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Central Agricultural University, College of Post Graduate Studies in Agricultural Sciences, Umiam
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ThesisItem Open Access Development of native Rhizobium compatible enriched compost for use in Lentil (Lens culinaris Medik.) grown in Acid Soil.(College of Post Graduate Studies in Agricultural Sciences, CAU-Imphal, Umiam, 2018-09) Sangma, Christy Berylnight K.; Thakuria, DwipendraThe benefit of Rhizobium inoculation in pulse crops grown near neutral to slightly acidic soils is well known. The promotion of pulse crops, especially lentil (Lens culinaris Medik.) in acid soils of North East India is very challenging due to poor nodulation efficiency and nitrogen fixation in strongly acid soils. Out of several causes, the development of acidity tolerant Rhizobium strain and build-up of Rhizobium population near the germinating seeds (spermosphere) in acid soils are challenging tasks. This investigation aimed at the development of effective native Rhizobium leguminosarum strain tolerant to acid soil and delivery of the effective Rhizobium strain through enriched compost to the soil. In order to prepare enriched compost, effective cellulose degrading bacteria (CDB) were screened and the most effective one used for preparation of compost followed by its enrichment by application of efficient Rhizobium strain and phosphate solubilising bacteria (PSB) along with rock phosphate (RP). Cellulose degrading bacteria were isolated from the forest floor litters of jhum cycles 2, 5, 10, and 20 years using cellulose agar medium (CAM) and were screened for cellulase activity in agar plates containing carboxy-methyl-cellulose (CMC) as substrate. Out of 32 CDB isolates, the most effective one (CDM-C1) was used for enrich compost preparation. Pea plant grown in 4 soil types (organic farm plot of ICAR, Umiam; Monabari, Garo Hills; Soils from Upland Lowland of CPGS farm fields) were screened for nodules. R. leguminosarum bv. viceae isolates were grow non Yeast Extract Mannitol Agar (YEMA). R. leguminosarum isolates were further confirmed on CRYEMA containing congo red. Four native Rhizobium isolates (NR1, NR2, NR3 and NR4) including one reference exotic strain (ER), Rhizobium leguminosarum CK1 (obtained from AINP Solan Centre, Dr. YSPUH & F, Solan, HP,India) were screened for nodulation efficiency and yield enhancement on lentil crop grown in a pot experiment using an acid soil (pH 5.25). The treatment combinations of the pot experiment were: (1) SRE 1: negative control (no Rhizobium inoculation)+50%RDF (@ 10:30:10 kg N-P-K ha-1), (2) SRE 2: positive control(CK1)+50% RDF, (3) SRE 3: NR1+50%RDF, (4) SRE 4: NR2+50%RDF, (5) SRE 5:NR3+50%RDF and (6) SRE 6: NR4+50%RDF. The treatment SRE4 (native Rhizobium NR2) performed best in terms of plant height, no. of branches, nodulation efficiency and yield compared to other treatments (P≤0.05, one-way ANOVA). Inoculum of the most effective CDM-C1 isolate was applied into mixed biomass (Eupatorium spp., Ambrosia spp. and broom grass and crop residues like rice straw, maize stalk and banana leaves) for preparation of compost in standard pits (each pit size was 1m x 1m × 1m) by imposing 5 treatments: (1) Normal compost 1 (EC1), (2) enriched compost (EC 2): RP+PSB compost, (3) enriched compost (EC 3): NR2 compost (4) enriched compost (EC 4): RP+PSB+NR2 compost, and (5) enriched compost (EC 5): RP+PSB+ER(CK1) compost. The compost quality and nutrient contents (E4/E6, ash content and alkalinity, germination percentage and index, N, Pand K content, pH and EC) values indicated that EC4 and EC5 composts were better than EC1 and other enriched compost. A field experiment on lentil crop (variety PL-8)was conducted in the ICAR Experimental Farm, Umiam with 9 treatments combination:T1: 100% RDF (@20:60:20 kg N-P-K ha-1), T2: 50% RDF, T3: seed inoculation (SI) with NR2+EC 1+50% RDF, T4: SI with ER (CK1)+EC 1+50% RDF, T5: SI with NR2+EC 2+50% RDF, T6: SI with ER (CK1)+EC 2+50% RDF, T7: SI with NR2+EC 4+50% RDF, T8: SI with ER (CK1)+EC 5+50% RDF, T9: SI with NR2+ EC 3+50% RDF. The nodulation efficiency was the highest in T5 followed by T7. Pod and seed yield were the highest in T5 followed by T7 and these treatments received enriched compost amended with native Rhizobium (NR2), PSB and RP. Overall, it can be concluded that enriched compost amended with native Rhizobium, PSB and RP showed great potential in supporting higher nodulation efficiency and yield of lentil crop grown under acid soil. Key words: Cellulose decomposer; Jhum; native Rhizobium; Acid soil; Pulse promotion; Lentil.ThesisItem Embargo Genetic analysis of RILs for Al stress tolerance in Lentil (Lens culinaris Medik.) under acidic soils of Meghalaya.