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Twenty F1 s, parents and checks viz., MTU 1010 and RNR 15048 were assessed for grain yield and its contributing attributes to study combining ability and heterosis. The mean of hybrids was greater than that of the parents except for days to 50% flowering and plant height. For majority of the investigated characters, the analysis of variance indicated considerable variations among parents and hybrids. Degree of dominance was more than unity for majority of traits including grain yield. For the examined characters, SCA variances were equal to GCA variances, indicating the dominance of additive and non-additive gene activity. The traits days to 50 % flowering, plant height, panicle length, test weight, kernel length and kernel length/breadth ratio showed additive gene action whereas the remaining traits showed non-additive gene action. The gca effects revealed that among the lines IR 72 had significant gca effects in desired direction for yield and yield attributing traits. Among the 20 hybrids, MTU 1001 x Akshyadhan was found to be a good specific combiner for grain yield per plant. Similarly, the hybrids NLR 34449 x IR10N270 and IR 72 x IR10N270 were found to be good specific combiners for grain yield and yield contributing characters. The standard heterosis of these three hybrids was positively significant over the check varieties MTU 1010 and RNR 15048. Based on mean, sca and heterosis estimates, MTU 1001 x Akshyadhan, NLR 34449 x IR10N270 and IR 72 x IR10N270 were identified as promising hybrids. [ABSTRACT FROM AUTHOR]

The present study was undertaken to investigate the genetic parameters of yield component and quality traits of the F3 population from BPT 5204 and JAK-686 cross in rice. High heritability and high genetic advance as a percentage of the mean were recorded for productive tillers per plant, grains per panicle, panicle length and grain yield per plant indicating the effectiveness of direct phenotypic selection for improvement of these traits. For traits such as grains per panicle, 1000 grain weight, amylose content and grain protein content, the magnitude of additive (d) effects surpassed dominance (h) gene effects. This implies that phenotypic selection using methods like pureline selection, mass selection would be beneficial. Gel consistency exhibited complimentary gene interaction. Furthermore, duplicate gene interaction was prevalent in traits like days to 50% flowering, productive tillers per plant, plant height, panicle length, grain yield per plant, kernel length, kernel breadth, and kernel L/B ratio, making selection in later generations more effective. The inheritance studies highlighted the importance of selecting desired recombinants from the segregating population to enhance rice quality as well as grain yield.

In the present global warming scenario, it is urgent to impart heat tolerance into the popular high yielding rice (Oryza sativa L.) varieties to reduce yield loss to a great extent. Uma (a prevalent red-grained rice variety in Kerala) was crossed with Nagina 22 (N22), the popular donor for heat tolerance. From the seven promising heat-tolerant F3 plants previously identified through marker assisted selection and field screening, F4 lines (58 nos.) were raised and characterised morphologically. Heat tolerance was scored under natural heat stress during hot summer months in field conditions. Among the evaluated F4 progenies, 26 promising plants registered >75% spikelet fertility. Double panicles were observed in some of the tillers of fourteen F4 plants. During the selection with reported polymorphic markers between parents, all the 26 F4 plants produced the corresponding amplicon for RM5749 (linked marker for heat tolerance in the parental cross Uma x N22) and also for RM9, RM201, RM208, RM225, RM242, RM495, RM3586, RM6100, RM6836, and RM26212, corresponding to the heat tolerant parent N22. Genomic analysis revealed 64% recovery of the Uma genome in seven F4 plants, with maximum genomic regions of Uma on the chromosomes 3 and 5. These promising F4 plants could be forwarded to generate stable and high yielding heat tolerant rice varieties. The identified markers could be used for linkage analysis and QTL mapping in future.

