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

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    Impact of biofertilizers and nutrients on the quality and shelflife of tomato (Solanum lycopersicum L.) and on the fruit shelflife regulator (SIFSR) gene expression under elevated CO2 condition
    (Department of Plant Physiology, College of Agriculture , Vellayani, 2024-03-16) Haripriya, S.; Manju, R V
    The study entitled “Impact of biofertilizers and nutrients on the quality and shelflife of tomato (Solanum lycopersicum L.) and the Fruit Shelflife Regulator (SlFSR) gene expression under elevated CO2 condition” was undertaken with the objective of elucidating the effects of biofertilizers and nutrients on the quality and shelf-life of tomato and the Fruit Shelf-life Regulator (SIFSR) gene expression under elevated CO2 condition. The experiment was conducted using the Open Top Chamber (OTC) system facility in the Department of Plant Physiology, College ofAgriculture, Vellayani during 2022-2023. In the experiment, quality and shelf-life of tomato under elevated CO2 environment, as influenced by nutrients and biofertilizers were evaluated. The experiment was laid out in CRD consisting 5 treatments with three replications under ambient and elevated conditions. The treatments comprised of T1: POP, KAU+AMF, T2: POP, KAU+ PGPR Mix-1,T3: POP, KAU+Azolla T4: POP, KAU+50 ppm B + 50 ppm Zn+60 ppm Ca water spray (40, 55 and 70 DAS.) and T5: POP,KAU Control. The experimental results revealed, plant height after 75 days of sowing, specific leaf area and total dry matter increased significantly under elevated CO2 condition. Foliar spray with 50 ppm B + 50 ppm Zn + 60 ppm Ca along with POP, KAU recommendation recorded the highest plant height at 75 DAS. AMF treated plants were found to improve specific leaf area at 60 DAS and 75 DAS. Root to shoot ratio was reduced under elevated CO2 condition compared to ambient condition. Among the treatments, soil incorporation of PGPR before transplantation of seedlings resulted in the highest accumulation of dry matter. Among the physiological and biochemical parameters, total chlorophyll content, total carbohydrate content and chlorophyll stability index recorded higher values under elevated CO2 compared to open condition. However, a significant reduction was noted in total soluble protein content under elevated CO2 compared to open condition. PGPR mix 1 treated plants had recorded the highest chlorophyll and total carbohydrate content but plants foliar sprayed with 50 ppm B+50 ppm Zn+60 ppm Ca recorded the best results with respect to chlorophyll stability index. Exposure to elevated CO2 was found to increase the days for first flowering. Application of biofertilizers and nutrients reduced the days to flowering significantly. Plants came to flowering 40 DAS in the cases of PGPR mix-1 treated plants under eCO2 and AMF treated plants under aCO2. Due to high temperature associated with CO2 enrichment, pollen viability was lost and there was no fruit production inside OTC. Yield parameters such as number of fruits, fruit weight, fruit setting percentage and yield per plant showed significant difference among treatments. Among the treatments, PGPR mix-1 treated plants recorded significant increase in fruit weight, number of fruits and yield. Application of biofertilizers and nutrients had significant impact on quality of fruit and the most effective treatment was incorporation of PGPR mix-1 along with POP, KAU in terms of increased accumulation of lycopene, β-carotene, vitamin C, total sugars, pectin, moisture content, shelf-life and reduced physiological loss in weight. Foliar spray had the same impact as that of PGPR mix-1 treatment in the cases of vitamin C and beta carotene contents. Though AMF was found to increase P content of the fruits significantly, Fe content in fruits was influenced by foliar sprayed and PGPR mix-1 treatment.CO2 enrichment was found to have no influence on expression levels SlFSR gene in leaf tissues but the application of biofertilizers and nutrients was found to affect expression levels in fruits. Lowest level of expression was noted in fruits collected from azolla treated plants under ambient condition. The increase in atmospheric temperature due to increasing CO2 concentration can hasten perishability in the case of farm products. Efforts towards shelf-life extension to make fruit safe for long periods, keeping its original quality is of paramount importance today. The present programme clearly indicates that the shelf-life of tomato variety Vellayani Vijay can be enhanced by 85% through the soil incorporation of PGPR mix-1 before transplanting. This is a great achievement considering the higher perishability of tomato. Application of the biofertilizer, azolla which resulted in the 22.22% increase in shelf-life lead to down regulation of the GRAS transcriptional factor, SlFSR which controls fruit shelf-life by regulating expression of cell wall modifying genes and metabolism of pectin and cellulose. The significant extension of shelf-life achieved through the application of PGPR and AMF could be mediated through the down regulation of ethylene biosynthesis and cell wall degrading enzyme activities. Combined application of calcium, boron and zinc contributes towards firmness of fruit tissues and extended shelf-life to the same degree. The findings of the present programme revealed that application of azolla, PGPR mix-1 and AMF and combined application of calcium, boron and zinc improved the quality and shelf-life of tomato significantly. The result also proves SlFSR gene as a potential biotechnological target for the control of fruit shelf-life. The outcome of the programme will help to develop agricultural practices for improving the shelf-life and quality of tomato which is of paramount importance in the scenario of increasing atmospheric temperature and climate change.
