Browsing by Author "Susha S Thara"

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Biocontrol of water hyacinth using fungal pathogens
(Department of Plant Pathology, College of Agriculture, Vellayani, 1997) Susha S Thara; Naseema, A
Detailed study was conducted on the host range of the already identified fungal pathogens of water hyacinth viz. Colletotrichum gloeosporioides, Fusarium eguiseti and F.pallidoroseum on thirty cultivated plants including vegetables, pulses and oil seeds, field crops, fruits and forest crops and ornamental plants and forty one common weed plants which are seen in and around water ways infested with water hyacinth. It was observed that C. gloeosporioides could infect amaranthus, bhindi, chilli, Euphorbia hirta, Hydrocotyl asiatica and Phyllanthus niruri. Of the thirty cultivated plants and forty one weed plants tested F. eguiseti was seen to be pathogenic to amaranthus, Amaranthus viridis, Commelina . bengalensis, C. jacobi and Monochoria vaginalis. F. pallidoroseum could produce symptoms on napier grass, Axonopus sp., boerhaavia diffusa, C.benghalensis, C.jacobi, Echinochloa colonum, Euphorbia hirta, Justicia diffusa, J.prostrata, M.vaginalis and Oldenlandia umbrellata and Scorpia dulcis. For the effective destruction of the weed, lxl011 spores per ml concentration of Q. gloeosporioides, E. eguiseti and F. pallidoroseum were found to be more effective than lxl09 and lxl010 spores per ml concentration. Cell free metabolites of the pathogenic fungi were found to produce symptoms on water hyacinth plant. Metabolite produced by E. pallidoroseum caused considerable damage than by E.equiseti and C. gloeosporioides. When pathogens were applied singly and in combination on water hyacinth it was observed that the combined application of F. pallidoroseum and F. equiseti followed by F. pallidoroseum alone gave maximum intensity of infection. Eventhough C. gloeospoirioides gave least intensity of infection it can be used as a co-pathogen with E. eguiseti. Metabolite of the pathogens individually and in combination when applied on healthy water hyacinth plants, maximum damage was caused by F.pallidoroseum alone and the combination of metabolite of three fungi viz. C. gloeosporioides,F equiseti and F. pallidoroseum. Least damage was caused by metabolite of C. gloeosporioides. An experiment was conducted to find out suitable carrier materials for the mass multiplication and storage of pathogen. It was observed that for C. gloeosporioides maximum sporulation was in water hyacinth leaf followed by guinea grass straw and rice bran. But the spore viability was maximum for rice straw, and on coir pith. Maximum infection was caused by fungus grown on guinea grass straw and rice straw. In the case of E. equiseti spore counts was higher in guinea grass straw followed by coir pith. The spore germination was maximum in rice bran and coir pith. Maximum infection was produced by the fungi on guinea grass straw, coir pith and waterhyacinth leaf. E. pallidoroseum produce maximum number of spores on rice bran followed by guinea grass straw. It was observed that the germination percentage of spores were maximum on coir pith. Out of the six carrier materials used the fungus produced maximum infection when grown on rice bran and guinea grass straw. In the study for testing the storage life of metabolities, it was observed that the efficiency to produce symptom was reduced on storage in the case of C. gloeosporioides and E. pallidoroseum whereas for E. eguiseti on storage the effeciency of the metabolite to cause damage increased. Metabolite stored on refrigerated condition performed poorly for all the three fungi. Different methods of application of the three fungi were tried. Of the five treatments, placement of bits and dusting the inoculum along with the carrier materials produced maximum infection. In the experiment conducted to characterize the toxin presented in the cell free metabolite of pathogenic fungi, observed the presence of Fusaric acid in the metabolite of Fusarium spp.
