Total Spikelet Research Articles

Increasing seedling number alleviates the adverse effects of warming on grain yield and reduces greenhouse gas emission in late-season rice

To address the adverse effects of warming on late-season rice, we investigated the impact of increasing the number of seedlings planted on rice yield, quality, and greenhouse gas emissions under canopy warming conditions using the free-air temperature increase (FATI) system. Three treatments were implemented: ambient temperature with 2 seedlings per hill (CKS1), canopy warming with 2 seedlings per hill (WS1), and canopy warming with 4 seedlings per hill (WS2). FATI increased rice canopy temperature and soil temperature by an average of 1.9oC–2.2oC and 0.6oC–0.8oC, respectively, over the two years. The yield in WS1 was significantly reduced by 10.1%–12.1% compared to CKS1, which was attributed to a significant decrease in total spikelets per unit area and spikelets per panicle, despite a notable increase in filled grains in 2023. However, WS2 demonstrated no significant change in yield compared with CKS1. Analysis of yield components revealed that WS2 exhibited significantly higher panicles per m2 relative to CKS1, while the spikelets per panicle were significantly lower than did CKS1. No significant changes were observed in grain weight and processing and appearance qualities. Compared with that under CKS1, CH4 was significantly reduced under WS2 treatment in both years. Furthermore, the global warming potential (GWP) and greenhouse gas intensity (GHGI) showed a decrease, with notable differences observed in 2022. Therefore, increasing the number of seedlings per hill can alleviate the negative impacts of canopy warming on grain yield and reduce greenhouse gas emissions in late-season rice.

Impact of supplemental irrigation and organic manure on growth and yield performance of rice variety BRRI dhan103 under terminal drought condition in Aman season

BRRI dhan103 is a transplanting Aman (T. Aman) rice variety that demands sufficient organic manure and supplemental irrigation to ensure successful production. Seven treatments, viz., T1= rainfed control; T2= one supplemental irrigation at 80 days after transplanting (DAT); T3= two supplemental irrigations at 70 and 80 DAT; T4= additional 5 t ha-1 poultry compost under rainfed condition; T5= additional 10 t ha-1 poultry compost under rainfed condition; T6= additional 2.5 t ha-1 biochar under rainfed condition; and T7= additional 5 t ha-1 biochar under rainfed condition, were evaluated against BRRI dhan103 to assess the impact of supplemental irrigation and manuring under terminal drought conditions. It was revealed that supplemental irrigation and manuring significantly improved all growth parameters and yield attributes compared to the rainfed control. Notably, T5 treatment provided its greatest performance statistically in respect of SPAD value (36.13), root dry weight (12.43 g), number of tillers hill-1 (13.22), panicle length (28.87 cm), panicles hill-1 at harvest (9.13), total spikelet (194.53), spikelet panicle-1 (197.63), filled spikelet panicle-1 (197.63), thousand grain weight (33.78 g), grain weight panicle-1 (28.70 g), grain yield hill-1 (31.97 g), and above-ground biological yield (3043.35 g m-2). The highest tiller hill-1 at harvest (9.53) was achieved when an additional 10 t ha-1 of poultry compost was applied under rainfed conditions. This study suggested that additional 10 t ha-1 poultry compost under rainfed conditions performed best to enhance the growth and yield of BRRI dhan103.

Identification and fine mapping of a QTL-rich region for yield-and quality-related traits on chromosome 4BS in common wheat (Triticum aestivum L.).

Yield and quality are important for plant breeding. To better understand the genetic basis underlying yield- and quality-related traits in wheat (Triticum aestivum L.), we conducted the quantitative trait locus (QTL) analysis using recombinant inbred lines (RILs) and a high-density genetic linkage map with a 90K array. In this study, a total of 117 QTLs were detected for spike number per area (SNPA), thousand grain weight (TGW), grain number per spike (GNS), plant height (PH), spike length (SL), total spikelet number (TSN), spikelet density (SD), grain protein content (GPC), and grain starch content (GSC). Among these QTLs, 30 environmentally stable QTLs for yield- and quality-related traits were detected. Notably, five QTL-rich regions (Qrr) for yield-and/or quality-related traits were identified, including the QTL-rich region on chromosome 4BS (QQrr.cau-4B) for eight traits (SNPA, GNS, PH, SL, TSN, SD, GPC, and GSC). The stable QTL-rich region QQrr.cau-4B was delimited into a physical interval of approximately 2.47Mb. Based on the annotation information of the Chinese spring wheat genome v1.0 and parental re-sequencing results, the interval included twelve genes with sequence variations. Taken together, these results contribute to further understanding of the genetic basis of SNPA, GNS, PH, SL, TSN, SD, GPC, and GSC, and fine mapping of QQrr.cau-4B will be beneficial for gene cloning and marker-assisted selection in the genetic improvement of wheat varieties.