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    Management of elevated CO 2 induced high temperature through nutrient and biofertilizer application in tomato (Solanum lycopersicum L.)
    (Department of Plant Physiology, College of Agriculture , Vellayani, 2021-12-17) Arunima, A S; R V, Manju
    The study entitled “Management of elevated CO 2 induced high temperature through nutrient and biofertilizer application in tomato (Solanum lycopersicum L.)” was undertaken with the objective of improving flowering and fruit set of tomato under elevated CO 2 condition through nutrient and biofertilizer application. The experiment was conducted using the Open Top Chamber (OTC) facility at the Department of Plant Physiology, College of Agriculture, Vellyani during 2020-2021. In the experiment, flowering and fruiting in tomato under elevated CO 2 environment, as influenced by nutrients and biofertilizers were evaluated. The experiment was laid out in CRD with nine treatments and three replications. The treatments comprised of T 1 :50 ppm B + 50 ppm Zn + water spray, T 2 :75 ppm B + 75 ppm Zn, T 3 : POP 150% N:125%P:125% K, T 4 : Azolla (soil application), T 5 :Azolla biofertilizer extract (20%) (foliar application), T 6 : Azolla biofertilizer extract(20%)(seed treatment), T 7 :POP, KAU+ PGPR1, T 8 : Control (water spray) and T 9 : Absolute control. Experimental results revealed that plant height, number of branches, number of leaves and specific leaf area increased significantly under elevated CO 2 condition at 75DAS. Among the treatments, foliar spray with 50ppmB+50ppm Zn+ water spray at 40, 55and 70 DAS recorded higher plant height (57.56%) at 75DAS. Nutrient application of 150%N:125%P:125%K found to improve the number of branches (91.82%), leaves (98.56%) and specific leaf area (40.03%) at 75DAS. Among the physiological and biochemical parameters, total chlorophyll content, total carbohydrate, photosynthetic rate, water use efficiency, chlorophyll fluorescence, chlorophyll stability index and proline content recorded higher values inside OTC compared to open condition. However, a significant reduction was noted in transpiration rate and total soluble protein content inside OTC compared to open condition. The foliar spray of 50ppm B+50ppm Zn+ water spray recorded high values for chlorophyll content (1.58 mg g -1 ) and cell membrane stability index (53.83%) compared to open condition at 75DAS. The application of POP 150% N:125% P:125% K recorded significantly higher photosynthetic rate (21.03μmol CO 2 m -2 sec -1 ), total carbohydrate(50.04mgg -1 ), chlorophyll stability index(135.38%) and chlorophyll fluorescence (0.74Fv/Fm). Also foliar application of 20% Azolla biofertilizer extract was found to significantly improve the relative water content (96.15%) and water use efficiency(6.82 mmol CO 2 mol -1 H 2 O) in tomato plants under elevated CO 2 conditions. Inside OTC, flowering delayed by 2 days and the total number of flower clusters (5.96) also increased compared to control (4.12). Reduction in pollen viability (82.42%) observed at higher CO 2 compared to control. But it was found to improve under treatment T1 (50ppm B+ 50ppm Zn + water spray) which resulted in highest fruit setting percentage (53.01%) as against the control (39.92%). Fruiting was delayed by 3 days inside OTC. However, the fruit weight was found to increase with water spray (54.46%), extra NPK(55.89%) and foliar spray of 50ppm B+ 50ppm Zn+ water spray(57.51%). Foliar application of Azolla biofertilizer extract (20%)(T5), 150% N:125% P:125% K(T3) than the recommended dose, as well as foliar application 50ppm B + 50ppm Zn+ water spray (T1) improved the yield per plant by 55.79%, 63.08% and 65.22% respectively compared to control. All these treatments also improved the quality parameters like lycopene, vitamin C, beta carotene and minerals (P, Fe) in