Comparative evaluation of different species of oyster mushroom suitable to Kerala
(Department of Plant Pathology, College of Agriculture, Padannakkad, 2022) Akhil, G L; Susha S Thara
he present study entitiled “Comparative evaluation of different species of Oyster mushroom suitable to Kerala” was carried out in the College of Agriculture, Padannakkad during 2019-2021 with the objective to identify the oyster mushroom species best suitable for cultivation under five agro-ecological zones of Kerala. Five species of Oyster mushrooms were selected for the study viz., Pleurotus florida, P. djamor, Hypsizygus ulmarius, P. sajor-caju and P. citrinopileatus. To evaluate the yield performance, five species were cultivated in farmer’s field of five agroecological zones of Kerala. The study also aims to evaluate the proximate constituents and medicinal components present in oyster mushrooms. Sensory evaluation and shelf life studies were also carried out. The sporocarps of five species of oyster mushrooms were studied for their morphological characters. P. florida produced white, delicate and fleshy sporocarp with an average weight of 11.71 g. P. djamor produced pinkish white leathery sporocarps with smaller pileus having very short stipe (0.8 cm). H. ulmarius produced creamy white fleshy sporocarps with significantly large pileus having average size of 7.0 cm x 7.52 cm. P. sajor-caju produced greyish white leathery sporocarp. P. citrinopileatus produced golden yellow delicate sporocarp with comparatively short stipe. The average size of pileus was 5.45 cm x 6.17 cm. Microscopic observations of hyphae and spores of five species of oyster mushrooms shows that hyphae of all the five species were septate, branched and hyaline with clamp connections. The width of the hyphae of all the five species ranged from 1.5- 4.5 μm. Basidiospores of P. florida and P. djamor recorded 7-12 μm in length and 2-5 μm in width whereas, H. ulmarius and P. sajor-caju produced spores with dimension of 8-12 μm× 3-6 μm. P. citrinopileatus produced spores with dimension of 7-10 μm× 2-3 μm. 141 Two substrates namely paddy straw and rubber sawdust were evaluated for the cultivation of five species of oyster mushrooms. Total yield from three harvests were significantly less in paddy straw, (954.66 g) compared to rubber sawdust which has given a yield of 1306.40 g. The yield recorded was highest for H. ulmarius cultivated on both paddy straw and rubber sawdust (1233 g kg-1 and 1611 g kg-1 respectively) which was followed by P. florida (1148.30 g kg-1 and 1582.66 g kg-1 respectively). It has been evident that selection of substrate significantly affected time taken for complete spawn run, time taken for pin-head formation, time taken for first harvest, total crop period and total yield from three harvests. The present study revealed that both the substrates viz., paddy straw and rubber sawdust were suitable for the cultivation of oyster mushrooms. So, both the substrates can be selected for cultivation based on the ease of availability and cost. In the present study, the suitability of five species of oyster mushrooms in five agro-ecological zones of Kerala were evaluated by cultivating the mushroom species at coastal plains, midland laterites, foothills, high hills and Palakkad plains. H. ulmarius was found to be the best suited oyster mushroom species for cultivation in coastal plains (102.99 % BE), foot hills (92.73 % BE) and high hills (123.30 % BE). In midland laterites and Palakkad plains, highest BE of 82.70 (%) and 103.80 (%) respectively were obtained from P. djamor. P. djamor, although reported to be performing well under warm conditions, yielded well under midland laterites and Palakkad plains. This may be due to low relative humidity and comparatively higher temperature in these zones. Earliness in primordial initiation (14-19 days) and extremely fast growth also make this species promising for cultivation in Kerala especially during dry months. The proximate analysis of five species of oyster mushrooms was carried out and it revealed that mushrooms are rich source of proteins, carbohydrates, fibres, amino acids, vitamins and minerals with less fat content. The protein content was highest in P. sajorcaju (26.02 %) and the fibre content was highest in P. florida (26.20 %). Fat content was the least in H. ulmarius with 1.70 per cent on dry weight basis. H. ulmarius (31.27 %) recorded the highest carbohydrate content among the five species of oyster mushrooms. 142 P. florida recorded the maximum moisture content (90.97 %). Highest amino acid content of 19.40 per cent was recorded from P. sajor-caju Analysis of mineral components revealed that highest content of sodium (965 ppm) and potassium (7175 ppm) was present in P. djamor. P. florida recorded highest content of calcium (1000 ppm) and magnesium (4025 ppm) which supports healthy immune system and keep bones strong. Medicinal analysis confirmed that these mushrooms were rich in bioactive components. P. djamor recorded highest content of β-glucan (30.25 g per 100g) having antitumour and immunomodulation activities, β-carotene (3.70 μg per 100g) having antioxidant properties and lovastatin (370.75 μg per 100g) which reduce blood cholesterol. P. sajor-caju recorded highest glycoprotein (435.00 μg per 100g) and terpenoid (1.26 %) content. Sensory evaluation of five species of oyster mushrooms was done using sauteed mushroom recipe to evaluate the quality attributes and consumability of the species. H. ulmarius recorded highest scores for appearance (8.83), colour (8.75), texture (8.66), flavour (8.58) and taste (8.83) on a maximum score of 9. H. ulmarius scored 8.80 in terms of overall acceptability followed by P. florida (7.60). Overall, from this study it was found that oyster mushrooms, especially H. ulmarius and P. florida are highly favoured for consumption. Shelf life of five species of oyster mushrooms were undertaken both in room temperature (26±20C) and in refrigerated conditions (150C). In the present study, comparatively higher shelf life was observed on P. djamor and P. sajor-caju which could be stored for two days after harvesting in room temperature and three days in refrigerated conditions. The present study demonstrated the exploitability of five species of oyster mushrooms in Kerala conditions. All the five species can be cultivated under the five agro-ecological zones of Kerala but H. ulmarius, P. florida and P. djamor yielded well compared to P. citrinopileatus and P. sajor-caju. H. ulmarius was found to be the best 143 suited oyster mushroom species for cultivation in coastal plains, foot hills and high hills. In midland laterites and Palakkad plains, highest yields were obtained from P. djamor can be economically cultivated regarding the yield and earliness in fruitin
Development of improved strain in oyster mushroom (Pleurotus spp.)
