Spikelet Sterility Research Articles

Effect of High Nighttime Temperatures on Growth, Yield, and Quality of Two Wheat Cultivars During the Whole Growth Period

It is a consensus that Earth’s climate has been warming. The impact of global warming is asymmetric, that is, there is more substantial warming in the daily minimum surface air temperature and lower warming in the maximum surface air temperature. Previous studies have reported diurnal temperature differences greatly affecting winter wheat yield. However, only a few studies have investigated the impact of global warming on the growth and yield of winter wheat, yet the influence of night warming on quality has not been deeply evaluated. In this study, two wheat cultivars were used as materials: Jimai 44 (JM44) with strong gluten and Jimai 22 (JM22) with medium gluten, to explore the effects of high nighttime temperatures (HNTs) on the growth, yield, and quality of wheat. The results show that HNTs significantly shortened seedling emergence and anthesis periods in both cultivars compared with ambient temperatures (ATs). In addition, HNTs increased the respiration rate at anthesis and grain-filling stages, impeding wheat pollination and grain maturity. HNTs also accelerated leaf senescence and increased the number of sterile spikelets and plant height, but decreased the effective tiller number, the number of spikes per unit area, and grains per spike. As a result, the grain yield of JM22 and JM44 was decreased by 24.6% and 21.2%, respectively. Moreover, HNTs negatively influenced the flour quality of the two wheat cultivars. The current findings provide new insights into the effects of HNTs on the growth, development, yield, and quality of different wheat genotypes during the whole growth period.

Disentangling conflicting molecular phylogenetic signals in nuclear and plastid DNA of the western Eurasian-Mediterranean grass genus Cynosurus and its relatives (Poaceae subtribes Cynosurinae and Parapholiinae)

The western Eurasian-Mediterranean grass genus Cynosurus, comprising about 11 species, is morphologically well delimited by the regular occurrence of conspicuous sterile spikelets distal to the fertile ones on the outer, abaxial side of the inflorescences. However, our molecular phylogenetic study using nuclear ribosomal DNA (ITS, ETS) and plastid DNA sequences (trnL–F, matK) has shown that the genus is not monophyletic in its current delimitation, but consists of three distinct lineages. These lineages were found to be closely related to a group of 6–7 genera taxonomically assigned to the subtribe Parapholiinae. These Parapholiinae genera were consistently monophyletic in our analyses, but the suggested relationships to the three lineages of Cynosurus varied depending on the particular DNA region examined. This was the case for both plastid and nuclear DNA, with cytonuclear discordance and ‘chloroplast capture’ indicating earlier hybridization. Interestingly, hybridization also proved to be the most likely explanation even with regard to the 18S–26S cistrons of the nuclear ribosomal DNA, where an exceptional evolutionary divergence between ITS and ETS was found. The results highlight and illustrate the important role of hybridization in the evolution of grasses. In terms of taxonomy, our findings argue against maintaining a polyphyletic genus Cynosurus s.l. but instead argue for dividing it into three monophyletic genera: Cynosurus s.s., Falona, which is reestablished here, and Ciliochloa, which is described as a new genus. In addition, it is proposed that the two subtribes Cynosurinae and Parapholiinae be combined into a single subtribe Cynosurinae, which is also monophyletic. The possible genetic background of the formation of sterile spikelets and the occasional occurrence of inflorescences with consistently fertile spikelets are discussed. New combinations are Ciliochloa effusa, C. effusa var. obliquata, C. effusa var. fertilis, C. elegans, C. gracilis, C. turcomanica and Falona colorata.

Determination of Optimum Nitrogen Level for Maximizing Yield of Two HYV Boro Rice Varieties in Bogura Region, Bangladesh

Application of N fertilizer is very crucial for rice, but both excessive and mild reduced productivity. A field experiment was conducted during the Boro 2021-2022 season to find out the optimum dose of N fertilizer for higher yield. The trial was conducted in a factorial RCBD design with three replications. Factor A: Two varieties of rice viz. BRRI dhan89 and BRRI dhan100 and B: Five Nitrogen levels i.e., 0, 90, 120, 150, and 180 Kg ha−1. Yield and yield-contributing traits varied significantly with N levels. BRRI dhan89 outyielded BRRI dhan100 due to its varietal potential and longer life cycle. The highest tiller number hill−1, panicle number hill−1, panicle length, filled grain panicle−1, grain yield, biological yield and harvest index and lowest spikelet sterility were obtained from 120 kg N ha−1 irrespective of variety. The result revealed that the combination of both varieties with 120 kg N ha−1 followed by 90 Kg N ha−1 in maximizing rice productivity while avoiding excess use of N fertilizer. Bangladesh Agron. J. 2024, 26(2): 41-48

