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Background: An investigation was performed to identify epistasis, additive, dominance components of genetic variation and yield and yield variability attributing characteristics by triple test cross testing involving three testers (P1, P2 and F1) and ten rice lines. Methods: The study materials consisted of F1 seeds of three crosses, involving six parents namely, ASD16, ADT47, ASD18, CO51, TKM9 and MTU 7029. They are evaluated in randomized complete block design with three replications. Observations were reported for seven traits, namely plant height, number of tillers per plant, number of productive tillers per plant, length of panicle, number of grains per panicle, weight of 1000 grains and yield of grain per plant on five randomly selected plants per replication. Result: The segregating population of three crosses exhibited wide range of variability for most of the traits. The difference between GCV and PCV was low for most of the characters indicated less influence of environment. Among the three crosses ASD18 X CO15 recorded high percent of heritability and genetic advance for grain yield per plant. The estimate of total epistasis revealed that i type of epistasis (additive X additive) was highly significant for number of tillers per plant, number of productive tillers per plant, panicle length and 1000 grain weight. The effect of the additive (D) variance was very important for all the traits except the number of grains per panicle. Across all traits, the degree of dominance (H/D)1/2 was less than unity (< 1) suggesting, partial of dominance. Since, the pre dominance component of epistasis in autogamous crop is additive X additive (i type), it was suggested that the selection may be post ponded to later generation until all the non-additive components of variance has been mitigated to additive components. [ABSTRACT FROM AUTHOR]

The aim of this experiment is to evaluate the impact of chitosan-NPK slow-release fertilizer (CS-NPK SRF) on the germination and growth of silk tree and rice in different planting patterns, as well as to assess the nutrient release rate of the SRF. The germination test followed a complete randomized design, incorporating a single factor (fertilizer type), namely no fertilizer (F0), SRF CS 0.5% weight 0.03 g (F1), SRF CS 0.5% 0.01 g (F2), SRF CS 0.7% 0.03 g (F3), SRF CS 0.7% 0.01 g (F4), and conventional NPK fertilizer (F5). The growth test utilized a 2-factor split-plot design, with the primary factor being the planting pattern (sengon/rice monoculture-SM/RM and sengon-rice agroforestry-AF) and the second factor being the fertilizer type. Results indicate that F2 and F4 yielded the highest germination and growth values in both plants, although not significantly different from F0. These findings suggest that CS-NPK SRF has the potential to enhance plant growth. The AF pattern exhibited lower growth compared to SM/RM, attributed to plant competition. CS-NPK SRF demonstrated a slower nutrient release (47.65% N; 85.01% P; 31.80% K) compared to conventional fertilizers. This slow release could potentially reduce nutrient loss to the environment while enhancing plant nutrient absorption. [ABSTRACT FROM AUTHOR]

Rice (Oryza sativa L.), a semi-aquatic crop cultivated in diverse environments from sea coasts to high altitudes, faces submergence issues impacting one-third of global cultivation. Effectively choosing superior offspring with a range of genetic traits is vital for improving yield stability, particularly in the development of submergence-tolerant varieties. This is accomplished by comprehending gene action through the generation mean analysis. This experimental material comprised six generations (P1, P2, F1, F2, B1, and B2) obtained from two rice crosses viz., ADT 45 x APD 19002 and CO 54 x APD 19002 involving three parents, examining twelve traits. In the cross ADT 45 x APD 19002, traits like days to fifty per cent flowering, plant height, number of productive tillers per plant, flag leaf width, total number of grains per panicle, number of filled grains per panicle, and single plant yield exhibited opposite signs of dominance (h) and dominance x dominance (l), indicating a prevalence of duplicate epistasis. Simultaneously, additive(d) and additive x additive(i) gene effects were displayed by days to fifty per cent flowering, total number of tillers per plant, panicle length, flag leaf width, total number of grains per panicle, and single plant yield. In cross CO 54 x APD 19002, traits such as days to fifty per cent flowering, plant height, flag leaf width, number of filled grains per panicle, spikelet fertility, and single plant yield suggested predominance of duplicate epistasis. Meanwhile, additive and additive x additive gene effects predominantly influenced the days to fifty per cent flowering, spikelet fertility, and single plant yield. These findings propose the potential for improvement through later-generation selection, emphasizing the integration of selection with screening for submergence tolerance to develop high-yielding submergence-tolerant varieties. [ABSTRACT FROM AUTHOR]

Bacterial panicle blight (BPB), incited by Burkholderia glumae, has impacted rice production globally. Despite its significance, little is known about the disease and the virulence pattern of the causal agent. BPB is a major challenge in the rice‐growing belts of North‐western India. We have characterized the 21 BG strains using the 16S rRNA and the gyrB gene‐based sequence approach in the present study. The gyrB gene‐based phylogenetic analysis resulted in geographic region‐specific clustering of the BG isolates into three clades. The BG isolates from Delhi‐National Capital Region (Delhi NCR) (Clade 1) and Uttar Pradesh (UP) (Clade 2) were separated into two clades and the BG isolates from Uttarakhand and Haryana clustered together in a single clade (Clade 3). Likewise, we sequenced the eight major virulence‐associated genes viz., toxA, toxB, lipA, lipB, pehA, pehB, flhC and flhD present across the genome of B. glumae and identified their interacting proteins through STRING analysis. Furthermore, virulence screening of 21 BG strains revealed the variation in the percentage of grains infected and the yield of rice plants. The most virulent BG1 strain resulted in the highest disease incidence (82.11%) and lowest yield (11.12 g/plant) and BG10 came out as the least virulent strain. Besides, the inoculation at three stages of the plant revealed that the booting stage of rice is the most susceptible stage which resulted in maximum disease percentage and less yield. Overall, our study gives information about virulence‐associated gene characterization and variation in the virulence nature of Indian BG strains. [ABSTRACT FROM AUTHOR]

The advancement of hybrid technology plays a crucial role in addressing yield plateau and diminishing resources in rice cultivating regions. The knowledge of genetic diversity among parental lines is a prerequisite for effective hybrid breeding program. In the current study, a set of 66 parental lines was studied for diversity based on both morphological characters and microsatellite SSR markers. The genetic variability parameters unveiled that number of productive tillers per plant, single plant yield and hundred grain weight exhibited additive gene action. Mahalanobis D2 statistics grouped the genotypes into ten clusters based on yield and grain traits. The principal component analysis identified four PCs with eigen value more than one accounting for 71.28% of cumulative variance. The polymorphic SSR markers produced 122 alleles among which the marker RM474 recorded the highest values for Polymorphic Information Content (0.83) and heterozygosity index (0.85). The genotypes were assembled in seven clusters based on jaccard distances using the Unweighted Pair Group method with Arithmetic Mean (UPGMA). The population structure divided the entire population into 3 subpopulations. In both clustering, there was difference in the assembling of genotypes, but, good performing genotypes identified through PCA were positioned in different clusters in both approaches. The genotypes CBSN 495 and CBSN 494 located in different clusters were identified as the potential restorers for high yielding and short duration hybrids. The hybridization among CRR Dhan 310, CRR Dhan 315, IR64 DRT, CB 17135 and WGL 347 can be performed to develop climate smart varieties with improved nutrition. [ABSTRACT FROM AUTHOR]

Root‐knot nematodes, Meloidogyne spp., are considered one of the major biotic constraints for global rice production. Although the role of Meloidogyne graminicola in root‐knot disease progression is well investigated, negligible research has been performed to understand the damaging potential of M. incognita in rice. In this study, the comparative infection biology of M. incognita and M. graminicola was investigated in the basmati rice cultivar PB1121 growing in Pluronic gel medium and soil. Intriguingly, M. incognita laid eggs outside the galled root, whereas M. graminicola egg masses were deposited inside the galled root. This differential egg‐laying pattern can be correlated with their specific adaptations in irrigated and upland rice production systems. Although M. incognita induced a greater number of galls than M. graminicola, M. graminicola gall sizes were comparatively larger than those of M. incognita. The greater reproductive success of M. graminicola than M. incognita did not cause any difference in their yield reduction potential in PB1121. PB1121 was equally vulnerable to M. incognita and M. graminicola in terms of reduction in plant height, tiller numbers per plant and grain yield per plant. Our research suggests that M. incognita also causes economic damage to rice, and nematode management tactics must consider the damaging potential of both nematode species. [ABSTRACT FROM AUTHOR]

