PG Thesis

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Subject: search.filters.subject.Molecular characterization

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    Morphological and molecular characterization of nerium (Nerium oleander L.)
    (Department of Floriculture and Landscaping, College of Agriculture, Vellayani, 2025) Jisna Johnson; Reshmi, C R
    The study entitled "Morphological and molecular characterization of nerium (Nerium oleander L.) genotypes" was conducted at the Department of Floriculture and Landscaping, College of Agriculture, Vellayani, Thiruvananthapuram, during the period 2022-2024. The primary objective was to evaluate the performance of fifteen nerium genotypes and to characterize them using morphological descriptors and molecular markers for assessing their genetic variability and diversity. Analysis of variance revealed significant differences among the genotypes for all morphological traits, including plant height, leaf blade length, and leaf blade width. Among the fifteen genotypes, twelve (T1, T2, T3, T4, T5, T6, T8, T9, T10, T11, T13 and T15) flowered during the experimental period. Floral characteristics, such as the number of flowers per plant at full flowering stage (i.e. two months after first flowering), flower diameter, corolla throat length, corolla throat diameter, corolline appendage length, and sepal length, also showed significant variations among the genotypes. Leaf blade width showed the highest phenotypic and genotypic coefficients of variation (PCV and GCV) among the plant traits, while the number of flowers per plant at the full flowering stage (i.e., two months after flower initiation) showed maximum variation among the floral traits. Heritability was high across all traits (69.6%–100%), with leaf blade length and single flower weight recording the maximum values. Notable genetic advance was observed, especially in the number of flowers per plant and corolla throat diameter. Traits with high heritability and genetic advance indicate strong genetic control, making them ideal for selection in breeding programmes. Correlation analysis revealed that flower diameter exhibited a significant positive genotypic correlation with plant height, length and width of leaf blade, corolla throat diameter, single flower weight, and shelf life. However, a negative correlation was observed between flower diameter and both the number of flowers per plant and overall flower yield. Additionally, plant height showed a significant 126 positive phenotypic correlation with flower diameter, corolla throat diameter, and single flower weight. Although flower diameter was negatively correlated with the number of flowers per plant, it displayed a strong positive correlation with plant height, corolla throat diameter, and single flower weight, making it a crucial trait for selecting loose flowers. Genetic diversity analysis using the ‘Average method’ and ‘Euclidean distance measures’ clustered the genotypes into four groups based on floral characteristics. The maximum inter-cluster distance was observed between cluster 3 and cluster 4, suggesting that hybridization between these clusters would be most effective. Scoring based on DUS guidelines revealed the highest score for genotype T13 and it was followed by T1 and T4. Molecular characterization of the fifteen genotypes was carried out using ten ISSR primers, all of which generated polymorphic bands. Among the 98 amplicons obtained, 81 exhibited polymorphism, whereas 17 were found to be monomorphic. Among the primers, UBC 826 yielded the highest number of alleles (14), while UBC 814 produced the fewest (3). The primer UBC 855 exhibited the highest polymorphic information content (PIC) value of 0.38, whereas UBC 814 showed the lowest PIC value of 0.15. Based on the cluster analysis of the molecular data, the genotypes were grouped into three distinct clusters: Cluster 1 consisting of seven genotypes (T1, T2, T4, T7, T8, T9, T12), Cluster 2 also containing seven (T3, T6, T10, T11, T13, T14, T15) and Cluster 3, comprising a single genotype (T5). Among the genotypes, T3 exhibited the highest yield of fragrant flowers, followed by T1, making them ideal for loose flower production and potential parental genotypes for breeding programmes. T5 was identified as a dwarf genotype, suitable for potted plant applications. Seasonal variations in flower production were observed across all the genotypes which flowered during the experimental period. These findings provide valuable insights into the morphological and genetic diversity of nerium genotypes, aiding in the selection of superior genotypes for floriculture and breeding purposes.
