PhD Thesis
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Item Baseline susceptibility of rice leaf folder Cnaphalocrocis medinalis (Guenee) (Lepidoptera: Crambidae) to selected insecticides(Department of Agricultural Entomology, College of Agriculture, Vellanikkara, 2025-08-29) Seena R Subhagan; Berin PathroseWith the rising food production demands, pesticides remain essential for achieving high yields, particularly in staple crops like rice. Despite the known environmental hazards of chemical pesticides, their repeated use has become common practice, often leading to selection pressure and the development of insecticide resistance. This issue is exacerbated when insect pests like the rice leaffolder, Cnaphalocrocis medinalis, which undergoes several generations a year, are exposed to the same insecticide across consecutive generations. Recent failures in controlling rice leaffolder outbreaks in Kerala have raised concerns, though no formal studies have documented insecticide resistance in these populations. This study aimed to address this gap by assessing the susceptibility of rice leaffolder populations to selected insecticides and investigating potential resistance mechanisms. Field populations from five agroecological units (AEUs) in Kerala were assessed for insecticide resistance through laboratory bioassays, with WYD (AEU 20) as a susceptible reference. The PKD (AEU 23), KUD (AEU 4), and TCR (AEU 6) populations experienced significant selection pressure, leading to moderate to high resistance to the tested insecticides, surpassing the resistance observed in the ONT (AEU 3) population. Resistance to acephate (5.07- to 172.53-fold) was identified for the first time in India. High resistance to quinalphos (133.24- to 611.37-fold) and carbosulfan (25.40- to 347.96-fold) were also noted. The observed carbosulfan resistance, despite no prior use, likely stems from cross-resistance due to previous organophosphate exposure, as both target acetylcholinesterase. Continuous exposure intensified resistance to lambda-cyhalothrin (up to 763.66-fold) and fipronil (up to 154.83-fold). Diamide resistance was significant, with chlorantraniliprole (1089.63 fold) and flubendiamide (1572.64-fold), marking the first reported flubendiamide resistance in C. medinalis in India. Cross-resistance to cartap (14.85- to 23.90-fold) and emamectin benzoate (24.97- to 81.09-fold) suggested resistance mechanisms driven by non-specific detoxification pathways. Further, the study aimed to elucidate the biochemical mechanisms of resistance by assessing the activities of detoxification enzymes. Resistant populations exhibited significantly elevated activities of carboxylesterase (CarE) (1.1–1.6-fold), cytochrome P450-dependent monooxygenase CytP450) (1.5–2.5-fold), and glutathione S transferase (GST) (2.3–3.0-fold). These findings underscore the increased activity of detoxifying enzymes as a contributing factor to the resistance observed in C. medinalis further confirmed through synergism bioassays. Bioassays with synergists revealed diverse resistance mechanisms across populations, driven by variations in detoxification enzyme activity. Metabolic resistance to acephate, quinalphos, carbosulfan, and lambda-cyhalothrin was primarily associated with CarE, CytP450, and GST, either individually or in combination. Multiple enzyme involvement was evident in PKD, KUD, and TCR, while CytP450 had a dominant role in ONT, highlighting enzyme-specific contributions to insecticide resistance. However, metabolic detoxification was not the primary driver of chlorantraniliprole and flubendiamide resistance in most populations, suggesting the involvement of alternative mechanisms. Minor contributions from CarE and CytP450 were detected in PKD, while slight synergistic effects in KUD may be linked to endosymbiont mediated resistance. In the case of fipronil, resistance was mediated by CytP450 in PKD, KUD, and ONT, whereas non-metabolic mechanisms likely contributed to the high fipronil resistance observed in TCR. These findings underscore the complexity of resistance mechanisms and highlight the need for further investigation into alternative pathways for diamide and fipronil resistance. This study investigated target site insensitivity as a potential resistance mechanism to diamides and fipronil in C. medinalis by analyzing mutations in the ryanodine receptor (RyR) and resistance to dieldrin (Rdl) genes. Gene duplication and a novel I4712N mutation in transmembrane (TM) domain 3 of RyR were detected in ONT and KUD populations, while PKD and TCR populations had a nonsynonymous mutation (F4691L) and a nonsense mutation (Y4692*) in the TM2-TM3 linker of the RyR gene, which may impact diamide binding. Additionally, a K4885K synonymous mutation was identified in TCR in the TM4-5 linker. As these mutations are newly reported, functional