PhD Thesis
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Item Physiological and molecular basis of selective fertilization for high temperature stress tolerance in tomato (Solanum lycopersicum L.)(Department of Plant Physiology, College of Agriculture, Vellayani, 2025-01-01) Ammu Alphonsa John; Roy StephenThe study entitled “Physiological and molecular basis of selective fertilization for high temperature stress tolerance in tomato (Solanum lycopersicum L.)”, was undertaken with the objective to screen the critical temperature for pollen germination of tomato genotypes and to evaluate the thermotolerance of selectively fertilized tomato hybrids through physiological and molecular techniques. The experiments were conducted using the Open field & Rainout shelter (ROS) facility at the Department of Plant Physiology, College of Agriculture, Vellayani during 2019-2024. The first experiment was devised to advance the selectively fertilized hybrid of Anagha and Manuprabha by the method of selective selfing by pollen selection up to F4 to stabilize the thermotolerance. Pollen germination %, photosynthetic rate, RWC, percentage leakage, chlorophyll content, CSI and stomatal conductance were observed in all generations. In F2 generation, T3 and T10 line showed comparatively better performance than the other lines on the basis of phenotypic evaluation and the molecular markers SSR136 and SSR630 were also present in these lines. The seeds from T3 and T10 line selected for next generation and F3 was developed. In F3 generation, T6 and T8 line were selected for next generation i.e., F4 and the molecular markers SSR134 and SSR630 were present in these lines. In F4 generation, T4 and T6 were the best lines. The second experiment was designed as a confirmation study of the selective fertilization technique in which ten popular varieties of tomato namely Anagha, Vellayani Vijay, Manuprabha, Nandi, Arka Saurabh, Arka Rakshak, Pusa Rohini, IIHR 26372, Arka Vikas and Akshaya were used for the identification of critical temperature for pollen germination. Mature pollen grains from the fully opened flowers were collected and incubated at different temperatures (320C to 400C) for two hours in the pollen germination media. The temperature of 36oC identified as the critical temperature for pollen germination and Anagha showed high pollen germination percentage (25.88 %) and Arka Saurabh showed least pollen germination percentage (16.34 %) at this critical temperature. In the third experiment, based on the critical sterility temperature six varieties were selected for pollen selection and selective fertilization. The variety Anagha, Vellayani Vijay and IIHR26372 with highest critical temperature for pollen germination percentage were selected as tolerant genotypes and the variety Manuprabha, Arka Saurabh and Pusa Rohini with low critical temperature were selected as the susceptible genotype. Selective fertilization (SF) was done between the six genotypes. Reciprocal cross between the tolerant and susceptible genotypes was also done by selective fertilization as well as normal cross for comparison. Growth performance of the selectively fertilized tomato plants was evaluated in ROS. The experiment was laid out in CRD with three replications. Floral characters (number of clusters and number of flowers per cluster) were noted significantly high in crosses with susceptible genotype as male parent. Among the crosses, T23 recorded the highest no. of clusters (18) and number of flowers per cluster (10). The flower characters like percentage of flowers with exerted stigma and length of stigma exertion were found high under high temperature but the selectively fertilized crosses recorded less value than the normal crosses. T16 (20.63%) showed lesser stigma exertion. The length of exerted stigma was recorded least in T7 (0.13 mm) which was on par with T2, T11, T17, T16, T23, T28, T26, T24, T19, T5, T4, T25, T34, T10, T1, T22 and T8. The no. of days to first flowering after sowing were recorded, T30 took the shortest period (37 days) for flowering, and T36 took the longest (50 days). The Normal and SF crosses with tolerant as male parent flowered comparatively earlier than its reciprocal crossed ones. Physiological parameters like photosynthetic rate and relative water content were observed high in selectively fertilized crosses than the normal crosses under higher temperature, the crosses of SF plants with tolerant genotype as male parent show significantly higher photosynthetic rate while it was SF plants with susceptible genotype as male parent in case of RWC. The photosynthetic