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Open Access
Differential and dynamic response of rice variety uma under varying drought stress regimes
(Department of Plant Physiology, College of Agriculture, Vellanikkara, 2021) Akshaya Ramakrishnan; KAU; Parvathi M Sreekumar
Rice has the evolutionary advantage of being semi-aquatic, making it one of the world's most important crops. As a result, it has fewer water-scarcity responses and is especially vulnerable to drought stress. Climate change has put rice production in jeopardy today. According to recent studies, rice yield decreases as result of climate change such that when drought frequency and rainfall pattern changes, rice output is lowered. Rice is the principal staple grain grown in Kerala, with around 600 types used across the state's paddy fields. Uma (MO 16), developed by Kerala Agricultural University's Rice Research Station, Moncompu, is one of the most popular rice varieties in Kerala, which is currently planted in more than 60% rice growing areas in the state. It also has adaptability towards wide range of environmental conditions as well, even though environmental variations limit the potential yield of variety Uma. In this context, the present study on differential and dynamic response of variety Uma under drought stress at vegetative stage and its impact on stress responses of progeny, were attempted with the main objective of identifying potential drought stress specific biomarkers representing a trend in metabolite dynamics across generations. This approach was aimed to demonstrate in a simple way that a natural drought stress exposure can influence stress responses of rice variety, Uma in the present as well as future generations, with an aim of identification and selection of potential traits for inclusion in crop improvement programmes. The study was carried out at the Department of Plant Physiology, College of Agriculture, Vellanikkara, Thrissur as two experiments- a drought stress imposition study in the net house facility and a laboratory study in the next generation. As part of the first experiment, drought stress (60% field capacity; FC) was imposed to rice variety, Uma at vegetative stage by gravimetric approach, simultaneously maintaining a nonstressed control at 100% FC by regular watering. The experiment was laid out in completely randomized design in customized rain-out shelter like structures in the net house. Physiological parameterswere assessed immediately after stress exposure for assessment of stress damage and it was noted that there was a significant reduction in chlorophyll content (36.2%), membrane thermostability (78.5%) and relative water content (23.5%) under stress in comparison to non-stressed control tissues, ensuring effective stress exposure. Biochemical markers such as proline and malondialdehyde (MDA) estimated immediately after stress and after recovery across different phenophases, revealed a differential pattern in their regulation. The levels of both the biomarkers were significantly higher (14% and 70.7% respectively) under stress which dropped drastically at panicle initiation stage, followed by an increase in the grain filling stage. However, it was interesting to note that correspondingly both the biomarker metabolites exhibited lesser accumulation (95.1% and 25.2% respectively) in comparison to the non-stressed control plants in grain filling stage. The differential dynamics of proline as well as MDA over different phenophases when related to the protein levels estimated at panicle initiation stage, revealed that there was no concomitant recovery in protein levels even after stress recovery. The non-stressed control and stressed plants were raised to maturity and harvested seeds were used for the second experiment for assessing the stress memory response in the next generation. Yield attributes assessed also showed significant difference between the stressed and non-stressed plants. The second experiment to assess the stress memory response aimed at comparative stress response assessment under salinity as well as osmotic stresses at seedling stage in the next generation. In this context, a standardization experiment was carried out using different concentrations of NaCl and polyethylene glycol (PEG 6000) to impose salinity and osmotic stresses respectively, to uniformly germinated seedlings of rice variety, Uma, to ascertain sub-lethal stress levels. From the standardization experiment, sub-lethal levels of salt (100 mM NaCl) and osmotic (-4 bar) stresses were arrived at based on the percent reduction in growth over control. The progenies of the first experiment along with a lot of fresh seeds were exposed to stress using the standardized doses of salt as well as osmotic stresses. Priorto stress exposure, germination speed and the vigour index of the seedlings were estimated, which led to the discovery of two classes of stress exposed plants of first experiment with their seeds differing in vigour viz. moderate and high vigour. Four classes of seed materials- control and stressed (high and moderate vigour) seed sets from first generation and a fresh set of seeds of rice variety, Uma were used for the stress response experiment using the sub-lethal stress levels ascertained. The high vigour seedlings from the stressed plants showed better growth under salt stress compared to control set of seedlings from first generation as evidenced by lesser percent reduction in growth as well as recovery responses. Subsequently, biochemical marker MDA was estimated in the different treatments revealing that moderate as well as high vigour seedlings of the stress class accumulated lesser (64.5% and 18.6% respectively) MDA levels in comparison to the non-stressed control, with a consistent pattern under salinity stress. GC-MS/MS analysis was performed using shoot tissues of the seedlings across the different treatments, with an attempt to unravel any possible stress responsemechanism. GC spectra displayed a number of highly abundant as well as uniquely present compounds in the plants. Diphenyl sulfone, a potent sulfone derivative with antioxidant activity was differentially detected in all classes of plant materials used for the stress response study. There were corroborative inferences from the fold changes in diphenyl sulfone as well as the MDA contents, wherein there were proportional variations in the two especially in NaCl induced salinity stress in all treatments, indicating its probable role in maintaining lower MDA levels in the progenies of plants that were subjected to a prior drought stress exposure in the previous generation. A round of stress exposure at vegetative stage in rice variety, Uma influenced several morpho-physiological and biochemical parameters at different stages of the crop. There was an indication of the transmission of stress induced signal even in the next generation as evidenced by profuse growth and lower MDA contents under different stresses at seedling stage. It will be rewarding to observe the stress response/acclimation behaviour of Uma, under different abiotic stress exposure regimes across different phenophases.