The present study was carried out to assess the genetic parameters and divergence in 38 rice genotypes for important yield and grain quality traits. Phenotypic coefficient of variation (PCV) exceeded genotypic coefficient of variation (GCV) for all the traits taken for the study, while high heritability was recorded for all the traits, except kernel length to breadth ratio and grain iron content. The trait number of grains per panicle exhibited high heritability (91.00%) and high genetic advance as a percentage of mean suggesting simple selection may be followed to improve the traits. Cluster analysis grouped the genotypes into seven clusters. The highest inter-cluster distance was observed between clusters VII and IV (537.17). Five genotypes excelled in grain yield, ten genotypes for grain zinc content and one genotype for grain iron content over the check variety Rajendra Bhagwati. Despite high variability in grain zinc and iron content, no genotype surpassed the check variety for all three crucial attributes i.e. grain yield, grain zinc and iron content. The experimental material’s variability for grain nutrient status suggests their potential use in biofortification programs.

Development of rice genotypes possessing high yielding potential; with increased grain iron content is the need of the hour to tackle hidden hunger. Considering the above said fact, genetical analysis was conducted in six improved cultivars along with 15 potential crosses thereof. Analysis of variance for combining ability revealed significant differences in GCA and SCA variances for grain yield as well as for iron and zinc content, indicating the possibility of realization of development of iron fortified varieties with higher yielding potential. The preponderance of additive gene action for these two important characters i.e., iron and zinc content indicate that selection will be highly rewarding for genetic improvement pertaining to these two traits. The genotype Gouri was found to be very good combiner for both grain yield (0.93) and iron content of grain (2.04). Similarly, genotype Sebati was found as a very good combiner for both grain yield (0.13) and zinc content of grain (0.65). Some of the superior crosses identified concerning both grain yield and grain iron content were Birupa / Pradeep, Sebati / Gouri, Sebati / Pratap, Gouri / Pradeep and Pratap / Pradeep. Hence, these specific crosses can be used in further breeding programme for the improvement of both grain yield as well as grain iron content. The crosses viz., Bhanja / Pratap and Bhanja / Sebati were found to be superior crosses for both grain yield and grain zinc content.

The leading target domain in lowland areas is improving the tolerance for anaerobic germination and submergence, especially in direct-seeded rice (DSR). The present study identified elite genotypes with tolerance for anaerobic germination and submergence among 25 diverse rice genotypes. This study adopted four experimental conditions (three in the lab and one in the field): anaerobic germination in water, anaerobic germination with soil and water, submergence condition and direct seeded rice in the field. The recorded traits showed significant variation under all four stresses. Chitiraikar performed well in anaerobic germination and DSR experiments. CO55 registered the highest trait value of seedling height and early vegetative vigour in the anaerobic experiment with water. Aanaikomban, Karunguruvai, Karuppukavuni and Chitiraikar outperformed other genotypes in most of the above experimental conditions. Thus, choosing lines based on germination percentage, early seedling vigour, elongation index and seedling survival rate can increase tolerance for anaerobic germination and submergence conditions in the lab and DSR method. Among all the experiments conducted, anaerobic germination with soil and water and the DSR method was found to be reliable for screening a large population.

Rice variety differentiation was based on morphological descriptors (DUS) before the advent of genomic and proteomic technology. DNA fingerprinting is becoming an important molecular marker approach because of its wide application in varietal protection, classification, and conflict settlement. In the present study, genetic diversity and variability among the 11 rice varieties of Manipur at the molecular level was studied using 42 SSR markers. The genotypic data of the SSR markers revealed four sub-populations. Cluster analysis indicated the close similarity between RC Maniphou 12 and RC Maniphou 15. To create a DNA fingerprinting database for 11 rice varieties, three separate multiplex PCR systems using different combinations of 11 polymorphic SSR markers based on amplicon size were successfully developed . These were able to distinguish the distinctness of all the eleven released rice varieties.

