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

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Subject: search.filters.subject.drought tolerance

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    Characterization and evaluation of selected genera under cucurbitaceae for drought tolerance
    (Department of Agricultural Vegetable Science, College of Agriculture,Vellanikkara, 2024-03-18) Lasima Jahan, M S.; Sangeetha Kutty, M
    Cucurbits comprise an extensive category of vegetables cultivated worldwide, playing a crucial role in the daily dietary intake of a large global population. The Cucurbitaceae family encompasses numerous genera and stands as the most extensive tropical vegetable group. This important family of vegetables comprises 950 species across more than 90 genera, predominantly found in tropical and subtropical regions (Parvathi et al., 2022). Cucurbitaceae family exhibits a remarkable genetic diversity, enabling them to thrive in a wide range of climates, including temperate regions, arid deserts, and tropical or subtropical zones (Rai et al., 2008). Despite their wide adaptability and widespread utility across the globe, cucurbits face increasing risks due to climate change, resulting in both biotic (living organism-related) and abiotic (non-living, environmental) stresses. Drought is one of the major limiting factors that significantly reduces crop output and results in both economic and nutritional insecurity (Wang et al., 2022). The present study entitled ‘Characterization and evaluation of selected genera under cucurbitaceae for drought tolerance’ was conducted at the Department of Vegetable Science, College of Agriculture, Kerala Agricultural University, Vellanikkara. The study was conducted from September to March and May to July of the academic year 2022-2023. Two experiments made up the current study. In the first experiment, 27 genotypes of cucurbits were characterized. It included eight genotypes of Luffa acutangula (LA-1 to LA-7), one Luffa cylindrica (LC-1), six Cucumis melo var. momordica (CMM-1 to CMM-6), two Lagenaria siceraria (LS-1 and LS-2), one Cucumis melo var. conomon (CMC-1), three Cucumis melo var. callosus (CC-1 to CC-3), one Cucumis melo var. utilissimus (CMU-1), one Momordica charantia var.muricata (MCM-1), two Cucurbita moschata (CM-1 and CM-2), one Cucumis sativus (CS-1) and one Citrullus lanatus (CL-1). During the study, observations were made on vegetative and reproductive characteristics, fruit and yield attributes, bitterness, as well as pest and disease incidence. Variations were noted among the species for all these parameters. In the second experiment, twenty genotypes from the first experiment were evaluated for drought tolerance in a pot culture experiment. The genotypes used in the study were LA-1, LA-2, LA-4, LA-8, CMM-2, CMM-4, CMM-5, CMM-6, CC-1, CC-2, CC-3, CS-1, CMU-1, CMC-1, MCM-1, LS-1, LS-1, CM-1 and CM- 2. Biochemical, physiological and morphological response of plants to drought stress were recorded in this study. The proline content and DPPH free radical scavenging activity exhibited different ranges among the genotypes of different species. In all genotypes, the proline content and DPPH free radical scavenging activity was observed to increase under drought conditions compared to control conditions. Cucumis melo var momordica (CMM-2, CMM-4, CMM-5 and CMM-6), Cucumis callosus (CC- 1, CC-2, and CC-3) and Momordica charantia var. muricata (MCM-1) had high proline content and DPPH free radical scavenging activity under water deficit when compared to well watered condition. All genotypes exhibited a reduction in total chlorophyll content under drought stress. Less reduction in chlorophyll content was seen in Cucumis melo var momordica (CMM-2, CMM-4, CMM-5 and CMM-6), Cucumis callosus (CC-1, CC-2, and CC-3) and Momordica charantia var. muricata (MCM-1). Water deficit leads to stomatal closure, a decreased transpiration rate, and an increase in leaf temperature. The change in photosynthesis rate, transpiration rate, stomatal conductance and leaf temperature was lower in Cucumis melo var momordica (CMM-2, CMM-4, CMM-5 and CMM-6), Cucumis callosus (CC-1, CC-2, and CC-3) and Momordica charantia var. muricata (MCM-1). Cucumis melo var momordica (CMM-2, CMM-4, CMM-5 and CMM-6), Cucumis callosus (CC-1, CC-2, and CC-3) and Momordica charantia var. muricata (MCM-1) exhibited higher root length and root weight under water deficit compared to well watered condition. Lower reduction under stress, in shoot length, as well as fresh and dry weights, were also observed in these genotypes, indicating their capacity for drought tolerance. These twenty genotypes of cucurbits were grouped into four clusters based on selected physiological and biochemical characters, using R software. The cluster III had the highest number of genotypes (8), followed by cluster IV (5). Cluster III consisted of the drought tolerant genotypes viz. CMM-2, CMM-4, CMM-5, CMM- 6, CC-1, CC-2, CC-3 and MCM-1. Thus, the present study reveals that Cucumis melo var momordica (CMM-2, CMM-4, CMM-5 and CMM-6), Cucumis callosus (CC-1, CC-2, and CC-3) and Momordica charantia var. muricata (MCM-1) are tolerant to drought. Hence there is a vast scope for further utilization of these genotypes in breeding as well as grafting programs.