A rare natural variation in TaFT-D2 underlies QTss.cas-3D associated with increased total spikelet number per spike in wheat

Total spikelet number per spike (TSS) is a crucial yield component in wheat. Dissecting and characterizing major stable quantitative trait loci (QTL) associated with TSS can significantly enhance the genetic improvement of yield potential. In a previous study, we identified a stable major QTL for TSS, named QTss.cas-3D. In the present study, we conducted fine mapping of QTss.cas-3D, interval to approximately 6.35 Mb, ranging from 105.03 to 111.38 Mb, based on the IWGSC RefSeq v2.1. Through genome re-sequencing and gene function annotation, we identified TraesCS3D03G0308000 (TaFT-D2) as the candidate gene. Phenotypic evaluation with paired near-isogenic lines revealed that this locus predominantly increases kernel number per spike by enhancing TSS and fertile spikelet number per spike, without significantly affecting thousand-kernel weight or tiller number. The presence of the TaFT-D2 allele in the parent P3228, which is rare in nature populations, highlights its potential value. This study provides a valuable gene resource and functional marker for wheat molecular breeding aimed at improving TSS and establishes a foundation for gene functional analysis of TaFT-D2.

Combination of Polymer-Coated Urea and Rapid-Release Urea Increases Grain Yield and Nitrogen Use Efficiency of Rice by Improving Root and Shoot Activities

The use of polymer-coated urea (PCU) can improve nitrogen use efficiency (NUE), compared to the application of rapid-release urea (RU). However, the effect of PCU-based nitrogen management on grain yield and the NUE of rice and its underlying mechanism remain unclear. A japonica rice cultivar Jinxiangyu 1 was grown in the field with four treatments including N omission (0N), split application of RU (Control), one-time application of 100% PCU (T1), and one-time application of 70% PCU + 30% RU (T2). Results showed that, compared to the control, the grain yield was significantly increased in the T2 treatment, while it was comparable in the T1 treatment. This was mainly due to increased total spikelets in the T2 treatment. Root oxidation activity (ROA) and root zeatin (Z) + zeatin riboside (ZR) content during booting were the distinct advantages of the T2 treatment, compared to either the control or T1 treatment, exhibiting significant or highly significant correlations with leaf photosynthesis. This process contributed significantly to total spikelets and total N uptake. Additionally, the T2 treatment absorbed more N than the control without reducing the internal N use efficiency (IEN), primarily due to its unchanged harvest index (HI) driven by comparable non-structural carbohydrate remobilization. In conclusion, combining PCU with RU can enhance the coordination of root and shoot traits during booting while maintaining a competitive HI at maturity, thereby significantly improving grain yield and achieving a balance in N uptake and utilization.

Genetic Variability for Yield Components, Iron and Zinc contents in Rice (Oryza sativa L.) Genotypes

The experiment was carried out for 11 characters in 41 rice genotypes during kharif 2022 at Agricultural Research Station, Vadgaon Maval, Pune. The highest value of GCV (32.111) and PCV (32.618) observed for grain yield per plant and followed by grain iron (Fe) content, GCV (31.137) and PCV (32.021), grain zinc (Zn) content GCV (27.039) and PCV (28.147), fertile spikelets per panicle GCV (20.462) and PCV (21.232), 1000 grain weight GCV (19.104) and PCV (20.094). The grain yield per plant was observed as the highest broad sense heritability (96.90%) followed by days to 50% flowering (95.60%) and grain iron (Fe) content (94.60%). The highest genetic advance as per cent of mean was observed for the traits grain yield per plant (65.121), grain iron content (62.373), grain zinc content (53.509) and fertile spikelets per panicle (40.625). The significant positive correlation was observed among grain yield per plant and days to 50% flowering (0.3171), panicle length (0.2974), fertile spikelets per panicle (0.5101), total spikelets per panicle (0.4519), spikelet fertility (0.4570), test weight (0.4378) and productive tillers per plant (0.5732). High heritability with high genetic advance observed for the trait grain yield per plant, grain iron (Fe) content, grain zinc (Zn) content, fertile spikelets per panicle and total spikelets per panicle indicated additive gene actions. The total spikelet per panicle (2.9940) was observed that had highest direct positive effect on grain yield per plant and followed by spikelet fertility % (0.7118), test weight (0.6805), productive tillers per plant (0.5068) and panicle length (0.1516).