Open Access
Elucidation of antioxidant fractions in leaves of Dendrophthoe falcata L. and standardisation of tape method of control
(Department of Plant Physiology, College of Agriculture, Vellanikkara, 2021) Aswathi Gopal; KAU; Parvathi M Sreekumar
Dendrophthoe falcata is a partial stem parasite belonging to Loranthaceae family, which is considered as a destructive pest of many economically important fruit trees such as mango, sapota, sugar apple and guava. They cause damage to the host plants by depleting nutrients, releasing toxins, and limiting their growth. Though several management strategies have been suggested by previous researchers which include pruning of its branches, base banding using 2,4-D and spray of ethrel in combination with organosilicone (non-ionic surfactant), the latter gave a promising response in comparison to others without affecting the host. Because of its destructive nature, some of the potential pharmaceutical features of the parasite often go unnoticed; if prospectively exploited it will automatically open up avenues for targeted removal of the parasitizing aerial parts of D. falcata. Plants are thought to be one of the most important sources for discovering and developing pharmaceuticals that are both effective and safe compared to currently available synthetic drugs. Traditional and folk medicines are gaining favour over contemporary therapy due to fewer side effects and a higher safety margin. Dendrophthoe falcata, a widely distributed plant in India, is one of nature's many plants with medicinal characteristics. The potential medicinal property of Loranthus has been reported in Ayurveda. It is reported to have diuretic, wound healing, anti-microbial, anti-helminthic, anti-fertility, antioxidant, anti-cancer, anti-diabetic, anti- hyperlipidemic and anti-hypersensitive activities. Medicinal properties of mistletoes are host specific. The antioxidant property of these parasitic plants might be due to their phenolic compounds including tannins and flavonoids. However, it will be very interesting to identify the novel antioxidant principles in the context of specific host associations. The present study was envisaged with a major aim of characterisation and elucidation of bioactive antioxidants from D. falcata leaves by invitro assays and identification of bioactive compounds through GC-MS/MS with prospective pharmaceutical applications, and standardization of efficient and non-regenerative method to control Loranthus.The experiments were carried out in Department of Plant Physiology, College of Agriculture, Vellanikkara, Thrissur. In the first experiment the leaf samples of Dendrophthoe falcata inhabiting different hosts namely mango, jackfruit, cocoa and sapota were collected, powdered and extracted in various organic solvents such as chloroform, petroleum ether, ethyl acetate, methanol and water followed by computation of extract yields. Aqueous extracts of D. falcata inhabiting all the hosts showed significantly higher (10.2 to 14.8%) yields compared to other solvents. Extract yield in case of petroleum ether and ethyl acetate were reported to be lowest (1.6 to 2.9% respectively) compared to other solvents indicating polar inorganic extraction to be advantageous, although novel and unique bioactive compounds could be effectively extracted in the latter. D(Sapota) showed lowest extract yield in petroleum ether (1.6%) and ethyl acetate (1.7%), whereas D(Jack) and D(Cocoa) had higher extract yields of 14.8% and 14.4% in water respectively. Free radical inhibition activity of D. falcata were assessed using DPPH radical scavenging assay in different hosts across various solvent extractions at different time intervals. Chloroform and water extracts of D. falcata showed an increasing trend in inhibition activity with time. However, ethyl acetate extracts marked a reduction in inhibition activity after two hours of incubation. Qualitative phytochemical screening of different extracts of D. falcata on the four hosts namely mango, jackfruit, cocoa and sapota were carried out to detect the presence of alkaloids, phenols, saponins, flavonoids, terpenes, tannins and steroids. There was a differential display of possession of different classes of phytochemicals by D. falcata across different host associations which varied with the nature of solvent used for extracting the antioxidant fractions. Chloroform extract of all the four hosts infested with D. falcata contained alkaloids, phenols, flavonoids, terpenes and steroids. Ethyl acetate extract had comparatively lesser phytochemicals, whereas methanolic extract had alkaloids, saponins, phenols, flavonoids, terpenes and steroids. Water extract yielded tannins along with other phytochemicals. Based on the antioxidant potential of the different extracts and host specificities, eight samples were shortlisted for GC- MS/MS analysis. Bioactive substances were detected in different extracts of D. falcata during GC-MS/MS analysis. Two common and abundant bioactive principles viz. cis- vaccenic acid and n-hexadecanoic acid were extracted in higher abundance in the petroleum ether extracts of D(sapota) and D(jack) for the former and D(jack) for thelatter. Petroleum ether extraction resulted in the best profiling for both the bioactive compounds from D(jack), indicating the association of D. falcata with jack as the most potential one to be tapped for pharmacological uses. The second experiment was carried out at Cocoa farm of Cocoa Research Centre, Kerala Agricultural University, Thrissur where the cocoa trees infested with Loranthus were tested for efficient management by impregnating the super absorbent polymer, super absorbent cotton and super absorbent paper with a combination of Ethrel and surfactants like oraganosilicone (OS)/alcohol ethoxylate (AE) @ 25mL/L