Haplotype-based breeding is an emerging and innovative concept that enables the development of designer crop varieties by exploiting and exploring superior alleles/haplotypes among target genes to create new traits in breeding programs. In this regard, whole-genome re-sequencing of 399 genotypes (landraces and breeding lines) from the 3000 rice genomes panel (3K-RG) is mined to identify the superior haplotypes for 95 drought-responsive candidate genes. Candidate gene-based association analysis reveals 69 marker-trait associations (MTAs) in 16 genes for single plant yield (SPY) under drought stress. Haplo-pheno analysis of these 16 genes identifies superior haplotypes for seven genes associated with the higher SPY under drought stress. Our study reveals that the performance of lines possessing superior haplotypes is significantly higher (p ≤ 0.05) as measured by single plant yield (SPY), for the OsGSK1-H4, OsDSR2-H3, OsDIL1-H22, OsDREB1C-H3, ASR3-H88, DSM3-H4 and ZFP182-H4 genes as compared to lines without the superior haplotypes. The validation results indicate that a superior haplotype for the DREB transcription factor (OsDREB1C) is present in all the drought-tolerant rice varieties, while it was notably absent in all susceptible varieties. These lines carrying the superior haplotypes can be used as potential donors in haplotype-based breeding to develop high-yielding drought-tolerant rice varieties. Using a subset of 399 genotypes from the 3000 rice genomes panel, genotypes carrying superior haplotypes were identified for five genes associated with yield under drought stress that hold potential for the development of high-yield drought-tolerant varieties in rice. [ABSTRACT FROM AUTHOR]

The grain protein content is an important quality trait in cereals, and the expression level of the OsAAP6 can significantly affect the grain protein content in rice. Through site-directed mutagenesis, we found that the position from −7 to −12 bp upstream of the transcription start site of the OsAAP6 was the functional variation site. By using the yeast single hybrid test, point-to-point in yeast, and the local surface plasmon resonance test, the OsNAC74 was screened and verified to be a regulator upstream of OsAAP6. The OsNAC74 is a constitutively expressed gene whose product is located on the cell membrane. The OsAAP6 and the genes related to the seed storage in the Osnac74 mutants were downregulated, and grain protein content was significantly reduced. In addition, OsNAC74 had a significant impact on quality traits such as grain chalkiness and gel consistency in rice. Although the Osnac74 mutant seeds were relatively small, the individual plant yield was not decreased. Therefore, OsNAC74 is an important regulatory factor with multiple biological functions. This study provides important information for the later use of OsNAC74 gene for molecular design and breeding in rice. [ABSTRACT FROM AUTHOR]

Saline stress is a major abiotic stress that inhibits plant growth and yields worldwide. The plant transcription factor (TF) family plays an important role in converting abiotic stress signals into gene expression changes. In this study, a transcriptome-based comparative analysis was performed to investigate the global gene expression of all the TFs in diploid and autotetraploid rice during the early stage of NaCl stress and recovery period. The phenotypic data indicated that the tetraploid rice exhibited a superior salt-tolerant ability compared to the diploid rice. A total of 55 TF families were co-expressed in the tetraploid and diploid rice, and the cumulative number of TF-expressed genes was relatively higher in the diploid rice than in the tetraploid rice at all time points. Unlike the diploid rice, the overall gene expression levels of the tetraploid rice were comparable to the control during recovery. The number of differentially expressed TFs (DE-TFs) in the tetraploid rice decreased after recovery, whereas it increased to a large extent in the diploid rice. GO and KEGG pathway enrichment analysis of the DE-TFs discovered the early switching of the ABA-activated signaling pathway and specific circadian rhythm in the tetraploid rice. Combining the PPI network and heatmap analysis, some core DE-TFs were found that may have potential roles to play in tetraploid salt tolerance. This study will pave the way for elucidating the complex network regulatory mechanisms of salt tolerance in tetraploid rice. [ABSTRACT FROM AUTHOR]

Tropospheric ozone, a toxic air pollutant and strong greenhouse gas, is possibly the most damaging air pollutant to agricultural crops due to its phytotoxicity and prevalence at high concentrations in agricultural areas. Being a strong oxidizing gas, once ozone enters the plant via the stomata it can cause damage to foliage which subsequently affects plant growth. This chapter provides an overview on ozone air quality, ozone effects on plant and crop, and the experimental and modeling methods used to assess the effects. A focus was on the results of the experimental and modeling studies of the ozone effects on agricultural crops in Asia. Detailed description is provided for the experiments using open top chamber method conducted for popular cultivars of rice (R18, Oryza sativa L.) and peanut (L14, Arachis hypogaea L). For each crop, five treatments were used, including one control and four treatments with fumigation ozone concentrations ranging from 32 to 113 ppb. Ozone effects have been clearly seen through visible leave injuries, reduction in plant height and dry biomass, and finally the crop yield loss. The rice grain and straw yields reduced by about 4.5% and 3.7% by every 10-ppb increase in O3 exposure level, respectively. The corresponding reduction for peanut seed and above ground biomass yields was, respectively, 4.5% and 2.1%. Multiple effects of ozone on plant, agricultural crop, as well as human health and climate make it a priority pollutant for control. Use of alternative ozone resistant cultivars of plants and crops should also be considered along, especially in areas with future high ozone scenarios. [ABSTRACT FROM AUTHOR]

The challenging climatic conditions and scarcity of water availability have a significant impact on rice production in South Asia. Presently, rice is grown by the conventional transplanting method, which is associated with several problems like deterioration of soil health, labor scarcity and lowering of the water table. The current scenario demands some substitutive planting methods and the development of rice varieties that require less water and favor mechanization. Therefore, field experiments were carried out for two consecutive seasons to examine the responses of fifteen rice varieties under wet direct seeding (WDS), flooded transplanted rice (FTR) and the system of rice intensification (SRI) for grain yield, component variables and quality traits. The examined varieties showed a significant variation for all the studied variables among the three planting methods. WDS recorded a reduced mean value for tillers per plant, panicle length, panicle weight, spikelets per panicle, thousand grain weight, biological yield per plant and grain yield per plant by 26.76%, 7.48%, 12.72%, 16.07%, 3.20%, 3.79%, 15.13% and 25.03%, respectively, While, SRI showed an increased mean for tillers per plant, panicle length, panicle weight, spikelets per panicle, thousand grain weight, biological yield per plant and grain yield per plant by 19.02%, 1.01%, 8.33%, 8.38%, 1.37%, 13.60% and 16.23% compared to FTR. Among the varieties, CSR 30 showed minimum reduction under WDS, whereas Pusa Basmati 1121 recorded maximum increment under SRI for tillers per plant, panicle length, panicle weight, spikelets per panicle, thousand grain weight, biological yield per plant and grain yield per plant compared to FTR. Further stepwise regression identified tillers per plant, biological yield per plant, panicle length, days to maturity, thousand grain weight in WDS and tillers per plant, biological yield per plant, days to maturity and thousand grain weight in SRI contributed most to grain yield variation and needed to be focused greatly for yield enhancement in respective planting methods. [ABSTRACT FROM AUTHOR]

The aim of the present study was to assess the degree of genetic variation, heritability, and character relationship among yield, yield attributing and grain quality parameters in BC3 F2 of CO 52 x APD19002 population. In the current study, number of total tillers per plant, number of productive tillers per plant, flag leaf length, number of filled grains per panicle and single plant yield showed high PCV and GCV. It became evident that there exists a highly significant and positive association between single plant yield and number of productive tillers per plant followed by number of tillers, flag leaf length, plant height, spikelet fertility and test weight. The path coefficient analysis showed that number of productive tillers per plant had high positive direct effect on single plant yield followed by flag leaf length, kernel length, KBAC and LER. The results indicate the number of productive tillers per plant and flag leaf length were identified as the key contributing traits as they are highly heritable and simultaneous consideration of these traits is important for crop improvement. It implies that flag leaf provides more photosynthates to grains along with number of productive tillers per plant which in turn increases the grain yield. [ABSTRACT FROM AUTHOR]