Effects of Salt Stress on Physiological and Agronomic Traits of Rice Genotypes with Contrasting Salt Tolerance.

Salinity is one of the major constraints to crop production. Rice is a main staple food and is highly sensitive to salinity. This study aimed to elucidate the effects of salt stress on physiological and agronomic traits of rice genotypes with contrasting salt tolerance. Six contrasting rice genotypes (DJWJ, JFX, NSIC, HKN, XD2H and HHZ), including three salt-tolerant and three salt-sensitive rice genotypes, were grown under two different salt concentrations (0 and 100 mmol L-1 NaCl solution). The results showed that growth, physiological and yield-related traits of both salt-sensitive and salt-tolerant rice were significantly affected by salt stress. In general, plant height, tiller number, dry weight and relative growth rate showed 15.7%, 11.2%, 25.2% and 24.6% more reduction in salt-sensitive rice than in salt-tolerant rice, respectively. On the contrary, antioxidant enzyme activity (superoxide dismutase, peroxidase, catalase), osmotic adjustment substances (proline, soluble protein, malondialdehyde (MDA)) and Na+ content were significantly increased under salt stress, and the increase was far higher in salt-tolerant rice except for MDA. Furthermore, grain yield and yield components significantly decreased under salt stress. Overall, the salt-sensitive rice genotypes showed a 15.3% greater reduction in grain yield, 5.1% reduction in spikelets per panicle, 7.4% reduction in grain-filling percentage and 6.1% reduction in grain weight compared to salt-tolerant genotypes under salt stress. However, a modest gap showed a decline in panicles (22.2% vs. 22.8%) and total spikelets (45.4% vs. 42.1%) between salt-sensitive and salt-tolerant rice under salinity conditions. This study revealed that the yield advantage of salt-tolerant rice was partially caused by more biomass accumulation, growth rate, strong antioxidant capacity and osmotic adjustment ability under salt stress, which contributed to more spikelets per panicle, high grain-filling percentage and grain weight. The results of this study could be helpful in understanding the physiological mechanism of contrasting rice genotypes' responses to salt stress and to the breeding of salt-tolerant rice.

Shading at the Booting Stage Improved the Grain Quality of Hybrid Rice Due to Reduced Spikelet Production

As a growing abiotic stress, light deficient conditions seriously affect the yield and quality of rice. However, few studies focus on the effects of shading on grain quality at the booting stage and the responses of different hybrid rice cultivars to shading. Field experiments involving four representative rice (Oryza sativa L.) cultivars across no shading (CK) and 40% shading at the booting (S) and grain filling stages (SS) were conducted in 2021 and 2022. Compared with CK, S reduced grain yield by 53.0% but increased the head rice rate by 11.4% averaged across varieties and years. The chalkiness degree (CD) and chalky grain percentage (CR) were reduced by 73.0% and 61.6% in S due to its 45.3% lower total spikelets m–2, 44.0% lower grain–leaf ratio and 23.5% lower dry weight spikelet production efficiency, compared with CK. The CD and CR in SS were 49.5% and 41.0% higher and HR was 7.1% lower than that in CK. Shading significantly reduced amylose content, peak viscosity and breakdown value, but increased protein content and setback value, and the effects of SS were greater than S. Y-liangyou900 and Liangyoupeijiu showed better milling quality, while Y-liangyou900 and Chuanyou6203 obtained a better appearance and eating quality than the other varieties under both S and SS. In conclusion, shading at the booting stage significantly improved the milling, appearance and nutritional quality, and did not reduce the cooking and eating quality, but led to a significant decline in the grain yield of hybrid rice. Moreover, Y-liangyou900 exhibited better rice quality but lower yield under shading treatments. Therefore, more attention needs to be focused on screening shade-tolerant varieties using both yield and quality to cope with climate change in the future.