(Department of Plant Pathology, College of Agriculture, Vellayani, 2019) Jyothi, K R; Susha S Thara
The present study entitled “Development of improved strain in Oyster mushroom (Pleurotus spp.)” was carried out in College of Agriculture, Vellayani during 2017-2019 with the objective to develop improved strain of Pleurotus sp. from native isolates. Three native isolates used for the study viz., isolate 1 (Pleurotus djamor), isolate 2 (Pleurotus florida) and isolate 3 (a native isolate with 80 per cent similarity to P. florida), were obtained from Mushroom Unit of Instructional Farm, College of Agriculture, Vellayani. Species level confirmation of isolate 3 was done at molecular level ITS sequencing and was confirmed as P. ostreatus. The morphologic studies of the native isolates revealed that P. florida and P. ostreatus produced comparatively larger sporocarps with long stipe and higher carp weight than P. djamor. P. djamor, P. florida and P. ostreatus produced fruiting bodies with pink, white and greyish white colour respectively. The microscopic characteristics of the isolates were studied. The mycelia were septate and with clamp connections. The basidiospores were cylindrical and produced on tetra-sterigmatic clavate basidia present on the hymenium of the sporocarps. Strain improvement programme was conducted by spawn mixing, hybridisation through crossing of single spore cultures and gamma irradiation. The experiment was laid out in completely randomised design with required number of replications. Spawn of two different species viz., P. djamor + P. florida and P. djamor + P. ostreatus, were mixed and cultivation trials were conducted. For the given Pleurotus spp., hybridization or crossing of isolates did not take place by spawn mixing, thus did not have any significance in strain improvement. The beds of mixed spawn produced sporocarps of both parents. In addition, the biological efficiency (BE) of P. djamor + P. florida was reduced by 41.95 and 66.49 per cent respectively, compared to their parents. Similarly, BE of P. djamor + P. ostreatus was lower compared to their parents viz., P. djamor and P. ostreatus by 36.41 and 68.81 per cent respectively. Hybridization was carried out between the compatible single spore cultures of P. djamor with P. florida and P. ostreatus independently by dual culture method. The hybrids were confirmed by the presence of clamp connection in the mycelium from the interaction zone. The BE of the hybrids viz., P. djamor x P. florida and P. djamor x P. ostreatus, was improved by 34.40 and 48.49 per cent respectively over the parent, P. djamor. The days taken for primordial initiation in the hybrids were significantly reduced compared to their parents. The days were reduced in hybrid, P. djamor x P. florida by two and 13 days respectively than the parents; and three and 12 days in hybrid of P. djamor x P. ostreatus, compared to its respective parents. The hybrids showed blended characters of both their parents. Light pink coloured sporocarps with wavy margin and stout stipe was produced by the hybrid, P. djamor x P. florida and light pink coloured sporocarps with slight depression towards the base and increased stipe length was produced in the hybrid, P. djamor x P. ostreatus. Studies on the effect of gamma irradiation at 20 and 25 Gy in strain improvement revealed that BE of P. djamor increased by 9.25 per cent when irradiated at 20 Gy. The number of days taken for primordial initiation was also reduced by one day compared to P. djamor. Though P. florida irradiated at 25 Gy recorded increase in sporocarp size, there was no significant difference in the BE over P. florida. The BE of P. ostreatus irradiated at 25 Gy was improved by 12.89 per cent and there was earliness in primordial initiation by three days compared to the parent, P. ostreatus. The improved cultures were evaluated for their relative performance and it was found that BE was higher for the mutant of P. ostreatus irradiated at 25 Gy and increased by 12.3 per cent over the parent. Whereas the hybrids which recorded earliness in primordial formation with pink coloured slightly delicate sporocarps and improved BE were also found to be promising. Molecular characterisation of improved strains along with parents were analysed by RAPD (Random Amplified Polymorphic DNA). Pairwise comparisons of the strains, based on the presence or absence of unique and shared amplicons, were used to generate similarity coefficient of Jaccard. The results were then analysed using the unweighted pair-group method with arithmetic average (UPGMA). The analysis revealed that the hybrid (P. djamor x P. ostreatus) had 57.1 per cent similarity with P. djamor and 28.6 per cent similarity with P. ostreatus. The hybrid, P. djamor x P. florida had 66.7 and 50 per cent similarity with P. djamor and P. florida respectively. The mutant strain of P. ostreatus at 25 Gy recorded 22 per cent polymorphism with the control. The present study indicated the exploitability of two promising strains. The hybrid of P. djamor and P. ostreatus can be recommended for the production of slightly delicate, light pink sporocarps with reduced crop period (44.75 days). Whereas P. ostreatus irradiated at 25 Gy produced delicate white sporocarps with increased BE and reduced crop period by one week compared to the parent.