The knowledge of functionally characterized genes and linked markers that govern grain yield and its related traits were used to unravel the markers/genes that associate with diversity of yield traits in a panel 30 novel rice genotypes comprising of indica, japonica, aromatic, landraces, interspecific crosses (O.glaberrima/O.sativa) etc. The ANOVA showed significant differences (P=

Multi-environment yield trials and multi-trait stability analyses are essential to identify the superior genotype. The aim of this research was to assess the adaptation and stability of rice genotypes using additive main effect and multiplicative interaction (AMMI) and genotype plus genotype by environment (GGE) biplot analysis and multi-trait stability index (MTSI). In this study, 20 rice genotypes were evaluated for three seasons at the same location during 2020-21. Based on AMMI analysis, the genotypes G22 (Vandana), G32 (IC-0098989), G34 (IC-0135769), G60 (ADT 36), G61 (ADT 37), and G64 (ADT 45) were found to have high yield and were more stable. GGE analysis revealed that the high-yielding and stable genotypes were G22 (Vandana), G34 (IC-0135769), G60 (ADT 36), and G64 (ADT 45). The genotypes G65 (ADT 48), G60 (ADT 36), G38 (IC-0135529), and G33 (IC-0124198) were observed to be stable based on the Multi Trait Stability Index (MTSI). Based on the above, G60 (ADT 36) could be concluded as stable across all seasons, not only based on yield but also other important agronomic traits. [ABSTRACT FROM AUTHOR]

Combining ability, along with heterosis was elucidated for nine yield attributing and 10 grain quality traits in a set of 40 rice hybrid combinations derived from 13 parents using Line × Tester mating approach. The analysis of combining ability unveiled significant GCA and SCA variances, highlighting the importance of both additive and non-additive genetic components. The ratio of dominant genetic variance to additive genetic variance exceeded unity, indicating the prevalence of non-additive gene action in governing the inheritance of all examined traits. The parental line CO 55 and the testers IC 457996 and IC 208262 were recognized as good combiners for the majority of yield-related and grain-quality traits. Regarding per se performance, heterosis, and sca effects, the crosses CO 55 × IC 457996, ADT 54 × IC 115439 and ADT 54 × IC 115439 were found promising. Consequently, these combinations could be exploited for recombination breeding aimed at developing early maturing, high-yielding fine-grain rice varieties with market acceptance.

Rice grain width is intricately governed by multiple aspects of grain development, such as cell division and expansion, thereby affecting overall grain morphology. Several key genes were identified and studied for their role in regulating grain width. OsSPL16/GW8 is a positive regulator of grain width by boosting grain weight, a major determinant of grain yield. The GW8 mRNA transcripts are cleaved by miR156, leading to reduced gene expression. In this study, we employed the CRISPR/Cas9 system to generate gw8 mutants with a disrupted GW8-miR156 binding site to enhance both grain morphology and yield in the ASD16 rice genetic background. Agrobacterium-mediated rice genetic transformation resulted in the generation of 25 putative gw8 mutants. Sanger sequencing revealed the presence of mutations within and outside the GW8-miR156 module. Notably, plants harboring mutations disrupting the GW8-miR156 module exhibited an altered grain morphology with awn and poor grain set. Further research is needed to unravel the pleiotropic effects associated with the GW8-miR156 module in rice.

Rice (Oryza sativa L.) stands as a important cereal sustaining over half of the world’s population. This study delves into the challenges confronting breeders in the realm of crop improvement, specifically focusing on the intricate task of designing an ideotype—a genotype amalgamating diverse attributes for optimal performance. Traditional methodologies, exemplified by the Smith–Hazel (SH) index, grapple with issues such as multicollinearity and the complexities of economic weighting decisions. In response to these challenges, the Multi-Trait Genotype–Ideotype Distance Index (MGIDI), conceptualized by Olivoto and Nardino (2021), emerges as a ground breaking approach. Principal Component Analysis (PCA) aids in the reduction of trait dimensionality, revealing four key factors that collectively contribute to 79.444% of total variability. The Scree plot guides factor selection, ensuring a targeted analysis. The MGIDI index computation yields a total genetic gain of 273.025%, with specific traits like spikelet fertility and seedling dry weight exhibiting significant gains. Six high-performing rice accessions—SM227, NLR33892, MTU3626, 239(3), SMB3, and 405C3 were identified through MGIDI. These identified genotypes serve as valuable resources for developing recombinant populations, aligning with sustainable and effective crop improvement strategies. Additionally, these promising varieties exhibit strengths across various traits, offering potential for simultaneous trait improvement in future breeding programmes. The efficiency of MGIDI is highlighted through its innovative application in simultaneous trait selection, underscoring its significance across a wide range of crops.