(College of Post Graduate Studies in Agricultural Sciences, Central Agricultural University - Imphal, 2022-12) Mahanta, Mayurakshee; Singh, K. NorenLentil (Lens culinaris ssp. culinaris) popularly known as “Masoor” in India, is an important pulse crop used both as food and feed because of its protein-rich seeds and straw. There is immense potential to increase area under lentil cultivation in NEH Region including Meghalaya attributing to suitable climatic factors. However, the soils of NEH Region including Meghalaya are acidic in nature where Aluminium (Al) stress becomes one of the prime limitations for production of crops specially pulses like lentil, as Al solubilizes into phytotoxic forms at low pH, explicitly below 5.0, causing root growth inhibition, reduced plant vigour and finally reducing grain yields to large extents. The present study involved screening for Al stress associated chromosomal regions and markers. tolerance in a RIL population of lentil developed from a cross between BM- 4 (Al sensitive parent) and L- 4602 (Al tolerant parent) through phenotypic evaluation in the field, root growth studies, organic acid exudate analysis under hydroponics and molecular studies to identify The variance analysis combined over two locations revealed highly significant genotype x location interaction for the traits under study except DM, NPB and SPP, whereas variance due to genotypes was highly significant for all the 10 characters. Among all the characters, high Hbs2 coupled with high GA% were observed in NPB, PH and 100 SW which suggested preponderance of additive gene effects in the inheritance of these traits. A highly positive and highly significant correlation was observed between SYP with PPP (0.84**), BYP(0.79**), SPP (0.47**) and NPB (0.30**) and a positively significant correlation with 100 SW (0.1955*). Path analysis revealed that, PPP (0.840) had the greatest direct effects in influencing SYP, followed by BYP (0.795), SPP (0.474), NPB (0.309) and HI (0.307) suggesting the importance of improving SYP by selecting these traits. ANOVA for root and shoot traits screened under hydroponics culture treated with Al (148μM) revealed presence of highly significant genotypic differences for all the traits. High GCV coupled with high H2bs and GA% were observed for RRG, RL, RFW, SFW, RDW, TRL, TRSA and TRV. Also, RRG showed highly significant positive correlation with SYP. Analysis of organic acid exudation from roots of lentil in response to toxic level of Al (148μM) led to identification of citric acid, malic acid, oxalic acid and fumaric acid in the root exudates. Citric acid was exudated in highest amount in all the genotypes, while it was observed that most of the tolerant genotypes exudated more organic acids as compared to sensitive ones. Citric acid was found to be positively and significantly correlated with RRG and seed yield. SSR based genotyping of extreme RILs having contrasting response to Al toxicity identified the markers significantly associated with more than one trait viz. PBA_ LC_1247 with RRG and TRSA, PLC_104 with RRG, TRL, TRSA, TRV and SYP, LcSSR 17 with RRG and TRL, PLC_ 91 with TRL, TRSA, SYP, PBA_LC_327 with TRL, TRSA, TRV, PBA_LC_118 with TRL, TRSA, PBA_LC_1401 with TRL, TRSA and TRV and PLC_46 with Root Al content and SYP. Considering the presence of positive alleles for majority of the associated markers, explaining more than 10% of trait variations (R2) and based on all the phenotypic screening methods the RILs identified as high yielding and Al tolerant are LRIL-92, LRIL-96, LRIL 97, LRIL-109, LRIL- 143, LRIL-144 and LRIL-148. It was observed from our study that, for root re-growth, total root length and root Al content, the associated chromosomal regions were located on chromosome 1 and chromosome 4; while for total root volume and seed yield per plant the associated regions were located on chromosome 1 and chromosome 3; and for total root surface area the associated regions were located on chromosome 1, suggesting that chromosome 1, chromosome 3 and chromosome 4 of lentil harbours the regions or QTLs that are associated with tolerance to Al toxicity stress in lentil. With further evaluation these RILs may serve as important Al toxicity tolerant varieties suitable for acidic soil conditions of Meghalaya. Also, these lines can be used as parents for generating new crosses for further genetic studies. The markers identified as associated with Al tolerance may facilitate in marker assisted selection programmes for developing Al tolerant varieties.ThesisItem Embargo Value chain analysis of bamboo in North Eastern Region of India(College of Post Graduate Studies in Agricultural Sciences, Central Agricultural University - Imphal, 2022-09) Gogoi, Jeemoni; Singh, RamBamboo is a naturally distributed evergreen perennial flowering plant belonging to the grass family Poaceae (Li and He, 2019).Trading in value-added products of bamboo has the potential to make positive contribution to the global environment and economy. The North Eastern Region (NER) of India along with West Bengal contributes half of the bamboo area of the country and bamboo craft has been practiced in NER for centuries as their prime livelihood and income source. For realizing bamboo’s full potential as a driver of environmental sustainability and inclusive economic growth, a fundamental shift in the current system is required. It has become necessary to examine the markets in terms of value addition, involvement of actors and quality requirements. Therefore, the study was carried out with the specific objectives (i) to study the utilization pattern of bamboo (ii) mapping of value chain actors in bamboo and its products (iii) estimation of compliance cost, investment and return involved in value chain of bamboo (iv) to assess the impact of value chain of bamboo on livelihood and income of different stakeholders in the state of Assam and Meghalaya. The study was conducted with primary data from Assam in Barpeta and Nalbari district with a total respondent of 130 and 150 respectively, and in Meghalaya, a total of 53 and 47 respondents were selected from East Khasi Hills and Ri- Bhoi district, respectively. To fulfil the above objectives, utilization of bamboo was classified into five categories; value chain map was prepared with identification of actors involved. The compliance cost, marketing margin, price spread, percentage change, Lorenz curve and Gini coefficient were estimated for the stakeholders. The results showed that the maximum quantity (84.50%) of bamboo has been utilized by the respondents for building and scaffolding purposes. The raw bamboo in Assam mainly marketed outside the state through channel-I (Pole collector →Traders→ Other states of India) (46.43%) in Assam, while in Meghalaya, it was through channel-II (Pole Collector→ Traders (Assam/Shillong)) (81.35%). In Assam, five channels were identified for bamboo products and maximum quantity (49.24%) was marketed in channel-IV (Artisans→Trader-cum-Wholesaler-cum-Producer→ Outside Assam) whereas, in Meghalaya majority of the product (90.39%) was sold off through channel-I (Artisans→ Village merchant→ Wholesaler-cum-Retailer→ Consumer). The bamboo shoots were marketed only in Ri-Bhoi district of Meghalaya through five channels out of which three channels were used for marketing of fermented (pickled) bamboo shoots. Differentiated value added furniture products viz., sofa set, bed, dining table and handicrafts and traditional products (Japi, Duli and Khorahi) were marketed in Assam while in Meghalaya handicraft and traditional products (Polo and Khoh) were marketed. In Barpeta and Nalbari districts, the price spread was found to be higher in channel-I and channel-V, respectively for all the products while in Meghalaya, the maximum price spread was found in channel-I in both the districts for all the bamboo products. Positive impact of bamboo value chain was observed on different stakeholders’ income and expenditure with significant difference in the income distribution assessed through Gini coefficient. Maximum employment was generated at artisan’s level (533 mandays). The study recommends the establishment of bamboo product export zone in the NER with focus on export-oriented bamboo value chain including high value product development viz. laminated bamboo boards, engineered bamboo products, bamboo vinegar, etc. for the improved livelihood of the stakeholders involved in the sector.ThesisItem Embargo Early generation MAS for selecting transgressive segregants carrying Pi9, PSTOL1 and yield related genes in elite X elite crosses of rice(2022-09) Magudeeswari P.; Rai, MayankIn order to enhance rice productivity under acidic soils of North Eastern Hill Region of India, breeding and selection for blast resistance and low P tolerance is most important along with yield component traits. Phenotypic selection in early segregating generations is not considered to be effective due to low to moderate heritability for most of the agronomic traits. However, use of allele specific DNA markers may enhance selection efficiency and heritability, thereby leading to higher genetic gain in a breeding programme. To test this hypothesis, 21 biparental populations developed from 13 parents were subjected to a combination of phenotypic selection along with MAS for PSTOL1 (phosphorus starvation tolerance), Pi9 (a major blast resistance genes), SPIKE (increased spikelet number) and Gn1a (increased grain