tomato fruits under elevated CO 2 condition. The present study indicated the improved performance of tomato variety Vellayani vijay upon exposure to elevated CO 2 . But flowering, fruit set and ultimately the total yield were negatively influenced by elevated CO 2 induced high temperature. The impact of application of extra N, P and K than the recommended doses as well as foliar application of B and Zn indicate the changing nutrient requirement of tomato under the current scenario of increasing atmospheric CO 2 concentration. The response of experimental plants to foliar application of Azolla extract (20%) strongly suggest the effectiveness of this biofertilizer in overcoming the impacts of elevated CO 2 induced high temperature and thereby improving the plant performance. Recommendations based on the best treatments can be developed by extending the study to field condition since the treatments were found to improve the yield and quality even under ambient condition
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    Management of button shedding in coconut by root feeding of nutrients and growth regulators
    (Department of Plant Physiology, College of Agriculture , Vellayani, 2021-12-13) Shanmugapriya, D; Roy Stephen
    The study entitled “Management of button shedding in coconut by root feeding of nutrients and growth regulators” was conducted to determine the physiological management of button shedding in coconut by using nutrients and growth regulators through root feeding and to determine the role of beneficial microbes on auxin production in coconut. Two experiments were conducted at Coconut Research Station, Balaramapuram during 2020-2021. Survey was conducted for the first experiment to select the palms with uniform age having significant button shedding. The respective solutions were prepared and administered to the palms through root feeding. The yield parameters, biochemical and physiological parameters were estimated and recorded for the first six months. The results shown that the yield parameters such as the number of female flowers and the number of buttons retained showed non siginificant variation in all the treatments. The percentage of button shedding also showed non siginificant variation during 5th and 6th month. Among the 7 treatments, T2 [Hoagland solution - 2X] reported the lowest button shedding percentage (22.9, 24.2, 28.4 and 31.1%) for the first four months respectively followed by T6 [Salicylic acid-200ppm] and T5 [Borax (0.5 g palm-1 ) + 2, 4- D (50 ppm)] .T1 [Control] reported the highest level of button shedding percentage (32.88, 37.21, 44.25 and 50%) for the first four months respectively. The physiological parameters such as transpiration rate shown the highest level (3.8, 4.0, 4.3, 4.2, 4.3, 4.4 mmol H2O m-2 sec-1 ) in the T2 treatment followed by T6 respectively for the first six months. T2 reported the maximum photosynthetic rate (4.4, 4.6, 4.9, 4.8, 4.9 and 5.2 µmol CO2 m-2 sec-1 ) for a period of first six months respectively which was on par with T6. T1 reported the minimum photosynthetic rate and transpiration rate for the first six months. The biochemical parameters such as carbohydrate content was maximum (21.84,79.65, 77.42, 84.33,96.66 mg g-1 ) in the T2 treated palms respectively except 2nd month. There was no significant variation in between the treatments during 2nd month. The macronutrients such as N (2.07, 2.26, 2.5, 2.37, 2.41, and 2.54 %), K (1.27, 1.46, 1.7, 1.65, 1.87, 2.14%), Mg (1.56, 1.74, 1.95, 1.6, 1.78, and 1.89 %), Ca (0.57, 0.88, 1.05, 0.88, 1.08 and 1.16%) and S (0.57, 0.75, 1.06, 0.86, 1.01 and 1.19%) were higher in T2 treated palms respectively for six months. T7 [SA (200 ppm) + 2, 4- D (50ppm)] recorded the maximum phosphorus content (0.13, 0.14, 0.18, 0.08, 0.15, and 0.22 %) during the observation of first six months