The present study aims to evaluate the genetic variability, character association and path coefficient for various quantitative traits in fifty rice genotypes comprising of landraces and varieties under water limited conditions. Drought being a major abiotic stress causes severe reduction in grain yield especially during reproductive stages. The results revealed the presence of high genetic variability and significance for all the traits studied. The traits like single plant yield, number of filled spikelets per panicle, number of productive tillers per plant, flag leaf length, leaf rolling and leaf drying showed high variability compared to all other traits. The traits viz., spikelet fertility, number of productive tillers per plant, number of total tillers per plant, plant height, flag leaf breadth, panicle length, number of filled spikelets per panicle and relative water content exhibited a significant and positive correlation and direct effect on single plant yield, suggesting the potential importance of these traits in the improvement and selection of stable and high-yielding rice genotypes. [ABSTRACT FROM AUTHOR]

Drought is an important factor limiting rice productivity in rainfed ecosystem. Development of high yielding drought tolerant rice varieties would increase rice production under such condition. In the present study, 116 qDTY QTL introgressed back crossed inbred lines (BILs) derived from the crosses viz., ADT (R) 45 * 3/Apo, ADT (R) 45 * 3/ Way Rarem and ADT (R) 45 * 2/Apo // ADT (R) 45 * 2/ Way Rarem along with parents were evaluated to assess their performance under target production environment. Estimates on genetic variability, trait association, direct and indirect effects of yield and yield components and principal component analysis were worked out. The results of genetic variability showed wide variation among the genotypes for different traits. High values of PCV than GCV showed the influence of environment on the traits. Genotypes could be selected based on total number of tillers per plant, number of productive tillers per plant, spikelet fertility, single plant yield, 1000 seed weight and grain yield per plot, which were found to have high heritability and genetic advance. Correlation analysis exhibited high and significant positive correlation of grain yield per plot with single plant yield and non significant positive association of all the traits except plant height that was negatively correlated. Path coefficient analysis of the genotypes showed that total number of tillers per plant had maximum direct effect on grain yield, while number of productive tillers per plant had high indirect effect on grain yield via total number of tillers. Based on genetic variability, correlation and path analysis, selection for six traits, viz., total number of tillers per plant, number of productive tillers per plant, single plant yield, spikelet fertility, 1000 seed weight and grain yield per plot, would be rewarding. The results of principal component analysis revealed that, four out of eleven principal components viz., PC1, PC2, PC3 and PC4 contributed 72.62% of the total variation with eigen values more than 1. PC1 accounted for the highest variability with 24.66% followed by PC2 (20.42%), PC3 (16.19%) and PC4 (11.35%). From this study, the traits contributing for variation were identified and the resulting genotypes would be beneficial for improving yield with drought tolerance. [ABSTRACT FROM AUTHOR]

The present experiment was undertaken to study the variability, trait association and principle component analysis among eighteen characters in 53 rice genotypes including landraces and cultivars. Higher estimates of GCV and PCV coupled with high heritability and GAM were observed for a number of filled grains per panicle followed by a number of spikelets per panicle and single plant yield indicated that these traits could be utilised for selection in rice improvement. Study of association of yield attributing traits revealed that the single plant yield had a significant positive association with the total number of spikelets per plant, number of filled grains per plant and number of primary branches per plant and had a significant negative association with the length of the primary branches. Hence, direct selection of positively associated characters can improve the grain yield and increased primary branch length reduces the number of primary and secondary branches that might lead to a reduction in yield. Path coefficient analysis showed that the number of spikelets per panicle, primary branches per plant and length of secondary branches had a positive direct effect on yield. Therefore, giving weightage during selection to the above the mentioned traits could improve the yield and yield attributes. The principal component analysis showed that out of 18 traits studied, only eight principal components (PCs) had Eigen values greater than 1.00 and accounted for approximately 80.18% of the total cumulative variability. Single plant yield, number of fertile spikelets and total number of spikelets per plant and number of tillers showed maximum vector length confirming that the maximum contribution to the total diversity and the genotypes with the above characters could be utilized as donors to improve the yield and its attributing traits in future breeding programme. [ABSTRACT FROM AUTHOR]

In this study, the genetic diversity among forty-two rice genotypes were evaluated for fifteen quantitative and eleven qualitative traits using D2 statistics and DUS characterization. The genotypes were grouped into eight clusters of which the cluster VIII was the largest consisting of twelve genotypes. While, the clusters IV and VII were the smallest with a single genotype each. The maximum inter-cluster distance was observed between clusters I and II. Hence, the genotypes from these clusters could be used as parents for rice hybridization programmes in future. Among all traits, days to 50% flowering and apiculus colour were found to be the major contributing quantitative and qualitative traits towards genetic diversity. Beyond this, in this study Cluster II recorded the highest mean value for shoot length, plant height, flag leaf width, panicle length, number of seeds per panicle, 1000 grain weight and single plant yield. However, the cluster VII recorded the highest mean for seedling height, flag leaf length, grain length and grain width. Thus, the genotypes from these clusters which were Aanai Komban, Kichili samba and Karuppu kavuni could be used in improving the yield parameters in rice. Further, the correlation analysis for fifteen traits revealed a significant positive correlation of number of productive tillers, flag leaf length, flag leaf width, number of seeds per panicle, grain length and 1000 grain weight with single plant yield. Further the path analysis portrayed that the from these correlated traits, number of productive tillers, flag leaf width, number of seeds per panicle and grain length were observed to have a positive direct influence on yield. Thereby, it could be observed that these traits could be used as major indicators for selection of desirable genotypes for utilization in hybridization programme to develop elite rice genotypes. [ABSTRACT FROM AUTHOR]

This study aimed to assess the genetic variability, heritability, genetic gain and trait relationships of sixteen biometrical characteristics in a collection of eighty-nine rice cultivars, landraces and exotic lines. The focus was on understanding the degree of genetic divergence and identifying traits with high selection potential. The analysis revealed that economic yield improving traits like single plant yield, filled grains per panicle and total number of productive tillers showed high GCV, PCV, heritability and genetic gain implying the predominance of additive gene action and these traits can be given importance in selection and genetic advancement for yield improvement. Days to 50% flowering, plant height, total number of productive tillers, filled grains per panicle and thousand grain weight showed notable significant associations with single plant yield, with direct effects, asserting that these traits were most efficient and promising for selection. Cluster analysis revealed two clusters with cluster 1 mostly occupied by elite cultivars and cluster 2 occupied mostly by landraces and exotic lines. This information can be valuable for further studies and breeding programs, allowing researchers to focus on specific clusters for targeted genetic improvement or conservation efforts. [ABSTRACT FROM AUTHOR]

Summary: Aphelenchoides besseyi is among the most devastating plant-parasitic nematodes and causes severe loss, mainly on japonica rice in China. Recently the nematode has been found to be present in the seeds of indica rice and the hybrid rice cultivars also show symptoms of the nematode damage. To understand the variations in different rice cultivars against A. besseyi , the dynamics of nematode population, the incidence of symptoms and the effects on plant yield were investigated in field experiments during 2017-2018 by inoculation of mixed stages of A. besseyi onto the seeds and seedlings of different types of rice cultivars. The results showed few nematodes could be recovered from the plants at the seedling and the end of tillering stages in all the cultivars. After flowering, the number of nematodes per panicle increased and the highest number was found in 'Zheyou 18' in 2017 (1050.2) and 2018 (732.1). The average incidence of the inoculated plants showing white-tip symptoms ranged from 0.5 to 10.3% and from 0.0 to 75.7% at the tillering stage in 2017 and 2018, respectively. The incidences of white-tip symptoms in the indica cultivars, including '9311', 'Minghui 63' and 'Nei 5 you 39', were significantly lower than in 'Xingxiang', a japonica cultivar and 'Zheyou 18', a hybrid rice cultivar, both at the flowering stage in 2017 and at the end of the tillering stage in 2018. A strong interaction of the treatments and cultivars on the 1000-grain weight and panicle length was evident. [ABSTRACT FROM AUTHOR]