number). Parental polymorphism survey for allele specific markers while SCM2 was fixed in all parents, DEP1 and OsSPL14 were completely absent. The segregating populations were subjected to early generation (F2) marker-assisted selection for Pi9 (ULRC66, ULRC67) and PSTOL1 (ULRC69) during the offseason and the remaining crosses were subjected to MAS for the abovementioned genes on phenotypically selected lines (kharif 2020). The MAS for PSTOL1 gene on phenotypically selected lines of eight segregating populations (ULRC52, ULRC56, ULRC57, ULRC69, ULRC70, ULRC72, ULRC73, ULRC77) was carried out and the results showed the presence of PSTOL1 significantly increased the tiller number at 60 days in all crosses and grain yield in ULRC56. Further, the segregating lines were evaluated for low phosphorous (P) tolerance under soil micro plot with normal (P+) and stress (P-) conditions. Analysis of variance (ANOVA) revealed the lines were significantly different for all traits and the interaction was found significant for tiller number at 45 days (TN45), spikelets per plant (SPP), filled grains per plant (FGPP), and plant height (PH). Shoot Phosphorus Use Efficiency (PUE) and P Efficiency Ratio (PER) were significantly correlated with biomass and grain yield under stress (minus P) conditions, suggesting that selection for PUE and PER may increase grain yield under low soil P conditions. Simultaneously, to find tolerant genotypes under stress conditions, eight stress tolerance indices (STI, GMP, TOL, SSI, YR, YI, PYR, YSI) were calculated and the data were subjected to PCA and unrooted cluster analysis. The results of PCA showed STI and GMP had positively contributed to PC1, and it revealed STI and GMP can be better indices to discriminate the tolerant and susceptible genotypes. Biplot and unrooted cluster tree clearly showed two groups, in which ULRC52-5, ULRC62-1, ULRC62-5 and ULRC62-SSD-5 were found more stable under both low P and normal conditions. MAS for Pi9 was carried out on four F2 populations (ULRC64, ULRC65, ULRC66, ULRC67) and evaluated for leaf blast disease under natural field conditions (kharif 2020 and kharif 2021) and artificial inoculated conditions. The results clearly showed that Pi9 (+ve) plants had recorded a low blast score compared to Pi9 (-ve) plants. From the Pi9 segregating populations, eleven lines carrying Pi9 at a homozygous state with high grain yield per plant were phenotypically selected and they can be used as a donor for Pi9 in future breeding programme. MAS for yield genes i.e., SPIKE and Gn1a was carried out on phenotypically selected lines of five and six segregating populations, respectively. The results showed the genes were significantly associated with high SPP, FGPP and GYPP in some, but not across all populations, suggesting interaction of these genes with genotypic “background” in determining the phenotype. ANOVA of segregating populations revealed the lines were significantly different for all the eleven traits in Kharif 2020 and the lines showed a significant difference for all traits except NP, SF, GYPP and BY in Kharif 2021. Response to selection was highest for ULRC52 (81.9%) followed by ULRC77 (54.2%), ULRC76 (25.2%) and ULRC68 (21%). The genetic gain for grain yield per plant was observed to be highest for ULRC76 (96%), followed by ULRC70 (25%), ULRC52 (13.61%) and ULRC62 (12.35%). Based on the evaluation of F4/F5 progenies the breeding value of parents was calculated and the results showed Maudamani reported a high breeding value for grain yield per plant (17.68) followed by CAUS103 (16.92), HPR2921(15.37) and CAUS107 (14.22). The parents with high breeding value can be used in a breeding programme to increase the genetic gain. The effectiveness of MAS and phenotypic selection were compared among the populations and it was found that mean of phenotypically selected lines was higher than the MAS selected lines. Genotypic selection alone for one or a few loci in early segregating generations may not lead to increased genetic gain compared to a combination of phenotypic and genotypic selection. Based on the presence of desirable alleles and superior performance under acidic soil ULRC52-SSD-2- 3-1, ULRC52-SSD-1-4 1, ULRC57-SSD-2-3-1, ULRC62-SSD-4-4-1 and ULRC62-SSD-5-6-1 lines were selected for further multilocational evaluation.ThesisItem Embargo Evaluation of potential rhizospheric fungal antagonists against banded leaf and sheath blight of maize caused by Rhizoctonia solani f. sp. sasaki (Kuhn.) Exner(College of Post Graduate Studies in Agricultural Sciences, CAU-Imphal, Umiam, 2022-06) Debbarma, Manashi; Rajesh, T.Rhizosphere represents the most dynamic ecosystem providing a close association between plant root and rhizosphere associated