The aim of this study was to explore the characteristics essential for a maintainer line to effectively complement the A lines in hybrid rice production. The experiment was conducted at the Regional Agricultural Research Station, Jagtial and Telangana, India during kharif, 2016 (June-October). A total of 40 genotypes were raised in Randomized Block Design (RBD) with two replications. PCA identified five principal components (PCs) with Eigen values over 1, collectively accounting for approximately 75.50% of the total variance. PC1 predominantly representing yield and related features (number of tillers per plant, panicle length, length-to-breadth ratio, grain yield per plant), while the other PCs corresponded to unique aspects like grain numbers, morphological and quantitative traits. The study also utilized biplot analysis to elucidate the relationships among these traits, revealing significant correlations and interactions crucial for rice breeding. It indicated a negative correlation between 1000 grain weight, kernel breadth, and the number of grains per panicle, while showing positive correlations among traits influencing grain yield. This method also proved assistance in identifying superior genotypes for specific traits, as exemplified by genotypes JMS18B and JMS20B excelling in grain numbers per panicle and genotype B18 standing out in grain yield and other yield-related traits. [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]

The present study involved assessment of 70 three-line hybrids obtained by crossing five CMS lines and 14 testers using line x tester mating design for combining ability and heterosis for 13 yield and grain quality traits. The Analysis of Variance identified significant difference among crosses and the ratio of GCA and SCA variances were less than unity indicating non-additive gene action for all the traits. The line COMS 24A and testers RNR 15048, WGL 32100, CBSN 504, CBSN 509, CBSN 511 and IR64 DRT were identified as best general combiners through gca effects. Among the hybrids, COMS 24A X WGL 32100, COMS 24A X CBSN 504, COMS 25A X CBSN 511, COMS 25A X CBSN 517, COMS 23A X IR64 DRT and COMS 23A X CBSN 509 demonstrated outstanding sca effects, mean and standard heterosis over CORH 3 and CORH 4. Two hybrids viz., COMS 25A X CBSN 511 and COMS 25A X RNR 15048 had medium slender grain type and hold promise for commercial exploitation in south India especially Tamil Nadu. [ABSTRACT FROM AUTHOR]

Salinity is a major abiotic stress that affects plant growth and development in rice. In this study, 37 genotypes along with 2 checks were screened for salinity at the seedling stage using hydroponics. Analysis of variance revealed a significant difference among genotypes for the recorded traits. Most studies have evaluated the salt tolerance based on the independent mean performance of traits. However, this study aimed to utilize membership function values which account for cumulative tolerance from all traits. Based on average MFV, three genotypes were classified as highly tolerant, four genotypes were classified as tolerant, 25 genotypes were classified as moderately tolerant, six genotypes were classified as susceptible, one genotype as highly susceptible. Simple linear regression analysis indicated total fresh weight is the reliable trait for salinity screening in rice at the seedling stage. Further, a multiple regression-based mathematical model was developed, which identified that a membership function-based evaluation system can be utilized for salinity tolerance grading. The identified highly tolerant and tolerant genotypes can be utilized for the improvement of salt tolerance at the seedling stage in rice.

To alleviate salt stress in rice, the role of potassium in countering the ill effects of sodium is gaining importance. Towards this, OsHAK5 a member of the high-affinity potassium transporter family was known for enhancing the intracellular potassium under reduced/low K+ availability during salt stress. The full-length cDNA of OsHAK5 was cloned and sequenced from the roots of Pokkali and cv. IR64 however, no nucleotide polymorphism detected. Interestingly, the expression of OsHAK5 in roots of salt-tolerant landrace Pokkali and salt susceptible cv. IR64 revealed a significant upregulation in the former under low K+ (1/4th) condition. Subsequent analysis of the amino acid sequence of CBL-interacting protein kinase (OsCIPK23), the upstream regulator of OsHAK5 revealed two INDELs and one of them turned out to be functionally relevant. The OsCIPK23 variant from salt-tolerant Pokkali should be favorably regulating the expression of the downstream OsHAK5 leading to an increased K+ uptake under salt stress.