Mitigation of salt stress in rice (oryza sativa l.) growth and yield in coastal saline soil using crop residue-driven organic amendments under varying moisture conditions

The increasing salinity in coastal areas due to climate change significantly hinders rice (Oryza sativa L.) production, a crucial food source for over half of the global population. This study evaluates the effects of organic amendments and moisture conditions on the vegetative growth and yield of rice varieties in a saline field in the Khulna district of Bangladesh. The field experiment was conducted from February to May 2020, using rice straw compost (RSC), sawdust (SD), rice husk (RH), and mustard seed meal (MSM) at varying rates (0, 5, 10, 15 t ha-1) under moist (70% soil moisture) and saturated (>100% soil moisture) conditions. The experiment featured BRRI dhan 28 (salt-sensitive) and BRRI dhan 47 (salt-tolerant) varieties. Key metrics evaluated in the study included the productive to unproductive tillers ratio (PTR), spikelet sterility, percent filled grains, straw yield, and grain yield. Results indicated significant (p ≤0.05) improvements in PTR, reduction in spikelet sterility, increased grain filling, and higher straw and grain yields with applying organic amendments, especially MSM. The highest PTR for BRRI dhan 47 (0.86) was achieved with MSM at 5 t ha-1 under moist conditions, while BRRI dhan 28 reached a PTR of 0.81 with RH at 10 t ha-1 under saturated conditions. Spikelet sterility was minimized (9/panicle) with MSM at 5 t ha-1 under saturated conditions for both varieties. Percent filled grains peaked (88.9%) with MSM at 5 t ha-1 for BRRI dhan 28. Enhanced straw yields were observed, with BRRI dhan 47 achieving 8.76 t ha-1 with MSM at 10 t ha-1. Grain yield increased significantly, with BRRI dhan 28 yielding 5.75 t ha-1 under similar conditions. The study confirms that organic amendments of MSM > RSC > SD > RH can effectively mitigate salt and moisture stress, thereby improving rice productivity in saline soils. Dhaka Univ. J. Biol. Sci. 33(2): 1-13, 2024 (July)

Study of Genetic Variability in F2 Population for Yield Enhancing Traits under Direct Seed Condition in Rice (Oryza sativa L.)

The present investigation was conducted to assess the variability, frequency distribution of grain yield and yield attributing traits in F2 generation of DRR Dhan 60 × Pusa 44 (NIL). In order to better understand the genetics of DSR and develop rice genotypes that are aerobic conditions-suited, genetic diversity is crucial. The experimental material consists of 236 F2 plants along with parents which were planted in DSR plot at ICAR-IIRR, Hyderabad. Data recorded for the traits viz., Days to 50% flowering, Plant height, Number of tillers per plant, Flag leaf length, Flag leaf width, Number of panicles per plant, Panicle length, Number of spikelets per panicle, Number of filled grains per panicle, Number of chaffy grains per panicle, Spikelet fertility, Spikelet sterility, 1000-grain weight and Grain yield per plant. The traits, number of productive tillers per plant, number of tillers per plant, flag leaf length and grain yield per plant have high genotypic and phenotypic coefficient of variation. For productive tillers per plant, number of tillers per plant, flag leaf length, and grain yield per plant, high GCV and PCV along with high heritability and high genetic advance as a percentage of mean were noted. This suggests an additive type of gene action and that selection for these traits is effective. These findings indicate that, in aerobic conditions, there was adequate genetic diversity for most of the characters under investigation.

