1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)

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    Yield prediction of kharif rice (Oryza sativa L.) in Kerala by various crop weather models
    (Department of Agricultural Meteorology, College of Agriculture,Vellanikkara, 2025-02-04) Chandana B Jyothi.
    Rice is a staple crop in Kerala, but its production faces challenges from adverse weather and climate changes, leading to yield fluctuations. Accurate yield forecasts are vital for farmers, policymakers, and exporters to ensure efficient resource allocation and strategic planning. Tools like DSSAT and Info-Crop simulate rice growth for yield prediction, while statistical models like Artificial Neural Networks (ANN) and Stepwise Multiple Linear Regression (SMLR) offer additional predictive capabilities. The present study “Yield prediction of kharif rice (Oryza sativa L.) in Kerala by various crop weather models” is aimed to predict kharif rice yield in different districts of Kerala using statistical and crop simulation models and compare above yield prediction models. Short duration variety, Jyothi and Manu Ratna were raised at Agricultural Research Station, Mannuthy, Kerala Agricultural University, Thrissur. The split plot design was used with five dates of planting (June 5th, June 20th, July 5th, July 20th and August 5th) as main plot treatments and two varieties as subplot treatments, with four replications. Various observations like weather, phenological, biometric, computed parameters, yield and yield attributes had been recorded to study the crop weather relationship. The data analysis has been done by using SPSS software and it was found that with increase in the maximum temperature (°C), minimum temperature (°C), temperature range (°C), bright sunshine hour (hrs) and rate of evaporation (mm) has reduced the crop duration, while amount of rainfall (mm), number of rainy days, forenoon and afternoon relative humidity (%) has positively influenced with the crop duration. A significant variation in the biometric and computed observations was also obtained. Plant height were found to be higher in Manu Ratna, when compared to Jyothi. Dry matter accumulation was higher in Manu Ratna during 75 DAP and there was no significant difference between varieties in the later stages. Both plant height and dry matter accumulation had significant variations among different planting dates. Leaf area index did not show any significant variation among varieties and date of planting. In Jyothi highest grain yield was found in July 5th planting, while in Manu Ratna July 20th planting was found to be higher. Maximum temperature in the P5 and P6 stage had a negative influence on the yield. Wind speed also showed a negative correlation with yield in the later stages. The genetic coefficients influencing the growth and yield of rice in the CERES- DSSAT model and Info-Crop model were calibrated to achieve the optimum agreement between observed and simulated values. Predicted yield of both rice varieties, Jyothi and Manu Ratna, under different planting dates were reasonably close to the observed values. These observations indicate that the DSSAT model generally performs better in districts like Thrissur, Pathanamthitta and Kollam, while the Info Crop model excels in Thrissur. However, both models require improvements in districts like Kottayam, Kasaragod and Alappuzha to enhance prediction accuracy. A dataset of 105 yield records (2013–2022) and weather indices was used for calibration. Stepwise regression identified the best statistical model having highest R2 for yield prediction. The ANN model, trained using the ‘caret’ package in R Studio, utilized 12 input variables. The dataset was split into 80% training and 20% testing. The developed model predicted 2023 yields for 12 districts. For comparing the accuracy of these models for districts of Kerala, MAPE and MAE were calculated. The data highlights the district-wise performance of both models, showing the ANN model generally outperforms the SMLR model in terms of accuracy, particularly in Kasaragod and Ernakulam. Yield prediction is crucial for ensuring food security, optimizing resource use and guiding agricultural planning and policy decisions. In conclusion, the comparison of crop-weather models for rice yield prediction reveals distinct strengths among the approaches. Machine learning models demonstrate superior accuracy with extensive datasets. A hybrid approach combining these models can optimize rice yield predictions, supporting sustainable and resilient rice farming systems.
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    Efficacy of foliar sprays in alleviating heat stress in rice (Oryza sativa L.) during different growth periods
    (Department of Agricultural Meteorology, College of Agriculture , Vellanikkara, 2025-01-28) Devanshi Maharana; Ajithkumar, B.