respectively. Micronutrients such as Fe (158.5, 175.45, 240, 234, 258.33 and 275.66 ppm), B (15.06, 19.16, 26.93, 20.33, 25.33 and 31.33ppm) and Mn (169.55, 179.66, 188.66, 181.92, 186.66 and 195.33 ppm) was also higher in the T2 treated palms for the first six months respectively. Except 1st month, T2 reported higher copper content (54, 67.66, 61.66, 71, 81.33ppm) from 2nd to 6th month. T5 [Borax (0.5 gm palm-1 ) + 2, 4- D (50 ppm)] reported the highest Zinc content (42.33, 43.9, 55.34, 46.43, 53.32 and 62.06 ppm) for the first six months respectively. T1 reported the lowest level of carbohydrate content and nutritional (macro and micro) content in the leaf during the six months period. The second experiment was performed to evaluate the role of beneficial microbes on auxin production in coconut. Piriformospora indica vermiculite mixture and Rhizobium radiobacter suspension were prepared and inoculated in the 3 months old coconut seedlings and the colonization was evaluated after 15 days of inoculation and recurred until the result was obtained. The results revealed that the chlamydospores similar to the P. indica were colonized in the cortex region of the root hairs of the coconut seedlings. Colonization of Rhizobium radiobacter were not observed in the roots of coconut seedlings. In coconut, considerable loss in yield had been observed due to the phenomenon of shedding of buttons. It varies from 55 to 95 per cent depending on the conditions prevailing, and on the variety of the coconut. In my study, root feeding of Hoagland solution (2X) recorded 43.03, 53.6, 55.7, 60.7% lower button shedding percentage over the control during the first four months respectively. Salicylic acid-200 ppm and [Borax (0.5 g palm-1 ) + 2, 4- D (50 ppm)] was also able to control the button shedding effectively.
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    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 Stephen
    The 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.
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    Deciphering the mechanistic role of plant neurotransmitters in rice
    (Department of Plant Pathology, College of Agriculture ,Vellayani, 2024-01-15) Sharmila, S; Parvathi M Sreekumar
    Rice, a fundamental dietary staple food for over half the global population, particularly in developing nations. It has developed intricate and sophisticated mechanisms to confront environmental stresses such as drought, heat and salinity. In response to stress conditions, rice plants showcase diverse adaptive strategies. Melatonin and dopamine serve as pivotal signaling molecules, contributing significantly to diverse physiological processes in plants, alongside stress ameliorative potentials. The present study was aimed at deciphering the mechanistic roles of these plant neurotransmitter-like ameliorants in rice. The first experiment was conducted at the Department of Plant Physiology, College of Agriculture, Vellanikkara laid out in a Completely Randomized Design (CRD) with nine treatments, with three replications. Rice seedlings were exposed to three stressors in petriplates namely Methyl Viologen (MV; 2.5 μM and 5 μM for oxidative stress), Dithiothreitol (DTT; 2.5 mM and 5 mM for endoplasmic reticular stress) and Antimycin A (ANT A; 10 µM and 20 µM for chloroplast and mitochondrial stress). Melatonin and dopamine, at concentrations of 100 µM and 0.4 µg/mL, respectively, were used to investigate their ameliorative potentials against the three stressors. The study examined various traits such as growth patterns, biochemical changes and stress tolerance mechanisms to elucidate the potential protective or ameliorative effects of melatonin and dopamine under the given stress conditions. The seedling assays indicated that the growth of non-stressed ameliorant-treated seedlings exceeded that of stressed ones. Dopamine