Comprehensive studies reveal physiological and genetic diversity in traditional rice cultivars for UV-B sensitivity

Acclimation to crop niches for thousands of years has made indigenous rice cultivars better suited for stress-prone environments. Still, their response to UV-B resiliency is unknown. 38 rice landraces were grown in cemented pots in a randomised block design with three replicates under open field conditions in Sambalpur University in the wet season of 2022. Half of the plants in each of the cultivars were administered UV-B radiation at the panicle emergence stage in an adjustable UV-B chamber permitting sunlight, and the effects of the stress on various morpho-physiological features, such as spikelet sterility, flag leaf photosynthetic and flavonoid pigment contents, and lipid peroxidation activities, were estimated for calibration of stress resistance. The experiment identified Swarnaprabha and Lalkain as the most sensitive and resilient to stress respectively, and the differential response between them was further revealed in the expression of genes related to UV-B sensitivity. Subject to the stress, Swarnaprabha exhibited symptoms of injuries, like leaf burns, and a higher loss of various photosynthetic parameters, such as pigment contents, SPAD and Fv/Fm, ETR and qP values, while NPQ increased only in Lalkain. Exposure to UV-B increased the total phenolic and flavonoid contents in Lalkain while depressing them in Swarnaprabha. Such an effect amounted to a higher release of fluorescent energy in the latter. The levels of expression of gene families controlling flavonoid activation and UV-B signal transduction, such as OsWRKY, OsUGT, OsRLCK, OsBZIP, OsGLP, and CPD photolyase were similar in both the cultivars in the control condition. However, exposure to UV-B stress overexpressed them in resilient cultivars only. The magnitude of expression of the genes and the impact of the stress on photosynthetic parameters, phenolic compounds and pubescent hair structure at the panicle emergence stage could be valid indicators among indigenous rice for UV-B tolerance.

Trait analysis of short duration boro rice (Oryza sativa L.) varieties in northern region of Bangladesh: Insights from heatmap, correlation and PCA

The role of genetic variation is utmost importance in the selection of a desirable genotype for breeding programs. In the northern region of Bangladesh, the performance of five short duration boro rice varieties (BRRI dhan28, BRRI dhan74, BRRI dhan81, BRRI dhan88, and Bangabandhu dhan100) on yield and yield-contributing traits were evaluated in four locations. Yield attributes tiller hill-1 (TN), panicle hill-1 (PN), filled grain panicle-1 (FG), panicle length (PL), 1000-grain weight (TGW), and harvest index (HI), showed a positive correlation with grain yield (GY). Conversely, spikelet sterility (SSP) and unfilled grains panicle-1 (UFG) showed negative associations with grain yield. Principal component analysis (PCA) revealed that the first three components accounted for 89.60% of variability. The highest positive eigenvalue was observed in DF, DM, BY, HI, PN, SY, TN, PL and GY in PC1, indicating their significant influence on the overall genotype variations. PC2 was primarily driven by plant height (PH) and FG, while PC3 driven by TGW and UFG. The results suggest that grain yield is highly influenced by FG, PH, DM, DF, PN, TN, PL, TGW, SY, BY, and HI. These components highlighted the importance in distinguishing rice genotypes with higher grain yield potential. By considering these traits, BRRI dhan74 have outperformed other varieties, followed by BRRI dhan88 and Bangabandhu dhan100. BRRI dhan74 is most suitable for all four location followed by BRRI dhan88. The traits such as PN, PL, FG, TGW, PH, & HI significantly influence rice yield and should be prioritized in breeding programs aimed at developing high-yielding rice varieties.

Higher Grain-Filling Rate in Inferior Spikelets of Tolerant Rice Genotype Offset Grain Yield Loss under Post-Anthesis High Night Temperatures