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    Phenotyping and marker assisted screening of rice (Oryza sativa L.) germplasm for sheath blight(Rhizoctonia solani kuhn) resistance
    (Department of Genetics and Plant Breeding, College of Agriculture,Vellayani, 2024-12-16) Bandela Chandana.; Adheena Ram
    The study entitled “Phenotyping and marker assisted screening of rice (Oryza sativa L.) germplasm for sheath blight (Rhizoctonia solani Kühn) resistance” was carried out at the Department of Genetics and Plant Breeding, College of Agriculture, Vellayani during 2022 to 2024 with an objective of artificial screening and identification of rice genotypes for sheath blight resistance and validation with molecular markers linked to reported QTLs of sheath blight resistance. The phenotypic screening for sheath blight resistance was conducted, using thirty rice genotypes and different biometric, biochemical and computed parameters were analysed. Analysis of variance revealed significant difference for all the biometric characters except number of tillers per plant. All the biochemical parameters such as peroxidise, catalase, polyphenol oxidase and phenylalanine ammonialyase showed an increase in biochemical activity in genotypes under stress but only phenylalanine ammonialyase showed significant difference among them. Studies on phenotypic coefficient of variation and genotypic coefficient of variation revealed high variation for lesion height, number of grains per panicle, number of unfilled grains per panicle and grain yield per plant. In general, PCV values were higher than GCV for all characters indicating the influence of environment towards total variance. High heritability with high genetic advance was noticed for days to heading, days to 50 per cent flowering, number of productive tillers per plant, stem thickness, panicle length, number of grains per panicle, thousand grain weight and grain yield per plant indicating the influence of additive gene action and suitability of these traits for selection. Panicle length, days to 50 per cent flowering, number of tillers per plant and thousand grain weight had significant positive correlation with grain yield per plant where as plant height and lesion height were negatively correlated with grain yield per plant. The days to 50 per cent flowering has a strong positive direct effect on grain yield per plant and days to heading through the days to 50 per cent flowering showed a strong indirect effect on grain yield per plant. Based on genetic divergence analysis 30 genotypes were grouped into four clusters. Cluster III with nine genotypes was the largest followed by cluster I (eight genotypes) and cluster IV (seven genotypes). The clusters II had the least number of genotypes (six). Based on the inter-cluster distances, clusters III and IV had the lowest divergence (6.50) while clusters I and IV recorded the highest divergence (11.41). The highest intra cluster distance was noticed among genotypes of cluster IV (6.32) and the lowest was noticed among genotypes of cluster II (5.36). The genotypes Remanika, Chenthadi, Krishnanjana, Panchami, Karishma, Revathy, White Ponni and Bhadra in the cluster I had the highest mean value for days to heading, days to 50 per cent flowering, number of tillers per plant, number of productive tillers per plant, stem thickness, panicle length, number of grains per panicle, thousand grain weight and grain yield per plant. Based on scoring of sheath blight severity and percentage disease index the genotypes Gouri, Chenthadi, Krishnanjana, Panchami, White ponni, VYT-1, Chenkayama and Onam were found to be resistant for sheath blight. Moderate resistance to sheath blight was shown by the cultivars Karishma, Revathy, Bhagya, VYT-7, Karuna, Sreyas, Prathyasa, Karthika, Chettivirippu, Makom, Uma and Bhadra. The 15 SSR markers linked to the reported sheath blight QTLs used for validation were polymorphic with the PIC value ranging between 0.17 (RM16200) and 0.63 (RM71). RM105 linked to qShB9-1 had the maximum number of alleles (4). The cluster analysis for marker data grouped the rice genotypes into two major clusters with cluster II having the highest number of genotypes. The high yielding rice genotypes Chenthadi and Krishnanjana were identified as resistant to sheath blight based on phenotypic and genotypic data. These genotypes can be used as donors for sheath blight resistance in future breeding programmes.
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    Effect of elevated CO2 on iron transporter gene expression and iron dynamics in rice (Oryza sativa L.)
    (Department of Plant Biotechnology, College of Agriculture , Vellayani, 2022-10-25) Maneesh ,M; Manju,R V
    The present programme entitled “Effect of elevated CO2 on iron transporter gene expression and iron dynamics in rice (Oryza sativa L.)” was carried out in the Department of Plant Biotechnology and Department of Plant Physiology, College of Agriculture, Vellayani, during the year 2021-2022 with the objective of evaluating the effect eCO2 condition on expression of iron transporter genes OsIRT1 and OsIRT2 and mechanism of iron transport in rice. By using in-silico methods, additional characteristics of the two proteins were investigated The experiment was laid out in CRD with two treatments and 15 replications. Plants were maintained under open field condition (390 ppm) and under the elevated CO2 of 500ppm in the Open Top Chamber (OTC) facility at the Department of Plant Physiology. The extent of variation in growth, physiological, and biochemical parameters as well as parameters related to Fe dynamics were assessed in rice variety Uma (MO16). The expression analyses of two genes were done using real time PCR. In the present study, larger numbers of tillers, productive tillers, dry matter buildup, root weight, and straw production were seen under 500 ppm CO2 exposure than under open field conditions. OTC condition resulted in higher total chlorophyll content, photosynthetic rate, and total reducing sugars while the rate of transpiration, stomatal conductance, and total soluble protein content decreased in the plants grown inside OTC. Physiological and biochemical parameters were recorded at the active tillering stage. The shoot, root, and grains of plants maintained in both environments were examined for parameters linked to iron dynamics. Additionally, soil samples from the two experimental settings were taken, and their Fe status was examined. The dry matter accumulation, number of tillers, number productive tillers and root weight increased significantly when grown inside the OTC with eCO2. The grain yield and straw yield increased by 59.4% and 36.2% respectively upon exposure to eCO2 compared to control plants which were grown in open field. Photosynthetic parameters like chlorophyll content and photosynthetic rate were found significantly increased under eCO2 condition leading to significantly higher total reducing sugar content at active tillering stage. The stomatal conductance, transpiration rate and total soluble protein content were reduced by eCO2 at the active tillering stage. The iron transporter genes, OsIRT1 and OsIRT2 were down regulated under eCO2 condition. Iron content in roots, straw and grains of eCO2 exposed plants were reduced by 10.3%, 24.5% and 37.5% respectively. The physicochemical analyses (Expasy protparam) of the proteins OsIRT1 and OsIRT2 revealed that they contain 374 and 370 amino acids respectively. The instability indices of OsIRT1 and OsIRT2 proteins were 41 and 45 respectively indicating that both these proteins are unstable. The phylogenetic analysis of OsIRT1 using MEGA X showed maximum similarity with IRT1-like protein Panicum hallii. OsIRT2 had maximum similarity with IRT1-like protein Hordeum vulgare subsp. vulgare. The Fe metal ion binding sites on OsIRT1 and OsIRT2 were projected to have a total of 21 amino acid residues and 24 amino acid residues respectively (MIB tool). Bioinformatics tools were used to predict the physicochemical parameters (Expsay protparam, secondary structure (PSIPRED v 2.0), and 3D homology structure (iTASSER) which was validated using Ramachanadran plot. In silico predictions done on Metal binding site, docking (MIB) and visualization (Pymol) revealed the characteristics of iron binding sites of these proteins. Elevated CO2 levels had a positive impact on the overall growth and yield performance of the rice variety Uma by improving the radiation interception and photosynthetic efficiency, but had an adverse effect on grain quality with reduced iron content. This can be due to modified absorption, translocation and remobilization pattern of Fe under eCO2 condition and the down-regulation of the Fe transporter genes OsIRT1 and OsIRT2 by eCO2. The predictions on the properties of the proteins OsIRT1 and OsIRT2 done through in silico means could be usedas a foundation for future research on their role in regulating the levels of micronutrients in crop plants. The influence of eCO2 on morphological, physiological, and molecular factors in rice could be utilised for developing climate change mitigation strategies.