Etiology and management of fungal root rot of cassava in Southern Kerala
(Department of Plant Pathology, College of Agriculture , Vellayani, 2023-02-16) Amritha S Kartha; Susha S Thara
The research entitled “Etiology and management of fungal root rot of cassava in Southern Kerala” was conducted in the Department of Plant Pathology, College of Agriculture, Vellayani, during 2020-2022 with an objective of Identification and characterization of major pathogen causing fungal root rot in cassava and its management using different biocontrol agents and fungicides. During this study, root rot infected cassava plants were collected from different locations in the Thiruvananthapuram and Kollam districts of Southern Kerala. Twenty-one isolates of different fungi were obtained from root rot infected parts of cassava. Various symptoms such as yellowing of leaves, rotting of tubers and collar region of cassava stems, mycelial growth over the infected tubers and wilting of cassava plants were noticed in diseased samples from different locations. Based on the pathogenicity test conducted on potted cassava plants of one - month old Vellayani Hraswa variety, T3B (isolate from Thalayal of Thiruvananthapuram district) and K1B (isolate from Ezhukone of Kollam district) isolates were found to cause 100 Percent Disease Incidence (PDI). Based on the number of days taken for disease development, the isolate T3B (Fusarium sp.) was found to be most virulent with a PDI of 100, which took 30 days for symptom development, followed by K1B (Fusarium sp.) with PDI of 100 and 40 days for symptom development. Hence, T3B was selected for further studies. Cultural and morphological characteristics of the T3B isolate were studied. The colony was white cottony, with irregular margins on the front view and a light pinkish tinge on the rear view. Microscopic characters of the T3B isolate revealed that the mycelia were septate and hyaline. Macroconidia and microconidia were produced abundantly on conidiophores. Macroconidia were hyaline, septate (0-2 septa), slender, almost straight and elongated with blunt ends, while the microconidia were slender, hyaline, and single celled with oblong shape. Chlamydospores were absent. Molecular characterization of T3B isolate was carried out using ITS sequencing using universal primers followed by comparative nucleotide sequence alignment with the available database from NCBI. The isolate T3B was confirmed as Fusarium proliferatum with 99.79 per cent homology with F. proliferatum strain OR25F07 (MT476359.1) and the dendrogram was also constructed as a distance tree which showed a phylogenetic relationship. The nucleotide sequence of the T3B isolate was deposited in GenBank and the accession number was retrieved as OQ376433. As part of the study, microflora was isolated from the rhizosphere of healthy cassava plants from Vellayani and Venganoor of Thiruvananthapuram district in Kerala. Among the isolated bacterial and fungal rhizosphere microflora, viz., Aspergillus sp. 1, Aspergillus sp. 2 Bacteria 1 and Bacteria 2, Aspergillus sp. 1 from Vellayani showed the highest inhibitory effect against the pathogen with 64.84 per cent inhibition. The in vitro antagonism of seven biocontrol agents viz., Pseudomonas fluorescens PN026, Bacillus sp. isolate 1 and Bacillus sp. isolate 2 (RRS, Moncompu), Trichoderma sp. 1, Trichoderma sp. 2 (KAU), Piriformospora indica (No. INBA 3202001787) and Aspergillus sp. 1 (selected antagonist) were evaluated against F. proliferatum by dual culture technique and results revealed that highest percentage inhibition was recorded with Trichoderma sp. 1 (57.57 %) followed by Trichoderma sp. 2 (51.51 %). The in vitro evaluation of fungicides through poisoned food technique against F. proliferatum was conducted using eight fungicides viz., mancozeb 75% WP, copper oxychloride 50% WP, propineb 70% WP, carbendazim 50% WP, propiconazole 25 % EC, cymoxanil 8% + mancozeb 64% WP, carbendazim 12% + mancozeb 63% WP and trifloxystrobin 25%+ tebuconazole 50 % 75 WG at 50, 100 and 200 ppm. The highest per cent inhibition was showed by carbendazim 50% WP and trifloxystrobin 25%+ tebuconazole 50 % 75 WG at 200 ppm with an inhibition percentage of 87.87% and 100%, respectively. Carbendazim 50% WP and trifloxystrobin 25%+ tebuconazole 50 % 75 WG were the most effective fungicides used for in vitro assay. A pot culture study was undertaken with the Vellayani Hraswa variety to evaluate the efficacy of effective biocontrol agents and fungicides, viz., Trichoderma sp. 1. Trichoderma sp. 2 (KAU), carbendazim 50% WP and trifloxystrobin 25%+ tebuconazole 50 % 75 WG against F. proliferatum and results shown that the highest disease suppression over control was recorded with Trichoderma sp. 2 (100.00%) followed by Trichoderma sp. 1 (88.89%) and trifloxystrobin 25%+ tebuconazole 50 % 75 WG (77.78%) with sett treatment and soil application at one and two months after planting. The highest yield of 1342.66 g per plant was obtained from treatment with Trichoderma sp. 2 @108 cfu/ml followed by trifloxystrobin 25%+ tebuconazole 50% 75 WG @1 gL-1 (1106.00 g per plant) and Trichoderma sp. 1 @108 cfu/ml (1003.66 g per plant). The present study revealed that Fusarium spp., Lasiodiplodia spp., Colletotrichum spp. and Rhizoctonia spp. were associated with root rot of cassava in Southern Kerala. The most virulent pathogen was identified as Fusarium prolifaratum by analysing the cultural, morphological and molecular characteristics. The sett treatment and soil application of biocontrol agent Trichoderma sp. 2 (KAU isolate) (108 cfu/ml) or the fungicide trifloxystrobin 25%+ tebuconazole 50% 75 WG (1 gL-1 ) at one and two months after planting can effectively manage the disease.
Evaluation and improvement of production technology of paddy straw mushroom (volvariella sp.)