of Ethrel + 0.5 mL/ L OS/AE and developed as a tape. Fresh and 1 week dried tapes were comparatively assessed, of which fresh application performed better than dried. The rate of defoliation also increased with time and after a while the number of leaves defoliated remained constant. Among the applicant material used, super absorbent polymer was found to be superior to super absorbent cotton and paper. Percent defoliation due to both surfactants revealed that AE performed better than OS. Ethrel along with surfactant alcohol ethoxylate (AE) as a sticky tape using superabsorbent polymer as the impregnating material can be used as an effective management strategy as AE is more eco-friendly than organosilicone. The tape method can also be an alternative to spraying even in the event its longer time for defoliation, provided if it ensures similar regrowth restriction efficiencies.
Open Access
Microencapsulation of Trichoderma viride for management of major soil borne fungal pathogens
(Department of Plant Physiology, College of Agriculture, Vellanikkara, 2020) Saleena, M; KAU; Reshmy, Vijayaraghavan
Trichoderma spp, one of the widely exploited biocontrol agents in the arena of crop disease management, are known for promoting growth and inducing abiotic stress tolerance in plants. However, direct application in the field limits their efficiency due to several adverse factors. Hence, they should be adequately formulated to escalate the efficacy in field application. Eventhough, a number of such formulations have been developed in the recent past, many of them are bulky in nature, having reduced shelf life with a high risk of contamination and desiccation. Thus, a study was conducted to develop a novel formulation of T. viride, with sodium alginate, a biodegradable polymer as the encapsulating carrier material. Evaluation of the effect of additive substances viz., mannitol (2%), trehalose (15 mM), polyvinyl pyrrolidone (1%), polyethylene glycol (0.25%), carboxymethyl cellulose (0.5%), liquid paraffin (1%) and tween 80 (0.5%) in eight combination on the shelf life of T. viride was carried out. After seven months of evaluation, a combination of trehalose, PVP, CMC and tween 80 outperformed the other treatments. Beads were prepared using 0.75, 1.5, 2.5, 3.0 and 3.5 per cent sodium alginate and 2.5, 3.0 and 3.5 per cent CaCl2 solution with and without additives. Without additives, no beads were formed at 0.75 and 1.5 per cent sodium alginate and spherical beads were formed at 2.5, 3.0 and 3.5 per cent. When additives were amalgamated, 0.75 and 1.5 per cent sodium alginate yielded spherical beads, while beads were not formed at 2.5, 3.0 and 3.5 per cent. Hence, the concentration of sodium alginate was standardized as 0.75 and 1.5 per cent. The impact of height of air column between the orifice of the separating funnel and the level of CaCl2 bath on the bead shape was evaluated at different heights where 2 and 4 cm yielded tailed beads while, rest of the heights yielded spherical beads. Hence, based on the shape of the bead, 8 - 12 cm was selected as the optimum height of air column. Previously standardized parameters along with 2.5, 3.0 and 3.5 per cent CaCl2 solution was adopted to prepare beads by employing ionotropic gelation and cross linking technique in 31 treatments. The beads were dried for 48 h at room temperature and stored in air tight containers. vii Properties like bead weight, diameter, yield and number of beads formed per ml sodium alginate solution was estimated. A maximum bead weight of 96.20 ± 1.8 mg and bead diameter of 2.42 ± 0.13 mm was recorded in control (T31-sodium alginate 2.5% and CaCl2 2.5%). Maximum per cent yield was documented in T19 (trehalose, PVP, CMC, tween 80, sodium alginate 1.5%, CaCl 2 2.5%) (69.09%) and a maximum of 26.91 beads were formed from each ml of sodium alginate in T9 while, it was 8.0 in control. Shelf life evaluation was carried out for six months, where T21 (trehalose, PVP, CMC, tween 80, sodium alginate 1.5%, CaCl2 3.5%) outperformed the other treatments even after six months hence, T21 was selected as the best treatment. Degree of contamination was estimated at 1, 3 and 6 months after preparation, where T1 - T6 and T19 - T30 remained free of contamination even after six months of preparation. Per cent of potentially infective beads were estimated where cent per cent germination was recorded at 72 h after incubation. Moisture content of the beads were assessed where the beads retained its intact shape at 48 h and therefore was selected as the optimum period of drying. Swelling behaviour of microbeads were estimated at pH 7.4 in phosphate buffer and at pH 1.0 in 0.1M HCl. A gradual increase in weight of beads at pH 7.4 confirmed the swelling behaviour while, reduction in weight at pH 1.0 revealed its shrinking nature. Time of gelation was standardized as 60 min as the bead weight declined until this time and attained stability after this time. The effect of pH on the selected bead (T21) was evaluated at pH 5.09 and 8.91 in soil under in vitro conditions where the release in former was sustained while a sudden release was observed in latter. Observations on biometric parameters, yield and the per cent disease incidence from pot culture experiments revealed that sodium alginate bead based formulation @ 5.0 g plant-1 performed superior to talc based and liquid formulations. The study on degradation revealed that the beads were biodegradable in nature. Thus, the present investigation succeeded in formulating T. viride using sodium alginate as the encapsulating carrier material, which would help to compensate the drawbacks associated with presently available formulations. However, the study should be complimented with multilocational trials to confirm its efficacy under field conditions.