microbial communities. Among the microbial communities colonizing the rhizosphere, Rhizospheric Fungi (RF) hold prominent position but are less explored than that of rhizospheric bacteria. RF plays a vital role in agricultural and environmental process as they can impact the ecological balance, plant growth, suppress or stimulate colonization as well as antagonism of plant pathogens. Therefore, the present investigation was aimed to isolate and evaluate the potential antagonists from maize rhizosphere against Banded leaf and Sheath blight of maize caused by Rhizoctonia solani f. sp. sasaki. Through extensive surveys conducted in different maize growing areas of Meghalaya, soil samples were collected from maize rhizosphere region from eight (8) districts viz., Ribhoi, West Garo Hills, North Garo hills, West Khasi Hills, West Jaintia hills, South West Garo Hills, East Khasi Hills and East Jaintia Hills. A total of eighty (80) fungi were isolated and recovered from rhizospheric soil by serial dilution method, of which majority of isolates showed higher inhibition of 50-80% against R. solani, belongs to the genus Trichoderma sp. (20 isolates) followed by Penicillium sp. (18), Aspergillus sp. (10), Phoma sp. (10), Acremonium sp. (6), Fusarium sp. (5), Chaetomium sp. (4), Metarrhium sp. (2) and Pythium sp. (5). Further, eighty (80) isolates were identified based on morphological and microscopic characteristics. Out of twenty (20) Trichoderma isolates, twelve (12) isolates were found most effective based on their antagonistic potential and were selected for further studies based on antimicrobial and plant growth promotion (PGP) traits. Potential Trichoderma (12) isolates were further identified based on molecular method using ITS primers and accession number was obtained from NCBI. In addition to that, systemic fungicides were evaluated against R. solani f. sp. Sasaki using poisoned food technique, of which carbendazim @ 0.1% showed higher inhibition of 94.44% against R. solani f. sp. sasaki. Among these twelve (12) isolates, only one best RF antagonist viz., RF 44 (T. harzianum) as liquid bioformulation was further evaluated for its efficacy against BLSB of maize (R. solani f. sp. sasaki) under field condition. Various mode of bioformulation delivery either as individually or in combination of seed and soil and foliar were evaluated. In total eleven (11) treatments were evaluated, of which the treatment combination of soil + seed + foliar application + liquid was found most effective in managing the disease showing only 29% disease incidence as compared to control which showed 71% disease incidence. In addition to that, yield per plant i.e., 0.65 kg/plant was also found significantly higher as compared to control i.e., 0.32 kg/plant. Therefore, the potential RF antagonist (RF 44) can be used as effective biological control agent against BLSB of maize which further requires field trial under different locations in this region.ThesisItem Embargo Economics of soil conservation in Meghalaya(College of Post Graduate Studies in Agricultural Sciences, CAU-Imphal, Umiam, 2022-08) Tyngkan, Hehlangki; Singh, S. BasantaSoil degradation is described as the rate at which soil quality degrades, leading to a reduction in agricultural yields, as a result of activities primarily driven by human activity. Meghalaya has the wettest environment on the planet, and its high terrain with tiny valleys in between limits the amount of land available for cultivation. Due to unprecedented rainfall and its high intensity, the problem of soil erosion persists in the state. Consequently, soil erosion in the state accelerated by primitive agricultural practices such as jhum and bun. Keeping the above facts in view, the study on the economics of soil conservation in Meghalaya was planned with the objectives: (i) to study the economics of different soil conservation methods vis-à-vis conventional farming (ii) to study the adoption of soil conservation practices by the farmers in the study area (iii) to assess the impact of soil conservation practices on income, employment and equity of farmers in the study area (iv) to derives policy implications for improvement of soil conservation measures in the state. For the study, primary data consisting of 120 adopters and 120 non-adopters of soil conservation were collected from East Khasi Hills and Ri-Bhoi districts. Benefit-cost analysis, binary logistic regression model, paired t-test, Gini index, Lorenz curve; policy documentation and consultation with different agencies were employed to achieve the above defined objectives. The study revealed that, all the adopted soil conservation (SC) measures viz., bench terracing, contour bunding, peripheral bunding, loose boulder bunding and