(Department of Plant Pathology, College of Agriculture, Vellayani, 2017) Brinda, G B; Susha S Thara
Expression profiling of laccase and β-Glucan synthase genes in Pleurotus ostreatus during different developmental stages
(Department of Plant Biotechnology, College of Agriculture , Vellayani, 2022-10-21) Nesma, A S; Susha S Thara
The study entitled “Expression profiling of laccase and β-glucan synthase genes in Pleurotus ostreatus during different developmental stages” was conducted at College of Agriculture, Vellayani. The objective of this study was to analyze the differential expression of laccase and β-glucan synthase genes in two strains of P. ostreatus during different developmental stages using quantitative Real-Time PCR (qRT- PCR). Two strains of P. ostreatus viz., DMR P115 collected from the Directorate of Mushroom Research (DMR), Solan, Himachal Pradesh and HUC collected from the Department of Plant Pathology, College of Agriculture, Vellayani were used for the study. Samples were collected from four different developmental stages viz., mycelium, primordium, young fruiting body and mature fruiting body of P. ostreatus strains. Potato Dextrose Agar (PDA) and Potato Dextrose Broth (PDB) were used for maintaining the pure cultures of both strains. The cultural and morphological studies of mycelia revealed that DMR P115 strain formed maximum radial growth on the 3rd, 5th, 7th and 9th day. However, white, thick and fluffy growth with radiating margins were observed in both strains. To obtain fruiting bodies, the spawn of both strains was prepared on paddy grains and inoculated on sterilized rubber sawdust substrate. The morphological studies of the mushroom fruiting body revealed that DMR P115 took minimum days for spawn run, days to produce primordia, days to produce young fruiting body and days for maturity. Sporophore characters like stipe length, stipe diameter, pileus length, pileus diameter and average weight of fruiting body were higher in DMR P115 strain than in HUC strain. Maximum yield (747.429 g/kg of the substrate) and the number of sporophores (84.429) were observed in DMR P115 strain. The expression of laccase (POXA3) and β-glucan synthase (FKS) genes that are important in fruiting body development and cell wall formation respectively was analysed at different developmental stages of two strains by performing qRT-PCR. There was a significant difference in the expression of POXA3 and FKS genes in different developmental stages of the two strains. The expression of POXA3 was higher in the mycelial stage of DMR P115 (5.58 fold) and HUC (2.03 fold) strains. FKS gene 81 was upregulated in mycelium (29.24 fold) and mature fruiting body (58.48 fold) of DMR P115 strain whereas in HUC strain, there was a significant upregulation only in the mycelial stage (17.15 fold). It can be concluded that the growth and gene expression pattern in DMR P115 and HUC strain varies. The expression of POXA3 and FKS genes differ significantly in different developmental stages of the two strains. POXA3 gene, which is essential for its fruiting body development and degradation of the substrate was upregulated in the mycelial stage of both strains. FKS gene was upregulated in the mycelium and mature fruiting body of DMR P115 strain and the mycelial stage of HUC strain which indicates the antioxidant and immunostimulatory properties of that strain. The findings obtained from this study can be used as a foundation for future lines of research related to strain improvement of P. ostreatus.
Integrated management of alternaria leaf spot of cabbage (Brassica oleracea var. capitata (L.))
(Department of Plant Pathology, College of Agriculture, Vellayani, 2018) Madhu Kiran Gunda, V N S; Susha S Thara
Management of postharvest anthracnose of banana using green nanoparticles
(Department of Plant Pathology, College of Agriculture , Vellayani, 2023-12-16) Ajay, B; Susha S Thara
A study entitled ‘Management of postharvest anthracnose of banana using green nanoparticles’ was conducted during 2021-23 at Department of Plant Pathology, College of Agriculture, Vellayani with the objective to characterize the major pathogen associated with anthracnose of banana fruits and its management using green nanoparticles. A survey was conducted in local markets of five agro-ecological units of Kerala viz., AEU 1, AEU 3, AEU 8, AEU 9 and AEU 12 covering Thiruvananthapuram, Kollam and Alappuzha districts. A total of 34 locations were surveyed during 2021-23 to collect the diseased specimens of banana Nendran variety (Musa AAB) and to study the symptomatology of the disease. Variations in symptoms were noticed from different locations such as black or brown sunken spots of various sizes, shriveling of fruits and spots having triangular shaped or angular edges. The pathogens were isolated from the collected specimens; a total of 62 isolates were obtained out of which 34 isolates were Colletotrichum sp. and Koch’s postulates were proved in matured harvested dehanded banana. All the 34 Colletotrichum sp. isolates were screened for its virulence and pathogenicity. The isolate K1B1 from Kollam corporation (AEU 1- Kollam district) recorded the highest Percent disease index (PDI) of 83.33 per cent with a highest lesion size of 5.10 x 4.95 cm on the 5th day of artificial inoculation; and hence concluded as the most virulent isolate. Cultural and morphological studies of isolate K1B1 were carried out. Initially white to grey floccose aerial mycelium was observed which turns orange colour with age. Microscopic studies revealed that mycelia were hyaline and septate, acervulus were brown without setae, conidia were hyaline aseptate with elliptical or cylindrical shape and appressorium were dark brown and irregular shaped. Based on the cultural and morphological studies, isolate K1B1 was identified as Colletotrichum musae. Further molecular characterization