Effects of Salt Stress on Grain Quality and Starch Properties of High-Quality Rice Cultivars

In recent days, there has been a noticeable surge in demand for high-quality rice. However, the influences of salinity on the quality and starch properties of high-quality rice remain unclear. Three high-quality rice cultivars (Nanjing 9108, Nanjing 5055, and Nanjing 46) were studied to investigate the responses of grain quality to salt stress. There were three treatments, including a control zero salt level (0 g·kg−1, CK), and two salt levels of 0.1 g·kg−1 (0.1% salt stress, T1) and 0.2 g·kg−1 (0.2% salt stress, T2). The study involved the assessment of the appearance, milling, cooking, and eating qualities of rice. We also conducted an analysis of pasting properties, an evaluation of starch thermal properties, and an examination of the fine structure of amylopectin. The findings suggest that as the level of salt stress increases, the yield of rice gradually declines, which is primarily due to a significant reduction in the total spikelet number and the ratio of filled grains. Compared with CK treatment, the appearance and milling quality of rice were significantly improved within the T1 treatment. In addition, the protein concentration and amylose concentration were significantly decreased, the gel consistency was significantly increased, and the cooking and eating qualities were improved. In terms of starch properties, the peak viscosity, breakdown value, infrared ratio (1022/995), and short-chain-length amylopectin ratio increased significantly, while the setback value, pasting temperature, gelatinization enthalpy, relative crystallinity, and infrared ratio (1045/1022) decreased significantly. When comparing T2 with CK, the appearance quality and cooking and eating quality had deteriorated, and the milling quality was improved. The changes in the structural and physicochemical properties of starch were opposite to those in the comparison between the T1 treatment and the CK group. Accordingly, we propose that moderate salt stress has the potential to enhance rice quality, even though there may be a slight decrease in yield. This indicates that it is feasible to cultivate high-quality rice in saline–alkali beach areas.

Soil biological quality in rhizosphere, growth, and yield of upland rice grown on acid soil after amended biochar enriched sap of Kappaphycus alvarezii

Abstract. Rakian TC, Kilowasid LMH, Afa LO, Riskyana A, Nurazizah, Wijayanti Y, Bahrun A, Subair I, Rahni NM, Alam S, Sarawa, Karimuna L. 2023. Soil biological quality in rhizosphere, growth, and yield of upland rice grown on acid soil after amended biochar enriched sap of Kappaphycus alvarezii. Biodiversitas 24: 6780-6792. Biological soil quality is essential in evaluating soil management practices using biochar enriched for upland rice growth on acid soil. Therefore, the study aimed to (i) analyze the effect of biochar-enriched sap of Kappaphycus alvarezii (K-sap) on the abundance of Arbuscular Mycorrhizae Fungi (AMF), bacteria, and protozoa in rhizosphere soil, growth, and yield of upland rice, and (ii) the relationship between the abundance of soil biota and the growth and yield components, as well as straw N, P, and K content on acid soil. Four upland rice were grown on acid soil incubated with biochar-enriched sap for two weeks in pots. Nine treatments of the biochar-enriched sap were tested, namely control, 5% biochar-0% K-sap, 5% biochar-5% K-sap, 5% biochar -10% K-sap, 5% biochar-15% K-sap, 7.5% biochar-0% K-sap, 7.5% biochar-5% K-sap, 7.5% biochar-10% K-sap, and 7.5% biochar-15% K-sap. Each treatment was three replicates in a randomized block design. The results demonstrated that the AMF spores quantity decreased while flagellates increased in the soil rhizosphere. The P and K content increased, the N:P decreased, and P:K ratio varied in the straw of the upland rice. Plant height and total spikelets increased, while root dry weight and roots to shoots ratio (R:S) decreased with biochar enriched. The abundance of AMF spores and flagellates correlated positively and negatively with R:S. Furthermore, R:S was negatively correlated with plant height and total spikelets. Plant height and total spikelets showed a positive correlation, while root dry weight and R:S was negatively correlated with K content in shoot tissue. The P and K contents with N:P ratio and N:P with P:K were negatively correlated. In conclusion, biochar-enriched K-sap effectively regulated the activity and composition of soil biota in the rhizosphere, influencing upland rice's growth, yield, and nutrient balance uptake on acid soils.