validation is required to confirm their role in resistance. Molecular analysis of the Rdl gene identified an A282S mutation in TM 2 of all populations, including the susceptible WYD, suggesting a limited role in fipronil resistance. Notably, this study reports a novel V457F mutation in TM 4 of the Rdl gene in the resistant TCR population, which may have contributed to high fipronil resistance (154.83-fold) by altering GABA receptor function. The absence of target-site mutations for isoxazoline and meta-diamides suggests their continued efficacy against C. medinalis. Metagenome analysis identified Pantoea sp. and Wolbachia sp. as potential endosymbiont contributors to microbial detoxification of chlorantraniliprole and flubendiamide resistance in KUD. These findings provide new insights into resistance mechanisms and highlight the need for further functional confirmation. Rice leaffolder populations in Kerala have developed diverse resistance mechanisms in response to sustained insecticide pressure, exhibiting metabolic and target-site adaptations. This study presents the first detailed evaluation of insecticide resistance in C. medinalis from Kerala, uncovering alarming resistance levels to multiple insecticides, including newly documented cases for acephate, carbosulfan, lambda-cyhalothrin, and flubendiamide. Metabolic detoxification, primarily through CarE, CytP450, and GST, played a key role in resistance against organophosphates, carbamates, and synthetic pyrethroids, with multiple detoxification pathways raising concerns about cross-resistance. Mutations in the RyR and Rdl genes suggest target site insensitivity for diamides and fipronil (TCR), while the potential involvement of endosymbionts in microbial detoxification (KUD) adds another layer of complexity. These findings highlight the urgent need for proactive resistance management strategies, integrating insecticide rotation, biological control, and molecular monitoring to sustain effective pest management in Kerala’s rice ecosystems.Item Nano zinc nutrition in rice based cropping systems in high Phosphorus soils(Department of Agronomy, College of Agriculture,Vellayani, 2025-07-04) Boddu Archana; Bindhu, J SThe project entitled “Nano zinc nutrition in rice based cropping systems in high phosphorus soils” was conducted at College of Agriculture, Vellayani, Thiruvananthapuram, Kerala, during 2020-2025. The objectives of the study were to evaluate the response of rice to nano zinc in high P soils, study the residual effect of nano zinc nutrition on growth and yield of succeeding crops, study the P - Zn interactions and to identify the promising crop sequence in terms of system productivity and profitability. The study comprised three parts which were carried out at Integrated Farming System Research Station (IFSRS), Karamana, Thiruvananthapuram, Kerala during 2022-23. The first and second parts of the experiment were laid out in randomized complete block design with three replications using variety Uma (Mo 16) in virippu and mundakan seasons. The treatments comprised T1- [Soil application (SA) of ZnSO4 at 20 kg ha-1 (applied only in virippu season)], T2- [Nutri priming (NP) with nano Zn at 0.05%], T3- [NP with nano Zn at 0.05% + Foliar spray (FS) with nano Zn at 0.05% at maximum tillering (MT) stage], T4- [NP with ZnSO4 at 0.5%], T5- [NP with ZnSO4 at 0.5% + FS with nano Zn at 0.05% at MT stage], T6-[FS with nano Zn at 0.05% at MT and panicle initiation (PI) stages], T7- [FS with ZnSO4 at 0.5% at MT and PI stages], T8- [Control (Recommended Dose of Nutrients (RDN) without application of P and Zn)]. The RDN were 90:45:45 (N:P2O5:K2O) kg ha-1 modified as 64:22:53 kg ha-1 on soil test basis. The growth and yield attributes of rice were significantly influenced by nano zinc nutrition. Taller plants with the highest number of tillers per m2, higher leaf area per hill, leaf area index and dry matter production were recorded in T3 and was on par with T6 during both the seasons. The yield attributes viz., higher numbers of productive tillers per hill, grains per panicle, grain weight per panicle and lower sterility percentage were observed in T3 and was on par with T6 during both the seasons. The pooled mean over the seasons revealed that the grain yield (5161 kg ha-1) and straw yield (6148 kg ha-1) of rice were higher in T3 and was on par with T6. The grain yield increased by 78 and 69 per cent in T3 and T6, respectively over control. The nutrient uptake by plants at panicle initiation and harvest were significantly affected by zinc nutrition. The higher uptake of N, P, K, Ca and Zn by the rice plants at panicle initiation and harvest were observed in T3 which was comparable to T2 and T6 at panicle initiation and comparable to T6 at harvest during both virippu and mundakan. The nutrient use efficiency of P and Zn in terms of