check dam had positive Net Present Value (NPV), B-C ratio more than one and Internal Rate of return (IRR) more than the considering discount factor (10%). Among the various SC, bench terracing had the highest NPV `264515.58) and IRR (24.36%) whereas loose boulder bunding had the highest B-C ratio (1.53). The economics of selected crops between the adopters and non-adopters of SC showed a significant difference over non-adopters in potato, cabbage and carrot with a difference in net return of `19325.44, `11310.22 and `15482.07, respectively. Out of 13 regressors taken into consideration for determining the factors affecting the adoption of SC by the farmers, age, sex, education, farm income, off-farm income, livestock, access to credit and training were significant. In both the adopters and non-adopters’ categories, majority of the farmers belonged in the income group of `30001-`60000 (39.17% and 48.33 % respectively) followed by `60001-`90000 (35.83% and 30.83% respectively). However, adopters had higher income with the difference of `16,723.65 as compared to the non-adopters. The Lorenz curve and Gini index (0.28 for adopters and 0.38 for non-adopters) depicted a comparatively even distribution of income among the adopters. Per farm employment showed a significant difference at 285.95 mandays and 243.18 mandays in adopters and non-adopters, respectively. The priority areas for action identified to improve the adoption of SC measures in the state include building partnerships, up-scaling of SC practices, building community capability, maximum participation in MGNREGA scheme, economic incentives, promotion of conservation agriculture (CA) and promotion of payment for ecosystem services (PES). The overall results on feasibility analysis for various SC measures were encouraging and hence regular awareness programs are necessary to motivate farmers for adopting appropriate erosion control measures in their field to bring positive returns while enhancing the productivity of the soil in long termThesisItem Embargo Heterotic grouping of maize (Zea mays L.) inbred lines developed from landraces of North East Hill Region (NEHR) of India(College of Post Graduate Studies in Agricultural Sciences, CAU-Imphal, Umiam, 2022-09) Rajasekhar, Duddukur; Sen, DevyaniHybrid breeding programs are dependent on successful exploitation of heterosis and the efficiency with which inbred lines can be assigned to opposing heterotic groups. The current study sought to determine the heterotic grouping of locally developed maize inbred lines in order to identify the most efficient grouping method. In all, 160 hybrids obtained by crossing 80 inbred lines with two standard testers (LM-13 and LM-14) in a Line × Tester (L × T) fashion were evaluated along with three checks over two seasons in an alpha lattice incomplete block design. The 80 inbreds were also genotyped with 34 polymorphic SSR markers. Analysis of variance revealed highly significant (P < 0.01) Genotype and Genotype × Environment interaction for all the traits under study. To reduce environmental effects and maximize the correlation between the true and predicted genotypic values, best linear unbiased predictions (BLUP) were calculated. General and specific combining abilities of the parental inbreds/ crosses and genetic distances were determined and followed up by classification of the inbreds into heterotic groups (LM-13 and LM-14) using four different methods- a) Specific combining ability (SCA) effect of grain yield; b) General combining ability (GCA) effects of multiple traits (HGCAMT); c) Heterotic grouping based on general and specific combining ability (HSGCA) for yield; and d) SSR based genetic distance (SSR_GD). A comparison of these grouping methods revealed that the HSGCA and SCA methods were most efficient. There was also a close correspondence among these methods for grouping similar inbreds into the same heterotic group. As determined by the SSR_GD method, the genetic distance between the divergent testers LM 13 and LM 14 was maximum (1.079) for the material under study. A full diallel analysis (Griffing’s Model 1 Method 1) in a subset of inbreds studied revealed significant GCA and SCA mean square values for all ear/kernel traits. Based on the GCA/SCA ratio however, a preponderance of nonadditive gene action mainly over-dominance was detected for all ear/grain traits. Significant reciprocal differences were also detected implying the direction of the crosses are important. The per se parental performance was a poor predictor of hybrid performance for ear/kernel related traits. Association studies of total grain weight with SCA and GCA effects for both L × T and diallel analysis indicated that low GCA combiners also are required to be