Optimizing the Total Spikelets Increased Grain Yield in Rice

Maximizing rice yield potential has always been the focus of high-yield rice cultivation research. For high-yield rice cultivation and breeding, more research into the link between yield and yield components is essential. In this experiment, 38 rice varieties with different yield types and 185 rice varieties as materials were chosen. The relationships between yield and yield components were studied. The regulation effects of total nitrogen application rate (TNAR) on yield and yield components were observed. The results showed that (1) the grain yield of high-yield varieties was 189.3−195.6%, 76.1−77.7%, and 27.0−28.7% higher than that of super-low-yield, low-yield, and medium-yield varieties, respectively. Compared with rice varieties with other yield types, rice varieties with high-yield type have a higher total number of spikelets. (2) The spikelet number per panicle and total number of spikelets were significantly positively linked with grain yield, but significantly negatively correlated with filled grains and grain weight. (3) With an increase in TNAR (0−340 kg ha−1), the panicles, spikelet number per panicle, and total spikelets of rice varieties with different yield types increased gradually, and the filled grains and grain weight decreased gradually. The higher the TNAR, the more obvious the decrease in filled grains and grain weight. The grain yield of rice varieties with different yield types was the highest under the TNAR at 250 kg ha−1. The main factor contributing to its high yield was the substantial increase in total spikelets. The above results showed that increasing the spikelet number per panicle and total spikelets played a material role in improving rice yield.

Enhancing Transplant Aman Rice Productivity through NPK Fertilizer Split Application Scheduling Under Zero Till Non-Puddled Condition

This experiment was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh to evaluate the varietal response of split application of NPK fertilizer application schedule on transplant aman rice under zero till non-puddled condition. The experiment comprised three rice varieties viz. Bashiraj (local), BRRI dhan49 (inbred), Dhanigold (hybrid); and seven NPK fertilizer application schedules. The experiment was laid out in a randomized complete block design with three replications. The effect of variety, NPK fertilizer split application schedule and their interaction showed significant variation on the yield attributes and yield of aman rice. In interaction, the highest number of effective tillers hill-1 (11.66), total spikelets panicle-1 (164.00), grains panicle-1 (151.22), 1000-grain weight (38.70 g), grain yield (5.67 t ha-1) and harvest index (60.36%) were obtained from hybrid variety Dhanigold when fertilized following 3-splits of N [1/3 at 14 days after transplanting (DAT) + 1/3 at maximum tillering (MT)+ 1/3 at panicle initiation (PI)] and P (1/3 as basal + 1/3 at MT + 1/3 at PI ), and single split of K as basal (full dose). Same treatment combination also provides the highest yield of BRRI dhan49, but the local Bashiraj gave the highest yield at recommended practice where only N was top-dressed at 3 splits. Based on this result, it may be concluded that for better productivity hybrid Dhanigold and inbred BRRI dhan49 might be fertilized with 3-splits of N (1/3 at 14 DAT + 1/3 at MT + 1/3 at PI) and P (1/3 as basal + 1/3 at MT + 1/3 at PI) and full dose of K as basal during aman season under zero till non-puddled condition. On the other hand, for local variety Bashiraj 3-spilts of N either [½ as basal + ¼ at active tillering (AT) + ¼ at PI] or N (1/3 at 7 DAT + 1/3 at MT + 1/3 at PI) and P, K as single split as basal appeared as the best application schedule.

Genetic Studies for Selected Agronomic Traits in 19 Maintainer Genotypes of Rice (Oryza sativa L.)

The current study was performed at MARDI Seberang Perai, Penang, Malaysia, during the Off Season 2020. This study aims to analyze genetic parameters, correlation, and path coefficient for 11 agronomic traits in 19 maintainer rice genotypes. All experimental units were arranged in a randomized complete block design with three replications. Observations were recorded for days to 50% flowering, plant height, culm height, panicle length, total panicle per plant, total spikelet per panicle, spikelet fertility, thousand-grain weight, grain length, grain width, and grain yield per plant. Analysis of variance revealed significant differences in the genotype factor for all assessed traits. The total spikelet per panicle trait exhibited the highest phenotypic and genotypic variance. Moreover, this trait had high broad-sense heritability and high genetic advance as percent of mean. Total panicle per plant recorded the highest value of phenotypic and genotypic coefficient of variation among traits under study and were classified as high and moderate, respectively. The traits association study revealed a significant positive correlation between grain yield per plant and two traits: total panicle per plant and spikelet fertility. Path analysis revealed a very high direct effect of plant height, culm height, and panicle length on grain yield per plant. This study contributes essential knowledge for the strategic design of effective breeding programs.