agronomic efficiency was the highest in T3 and T6, respectively during virippu and mundakan. The available nutrient status of the soil after each season was significantly influenced by nano zinc nutrition. The available N, P, K and Zn were higher in T3 and T6 during both virippu and mundakan. The dehydrogenase and phosphatase activities were significantly higher in T3 and were on par with T6. The highest net returns (₹ 76622 ha-1 and ₹ 86368 ha-1) and B:C ratio (1.74 and 1.82) were recorded in T3 during virippu and mundakan, respectively. The third part of the experiment was conducted during summer season to study the residual effect of nano zinc nutrition on growth and yield of succeeding crops. The experiment was laid out in strip plot design and was replicated thrice wherein, each individual plots of previous crop were divided to three sub plots and crops viz., grain cowpea (Kanakamony (PTB 1)) and bhindi (Anjitha) were grown in two sub plots and one sub plot was kept as fallow. The main plot treatments were residual nutrients of the previous seasons (N1 to N8) and the sub plot treatments were three crop sequences (C1- rice-rice-grain cowpea, C2- rice-rice-bhindi, C3- rice-rice-fallow). Growth, yield attributes and yield of summer crops viz., grain cowpea and bhindi were higher in N1. Available N, P, K, Zn, and soil enzyme activities were influenced by the residual nutrient status of the soil and crop sequences. Higher available N was observed in N6 and N5, available P, K and dehydrogenase activity were higher in N3, available Zn was the highest in N6, and phosphatase activity was higher in N1. Among the crop sequences, available P, Zn and dehydrogenase activity were the highest in C1. Among the interactions, the highest available Ca, available Zn and phosphatase activity were observed in n8c2, n3c1 and n1c1, respectively. The highest system yield (11504 kg ha-1) and system productivity (32 kg ha-1 day-1) were observed in N3 which was on par with N6. The crop sequence C2 recorded the highest system yield (10592 kg ha-1), while both C2 and C1 sequences showed higher system productivity. Among the interactions, n3c1 and n3c2 recorded the highest system yield (12100 and 12090 kg ha-1, respectively) and system productivity (33 kg ha-1 day-1, respectively). The highest energy efficiency, the lowest specific energy, the highest energy productivity and the highest energy intensity were recorded in N3. Among the crop sequences, C1 recorded the highest energy efficiency (7.42) and energy productivity was higher in C2 (0.62 kg MJ-1). Among the interactions, n3c3 recorded the highest energy efficiency. The data on nutrient balance showed a net gain of nitrogen in all treatments in C1 and C2, except N8. The rice-rice-fallow sequence showed a net gain in N3, and N6. Available phosphorus showed a net loss among all sequences and all treatments except N8. Potassium had a positive balance in the rice-rice-grain cowpea and rice-rice-bhindi in all treatments except N8. In rice-rice-fallow sequence, net gain of K was observed in N3 and N6. Zinc balance was positive in all the crop sequences and all the treatments except N1 and N7 which recorded net loss of Zn. Among the residual nutrients, the highest system net returns (₹ 173627 ha-1) and B:C ratio (1.49) were observed in N3 whereas, among crop sequences, rice-rice-bhindi (C2) showed the highest net returns (₹ 114127 ha-1) and B:C ratio (1.47). Among the treatment combinations, n3c2 recorded the highest net returns (₹ 182091 ha-1) and the highest B:C ratio (1.79) in n3c3. From the study, it can be concluded that nutri priming with nano zinc at 0.05% (50 ml ha-1) followed by foliar spray of nano zinc at 0.05% (250 ml ha-1) at maximum tillering stage along with soil test basis recommended dose of nutrients was effective way in enhancing the productivity and profitability of rice in high phosphorus soils. The growth and yield of grain cowpea and bhindi were the highest in residual nutrient with soil application of ZnSO4 at 20 kg ha-1 [applied only in virippu]. Rice-rice-bhindi was identified as the promising crop sequence in terms of system productivity and system profitability.Item Endophytic and growth promoting activities of the entomopathogenic fungus, Lecanicilliumsaksenae (Kushwaha) Kurihara and Sukarno in rice(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2025-07-11) Shree Naveena, PThe study entitled “Endophytic and growth promoting activities of the entomopathogenic fungus, Lecanicilliumsaksenae (Kushwaha) Kurihara and Sukarno in rice” was carried out during 2020-2024 in the Department of Agricultural Entomology, College of Agriculture, Vellayani, Thiruvananthapuram. The objective of the study was to establish the entomopathogenic, endophytic and growth promoting attributes of L. saksenae in rice. The infection process of L. saksenae in the