of the isolate K1B1 was done using ITS primers and the isolate was confirmed as Colletotrichum musae. In vitro evaluation of prepared essential oil nanoemulsions (NEs) viz., cinnamon oil NE, clove oil NE, basil oil NE, neem oil NE and mustard oil NE at 0.5 %, 1 % and 2 % against C. musae in PDA by poisoned food technique revealed that all the essential oil NEs significantly reduced the growth of C. musae over control. The highest inhibition (100 %) at the lowest concentration (0.5 %) was observed in cinnamon oil NE and clove oil NE followed by basil oil NE (96.66 %). In vitro evaluation of prepared green copper nanoparticles (CuNPs) synthesized using leaf extracts of neem, ocimum, clove, American mint, and cinnamon at 0.05 %, 0.1 % and 0.2 % against C. musae by poisoned food technique revealed that all the synthesized green CuNPs significantly reduced the growth of C. musae over control. The highest inhibition (100 %) at the lowest concentration (0.05 %) was observed in green CuNPs synthesized using leaf extracts of cinnamon and clove followed by green CuNPs synthesized using leaf extracts of neem (97.58 %). In vitro evaluation of chitosan NPs (60 nm) at 0.5 %, 1 % and 2 % in comparison with the best three treatments from essential oil NEs (cinnamon oil NE, clove oil NE and basil oil NE at 0.5 %) and green CuNPs (Synthesized using leaf extracts of cinnamon, clove and neem at 0.05 %) against C. musae by poisoned food technique revealed that the essential oil NEs and the green CuNPs significantly reduced the growth of C. musae over control. Chitosan NPs didn’t show any reduction in the growth of the pathogen.The highest inhibition (100 %) at the lowest concentration was observed in cinnamon oil NE (0.5%), clove oil NE (0.5%), green CuNPs synthesized using leaf extracts of cinnamon (0.05%) and clove (0.05%) followed by green CuNPs synthesized using leaf extracts of neem (97.58 % at 0.05%). Based on the results of in vitro evaluation, the best five treatments (cinnamon oil NE, clove oil NE, green CuNPs synthesized using leaf extracts of cinnamon, clove and neem) were taken for in vivo studies along with carbendazim (0.1 %), pathogen inoculated control and uninoculated control. All the tested green NPs significantly reduced the lesion formation in matured harvested dehanded banana. Lowest lesion size of 0.86 cm and 1.46 cm was recorded in green CuNPs synthesized using leaf extracts of cinnamon and clove respectively followed by cinnamon oil NEs (2.60 cm). Similarly, the highest percent disease reduction over control was observed in green CuNPs synthesized using leaf extracts of cinnamon (99.01 %) and clove (98.28 %) followed by cinnamon oil NE (97.56 %). The best three green NPs (Green CuNPs synthesized using leaf extracts of cinnamon and clove and cinnamon oil NE) from in vivo studies were characterized. The formation of green CuNPs synthesized were confirmed by a characteristic peak obtained at 800 nm by UV-Vis spectroscopy.The results from FT-IR (Fourier transform infrared spectroscopy) analysis conclude that the surface of synthesized CuNPs were capped and stabilized by flavonoids and other phenolic compounds in the leaf extracts. The morphological characterization of CuNPs using FESEM (Field emission scanning electron microscopy) and HRTEM (High resolution transmission electron microscopy) revealed the presence of spherical particles with some agglomeration and the size of the particles was found to be in the range of 20 – 60 nm. DLS (Dynamic light scattering) analysis was used to find out the surface charge of NPs and the negative zeta potential was found at -22.2 mV, -21.7 mV and -25.8 mV for green CuNPs synthesized using leaf extracts of cinnamon, clove and cinnamon oil NE respectively. The X-ray diffraction (XRD) analysis of green CuNPs revealed the crystalline structure of CuNPs. The shelf life and organoleptic properties (appearance with and without skin, colour with and without skin, texture, taste, flavor and overall acceptability) of the banana fruits treated with green nanoparticles was evaluated along with the uninoculated control and pathogen inoculated control and the green CuNPs synthesized using leaf extracts of cinnamon was noticed with highest shelf life (9 days) and excellent organoleptic properties followed by green CuNPs synthesized using leaf extracts of clove (8 days) and cinnamon oil NE (7 days). Based on the results of in vivo evaluation, the best three treatments (Green CuNPS synthesized using leaf extracts of cinnamon, clove and cinnamon oil NE) were taken for the study of biochemical changes (Reducing sugar, ascorbic acid, titratable acidity, protein, moisture and pH) in comparison with the uninoculated control and pathogen inoculated control. The green CuNPs synthesized using leaf extracts of cinnamon was noticed with less biochemical changes with a decrease in reducing sugar (8.30 %), decrease in ascorbic acid (62.56 mg/100g), decrease in titratable acidity (0.59 %), decrease in protein (5.08 mg/g fresh weight), increase in moisture (56.24 %) and acidic in pH (3.40) when compared with the uninoculated control with reducing sugar (8.87 %), ascorbic acid (62.77 mg/100g), titratable acidity (0.60 %), protein (5.25 mg/g fresh weight), moisture (55.88 %) and pH (3.41) followed by green CuNPs synthesized using leaf extracts of clove and cinnamon oil NE. The present study revealed that the major pathogen associated with anthracnose of banana fruits is Colletotrichum musae. The postharvest spraying of green CuNPs synthesized using leaf extracts of cinnamon at 0.05 % is proved to be an effective novel strategy for the management of banana anthracnose with higher shelf life (9 days) and excellent organoleptic properties. The results may be subjected to multi-location and multi seasonal field trials and the residual toxicity of CuNPs on the fruits have to be undertaken.