Open Access
Physiological intervention for mitigating temperature stress in rice
(Department of Plant Physiology, College of Horticulture , Kerala Agricultural University, Vellanikkara, 2020) Femina, K; KAU; Girija, T
Rice is an important cereal crop which is most widely consumed as staple food by millions of people. Demand for rice is projected to increase across globe with rapid increase in population. Rice being a tropical crop requires a fairly high temperature for optimum growth and development. However, temperatures above 35 0C cause heat injuries in rice including changes in morphological, physiological and yield characters. Hence, the present study was conducted to identify ameliorative chemicals to mitigate high temperature stress, which is a common occurrence in the third crop season where temperatures can go up to 40 0C in the reproductive stage leading to yield loss. Popular rice varieties, Uma and Manuratna, which are also suitable for the third crop season were chosen for the study. The whole study was divided in to two experiments. The first experiment was carried out in glass house at College of Horticulture, Vellanikkara during January to May, 2019. Ten day old rice seedlings of Uma (V1) and Manuratna (V2) were planted in pots. Treatments included five ameliorative sprays viz. Ascorbic acid (T1), Glutathione (T2), Melatonin (T3), Salicylic acid (T4) and Hoagland solution (T5) along with Water sprayed (T6) and Unsprayed (T7) controls. Ameliorants were sprayed at active tillering stage (S1), booting stage (S2) and both active tillering and booting stages (S3). Physiological responses were studied from this experiment. Pot culture study showed that ameliorants could improve physiological characters of rice under increasing temperature. Hoagland solution spray enhanced photosynthetic rate, stomatal conductance, IAA content and pollen viability in both the varieties. Increased total soluble protein content, chlorophyll a, chlorophyll b and total chlorophyll was noted in plants sprayed with melatonin. Proline accumulation increased in plants sprayed with glutathione while nitrate reductase enzyme activity improved by salicylic acid. Reduced amount of reactive oxygen species as evidenced by histochemical studies was observed in plants sprayed with ameliorants having antioxidant property, like melatonin, glutathione and ascorbic acid. Spraying of ameliorants at both active tillering and booting stages (S3) was the best followed by spraying at booting stage (S2) alone. Second experiment was carried out in Agronomy farm at College of Horticulture, Vellanikkara during February to June, 2020. Twenty day old seedlings of Uma and Manuratna were transplanted to micro plots of 4 m2. Ameliorants were given as foliar spray at booting stage and one plot of each variety was maintained as control for comparison. Biometric observations and yield characters were studied from this trial. Hoagland solution and salicylic acid treatments increased plant height, RGR and CGR in both the varieties. Reduced tiller decline was also observed in Hoagland solution treated plants. Uma showed higher response to ameliorants than Manuratna. Yield parameters were analyzed by comparing response of ameliorants with control. Plants sprayed with Hoagland solution showed better performance with higher grain yield. It was due to increased number of productive tillers, spikelets per panicle, filled grains per panicle and thousand grain weight. Chaff percentage decreased by application of ameliorants and among them Hoagland solution spray gave the best result. Salicylic acid applied plants had higher straw yield compared to other treatments. Yield performance was better in Uma compared to Manuratna.
