PhD Thesis
Permanent URI for this collectionhttp://localhost:4000/handle/123456789/48
Browse
4 results
Search Results
Item Nitrogen use efficient varieties for enhanced productivity in rice (Oryza sativa L.)(Department of Agronomy, College of Agriculture, Vellayani, 2025-07-29) Merin Jose; Shalini Pillai, PThe research entitled “Nitrogen use efficient varieties for enhanced productivity in rice (Oryza sativa L.)” was conducted at the Department of Agronomy, College of Agriculture, Vellayani, during 2021 to 2025. The objectives of the study were to screen selected rice varieties for nitrogen use efficiency (NUE) based on germination and root characteristics, to evaluate the field performance of selected nitrogen-efficient rice varieties at graded doses of nitrogen (N), and to work out the economics. The study was conducted in three parts. The first part was a lab study wherein, 14 popular rice varieties released from Kerala Agricultural University (KAU) were screened for NUE based on germination characteristics. The experiment was laid out in completely randomized design (CRD) with 14 varieties and 5 media, replicated thrice. The treatments comprised seven short duration varieties (SDVs) viz., v1- Makom (MO 9), v2- Prathyasa (MO 21), v3- KAU Manuratna, v4- Jyothi (PTB 39), v5- Harsha (PTB 55), v6- Varsha (PTB 56) and v7- Kanchana (PTB 50) and seven medium duration varieties (MDVs) viz., v8- Bhadra (MO 4), v9- Uma (MO 16), v10- Sreyas (MO 22), v11- Pournami (MO 23), v12- KAU Manuvarna, v13- Athira (PTB 51) and v14- Aiswarya (PTB 52), and Modified Arnon Hoagland (AH) media [(m1- AH media with urea (7.5 mM), m2 - AH media with ammonium chloride (15 mM), m3- AH media without N source, m4- AH media and m5 - distilled water]. In general, the presence of urea or any other additional source of N tends to inhibit germination. However, this inhibitory effect was not observed in the case of Harsha (v5) and Varsha (v6), as both varieties took 39 h each to reach 50 per cent germination in distilled water and in AH media with urea. In the case of MDVs, the germination of all the varieties were inhibited. The SDVs, viz., Varsha (v6), Harsha (v5) and Prathyasa (v2) had longer shoots (10.25 cm ± 1.27 cm, 7.95 cm ± 0.52 cm and 6.63 cm ± 0.79 cm respectively) in the presence of urea as compared to distilled water. In the case of MDVs, Aiswarya (v14), Athira (v13), Sreyas (v10) and Uma (v9) produced longer shoots (9.20 cm ± 0.36 cm, 8.20 cm ± 0.39 cm, 8.13cm ± 0.85 cm and 6.53 cm ± 0.75 cm respectively) in the presence of urea as compared to distilled water. In the presence of urea, Varsha (v6) and Harsha (v5) recorded longer roots (9.13 cm ± 1.91 cm and 9.03 cm ± 2.78 cm). With respect to MDVs, Sreyas (v10) recorded longer roots (12 cm ± 0.28 cm) and this was on par (11.73 cm) with that under distilled water. Higher seedling dry weight (23.15 mg ± 2.25 mg) was recorded in Varsha (v6) which was on par with Kanchana (v7), Harsha (v5) and Jyothi (v4). In the presence of urea, Uma (v9) recorded higher seedling dry weight (23 mg ± 1.83 mg) which was on par with Aiswarya (v14), Sreyas (v10) and KAU Manuvarna (v12). Urease enzyme activity was found to be the highest (0.59 ± 0.01) mM NH4+ min-1 g-1 in Varsha (v6) followed by Harsha (v5). A similar trend was observed in urea and NH₄Cl, where Varsha (v6) recorded higher urease enzyme activity than Harsha (v5). In case of MDVs, urease enzyme activity was the highest (0.47 ± 0.01) mM NH4+ min-1 g-1 in Aiswarya (v14) followed by Sreyas (v10). Seedling vigour index I (SVI I) was higher in Varsha (v6) followed by Harsha (v5) and higher seedling vigour index II (SVI II) was recorded by Kanchana (v7), followed by Varsha (v6) and Harsha (v5). In case of MDVs, Aiswarya (v14) recorded higher SVI I (885.15), followed by Sreyas(v10) (717.28). Whereas, Sreyas (v10) recorded higher SVI II (2288.25) which was followed by Aiswarya (v14) (2278.50). The second part of the study comprised screening the 14 rice varieties in field, under two contrasting N levels. It was carried out in the wetlands of the Integrated Farming System Research Station (IFSRS), Karamana, during June to October 2023. The experiment was laid out in randomised block design (RBD) with