rice bug, investigated using Scanning Electron Microscopy (SEM), revealed five step infection processes comprising adhesion, germination, penetration, colonisation/invasion, and conidiation/dissemination at 24, 48, 72, 96 and 120 hours post inoculation (HPI), culminating in dissemination of spores facilitating horizontal transmission and complete mycosis evidenced by mummified appearance, by 144 HPI. Biochemical mechanisms involved in pathogenesis were deciphered using metabolomic analyses of the infected rice bug. Gas Chromatography-Mass Spectrometry (GC-MS) and High-Resolution ORBITRAP Liquid Chromatography Mass Spectrometry (HR-LC-MS) revealed an array of 19 insecticidal compounds, three immunosuppressors, three antimicrobial compounds, and 13 other metabolites related to insect metabolism, highlighting the complex biochemical arsenal employed by L. saksenae in insect pathogenesis. In addition to entomopathogenicity, L. saksenae exhibited significant plant growth-promoting traits. Plate assays and spectrophotometric observations, displayed elevated levels of phytohormones, notably gibberellic acid (GA3: 334.68 µg mL-1) and indole acetic acid (IAA: 30.00 µg mL-1). It also exhibited zinc and phosphate solubilization efficiency (1.15 SE and 1.70 SE), which are related to nutrient assimilation. The siderophore (2.23 AU) and ammonia production (15.42 µmol mL-1) levels which help in nutrient uptake were significant and higher than those in other entomopathogenic fungi. The study further examined endophytic association of L. saksenae upon seed inoculation, in rice through re-isolation, microscopy, and PCR. The fungus could be reisolated from roots, stems, and leaves of the inoculated plants up to 90 days after seed inoculation (DAI) demonstrating its systemic translocation within then plant. Maximum colonisation was noted in roots (72.86 per cent), followed by stem (64.29 per cent) and leaves (40.00 per cent) at 30 DAI, which tapered to 32.86, 17.14 and 11.4 per cent at 90 DAI. SEM observations confirmed internal colonisation of L. saksenae in the leaf stem and root tissues of inoculated rice, which was further established by PCR amplification, that unequivocally matched with the original Accession. MN545844 deposited by Rani et al. (2015). Comparative metabolomic analysis between inoculated and uninoculated plants revealed significant biochemical changes due to L. saksenae colonisation. Significant elevation of proteins, sugars, and phenolic compounds in the inoculated plants indicated a metabolic shift that favours enhanced growth and defence. Untargeted GC-MS analysis revealed predominance of carbohydrates at maximum tillering stage which indicates protection at cellular levels and promotion of plant growth. Untargeted ORBITRAP HR LC-MS detected the presence of 10 insecticidal/insectistatic, one nematicidal, and three antimicrobial compounds, suggesting that L. saksenae induced the defence mechanism in inoculated plants. LC-MS/MS revealed profound modulation of growth and defence related hormones at critical plant growth stages due to fungal inoculation. Inoculated plants showed increased growth related hormones such as indole-3-butyric acid (IBA), IAA, GAs, N6-benzylaminopurine (6-BAP), trans-zeatin (tZ), and trans-zeatin riboside (tZR) at the seedling stage, and IAA, IBA, GA3, GA4, GA7, and tZR at the maximum tillering stage. Defence hormones such as abscisic acid (ABA), salicylic acid (SA), jasmonic acid (JA), cis-jasmone (CJ), methyl jasmonate (MeJA), epibrassinolide (EBL), and 1 aminocyclopropane-1-carboxylic acid (ACC) were significantly higher in the inoculated plants at the seedling stage and SA, JA, CJ, MeJ, and ACC at the tillering stage, which are related to increased resistance to pest infestation. Inoculated seeds exhibited improved germination (6.38 per cent) and the seedlings exhibited increase in shoot and root length (30.30 per cent, 55.58 per cent), number of leaves and roots (35.29 per cent, 26.58 per cent) and the seedling vigor index (51.46 per cent), compared to the control. Pot culture experiments proved enhancedplant height (25.80 per cent), number of tillers (36.99 per cent), panicle count (30.00 per cent), grain number (24.20 per cent), grain yield (30.00 per cent), and straw yield (28.43 per cent) in the inoculated plants. In L. saksenae colonised, rice bug infested plants, there was a significant reduction in the number of eggs laid (29.40 per cent), number of feeding punctures (32.83 per cent) and grain damage (37.45 per cent) compared to control plants. Gene expression analysis revealed the upregulation of defence related genes, phenyl ammonia lyase (PAL) and lipoxygenase (LOX) in both inoculated and control plants, indicating it as a general stress response to herbivory. However, the pathogenicity related genes of the entomopathogens viz. subtilin like