Browsing by Author "Susha, S Thara"

Now showing 1 - 4 of 4

Etiology, molecular characterization and management of viral disease of dendrobium
(Department of plant pathology , Vellayani, 2023-07-19) Safeer, M M.; Susha, S Thara
The present study on “Etiology, molecular characterization, and management of virus diseases of Dendrobium” was conducted at the Department of Plant Pathology, College of Agriculture, Vellayani during the period 2015-2019. The study included survey among different orchid growers in Kerala, etiology of disease, detection of viruses using immunological and molecular techniques and finally finding a management strategy for the diseases. A scoring technique was developed for scoring severity of Cymbidium mosaic virus (CymMV) and Odontoglossum ringspot virus (ORSV) and based on which a survey was conducted among different orchid importers and growers in five districts of Kerala. Among a total of 9500 plants surveyed, a minimum five percent virus disease incidence was recorded in all locations surveyed. The present investigation observed the presence of CymMV and ORSV in the imported and cultivated Dendrobium orchids in Kerala. The study also observed that integrating meristem culture followed by root inoculation of P. indica in combination with foliar application of antiviral compounds effectively controls CymMV in Dendrobium orchids. This management practice can be easily adopted by farmers and with ease and had a prolonged effect on Dendrobium orchids.
Mycoflora of black pepper in storage and their management
(Department of Plant Pathology, College of Agriculture,Vellayani, 2025-01-15) Jesna, N B.; Susha, S Thara
A study entitled ‘Mycoflora of black pepper in storage and their management’ was conducted during 2022-24 at the Department of Plant Pathology, College of Agriculture, Vellayani, with the objective of investigating the fungal contaminations of black pepper in storage and assessment of the quality deterioration and mycotoxin associated with the mycoflora; its management through ecofriendly methods. A survey was conducted during July to December 2023, for collecting the stored contaminated samples of the whole black pepper from pepper growers in 3 locations each from Thiruvananthapuram, Kozhikode, Idukki and Wayanad districts (Agro ecological units (AEU) 14, 15, 16 and 20) of Kerala for studying the mycoflora associated with the stored pepper. Weather data from the survey locations, including maximum and minimum temperatures, relative humidity and rainfall were recorded. Weather conditions prevailing in the area showed relation to the level of contamination. The symptoms of contamination in black pepper samples collected from different AEUs varied across locations. Symptoms observed were greenish and whitish fungal growth over the surface of the berries, shrivelled and hollow berries. Most of the collected samples were stored in sacks and higher level of mould infestation was noted in these samples. The contaminated berries had a storage period of more than 1 year. The moisture content of the samples range between 5.82% and 7.22%. The contaminants were isolated from the collected contaminated black pepper samples; out of 61 isolates 28 belonged to Genus Aspergillus. Morphological studies revealed that eleven were Aspergillus flavus, ten Aspergillus ochraceus, seven Aspergillus niger, seven Talaromyces pinophilus, six Penicillium spp., six Syncephalastrum spp., three Mucor spp., one Helminthosporium sp. and one Colletotrichum sp. Since the study primarily focused on major contaminant of black pepper samples, A. flavus the isolate having the wider occurrence was selected for further studies. The colony of A. flavus exhibited a yellowish green colour with white margin, had regular borders and a flat topography. Non-pigmented, unbranched uniseriate conidiophore bears subglobose/globose vesicle with ampulliform phialides having globose yellowish to olive conidia. Based on the cultural, morphological and molecular studies, major contaminant was confirmed as Aspergillus flavus (accession number PQ222594). The biochemical changes viz., phenol, protein, starch, piperine, moisture, total ash, essential oil and oleoresin in the collected black pepper samples were analyzed in comparison to the healthy black