the 14 varieties at two levels of nitrogen (n0- 0 % RDN and n1- 100 % RDN), replicated thrice. Among the SDVs, Harsha (v5) and Varsha (v6) and among MDVs, Sreyas (v10) and Aiswarya (v14) proved superior in terms of growth attributes including plant height, tillers m-2, rooting depth and root volume. The same trend was observed in yield attributes and yield. The lower percentage in yield reduction observed in Harsha (23.89%), Varsha (22.50%), Sreyas (27.89%) and Aiswarya (20.61%) at zero per cent RDN compared to 100 per cent RDN pointed towards their higher NUE. These varieties also exhibited higher root dry weight efficiency index (RDWEI) which is also an indicator of NUE. The Partial factor productivity of N (PFPN) also exhibited a similar trend. Based on the cumulative ranking of germination traits (part I) and RDWEI, yield and PFPN (part II) the varieties Harsha, Varsha, Sreyas and Aiswarya were chosen as promising candidates for further field evaluation aimed at validating their production potential, NUE and profitability. The third part of the study entitled ‘Field evaluation of nitrogen- efficient rice varieties’ was also conducted at IFSRS, Karamana from November 2023 to February 2024 (second crop 2023-’24 referred to as season I) and July to November 2024 (first crop 2024 ’25 referred to as season II). The field performance of the four nitrogen-efficient rice varieties chosen from part I and part II were assessed at graded levels of recommended dose of nitrogen (RDN). The experiment was laid out in split plot design with four main plots (n1- 100 % RDN, n2 - 75 % RDN, n3 - 50 % RDN and n4- absolute control) and four sub plots [v1- Harsha (PTB 55), v2- Varsha (PTB 56), v3- Sreyas (MO 22) and v4- Aiswarya (PTB 52)], replicated four times. The results revealed that during seasons I and II, while Harsha at 100% RDN (n1v1) recorded the highest grain yield (4567 kg ha-1 ± 64 kg ha-1 and 4703 kg ha-1 ± 35 kg ha-1 respectively), the yield of Varsha at 100% RDN (n1v2) (4507 kg ha-1 ± 81 kg ha-1 and 4720 kg ha-1 ± 89 kg ha-1) and 75 per cent RDN (n2v2) (4440 kg ha-1 ± 82 kg ha-1 and 4603 kg ha-1 ± 68 kg ha-1) were statistically comparable. The MDVs, Sreyas and Aiswarya also behaved in a similar manner with comparable yields at 100 per cent RDN and 75 per cent RDN. Chlorophyll content was significantly the highest at 100 % RDN in Harsha, Varsha and Sreyas throughout the growth stages. Whereas in Aiswarya, the chlorophyll content at 100 per cent RDN was statistically comparable to that at 75 per cent RDN. In terms of NUE indices, all the four varieties exhibited significantly higher PFPN and agronomic efficiency of nitrogen (AEN) at 50 per cent RDN. However, during season II AEN of both Varsha and Aiswarya at 50 per cent RDN and 75 per cent RDN were comparable. Harsha recorded the highest BCR (1.41± 0.02 and 1.45± 0.01) at 100% RDN (n1v1), while, Varsha recorded the same (1.42 ± 0.03 and 1.49 ± 0.02) at 75 per cent RDN (n2v2). Among the MDVs, Sreyas and Aiswarya recorded higher BCR at 75 per cent RDN. Screening of 14 popular rice varieties released from KAU based on germination characters, RDWEI and PFPN showed that the short duration varieties viz., Harsha (PTB 55) and Varsha (PTB 56) and the medium duration varieties viz., Sreyas (MO 22) and Aiswarya (PTB 55) could be considered as nitrogen efficient. Field evaluation of the nitrogen efficient varieties showed that while the productivity and profitability of Varsha could be sustained at 75 per cent RDN, the variety Harsha required 100 per cent RDN. The study also revealed that, the recommended dose of N (90 kg ha-1) for the nitrogen efficient MDVs, could be reduced by 25 per cent without compromising yield and profitability.Item Expression profiling of genes associated with nitrogen use efficiency in rice varieties under organic and conventional management(Department of Molecular Biology and Biotechnology, College of Agriculture, Vellayani, 2024-05-02) Elizabeth Jose; KAU; Soni, K BThe study entitled “Expression profiling of genes associated with nitrogen use efficiency in rice varieties under organic and conventional management” was conducted in the Department of Molecular Biology and Biotechnology during 2019-2023. The