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    Zinc fertifortification of rice (Oryza sativa L.) cultivars
    (Department of Agronomy, College of Agriculture , Vellayani, 2021-10-10) Namitha Krishna; Jacob, D
    An experiment entitled “Zinc fertifortification of rice (Oryza sativa L.) cultivars” was conducted during 2019-2021 at College of Agriculture, Vellayani. The main objective of the study was to enhance the grain Zn content of rice cultivars through Zn fertilization. The field experiment was carried out in farmer’s field at Southern Coastal Plain (AEU 1) during the kharif season 2020-21. The field experiment was laid out in Randomised Block Design (with two factors) and was replicated thrice. The treatment combinations included four medium duration rice varieties viz., Uma (V1), Pournami (V2), Gouri (V3), DRR Dhan 45 (V4) and four foliar Zn fertilization viz., without ZnSO4 (F1), ZnSO4 @ 0.1 per cent at maximum tillering (MT) and milk (M) stages (F2), ZnSO4 @ 0.5 per cent at MT and M stages (F3), ZnSO4 @ 1.0 per cent at MT and M stages (F4). The growth parameters such as plant height, number of tillers per hill and dry matter production at panicle initiation and harvest stages were significantly influenced by foliar Zn fertilization. ZnSO4 @ 1.0 per cent (F4) recorded taller plants (80.5 and 113 cm), higher tillers per hill (20.2 and 15.7 nos.) and higher dry matter production (12.0 and 28.9 g hill-1 ) at panicle initiation and harvest stages respectively, and were comparable with ZnSO4 @ 0.5 per cent (F3). Higher leaf area index 3.87 recorded at panicle initiation stage in ZnSO4 @ 1.0 per cent (F4) was comparable to ZnSO4 @ 0.5 per cent (F3). Higher spikelets per panicle (120 nos.) and filled grains per panicle (78.0 nos.) recorded in Uma (V1) were statistically similar to Pournami (V2). Sterility per cent (35.2) and thousand grain weight (25.6 g) recorded in Uma (V1) was higher and comparable to DRR Dhan 45 (V4). ZnSO4 @ 1.0 per cent (F4) recorded higher values for yield attributes such as productive tillers per square meter (459 nos.), grain weight per panicle (2.37 g), spikelets per panicle (119 nos.), filled grains per panicle (83.3 nos.), which were comparable to ZnSO4 @ 0.5 per cent (F3). Foliar fertilization with ZnSO4 @ 1.0 per cent (F4) produced higher grain 4.65 t ha-1 and straw 4.85 t ha-1 yield, and was comparable to ZnSO4 @ 0.5 per cent (F3) which recorded grain and straw yield of 4.62 and 4.81 t ha-1 respectively. The increase in grain and straw yield due to ZnSO4 @ 0.5 per cent (F3) were 12.1 to 11.1 per cent respectively over the control plot (without ZnSO4 ) (F1). Biofortified rice variety DRR Dhan 45 (V4) recorded significantly higher Zn content in rough rice (28.6 mg kg-1 ) and its milled fractions viz., brown rice (33.7 mg kg1 ), white rice (25.3 mg kg-1 ), rice husk (51.1 mg kg -1 ) and rice bran (97.7 mg kg-1 ). Significantly higher Zn content was recorded in boiled rice (16.6 mg kg-1 ) and decanted rice water (19.9 mg kg-1 ) of variety DRR Dhan 45 (V4). As a variety with high Zn content in rough rice and its milled fractions, Gouri (V3) was second only to DRR Dhan 45 (V4). Among non biofortified rice varieties, lower Zn content in rough rice (18.8 mg kg-1 ), brown rice (16.3 mg kg-1 ), white rice (12.2 mg kg-1 ), rice husk (24.7 mg kg -1 ) and rice bran (47.1 mg kg-1 ) was recorded in Uma (V1) and was comparable with Pournami (V2). Lower Zn content recorded in boiled rice (8.0 mg kg-1 ) and decanted rice water (9.6 mg kg-1 ) of variety Uma (V1) was comparable to Pournami (V2). Foliar fertilization with ZnSO4 @ 1.0 per cent (F4) could increase Zn content in rough rice (24.0 mg kg-1 ), brown rice (28.3 mg kg-1 ), white rice (21.2 mg kg-1 ), rice bran (82.0 mg kg-1 ), boiled rice (13.9 mg kg-1 ), decanted rice water (16.7 mg kg-1 ). However, it was comparable with ZnSO4 @ 0.5 per cent (F3) which recorded Zn content of 22.0, 26.0, 19.5, 75.3, 12.8 and 15.4 mg kg-1 in rough rice, brown rice, white rice, rice bran, boiled rice, and decanted rice water respectively. Zn content in rice husk (54.6 mg kg-1 ) was significantly increased by ZnSO4 @ 1.0 per cent (F4). NPK content of grain and straw was enhanced by ZnSO4 @ 1.0 per cent (F4) resulting in higher plant uptake of NPK, which was comparable with ZnSO4 @ 0.5 per cent (F3). Varieties DRR Dhan 45 (V4) and Uma (V1) resulted in Zn biofortification recovery efficiency (ZnBRE) of 3.26 and 1.39 per cent respectively. Significantly higher ZnBRE efficiency of 3.14 per cent was recorded in ZnSO4 @ 0.5 per cent (F3), ZnSO4 @ 1.0 per cent (F4) recorded ZnBRE of 1.99 per cent. Economic analysis revealed highest gross income (₹ 140474 ha-1 ), net income (₹ 46900 ha-1 ) and benefit: cost ratio (1.50) in treatment combination non biofortified variety Uma foliar fertilized with ZnSO4 @ 0.5 per cent (v1f3). Increasing the foliar fertilized ZnSO4 from 0.5 per cent (v1f3) to 1.0 per cent (v1f4) in variety Uma could bring about only negligible increase in gross income, net income and benefit: cost ratio by 0.5 per cent, 1.1 per cent and 0.3 per cent respectively. Biofortified variety DRR Dhan 45 foliar fertilized with ZnSO4 @ 0.5 per cent (v4f3) recorded gross income, net income and benefit: cost ratio of ₹ 135753 ha-1 , ₹ 42019 ha-1 and 1.45 respectively. Increasing foliar fertilization of ZnSO4 from 0.5 per cent to 1.0 per cent resulted in an increment in gross income, net income and benefit: cost ratio by 1.2 per cent, 3.5 per cent and 0.7 per cent respectively. The present study indicated that foliar fertilization with ZnSO4 @ 0.5 per cent at maximum tillering and milk stages as an economically viable option to significantly increase grain and straw yield of rice, and also to increase Zn content in rough rice and its milled fractions, resulting in increased Zn content in boiled rice and decanted rice water, irrespective of the rice variety.