rate was recorded higher in T13 (10.73 μmol CO2 m-2 s-1) and the relative water content was recorded highest in T29 (64.09%). Among the temperature tolerance characters like membrane integrity (% leakage), SOD activity and pollen viability, % leakage and SOD activity recorded higher in selectively fertilized plants than the normal plants while the pollen viability recorded high in normal crosses. The T27 (1.78 %) recorded the least percentage leakage, which was on par with T35 and T30. The highest value of SOD activity was recorded in T28 (0.35 activity g-1 min-1) and pollen viability was observed highest in T1 (100 %). Vitamin C content of leaves were recorded highest in normal crossed hybrid with tolerant as male parent, T9 (413.02 μg g-1) showed highest value. The number of fruits/cluster and yield were high in selectively fertilized crosses than the normal crosses, specifically the SF crosses with tolerant genotype as male parent. T10 (4.67) recorded highest number of fruits per cluster which was on par with T16. The yield was very less in ROS condition and the highest value was also observed in the treatment T10 (226 g plant-1). In the first experiment, the selfing of plant through SF improves its performance in each generation. The mean performance of F4 plants were better than F2 and F3. In the second experiment among the ten varieties of tomato, Anagha was found as the best with high germination percentage with critical temperature 360 C and Arka saurabh as the susceptible one with lowest pollen germination percentage. In the third experiment selective fertilization technique was found to have an advantageous influence on the physiological and yield attributes as it increased the photosynthetic efficiency and high temperature stress tolerance mechanism. Among the various cross combinations, selectively fertilized cross of tolerant and susceptible parent having tolerant genotype as male parent was found to be the best at high temperature. Hence this study has importance in improving the high temperature tolerance mechanism in tomato under increasing daily mean temperature.Item Physiological and molecular assessment of abiotic stress tolerance in selectively fertilized coconut hybrids (Cocos nucifera L.)(Department of Plant Physiology, College of Agriculture,Vellayani, 2024-03-14) Afna Mol, O P; KAU; Roy Stephen; Gladis, RThe present study entitled “Physiological and molecular assessment of abiotic stress tolerance in selectively fertilized coconut hybrids (Cocos nucifera L.) was carried out in the Department of Plant Physiology, College of Agriculture, Vellayani during 2018-2023. The objective of the study was physiological and molecular evaluation of selectively fertilized coconut hybrids for water stress and temperature stress tolerance and to assess genetic variability for temperature stress tolerance through pollen selection at critical temperature. The study consisted of four experiments. In the first experiment, 10 year old field grown coconut palms of the following varieties Kerasree (WCT X MYD)- 198 selectively fertilized, Keraganga (WCT X GB)-selectively fertilized, Kerasree (WCT X MYD) Hybrid, Keraganga (WCT X GB) Hybrid and West Coast Tall at Regional Agricultural Research Station, Pilicode, Kasaragod were used as the experimental material for the study. The experiment was carried out in Randomized Block Design (RBD) with four replications during 2019 March to 2019 April. Water stress was imposed by withdrawing irrigation from the field for one month and physiological and biochemical observations were made at 15 days interval .Then the palms were irrigated on 30th day and recovery responses were analysed on 15th day after the irrigation rescheduling. On physiological analysis, selectively fertilized Kerasree showed higher relative water content and epicuticular wax of the leaves. Keraganga selectively fertilized showed maximum photosynthetic rate and cell membrane stability index. Leaf temperature was minimum in Kerasree selectively fertilized hybrids followed by Keraganga selectively fertilized hybrid. WCT recorded higher transpiration rate followed by Kerasree selectively fertilized hybrid. Stomatal conductance was higher in WCT and then in Kerasree selectively fertilized hybrids. In all the parameters tested both the selectively fertilized hybrids responded positively towards drought than their normal hybrids and this was an indication of higher water use efficiency in them. Recovery response after rewatering was also higher in selectively fertilized hybrids than their normal hybrids. The biochemical parameters like chlorophyll content, antioxidant enzymes viz SOD and peroxidase activities were found maximum in Kerasree selectively fertilized hybrids under water stress condition. Recovery response of these parameters were also found elevated in Kerasree selectively fertilized hybrids. Also Kerasree selectively fertilized hybrids showed lowest membrane damage (lipid peroxidation value) compared with normal hybrids and WCT. Amount of proline in leaves was found higher in WCT, which was on par with Kerasree selectively fertilized hybrid and Keraganga selectively fertilized hybrid. 