protease (PR1) and chitinase II (CHIT II) were not expressed in the colonised plants, as these genes are typically involved in breaching of insect cuticle. Headspace volatile analysis (GC-MS) of L. saksenae inoculated plants before rice bug infestation revealed the presence of 2-heptanone (natural enemy attractant and insect repellent), and 4-methylbenzaldehyde (oviposition deterrent). L. saksenae inoculated, rice bug infested plants, displayed defence related volatiles, such as S linalool (natural enemy attractant and insect repellent), methyl salicylate (natural enemy attractant), 9-octadecenamide (Z) (insecticidal), N-methyl-1-adamantaneacetamide (insecticidal and repellent). Additionally, there was upregulation of defence related enzymes, PAL, catalase (CAT), superoxide dismutase (SOD), polyphenol oxidase (PPO), peroxidase (POD), and ascorbate peroxide (APX) in inoculated plants. Temporal profiling revealed a dynamic activation pattern, where PPO, SOD, and APX peaked early at 48 hours after insect release (HAR), followed by a surge in PAL and POD at 72 HAR, and a delayed peak of CAT at 96 HAR. Importantly, L. saksenae inoculated plants displayed earlier and more intense upregulation of SOD and PAL, indicating a primed defence in plants during herbivore attack. These biochemical changes may underlie the observed reduction in pest performance and feeding efficiency. The above findings established the entomopathogenic, endophytic and growth promoting attributes of the indigenous isolate, L. saksenae in rice. By elucidating the tritrophic interactions involving the fungus, plant and insect, the study positions L. saksenae, as a "two-in-one" eco-friendly solution for plant health management in rice.Item Development of breeding lines in rice(Oryza sativa L.) Pyramided with R genese for resistance to brown plant hopper (BPH) by marker assisted selection.(Department of plant breeding and genetics, college of agriculture, Vellayani, 2023-07-21) Arun Chacko; Jayalekshmy, V GThe present study ‘Development of breeding lines in rice (Oryza sativa L.) pyramided with R genes for resistance to Brown Plant Hopper (BPH) by markerassisted selection’ was conducted in the Department of Plant Breeding and Genetics, College of Agriculture, Vellayani and Regional Agricultural Research Station, Pattambi, during the year 2019-2022, with an objective to introgress R genes for resistance to BPH in the background of the elite variety Jyothi using marker-assisted selection. The study comprised of two main experiments. Experiment-I aimed at the BPH bioassay, assessment of morphological and biochemical characters linked to BPH resistance in the donor and recipient parents followed by the validation of the presence of genes for resistance using specific molecular markers. Recipient parent (Jyothi) and probable donors for BPH resistance from the results of a concluded project in the Department of Plant Breeding and Genetics, COA, Vellayani, and other R gene introgressed lines from IRRI were selected for screening. The BPH bioassay was done using the modified seedbox screening test (MSST) developed by Velusamy (1986). BPH-affected seedling survival rate was calculated based on the Standard Evaluation System (SES) scale of 0-9 (IRRI, 2013). Among the twelve rice genotypes screened, PTB-33, PTB-21, and IR7103-121-15-B were classified as highly resistant and the genotypes IR65482-7-216-1-2 and RP2068-18-3-5 were classified as resistant to BPH infestation. The japonica variety Kinandang Patong was moderately resistant to BPH. The recipient parent Jyothi and five other genotypes viz., Manu Ratna, White Ponni, Wayrarem, Vandana, and APO were classified as highly susceptible to BPH infestation. Five genotypes, Jyothi (recipient parent), PTB-33, IR7103-121-15-B, IR65482-7-216-1-2, and RP2068-18-3-5 were forwarded for studying the BPH resistance reaction. The antibiosis and tolerance mechanisms of BPH resistance were explored in terms of nymphal survival rate, honey-dew test, functional plant loss index (FPLI), and tolerance index (TI). The recipient parent, ‘Jyothi’ turned out to be highly susceptible, and ‘PTB-33’ showed high resistance to BPH feeding among the rice genotypes screened. Other genotypes, IR65482-7-216-1-2 RP206818-3-5, and IR7103-121-15-B showed intermediate values compared to PTB-33 and the highly susceptible variety ‘Jyothi’. The morphological characters and biochemical parameters linked with BPH resistance of five genotypes were assessed in a completely randomized design (CRD) with four replications. The results revealed that BPH feeding, survival, functional plant loss index, and disease score were positively correlated with protein content and negatively correlated with phenol and ascorbic acid content. Reducing sugar content in plants did not show much effect on BPH resistance. The genetic parameters, phenotypic