was effective in mitigating damage caused by oxidative and ER stress, while melatonin demonstrated superior performance in alleviating chloroplast and mitochondrial stress. Malondialdehyde (MDA) content increased significantly under oxidative stress induced by 5.0 μM MV treatment and decreased in the control. Under ER stress, MDA was higher in DTT treated seedlings @ 2.5 mM with (84.13%) and without (94.83%) dopamine. In chloroplast and mitochondrial stress, MDA levels were 25.6% and 82.5% lower in dopamine-treated seedlings stressed with ANT A @ 10 and 20 μM, respectively. Histochemical observations revealed that, methyl viologen induced damage elevated ROS production, as indicated by prominent staining in stressed seedlings, with an ameliorant specific scavenging activity in shoots (melatonin) and roots (dopamine). Noticeably, dopamine outperformed melatonin at higher ER stress levels, in maintaining shoot and root growth, whereas t in chloroplast and mitochondrial stress, dopamine and melatonin had distinct roles in shoot and root growth maintenance, respectively. The second experiment was carried out in pots at the nethouse facility, Department of Plant Physiology, College of Agriculture, Vellanikkara, in Completely Randomized Design (CRD) with three replications. One month old rice plants were subjected to four treatments namely a mock/absolute control, Tween-20 (0.05%), Melatonin (100 μM) and Dopamine (0.4 μg/mL). Both dopamine and melatonin treatments constitute Tween-20 as a surfactant. Results indicated that the ameliorants have a distinct physiological role in stress alleviation over control. Plant height variations indicated a more significant increase with Tween-20, followed by melatonin and dopamine, compared to the unsprayed control. Ameliorant treated rice showed enhanced chlorophyll levels, with the highest content observed in Tween-20-treated plants, followed by melatonin and dopamine treatments. Likewise, dopamine treatment resulted in a higher net photosynthetic rate than melatonin, while Tween-20-treated plants displayed the highest net photosynthetic rate and stomatal conductance among all treatments. Soluble sugar and protein contents were on par across the four treatments. The research also focused on exploring the response of noble prize-winning mechanosensitive ion channel receptors such as TRPV1 and PIEZO mediating human sensory perception of temperature, touch, and cold, to exogenous application of melatonin and dopamine. Acknowledging the potential involvement of plant neurotransmitter-like molecules like melatonin and dopamine in orchestrating sensory responses, the study delved into the plant homologs of these receptors. Phylogenetic analysis of TRPV1 with diverse species indicated a 33% homology between Oryza sativa and Homo sapiens. Further, in silico expression analysis of TRPV1 under diverse stress conditions using the ePlant Stress Expression Browser was studied and interpreted. Mechanosensory receptor expression signatures (OsPIEZO, OsTRPV1, OsPMTR1) and basal transcriptional regulator responsiveness (OsTAF2, OsTAF4, OsTAF6, OsTAF9A, OsTAF9B, OsBTF3), were examined in melatonin and dopamine treated rice leaf tissues. OsTAF4, OsTAF6, OsTAF9A, OsTAF9B, OsBTF3, OsPIEZO, OsTRPV1 and OsPMTR1 were upregulated in dopamine-treated plants (0.4 µg/mL) compared to control, whereas OsTAF4 and OsTAF6 showed similar expression patterns under both dopamine and melatonin administration. OsTAF2 exhibited higher expression in Tween-20 treated leaf tissues. With dopamine treatment, OsTAF9B, OsPIEZO and OsPMTR1 displayed nearly three-fold change in transcript levels over control. OsTRPV1 exhibited one- and two-fold changes under melatonin and dopamine treatments, respectively, marking the first report of mechanosensory receptor responsiveness to plant neurotransmitter-like molecules in rice.