199 In the second experiment, molecular characterization was carried out in the above five treatments. Protein profiling of leaves was done in all the five treatments of experiment one, using SDS-PAGE, in which, there was variation in the intensity of large subunit (55 kDa) as well as small subunit (around16 kDa) of RuBisCO, among the treatments. The intensity of those bands were found higher in WCT and Kerasree selectively fertilized hybrid .The band expressed in selectively fertilized hybrid in between 26 kDa to 36 kDa was absent in other treatments.. SSR markers CncirE2, CncirE10, CncirE12 and CncirH4 were screened in five treatments and polymorphism was observed in CncirE2, CncirE12, and CncirE10. RNA-seq tranascriptomic analysis of Kerasree selectively fertilized hybrid in reference with Kerasree was done to identify the key differentially expressed genes (DEGs) responding to water stress tolerance in Kerasree selectively fertilized hybrid. A total of 16671 genes were found expressed in Kerasree SF differing from Kerasree. 9635 genes were upregulated and remaining 7036 genes were down regulated in Kerasree SF.Abiotic stress related genes like late embryogenesis abundant protein Lea5 and HSPs were found differently expressed in Kerasree S.F hybrid in response to water stress. Gene ontology of the identified genes revealed that in terms of biological processes the following were the most represented GO terms (GO:0006749, 24 proteins, GO:0006468, 23 proteins,GO:0009415,12). In cellular component (GO: 0016020, 31 proteins) and in molecular function (GO: 0005524, 56 proteins, GO: 0009408, 21 proteins) the above shown were the most represented GO terms. In experiment three, physiological assessment of temperature stress tolerance of selectively fertilized coconut hybrids was done. Pollen grains were collected from the selectively fertilized coconut palms during summer season. The pollen grains were incubated in specific pollen germination media and exposed to different temperature ranging from 35oC to 45oC for a period of 2 hours. The temperature at which only 20-30 % of pollen germinated was identified as the critical temperature stress for pollen germination. From the results obtained, both the selectively fertilized hybrid of Kerasree and Keraganga were noted with maximum critical temperature for pollen germination (42oC) followed by WCT (40oC).This indicated 200 the temperature stress tolerance of selectively fertilized hybrids over their normal hybrids. Pollen viability was found maximum in WCT followed by Kerasree selectively fertilized hybrid. Accumulation of starch was found significantly higher in Kerasree selectively fertilized hybrid and the protein in WCT. The fourth experiment was conducted to screen temperature stress tolerance of 30 coconut genotypes in Regional Agricultural Research Station, Pilicode for recognizing the temperature stress tolerance through critical temperature for pollen germination. Significant genetic variation in critical temperature was discerned among the treatments. Andaman ordinary and Tanjore coconut genotypes were observed with higher critical temperature (42oC) for pollen germination. Hence they can be used as a pollen parent in hybridization programs for developing temperature stress tolerance. The present study revealed that Kerasree selectively fertilized and Keraganga selectively fertilized hybrids of coconut were more tolerant to water stress than normal hybrids in terms physiological, biochemical and molecular parameters. Selectively fertilized hybrids developed through pollen selection at critical water potential also have temperature stress tolerance. By selective fertilization techniques it may be possible to add water stress and temperature stress tolerance traits to high yielding coconut hybrids.Item Evaluation of sesame genotypes for tolerance to waterlogging and development of mitigation strategies(Department of Plant Physiology, College of Agriculture, Vellanikkara, 2021-10-18) Sreepriya, S; Girija, TThe present study was