and genotypic coefficient of variation were higher in seven characters, and moderate in six characters indicating high variability among the parents. High heritability and genetic advance in the characters except for the number of productive tillers, and culm thickness and grain length respectively indicated the presence of additive gene action. The characters, culm thickness, 1000 grain weight, and protein content showed a significant positive correlation with the functional plant loss index (FPLI). Path analysis of morphological and biochemical characters with FPLI as the dependent variable showed the direct positive effect of the number of productive tillers, panicle length, number of grains per panicle, grain breadth, LB ratio, and phenol content on FPLI. The validation of the presence or absence of genes for BPH resistance in donor and recipient parents was done using SSR markers RM589 for the Bph-3 gene, RM3331 for Bph-18, RM8213 for Bph-20, and RM28561 for Bph-21. Distinguishable polymorphic bands were obtained in SSR markers RM589 (200 bp for resistance and 180 bp for susceptibility) and RM3331 (110 bp for resistance and 130 bp for susceptibility). Based on BPH screening, resistant reaction study, and gene validation, the KAU released variety ‘PTB-33’ and IRRI introgression line IR65482-7-216-1-2 were selected as the donors for Bph-3 and Bph-18 gene respectively in the marker-assisted breeding program. The second experiment was marker-assisted backcrossing to introgress the R genes (Bph-3 and Bph-18) into the background of elite high-yielding but susceptible variety Jyothi. The donors PTB-33 and IR65482-7-216-1-2 were crossed independently with Jyothi to obtain the F1 generation followed by backcrossing with Jyothi to develop the BC1F1 generation. Phenotyping for ten morphological characters and genotyping using gene-specific SSR markers were carried out in all the backcross generations. Genotyping of 63 BC1F1 lines derived from the PTB-33 donor parent with RM589 marker identified 28 plants with the Bph-3 gene in heterozygous condition. Genotyping of 78 BC1F1 lines derived from the IR65482-7-216-1-2 donor parent with RM3331 marker identified 36 plants with Bph-18 gene in heterozygous condition. The goodness of fit test (χ2 test) in BC1F1 lines with genotypic data showed that the genes Bph-3 and Bph-18 followed the ratio of simple dominance. Intercrossing of BC1F1 lines involved two crosses viz., the PTB-33 derived BC1F1 lines with Bph-3 in heterozygous condition as the female parent and IR65482-7-216-1-2 derived BC1F1 lines with Bph-18 in heterozygous condition as male parent denoted as ‘ICAB’ and the reciprocal cross denoted as ‘ICBA’. Among the twenty-two ICAB progenies, three plants showed both genes (Bph-3 and Bph18) in heterozygous condition, and among the eighteen ICBA progenies, five plants were obtained with both genes (Bph-3 and Bph-18) in heterozygous condition. The Euclidean Distance of intercrossed BC1F1 lines from the recipient parent Jyothi using proximity dissimilarity matrix analysis was calculated to select the intercrossed BC1F1 lines more similar to the recipient parent. Eight intercrossed BC1F1 lines with Jyothi-specific characters and both genes in heterozygous condition were backcrossed with Jyothi to develop BC2F1 lines. In the genotypic evaluation of twenty-six BC2F1 lines, five lines showed the presence of both genes (Bph-3 and Bph-18) in heterozygous condition. The five BC2F1 lines with maximum similarity in proximity dissimilarity matrix analysis were selfed and three-hundred and twenty BC2F2 lines were forwarded to BPH bioassay in the seedling stage at RARS, Pattambi, and COA, Vellayani. Eighty-nine BC2F2 lines showed different levels of resistance in the BPH bioassay. Genotyping of these lines showed the presence of both genes (Bph-3 and Bph-18) in homozygous resistant condition in four lines namely, ICAB-1/3/6, ICAB-1/3/7, ICAB-1/6/2, and ICAB-1/6/10. The similarity percentage of these four lines with the recipient parent in proximity dissimilarity matrix analysis was obtained as 84.51 per cent in ICAB-1/3/6, 89.27 per cent in ICAB-1/6/10, 91.15 per cent in ICAB-1/6/2, and 91.6 per cent in ICAB-1/3/7. The developed breeding lines, possessing pyramided R genes for BPH resistance in the background of Jyothi, can be used to develop essentially derived varieties from Jyothi with BPH resistance. This will offer an improved and sustainable solution for combating BPH infestations, reducing reliance on chemical insecticides, and enhancing the stability of rice production.Item Identifying resilient rice based cropping systems involving tuber crops for lowlands(Department of agronomy, college of agriculture ,Vellayani, 2023-10-09) Anju, B Raj.; Jacob JohnThe study entitled “Identifying resilient rice based cropping systems involving tuber crops for