objectives of the study were to identify differentially expressed genes associated with nitrogen use efficiency (NUE) in rice varieties under organic and conventional management and to find out the polymorphism in the gene sequences. A pot culture experiment was conducted in a completely randomized design with five replications. Four rice varieties namely Jaiva, Ezhome 2, Uma and Jyothi were compared under two nutrient management practices (KAU PoP, Adhoc Organic PoP of KAU) along with an absolute control. Under organic management, nutrients were applied on N equivalent basis. The observations on morphological, physiological, biochemical and yield parameters and expression of genes associated with NUE were taken at seedling, panicle initiation and grain filling stages. All rice varieties showed significantly taller plants, greater number of tillers per hill, higher grain and straw yields per hill with KAU PoP. Jaiva and Ezhome 2 showed a significantly greater number of productive tillers per hill (P=0.001 and P=0.02) under KAU PoP, and Ezhome 2 produced higher filled grains per panicle under organic PoP. Jyothi showed significantly higher root depth and root biomass per hill (46.34 cm, 18.6 g) under organic PoP. At the vegetative stage, all varieties except Jaiva and Uma, exhibited significantly higher photosynthetic rates under KAU PoP. The varieties Ezhome 2 and Uma showed higher leaf protein content under organic PoP. All rice varieties, except Ezhome 2, showed significantly higher amino acid content under KAU PoP. The nutrient management practices did not significantly affect the reducing sugar content in Jyothi, compared to other varieties which showed higher values under KAU PoP. All the varieties showed higher NUE with KAU PoP than organic PoP. Maximum NUE was seen in Jyothi (0.28 kg yield increase/g N applied) under KAU PoP. Variation in NUE under both nutrient management was found to be lesser in the variety Jaiva (23.8%). 195 Expression profiles of NUE-associated genes such as OsNRT1.1a, OsNRT1.1b, OsAMT1.1, OsAMT1.2, OsAMT1.3, OsNRT2.1, OsNAR2.1, OsGS1.1, OsNADH-GOGAT1 were analyzed at different stages of growth by performing RT-qPCR using SYBR Green dye and β-actin as the reference gene. At the three-week seedling stage, ammonium uptake and transporter genes OsAMT1.1, OsAMT1.2, and nitrate uptake and transporter gene OsNRT2.1 which are root-specific in nature, exhibited significantly higher expression under organic PoP in Jaiva and Jyothi. Jyothi also showed a significantly high expression of glutamine synthase gene, OsGS1.1 in the leaf and root tissues (0.72 and 8.28 folds respectively). OsNADH-GOGAT1, a gene associated with nitrogen assimilation exhibited significantly higher expression in the root tissues of all rice varieties, except Jaiva under organic PoP. At the panicle initiation stage, Uma and Jyothi showed comparatively higher expression of OsNRT1.1a, OsNRT1.1b, OsAMT1.1, OsAMT1.2, OSAMT1.3, OsNRT2.1, OsNAR2.1 and OsNADH-GOGAT1 under organic PoP. At the grain-filling stage, Uma showed significantly higher expression of OsAMT1.1 (3.19 folds), OsAMT1.2 (5.24 folds), OsAMT1.3 (7.65 folds), OsNAR2.1 (11.02 folds), OsNADH-GOGAT1 (2.2 folds) in root tissues under organic PoP. Jyothi, under organic management, showed significantly higher expression of the OsNRT2.1 gene (6.95 folds) in root tissues. In Jaiva, nitrogen assimilatory genes like OsGS1.1 and OsNADH-GOGAT1 showed higher expression in leaf and root tissues under PoP and for Jyothi, they were found elevated (P<0.005) under organic PoP. The full-length sequencing of differently expressed OsAMT1.1 of Jaiva yielded a sequence comprising 2671 bp. This is the initial comprehensive gene sequencing report for the OsAMT1.1 gene of an organic rice variety. It showed a similarity (99.7%) to that of NERICA L19 (O. sativa × O. glaberrima). Uma exhibited an insertion of 41 bp in the promoter region compared to the other three varieties. Furthermore, some single nucleotide polymorphisms were also identified in the promoter region of Jaiva, Ezhome, Uma and Jyothi. In conclusion, the present study explored the response of the key genes involved in the uptake, transport and assimilation of nitrate and ammonium under different nutrient management strategies in determining nitrogen use efficiency in rice varieties. 