An ameliorant is a chemical that can be used to improve soil fertility. The improving agents include dolomite and steel slag. Steel slag is a byproduct of the steel industry containing CaCO3, SiO2, CaSiO3, and MgO, which can be used to improve the growth and yield of rice plants. Dolomite, on the other hand, is a limestone rock containing MgO and CaO, which is useful in agricultural soils. This study aimed to determine the types and doses of ameliorants affecting the growth and yield of rice plants (Oryza sativa L.). The research was carried out at Sukadana Village, Ciomas SerangBanten District. A nonfactorial Group Randomized Design with seven treatments was employed in this investigation. The treatments include P0 = No treatment (control), P1 = 2 t/ha of dolomite, P2 = 2 t/ha of dolomite + 2.5 t/ha of steel slag, P3 = 1.5 t/ha of steel slag, P4 = 2.5 t/ha of steel slag, P5 = 5 t/ha of steel slag, and P6 = 7.5 t/ha of steel slag. Observation was made on steel slag characterization, plant height, the total number of tillers, the weight of 1000 grains, the amount of grain per clump, and the weight of drymilled grain. The results showed that applying dolomite at 2 t/ha and steel slag at 2.5 t/ha could increase the weight of 1000 grains of rice, and applying steel slag at 1.5 t/ha could enhance the amount of grain per clump. [ABSTRACT FROM AUTHOR]

Rice (Oryza sativa L.) ratooning is one of the most essential production strategies to increase grain yield. Field experiments were conducted in southwestern Japan in 2021 and 2022 to determine the effects of planting date and cutting height of the first crop on grain yield. Grain yield of the second crop was higher at early planting date than at late planting date in 2021, but the yield difference was narrowed in 2022. The higher grain yield at early planting date resulted from the higher number of spikelets and percentage of filled spikelets due to the higher stubble nonstructural carbohydrate (NSC) content, leaf area index (LAI), and air temperatures. Grain yield of the second crop was higher at high cutting height than at low cutting height in 2021, but the yield difference was narrowed in 2022. The higher grain yield at high cutting height resulted from the higher number of spikelets due to the higher NSC content and LAI. In the weather conditions, grain yield had a strong positive correlation with the air temperature, which had positive correlations with the number of panicle and percentage of filled spikelets. In the stubble conditions, grain yield had a strong positive correlation with NSC content, which had positive correlations with the number of panicle and percentage of filled spikelets. Therefore, early planting, which secures high air temperatures, and high cutting height, which produces high NSC content, are recommended to increase grain yield of the second crop. Core Ideas: Early planting date generally had higher yield of the second crop.Yield difference of the second crop between planting dates was narrowed under high air temperature condition.High cutting height generally had higher yield of the second crop than low cutting height.Yield difference of the second crop between cutting heights was narrowed under high air temperature condition.Early planting and high cutting height are recommended to increase yield of the second crop. [ABSTRACT FROM AUTHOR]

Plant height and its relative traits are key factors that affect plant type and yield of sorghum. Mapping major QTL for these traits may provide a basis for genetic improvement in sorghum. In this study, a RI population including 205 lines obtained from a cross between American cultivar BTx623 and Guizhou liquor-brewing cultivar Hongyingzi was used to investigate plant height and internode numbers under five environments. The genetic map was constructed based on genotype data from Super-GBS technology, and major QTLs were identified by inclusive composite interval mapping（ICIM）. Totally, eighteen major QTLs were detected on chromosome 1, 3, 4, 8, and 9, of which 7 and 11 QTLs were related to plant height and internode numbers, respectively. Ten major QTLs were repeatedly detected in multiple environments or two traits, of which qPH9.1 was consistent with the known plant high gene Dw1, while qPH1.2, qPH3.2, qIN3.2 and qIN8.1 were colocalized with four homologous genes involving in plant height or internode elongation in rice. [ABSTRACT FROM AUTHOR]

The study was conducted during kharif season ( June–October) of 2016 at the Regional Agricultural Research Station, Agriculture College, Professor Jayashankar Telangana State Agricultural University (PJTSAU), Jagtial, Telangana, India. Forty (40) maintainer lines of rice (Oryza sativa L.) were grown in randomized block design replicated twice to find the relationships between the yield and its components, as well as their direct and indirect effects on the rice grain yield. Observations were recorded for yield, yield attributing characters and quality traits on five randomly selected competitive plants for each entry in each replication for 15 characters. The results revealed that the analysis of variance was significant for all the characters investigated. Grain yield was significantly correlated with its component characters like number of tillers plant-1 (0.9191**), panicle length (0.3339**), milling percentage (0.3214**) and hulling percentage (0.2873**) whereas it showed a negligible positive correlation with days to 50% flowering, days to maturity, plant height, panicle length, number of grains per panicle, kernel length, kernel breadth, L/B ratio, test weight, hulling percentage, and head rice recovery percentage. Path coefficient analysis revealed that number of tillers plant-1 (0.9439) exerted maximum positive direct effect on plant yield followed by kernel breadth, L/B ratio, panicle length, milling percentage, days to flowering and head rice recovery percentage indicated their importance in determining the complex character and therefore should be kept in mind while practicing selection aimed at improving the grain yield. [ABSTRACT FROM AUTHOR]

In Northeast China, the frequency and intensity of chilling events has been increasing continuously, which places regional rice production at an increasing risk for yield loss. Previous studies have shown that continuous chilling at the tillering, booting and flowering stages could reduce rice grain yield. However, the effects of intermittent chilling at different growth stages on rice yield have rarely been reported. In this study, we conducted a temperature‐controlled experiment on rice plants at the tillering, booting and flowering stages, with both continuous and intermittent chilling treatments at two chilling temperatures and four chilling durations. The results showed that rice grain yield was most affected by chilling at the booting stage, followed by chilling at the flowering stage and least affected by chilling at the tillering stage. For per 1 day increase in chilling duration, the continuous (intermittent) chilling treatment at T1 (11°C/12°C/12°C) at the tillering, booting and flowering stages decreased the grain yield per plant by 1.0%, 6.0% and 2.9% (0.9%, 2.7% and 1.6%), respectively. For per 10°C·day increase in cooling degree days, the continuous (intermittent) chilling treatment at the booting stage decreased the grain yield per plant, spikelet fertility, grain number per spike and thousand grain weight by 10.7%, 7.9%, 5.4% and 1.6% (5.6%, 1.5%, 4.4% and 1.2%), respectively. While the continuous (intermittent) chilling treatment at the flowering stage decreased the grain yield per plant and spikelet fertility by 4.9% and 3.9% (2.8% and 3.2%), respectively. Our study is complementary to the current knowledge gap concerning the mechanism of chilling‐induced yield losses for rice. In particular, the results of this study could be used to (a) modify the chilling effects algorithms in rice models to improve the simulation accuracy in rice yields and (b) target the genetic features to breed new rice varieties with greater cold tolerance. [ABSTRACT FROM AUTHOR]

The ideal rice phenotype is that of plants exhibiting fewer panicles with high biomass, large grain number, flag leaf area with small insertion angles, and an erected morphology improving light interception. The sunflower transcription factor HaHB11, homeodomain–leucine zipper I, confers increased seed yield and abiotic stress tolerance to Arabidopsis and maize. Here, we report the obtaining and characterization of rice plants expressing HaHB11 driven by its promoter or the 35S constitutive one. Transgenic p35S:HaHB11 plants closely resembled the ideal high-yield phenotype, whereas those carrying the pHaHB11:HaHB11 construct were hard to distinguish from the wild type. The former had an erected architecture, enhanced vegetative leaf biomass, rolled flag leaves with a larger surface, sharper insertion angles insensitive to brassinosteroids, and higher harvest index and seed biomass than the wild type. The combination of the distinct features exhibited by p35S:HaHB11 plants, including the increased number of set grains per panicle, supports the high-yield phenotype. We wondered where HaHB11 has to be expressed to achieve the high-yield phenotype and evaluated HaHB11 expression levels in all tissues. The results indicate that its expression is particularly necessary in the flag leaf and panicle to produce the ideal phenotype. [ABSTRACT FROM AUTHOR]