incorporated in heterotic groups. While all the crosses generated from diallel matings recorded significant mid and better parent heterosis, hybrid combinations P10×P9, P8×P4, P8×P7, P1×P8, P6×P4 and P3×P8 in particular were at par/superior for multiple traits when compared with the standard commercial checks used in the study.ThesisItem Embargo Development of critical nitrogen dilution curve and simulation for rice-rice system under climate change(College of Post Graduate Studies in Agricultural Sciences, CAU-Imphal, Umiam, 2022-03) Bharti, Chandrabhan; Ram, VishramThe experiment entitled “Development of Critical Nitrogen Dilution Curve and Simulation for Rice-Rice System under Climate Change" was conducted at the trial field of the College of Post Graduate Studies, (CAU), Umiam, Ri-Bhoi district of Meghalaya during kharif and boro season, 2018-19 and 2019-20 respectively. A field experiment with 6 nitrogen levels such as 0, 30, 60, 90, 120, 150 kg ha-1 and 3 split application, 1st Split (50% as basal + 50% at 45 DAT as top dressing), 2nd Split (50% as basal + 25% at 45 DAT and 25% at 60 DAT as top dressing) and 3rd Split (25% as basal + 25% at 45 DAT, 25% at 60 DAT and 25% at 75 DAT as top dressing) during 2018-19 and 2019-20. Agronomic data were recorded throughout the crop growth period. Daily weather data related to the minimum and maximum temperature, rainfall and solar radiation were collected from the nearest meteorological station at ICAR Research Complex for NEH Region, Umiam, Meghalaya. The study undertaken to develop nitrogen dilution curve based on plant dry matter (PDM), to determine light and nitrogen distribution pattern with grain filling characteristics to study simulated performance of rice with rising temperature and CO2. The result showed that all the growth parameter viz., plant height, tillers hill, dry matter production, Leaf Area Index (LAI), growth indices like Crop Growth Rate (CGR), Relative Growth Rate (RGR) and Net Assimilation Rate (NAR) improved with succession of crop growth period i.e.15-90 days after transplanting (DAT) as well as at harvest. Among the levels of nitrogen and split application recorded significantly higher plant height, dry matter production, LAI, CGR, RGR, NAR, yield and yield attributes, were found at 150 kg N ha-1 followed by 120, 90, 60 and 30 kg N ha-1 . The result showed that N concentration (Nc) were decreased with the dry matter accumulation in rice. Nitrogen application rate had a significant effect on plant biomass accumulation and Nc. Critical N dilution curve (kharif pooled Nc= 6.754 PDM-0.562 and boro pooled Nc= 19.752 PDM-0.82) at the rate 150 kg N ha-1 (N5) followed by other treatment. The critical N dilution curve can be used as a tool for diagnosing the status of N in rice. The N nutrition index (NNI) calculated from this critical N dilution curve was significantly related to grain yield. Based on plant dry matter for an (NNI > 0.97 and NNI > 0.99) the grain yield was near 1 in both kharif and boro pooled 2018-19 and 2019-20, respectively. Canopy N and light profile parameter, i.e. the light extinction coefficient (KL) and for Nitrogen extinction coefficient (KN) and their relation enhance to yield. Crop management practice better-quality canopy eco-physiological features (lower KL, higher KN) to the scattering of light and N inside the canopy to make best use of canopy photosynthesis and give higher yield. Rice grain filling rate increased linearly with increasing levels of nitrogen and accumulated heat units such as growing degree days in °C day. The maximum grain filling was observed at the rate of 150 kg N ha-1 (N5) (0.38 to 0.28 mg grain-1 degree-1 day-1). The higher rice grain yield was recorded at rate of 150 kg N ha-1 (N5) followed by other treatment (4.11 and 4.24 t ha-1) both the kharif and boro pooled 2018-19 and 2019-20, respectively. When the temperature was increased by +1, +2, +3 ºC with enrichment in CO2 level from the current condition, it was reported gradual increase in the grain yield with the subsequent increase of temperature. Increasing temperature +1, +2, +3 ºC and CO2 408, 458, 508 and 558 ppm the yield increase by 7.89%, 13.48 to 61.43 % at rate of 150 kg N ha-1 during both the years and pooled 2018-19 and 2019-20, respectively.ThesisItem Embargo Studies on the suitability of potato in rice fallows under valley land of Meghalaya(College of Post Graduate Studies in Agricultural Sciences, CAU-Imphal, Umiam, 2022-05) Gurjar, Ganesh Narayan; Ram, VishramCrop production in sustainable manner through modern-agro techniques become the need of 21st century to feed the rising population across the planet earth. The producing crops without compromising future natural resources is very important to takes