Stage Testing (LST) of fixed breeding lines has been adopted as a routine work in Bangladesh Rice Research Institute. In the present study, we described the evidence of advancing a large number of segregating population and high selection pressure at LST to isolate fixed lines in the Irrigated Boro rice breeding program. This program was implemented under development of Favourable Boro Rice and Cold Tolerant Rice. In both programs, wide variation was observed among the number of population and segregating generation at RGA nursery. A total of 62,269 individual progenies from 64 crosses were advanced through RGA in 2019 whereas 12,122 individual progenies from 45 crosses were advanced in 2020 under the FBR program. In contrast, 68,531 segregating progenies from 82 crosses and 15,004 progenies from 52 crosses were advanced through RGA under CTR program during 2019 and 2020, respectively. During LST, selection pressure was imposed for the first time to isolate homozygous lines from a pool of large number of breeding lines. The selection intensity ranged between 0.21-20.1% and 0.6-14.9% for FBR and CTR, respectively. A total of 794 fixed breeding lines having different combinations of favourable alleles of BLB, Blast and different grain quality traits were isolated from 17,633 RGA derived lines. The results obtained from this study suggested that the RGA system has become an effective tool for population improvement in a breeding program. Bangladesh Rice J.26 (1): 33-46, 2022

Period of effective catching of insect pests and natural enemies in light traps

Light trap helps to protect natural enemies and manage destructive insect pests in rice farming ecosystem. Light trapping time at night is not identified, for organic farming in farmers level its essential to identified proper timing at night. The experimental light trap was set up at Sagordi rice farm, Bangladesh Rice Research Institute, Barishal, during T. Aman rice season in 2019-2020. The time of catching insects by light trap were divided in six different times in a night and defined as treatments (T1= 17.20 to 18.20, T2= 18.20 to 19.20, T3= 19.20 to 20.20, T4 =20.20 to 21.20, T5=21.20 to 22.20, T6= 22.20 to rest of night insects caught at light trap) in this study. Each treatment has had four replications. Yellow sticky trap used to catch and trapped insect and natural enemyRice insect pests and their natural enemies were counted and recorded manually. The caught of yellow stem borer increased and green leafhopper were decreased from treatment, T1 to treatment, T6. During dusk to first four hours, the percentage of caught was approximately 69.28% insect pests. Overall, the percentages of insect pests trapping were 89.65% and natural enemies were 10.35% during the experimental period. The ratio of destructive insect pests caught was highest compared to that of natural enemies in light trap of rice ecosystem.

Prevalence of Seed-Borne Fungi Associated With Selected Rice Varieties of Brri

Selected rice varieties such as BR-78, 80, 81, 82, 83, 84, 86, 87, 88 and 89 were used in this experiment to investigate the prevalence of seed-borne fungi. A total of twelve fungi belonging to six genera was isolated from the seeds of selected BRRI (Bangladesh Rice Research Institute) rice varieties by using tissue planting method. They were Alternaria alternata (Fr.) Keissler, Aspergillus flavus Link, A. fumigatus Fresenius, A. niger van Tieghem, A. ochraceous Wilhelm, A. terreus Thom, Curvularia lunaata (Wakker) Boedijn, Curvularia sp. 1, Drechslera oryzae Breda de Haan (Subramanian and Jain), Penicillium sp.1, Penicillium sp. 2 and Rhizopus stolonifera (Ehrenb.) Vuill., Among the isolated fungi A. niger was the most prevalent fungi associated with the seeds of the rice varieties with a mean per cent frequency of 16.93 and the least prevalent fungi was A. ochraceous with a mean per cent frequency of 0.27. Mean per cent frequency of A. niger (16.33) was highest which was followed by A. flavus (7.27), Penicillium sp.1 (5.93), Penicillium sp. 2 (3.27), Drechslera oryzae (2.67) and A. terreus (2.53). Among the identified seed-borne fungi Curvularia lunata and Drechslera oryzae were found as pathogenic and cause seed-borne diseases. J. Biodivers. Conserv. Bioresour. Manag. 2023, 9(1): 61-68

Assessment of Yield Limiting Nutrients through Response of Rice to Nutrient Omission Technique of Shallow Brown Terrace under Madhupur Tract

A field experiment was conducted during Boro 2018-2019 and T.Aman 2019 season at Bangladesh Rice Research Institute, Gazipur to assess the yield limiting nutrients and response of rice to nutrient omission technique for the Boro-Fallow-T. Aman rice cropping pattern. The experiment was set up in a split plot design (RCBD) with three replications. Four fertilizer treatments viz T1=NPK (AEZ basis), T2=N omission (-N), T3=P omission (-P) and T4=K omission (-K) were imposed in the main plots. The rice genotypes viz Nerica Mutant, BRRI dhan28 and BRRI dhan45 in Boro season and in T.Aman BRC245-4-19-2-1, BR11 and BRRI dhan31 was laid in the subplots. Interaction of nutrient omission and rice genotypes showed significant effect on all the tested growth attributes in Boro 2018-19 season. Treatments with ample dose (NPK) show significantly outperformed than N and P omission in respect of the plant height, tiller and panicle number per square meter but no significance differences of growth attributes were observed in case of K omission in Boro season. Varietal influence of different rice genotypes due to ample dose of NPK and their omissions were insignificant but significance influence of grain yield due to nutrient omission was found. Due to P omission, highest yield reduction (80%, BRRI dhan45) was recorded in Boro season. In T.Aman Season, Only N omission significantly produced lowest tiller and panicle number per meter square. Less than 25% of yield reductions due to nutrient omission were recorded in T.Aman season. The overall findings of the study point out that the yield limiting nutrients in Boro season were identified as N and P. However, N and K was found yield limiting nutrient factor in T.Aman season.