initiated to identify constraints of sesame farmers in Kerala, to screen sesame genotypes for tolerance to waterlogging, identification of suitable ameliorative treatment for waterproofing sesame, molecular characterization of sesame genotypes with genes and markers reported for waterlogging tolerance and screening for drought tolerance. Sesame growing farmers were surveyed in three districts of Kerala viz., Alappuzha, Kollam and Thrissur during 2018. Data was analyzed using Garrett ranking technique. Identified constraints were high labour cost, excessive rain fall, drought, weed infestation, unavailability of labour, pest and disease, marketing problem, problems for transportation, drying and threshing, and storage problems in decreasing order of their Garrett rank.Item High temperature medicated changes in sugar signaling pathway and identification of associated microsatellite markers in rice (Oryza sativa L.)(Department of Plant Physiology, College of Agriculture, Vellayani, 2022-10-02) Stephen Kukkamudi.; Beena RThe research work entitled ‘High temperature mediated changes in sugar signaling pathway and identification of associated microsatellite markers in rice (Oryza sativa L.)’ was undertaken at the College of Agriculture, Vellayani during 2018-2022. The aim of the study was to understand the effect of high temperature stress on the changes in the sugar signaling pathway and to identify the molecular markers associated with heat tolerance in rice. The investigation was carried out as four experiments, the first being the study of heat stress effects on the sugar signaling pathway, and the remaining three experiments being interconnected. The second experiment was the laying of crossing blocks to produce F1 and F2 generation seeds, after which the third experiment was conducted to phenotypically evaluate the F2 population derived from the second experiment. The fourth experiment was conducted to identify polymorphic micro-satellite markers that were associated with heat tolerance in the F2 population evaluated in the previous experiment. In the first experiment, the genotypes NERICA L-44 (NL-44) and Vandana were evaluated under two different temperature conditions viz. high temperature stress (38-42 ˚C) and ambient (26-34 ˚C) which was taken as control. The expression of four genes viz. OsHXK2, OsSnRK1, OsTOR and OsTPS1 was studied using quantitative real-time polymerase chain reaction (qRT-PCR) at the vegetative phase just before panicle initiation and at the grain filling stage. The results of the experiment showed that under high temperature stress conditions, the performance of the variety NL-44 was superior to the variety Vandana, as measured by parameters such as cell membrane stability index (+10%), pollen viability (+19%), panicle length (+4.8 cm), photosynthetic rate (+4.75 µmol cm-2 s - 1 ), stomatal conductance (+0.027 mol m-2 s -1 ), spikelet fertility (+19.1%), 1000 grain weight (+5.5 g) as well as greater photochemical efficiency (Fv/Fm ratio), maximal quantum yield (ΦPSII), electron transport rate and higher water-use efficiency. The results of the experiment clearly reinforce the tolerance characteristics of NL-44 and establish the susceptibility of Vandana to high temperature stress. The expression of each gene was correlated with multiple traits that explained the tolerance or susceptibility of the genotypes 204 under heat stress. Based on such correlations, the proposed pathway of sugar signaling in tolerant rice genotypes should necessarily cause upregulation of OsHXK2, as it indicates high glucose content; down-regulation of OsSnRK1, as it would prevent the induction of catabolic processes; up-regulation of OsTOR, as it indicates higher nutrient status as well as being involved in inducing stress responses; and down-regulation of OsTPS1 as the low T6P content would signal remobilization of nutrients towards stress response. In the second experiment, the two varieties NL-44 (heat-tolerant) and the high yielding Uma (heat-susceptible) were crossed to produce F1 generation hybrids. The F1 seeds were then selfed to produce F2 generation seeds. The F2 seeds produced had morphological characters that were intermediate to the parents with medium length and medium boldness unlike NL-44 which was long and slender grain whereas Uma has characteristic short and bold grain characteristics. 