Open Access
Drought mitigation in Okra (Abelmoschus esculentus L.) through chemical approach
(Department of Plant Physiology, College of Agriculture, Padannakkad, 2021) Fathimath, Suhaila; KAU; Sudarshana Rao, G V
Okra or Bhindi (Abelmoschus esculentus L.) is one of the most popular summer vegetable crop grown widely in Kerala for its edible green fruits. Drought is a major yield limiting factor in agriculture and vegetables are more sensitive to drought stress as compared to most of the field crops because of their high water requirement. Hence, the study entitled “Drought mitigation in okra (Abelmoschus esculentus L.) through chemical approach” was carried out with the objective to investigate the influence of different chemicals namely, salicylic acid, ascorbic acid and thiourea on mitigation of drought and to evaluate their effect on morphological, physiological and yield charcteristics of okra. The field experiment was laid out in randomized block design with 8 treatments and 3 replications at RARS, Pilicode during December 2019 to March 2020. The okra variety Arka Anamika was raised as per standard package of practices recommendations of Kerala Agricultural University and also under soil test based nutrient management system. The experiment consisted of 8 treatments viz., normal irrigation (T 1 ) as control, drought stress (T 2 ), T 2 + salicylic acid foliar spray @ 1 mM (T 3 ), T 2 + salicylic acid foliar spray @ 2 mM (T 4 ), T 2 + ascorbic acid foliar spray @ 1 mM (T 4 ), T 2 + ascorbic acid foliar spray @ 2 mM (T 5 ), T 2 + thiourea foliar spray @ 500 ppm (T7), T 2 + thiourea foliar spray @ 1000 ppm (T8). Foliar application of chemicals were given at 10, 20 and 30 DAS and stress was induced by withholding irrigation from 25 days of sowing and re-irrigation was given at 50 per cent field capacity. Morphological, physiological and biochemical parameters were recorded at 25, 50 and 75 DAS and the yield and fruit quality characters were recorded at the time of harvest. A perusal of morphological data showed that T 3 had maximum plant height, number of leaves plant -1 , number of pickings and highest duration of the crop followedby T 6 when compared to all other treatments. The maximum number of branches per plant and the highest root volume were recorded in T 1 which was on par with T 3 followed by T 6 . Foliar spray of chemicals did not significantly influence number of days for 50 per cent flowering and first harvest. Up to 75 DAS, maximum relative growth rate was observed T 3 . All the treatments performed better than drought stress treated crops. At all the growth stages, maximum specific leaf weight was exhibited T 3 . Leaf area was observed maximum for T 3 and was on par with T 4 , T 5 , T 6 at 25 DAS and T 1 , T 4 and T 6 at 50 DAS and T 6 at 75 DAS. The relative leaf water content was recorded the highest for T 3 at 25 DAS and for T 1 at 50 and 75 DAS. At 50 DAS, T 1 was on par with T 3 , T 6 and T 7 and at 75 DAS T 1 was followed by T 3 and T 6 . T 3 had maximum total dry matter production which was on par with T 1 and T 4 .at 25 and 50 DAS, respectively. Root shoot ratio was recorded maximum in T 3 which was on par with T 1 at 25 and 50 DAS. SPAD chlorophyll meter reading (SCMR) was recorded maximum in T 3 at 25 and 50 DAS and in T 1 at 75 DAS. T 1 was on par with T 3 , T 4 and T 6 at 75 DAS. Considering the yield and fruit quality attributes, T 4 recorded maximum value for fruit length and was on par with T 1 , T 7 and T 8 . The highest average fruit girth and fruit weight were exhibited in T 3 and lowest was in drought stressed crop (T 2 ). The treatment T 1 , T 3 , T 4 and T 6 recorded maximum number of fruits plant -1 which were on par with T 5 and T 7 . The highest total fruit yield was recorded in foliar spray of salicylic acid (1 mM) followed by ascorbic acid (2 mM). These treatments recorded 45 per cent and 41 per cent higher yield over drought stressed treatment, respectively. The crude fibre content was recorded highest for drought stressed crops (T 1 ) and the lowest was recorded in T 3 . The ascorbic acid content was observed maximum in T 1 followed by T 5 and T 6 . The highest net returns and BCR was obtained in T 3 followed by T 6 . The frequency of irrigation given was highest in T 1 followed by T 2 and T 8 . The lowest frequency of irrigation given were in T 3 , T 6 and T 7 . The irrigation interval was more with T 3 , T 6 and T 7 (5 days).It can be concluded that morphological, physiological, biochemical and yield traits of okra were severely affected under drought stress. Among the three drought mitigating chemicals, salicylic acid (1 mM) recorded maximum values for morphological traits viz., plant height, number of leaves plant -1 , root volume and duration of crop, followed by ascorbic acid (2 mM), which also significantly improved morphological traits of okra compared to all other treatments. Physiological traits such as total dry matter production, leaf area plant -1 , relative growth rate, specific leaf weight, root shoot ratio and SPAD chlorophyll meter reading increased over drought stress crop when sprayed with salicylic acid (1 mM) and ascorbic acid (2 mM). Salicylic acid (1 mM) and ascorbic acid (2 mM) is beneficial for getting higher fruit yield and maximum economic returns over drought stressed and normal irrigated crops. Therefore, application of salicylic acid (1 mM) and ascorbic acid (2 mM) significantly mitigated the harmful effect of drought stress in okra.