Management of postharvest crown rot of banana using biocontrol agents and essential oils
(Department of Plant Pathology, College of Agriculture, Vellayani, 2019) Deepa R Chandran; Susha S Thara
Management of stem rot and foliar blight of cowpea (vigna unguiculata (L.) walp.)
(Department of Plant Pathology, College of Agriculture, Padannakkad, 2020) Nayana Sunil, M V; Susha S Thara
Monographic studies on agaricus species of Kerala
(Department of Plant Pathology, College of Agriculture, Vellayani, 2001) Susha S Thara; Bhavani Devi, S
The warm humid climatic conditions and wide diversity in soil types and pattern favoured a luxuriant growth of a wide variety of fungal flora in Kerala. In the present study collections were made during south-west and north-east monsoon periods of 1998-2000 in twenty agro climatic zones of Kerala and forty two species of Agaricus were collected. Among the 42 species collected A. abruptibulbus, A. actinorachis, A. altipes, A. annae, A. arenicolus, A. benesi, A. bernardii, A. bulbosus, A. caroli, A. chloroconius, A. ingrata, A. lividonitidus, A. mediojuscus, A. microflavus, A. micromegethus, A. microrubescens, A. moelleri, A. nivescens, A. ochraceous, A. ochroflavus, A. phaeolepidotus, A. pseudopratensis, A. purpurellus, A. rubicolus, A. rusiophyllus, A. semotus, A. silvicola, A. simulans, A. spissarujosa, A. squamuliferus, A. stadii, A. subperonatus, A. trisulphuratus and A. xantholepis are new reports from Kerala. Among these A. abruptibulbus, A. annae, A. arenicolus, A. benesi, A. bernardii, A. bulbosus, A. caroli, A. chloroconius, A. ingrata, A. lividonitidus, A. mediojuscus, A. microflavus, A. microrubescens, A. moelleri, A. nivescens, A. ochraceous, A. ochroflavus, A. phaeolepidotus, A. purpurel!us, A. rubicolus, A. rusiophyllus, A. simulans, A. spissarujosa, A. stadii and A. subperonatus are first reports from India. A. bulbosus, A. ochraceous, A. ochroflavus, A. microflavus, A. microrubescens, A. rubicolus and A. spissarujosa are the new reports during the study. 'f. Most of the collections were obtained during May-June and September- October months coinciding with the early south-west and north-east monsoon periods. The species of the Genus Agaricus preferred laterite soils. Growth of Agaricus species was maximum on complete medium and they preferred a temperature range between 25 and 30DC and pH 6. The results of the studies revealed that light did not play any significant role on growth of the fungi. Among the different carbon sources tried Agaricus spp. preferred glucose, sucrose and fructose. Agaricus spp. exhibited best growth in organic nitrogen compared to inorganic sources of nitrogen. From the study it was observed that wheat gram IS best for the production of spawn of A. bitorquis and maximum growth was obtained when incubated at 25 and 30DC. Spawn run of A. bitorquis was observed in traditional compost and pinheads started appearing within 30-35 days after spawning. The buttons can be harvested on fourth or fifth day after pinhead emergence. 400 g of buttons were obtained from 10 kg compost and this preliminary study showed the possibilities of commercial cultivation of this excellent mushroom species under Kerala condition.