pepper samples. The phenol and moisture content were found to be increased on contamination while the protein, starch, piperine, total ash, essential oil and oleoresin were decreased. Among samples collected from Trivandrum, starch (20.62%), essential oil (0.32%) and oleoresin (8.03%) were found to be lowest in samples collected from Vithura, whereas piperine content (4.31%) was lowest in samples from Peringammala. Analysis of samples from Kozhikode revealed that protein (5.14 mg/g), starch (24.57%) and piperine (3.17%) content were lowest in samples from Kodenchery whereas oleoresin was lowest for samples from Narippatta. For the samples from Idukki, oleoresin (7.01%) and piperine (2.33%) was lowest for samples from Pampadumpara. The quality of the contaminated black pepper samples was reduced with faded black and dull black colour, hard, wrinkled and brittle texture, greenish, white and grey fungal growth. Mycotoxin levels in black pepper samples were analyzed using HPLC. Detectable level of aflatoxins (B1, B2, G1, G2) and ochratoxin were not present in the contaminated black pepper samples. In vitro evaluation of prepared essential oil nanoemulsions (NEs) viz., cinnamon oil NE, clove oil NE, basil oil NE, neem oil NE and thyme oil NE at 0.5%, 1% and 2% against A. flavus. The highest inhibition (100%) at the lowest concentration (0.5%) was observed in basil oil NE followed by 1% clove oil NE and cinnamon oil NE. Particle size analysis of essential oil NE were measured as 81.73 nm for cinnamon oil NE, 108.47 nm for clove oil NE and 32.33 nm for basil oil NE. The zeta potential values were -27.2 mV for basil oil NE, -37.5 mV for cinnamon oil NE and -34.6 mV for clove oil NE which indicated the stability of these nanoemulsions. Based on the results of in vitro evaluation, the best three treatments (0.5% basil oil NE, 1% clove oil NE and 1% cinnamon oil NE) were taken for in vivo studies along with uninoculated control. The treated black pepper berries were inoculated with a five day old culture of A. flavus and other contaminants. Berries treated with 0.5% basil oil NE showed no symptoms during storage (90 days). A fine layer of greenish fungal growth on the surface of the berries were observed in berries treated with 1% clove oil NE (78th day) and 1% cinnamon oil NE (70th day). While the berries inoculated with all contaminants and left untreated showed white and grey fungal growth by 18th day. The present study revealed that the major contaminant associated with black pepper in storage is Aspergillus flavus. The postharvest coating of dried black pepper berries with 0.5% basil oil nanoemulsion is proved to be an effective novel strategy for the management of Aspergillus flavus and all other contaminants during storage without causing any quality deterioration.
Silver nanoparticles green synthesized using leaf extract of Piper colubrinum for the management of foot rot in black pepper (Piper nigrum L.)
(Department of Plant Pathology, College of Agriculture, Vellayani, 2024-12-21) Susha, S Thara; Susha, S Thara
The study entitled “Silver nanoparticles green synthesized using leaf extract of Piper colubrinum for the management of foot rot in black pepper (Piper nigrum L.)” was conducted at Department of Plant Pathology, College of Agriculture, Vellayani during 2022-2024 with the objectives to green synthesize silver nanoparticles with leaf extract of foot rot resistant Piper colubrinum, their characterization, test its efficacy in managing foot rot in black pepper (Piper nigrum L.) caused by Phytophthora capsici and estimation of defense related enzymes. Piper colubrinum and Piper nigrum leaf extract were used to synthesis silver nanoparticles (AgNPs), which were then physically characterized and tested for their antagonistic effect against P. capsici. Formation of silver nanoparticles was confirmed by colour change of the solution to dark brown after one hr incubation and by characterisation techniques. The green synthesized silver nanoparticles (GSAgNPs) using P. nigrum leaf extract (Pn-AgNPs) exhibited an absorbance maximum at 440 nm and GSAgNPs using P. colubrinum leaf extract (Pc-AgNPs) exhibited an absorbance maximum at 460 nm in UV Visible spectroscopy. The sharp peaks obtained in XRD analysis indicated the crystalline