A total of 64 medium duration rice accessions were evaluated for their genetic variability and genetic divergence during Rabi season 2020 at Pandit Jawaharlal Nehru College of Agriculture and Research Institute, Karaikal. Analysis of variance revealed significant differences for all the traits considered for the study. The traits spikelets per panicle and filled grains per panicle recorded high GCV as well as PCV thereby indicating that these traits would be improved effectively through selection. Other yield component traits viz., plant height, productive tillers per plant, spikelets per panicle, filled grains per panicle, fertility per cent, grain weight and single plant yield revealed high heritability coupled with high genetic advance, indicating that simple selection could be effective for improving these characters. The D2 values and hierarchical clustering analysis grouped the 64 germplasm into seven clusters. In both the clustering methods, the genotype Gold 44 was grouped under separate clusters indicating that, this is a diverse genotype among all the genotypes taken for study. Further, genotype AD 16124 was grouped under the same cluster in both the clustering methods with the highest cluster mean for grain yield per plant. Hence, this genotype could be efficiently utilized for the yield improvement programme in rice. [ABSTRACT FROM AUTHOR]

An experiment was conducted with a view to obtain information of genetic parameters of variation and character association for 13 quantitative traits in a set of 64 rice cultivars of Assam. The study revealed significant differences for all the traits under study. Highest genotypic coefficient of variation was observed for the trait biological yield followed by harvest index and grain yield. More than 80% heritability was observed for all the traits except grain yield, effective tillers per plant and biological yield. Genetic advance as per cent of mean was highest for biological yield followed by harvest index, filled grains per panicle and grain yield. Higher magnitude of genetic advance along with considerably high heritability observed for harvest index, filled grains per panicle and biological yield indicated that these traits could be considered for selection to obtain high genetic gain. Character association studies indicated that direct selection of 100 - grain weight, grain length, grain breadth, biological yield and harvest index, would bring about improvement in grain yield. Non-significant association of grain yield with important yield attributes viz., filled grain per panicle, tillers per plant and panicle length were due to their strong association with duration of genotypes, which in turn was negatively associated with grain yield. Recombination breeding and recurrent selection, therefore, could be suggested to break the negative linkage in order to achieve further genetic improvement. [ABSTRACT FROM AUTHOR]

In the current study, 20 elite rice genotypes were crossed with four CMS lines-CMS 23A, CMS 59A, CMS 64A and JMS 13A in a line x tester mating design and assessed alongside standard controls (JKRH 3333 and MTU 1001) to determine the best heterotic combinations in terms of grain yield and yield component characters at the Rice Research Centre, Rajendranagar. Eight restorer lines were found in Kharif 2018-19 based on pollen and spikelet fertility (MTU 1153, RNR 26015, RNR 28355, JGL 25960, MTU 1010, IET 27253, RNR 26085 and JAYA). The resulting 32 hybrids of 8 restorer lines and their corresponding CMS lines are studied for combing ability and heterosis. The degree of heterosis varied between traits. Three of the 32 hybrids under study had considerable standard heterosis for grain yield viz., JMS 13A x MTU 1153, CMS 59A x RNR 26015 and CMS 64A x MTU 1153, which outperformed the best checks JKRH 3333 and MTU 1001. The best experimental hybrid, JMS 13A x MTU 1153, yielded the most grain yield per plant, 62.89g (Table 1). Further testing of these three experimental hybrids will take place in areas conducive to extensive commercialization. [ABSTRACT FROM AUTHOR]

MTU 1010 is an early maturing and high-yielding mega rice variety widely grown in an area of 3 Mha. It is characterised by limited grain number and panicle branching. To improve the grain number in MTU 1010, an IRRI breeding line, IR121055-2-10-5 was utilized as donor to transfer yield-enhancing genes Gn1a and OsSPL14 (associated with increased grain number and better panicle branching, respectively) into MTU1010 by Marker-Assisted Backcross Breeding (MABB). At each backcross generation, foreground selection was carried out with Gn1a and OsSPL14- specific molecular markers, whilst background selection was done with a set of SSR markers polymorphic between the IR121055-2-10-5 and MTU1010. With the use of a gene-specific marker, homozygous BC2F2 plants carrying the yield-enhancing gene were identified and advanced through pedigree-method of selection till BC2F6 and best performing ten lines were selected and evaluated in replicated station trials for yield contributing traits, where grain number and brancing per panicle exhibited high significant and positive correlation with single plant yield. Three promising lines namely RP6353-5-8-13-24, RP6353-26-13-39-5 and RP6353-32-12-8-16 with higher grain number and yield than MTU1010 were identified and nominated for evaluation in Initial Varietal Trial-Aerobic (IVT-Aerobic) of All India Crop Improvement Programme on Rice (AICRP), of which RP6353-26-13-39-5 (IET28674), was promoted for further testing. [ABSTRACT FROM AUTHOR]

Drought occurrence during reproductive stage of rice leads to significant yield loss. Rice production has to be doubled to feed the ever increasing human population. As the yield levels are stagnated under favourable production system, improvement of yield under unfavourable environment is key to attain the projected target. Therefore, the present study was undertaken to improve the drought tolerance of popular rice variety ADT(R)45 by introgressing major effect quantitative trait loci (QTLs) conferring yield under drought (qDTY1.1, qDTY3.1 and qDTY12.1) through marker assisted backcross breeding (MABB). Through MABB, 117 BILs in the background of ADT(R)45 were developed with different combinations of qDTY QTLs. The BILs were evaluated under rainfed target production environment and observations on nine biometrical and yield traits were recorded. Variability analysis revealed presence of additive gene action for the traits viz., total number of tillers per plant, number of productive tillers per plant, hundred grain weight, yield per hectare and single plant yield. Hence, selection based on these traits will be effective to improve yield under drought stress. Association analysis showed total number of tillers per plant, number of productive tillers per plant, panicle length, hundred grain weight and spikelet fertility percentage were highly correlated with yield per plant. Comparison of BILs with different QTL combinations showed that BILs with single QTL (qDTY12.1) was better for most of the traits studied. BILs with single or two QTL combinations were found to perform better under rainfed condition, when compared to BILs with all the three QTLs. [ABSTRACT FROM AUTHOR]

The present investigation was performed to explain the genetic variability and association parameters of twenty traits in 30 F1s involving six parents differing in resistance against false smut in rice. Breeding materials were evaluated at hotspot location viz., HREC, Gudalur. The ANOVA revealed significant differences among the studied variables. Higher PCV over other coefficients of variation suggest the role of environment in trait expression. Disease related traits viz., NIP, NIT, NIGPa, PIT, PIGPa and agronomic traits viz., TNFPa, NCGPa, SSP, PH, HGW and SPY showed high magnitude of values for GCV, heritability and GAM indicating the role of additive gene action. Hence, selection of these traits may be effective. Correlation studies indicated that HGW and SPW showed positive significant association with SPY. Path analysis revealed that NIT, NIGPa, NIGP and PIP had negative direct effect and DFF, NPT, TNFPa, SSP, NSRPa and SPW had positive direct effect towards single plant yield. [ABSTRACT FROM AUTHOR]