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    Evaluation of plant growth promoting rhizobacteria for pokkali rice
    (Department of Agricultural Microbiology, College of Agriculture,Vellanikkara, 2023-02-17) Bony Cyriac.; Surendra Gopal, K
    Pokkali rice farming is a time-honoured, environmentally beneficial, traditional and organic method of growing rice. Neither chemical fertilizers nor plant protection agents are used on the crop in this conventional rice farming technique. The present study was undertaken to evaluate a native plant growth promoting rhizobacteria (PGPR) consortia with an objective to screen PGPR for functional efficiency under in vitro and evaluate for plant growth promotion in Pokkali rice. Isolation, characterization and screening of plant growth promoting rhizobacteria such as nitrogen fixers, phosphate solubilizers, potassium solubilizers, fluorescent pseudomonads and Bacillus sp. were carried out from three Pokkali rice growing regions of Ernakulam district (Vytilla, Varapuzha and Kadamakudy). Maximum population of 4 x 103 , 4.66 x 103 and 16.67 x 103 cfu per g of soil were recorded for nitrogen fixers, phosphate solubilizers and Bacillus sp. respectively and fluorescent pseudomonads and potassium solubilizers were absent. A total of 25 predominant isolates were obtained of which 17 isolates belonged to Bacillus sp. and remaining 4 isolates each were nitrogen fixers and phosphate solubilizers. Cultural, morphological and biochemical characters of all the 25 isolates of rhizobacteria showed varied colony morphology and Gram reaction. These isolates were evaluated under in vitro for plant growth promotion activities (production of indole acetic acid, nitrogen fixation, phosphate and potassium solubilization), antagonistic mechanisms (NH3, HCN and siderophore production) and its activities against Xanthomonas oryzae. Quantity of IAA produced by rhizobacterial isolates ranged from 0.46 to 31.27 μg ml-1. Quantity of nitrogen fixed and phosphate solubilized by rhizobacterial isolates varied from 5.72 to 25.21 mg of N g-1 sucrose utilized and 1.98 to 53.19 μg ml-1, respectively. There was no significant difference between potassium solubilized by isolates. Among the rhizobacterial isolates all Bacillus sp. isolates and two isolates each of nitrogen fixers and phosphate solubilizers were found positive for ammonia production. In case of screening of isolates for siderophore production, isolate VYP1 produced moderate orange halo zone on CAS agar media. Isolates VYN1, VYN2, VRB1 and VRB3 recorded poor siderophore activity. Remaining all isolates in the study screened negative for siderophore production. All isolates in the study were found negative for HCN production. Antagonistic activities of isolates to inhibit the rice pathogen Xanthomonas oryzae was evaluated and twenty one isolates screened exhibited antagonistic response against pathogen in which Bacillus isolates KDB4 and KDB5 exhibited excellent antagonism against pathogen. Based on the plant growth promotion activities and antagonistic activities, four most efficient isolates each of nitrogen fixers, phosphate solubilizers and Bacillus sp. were selected for salinity tolerance studies. Among the isolates, nitrogen fixers and Bacillus sp. exhibited maximum salinity tolerance of 12% whereas, phosphate solubilizers exhibited salinity tolerance up to 4% salt concentration. After salinity tolerance studies, three most tolerant nitrogen fixers (VYN2, KDN1 and KDN2), phosphate solubilizers (VYP1, VRP1 and KDP1), and Bacillus sp. (VYB3, VYB6 and KDB1) were selected for compatibility studies. Three most promising PGPR based consortia, PGPR consortia1 (KDN2 + KDP1 + VYB6), PGPR consortia-2 (KDN1 + KDP1 + VYB6) and PGPR consortia-3 (KDN2 + VYP1 + KDB1) were formulated. The three most promising consortia were evaluated under pot culture experiment, along with KAU commercial formulation (PGPR Mix-1) and Organic Package of Practices Recommendations of KAU (2017), at RRS, Vytilla, with Pokkali rice (variety Vytilla-6) as the test crop. All the three native PGPR consortia (T1, T2 and T3) exhibited significant increase in plant height and plants treated with T1 (PGPR consortia 1- KDN2 + KDP1 + VYB6) and T2 (PGPR consortia 2 - KDN1 + KDP1 + VYB6) recorded significantly higher results. Higher number of grains per panicle, grain yield (g per pot) and theoretical grain yield (kg ha-1) were observed in PGPR consortia 1 consisting of isolates KDN2 (N-fixer) + KDP1 (P- solubilizer) + VYB6 (Bacillus sp.). Significantly higher test weight of seeds were observed in T1, T2 and T3 inoculated with native PGPR consortia compared to other treatments. However, the treatments did not have any significant effect on number of tillers, number of panicles per plant and the percentage of chaffy grains produced. The present study indicated that saline tolerant PGPR consortia-1 consisting of Enterobacter cloacae strain KDN2 (N-fixer) + Bacillus subtilis strain KDP1 (Psolubilizer) + Bacillus altitudinis strain VYB1 (Bacillus sp.) was the most promising biofertilizer in enhancing the production of Pokkali rice of Kerala. However, further evaluation of the most promising consortia needs to be done under field conditions to confirm the results.