Enhancing genetic gain through the application of genomic selection in developing irrigated rice for the favorable ecosystem in Bangladesh.

Increasing selection differential and decreasing cycle time, the rate of genetic improvement can be accelerated. Creating and capturing higher genetic with higher accuracy within the shortest possible time is the prerequisite for enhancing genetic gain for any trait. Comprehensive yield testing at multi-locations at early generations together with the shortest line fixation time can expedite the rapid recycling of parents in the breeding program through recurrent selection. Genomic selection is efficient in capturing high breeding value individuals taking additive genetic effects of all genes into account with and without extensive field testing, thus reducing breeding cycle time enhances genetic gain. In the Bangladesh Rice Research Institute, GS technology together with the trait-specific marker-assisted selection at the early generation of RGA-derived breeding lines showed a prediction accuracy of 0.454-0.701 with 0.989-2.623 relative efficiency over the four consecutive years of exercise. This study reports that the application of GS together with trait-specific MAS has expedited the yield improvement by 117kgha-1·year-1, which is around seven-fold larger than the baseline annual genetic gain and shortened the breeding cycle by around 1.5years from the existing 4.5years.

Paddy Field Water Movement Through Soil Profiles Under Different Water Management Practices: A HYDRUS 1D Model Study

Physical measurement of hydrological processes through soil profile is very complicated and timeconsuming. Complex and coupled physical processes like water movement with soil matric potential in puddled paddy field can be simulated using physical process-based model HYDRUS 1D. The model simulation was setup for the multilayered (different soil materials at 0-15 and 15-30 cm depth) paddy fields having continuous flooded irrigation (CFI) practice and water saving Alternate Wetting and Drying (AWD) practice. Measured soil physical properties of three Bangladesh Rice Research Institute (BRRI) regional station farms (Kushtia, Sirajganj, and Rangpur) were used as model input, initial and boundary conditions configuration. The model was calibrated and validated using the water data of a dry season field experiment in Kushtia. The calibrated (RMSE of 0.54 cm, d of 0.94, NSE of 0.89) water level data validated successfully with observed water level data of AWD practiced paddy field (d of 0.95, NSE of 0.92). Soil water content reached the threshold/critical level in AWD practice (-101 cm of water soil matric potential at 15 cm soil depth) earlier in light textured soil (loam or sandy loam) compared to heavy textured soil (clay). The physical properties of the layered soils (i.e., soil particle size distribution and soil water release curve, SWRC) did not affect much on water movement in CFI practice, but it had substantial impact on field water movement under AWD practice. The change in soil water storage followed the general trend for respective soil water holding and releasing capacity, clay soil was heavier and released water slowly than that of loam or sandy loam soils. The positive water flux above 15 cm of soil profile mainly drove the water flow due to evapotranspiration and soil water and pressure distribution along the soil profile while the negative fluxes below 15 cm of soil depth due to infiltration or percolation contributed as a secondary force. A basic understanding of HYDRUS simulated results would lead to realize the total physiohydrological environment in the paddy field. Bangladesh Rice J. 25 (2) : 57-67, 2021

Low-Cost Solar Pump Irrigation System for Irrigated Rice Production

Irrigation pumps operated by diesel and electricity are commonly used for irrigated rice cultivation, but fuel cost expansion and doubtful accessibility of power hampers the continuous irrigation. A solar pump would be an alternative option for irrigation to contribute in expanding rice production and food security to the growing population. Field experiments were conducted at Bangladesh Rice Research Institute, Gazipur, farm during Boro season from January May in 2015, 2016 and 2017, respectively to determine the economic feasibility of a low cost 1.5 Horsepower (hp ) capacity solar irrigation pump for rice cultivation. BRRI dhan63 was tested under four irrigation treatments as flood irrigation (continuous standing water at 7 cm depth above the soil surface), 3 cm irrigation at saturation level, 3 cm irrigation in AWD (alternate wetting and drying) practice, and 5 cm irrigation in AWD practice. The CROPWAT 8.0 model was used to ascertain crop water requirement (CWR) and irrigation requirement of each rice growth phase in each year using weather data. In 3 cm irrigation in AWD practice, about 1.0 ha of paddy field can be irrigated with the 1.5 hp solar pump without any or a few water deficits in reproductive and ripening phases. In both years, rice yield did not differ among the irrigation treatments. The benefit-cost ratio was 1.09, 1.18 and 1.02 for Aman, mustard and Boro season respectively. A 1.5 hp solar pump is the best feasible when it is used yearround for three or more crops. Although solar pump irrigation system involved higher initial cost, it was found economically sound and environment friendly. Thus, proper policy support is required to encourage solar power utilization for irrigation. Bangladesh Rice J. 25 (2) : 1-10, 2021