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    Molecular characterization of brinjal (Solanum melongena L.) genotypes and their performance assessment in summer
    (Department of Genetics and Plant Breeding, College of Agriculture, Padanakkad, 2023-05-31) Chakravaram, Alekhya; Namboodiri Raji Vasudevan
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    Physico-chemical and molecular characterization of grain quality of traditional rice varities
    (Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, 2016) Jeena George; Jayalekshmy, V G
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    Genetic diversity analysis in taro (Colocasia esculenta (L.) Schott) of north east India
    (Department of Plant Biotechnology, College of Agriculture, Vellayani, 2014) Vinutha, K B; Asha Devi, A
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    Bio-efficacy and molecular charaterization of the native isolates of Bacillus thuringiensis Berliner
    (Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2008) Jyothi Sara Jacob; Maicykutty P Mathew
    Bacillus thuringiensis Berliner shortly known as B.t., is a gram-positive, spore forming bacterium that produces proteinaceous crystal containing insecticidal toxins. The host range of B.t. has expanded considerably due to extensive screening programmes. By virtue of its lack of toxicity towards other species of animals and human beings, B.t. has emerged as a safe candidate in the IPM programmes of various agroecosystems. Frequent exposure to one type of B. thuringiensis toxins can develop resistance in insects. Isolation of novel strains is important to overcome the onset of insect resistance. The present study on “Bio-efficacy and molecular characterization of native isolates of Bacillus thuringiensis Berliner” was conducted at the Department of Agricultural Entomology and CPBMB, College of Horticulture, Vellanikkara during the period from 2006 to 2008 with an objective to study the pathogenicity of 20 B. thuringiensis isolates collected from the Western Ghats of Kerala, one of the well known hot spots of biodiversity. The tobacco caterpillar, Spodoptera litura Fb. which was used as the test insect was reared in semi-synthetic diet (Ballal, 2004) and also in natural diet on castor leaves. The preliminary screening was performed for lepidopteran specificity with the ideal dose of 1 x 109 spores per ml showed that three isolates were toxic to S. litura. The per cent mortality caused by the lepidopteran effective isolates, namely, KAU-11, KAU-51, KAU-166 and the reference strain, HD-1 were 76.7 per cent, 80.0 per cent, 86.7 percent, 96.7 per cent respectively. A standardized bioassay was carried out with five different concentrations of all the selected isolates namely, KAU-11, collected from Thusharagiri (Calicut Dt.), KAU-51 from Kolahalamedu (Idukki Dt.), KAU-166 from Nelliyampathi (Palakkad Dt.) and the reference standard HD-1 (B. thuringiensis subsp. kurstaki). The mortality ranged from 63.3 to 100.0 per cent in various isolates and there was no significant difference between isolates. This indicated the equal effectiveness of the native isolates with the standard strain, HD-1. The LC50 value for the isolates was calculated by Finney’s Method of Probit Analysis. The lowest LC50 was obtained in KAU-51, with 6.3095 x 104 spores per ml and highest in KAU-11, with 1.2589 x 106 spores per ml. The lethal time to cause 50 per cent mortality (LT50) ranged from 44.4 h. to 96.0 h. in different isolates. The lowest LT50 was recorded in HD-1, which shows the ability of the standard to cause mortality slightly earlier compared to other isolates. The molecular characterization of the selected isolates was performed with RAPD-PCR technique. RAPD-PCR is a simple and rapid method for determining genetic diversity in various organisms and is a means of creating a biochemical finger print of an organism. Out of the 20 primers screened, 10 primers which produced more than five bands were selected for RAPD analysis. The RAPD data was used to generate a similarity matrix using the NTSyS programme. Clustering was done and dendrogram was drawn using Unweighted Pair Group Method of Arithematic Averages (UPGMA). The results showed that high variability exists between the selected isolates. Further studies are required to identify the subspecies of the efficient B.t. isolates to evaluate the field effectiveness against S. litura and other major lepidopteran pests for its utilization in pest management programmes. More primers need to be screened to study the genetic diversity of the isolates.