1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)
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Item Physiological and molecular studies in mitigating drought stress of Tomato (Solanum lycopersicum) by biochar with organic amendments(Department of Plant Biotechnology, College of Agriculture , Vellayani, 2022-11-09) Anjusha, P; Viji, M MThe study entitled “Physiological and molecular studies in mitigating drought stress of tomato (Solanum lycopersicum) by biochar with organic amendments” was conducted at College of Agriculture, Vellayani, Thiruvananthapuram, during 2021-2022. The primary objective of this study was to determine the physiological and molecular attributes of tomato grown under water stress as influenced by biochar with organic amendments. The experiment on tomato variety ‘Vellayani Vijay’ was conducted in a completely randomized design in pot culture with five replications. In order to assess the effect of biochar (BC) (0.5% w/w) and organic amendments such as vermicompost (VC) and farm yard manure (FYM) in mitigating the consequences of water stress, individual treatments viz. (Biochar (0.5% w/w), VC (50g/10kgsoil) and FYM (50g/10kg soil)) as well as combined treatments viz. ((Biochar+VC) and (Biochar+FYM)) were carried out along with T1 control (normal irrigated condition) and T7 control (water stress). The study consisted of 12 treatments, in which T1 to T6 were irrigated normally whereas treatments designated as T7 to T12 were subjected to 25% water stress. The present study was carried out using biochar derived from rice husk that was subjected to maximum pyrolysis temperature of 550°C in a cylindrical iron tank. Water stress of 25% was imposed by gravimetric method for a period of 80 days (after three weeks of sowing). The seedlings were maintained in protected condition for the first three weeks. Various morpho-physiological and yield parameters were evaluated at different critical stages of the crop, such as seedling stage, vegetative stage, flowering stage, fruiting stage and harvesting stage. Molecular studies were carried out at 50% flowering stage. Water stress had a negative impact on morphological, physiological and yield attributes of S. lycopersicum except total soluble solids, when compared to plants under normal irrigated condition. Biochar treatment was found to effectively mitigate the deleterious impacts of water stress. Plants treated with biochar outperformed the plants grown in both VC and FYM with regard to all the physiological and morphological parameters studied. However the best yield performance (yield and yield parameters) was obtained in the treatment with 124 biochar in combination with vermicompost. According to the results obtained it was clear that the combined application of biochar and vermicompost increased the relative water content, membrane stability index, chlorophyll stability index, photosynthetic rate, total protein content, stomatal conductance, transpiration rate, plant height and primary branches per plant under both water stress and normally irrigated conditions when compared to the non-treated controls. This indicates the ability of biochar to retain water and thereby increasing soil moisture content. Furthermore, under water stress, there was a significant improvement in the morphological traits such as, root weight (57.07%), shoot weight (33.33%), root: shoot ratio (17.91%), fruit number (43.54%), fruit size (69.93%), fruit weight (13.10%), total soluble solids (10.32%) and yield (62.42%). SlWRKY8 gene has an important role under drought stress conditions and is reported to have role in the regulation of ROS pathways and mitigating the detrimental effects in plants grown under water stress condition. In the present study, quantitative real time PCR amplification of SlWRKY8 gene in tomato leaves (taken at 50% flowering stage) showed an increase in the expression level of this gene in the treatments with combined application of biochar and vermicompost, both under water stress condition (T11) (3.24 fold) and normal irrigated condition (T5) (1.51 fold) compared to their respective controls (T7 and T1). This indicates that BC and VC combinations can be applied to tomato plants grown under water stress for the upregulation of SlWRKY8 genes which regulate the ABA signaling and helps in ABA-mediated stomatal closure in water stress condition. Taken together, the study demonstrate that, the combined application of vermicompost and biochar not only boost crop production, but also mitigate the destructive impacts of water stress by influencing physiological, morphological and molecular parameters of tomato.Item Physiological and molecular studies on genera of loranthaceae and their management(Department of Plant Physiology, College of Agriculture, Vellanikkara, 2021) Garggi, C; Girija, THemiparasitic plants belonging to the family Loranthaceae are major tree parasites. Dendrophthoe falcata, Helicanthus elastica, Macrosolen capitellatus are major hemiparasites infecting perennial crops of the tropics. Helixanthera wallichiana and Taxillus tomentosus are two important hemiparasites infecting the fruit and timber trees of the high ranges. Apart from