144 F2 plants along with the parents, NL-44 and Uma were phenotypically evaluated under high temperature stress (36-40 ˚C) in the third experiment. . The mean of the population was closer to NL-44 with regards to the traits of plant height, membrane stability index, photosynthetic rate, stomatal conductance, transpiration rate, pollen viability, spikelet fertility and 1000 grain weight. However, for the traits such as tiller number, days to flowering, time of anthesis, leaf temperature and panicle length, the mean of the population was influenced by the susceptible parent, Uma. Based upon the spikelet fertility percentage, the ten most tolerant and ten most susceptible plants were selected from the F2 plants and Bulked Segregant Analysis (BSA) technique was used to identify polymorphic SSR markers that are linked to high temperature tolerance. The results of the study have identified 18 SSR markers that exhibited polymorphism between the parents out of the 100 SSR markers used. The identified polymorphic markers could distinguish between the tolerant and susceptible bulks as seen in their differential banding pattern. The identified polymorphic markers were also found to segregate between the individual lines and characterize them into tolerant or 205 susceptible lines based on their similarity to the banding pattern of the tolerant parent, NL44 or the susceptible parent, Uma. In the present study, the expression levels of the sugar signaling genes and their association with phenotypic characters has elucidated their role in imparting heat tolerance in rice. The phenotyping of the F2 generation indicated that the tolerance traits in the population were majorly contributed by the tolerant parent i.e. NL-44. The identified polymorphic markers were able to segregate the individual lines of F2 population into tolerant and susceptible genotypes. The elucidation of the sugar signaling mechanism in tolerant genotypes of rice and the association of molecular markers linked to the heat tolerance trait in the segregating second generation filial populations is validated to be beneficial in undertaking crop improvement studies for enhanced sugar metabolism as well as to introgress the tolerance traits into high-yielding regional varieties.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.Item Evaluation of CO2 enrichment on growth, development and soft rot tolerance in ginger (Zingiber officinale Rosc.)(Department of Plant Physiology, College of Agriculture, Vellayani, 2021) Manasa, R; Manju, R VThe present investigation entitled “Evaluation of CO 2 enrichment on growth, development and soft rot tolerance in ginger (Zingiber officinale Rosc.)” was undertaken with the objective to assess the impact of elevated CO 2 on growth, yield, quality and tolerance to soft rot in ginger through morphological, physiological, biochemical and molecular analysis. Two sets of pot culture experiments were conducted during 2017- 2019. The technology utilized for CO 2 enrichment was Open Top Chamber (OTC) system established under Department of Plant Physiology, College of Agriculture, Vellayani. In the first experiment three varieties of ginger Aswathy, Athira and Maran were utilized to assess the impact of elevated CO 2 on growth, yield and quality of ginger. One set of three month old plants were shifted to OTC and another set was retained under ambient CO 2. The plants were harvested at 4 th , 5 th , 7 th and 8 th months after planting (MAP). Observations on growth, physiological and biochemical parameters were recorded at each harvest. Yield, yield parameters, tissue nutrient status and quality parameters were assessed at 8 MAP. Second experiment was conducted to assess the impact of elevated CO 2 on tolerance to soft rot in three ginger varieties Aswathy, Athira, Maran and wild ginger congener Zingiber zerumbet. One set of three and a half month old plants were shifted to OTC and another set retained at ambient CO 2 and were challenged with Pythium aphanidermatum at 4 MAP. The CO 2 concentration of 500 ppm was maintained in the OTC. The results of the first experiment indicated an improvement in growth parameters like plant height, number of leaves, root weight, shoot weight, stem diameter and number of tillers, physiological and biochemical parameters like total chlorophyll, photosynthetic rate and total sugars in the rhizome by recording significantly higher values upon CO 2 enrichment when compared to ambient CO 2 condition. Significant reduction in transpiration rate, stomatal conductance and specific leaf area were recorded upon CO 2 enrichment. The per cent increase in yield parameters like number of fingers (38.19%), rhizome spread (11.32%), thickness (42.72%) and dry weight of rhizomes (31.43%) recordedhigher values upon CO 2 enrichment, based on average performance of all the selected varieties, leading