structure of the silver nanoparticles and the positions of the peaks suggest the presence of face-centered cubic (FCC) structures in both Pn-AgNPs and Pc-AgNPs. FTIR results revealed that more functional groups are present in Pn-AgNPs than Pc-AgNPs. FE-SEM showed the average size of Pn-AgNPs was 57 nm and that of Pc- AgNPs was 56 nm. The spherical morphology of Pn- AgNPs and Pc- AgNPs were revealed by HR-TEM images. Black pepper leaves with the foot rot symptoms of dark brown lesions with a fimbriate margin were selected for the isolation of the pathogen. The isolated colonies appeared as white to off white in stellate pattern on PDA medium. Mycelia were coenocytic with an average width of 3-8 μm. Lemon shaped papillate sporangia of the fungus with an average length 32-51 μm were observed microscopically. Molecular identification of the pathogen confirmed it as Phytophthora capsici and accession number of the culture is PP09178. The efficacy of Pn-AgNPs and Pc-AgNPs at different concentrations in inhibiting the growth of P. capsici was tested under in vitro conditions by poisoned food technique. Among treatments, commercial AgNPs, commercial chitosan nanoparticles (ChNPs), P. nigrum and P. colubrinum leaf extracts (5%) and copper oxychloride (0.2%), were also included. Highest in vitro mycelial growth inhibition (76.67 %) of the pathogen was observed with 750 ppm Pn-AgNPs followed by 750 ppm of Pc-AgNPs (73.33%). The better antifungal activity of Pn-AgNPs can be due to the type of phytochemicals present in P. nigrum leaf extract, which could provide better capping and stabilization of the silver nanoparticles. Copper oxychloride inhibited the mycelial growth completely. In detached leaf assay with black pepper variety Panniyur-1, lesion development was significantly reduced on leaves treated with the GSAgNPs (500 ppm and 750 ppm) compared to those treated with commercial AgNPs and ChNPs of the same concentrations on 3rd and 5th day after inoculation. No lesion was observed on leaves treated with 750 ppm of GSAgNPs. Leaf extracts (5%) were ineffective in disease suppression and pathogen growth. Mild symptoms were observed on leaves treated with the biocontrol agent (Pseudomonas fluorescens, 2%), while no symptoms were found on leaves treated with the fungicide. The best concentration of GSAgNPs (750 ppm) from in vitro assays was selected for in vivo pot culture study. In the in vivo assay, challenging with the pathogen after spraying the foliage of the foot rot susceptible black pepper variety Panniyur-1 with Pc-AgNPs at 750 ppm recorded the lowest percentage disease index (PDI) (15.55%) followed by that received 750 ppm Pn-AgNPs spray (17.77%), six days after inoculation. PDI for chemical control plants was 28.88% and that for plants treated with biocontrol agent was 37.77%. Highest PDI (77.77%) was observed for inoculated control plants. Peroxidase (PO), Phenylalanine ammonia lyase (PAL) and Polyphenol oxidase (PPO) from the treated plants were estimated on 2nd day, 4th day and 6th day after inoculation. Plants sprayed with Pc- AgNPs after pathogen inoculation showed the highest PO activity on the 4th day after inoculation (95.3 μg g-1min-1). Plants treated with 750 ppm of Pc-AgNPs after pathogen inoculation showed the highest PAL activity on 6 DAI (67.63 μg g-1min-1). The highest PPO activity was observed on 6 DAI and the corresponding values were in plants treated with 750 ppm of Pn AgNPs after pathogen inoculation (24.3 μg g-1min-1). The study revealed a significant increase in the defense enzyme activity in the plants sprayed with GSAgNPs (750 ppm), compared to the pathogen inoculated control plants without nanoparticle spray. This can be because of the action of GSAgNPs in triggering defense response. The present study suggests that AgNPs prepared with leaf extract of Piper spp. (Pn-AgNPs and Pc-AgNPs) effectively suppressed infection by P. capsici in black pepper at 750 ppm concentration, and these could be an effective and useful antifungal substitute for crop protection systems. However, multilocation field trials must be conducted to confirm the effectiveness of these nanoparticles. Studies to examine the residual toxicity of silver nanoparticles have also to be undertaken before field-level recommendations.