crop under rice-fallows. This study was led out by keeping in view that ricefallows in the Meghalaya and across the country remains more due to one or other problems specially lack of soil moisture, so to overcome from the lack of soil moisture could be solved by the application of organic mulch which are eco-friendly and improve in the soil properties including soil chemical and biological properties. However, the sowing of potato crop under rice fallows on time is very important to get higher tuber yield. Because the potato crop is very sensitive to rising temperature under changing climatic scenario, also sowing of potato crop on time does not require any monetary inputs which is another benefit to farmers of Meghalaya and other regions of NEI as well as for other parts of the country. The present study was led out on rice-potato system under rice fallows to increase in the cropping intensity of the region by taking potato crop under various sowing dates and mulching practices throughout the 2018-19 and 2019-20, and their results were recorded significantly beneficial in terms of both quantity and quality. Firstly, the thermal response of potato crop was recorded significant under S1 (5th November) sowing date among various practices, and sowing of potato crop after S1 has significantly negative effect on plant physiological parameter (plant height, number of primary and secondary branches, leaf area index), on growth parameters (CGR, RGR, NAR, dry matter production, days to 50 % emergence, stolon formation, tuber initiation and tuber bulking rate), on yield and yield parameters (number of tubers, weight of tubers, individual tuber weight, grading of tubers, biological yield, tuber yield and harvest index) and on meteorological parameters (light interception, radiation use efficiency, thermal use efficiency, lead area duration and growing degree days) at different growth stage during experimentation. However, the higher plant height (cm) was recorded under M1 (rice straw) and M2 (weed biomass) mulch and lower in M0 (No mulch); number of primary and secondary branches were recorded under M1 and M0 mulches at 90 and 75 DAS, individually. Higher and lower leaf area index was recorded under S2 (20th November sowing date), M2 and M0; CGR -Haulm, CGR-Tuber, RGR, NAR recorded higher under S1 and lower under S4 (20th December sowing date) and dry matter in the S1 and S5, days to 50% emergence, stolon formation and tuber initiation under M0 and M1 mulches while bulking rate was significantly higher and lower under S1 and S5 (4th January sowing date), M0 at 105 DAS. However, the higher tuber yield and harvest index during both years was recorded under S1 and M0 combinations. Higher amount of good quality “A”, “B” and “C” grade tubers were recorded under S1M1 (5th November sowing date and rice straw mulch), S1M2 (5th November sowing date and weed biomass mulch) and S5M0 (4th January sowing date and no mulch) at harvest during experimentation. Moreover, the higher and lower LI, RUE, TUE, LAD and GDD were recorded under S1 and S5 except LI under M1 and M0 during both the years, respectively. Increased N mineralization pattern of organic mulches was chronicled in M1 under S5 and M2 under S1, P mineralization of M1 under S1; M2 under S1 and K mineralization of M1 under S3 during first and second year, respectively. Soil moisture depletion pattern was chronicled variable at various growth stages as well as under various soil depths, the advanced depletion was recorded at upper soil layers (0-15 cm) in assessment to lower soil layers (15-30 and 30-45 cm soil depths) under M0 and M1, respectively. The chemical and biological pools were changed with growth stages of potato and soil depths (0-10, 10-20 and 20-30 cm soil depth), also higher pool was observed during second year in contrast to first years under different sowing dates and mulching practices during both years of research. Besides, the biological pools of bacterial counts were recorded higher at early sowings under M1 mulch and as delayed sowing leads to lower bacterial count at various soil depths, while in case of fungal count, its higher number was recorded under delayed sowings from S1 onwards in M1 mulch in comparison to M0 at various growth stages as well as at different soil depths. Moreover, the significantly higher gross income, net income and benefit to cost ratio was recorded under S1 sowing date in comparison to others and higher cost of cultivation of the rice-potato system was recorded under M1 in comparison to others. Lastly, the potato crop sown on early dates with rice straw and weed biomass mulch were found most suitable in comparison to late sowing and no mulch practices in rice fallows under valley land of Meghalaya.