Rice (Oryza sativa L.) plays a pivotal role in global food security, necessitating continuous efforts to enhance yield potential and grain quality. Mutation breeding, employing physical (electron beam) and chemical (ethyl methane sulphonate, EMS) mutagens, offers a promising avenue for creating genetic variability. This study assessed the sensitivity of rice variety ASD 16 and landrace Norungan to varying doses of electron beam (100 Gy to 500 Gy) and EMS (30 mM to 70 mM). The genotypes exhibited dose-dependent responses in germination, seedling survival, shoot and root length, seedling height, pollen fertility and spikelet fertility. The LD50 values for electron beam under in vivo and in vitro conditions were 314.24 Gy and 348.21 Gy respectively for ASD 16 and 445.07 Gy and 461.88 Gy for Norungan whereas for EMS, the LD50 values for ASD 16 were 49.17 mM and 55.37 mM; 53.53 mM and 65.12 mM for Norungan under in vivo and in vitro conditions based on probit analysis. ASD 16 showed a GR50 value of 309.02 Gy for the electron beam and 51.60 mM for EMS while Norungan exhibited a GR50 value of 538.79 Gy for electron beam and 98.71 mM for EMS. The variety, ASD 16 demonstrated higher sensitivity, proved by greater growth reduction percentages and lower lethal dose 50 (LD50) values compared to landrace Norungan. Electron beam treatments induce significant reductions in various growth traits, underlining the potential deleterious effects at higher doses. EMS, as a chemical mutagen, also impacted germination and growth characteristics. Both mutagens affected pollen and spikelet fertility with notable influence on yield contributing traits. This finding emphasizes the significance of precise dosage selection in mutation breeding to induce desirable traits and maintaining complete plant viability and productivity. Understanding genotype-specific responses is crucial for successful mutation breeding programmes. Overall, this study offers valuable insights into the application of electron beam and EMS mutagenesis in rice, contributing to the optimization of mutagenic protocols for crop improvement.

Fifty selected rice genotypes including two checks were evaluated during Kharif, 2022-23 for genetic variability, heritability and genetic advance as per cent of mean for 16 yield and its attributing traits along with six nutritional parameters in Ranadevi Post Graduate Research Farm, M. S. Swaminathan school of Agriculture, Centurion University of Technology and Management. Analysis of variance indicated highly significant differences among the 50 genotypes studied indicating that substantial variability is present among the genotypes. Total grains panicle-1, filled grains panicle-1, test weight, grain yield plant-1, straw yield plant-1, biological yield plant-1, protein content and mineral contents of Fe, Zn, Cu and Mn exhibited high genotypic coefficient of variation (GCV) and phenotypic coefficient of variation (PCV) suggesting that there is considerable genetic variability among the genotypes studied for the evaluated traits. All 22 traits showed a high heritability (broad sense) coupled with high genetic advance as percent of mean except panicle length, spikelet fertility, harvest index and carbohydrate content, which recorded moderate genetic advance as percent of mean, indicating that additive gene action operates for these traits and has potential for improvement through direct selection methods.

Salinity is a major abiotic stress that affects plant growth and development in rice. In this study, 37 genotypes along with 2 checks were screened for salinity at the seedling stage using hydroponics. Analysis of variance revealed a significant difference among genotypes for the recorded traits. Most studies have evaluated the salt tolerance based on the independent mean performance of traits. However, this study aimed to utilize membership function values which account for cumulative tolerance from all traits. Based on average MFV, three genotypes were classified as highly tolerant, four genotypes were classified as tolerant, 25 genotypes were classified as moderately tolerant, six genotypes were classified as susceptible, one genotype as highly susceptible. Simple linear regression analysis indicated total fresh weight is the reliable trait for salinity screening in rice at the seedling stage. Further, a multiple regression-based mathematical model was developed, which identified that a membership function-based evaluation system can be utilized for salinity tolerance grading. The identified highly tolerant and tolerant genotypes can be utilized for the improvement of salt tolerance at the seedling stage in rice. [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.