196 Jaiva and Jyothi exhibited superior efficiency in both nitrate and ammonium uptake, correlating with higher NUE and narrower yield gaps between organic and fertilizer-based management. In the initial stages of crop growth, an elevated expression of OsAMT1.1 and OsAMT1.2 was seen in Jaiva and Jyothi under organic management, whereas OsAMT1.3, which has a N-derepressible role was highly expressed in Uma under organic management. The variety, Uma was found to be less nitrogen-efficient and was highly influenced by ammoniacal fertilizer. Even though OsAMT1.1 and OsAMT1.2 were less expressed in the initial stages of Uma, a significant increase was observed in its later stages. OsNRT2.1 and its partner protein OsNAR2.1, which are important in regulating nitrate transport and signaling, were upregulated in Jaiva and Jyothi under organic PoP, influencing root development and contributing to superior agronomic use efficiency. The higher expression of OsGS1.1 in the seedling and grain filling stages of Jyothi under organic PoP contributed to grain development and filling, demonstrating better NUE and a reduced yield gap. Ezhome 2, by exhibiting higher OsGS1.1 expression at the seedling stage, displayed increased filled grains, emphasizing the significance of early gene expression in yield determination. Furthermore, OsNADH-GOGAT1's role in ammonia assimilation, productive tiller formation, and grain development was evident, with varieties like Ezhome 2 showcasing its positive impact on grain number and tiller productivity under organic PoP. The findings highlight the complexity of nitrogen response and metabolism in rice and emphasize the importance of nutrient management strategies in achieving optimal NUE and crop yield. The observed variations in the gene expression across different varieties and growth stages provide a foundation for further research and potential molecular interventions to enhance NUE in rice.Item Nutrient- moisture interaction under phasic stress irrigation of sweet potato in summer rice fallows(Department of Agronomy, College of Agriculture,Vellayani, 1994) Muraleedharan Nair, G; Muraleedharan Nair,VA field experiment on sweet potato was laid out in the rice field fallowed during summer season at the Instructional Farm, College of Agriculture, Vellayani. The study was intended to work out of the irrigation schedule and fertilizer practice for sweet potato grown as a catch crop during the summer season of 1990 and 1991. The experiment was designed to economise the use of irrigation water as well as fertilizers by inducing phasic stress at certain phases of plant growth which are considered critical for sweet potato. The field experiment was laid out in a strip plot design replicated thrice with irrigation in horizontal strips and fertility levels in vertical strips. Irrigation water at full CPE was given during tuber initiation phase (10-30 DAP), full CPE at tuber maturity phase (80-100 DAP) and full CPE at tuber initiation and tuber maturity phases. The crop received irrigation at ½ CPE during the rest of the period of plant growth. Nitrogen and potassium were applied @ 25, 50 and 75 kg ha-1 and a uniform dose of P2 O5 @ 50 kg ha-1 and lime @ 500 kg ha-1 were applied. A control plot that received NPK @ 75:50:75 kg ha-1 and FYM @ 10 t ha-1 was maintained for treatment comparison. Growth characters were recorded at an interval of 21 days from planting and it was observed that providing irrigation at full CPE during tuber initiation phase resulted in significant increase in vine length and number of leaves plant-1. Enhanced rate of application of Nitrogen promoted the growth of vines, number of branches plant-1 and number of leaves produced plant-1. Potassium did not exert any influence on these growth characters. Growth analysis studies showed that the LAI was maximum in plots that received irrigation at full CPE during tuber initiation phase. Nitrogen substantially influenced the LAI, higher levels being significantly superior to the lower levels. Higher levels of potassium also influenced the LAI. The NAR and specific leaf weight