to greater yield. The per cent increase in the fresh weight of rhizome recorded higher for variety Aswathy (38.34%), followed by Maran (20.00%) and Athira (12.12%) with a total fresh rhizome yield of 165.35 g plant -1 under ambient and 228.75 g plant -1 under elevated CO 2 condition in the case of Aswathy. Upon CO 2 enrichment the quality of rhizome was modified with increase in fiber (60.26%), gingerol (9.06%), phenol (19.25%), total oleoresin (11.52%), starch (44.84%) and essential oils (31.10%). Significant reduction in protein and nutritional status in the rhizomes were also recorded. Nitrogen, potassium, iron and zinc contents decreased by 15.78%, 3.22%, 11.78% and 18.57% respectively. Phosphorous and copper showed decrease in trend though not significant. Among the three varieties of ginger, Aswathy was found to be performing better compared to Athira and Maran not only in terms of yield, also for majority of quality parameters assessed upon exposure to elevated CO 2 condition. In the case of impact of elevated CO 2 on soft rot development, there was no variation in the per cent disease incidence. However, lesser number of days was taken for development of symptom. The per cent disease index was reduced by 11.10% upon CO 2 enrichment. The reduction in the fresh weight of rhizome upon pathogen inoculation was also less under elevated CO 2 (14.34%) when compared to ambient CO 2 (17.60%) showing that increasing CO 2 levels might bring down the disease severity. Upon P. aphanidermatum inoculation, the retention of photosynthetic pigments like chlorophyll a (0.90 mg g -1 FW) chlorophyll b (0.74 mg g -1 FW) total chlorophyll (1.64 mg g -1 FW) carotenoids (0.58 mg g -1 FW), xanthophyll (0.40 mg g -1 FW) and photosynthetic rate (5.92 μmol CO 2 m -2 s -1 ) were higher under elevated CO 2 when compared to ambient CO 2 . Higher membrane integrity values and lower malondialdehyde (0.75 μg g -1 FW) content in all the selected varieties were evident upon pathogen inoculation under CO 2 enrichment. Enhanced activity of ascorbate peroxidase (4.86 activity Units mg -1 total protein), PAL (Phenylalanine ammonia lyase) (20.91 Units mg -1 total protein), and glucanase (4.57Units mg -1 total protein) activity, as well as higher accumulation of phenols (32.40 mg g -1 DW) and ascorbic acid (7.14 mg 100 g -1 FW) were found in the inoculated plants under CO 2 enrichment compared to the ambient CO 2 . The catalase activity was found to reduce upon pathogen inoculation and the reduction was higher (0.11 Units mg -1 total protein) under ambient CO 2 as compared to elevated CO 2 (0.09 Units mg -1 total protein). Highest levels of hydrogen peroxide, superoxide and cell death were observed upon pathogen inoculation under ambient CO 2 through staining techniques and it was highest for variety Aswathy and least for Z. zerumbet. After pathogen inoculation maximum values for variable to maximum fluorescence Fv/Fm (0.63), photosynthetic electron transport rate (82.60 micro equiv m -2 s -1 ) and quantum yield of PS II photochemistry (0.29) were recorded under elevated CO 2. Protein profiling performed in varieties Athira and Aswathy revealed lower expressions of 20-25 kDa and 25-35 kDa protein under pathogen inoculation in variety Aswathy. The expression of 55 kDa (Rubisco Large Sub- Unit) was down regulated to a greater extent under pathogen inoculation in both the varieties. Higher expression levels of the defense responsive genes Phenylalanine ammonium-lyase (PAL), Cinnamyl alcohol dehydrogenase (CAD) and Chalcone synthase (CSH) were also observed upon pathogen inoculation under CO 2 enrichment in both the varieties. Between the varieties, Athira had higher relative fold changes of PAL, CAD and CSH under both ambient and elevated CO 2 upon pathogen inoculation. The present study revealed that CO 2 enrichment can improve the performance of ginger in terms of growth, yield and quality. It also indicates changes in photosynthetic allocation pattern and phytochemical profiles with enhanced contents of oleoresins and essential oils. Ginger plants showed better tolerance against P. aphanidermatum upon CO 2 enrichment. This was apparent in the form of reduced disease severity, oxidative stress level and less reduction in yield upon pathogen infestation under elevated CO 2 condition. This was evidently achieved through the activation of multiple mechanisms, including enhanced production of anti-oxidants and up regulation of pathogen resistance proteins. This is one of the first studies to comprehend on possible effects of elevated CO 2 on the susceptibility of ginger to soft