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.

Fine mapping and characterization of a major QTL for grain length, QGl.cau-2D.1, that has pleiotropic effects in synthetic allohexaploid wheat

Grain size is one of the determinants of grain yield, and identifying the genetic loci that control grain size will be helpful for increasing grain yield. In our previous study, a quantitative trait locus (QTL) for grain length (GL), QGl.cau-2D.1, was identified from an F2 population developed from the cross between the natural (TAA10) and synthetic (XX329) allohexaploid wheat. In the present study, we mainly fine mapped and validated its genetic effects. To this end, multiple near-isogenic lines (NILs) were obtained through marker-assisted selection with TAA10 as the recurrent parent. The secondary populations derived from 25 heterozygous recombinants were used for fine mapping of QGl.cau-2D.1, and the allele from XX329 significantly increased GL, thousand-grain weight (TGW), total spikelet number per spike (TSN) and spike compactness (SC). Using NILs for XX329 (2D+) and TAA10 (2D−), we determined the genetic and pleiotropic effects of QGl.cau-2D.1. The target sequences were aligned with the wheat reference genome RefSeq v2.1 and spanned an ~0.9 Mb genomic region. TraesCS2D03G0114900 (ortholog of Os03g0594700) was predicted as the candidate gene based on whole-genome re-sequencing and expression analyses. In summary, the map-based cloning of QGl.cau-2D.1 will be useful for improving grain weight with enhanced GL and TSN.

Effect of Biochar on Arbuscular Mycorrhizae Fungi, Nutrient Uptake and Growth of Local Upland Rice, Southeast Sulawesi, Indonesia

Biochar has the capacity to influence soil fertility, mycorrhizal arbuscular fungi (AMF), and upland rice growth. Therefore, this study aimed to assess biochar addition on soil character and investigate the effect on AMF, growth, yield, and nutrient uptake of upland rice local. Four levels biochar rate (%, w/w) of 0%, 2.5%, 5.0%, and 7.5% was tested in a pot experiment. The results showed that pH, C-org, tot-N, and C and N-ratio increased linearly, while P-available quadratic, and K-exchange increased exponentially with biochar rate. At 60 and 90 days after planting, the height of a plant containing 7.5% biochar was significantly high. The roots and shoots ratio showed the highest and lowest values at 0% and 7.5% biochar rates. Furthermore, the filled spikelet percentage at a 5.0% was the most significant among the others. The biochar rate increased the straw P and K uptake, but N was insignificant and N and P ratio was decreased. Total AMF spores were reduced with biochar addition, and the difference in the proportion of infected roots was not statistically significant. There was a positive correlation between total spikelet per panicle with P and K uptake and a negative correlation with N and P ratio and total AMF spore. The filled spikelet negatively correlated with K uptake, and biochar addition to soil fertility increased. The 5% addition had a better effect on yield component and nutrient uptake of P and K by the local upland rice on acidic soil.

Principal component and cluster analyses for assessing agro-morphological diversity in rice

Forty-five rice genotypes were evaluated for determining the pattern of variation and relationship among 14 yield contributing traits. Four principal components (PCs) exhibited eigen values >1.0 and explained about 79.5 % of the total phenotypic variability. From rotated component matrix it has been observed that the highest positive eigen vector was taken by secondary branches (0.945), followed by total spikelet number (0.945), fertile spikelet number (0.889), primary branches (0.676) and harvest index (0.632) in PC1, indicating the major effects in the overall variation among the genotypes. Seven groups were formed after cluster analysis. Cluster I had lowest average for days to 50% flowering, Cluster II had highest mean value for harvest index, Cluster III had highest mean for flag leaf area, test weight, and straw and grain yield per plant, and Cluster V had highest mean value for primary branches, total spikelet number, fertile spikelet number and fertility %. So, desirable genotypes fromdifferent cluster can be selected and hybridization programme may be initiated to utilize heterosis in F1 generation and wide spectrum of recombinants in segregating generations for selection of promising segregants.

Identification of major QTLs for yield-related traits with improved genetic map in wheat.