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    Somatic embryogenesis in rice (Oryza sativa L.)
    (Department of Plant Breeding and Genetics, College of Agriculture,Vellanikkara, 2023-05-17) Ardra, K S.; Sindhumole, P
    Rice is the staple food for more than half of the world’s population, but over time the yields have plateaued and there are higher incidences of pest and diseases. This problem can be tackled by combining biotechnological tools with crop improvement methods. Genetic modifications can be used to improve yield, tolerance to pest and disease and even incorporate climate resilience in the crop, which is the need of the hour for the rapidly growing population. For the application of genetic transformation techniques, standardised in vitro regeneration protocols are necessary and among the many techniques, somatic embryogenesis is a promising technique as it produces large number of plantlets. Somatic embryogenesis is a type of asexual reproduction whereby somatic or gametic cells are induced to form somatic embryos under favorable in vitro conditions by exploiting the cellular totipotency of plant cells to form entire plantlets. Thus, this study was conducted to standardise the protocol for somatic embryogenesis and regeneration in two rice varieties, Jyothi (PTB 39) and Nagina 22 (N22). Jyothi is a very popular, red and long bold grained rice variety cultivated predominantly in the Kole and Kuttanad regions of Kerala. N22 is a deep rooted aus type Indian rice variety, well known for its high tolerance to drought and heat. The mature seeds and leaves of these varieties were used as explants in this research programme. Experiment 1 involved studies to standardise the medium for callus induction and somatic embryogenesis. In the preliminary study, the effect of medium (MS and N6), carbon source (sucrose and maltose) and 2,4-D at different levels (0, 1, 2, and 3 µM) were observed, and the treatment combination MS + 2,4-D (3 µM) with maltose performed the best among the sixteen treatments in both varieties. The effect of medium with 2,4-D and BAP on callus induction from leaf explants was studied and none of the varieties responded to the treatments. When the effect of 2,4-D and kinetin on somatic embryogenesis was investigated, the somatic embryogenesis per cent was higher in the treatment combination MS + 2,4-D (0.4 µM) + Kinetin (1.5 µM) in Jyothi (80%) and the treatments MS + 2,4-D (0.4 µM) + Kinetin (1.5 µM) and MS + 2,4-D (0.4 µM) + Kinetin (2 µM) in N22 (85.71%). Moreover, both varieties exhibited some rhizogenesis from the callus, which reduced the capacity of the calli for somatic embryogenesis as well as regeneration. During this study, the seeds germinated regardless of treatment and the germination per cent varied from 75 to 97.22 per cent in Jyothi while it ranged from 58.33 to 100 per cent in N22. Regarding the callus induction frequency (CIF), 2,4-D (3 µM) in MS medium containing maltose exhibited the highest CIF in both the varieties (N22 with 100 per cent CIF and Jyothi with 69.44 per cent CIF). The callus was developed from the scutellar region of the seeds. Callus induction required six to seven days in both the varieties. It was observed that three week old calli started forming somatic embryos when sub cultured on MS medium supplemented with 2,4-D (0 and 0.4 µM) and Kinetin (0, 0.4, 1, 1.5 and 2 µM), and incubated in dark. Embryogeneic calli per cent was highest in treatment MS + 2,4-D (0.4 µM) + Kinetin (0.4 µM) in Jyothi (87.50%) and in treatments MS + 2,4-D (0.4 µM) + Kinetin (1.5 µM) and MS + 2,4-D (0.4 µM) + Kinetin (2 µM) in N22 (85.71%). Non-embryogenic calli formation was the lowest in the treatment MS +2,4-D (0.4 µM) + Kinetin (0.4 µM) for Jyothi (12.50%), while MS +2,4-D (0.4 µM) + Kinetin (1.5 µM) and MS + 2,4-D (0.4 µM) + Kinetin (2 µM) for N22 (14.29 %). For the development of somatic embryos into plantlets, the embryogenic calli were sub cultured on medium with NAA and BAP and incubated in 16 hours light and 8 hours dark conditions. Embryoid formation was observed in both varieties within two weeks, but not all the embryoids developed into plantlets due to degeneration. In Experiment 2 for regeneration studies, N22 formed two plantlets from somatic embryos in the treatment combinations MS + NAA (0.2 µM) + BAP (0.8 µM) and MS + NAA (1 µM) + BAP (3.5 µM) whereas, Jyothi required the addition of maltose (20 and 30 g/l) and sorbitol (25 and 30 g/l) in the medium for embryoid development. Seventeen embryoids formed in Jyothi, but only three developed into plantlets in the treatment MS + NAA (1 µM) + BAP (3.5 µM) with 30 g/l each of maltose and sorbitol. Jyothi plantlets needed an average of 15.67 days for shoot initiation and 29.67 days for root initiation. In N22, the average number of days for shoot initiation and root initiation were 8.50 and 18.50 respectively. All the plants obtained from this study were green and healthy, with the characteristics of normal rice plants formed from seeds. However, these plantlets required additional time for proper root development in basal MS medium or MS medium with IBA and NAA, prior to planting out into pots. Experiment 3 entailed hardening and pot culture. The plantlets of Jyothi and N22 were first transferred to distilled water for a few days to let the leaves to unfurl and then planted in sterilised potting mixture. The plants were then kept under 16 hour photoperiod for 10 days. These plants were further hardened in a polytunnel and later grown in a rain shelter using standard agronomic practices. N22 and Jyothi plants grew with healthy leaves and formed panicles within two months but N22 exhibited poor tillering.