Open Access
Microencapsulation of Trichoderma viride for management of major soil borne fungal pathogens
(Department of Plant Physiology, College of Agriculture, Vellanikkara, 2020) Saleena, M; KAU; Reshmy, Vijayaraghavan
Trichoderma spp, one of the widely exploited biocontrol agents in the arena of crop disease management, are known for promoting growth and inducing abiotic stress tolerance in plants. However, direct application in the field limits their efficiency due to several adverse factors. Hence, they should be adequately formulated to escalate the efficacy in field application. Eventhough, a number of such formulations have been developed in the recent past, many of them are bulky in nature, having reduced shelf life with a high risk of contamination and desiccation. Thus, a study was conducted to develop a novel formulation of T. viride, with sodium alginate, a biodegradable polymer as the encapsulating carrier material. Evaluation of the effect of additive substances viz., mannitol (2%), trehalose (15 mM), polyvinyl pyrrolidone (1%), polyethylene glycol (0.25%), carboxymethyl cellulose (0.5%), liquid paraffin (1%) and tween 80 (0.5%) in eight combination on the shelf life of T. viride was carried out. After seven months of evaluation, a combination of trehalose, PVP, CMC and tween 80 outperformed the other treatments. Beads were prepared using 0.75, 1.5, 2.5, 3.0 and 3.5 per cent sodium alginate and 2.5, 3.0 and 3.5 per cent CaCl2 solution with and without additives. Without additives, no beads were formed at 0.75 and 1.5 per cent sodium alginate and spherical beads were formed at 2.5, 3.0 and 3.5 per cent. When additives were amalgamated, 0.75 and 1.5 per cent sodium alginate yielded spherical beads, while beads were not formed at 2.5, 3.0 and 3.5 per cent. Hence, the concentration of sodium alginate was standardized as 0.75 and 1.5 per cent. The impact of height of air column between the orifice of the separating funnel and the level of CaCl2 bath on the bead shape was evaluated at different heights where 2 and 4 cm yielded tailed beads while, rest of the heights yielded spherical beads. Hence, based on the shape of the bead, 8 - 12 cm was selected as the optimum height of air column. Previously standardized parameters along with 2.5, 3.0 and 3.5 per cent CaCl2 solution was adopted to prepare beads by employing ionotropic gelation and cross linking technique in 31 treatments. The beads were dried for 48 h at room temperature and stored in air tight containers. vii Properties like bead weight, diameter, yield and number of beads formed per ml sodium alginate solution was estimated. A maximum bead weight of 96.20 ± 1.8 mg and bead diameter of 2.42 ± 0.13 mm was recorded in control (T31-sodium alginate 2.5% and CaCl2 2.5%). Maximum per cent yield was documented in T19 (trehalose, PVP, CMC, tween 80, sodium alginate 1.5%, CaCl 2 2.5%) (69.09%) and a maximum of 26.91 beads were formed from each ml of sodium alginate in T9 while, it was 8.0 in control. Shelf life evaluation was carried out for six months, where T21 (trehalose, PVP, CMC, tween 80, sodium alginate 1.5%, CaCl2 3.5%) outperformed the other treatments even after six months hence, T21 was selected as the best treatment. Degree of contamination was estimated at 1, 3 and 6 months after preparation, where T1 - T6 and T19 - T30 remained free of contamination even after six months of preparation. Per cent of potentially infective beads were estimated where cent per cent germination was recorded at 72 h after incubation. Moisture content of the beads were assessed where the beads retained its intact shape at 48 h and therefore was selected as the optimum period of drying. Swelling behaviour of microbeads were estimated at pH 7.4 in phosphate buffer and at pH 1.0 in 0.1M HCl. A gradual increase in weight of beads at pH 7.4 confirmed the swelling behaviour while, reduction in weight at pH 1.0 revealed its shrinking nature. Time of gelation was standardized as 60 min as the bead weight declined until this time and attained stability after this time. The effect of pH on the selected bead (T21) was evaluated at pH 5.09 and 8.91 in soil under in vitro conditions where the release in former was sustained while a sudden release was observed in latter. Observations on biometric parameters, yield and the per cent disease incidence from pot culture experiments revealed that sodium alginate bead based formulation @ 5.0 g plant-1 performed superior to talc based and liquid formulations. The study on degradation revealed that the beads were biodegradable in nature. Thus, the present investigation succeeded in formulating T. viride using sodium alginate as the encapsulating carrier material, which would help to compensate the drawbacks associated with presently available formulations. However, the study should be complimented with multilocational trials to confirm its efficacy under field conditions.