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    Elucidation of hormonal physiology underlying the differential response of indica and japonica rice to in vitro system
    (Department of Plant Physiology, College of Agriculture ,Vellanikkara, 2024-01-19) Anubharathi, K.; Krishna Kumar, G
    World is running towards 9 billion population by 2050 along with two serious issues in its hand– climate change and food insecurity. It can ultimately hamper the world to achieve Sustainable Development Goals (SGDs). High yielding and climate resilient crops are crucial towards accomplishing SDGs. Half of the world population relies on rice and it is also a model monocot crop which is widely used for the study of various crop improvement programs. Indica rice is the widely cultivated genotype across India. Improvement in quantitative and qualitative traits of rice is very important to battle against hunger and malnutrition. Micropropagation takes the lead towards crop improvement through various biotechnological approaches. In indica there is a research gap due to recalcitrant calli which is poor to regenerate under micropropagation conditions. The present study was undertaken to dissect the reason behind this limitation in indica. In the current study, IR64 an indica genotype along with a check japonica genotype, Nipponbare were used. The manually dehusked surface sterilized seeds were inoculated in the callus induction media with various dosages of 2,4-D (0, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 mg/L). The response of the seeds to 2,4-D was examined by callus induction frequency (%), callus size (mm), and fresh and dry weight of callus (g). The calli from 3 mg/L 2,4-D had maximum callus induction frequency in IR64 while in Nipponbare it was 100 % at 1.5 mg/L 2,4-D. The size, fresh weight and dry weight of the callus was maximum at 3 mg/L of 2,4-D in both genotypes. Calli from IR64 was compact and larger than that of Nipponbare. Considering all the dosages, calli from 3 mg/L 2,4-D performed best in both genotypes. The maximum size and weight might be the due to aggressive cell division and growth of the calli. This uncontrolled cell division can possibly affect the development of embryogenic calli. Hence calli from suboptimal concentration i.e., 2.5 mg/L of 2,4-D was selected for regeneration process. Two to three week old calli from 2.5 mg/L 2,4-D were transferred to two regeneration media. The first media was supplemented with 0.05 mg/L NAA and 2, 2.5, 3 mg/L BAP, kinetin and the other with 0.5 mg/L NAA with same concentration of cytokinins as in the first set of treatments. The differential response of the callus to the media was determined by recording the number of green calli, shoots, brown and hairy calli, chlorophyll and carotenoid content, secondary metabolites, and endogenous hormonal homeostasis. In general, green calli were more in the media with 0.5 mg/L NAA in both genotypes. IR64 had maximum number of green calli at 0.5 mg/L NAA with 3 mg/L BAP and Nipponbare at 0.05 mg/L NAA with 3 mg/L BAP. No shoots were regenerated from IR64 in both regeneration media types tested. In the media with 0.5 mg/L NAA shoots from Nipponbare were regenerated. Number of brown calli were more in IR64 than Nipponbare in both media. Maximum number of brown calli were found in the media with 0.05 mg/L NAA in IR64. Total number of hairy calli were higher in Nipponbare than in IR64 irrespective of the media. Chlorophyll content in IR64 was maximum at 0.05 mg/L NAA and in Nipponbare at 0.5 mg/L NAA. In both cases, media with BAP had maximum chlorophyll content. Carotenoid content was high in IR64 at 0.05 mg/L NAA. In the media with 0.5 mg/L NAA, higher carotenoid was found at BAP in IR64 and kinetin in Nipponbare. Secondary metabolites had both positive and negative roles in the regeneration of calli. Total phenols were significantly high at 0.05 mg/L in IR64 than at 0.5 mg/L NAA. Nipponbare had maximum phenol content at 0.05 mg/L NAA and 3 mg/L BAP and with no significant difference in other treatments for both the media types. Alkaloid content of calli was collectively less in the media with 0.5 mg/L NAA than 0.05 mg/L NAA. In IR64 the alkaloid content exhibited a two-fold increase at 0.05 mg/L NAA. Nipponbare maintained steady alkaloid content in almost all treatments in both media. As auxin and cytokinin ratios are critically important, in this study auxin content and IAA oxidase activity were determined. Higher auxin content in both genotypes has recorded at the media supplemented with 0.05 mg/L. In the media 0.5 mg/L NAA the auxin content was reduced in IR64 and also had improved auxin homeostasis. After four weeks, shoots of Nipponbare were transferred to the ½ x MS media without NAA and 0.5 mg/L NAA. The efficacy of the rooting media was determined by observing root number, total root length, dry weight of roots and shoots. Media without hormone failed to produce roots however the media with 0.5 mg/L NAA had the positive effect of rooting irrespective of the shooted calli from different treatments. The present study points that IR64 exhibited considerably good green calli number, better accumulation of chlorophyll content than Nipponbare. But better regeneration of Nipponbare may be attributed to its friable nature of the calli along with steady maintenance of the secondary metabolites and auxin content. The poor performance of IR64 might be due to higher levels of phenolics and alkaloids accumulation. These findings also give insights into the importance of auxin-cytokinin signaling crosstalk and auxin transport during shoot regeneration.
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    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, R
    The 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.
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    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, T
    The 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.
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    Elucidating the role of growth promoting endophytic fungus Piriformospora indica for water stress tolerance in rice (Oryza sativa L.)