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    Somatic embryogenesis in rice (Oryza sativa L.)
    (Department of Plant Breeding and Genetics, College of Agriculture, Vellanikkara, 2023) Ardra, K S; Sindhumole, P
    Rice is the staple food for more than half of the world’s population, but over time the yields have plateaued and there are higher incidences of pest and diseases. This problem can be tackled by combining biotechnological tools with crop improvement methods. Genetic modifications can be used to improve yield, tolerance to pest and disease and even incorporate climate resilience in the crop, which is the need of the hour for the rapidly growing population. For the application of genetic transformation techniques, standardised in vitro regeneration protocols are necessary and among the many techniques, somatic embryogenesis is a promising technique as it produces large number of plantlets. Somatic embryogenesis is a type of asexual reproduction whereby somatic or gametic cells are induced to form somatic embryos under favorable in vitro conditions by exploiting the cellular totipotency of plant cells to form entire plantlets. Thus, this study was conducted to standardise the protocol for somatic embryogenesis and regeneration in two rice varieties, Jyothi (PTB 39) and Nagina 22 (N22). Jyothi is a very popular, red and long bold grained rice variety cultivated predominantly in the Kole and Kuttanad regions of Kerala. N22 is a deep rooted aus type Indian rice variety, well known for its high tolerance to drought and heat. The mature seeds and leaves of these varieties were used as explants in this research programme. Experiment 1 involved studies to standardise the medium for callus induction and somatic embryogenesis. In the preliminary study, the effect of medium (MS and N6), carbon source (sucrose and maltose) and 2,4-D at different levels (0, 1, 2, and 3 µM) were observed, and the treatment combination MS + 2,4-D (3 µM) with maltose performed the best among the sixteen treatments in both varieties. The effect of medium with 2,4-D and BAP on callus induction from leaf explants was studied and none of the varieties responded to the treatments. When the effect of 2,4-D and kinetin on somatic embryogenesis was investigated, the somatic embryogenesis per cent was higher in the treatment combination MS + 2,4-D (0.4 µM) + Kinetin (1.5 µM) in Jyothi (80%) and the treatments MS + 2,4-D (0.4 µM) + Kinetin (1.5 µM) and MS + 2,4-D (0.4 µM) + Kinetin (2 µM) in N22 (85.71%). Moreover, both varieties exhibited some rhizogenesis from the callus, which reduced the capacity of the calli for somatic embryogenesis as well as regeneration. During this study, the seeds germinated regardless of treatment and the germination per cent varied from 75 to 97.22 per cent in Jyothi while it ranged from 58.33 to 100 per cent in N22. Regarding the callus induction frequency (CIF), 2,4-D (3 µM) in MS medium containing maltose exhibited the highest CIF in both the varieties (N22 with 100 per cent CIF and Jyothi with 69.44 per cent CIF). The callus was developed from the scutellar region of the seeds. Callus induction required six to seven days in both the varieties. It was observed that three week old calli started forming somatic embryos when sub cultured on MS medium supplemented with 2,4-D (0 and 0.4 µM) and Kinetin (0, 0.4, 1, 1.5 and 2 µM), and incubated in dark. Embryogeneic calli per cent was highest in treatment MS + 2,4-D (0.4 µM) + Kinetin (0.4 µM) in Jyothi (87.50%) and in treatments MS + 2,4-D (0.4 µM) + Kinetin (1.5 µM) and MS + 2,4-D (0.4 µM) + Kinetin (2 µM) in N22 (85.71%). Non-embryogenic calli formation was the lowest in the treatment MS +2,4-D (0.4 µM) + Kinetin (0.4 µM) for Jyothi (12.50%), while MS +2,4-D (0.4 µM) + Kinetin (1.5 µM) and MS + 2,4-D (0.4 µM) + Kinetin (2 µM) for N22 (14.29 %). For the development of somatic embryos into plantlets, the embryogenic calli were sub cultured on medium with NAA and BAP and incubated in 16 hours light and 8 hours dark conditions. Embryoid formation was observed in both varieties within two weeks, but not all the embryoids developed into plantlets due to degeneration. In Experiment 2 for regeneration studies, N22 formed two plantlets from somatic embryos in the treatment combinations MS + NAA (0.2 µM) + BAP (0.8 µM) and MS + NAA (1 µM) + BAP (3.5 µM) whereas, Jyothi required the addition of maltose (20 and 30 g/l) and sorbitol (25 and 30 g/l) in the medium for embryoid development. Seventeen embryoids formed in Jyothi, but only three developed into plantlets in the treatment MS + NAA (1 µM) + BAP (3.5 µM) with 30 g/l each of maltose and sorbitol. Jyothi plantlets needed an average of 15.67 days for shoot initiation and 29.67 days for root initiation. In N22, the average number of days for shoot initiation and root initiation were 8.50 and 18.50 respectively. All the plants obtained from this study were green and healthy, with the characteristics of normal rice plants formed from seeds. However, these plantlets required additional time for proper root development in basal MS medium or MS medium with IBA and NAA, prior to planting out into pots. Experiment 3 entailed hardening and pot culture. The plantlets of Jyothi and N22 were first transferred to distilled water for a few days to let the leaves to unfurl and then planted in sterilised potting mixture. The plants were then kept under 16 hour photoperiod for 10 days. These plants were further hardened in a polytunnel and later grown in a rain shelter using standard agronomic practices. N22 and Jyothi plants grew with healthy leaves and formed panicles within two months but N22 exhibited poor tillering.