Identification of stable major quantitative trait loci (QTLs) for yield-related traits is important for yield potential improvement in wheat breeding. In the present study, we genotyped a recombinant inbred line (RIL) population using the Wheat 660K SNP array and constructed a high-density genetic map. The genetic map showed high collinearity with the wheat genome assembly. Fourteen yield-related traits were evaluated in six environments for QTL analysis. A total of 12 environmentally stable QTLs were identified in at least three environments, explaining up to 34.7% of the phenotypic variation. Of these, QTkw-1B.2 for thousand kernel weight (TKW), QPh-2D.1 (QSl-2D.2/QScn-2D.1) for plant height (PH), spike length (SL) and spikelet compactness (SCN), QPh-4B.1 for PH, and QTss-7A.3 for total spikelet number per spike (TSS) were detected in at least five environments. A set of Kompetitive Allele Specific PCR (KASP) markers were converted based on the above QTLs and used to genotype a diversity panel comprising of 190 wheat accessions across four growing seasons. QPh-2D.1 (QSl-2D.2/QScn-2D.1), QPh-4B.1 and QTss-7A.3 were successfully validated. Compared with previous studies, QTkw-1B.2 and QPh-4B.1 should be novel QTLs. These results provided a solid foundation for further positional cloning and marker-assisted selection of the targeted QTLs in wheat breeding programs.

Mitigating Ammonia Volatilization without Compromising Yield and Quality of Rice through the Application of Controlled-Release, Phosphorus-Blended Fertilizers

Ammonia (NH3) volatilization from paddy fields is a major issue which leads to poor fertilizer use efficiency and is considered a severe threat to the atmosphere. The previous research studies gave importance to the use of nitrogen fertilizers to mitigate NH3 volatilization, while very little emphasis was given to the role of other fertilizers, such as phosphorus (P), for the alleviation of NH3 volatilization in rice fields. Considering P importance herein, we conducted two consecutive field experiments using an innovative, controlled-release, phosphorus-blended fertilizer (CRPBF, with levels CRP0, CRP1, and CRP2). We compared CP0 (in which no fertilizer was applied), CP1 (112.5 kg P ha−1 P of locally recommended fertilizers), and CP2: (P and K blended fertilizers) to determine the best possible way to reduce NH3 volatilization without affecting the yield and quality of rice. The results of the study suggested that the yield of rice increased significantly with the application of CRP1 (11.11 t ha−1) and CRP2 (11.99 t ha−1). The addition of CRP1 and CRP2 to the rice field also enhanced yield-related components, i.e., panicle weight, total spikelets per unit area, spikelets per panicle, and above-ground biomass. CRP0 showed a lower yield and related components when compared to CP2. The addition of CRP1 and CRP2 demonstrated lower protein contents when compared to other treatments. The CRPBF application improved starch content and taste scores, and reduced the chalkiness of the rice grain during both years. The results showed a decreasing trend in NH3 volatilization from CRPBF amendments by improving the nitrogen use efficiency traits when compared to other treatments: CRP2, CRP1, and CRP0 reduced NH3 volatilization by 45%, 35%, and 15%, respectively. The results of this study indicate that, due to the episodic nature of NH3 volatilization, CRPBFs with 50% P and 100% P can markedly reduce NH3 volatilization from paddy fields without compromising the yield and quality of the crop, and could be a promising alternative to the ordinary commercial fertilizers used in rice fields.

GENETIC DIVERSITY IN TRADITIONAL LOCAL CULTIVAR OF JHUM RICE GENOTYPES OF BANGLADESH

The genetic diversity of seventeen indigenous jhum rice accessions collected from the BRRI gene bank was studied through Mahalanobis D2-statistics for grain yield and its contributing characters. The genotypes were grouped into three clusters. Cluster III contained the highest number of genotypes (10), while clusters I and II contained five and two genotypes, respectively. The highest inter-cluster distance was observed between clusters II and III (14.408) and the lowest between clusters I and II(5.9). Genotypes of cluster III showed high genetic distances from all other clusters in terms of inter-cluster distance. The highest cluster means for number of effective tillers (11.34), longest panicle (25.41 cm), high panicle weight (3.45 g), grain per panicle, total spikelets per panicle, and grain yield were obtained from cluster II, whereas the lowest mean values for yield, plant height and grain breadth were found in cluster III. Cluster I contained the genotypes producing comparatively taller and earl maturing genotypes. Therefore, genotypes under cluster III and cluster I have enough potentiality to be used for backcrossing or as parents in a breeding program to produce desired recombinants with early maturity and high yield specific to jhum cultivating areas in Bangladesh.