    (Department of Plant Physiology, College of Agriculture, Vellayani, 2022-10-03) Lekshmi Mohan S; Beena R
    The research work titled “Elucidating the role of growth promoting endophytic fungus Piriformospora indica for water stress tolerance in rice (Oryza sativa L.)” carried out at Department of Plant Physiology, College of Agriculture, Vellayani during 2020-2021 with the objective to elucidate the changes in morphological, physiological, biochemical and molecular mechanisms associated with water stress tolerance in Piriformospora indica-colonised rice. The roots of Ptb 23, Ptb 24, Ptb 29 and Ptb 30 varieties’ seedlings were appraised microscopically for root colonisation after germinating in trays containing P. indica-infused composted coir pith- cow dung (1:1) mixture maintained in temperature and humidity-controlled conditions. Isolated or chains of double walled pear shaped chlamydospores were observed in the root sections of seedlings in trays with P. indica after seven days of cocultivation. On treatment with Poly Ethylene Glycol (PEG) 6000 at concentrations of 0, 5,10, 15, and 20 per cent, the varieties on root colonisation with P. indica showed higher water stress tolerance while the water stress tolerant varieties Ptb 29 and Ptb 30 showed tolerance to water stress even in the absence of P. indica. Shoot length, shoot and root dry weight, number of root branches, SVI 1 and SVI 2 increased in P. indica-colonised plants than non-colonised plants under water stressed condition, while the root length decreased. Based on the observations on different parameters, Ptb 29 was considered as the best water stress tolerant variety and as Ptb 23 performed better than Ptb 24 under water stress condition, the former was selected as the best water-stress susceptible variety. The P. indica-colonised and non-colonised rice seedlings of Ptb 23 and Ptb 29 were the evaluated for water stress tolerance during the different growth stages by studying the morphological, physiological, biochemical, yield parameters and molecular aspects. P. indica-colonised plants under water stress exhibited higher shoot and root length, shoot and root dry weight, root-shoot ratio and root volume, however, it was more conspicuous in the water stress susceptible variety. The enhanced plant shoot-root growth and biomass production as well as other changes in plant morphology after P. indica-colonisation can be related to the plant response to increase auxin level in roots either produced by the fungus or by the plant due to stimulation by the endophyte. Relative water content was found to be higher in water stressed P. indica-colonised plants in both Ptb 23 and Ptb 29, although the effect of colonisation was more visible in Ptb 23. There was significant increase in the specific leaf area in P. indica-colonised plants of both varieties than non-colonised plants. In the current study, rice plants of Ptb 29 under water stressed condition had higher cell membrane stability index than Ptb 23. Plants in the presence of P. indica showed significantly reduced MDA content which indicates that P. indica lowers the adverse consequences of drought. Ptb 29 had lower MDA content than Ptb 23, which further established that Ptb 29 is more tolerant to water stress. Gas exchange parameters like stomatal conductance, transpiration rate and photosynthetic rate showed increase in P. indica-colonised plants than in non-colonsed plants. Retention of chlorophyll was significantly higher in water stressed plants of Ptb 29 than Ptb 23. The increased activity of antioxidant enzymes such as superoxide dismutase and catalase in P. indica-colonised plants during stressed condition reduced ROS levels in cells and thereby minimizing or preventing damage to cellular components. P. indica-colonised plants showed a reduced invertase activity than non-colonised plants. P. indica-colonisation improved the number of tillers, productive tillers as well the panicle length in plants under water stressed condition. The spikelet sterility was higher in non-colonised and water stressed plants. P. indica-colonisation contributed to a considerable increase in grain weight in Ptb 23. All these factors contributed to the final yield of the plant and unsurprisingly, P. indica-colonised plant sets produced more yield than non-colonised plant sets under water stressed conditions. Even though Ptb 29 produced more yield., P. indica-colonisation was more noticeable and effective in the water stress susceptible variety- Ptb 23. Keeping in view of our results, it can be emphasised that P. indica can mitigate the ill effects of water stress. The findings obtained from this study can be used as a foundation for future lines of research related to rational improvement of rice plants against water stress using endophytes.
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    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 R
    The 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.