lowlands” was conducted at Department of Agronomy, College of Agriculture, Vellayani during the period from 2019-2023. The major objectives of the study were to evaluate the performance, in terms of yield and economics, of different rice based cropping systems involving tuber crops in lowlands under different nutrient levels, to analyse weed dynamics, soil health and carbon dioxide emission, and to assess the residual effect on the succeeding virippu rice crop. It could be concluded that, among different rice based cropping systems involving tuber crops in lowlands, rice-rice-sweet potato (C2) performed better in terms of yield, economics and weed control. Grain yield of succeeding crop of rice, recorded with F2 and F1 were comparable. Thus it was concluded that FYM, N and P could be reduced by 25 per cent in rice based cropping systems. Rice-(cassava+bush cowpea)-daincha (C4) recorded significantly higher available nutrients, carbon fractions with less CO2 emission. Hence, rice-(cassava+bush cowpea)-daincha (C4) could be adjudged as the resilient rice based cropping system involving tuber crops in lowlands.Item Assessment of ion interactions in the acid saline soils (Orumundakan) to evolve a customized rice nutrition strategy(Department of Soil Science and Agricultural Chemistry, College of Agriculture,Vellayani, 2023-07-21) Anjali Bhadra, VijayA study on 'ʽʽAssessment of ion interactions in the acid saline soils (Orumundakan) to evolve a customized rice nutrition strategy ˮ was undertaken with an objective to identify the major nutritional constraints for rice production and to evolve a customized nutrient management strategy by integrating varietal tolerance and nutrition. From the investigation it can be concluded that there is soil fertility constraints in the Orumundakan tract of AEU 3. The soil was very strongly acidic with low nutrient status except for P, Fe, Mn and S. From the different indices computed it was found that K and Mg are the limiting ion in this soil. Management of nutritional constraints in this tract should be based give more emphasis on K and Mg fertilizers. Soil test based NPK + lime along with foliar application of customised fertilizer (T7) was found to be effective in management of the fertility constraints of Orumundakan tract which resulted in the highest yield and B: C ratio. Profitable rice cultivation in this tract is possible through the integration of acid-saline tolerant rice variety and soil test based NPK+ lime with foliar application of customised fertilizer at critical growth stages of the crop.Item Population dynamics and management of rice yellow stem borer Scirpophaga incertulas (Walker) and leaf folder Cnaphalocrocis medinalis (Guenee) in South Kerala(Department of Agricultural Entomology, College of Agriculture , Vellayani, 2022-12-19) Sharanappa.; Suja, GThe present study entitled “Population dynamics and management of rice yellow stem borer, Scirpophaga incertulas (Walker) and leaf folder, Cnaphalocrocis medinalis (Guenee) in South Kerala” was carried out at Department of Agricultural Entomology, College of Agriculture-Vellayani, from 2018 to 2021. A survey was conducted in major rice growing areas viz. Thiruvananthapuram, Onattukara and Kuttanad to study the population dynamics of rice stem borers and leaf folders in South Kerala in relation to biotic and abiotic factors. Field tolerance of different released varieties against rice stem borers and leaf folders and management studies were conducted at Onattukara Regional Agricultural Research Station, Kayamkulam. In addition to the common species of stem borer and leaf folder in rice, the white stem borer S. innotata was recorded from Onattukara and Kuttanad and the leaf folder species M. patnalis from Thiruvananthapuram and Onattukara. The lowest stem borer and leaf folder damage in rice was recorded in Kuttanad at 75 and 90 DAS respectively in southern Kerala. The major natural enemies recorded were the predators viz. dragonflies, damselflies, coccinellids and spiders and parasitoids viz.Cotesia sp, Isotima sp. and Tetrastichus sp. The rice varieties Samyuktha and Onam recorded significantly low stem borer infestation and Makom significantly low infestation by leaf folders. The highest phenol content was estimated in the rice variety Onam both at vegetative and flowering stages and highest silica content in Supriya and Sreyas. The bio-pesticides viz. 1% azadirachtin 0.003%, dasagavya 3%, cashewnut shell liquid 0.1% and T. japonicum and T. chilonis each 1 lakh ha-1 are effective in controlling stem borer and leaf folder infestation and safe to natural enemies. Significantly high grain yield and highest marginal benefit: cost ratio was recorded in the treatments chlorantraniliprole 18.5 SC 0.005% and 1% azadirachtin 0.003%. This study leads to the future investigations on identification