Aims: The gene qPE9-1, which encodes the G protein γ subunit, is important for nitrogen (N) use in rice and in regulating rice photosynthesis under elevated CO2 (eCO2). However, under a changing climate, the qPE9-1 response to combined increasing atmospheric CO2 (aCO2) and soil N availability is unclear. Therefore, we investigated the regulative roles of qPE9-1 in rice N use under eCO2. Methods: Wild-type (WT) and qPE9-1 RNAi rice plants were exposed to low (LN) and high (HN) N treatments under aCO2 (400 ppm) and eCO2 (800 ppm) in the growth chamber and the field Open-Top Chamber (OTC). Rice growth, net photosynthetic rate, and N uptake were determined in the growth chamber. Then, the OTC was used to evaluate to the combined impacts of eCO2 and N on rice yield. Results: Under HN conditions, the dry weight and net photosynthesis rate of WT plants was significantly increased under eCO2 compared with aCO2; however, there was no significant difference in the qPE9-1 RNAi lines. The CO2 and N levels had relatively minor effects on the carbon concentration of all plants. Regardless of the CO2 concentration, the N concentrations in the roots and leaves of all plants were significantly reduced under LN treatment compared with HN. Under LN conditions, eCO2 enhanced the N content of WT plants, but had no significant effects on the RNAi lines. The grain yield of WT plants was also significantly increased by eCO2 under HN treatment in the field OTC, whereas the RNAi lines were not affected. Conclusion: The G protein γ subunit qPE9-1 is involved in N uptake under elevated CO2; however, this response is affected by N levels. These findings provide useful information on efficient N management for adapting to the future CO2-enriched environment. [ABSTRACT FROM AUTHOR]

Nitrogen (N) is the element supplied by the soil that limits the development of irrigated rice. The hypothesis of the present is that to meet higher demand for N by the plant due to the higher potential yield, it is not necessary to apply a higher dose of N fertilizer. This studyevaluated the efficiency of N utilization, the rate of growth and accumulations of N by plants and the grain yield of two rice cultivars, short cycle and medium cycle, with and without N fertilization. A field experiment was installed in the Rio Grande do Sul, southern Brazil. The treatment factors evaluated were cultivar, with medium and short cycles, with doses of 0 and 150 kg N ha-1. Growth curves, absorption rate, N content and leaf area index over time, root area and grain yield were analyzed. The medium cycle cultivar has a greater potential to explore the environment when compared to the short cycle rice cultivar, both for greater leaf area and root area per cultivation area, as well as for longer exploration times. Thus, the medium cycle cultivar has greater N utilization efficiency and higher grain yield. [ABSTRACT FROM AUTHOR]

Crop varieties with a high yield are most desirable in the present context of the ever-growing human population. Mostly, the yield traits are governed by a complex of numerous molecular and genetic facets modulated by various quantitative trait loci (QTLs). With the identification and molecular characterizations of yield-associated QTLs over recent years, the central role of phytohormones in regulating plant yield is becoming more apparent. Most often, different groups of phytohormones work in close association to orchestrate yield attributes. Understanding this cross talk would thus provide new venues for phytohormone pyramiding by editing a single gene or QTL(s) for yield improvement. Here, we review a few important findings to integrate the knowledge on the roles of auxin, brassinosteroid and cytokinin and how a single gene or a QTL could govern cross talk among multiple phytohormones to determine the yield traits. [ABSTRACT FROM AUTHOR]

The present study aimed to determine the nature and extent of genetic divergence for agro-morphological and quality traits amongst advanced breeding lines of rice utilizing multivariate techniques. Based on the inter se D2 values, breeding lines were grouped into six non-overlapping clusters, indicating presence of diversity amongst the lines. Cluster I and Cluster II were found to be the largest clusters consisting of 14 and 9 genotypes, respectively, while, the remaining four clusters were mono-genotypic. The maximum inter-cluster distance was observed between cluster II and VI, while the maximum intra-cluster distance was recorded for cluster II. Breeding lines present in cluster II were observed to have highest cluster means for traits viz., plant height, total number of tillers per plant, amylose content, grain yield per plant and grain yield per plot indicating its superiority over rest of the clusters. Traits including grain yield per plot, grain yield per plant, days to maturity, 1000-grain weight, total number of tillers per plant and panicle length were observed to be the major contributors to genetic divergence. Principal component analysis extracted six principal components of which first five components viz., PC-I to PC-IV had eigen scores greater than one. This suggested that traits within these axis were of importance. Principal component analysis revealed that the traits viz., number of effective tillers per plant, grain yield per plot, plant height, panicle length and days to 50 per cent flowering contributed maximum towards genetic diversity. [ABSTRACT FROM AUTHOR]

The study was carried out to learn about the nature of gene action and combining ability in rice hybrids for grain yield and its component traits. For this, eight lines were crossed with four testers in an L x T mating design. The analysis of variance revealed significant variance for all the characters studied among the parents and hybrids. GCA variances were higher than SCA variances for most of the characters, indicating the predominance of additive gene action, while SCA variances were higher than GCA variances for number of productive tillers per plant, pollen fertility, hulling, milling, head rice recovery and grain yield per plant, indicating the predominance of non-additive gene action. The testers JMS 13A (3.91) and CMS 59A (2.46), as well as the lines MTU 1153 (9.52), RNR 28355 (3.26) and RNR 26085 (3.09), were the best combiners for grain yield and important yield components due to positive GCA effects. Based on SCA effects and corresponding mean performance for grain yield and its component traits, the hybrids CMS 59Ax RNR 26015, CMS 23A x JGL 25960, CMS 64Ax RNR 26015 and JMS 13Ax MTU 1153 were identified as the best specific combiners. These hybrids could be tested in multi-environment trials for commercial use. [ABSTRACT FROM AUTHOR]

Rice (Oryza sativa L.) is the staple food crop and it is cultivated under diverse ecological conditions. Understanding genetic effects and identifying superior hybrids are important steps in rice breeding to enhance yield. Six parents with varying numbers of grains per panicle were subjected to full diallel mating. Hayman's graphical approach was applied to compute various genetic parameters and better parental, mid parental and standard heterosis for panicle and yield related traits. The results revealed that, grain yield per plant and panicle related traits were governed by both additive and non-additive effects but the additive component was predominant for the number of filled grains per panicle and non-additive for grain yield per plant. The number of spikelets per panicle, the number of filled grains per panicle and the number of primary branches per panicle were mainly governed by recessive alleles present in the parents. The overdominance effect was found in the number of productive tillers, flag leaf area, panicle length, the number of primary branches per panicle, length of primary branches, thousand grain weight and grain yield per plant. The Vr-Wr graph depicted that the number of spikelets per panicle, the number of filled grains per panicle and the number of secondary branches per panicle were governed by partial dominance and grain yield per plant had over dominance effect and the low grain number parents, IET 28835 and ADT (R) 48 possessed more number of dominant alleles than other parents for all these traits. The promising cross combination BPT 5204 × CB12132 and its reciprocal hybrid exhibited high mid parental and standard heterosis for important panicle traits were adjudged as promising hybrids. [ABSTRACT FROM AUTHOR]

Sixty four parental lines of hybrid rice were evaluated for genetic divergence by taking into account of nine traits during two seasons of year 2018. By resolving the parental lines into ten groups, Ward's clustering method demonstrated the parental lines having significant genetic diversity. Cluster X had the most parental lines (13) out of all the clusters, followed by cluster II (12 genotypes). The parental line clusters IX, VIII, VII, V, and IV, which correspond to SD-5, SD-2, HSRV-16, GR-37, and SD-39, respectively, showed the significant degree of variability. Screening for fertility restoration was done in 64 parental lines with the help of SSR molecular markers. Among them, 44 potential restorers were identified (Rf4 and Rf3 present) with a hundred percentage efficiency supported molecular screening. The traits number of productive tillers per plant, length of the panicle and number of grains per panicle were significantly correlated with the trait grain yield per plant. Path analysis showed that the traits number of grains per panicle, the number of productive tillers per plant, test weight and panicle length had positive direct effects on grain yield and indicating that selection for these yield contributing traits could lead to an improvement in single plant yield as a whole. [ABSTRACT FROM AUTHOR]