Open Access
Physiological intervention for mitigating temperature stress in rice
(Department of Plant Physiology, College of Horticulture , Kerala Agricultural University, Vellanikkara, 2020) Femina, K; KAU; Girija, T
Rice is an important cereal crop which is most widely consumed as staple food by millions of people. Demand for rice is projected to increase across globe with rapid increase in population. Rice being a tropical crop requires a fairly high temperature for optimum growth and development. However, temperatures above 35 0C cause heat injuries in rice including changes in morphological, physiological and yield characters. Hence, the present study was conducted to identify ameliorative chemicals to mitigate high temperature stress, which is a common occurrence in the third crop season where temperatures can go up to 40 0C in the reproductive stage leading to yield loss. Popular rice varieties, Uma and Manuratna, which are also suitable for the third crop season were chosen for the study. The whole study was divided in to two experiments. The first experiment was carried out in glass house at College of Horticulture, Vellanikkara during January to May, 2019. Ten day old rice seedlings of Uma (V1) and Manuratna (V2) were planted in pots. Treatments included five ameliorative sprays viz. Ascorbic acid (T1), Glutathione (T2), Melatonin (T3), Salicylic acid (T4) and Hoagland solution (T5) along with Water sprayed (T6) and Unsprayed (T7) controls. Ameliorants were sprayed at active tillering stage (S1), booting stage (S2) and both active tillering and booting stages (S3). Physiological responses were studied from this experiment. Pot culture study showed that ameliorants could improve physiological characters of rice under increasing temperature. Hoagland solution spray enhanced photosynthetic rate, stomatal conductance, IAA content and pollen viability in both the varieties. Increased total soluble protein content, chlorophyll a, chlorophyll b and total chlorophyll was noted in plants sprayed with melatonin. Proline accumulation increased in plants sprayed with glutathione while nitrate reductase enzyme activity improved by salicylic acid. Reduced amount of reactive oxygen species as evidenced by histochemical studies was observed in plants sprayed with ameliorants having antioxidant property, like melatonin, glutathione and ascorbic acid. Spraying of ameliorants at both active tillering and booting stages (S3) was the best followed by spraying at booting stage (S2) alone. Second experiment was carried out in Agronomy farm at College of Horticulture, Vellanikkara during February to June, 2020. Twenty day old seedlings of Uma and Manuratna were transplanted to micro plots of 4 m2. Ameliorants were given as foliar spray at booting stage and one plot of each variety was maintained as control for comparison. Biometric observations and yield characters were studied from this trial. Hoagland solution and salicylic acid treatments increased plant height, RGR and CGR in both the varieties. Reduced tiller decline was also observed in Hoagland solution treated plants. Uma showed higher response to ameliorants than Manuratna. Yield parameters were analyzed by comparing response of ameliorants with control. Plants sprayed with Hoagland solution showed better performance with higher grain yield. It was due to increased number of productive tillers, spikelets per panicle, filled grains per panicle and thousand grain weight. Chaff percentage decreased by application of ameliorants and among them Hoagland solution spray gave the best result. Salicylic acid applied plants had higher straw yield compared to other treatments. Yield performance was better in Uma compared to Manuratna.
Open Access
Spectral manipulation of growth and physiology of Gerbera jamesonii Bolus
(Department of Plant Physiology, College of Horticulture , Kerala Agricultural University, Vellanikkara, 2020) Anil, A S; KAU; Girija, T
Gerbera (African daisy) is one of the most important commercial flower grown throughout the world under a wide range of climatic conditions. Gerbera requires high light intensities for good vegetative growth and flower yield. The average sunshine hours in open condition in the central zone of Kerala during January to May goes upto 8.1 h/day while during June- September is only 3h/day as per 33 year mean data available with the Agro Meteorology Observatory COH, Vellanikkara. This shortage in the sun shine hours can be substituted by the use of external light in polyhouse. When light is provided at the optimal levels it can significantly increase growth rate, health and yield of the crop. The experiment was conducted during the period from July 2018 to September 2019 in polyhouses, at, College of Horticulture, Vellanikkara, to study the influence of spectral light intensities and UV on the morphological, phenological, physiological characters, yield and flower quality of Gerbera (Gerbera Jamesonii Bolus) Tissue culture plants of Gerbera variety Julia developed and marketed by LJ International (AVT Biotechnology) in two leaf stage were directly planted in pots of size 9-inch depth at the rate of one plant per pot. The pots were placed under LED lights of red, blue, green, white and yellow colours kept at a height of one meter from the ground. Plants were illuminated for 10 hours from 09.00 am to 07.00 pm daily from July 28th to September 25 th (2018 to 2019). Observations on morphological characters such as plant height, leaf length, leaf breadth, plant spread, number of lobes, specific leaf area and petiole length were significantly influenced by spectral colors and UV. Among the spectral color’s plants under red and blue showed significant higher morphological attributes compared to other colors. Also, plants under non-UV condition showed greater growth characters as compare to UV condition. Floral evocation was observed when the plants reached five leaf stage. Under red and blue light exposure, plants came to flower in September (49 days from planting) while plants in all other treatments started flowering in October (60 days from planting). Evaluation of photosynthetic rate under different color regimes indicated that maximum photosynthetic rate was under red light. Gas exchange parameters like stomatal conductance, transpiration rate and stomatal frequencies were higher under blue light followed by red light. Also, plants under non-UV condition showed better physiological characters as compare to those under UV condition. Estimation of GA, IAA and chlorophyll content revealed that all the three components were higher in red light followed by blue under non-UV condition. Nitrate reductase enzyme plays a major role in nitrogen metabolism of plants. In the present study, the nitrate reductase enzyme activity was found to be higher in plants grown under red light in non-UV condition. Flower pigments like anthocyanin, xanthophyll, flavonoids were found higher in plants grown under blue light and under UV condition rather than non-UV condition. These constituents are products of secondary metabolic pathway in plants. Flower number and flower quality parameters like number of flowers, flower head diameter, flower stalk length, flower stalk girth and vase life was better under non UV condition than UV condition. These quality characters were seen to be better in plants grown under red and blue light. The study indicated that UV stabilized sheets would be more beneficial than normal polythene sheets and red and blue LED’s can be used to supplement light requirement in polyhouses for commercial cultivation of Gerbera jamesoni Bolus
Open Access
Physiological and biochemical studies in cluster bean (Cyamopsis tetragonoloba (L.) Taub) as influenced by light and moisture stress
(Department Of Plant physiology, College Of Agriculture, Vellayani, 2020) Sreeraj; KAU; Viji, M M
The programme entitled “Physiological and biochemical studies in cluster bean [Cyamopsistetragonoloba(L.) Taub.] as influenced by light and moisture stress” was carried out at the Department of Plant Physiology, College of Agriculture, Vellayani, during 2019-2020. The objective of the programme was to study the light and moisture stress induced physiological and biochemical changes in cluster bean. A field study was carried out with the cluster bean variety ‘KAU Suruchi’ in Factorial Randomized Block Design (FRBD). It involved a combination of three levels of light stress (different shade levels) and three levels of moisture stress (different field capacity levels) which is inclusive of a control also, with four replications .The observations were taken at three different critical stages of the crop viz.vegetative stage, flowering stage and pod filling stage. Different shade levels were provided by using high-density polyethylene nets with differential light transmission to maintain 50 % and 25% shade and no shade net for open condition. Whereas for imposing moisture stress, three irrigation regimes based on gravimetric estimations were followed to maintain the field capacity levels of 100%, 75% and 50%.The treatment ( open condition + 100% field capacity) served as the control (T7) for the experiment. Different growth parameters such as plant height, number of primary branches per plant, root dry weight, shoot dry weight, root: shoot ratio, crop growth rate and relative growth rate were studied. It was found that only root dry weight and root: shoot ratio increased under combined light and moisture stress in comparison to control . However, plant height was found to increase under the treatments T1 (50% shade + 100% field capacity), T4 (25% shade + 100% field capacity), T5 (25% shade + 75% field capacity) and T6 (25% shade + 50% field capacity) compared to the control. The physiological parameters studied viz. transpiration rate and photosynthetic rate were found to decrease under the influence of both light and moisture stress conditions compared to the control. Among the biochemical parameters studied, total chlorophyll content was found to increase under the influence of both the stresses with the highest value (1.747 mg g-1, 1.947 mg g-1 and 2.141 mg g-1) across the three growth stages except that of treatment T9 (open + 50% field capacity).The chlorophyll ‘a’content was found to increase across all the treatments compared to the control. However chlorophyll ‘b’ content was found higher under shaded condition. But the chlorophyll a: b ratio was found to be higher only under open conditions. The total soluble protein content showed a decrease under the combined abiotic stresses. Overall it was observed that under the combined influence of light and moisture stress, physiological parameters such as plant height(T1,T4,T5 and T6), root weight and root: shoot ratio were up regulated whereas number of primary branches per plant, shoot weight, crop growth rate, relative growth rate, photosynthetic rate and transpiration rate were down regulated. As far as biochemical characters are concerned chlorophyll ‘a’, chlorophyll ‘b’ (T1 to T6), chlorophyll a: b ratio (T8 and T9) and total chlorophyll content (T1 to T8) improved, whereas the total soluble protein was found to decrease across all treatments compared to control. Considering the physiological, and biochemical characters, treatment T6 (25% shade + 50% field capacity) is favourable for the tolerance of cluster bean to the light and moisture stress, in view of the enhancement of plant height and chlorophyll content and the comparatively better performance than other stress combinations in comprehending the stress combination. However, the severest stress combination of treatment T3 (50% shade + 50% field capacity) enhanced the root: shoot ratio and lowered the transpiration rate the most, which is a positive aspect in terms of stress tolerance. In short, cluster bean is capable of tolerating light and moisture stress levels up to 50% shade and 50% field capacity respectively.

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