Increased nighttime respiratory losses decrease the amount of photoassimilates available for plant growth and yield. We hypothesized that the increased respiratory carbon loss under high night temperatures (HNT) could be compensated for by increased photosynthesis during the day following HNT exposure. Two rice genotypes, Vandana (HNT-sensitive) and Nagina 22 (HNT-tolerant), were exposed to HNT (4 °C above the control) from flowering to physiological maturity. They were assessed for alterations in the carbon balance of the source (flag leaf) and its subsequent impact on grain filling dynamics and the quality of spatially differentiated sinks (superior and inferior spikelets). Both genotypes exhibited significantly higher night respiration rates. However, only Nagina 22 compensated for the high respiration rates with an increased photosynthetic rate, resulting in a steady production of total dry matter under HNT. Nagina 22 also recorded a higher grain-filling rate, particularly at 5 and 10 d after flowering, with 1.5- and 4.0-fold increases in the translocation of 14C sugars to the superior and inferior spikelets, respectively. The ratio of photosynthetic rate to respiratory rate on a leaf area basis was negatively correlated with spikelet sterility, resulting in a higher filled spikelet number and grain weight per plant, particularly for inferior grains in Nagina 22. Grain quality parameters such as head rice recovery, high-density grains, and gelatinization temperature were maintained in Nagina 22. An increase in the rheological properties of rice flour starch in Nagina 22 under HNT indicated the stability of starch and its ability to reorganize during the cooling process of product formation. Thus, our study showed that sink adjustments between superior and inferior spikelets favored the growth of inferior spikelets, which helped to offset the reduction in grain weight under HNT in the tolerant genotype Nagina 22.

High night temperature stress on rice (Oryza sativa) - insights from phenomics to physiology. A review.

Rice (Oryza sativa ) faces challenges to yield and quality due to urbanisation, deforestation and climate change, which has exacerbated high night temperature (HNT). This review explores the impacts of HNT on the physiological, molecular and agronomic aspects of rice growth. Rise in minimum temperature threatens a potential 41% reduction in rice yield by 2100. HNT disrupts rice growth stages, causing reduced seed germination, biomass, spikelet sterility and poor grain development. Recent findings indicate a 4.4% yield decline for every 1°C increase beyond 27°C, with japonica ecotypes exhibiting higher sensitivity than indica. We examine the relationships between elevated CO2 , nitrogen regimes and HNT, showing that the complexity of balancing positive CO2 effects on biomass with HNT challenges. Nitrogen enrichment proves crucial during the vegetative stage but causes disruption to reproductive stages, affecting grain yield and starch synthesis. Additionally, we elucidate the impact of HNT on plant respiration, emphasising mitochondrial respiration, photorespiration and antioxidant responses. Genomic techniques, including CRISPR-Cas9, offer potential for manipulating genes for HNT tolerance. Plant hormones and carbohydrate enzymatic activities are explored, revealing their intricate roles in spikelet fertility, grain size and starch metabolism under HNT. Gaps in understanding genetic factors influencing heat tolerance and potential trade-offs associated with hormone applications remain. The importance of interdisciplinary collaboration is needed to provide a holistic approach. Research priorities include the study of regulatory mechanisms, post-anthesis effects, cumulative HNT exposure and the interaction between climate variability and HNT impact to provide a research direction to enhance rice resilience in a changing climate.

Association Analysis in Rice Germplasm Lines for High Temperature Tolerance

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

Response of Boro Rice (cv. BRRI dhan89) Yield to Foliar Application of Micronutrients

Insufficient management of nutrients poses a significant obstacle to achieving sustainable rice production in tropical climates. To address this challenge, an investigation was conducted to find the potential impact of micronutrients on enhancing the yield of Boro rice through foliar application. The study was structured using a randomized complete block design and replicated three times. Field trials were conducted with three micronutrients (Boron, Zinc and Copper) and involved seven treatments, namely control (NPK), NPK + Zinc, NPK + Boron, NPK + Zinc + Boron, NPK + Zinc + Copper, NPK + Boron + Copper, and NPK + Zinc + Boron + Copper. The addition of zinc, boron and copper led to a notable enhancement in the factors contributing to yield. The maximum number of total tillers hill-1 (11.29), effective tillers hill-1 (10.09), panicle length (24.69), grain panicle-1 (138.36), grain yield (5.43 t ha-1) and straw yield (7.22 t ha-1) was resulted when NPK + Zinc + Boron + Copper applied together. The least grain yield (3.64 t ha-1) was produced in control (NPK) owing to lower number of effective tillers hill-1 (7.46), lower number of grain panicle-1 (118.46) and higher number of sterile spikelet panicle-1 (25.46). The findings suggested that the appliance of NPK combined with Zn, B and Cu yielded superior in BRRI dhan89.