Rice leaf is a solar panel of photosynthesis and determines the light energy utilization and yield of plants. Leaf numbers appear as S-type or parabola-type growth curves throughout their development. However, the ways in which the genes regulate the process of leaf numbers still remain poorly understood. This paper first identified five QTLs associated with leaf numbers using single-segment substitution lines (SSSLs). Then, the epistatic effects between double QTLs were estimated via the decomposition of the QTL polymerization effects. Additionally, further the expression patterns and functions for these five QTLs and their epistasis were revealed by the methodologies of conditional QTL mapping and functional QTL mapping, respectively. The five SSSLs were detected as having significant additive and/or dominant effects at one or more stages, all of which increased the leaf numbers, except for the negative additive effect of the first SSSL. Seven pairs of QTLs interacted each other via three or four epistatic components, with the opposite effects in the case of single genes, i.e., most epistatic effects were negative. The five QTLs expressed their effects mainly in three stages, namely within 14 days, from 28 days to 42 days, and from 49 days to 63 days after transplantation. Positive effects and negative interactions of the QTLs were observed in the early and the late stages, but opposite interactions were observed in the middle stage. Mainly, three functional parameters, including the inflexion point, the peak value, and the degradation rate, were regulated via the QTL effects and their opposite interactions. This paper uncovered the genetic rule of five QTLs on the leaf numbers, including the interaction, expression, and function features. The information will be helpful to understand the genetic mechanism for developmental traits. [ABSTRACT FROM AUTHOR]

Panicle length (PL) is an important trait that determines panicle architecture and strongly affects grain yield and quality in rice. However, this trait has not been well characterized genetically, and its contribution to yield improvement is not well understood. Characterization of novel genes related to PL is of great significance for breeding high-yielding rice varieties. In our previous research, we identified qPL5, a quantitative trait locus for PL. In this study, we aimed to determine the exact position of qPL5 in the rice genome and identify the candidate gene. Through substitution mapping, we mapped qPL5 to a region of 21.86 kb flanked by the molecular marker loci STS5-99 and STS5-106 in which two candidate genes were predicted. By sequence analysis and relative expression analysis, LOC-Os05g41230, which putatively encodes a BRASSINOSTEROID INSENSITIVE 1-associated receptor kinase 1 precursor, was considered to be the most likely candidate gene for qPL5. In addition, we successfully developed a pair of near-isogenic lines (NILs) for qPL5 in different genetic backgrounds to evaluate the genetic effects of qPL5. Agronomic trait analysis of the NILs indicated that qPL5 positively contributes to plant height, grain number per panicle, panicle length, grain yield per plant, and flag leaf length, but it had no influence on heading date and grain-size-related traits. Therefore, qPL5 and the markers tightly linked to it should be available for molecular breeding of high-yielding varieties. [ABSTRACT FROM AUTHOR]

Leaf angle is an influential agricultural trait that influences rice (Oryza sativa L.) plant type and yield, which results from the leaf bending from the vertical axis to the abaxial axis. UV-B radiation affects plant morphology, but the effects of varying UV-B intensities on rice flag leaves and the underlying molecular, cellular, and physiological mechanisms remain unknown. This experiment aims to examine the effect of natural light and field-enhanced UV-B radiation (2.5, 5.0, 7.5 kJ·m−2) on the leaf angle of the traditional rice variety Baijiaolaojing on Yuanyang terraces. In comparison with natural light, the content of brassinolide and gibberellin in rice flag leaves increased by 29.94% and 60.1%, respectively. The auxin content decreased by 17.3%. Compared with the natural light treatment, the cellulose content in the pulvini was reduced by 13.8% and hemicellulose content by 25.7% under 7.5 kJ·m−2 radiation intensity. The thick-walled cell area and vascular bundle area of the leaf pulvini decreased with increasing radiation intensity, and the growth of mechanical tissue in the rice leaf pulvini was inhibited. The flag leaf angle of rice was greatest at 7.5 kJ·m−2 radiation intensity, with an increase of 50.2%. There are two pathways by which the angle of rice flag leaves is controlled under high-intensity UV-B radiation. The leaf angle regulation genes OsBUL1, OsGSR1, and OsARF19 control hormone levels, whereas the ILA1 gene controls fiber levels. Therefore, as cellulose, hemicellulose, sclerenchyma, and vascular bundles weaken the mechanical support of the pulvini, the angle of the flag leaf increases. [ABSTRACT FROM AUTHOR]

The present study was carried out during kharif (June-September, 2019) and from January to mid of May 2020 at AC&RI, Madurai, Tamilnadu state, India. From the segregating populations of F3 and F4 generations of the cross ASD16×Improved Pusa Basmati 1 to estimate the effectiveness of selection for yield and its contributing traits. F3 generation was raised in single seed decent method in the non-replicated manner and line sowing was taken in F4 generation. Positively skewed and platykurtic curve was observed for the trait hundred seed weight in the both generations this result revealed that the trait was controlled by the complementary type of gene action hence showing that intense selection is needed to obtain more genetic gain from these traits. The parent progeny regression and intergenerational correlation showed positive and highly significance for the quantitative traits i.e., days to 50% flowering, number of productive tillers, number of filled grains panicle-1, and single plant yield, plant height and hundred grain weight. Narrow sense heritability was observed for the traits viz., days to 50% flowering, single plant yield, number of productive tillers, panicle length, number of filled grains panicle-1 infer that these traits carried their additive×additive component and helped in the fixation of the characters in the early generation itself. [ABSTRACT FROM AUTHOR]

Climate change increases the drought-affected areas, which challenge the breeders to develop adaptive and drought-tolerant rice cultivars. The study aimed to determine heritability, and gene action controlling of various traits in upland rice F4 populations derived from the cross, Sileso (high yielding and drought tolerant) × Ciherang (early maturing), and to obtain high-yielding and earlymaturing rice lines. The upland rice F4 populations, along with parental and check cultivars, were planted in augmented design from July to November 2021 at the Faculty of Agriculture, Samudra University, Langsa, Indonesia. Analysis of variance showed significant differences among the check cultivars for the traits, such as, panicle length, productive tillers, filled grains per panicle, and grain yield per plant. The F4 population families revealed significant differences for the maturity, filled grain per panicle, and grain yield per plant, which confirmed greater genetic diversity, and proved potential to produce the best lines. The check vs. family interactions also exhibited significant differences for all the characters. Results revealed high heritability for the traits, i.e., maturity, filled grain per panicle, and grain yield per plant. The inheritance of all the characters was controlled by the additive gene action. Inheritance of the majority of the traits was polygenic except plant height and productive tillers. The selected and promising upland rice F4 populations revealed reduced plant height, maturity, and increased yield per plant compared with its rice parental cultivar 'Sileso'. [ABSTRACT FROM AUTHOR]

For designing of the breeding programme, analysis of genetic variability and character correlation is crucial in crop improvement. The aim of this experiment was to estimate genetic variability parameters and trait association for 13 quantitative traits which were measured in F2 segregating populations of six crosses containing nine parents. All the F2 populations showed significant GCV and PCV values for productive tillers per plant, grains per panicle, grain yield per plant and straw yield per plant, indicating that these traits may be improved through selection. Plant height, productive tillers per plant, grains per panicle, grain yield per plant and straw yield per plant showed high heritability coupled with high genetic advance, indicating that these traits were controlled by additive gene action and have a good chance of improvement through pure line selection. Grain yield per plant exhibited a strong positive correlation with plant height, panicle length, grains per panicle, straw yield per plant, productive tillers per plant and harvest index in all the six F2 segregating populations. The F2 population of the cross GR 17 × NVSR 2740 demonstrated that more GCV and PCV, high heritability with high genetic advance for the majority of the traits which can be improved by selection. [ABSTRACT FROM AUTHOR]