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    Enhancing nutrient use efficiency through nano-DAP in upland rice (Oryza sativa L.)
    (Department of Agronomy, College of Agriculture, Vellayani, 2024-01-10) Akshara, B.; Shimi, G J
    The study entitled “Enhancing nutrient use efficiency through nano-DAP in upland rice (Oryza sativa L.)” was conducted during 2021-2023 at College of Agriculture, Vellayani. The main objectives of the study were to evaluate foliar applied DAP and nano-DAP on growth, nutrient use efficiency, yield and working out the economics in upland rice. The study was carried out in randomized block design with (4×2)+1 treatments replicated thrice at Instructional Farm from November 2022 to February 2023. The treatments included two factors, levels of recommended dose of nutrients (N) with four levels of N and P (n1: 100 per cent N and P; n2: 75 per cent N and P; n3: 50 per cent N and P and n4: 25 per cent N and P); and two levels of foliar fertilizers (F) applied at AT (active tillering) and PI (panicle initiation) stages (f1: 2 per cent DAP and f2: 0.2 per cent nano-DAP), compared against KAU POP as control. The rice variety used for the study was Prathyasa and nutrient recommendation followed was 60:30:30 kg NPK ha-1 as per the KAU POP. The results of the study indicated that the levels of recommended dose of nutrients had significant effect on growth attributes of rice. Significantly taller plants were recorded in n1 and was on par with n2 and n3 at flowering stage. The highest number of tillers per square metre, leaf area per hill and LAI were recorded in n1 at AT (663.33 tillers m-2 , 593.58 cm2 , 3.96 respectively), PI (739.00 tillers m-2 , 1003.88 cm2 , 6.69 respectively) and flowering (683.00 tillers m-2 , 1140.90 cm2 , 7.61 respectively) stages. Leaf area duration (LAD) during AT to PI (79.87 days), PI to flowering (107.24 days), flag leaf area per hill (61.23 cm2 ) and total dry matter production (8852 kg ha-1 ) were also higher in n1. Among foliar fertilizers, the highest leaf area per hill and LAI were obtained in f1 at PI and flowering stages. The longest LAD during PI to flowering stages, and flag leaf area per hill were also recorded in f1. Considering the interaction, n1f1 resulted in significantly higher leaf area, flag leaf area per hill, and total dry matter production. Treatments are significantly higher than that of control with respect to growth attributes in rice. The productive tillers per square metre (513.17 and 455.75), number of grains per panicle (105.75 and 95.56), grain yield (4.91 t ha-1 and 4.46 t ha-1 ) and straw yield (5.73 t ha-1 and 5.24 t ha-1 ) were observed to be the highest in n1 and f1 respectively. Significantly higher harvest index (0.467) was noticed in n2 which was on par with n1. The lowest sterility percentage was recorded in f1. The combination, n1f1 was significantly superior in producing the higher productive tillers per square metre, grains per panicle, grain and straw yield. However, the highest harvest index was obtained in n2f2 (0.472). Significantly higher leaf N and P contents were recorded in n1 for both AT and PI stages. At harvest stage, grain N content was higher in n1 which was on par with n2. The highest straw N content and grain P content were recorded in n1. The highest straw P content was in n2 and straw K content was higher in n1 which was on par with n2 and n3. Among foliar fertilizers, f1 resulted in higher leaf N content at PI stage, grain P and K contents and straw P content at harvest stage. Significantly higher leaf N content at PI, grain and straw P contents and grain K content at harvest stage were recorded in f1. Considering the interaction, n1f1 had significantly higher leaf N and P contents at AT and PI stages but was on par with n1f2. At harvest stage, higher grain P content was with n1f1 and n1f2. However, straw P content was higher in n2f2 and n3f1. Straw K content was higher in n1f2 but was on par with n2f1. Crude protein content was higher in n1, was on par with n2 and n3. The treatment, n1 resulted in significantly higher N (130.02 kg ha-1 ), P (32.31 kg ha-1 ) and K uptake (145.32 kg ha-1 ) but was comparable with n2 for K uptake. Foliar fertilizers had significant effect on P uptake (26.05 kg ha-1 ) with the highest value in f1. When significantly higher N uptake of 136.69 kg ha-1 was recorded in n1f1, the interaction n2f1 produced the highest K uptake. On comparing treatments with control, n1f1 recorded significantly higher N, P, K uptake. When the highest agronomic efficiency (AE) and physiological efficiency (PE) of N and P were recorded in n2, the highest apparent recovery efficiency (ARE) of N was obtained in n4, and that of P in n3. The treatment f1 resulted in the highest AE of N (36.86 kg kg-1 ), and PE of N (19.24 kg kg-1 ) and P (73.24 kg kg-1 ). However, higher ARE of P (94.74%) was recorded in f2. Considering the interaction, PE of N was significantly higher with n3f1 whereas PE of P was the highest with n2f1. Significantly higher ARE of N and P were obtained in n3f2. Significantly higher chlorophyll contents at AT and PI stages were observed in n1. Among foliar fertilizers, f1 had the highest value at PI stage. Soil available N (263.58 kg ha-1 ) was higher in n1. The highest available P was recorded with n2 (106.82 kg ha-1 ), f1 (103.92 kg ha-1 ) and n2f1 (117.86 kg ha-1 ). Significantly higher net income and B:C ratio were recorded in n1 (₹ 39,497 ha-1 , 1.21), f1 (₹ 21,633 ha-1 , 1.12) and n1f1 (₹ 47,124 ha-1 , 1.26). From the study it could be concluded that, soil application of 100 per cent recommended dose of N (60 kg ha-1 ), P (30 kg ha-1 ) and K (30 kg ha-1 ) supplemented with foliar application of 2 per cent DAP (Diammonium phosphate) at active tillering and panicle initiation stages were effective for enhancing growth, productivity, nutrient use efficiency and economics in upland rice Rice