Water productivity and yield characteristics of transplanted rice in puddled soil under drip tape irrigation

Lowland rice flooding, while consuming considerable water, has adverse environmental effects, including releasing methane into the atmosphere, aggravating climate change. Several drawbacks can be attributed to water-saving alternatives, such as aerobic rice, whereas rice drip irrigation techniques have been evaluated primarily under aerobic conditions. This study investigated drip tape irrigation technique with different lateral spacings for transplanted rice in puddled paddy soil at the Rice Research Institute of Iran in Rasht over two years (2020 and 2021), compared to intermittent irrigation. In twelve isolated concrete basins, three treatments with lateral spacings of 40 (T40), 60 (T60), and 80 cm (T80), were compared with a fixed five-day period intermittent irrigation (INT). In 2020 and 2021, the INT treatment produced the highest grain yield (3814 and 4758 kg ha−1, respectively) and among drip tape treatments, T40 demonstrated the highest grain yield (3613 and 4020 kg ha−1, respectively), comparable with INT’s yield but with the highest sterile spikelets ratio. In contrast, T80 resulted in the lowest grain weight (2892 and 3653 kg ha−1, respectively) and yield characteristics values, while producing the highest weeds population. Drip tape irrigation significantly reduced water application by 27% and 36% in 2020 and 2021, respectively and T40 achieved the highest water productivity, at 0.68 kg m−3. The economic water productivity estimation of drip tape irrigation can range from 0.11 to 0.51 US$ m−3 in various scenarios, while that of intermittent irrigation remains at 0.25 US$ m−3.

Desempenho de linhagens elite de arroz de terras altas em baixas temperaturas

Abstract The objective of this work was to evaluate the phenotypic performance of elite upland rice lines subjected to different temperature conditions during the booting stage (R2). Eight elite lines from an upland rice breeding program were evaluated under six temperatures: 12, 17, 20, 25, 29, and 32°C. The experiment was conducted in a greenhouse and climatic chambers with photoperiod control. The experimental design was completely randomized, with three replicates. Number of days to flowering, plant height, number of panicles, and spikelet sterility were measured. The upland rice lines do not tolerate the low temperatures of 12 and 17°C, which result in a low performance in yield components and a grain sterility of 100%. The lowest rates of spikelet sterilization occur at the temperatures of 25 and 29°C. Cultivar BRSMG Caçula is a promising candidate to integrate the crop succession system.

Cold-Tolerant and Short-Duration Rice (Oryza sativa L.) for Sustainable Food Security of the Flash Flood-Prone Haor Wetlands of Bangladesh

Rice cultivation in the low-lying basin-like wetlands, known as the Haor, is often affected by early flash floods during the first two weeks of April. The flooding is mainly caused by heavy rainfall and water surging downstream from the Meghalaya hills in India. This flash flood poses a significant threat to rice production, risking the country’s food security. Dry winter (Boro) rice is the primary food source throughout the year in the Haor region. Flash floods are the most catastrophic, affecting about 80% or even the entire rice yield. In 2017, a loss of 0.88 million metric tons of Boro rice in Haor regions cost the nation USD 450 million. To escape flash floods, it is recommended to sow Boro rice earlier, between the last week of October and the first week of November, instead of around 15 November so rice may be harvested by the last week of March before the onset of flash floods. However, early sowing has a possibility of causing grain sterility due to cold spells when the booting and heading stages of rice inevitably coincide with the cold period between 15 January and 7 February. The minimum temperature in the Haor regions ranges from 11 to 15 °C during this time. Rice is especially susceptible to low average temperatures (<20 °C) during the reproductive stage, leading to pollen abortion and the malformation of immature microspores. Low temperatures mainly impact rice cultivation in Haor regions during the reproductive phase, resulting in the degeneration of the spikelets, partial panicle exertion, and increased spikelet sterility, leading to a decrease in grain yield. Over two million hectares of Boro rice have been damaged by extreme cold spells in recent years, resulting in partial or total yield loss. To overcome the threats of flash floods and cold injury, breeding short-duration and cold-tolerant rice varieties is crucial. We assume that an economic benefit of USD 230 million per year could be achieved through the development and adoption of short-duration and cold-tolerant high-yielding rice varieties in the Haor regions of the country. In this review article, the authors summarized the problems and outline a way forward to overcome the flash flood and cold injury of Boro rice cultivation in the Haor districts of the country. Furthermore, the authors discussed the various forms and scenarios of cold damage and the global existence of cold-tolerant rice cultivars. Based on the available data from earlier research, a potential way of mitigating flash floods and cold devastation was suggested.