being a troublesome parasite they also serve as a linchpin reservoir supporting an extensive ecosystem. The prevailing investigation namely “Physiological and molecular studies on genera of Loranthaceae and their management” was carried out at Department of Plant Physiology, College of Agriculture, Vellanikkara, Thrissur, during the period from 2015 to 2020. Morphological characters of representative species viz., Dendrophthoe falcata, Helicanthus elastica, Macrosolen capitellatus, Helixanthera wallichiana and Taxillus tomentosus from five selected. Samples of these were collected from various locations from the plains and highranges of Thrissur. In all the selected species, leaves were oppositely arranged, D. falcata and H. elastica had oblong shaped leaves, leaves of M. capitellatus was lanceolate in shape, and H. wallichiana and T. tomentosus had narrow ovate shaped leaves. Fruit was berry in all the genera. Hemiparasites possess a physiological structure called haustoria through which they abstract water and minerals from the host. Haustorial branching pattern in all the genera was found to be basal epicortical root (ber). Haustorial portions of the collected samples were treated and prepared to permanent slides. Anatomical sections of the haustoria of the five selected genera of Loranthaceae revealed that there exists a transition zone between the host- parasite interphase region. This was observed as undifferentiated parenchymatous cells which aid in translocation of molecules. Presence of xylem elements were observed at the haustorial region. Haustorial anatomy of M. capitellatus was unique as there was complete merging of cells of host and parasite at the interphase region. The lineage of five selected genera belonging to Loranthaceae family were studied by molecular assay. The results from the ISSR assay revealed that, T. tomentosus and M. capitellatus had maximum similarity compared to all the other genera, since it formed a separate cluster. Morphological characterization indicated similarity between the two genera in the haustorial attachment pattern. Both the species have a single point of attachment to the host. H. wallichiana was observed to be more similar to the first cluster. D. falcata formed another branch close to H. wallichiana, where all these four genera formed the main group. H. elastica formed a separate lone group, which indicated genetical variance from other genera studied. Morphological observations supporting such a uniqueness in this parasite was noted in haustorial branching type, where basal epicortical root with lateral tendril like structures from nodes and internodes were observed. The parasite also showed other phylogenetically advanced characters according to Angiosperm Phylogeny Group (APG system) of classification like fused corolla and calyx. To study the host parasite interaction, root feeding studies with labelled 32P were undertaken. Cocoa plants infected with both parasites D. falcata and H. elastica was selected for the study. 32P in carrier solution of 1000ppm orthophosphoric acid @ 2 mCi per plant was fed to the surface running roots of cocoa. Leaf samples of the host and parasite were collected at 7 and 14 days after treatment and assayed for radio activity. To understand the translocation from parasite to host, leaves of the parasitic species both D. falcate and H. elastica were also smeared with labelled 32P and leaf samples were analysed from different parts of both the host and the parasite. These experiments were done on different trees. Leaf samples of the host and parasite were collected at 2, 7 and 14 DAT and assayed for radio activity. Results from the radio assay indicated that there is bidirectional movement of nutrients from host to parasite and parasite to host. There exists a prioritized partitioning pattern for nutrient transport (phosphorous) based on demand by the sink, regardless of the parent plant. The host and parasite were found to act as a single system indicating their coexistence. Physiological parameters of the host and parasites were also observed using InfraRed Gas Analyser (IRGA) for a period of six months. It was observed that stomatal conductivity of D. falcata and H. elastica was significantly higher than the host cocoa. Even though there was no much variation in the photosynthetically active radiation (PAR) received by the host and parasite during the period of observation, D. falcata and H. elastica had significantly higher rate of photosynthesis than cocoa. Transpiration rate of both parasites were significantly higher than their host. Carboxylation efficiency and light use efficiency of H. elastica were observed to be significantly higher than the host, cocoa. Field experiment was conducted to improve the management strategy and control the spread of the parasite. Use of surfactant was found to improve the efficacy of ethephon in controlling the regrowth of parasite on host plant. Non- ionic surfactants viz., Nonyl phenol ethoxylate (NPE) and Organosilicone (OS) were selected for the study. A combination of OS (0.5 ml/L) surfactant with ethephon (25ml/L) was successful in suppressing the regrowth of both D. falcata and H. elastica.