of new species of stem borers, leaf folders and associated natural enemies. Breeding programmes can be taken up with tolerant varieties and management of these pests with new bio-pesticides can be done.Item Marker assisted backcross breeding in rice variety jyothi for drought tolerance(Centre for Plant Biotechnology and Molecular Biology, College of Agriculture, Vellanikkara, 2024-01-03) Shankar, C.; Abida, P SDrought is one of the important abiotic stressors that can substantially reduce rice production by 35 - 40 per cent. Water stress will significantly impact the growth and development of rice crops, but drought at the reproductive stage will directly affect the grain yield. In 2018, the State Disaster Management Authority, Kerala declared major rice growing districts including Palakkad and Alappuzha as drought affected. Jyothi is a high-yielding popular rice variety, widely cultivated variety across Kerala. Despite its widespread popularity, it exhibits poor spikelet fertility per cent under water deficit conditions, indicating that it is susceptible to drought. Considering the negative impact of drought stress on rice production and the losses incurred by farmers, efforts were initiated at the College of Agriculture, Vellanikara to pyramid QTLs (qDTY4.1, qDTY6.1, and qDTY9.1) for yield under drought into the rice variety Jyothi (recurrent parent) from the drought tolerant variety Chuvannamodan (donor parent). The present work was conducted during 2021-2023 with the objective of introgressing the target QTLs of interest into variety Jyothi through marker assisted backcross breeding. Genomic DNA was isolated from both parents and subjected to PCR amplification for parental polymorphism using a set of 208 microsatellites. Out of which, 85 markers were found to be polymorphic between the parents. Parental varieties were hybridized and resultant F1 hybrids were confirmed using foreground markers (RM518, RM587 and RM566). A total of 27 F1 hybrids showed heterozygous banding pattern for all foreground markers. The F1 hybrids were backcrossed with recurrent parent for the production of the BC1F1 population. Also, F1 hybrids were allowed to selfing for the production of F2 and subsequently F3 generation. Gene annotation and enrichment analysis were done using Simple Sequence Repeat (SSR) markers associated with the target QTLs of interest. It was found that 23 genes were associated with drought tolerance, spikelet fertility and root related traits at three different QTL regions. Foreground selection in 200 BC1F1 progenies along with the parents was done to identify the plants with the target QTLs. SSR markers RM518, RM587 and RM566 closely linked with qDTY4.1, qDTY6.1 and qDTY9.1, respectively were used as foreground markers. Screening of BC1F1 population revealed that 60 progenies possessed heterozygous alleles for at least one QTL. A total of 27 BC1F1 progenies including 10 with qDTY4.1 + qDTY6.1, 9 with qDTY6.1 + qDTY9.1 and 8 with qDTY9.1 + qDTY4.1 were identified to possess two QTLs pyramided. Background selection of 27 BC1F1 foreground selected progenies using 76 SSR markers, polymorphic between the parents, revealed the presence of wide variability among these progenies with respect to recurrent parent genome recovery (RPGR). The results of graphical genotyping revealed a maximum RPGR of 57.7 per cent in the BC1F1 progeny 24.165, followed by 56 per cent in progeny 1.2. Drought tolerance of 15 BC1F1 with two QTL combination along with the parental varieties was characterized under reproductive stage drought stress using thirteen traits as per standard evaluation system (IRRI, 2002), including water mining traits. All the backcrossed progenies exhibited better performance under water deficit condition than the susceptible parent, Jyothi. It was found that progeny 20.118 (qDTY4.1 + qDTY6.1) had a higher number of filled grains (FG) per panicle (41) and spikelet sterility (SS) per cent (49.38 %) compared to Jyothi with 1 FG and 99.29 % SS under drought. The progeny 1.10 (qDTY9.1 + qDTY4.1) possessed higher root length (97 cm), root volume (100 cc), root to shoot ratio (1.70), root dry weight (25.9 g) than Jyothi (82.2 cm, 76 cc, 1.4, 14.64 g). Also, progenies 23.153 (qDTY4.1 + qDTY6.1) and 3.30 (qDTY6.1 + qDTY9.1) exhibited delay of 8 days to show the leaf rolling symptoms than Jyothi with 4.2 days. The BC1F1 progenies positive in foreground selection was backcrossed with the recurrent parent and 87 BC2F1 seeds were harvested. The resultant BC2F1, BC1F2 and F3 lines with potential drought tolerant QTLs can serve as the base population for enhancing the drought tolerance in Jyothi. Further, genotypic and phenotypic evaluation of the QTL pyramided progeny in subsequent generations will lead to the development of drought tolerant cultivar in the background of popular rice variety Jyothi.