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    Screening and QTL mapping for drought tolerance among the plus trees of Tectona grandis L.f.
    (Department of Forest Biology and Tree Improvement, College of Forestry ,Vellanikkara, 2024-03-23) Aswath, M N.; Santhoshkumar, A V
    The present study investigated standardization of the Miniclonal propagation technique, assessing genetic diversity among accessions using ISSR markers, screening plus trees for drought stress and recovery, and discovering Single Nucleotide Polymorphisms (SNPs) through Genotyping by Sequencing in plus trees of Tectona grandis L. f. The study attempted to map the QTLs associated with drought tolerance, providing valuable insights into the genetic basis of this trait in teak. The effects of auxins on epicormic shoot production and rooting were evaluated to select the best hormone combination. The shoot production varied among the auxins and their concentrations. Indole-3-butyric acid (IBA) at 4000 mg L-1 showed optimal shoot production, enhancing rooting potential, with the highest rooting percentages observed at 49.19% for 4000 mg L-1 IBA and 41.71% for 3000 mg L-1 IBA. The cuttings treated with 1-Naphthaleneacetic acid (NAA) showed only 5.61 to 14.01% rooting, whereas a combination of IBA and NAA encouraged the callusing. The size of the cuttings affected the rooting potential, and the rooting percentage showed a significantly positive correlation with shoot diameter (r=0.89). Further, epicormic shoot and root production was observed to vary significantly among the accessions. Aravallikkavu (10.67) and Top slip-6 (8.33) exhibited the highest epicormic shoot numbers, while Nedumkayam-1 displayed minimal shoot production. Nellikutha-6 showed the highest rooting percentage (57.11%), contrasting with Nellikutha-2 (22.50%). Subsequently, ten accessions were successfully propagated for further investigations. Genomic DNA from ten accessions was extracted using the modified CTAB protocol, yielding DNA concentrations ranging from 166.7 to 269.4 ng μL-1, with OD260/280 values between 1.86 and 2.08. Amplified bands resulted in 212 observed alleles, of which 199 were polymorphic, demonstrating genetic diversity, while 13 were monomorphic. The Jaccard similarity coefficient between Topslip-6 and Topslip-10 was 0.361, suggesting their genetic similarity. Accessions 6, 4, 10, 8, and 7 displayed coefficients of 0.504, 0.476, 0.465, and 0.440, respectively, indicating close relationships. Morpho-physiological and biochemical responses of teak ramets to drought stress were evaluated, indicating varying tolerance levels among accessions. Based on morphological indicator (percent leaf retained), accessions Topslip-6, Topslip-10, and Shankaramthode-1 were classified as "Highly Tolerant," whereas Nellikutha-2 was "Highly Susceptible". Photosynthesis varied, with Topslip-6 maintaining the highest 2 m-2 s-1) and Nellikutha-2 exhibiting the lowest (1.200) under drought. Accessions displayed diverse responses under drought for Fv/Fm (0.819- Topslip-10 to 0.309-TC11) and chlorophyll content (1.573- Nedumkayam-1 to 4.342 - TC4). Maximum proline was produced by Topslip-6 -1), whereas -1 -1) produced minimal proline. Similarly, Accession 8 produced lower glycine content -1), and Topslip-10 exhibited -1. Cluster analysis revealed distinct groupings, with PCA aiding accession selection based on performance indices, categorizing teak accessions into Highly Susceptible (Nellikutha-2), Susceptible (Nedumkayam-2 and Nellikutha- 1), Moderately Tolerant (Topslip-6, TC4, Nedumkayam-1, and Shankaramthode-1), and Highly Tolerant (Topslip-10, TC11, and Topslip-6) categories. Genotyping based on Illumina-assembled genomic sequences for diverse accessions was carried out. Variant calling on ten genomes yielded 7,518,960 variants and filtered down to 3,665 SNPs. GWAS identified 19 significant SNPs linked to drought tolerance, supported by QQ and Manhattan plots. BLASTX and UniProt annotations unveiled genes associated with stress resistance, organ formation, and metabolic processes. QTLs on Chromosome_1 (BLH9, POX), Chromosome_4 (DXS, TKL), and Chromosome_11 (MFS, MIK2) were implicated in diverse physiological functions. BLH9 is implicated in plant organ and shoot formation, xylem development, morphogenesis, and meristem activity. DXS is involved in chlorophyll biosynthesis and terpenoid biosynthesis. MFS regulates stomatal closure, while MIK2 is associated with various cellular responses, including cellular and root activity. The study enhances understanding of the genetic basis of drought tolerance in teak, contributing valuable information for breeding programs and sustainable forest management. The multidisciplinary approach integrating physiological, biochemical, and genomic analyses offers a comprehensive framework for understanding and improving teak cultivation, ensuring sustainable production in the face of environmental challenges