Wild edibile mushroom Termitomyces spp. for mycoprotein production
(Department of Plant Pathology, College of Agriculture,Vellayan, 2023-03-31) Anukrishna V J.; Susha, S Thara
The present study entitled “Wild edible mushroom Termitomyces spp. for mycoprotein production, was conducted at Department of Plant Pathology, College of Agriculture, Vellayani during 2020-2022 with an objective to collect and identify the native isolates of Termitomyces spp., in order to determine the optimal conditions for mycelial biomass cultivation and, exploiting the potential of this mushroom for mycoprotein production. A survey was conducted in agro ecological units 8, 9 and 12 of Kerala, during the South West and North East monsoon periods of 2021 and 2022. Twenty six native isolates of Termitomyces were collected from Thiruvananthapuram and Kollam districts. The most distinguishing characters of this mushroom is the presence of an umbonate cap with a prominent perforatorium and a subterranean pseudorhiza. Identification of species were carried out based on macro and micro morphological characters. The macro-morphological characterisation revealed that the cap size varies enormously between the species. The colour of the cap varied from white-cream to grey, light brown to dark brown between species. The pseudorhiza length varied from none (Termitomyces microcarpus) to 35 cm (Termitomyces heimii). The stipe was mostly cylindrical, smooth and glabrous. The spore print was pink in colour. Micro- morphological characterisation revealed that the basidia (18- 30 μm x 5 -9.5 μm) were clavate, bearing four sterigmata, cystidia (24-49 μm x 8-28 μm) were clavate to pyriform, hyaline and the basidiospores (5.5-8.5μm x 3.5-6 μm) were hyaline, ovoid to ellipsoid in nature. Based on morphological characteristics, twenty six Termitomyces samples were identified as ten species. The species confirmed through molecular characterization include Termitomyces eurrhizus, Termitomyces striatus, Termitomyces cylindricus, Termitomyces fuliginosus, Termitomyces microcarpus (large form and small form), Termitomyces radicatus, Termitomyces robusts, Termitomyces sp (1), Termitomyces sp (2) and Termitomyces heimii. Among the nine species, Termitomyces sp (1) and Termitomyces sp (2) were identified as two new species of Termitomyces, the first record from Kerala. It was observed that T. microcarpus (large form and small form) was the most commonly occurring and widely distributed species in Thiruvananthapuram and Kollam districts followed by T. fuliginosus. Cultural studies showed that potato dextrose peptone agar was the best media for mycelial growth of Termitomyces spp. Significantly the largest colony diameter and highest biomass yield of all isolates were observed on potato dextrose peptone agar. Termitomyces eurrhizus (best isolate) showed the largest colony diameter (7.800 cm ±0.100) and biomass yield (1.675 ± 0.006) when compared with other isolates. The growth response of T. eurrhizus to various carbon sources in basal medium (potato dextrose peptone broth) was tested. Higher mycelial biomass production was found in dextrose as carbon source. Peptone was the best nitrogen source to promote higher mycelial production. The optimum temperature, pH and light intensity were identified as 300C, 5.5 and 2000 lux respectively. Mycelial production was nil at 150C, 200C and 350C. The lower and higher pH (4.5 and 7.5) retarded the mycelial growth. The best two isolates (T. eurrhizus, and T. fuliginosus) were used for mycoprotein production. Pelletization was achieved in 100 ml potato dextrose peptone broth of pH 5.5 at 150 rpm in light (2000 lux) after incubation for 20 days at 29±10C. The two isolates produced good pellets evidenced by micro and macro pellets. Spherical to oval compact pellet morphology was common. The most promosing srain was T. eurrhizus which produced brownish to light orange coloured smooth spherical to oval compact pellets (diameter: 1-12 mm). T. fuliginosus produced whitish to light brown coloured pellets (1-11 mm). The proximate analysis of mycoprotein pellet revealed the constituents including crude protein (25. 7%), carbohydrate (36. 59%), fibre (9.91%) fat (3%) and ash (12.3%). The protein content was found to be more in the pellet (25.7%) as compared to the mushroom fruiting body (21.48%). In view of difficulty of domestication of the wild edible mushroom, Termitomyces spp., the only way to exploit the potential is through mycelial biomass production by submerged culture. The present study revealed the possibility of utilizing T. eurrhizus and T. fuliginosus for mycoprotein production.