Mitigation of heat-induced spikelet sterility at flowering by transferring a QTL for the early-morning flowering trait, <i>qEMF3</i>, into the genetic background of <i>japonica</i> cultivars

Mitigation of heat-induced spikelet sterility at flowering by transferring a QTL for the early-morning flowering trait, <i>qEMF3</i>, into the genetic background of <i>japonica</i> cultivars

WATER STRESS IN MODERN UPLAND RICE CULTIVARS: A MULTIVARIATE STUDY BETWEEN PHYSIOLOGICAL TRAITS AND YIELD

Water stress negatively affects upland rice production. The objective of this study was to identify physiological traits that could depict yield responses under water stress conditions. Three modern upland rice cultivars (C) (BRS A501 CL, BRS Esmeralda and BRS Serra Dourada) were subjected to three water availability levels (W): Control (100% of the field capacity throughout the growing cycle) and 70 and 40% of the water applied to the control during flowering. Yield, spikelet sterility, and 1000-grain weight were influenced by the water availability level (p < 0.05), whereas for the cultivar, only 1000-grain weight was significant. The W × C interaction was not significant for the analyzed yield components. Multivariate analysis revealed that well-irrigated plants were positively associated with grain yield and gas exchange traits, whereas the 40% water availability level was highly related to spikelet sterility and the crop water stress index. The best-fitted model for grain yield was obtained using photosynthesis, stomatal conductance, and transpiration (R2 = 0.76). Thus, physiological parameters can be used to explain the variations in upland rice yield under water stress.

Effect of ethyl methanesulfonate mediated mutation for enhancing morpho-physio-biochemical and yield contributing traits of fragrant rice.

Chemical mutagenesis has been successfully used for increasing genetic diversity in crop plants. More than 800 novel mutant types of rice (Oryza sativa L.) have been developed through the successful application of numerous mutagenic agents. Among a wide variety of chemical mutagens, ethyl-methane-sulfonate (EMS) is the alkylating agent that is most commonly employed in crop plants because it frequently induces nucleotide substitutions as detected in numerous genomes. In this study, seeds of the widely consumed Basmati rice variety (Super Basmati, Oryza sativa L.) were treated with EMS at concentrations of 0.25%, 0.50%, 0.75%, 1.0%, and 1.25% to broaden its narrow genetic base. Sensitivity to a chemical mutagen such as ethyl methanesulfonate (EMS) was determined in the M1 generation. Results in M1 generation revealed that as the levels of applied EMS increased, there was a significant reduction in the germination percent, root length, shoot length, plant height, productive tillers, panicle length, sterile spikelet, total spikelet, and fertility percent as compared to the control under field conditions. All the aforementioned parameters decreased but there was an increase in EMS mutagens in an approximately linear fashion. Furthermore, there was no germination at 1.25% of EMS treatment for seed germination. A 50% germination was recorded between 0.50% and 0.75% EMS treatments. After germination, the subsequent parameters, viz. root length and shoot length had LD50 between 05.0% and 0.75% EMS dose levels. Significant variation was noticed in the photosynthetic and water related attributes of fragrant rice. The linear increase in the enzymatic attributes was noticed by the EMS mediated treatments. After the establishment of the plants in the M1 generation in the field, it was observed that LD50 for fertility percentage was at EMS 1.0% level, for the rice variety. Hence, it is concluded that for creating genetic variability in the rice variety (Super Basmati), EMS doses from 0.5% to 0.75% are the most efficient, and effective.