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    Identification of simple sequence repeat (SSR) markers linked to high temperature tolerance in rice (Oryza sativa L.) by bulked segregant analysis
    (Department of Molecular Biology and Biotechnology, College of Agriculture, Vellayani, 2023-08-24) Aparna, K.; Beena, R
    The study entitled “Identification of Simple Sequence Repeat (SSR) markers linked to high temperature tolerance in rice (Oryza sativa L.) by bulked segregant analysis” was conducted at the Department of Molecular Biology and Biotechnology and the Department of Plant Physiology, College of Agriculture, Vellayani, Thiruvananthapuram during 2022-23. The objective of the study was to evaluate the F3 population of Uma X NERICA-L-44 for identifying SSR markers linked to high temperature tolerance in rice by bulked segregant analysis and to establish the role of the genes associated with them in heat tolerance. Seeds collected from 46 F2 segregants (23 tolerant and 23 susceptible) of Uma X NL-44 along with their parents were raised and transplanted to pots after 18 days of sowing in the Kharif season of 2022. These 48 lines were kept under normal conditions up to the maximum tillering stage and then transfered to polyhouse conditions where it was subjected to a high temperature of 38-40 ⁰C. Phenotypic evaluation was done for plant height, tiller number, productive tiller number, days to flowering, time of anthesis, Pollen viability, Spikelet fertility, and 100 seed weight. Based on spikelet fertility percentage, 10 extremely tolerant and 10 extremely susceptible lines were selected. DNA was extracted from the selected 10 heat tolerant and 10 susceptible lines along with the parents by the modified Cetyltrimethylammoniumbromide (CTAB) method of DNA extraction. The quality and quantity of extracted DNA were checked by using agarose gel electrophoresis and spectrophotometric analysis. The DNA samples were screened by using 55 SSR primers distributed across the rice genome. Out of 55 SSR primers, 18 of them showed polymorphism between the parents. Then equal quantity of DNA was pooled to make heat tolerant and susceptible bulks. The bulked DNA samples were screened using the 18 SSR primers that have shown polymorphism between parents. The polymorphic markers between the tolerant and susceptible bulks were used to study the segregation of the alleles in the individual lines constituting the tolerant and susceptible bulks. Through bulked segregant analysis (BSA), 10 SSR markers were found polymorphic between tolerant and susceptible bulks and their individual lines. It revealed the possible presence of genetic loci for heat tolerance in those locations. Out of the 10 SSR markers identified in the BSA (RM337, RM10793, RM242, RM5749, RM6100, RM490, RM3475, RM470, RM473, and RM556), nine of the markers have been previously reported for heat tolerance traits. RM337 is newly identified in the present study. The genes in the 200 kb vicinity of the RM markers were retrieved from the Rice Annotation Project database. To get a deeper insight into how these genes participate in heat tolerance, gene annotation, gene ontology (GO) enrichment analysis, and trait ontology (TO) were performed for all the significant markers. Upon screening of the loci in the proposed region, genes LOP1 (LOC_Os08g01330) and LOP2 (LOC_Os08g0112) were found to be associated with RM337. LOP1 is a NAC transcription factor that is reported to be involved in the regulation of cellulose synthesis, secondary wall biosynthesis (Os08t0103900-01), and inflorescence development. LOP2 is also known as OsMOT1, which is a molybdate transporter involved in the uptake and translocation of molybdate (Os08t0101500-01). Hence their expression was analyzed in the two rice varieties under both control and high temperature conditions. LOP1 was found to be significantly upregulated in the NL-44 variety under high temperature condition compared to the normal temperature conditions and susceptible variety, Uma. On the other hand, the gene LOP2 was found to be upregulated in both varieties under the higher temperature condition compared to their respective controls. However, the relative expression in Uma was higher than in NL-44. In the present study, the phenotypic evaluation and bulked segregant analysis using 55 SSR primers in F3 generation of Uma X NL-44 revealed that 10 SSR markers (RM222, RM242, RM337, RM470, RM473, RM490, RM556, RM5749, RM6100, RM10793) are linked to high temperature tolerance in rice. The newly identified SSR marker RM337 and associated gene LOP1 is also linked to high temperature tolerance in rice. The results demonstrate that BSA using SSR markers and gene annotation and enrichment analysis is useful in identifying genomic regions and genes that contribute to thermotolerance respectively. Also, these F3 lines can be used for the development of high temperature tolerant rice varieties and these markers can be used for marker assisted selection (MAS) in rice.