rot. The study also demonstrated the varietal variations existing in the response to CO 2 enrichment which will help in selection ofsuitable varieties for changing climatic scenario. The information generated indicates the possibility of enhancing both qualitative and quantitative yield of ginger through low cost CO 2 enrichment technologies. The insights obtained on the tolerance mechanisms involved will help to restructure the soft rot disease management strategies in the coming future.Item Physiological biochemical and molecular studies in medicinal rice (Oryza sativa L.) njavara as influenced by abiotic stresses(Department Of Plant physiology, College Of Agriculture, Vellayani, 2020) Wagh Yogesh Sahebrao; Viji, M MItem Evaluation of CO 2 enrichment effects on resource utilization in cowpea and amaranathus(Department of Plant Physiology, College of Agriculture, Vellayani, 2019) Srikanth, G A; Manju, R VItem Marker assisted transfer of thermosensitive genic male sterility to high yielding red kernelled varieties of rice (Oryza sativa L.)(Department of Plant Physiology, College of Agriculture, Vellayani, 2015) Niya Celine, V J; Roy StephenThe project entitled “Marker assisted transfer of thermosensitive genic male sterility to high yielding red kernelled varieties of rice (Oryza sativa L.)” was conducted in the Department of Plant Physiology, College of Agriculture, Vellayani during 2011 to 2014. The main objectives were to develop molecular markers associated with TGMS gene and to transfer TGMS character to red rice background. For the present investigation, two TGMS lines were imported from International Rice Research Institute (IRRI) namely, TGMS1 and TGMS2which are from two different TGMS sources ID24 and IR32364 respectively. The TGMS lines along with two popular red rice varieties of Kerala, Uma and Jyothi were sown on monthly intervals for their initial phenological study. The critical sterility temperature and period of TGMS lines were characterised in the field using tracking method. The activity of antioxidant enzymes plays an important level in causing sterility in rice pollen grains, though the reason behind male sterility is unknown. Morphological, agronomic and floral traits were studied during the specific crop growth stage and were recorded as per the standard evaluation systems given by IRRI. Phenological, floral and morpho-agronomic characterisation of TGMS lines revealed that the line TGMS1 performed better with short stature, early maturity, more productive tillers, wider glume opening, higher panicle and stigma exertion, more filled grains and longer panicles. Stages of panicle development were determined by various methods viz., physical method, morphological index method and tracking method. The results have shown that TGMS1 is a better candidate for Kerala condition with critical sterility period of 15-22 days before heading and the sterility inducing average temperature of 27.25 o C. For hybridisation, TGMS1 plants were grown under sterility inducing condition and they were crossed with a popular red rice variety, Uma to produce F1. The F1 s were then selfed to get F2 population. A gene specific primer was designed for the red pericarp colour (Rc) which can be used as a background selection marker. Fifty F2 plants were used for marker analysis. Microsatellite analysis was done to find out the SSR markers polymorphic to the tms gene. DNA was isolated from the 50 F2 plants and performed PCR using 45 SSR markers. Capillary electrophoresis was done for the allele sizing of PCR products. Among 45 SSR markers used, three primers RM 3351, RM23 and RM31 could differentiate Uma, Jyothi andTGMS1, TGMS2. A set of twenty one primers were able to distinguish TGMS1 and Uma. The F2 plants sterile as per the TGMS markers were found to be sterile under sterility inducing condition. Under low temperature their fertility was transformed indicating the presence of tms gene. Linkage analysis using MAPMAKER version 3.0, seven linkage groups and a few unlinked primers were found. A segregation ratio of 2.57:1 was obtained between fertile and sterile lines. This ratio explains the monogenic nature of tms gene.Among 20 polymorphic markers, six (RM23, RM31, RM3351, RM 212, RM258 and RM244) were found significant. These on further analysis using χ 2-test revealed the possible association between the sterility phenotype and marker. From the present study, the sterility tms gene got successfully transferred into 14 sterile F2 plants and RM31, RM23, RM3351, RM212, RM244 and RM258 can be used for the evaluation of TGMS1 X Uma hybrids and their F2s.