were the highest in plots that received irrigation at ½ CPE during tuber initiation phase. Both NAR and CGR were high in the early stage of plant growth and decreased towards harvest. Increased rates of nitrogen supply decreased the NAR and specific leaf weight whereas no definite trend could be observed on CGR> Higher levels of potassium had a favourable influence on NAR and CGR. The dry matter of leaves, shoots, fibrous roots and tubers were significantly enhances by providing full CPE during tuber initiation phase. Increasing the level of nitrogen, influenced the dry matter in the aerial parts. The influence of K on dry matter production was not consistent. Tuber bulking rate showed a positive trend under irrigation at full CPE during tuber initiation phase. Nitrogen levels at 50 and 75 kg ha-1 had an overlapping influence on tuber bulking rate and both remained superior to 25 kg ha-1. Scheduling of irrigation did not exert any influence on the length and girth of tuber. However, an increase in the length and a corresponding decrease in the girth were noticed at enhanced rates of nitrogen supply. The number of tubers plant-1 showed a significant improvement by providing irrigation at full CPE during tuber initiation phase. The total number of tubers plant-1 was increased by high rates of N, but did not influence the number of marketable tubers. Application of K at 50 kg ha-1 promoted the production of more tubers. Tuber yield was significantly influenced by irrigation wherein providing full CPE during tuber initiation phase resulted in superior yield of both total and marketable tubers. Tuber yield was maximum at 50 kg ha-1 each of nitrogen and potash. Vine yield was significantly enhanced by higher rates of applied nitrogen. The harvest index and utilization index were enhanced by the application of irrigation water at full CPE during tuber initiation phase. Application of N at 25 kg ha-1 resulted in the production of high starch content whereas the sugar content was increased upto the highest level of 75 kg ha-1. The uptake of nitrogen by vines and tubers showed a progressive increase by applying full CPE during tuber initiation phase. Application of higher levels of nitrogen invariably promoted the uptake of N, P and K by the plant. Application of potash at 50 or 75 kg ha-1 also resulted in higher uptake of potassium. The fertility status of the soil did not show a positive trend by scheduling of irrigation. The plots that received the lowest dose of nitrogen, invariably recorded the highest level of available phosphorus. Available potassium content was also high in plots that received higher rates of potash. Irrigation at full CPE during tuber initiation and/or tuber maturity phase recorded significantly higher water use efficiency and net returns as compared to including stress during tuber initiation phase. Nitrogen and potash both at 50 kg ha-1 recorded the maximum water use efficiency and net returns from sweet potato cultivation.Item Deficiency symptoms of mineral nutrients in clove (Syzygium aromaticum (L.) Merr. and Perry).(Department of Plantation Crops and Spices, College of Horticulture, Vellanikkara, 1989) Nazeem, P A; Sivaraman Nair, P CExperiments were conducted at the College of Horticulture on nutritional aspects of clove, to study the nutrient deficiency symptoms as well as the distribution pattern of nutrients in starved clove plants. The deficiency symptoms were induced in clove seedlings in sand culture. The distribution pattern of P, S (anions) and Ca (cation) were studied in the nutrient-starved seedlings employing radio isotopes. Besides, the annual nutrient removal and the seasonal fluctuations in the foliar nutrient concentration were studied in bearing clove trees. Older leaves were the first to exhibit 'hunger signs' due to the stress induced by N, P, K and Mg starvation whereas the symptoms, were manifested on the younger growth due to deficiency of Ca, S, Fe, Mn, Cu, Zn and B. General yellowing of the older leaves and early defoliation were the symptoms expressed by N-starved plants. Phosphorus stress resulted in small brownish spots to appear on older leaves of clove seedlings which later coalesced to form necrotic patches.