Morpho-physiological and yield attributes of boro rice varieties as influenced by different nitrogen sources

The present study was carried out at the Research Field of Sher-e-Bangla Agricultural University (SAU), Dhaka during Boro season, 2021-2022 to discover the best nitrogen source for enhancing Boro rice grain production. The experiment consisted of two factors: A) Three varieties: BRRI dhan29 (V1), BRRI dhan58 (V2), and Heera (V3). B) Four nitrogen sources: no nitrogen (T1), BRRI-recommended prilled urea (T2), recommended dose of mixed NPK (T3), and BARC-recommended USG (T4). The experiment was laid out in split plot design with three replications where main plot was for nitrogen source and subplot was for variety. USG treatment resulted in the highest grain production (8.6 t/ha) and the lowest percentage of spikelet sterility of any nitrogen source tested. Except for harvest index, all of the examined characteristics differed considerably between types. This is mostly due to BRRI dhan29 having the maximum number of full grains (98.8/panicale) and a significantly lower degree of spikelet sterility (7.3%). Among the interaction effects, the combination of the USG application with BRRI dhan29 showed the greatest performance in terms of delivering the maximum grain production (9.3 t/ha) by significantly reducing spikelet sterility. Res. Agric. Livest. Fish. Vol. 10, No. 2, August 2023: 175-182

Twice-split phosphorus application alleviates low-temperature impacts on wheat by improved spikelet development and setting

Extreme low-temperature incidents have become more frequent and severe as climate change intensifies. In Huang-Huai-Hai wheat growing area of China, the late spring coldness occurring at the jointing-booting stage (the anther interval stage) has resulted in significant yield losses of winter wheat. This study attempts to develop an economical, feasible, and efficient cultivation technique for improving the low-temperature (LT) resistance of wheat by exploring the effects of twice-split phosphorus application (TSPA) on wheat antioxidant characteristics and carbon and nitrogen metabolism physiology under LT treatment at the anther interval stage using Yannong 19 as the experimental material. The treatments consisted of traditional phosphorus application and TSPA, followed by a –4°C LT treatment and natural temperature (NT) control at the anther interval stage. Our analyses showed that, compared with the traditional application, the TSPA increased the net photosynthetic rate (Pn), stomatal conductance (Gs), and transpiration rate (Tr) of leaves and reduced the intercellular carbon dioxide concentration (Ci). The activity of carbon and nitrogen metabolism enzymes in the young wheat spikes was also increased by the TSPA, which promoted the accumulation of soluble sugar (SS), sucrose (SUC), soluble protein (SP), and proline (Pro) in young wheat spike and reduced the toxicity of malondialdehyde (MDA). Due to the improved organic nutrition for reproductive development, the young wheat spikes exhibited enhanced LT resistance, which reduced the sterile spikelet number (SSN) per spike by 11.8% and increased the spikelet setting rate (SSR) and final yield by 6.0 and 8.4%, respectively, compared to the traditional application. The positive effects of split phosphorus application became more pronounced when the LT treatment was prolonged.

Effect of Water Stress Duration on the Growth Characteristics and Yield Components of Upland Rice Varieties in Kenya

Drought stress is a major problem in upland rice grown areas under rainfed conditions. It affects plant growth and development, and eventually leads to a considerable yield reduction. The study was carried out with the aim of evaluating the effect of drought stress duration on the growth characteristics and yield components of upland rice varieties. The experiment was conducted at the University of Eldoret with Sixteen upland commercial and local rice varieties were used in the study obtained from Kenya and Liberia. Rice plants were subjected to drought stress treatments at tillering and flowering stages in the green house. The experiment was layout in a complete randomized design (CRD) in a split plot arrangement with five treatments and replicated three times. The results of leaf rolling, plant height, days to 50% flowering, days to maturity, panicle number, spikelet sterility, biological yield, leaf relative water content,1000-grain weight, harvest index and grain yield revealed that there were significant differences as a result of water stress on the treatments (p≤0.001) and rice varieties (p≤0.05). All the sixteen varieties were significantly affected by the treatments when compared with the control. The results also revealed that MWUR, Dourado, L-22, Komboka, Jaowo, LAC-23, Kpatawee, MWUR, White rice and Red Youmo varieties were significantly affected by the water stress treatments at leaf rolling, flowering and maturity then that of NERICA 1,2 ,3, 4, 10,11 and 14 at tillering and flowering stages. The findings of this study indicated that NERICA 1, 2, 3, 4, 10 varieties were less affected by soil water stress treatments amongst the tested varieties, followed by NERICA 11 and14 respectively. Thus, NERICA varieties had the best performance in most of the parameters that were measured. Therefore, these varieties can thus be used by breeders to develop varieties adapted to areas with limited rain fall and insufficient soil moisture for rice production.