Sixty-nine cultivars of rice were examined for fourteen biometrical characteristics to study the degree of genetic divergence, heritability and genetic gain as a percentage of mean, character relationship and path coefficient analysis. Yield per plant reported the highest estimate of PCV and GCV followed by the total effective tillers per plant, hundred seed weight, number of filled seeds per panicle and flag leaf length indicating that these traits may be given importance while exercising selection. Plant height, panicle length, total tillers, total effective tillers per plant, flag leaf length, grain length, grain L/B ratio, the number of filled seeds per plant, hundred seed weight and yield per plant exhibited remarkable genetic gain and high heritability, implying a predominance of additive gene action. Hence, genetic advancement through simple selection would be more beneficial. Among the yield traits examined, days to 50% flowering, total tillers per plant, the number of effective tillers per plant, flag leaf breadth, the number of filled seeds per panicle, and hundred-seed weight recorded a positive significant correlation with direct effects on yield per plant asserting that these traits were the most efficient and promising selection criteria. [ABSTRACT FROM AUTHOR]

An experiment was conducted with 39 rice genotypes to screen for salt tolerance and evaluate potential variation among the genotypes under sodic conditions. All the 39 rice genotypes along with two check varieties (TRY2 & TRY5) were screened in vitro for salt tolerance by imposing 100 mM NaHCO3 at the seedling stage under hydroponics and a salt injury score was given based on morphological symptoms. Observations on 12 biometrical traits were recorded under field sodic conditions and subjected to variability analysis. The ANOVA revealed that there was a significant difference for the 11 traits among the genotypes except for flag leaf breadth. Among the genotypes, the highest single plant yield was recorded by RG 50 (36.83 g). A correlation study revealed that, single plant yield exhibited significant and positive genotypic and phenotypic relation with panicle harvest index, the number of grains per panicle and panicle length. Path analysis showed that the traits viz., panicle harvest index, plant height and panicle length had a very high and positive direct effect on single plant yield. The traits viz., flag leaf breadth, SPAD meter reading and number of productive tillers per plant had a high and positive direct effect on single plant yield. In vitro studies revealed that the genotype RG113 was found to be highly tolerant to salt stress and it also showed a significantly higher yield (35.42 g) under field sodicity. The genotypes RG22, RG150, RG162 and RG188 which showed tolerance under in vitro screening and the moderately tolerant genotypes RG26, RG50, RG95, RG107, RG123 and RG176 were exhibiting significant yield under field sodicity conditions. Therefore, in order to breed for high yielding salt-tolerant rice varieties, the identified genotypes could be exploited as donor genotypes. [ABSTRACT FROM AUTHOR]

The present investigation was carried out to understand the genetic variability, association, cause and effect relationships between yield and its attributing agronomic and physiological traits in 23 F3 families of pre-breeding restorer germplasm in a hybrid rice program for six agronomic and three physiological characters. The variability and heritability parameters were grouped under the high category for the number of productive tillers per plant, leaf area per plant, dry matter production and single plant yield. The traits viz., the number of tillers per plant and panicle length, leaf area per plant and dry matter production showed a direct correlation with single plant yield and in cause and effect relationships. All traits had a direct influence on single plant yield except days to 50% flowering and chlorophyll index. At the intra-family level, six families namely 30, 35, 36, 46, 55 and 82 showed high variability and heritability values of all parameters for six traits. All nine traits exhibited normal distribution. [ABSTRACT FROM AUTHOR]

Traditional rice varieties having high flavonoids and anthocyanin traits were hybridized to high-yielding quality cultivars to assess their combining ability. Significant variation was observed among parents and hybrids for the traits studied. The predominance of non-additive gene action was observed for single plant yield, total flavonoid content, amylose content, whereas, trait anthocyanin registered additive gene action in the study. The genotypes ADT 37 and ADT (R) 45 were found to be good general combiners for flavonoids and anthocyanin content. The hybrid ADT (R) 45 x IG6 exhibited significant sca for flavonoids, anthocyanin and amylose per cent. The hybrid ADT (R) 45 x Mikkuruvai exhibited significant per se and sca for single plant yield and flavonoid content. [ABSTRACT FROM AUTHOR]

An investigation was conducted with 217 germplasm lines of rice to estimate potential variation among rice genotypes. Multivariate analyses viz., PCA and cluster analysis to assess genetic diversity were performed on seven agronomic traits. For the evaluated traits in the lines of germplasm, box plots and normal probability plots displayed substantial estimates of variability. PCA showed that PC1 and PC2 represented 46.15 per cent of variation. PC1 was responsible for the most variance (24%) for four characters, followed by PC2 (22.15%) for three parameters. Filled grain number per panicle, single plant yield, plant height and thousand grain weight were identified as vital traits contributing to variability. Based on agglomerative hierarchical cluster analysis, the germplasm lines were grouped into five clusters, which explained a lot of variation in the traits. The study identified that plant height and 1000 grain weight have the greatest impact on variation. The genotypes viz., WGL 1063, RNR 26085, OR 2511-3, Swarna, KNM 7123, WGL 1063, MGD-101, IVT MS-6130, IVT IM-4231, IVT IME-3948 and IVT NPT-6303 were found to be the best performing genotypes for the traits panicle length, plant height and single plant yield, which can be used in hybridisation programme to improve these traits. [ABSTRACT FROM AUTHOR]

Background: Rice (Oryza sativa L.) gets affected by more than seventy diseases by the infection of bacteria, fungi and viruses. Among, bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv oryzae (Xoo) is the important disease around the rice cultivated areas and causing drastic yield losses ranging between 20 and 30 per cent. Among very few options for increasing yield potential in rice, genetic diversity among the genotypes plays an important role in selection of parents having wider variability for disease resistance. Methods: The rice genotypes were screened using PDI for bacterial leaf blight (BLB) and subjected to D2 analysis for nine quantitative traits viz., plant height, number of productive tillers per plant, panicle length, days to fifty per cent flowering, number of grains per panicle, thousand grain weight, grain length, grain breadth and single plant yield. Result: On the basis of Mahalanobis D2 statistics, the thirty five genotypes are grouped into VIII clusters. The highest intra cluster distance was recorded for cluster II (41.16) followed by cluster VI (37.73). Out of thirty five genotypes screened under field condition using percentage disease index (PDI), CR 1009 found to be resistant with the lowest PDI value of 9.67 per cent. The genotypes Karsamba, TPS 4 and Kaivara samba registered highest PDI value of 70.67, 67.22 and 66.67 respectively. The BLB resistance in genotype dependent and not cluster based. The resistant genotype CR 1009 under field screening was positioned in VI cluster. The cluster II had susceptible genotypes karsamba and kaivarasamba. Thus, the identified genotypes can be utilized in recombination breeding to provide BLB resistance segregants. [ABSTRACT FROM AUTHOR]

Optimum growing temperature is necessary for maximum yield-potential in any crop. The global atmospheric temperature is changing more rapidly and irregularly every year. High temperature at the flowering/reproductive stage in rice causes partial to complete pollen sterility, resulting in significant reduction in grain yield. Green Super Rice (GSR) is an effort to develop an elite rice type that can withstand multiple environmental stresses and maintain yield in different agro-ecological zones. The current study was performed to assess the effect of heat stress on agronomic and physiological attributes of GSR at flowering stage. Twenty-two GSR lines and four local checks were evaluated under normal and heat-stress conditions for different agro-physiological parameters, including plant height (PH), tillers per plant (TPP), grain yield per plant (GY), straw yield per plant (SY), harvest index (HI), 1000-grain weight (GW), grain length (GL), cell membrane stability (CMS), normalized difference vegetative index (NDVI), and pollen fertility percentage (PFP). Genotypes showed high significant variations for all the studied parameters except NDVI. Association and principal component analysis (PCA) explained the genetic diversity of the genotypes, and relationship between the particular parameters and grain yield. We found that GY, along with other agronomic traits, such as TPP, SY, HI, and CMS, were greatly affected by heat stress in most of the genotypes, while PH, GW, GL, PFP, and NDVI were affected only in a few genotypes. Outperforming NGSR-16 and NGSR-18 in heat stress could be utilized as a parent for the development of heat-tolerant rice. Moreover, these findings will be helpful in the prevention and management of heat stress in rice. [ABSTRACT FROM AUTHOR]