Strain improvement of Trichoderma spp.for management of foot rot of black pepper caused by phytophthora capsici
(Department of plant pathology, College of Agriculture, Vellanikkara, 2025-09-22) Alby John; Susha S Thara
The research work entitled ‘Strain improvement of Trichoderma spp. for management of foot rot of black pepper caused by Phytophthora capsici’ was conducted at Department of Plant Pathology, College of Agriculture, Vellayani during 2022-2025 with an objective of enhancing the antagonistic potential and growth promotion of Trichoderma strains by protoplast fusion and mutagenesis; studying the biochemical and molecular mechanisms underlying antagonism and evaluation of its efficacy for managing P. capsici. Five promising isolates of Trichoderma spp.: TRMW-2, TRKR-2, TRPN-3, TRPN-11 and TRPN-17, previously collected from different agroclimatic zones of Kerala, along with Trichoderma asperellum, the reference culture from KAU were used as the parental isolates. Molecular characterization using species-specific primers (TEF1 and RPB2) and multi-gene phylogenetic analysis identified TRMW-2, TRKR-2, TRPN 3, TRPN-11 and TRPN-17 as Trichoderma brevicompactum [Tb], Trichoderma koningiopsis [Tk], Trichoderma pholiotae (PN3) [Tp (PN3)], T. pholiotae (PN11) [Tp(PN11)] and Trichoderma guizhouense [Tg], respectively. A total of 15 protoplast fusion combinations were performed using the six parental isolates and 30 fusants with a colony diameter exceeding 8.5 cm at 48 h were screened. Among these, the 10 most effective fusants, exhibiting a growth inhibition rate of 85.73% to 92.13% against P. capsici were selected based on their mycelial growth suppression. Simple sequence repeat (SSR) marker analysis was performed using 15 primers to determine whether the selected fusants were interspecific. Similar amplification patterns were observed between the fusants Ta × Tk-1, Tk × Tp (PN3)-1, Ta × Tp (PN3)-1 and Ta × Tp (PN3)-5 and their respective parental strains for the markers PRB ATC, TV1, KON 700, TA4, TA9 and TH5, confirming them as interspecific fusants. Strain improvement through UV irradiation (5, 10 and 15 min) exhibited an inverse correlation between exposure time and the number of regenerated colonies. Among 140 mutants screened, 30 with a colony diameter greater than 7.5 cm at 48 h were selected, which were further narrowed down to 10 with the highest inhibition rates of 80.87% - 84.47% against P. capsici. Similarly, gamma irradiation (150, 200, 250 and 300 Gy) showed a negative correlation between colony regeneration and radiation dose. Among 180 mutants screened, 10 superior mutants with a growth inhibition of 81.67% - 90.40% were selected. From the 30 improved Trichoderma spp. strains obtained through three distinct strain improvement techniques, the 10 most effective strains exhibiting significant pathogen inhibition (83.73% to 93.60%) were identified and subjected to genetic stability assessment via ten successive subculturing rounds, followed by dual culture assay against P. capsici. The five most promising Trichoderma strains: T. asperellum × T. koningiopsis-1 [Ta × Tk-1], T. koningiopsis ×T. pholiotae (PN3)-1 [Tk × Tp(PN3)-1], T. pholiotae (PN11) fifth UV mutant colony irradiated for 5 min [Tp(PN11).5m5], T. pholiotae sixth gamma mutant colony irradiated at 200 Gy [Tp(PN3).200m6] and T. asperellum first gamma mutant colony irradiated at 250 Gy [Ta.250m1] with superior mycelial growth suppression (83% to 91.27%) were selected. Culture filtrate assay at 50% concentration revealed maximum mycelial inhibition of P. capsici by Tk × Tp(PN3)-1 (98.33%) and Tp(PN11).5m5 (97.92%). Additionally, Ta × Tk-1 (76.13%) and Tp(PN3).200m6 (72.25%) exhibited significant volatile metabolite activity against P. capsici, outperforming T. asperellum (59.88%). The potential of the selected Trichoderma spp. strains to produce lytic enzymes, including β-1,3 glucanase, protease, chitinase and lipase was evaluated. Ta × Tk-1, Tk × Tp(PN3)-1, Tp(PN11).5m5 and Ta.250m1 exhibited higher enzymatic activity than T. asperellum, signifying enhanced antagonistic potential. Growth promoting attributes, including IAA (174.41 μg ml-1) and siderophore production (77.09%) were highest in the interspecific fusant Ta × Tk-1, while phosphate solubilization was most pronounced in the gamma mutant Ta.250m1(1326.90 μg ml-1). Cultural and morphological characterization of the improved strains revealed distinct variations in conidiation, pigmentation, hyphal width and conidial and phialide size compared to their parental isolates. Notably, Tp(PN3).200m6 exhibited deep yellow pigmentation, while Ta × Tk-1 and Ta.250m1 showed dense sporulation. Pot culture experiments were conducted to evaluate the biocontrol efficacy and plant growth promoting potential of five promising Trichoderma spp. along with T. asperellum in black pepper var. Panniyur - 1. Biometric characters (plant height, number of leaves, nodes and internodal length) were highest in plants treated with Ta × Tk-1, followed by Ta.250m1. Upon challenge inoculation with P. capsici, lesion size was smallest in plants treated with Tk × Tp(PN3)-1 and Tp(PN11).5m5, corresponding to a percent disease index of 20.19% and 35.44% respectively, compared to 83.57% in control plants. Elevated activity of defense related enzymes (peroxidase, polyphenol oxidase, phenylalanine ammonia-lyase, catalase and superoxide dismutase) was recorded in plants treated with Tk × Tp(PN3)-1, Tp(PN11).5m5 and Ta × Tk-1. The relative expression of antagonism associated genes from different functional groups; chitinase, β-1,3-endoglucanase, subtilisin-like protease and terpene synthase were analyzed in both improved Trichoderma strains and their respective parental isolates using semi-quantitative RT-PCR. Expression levels were significantly upregulated in Tk × Tp(PN3)-1 and Tp(PN11).5m5 across all four genes compared to the parental isolates. This study identified three improved Trichoderma strains; Ta × Tk-1, Tk × Tp(PN3)-1 and Tp(PN11).5m5 that exhibited enhanced antagonistic potential, biochemical characteristics, plant growth promoting traits and defense enzyme activities, surpassing the reference strain T. asperellum. Therefore, following multi-locational field trials across different crops and comprehensive toxicological studies, these strains could be released as efficient biocontrol agents in the future.
Studies on the variability of rhizoctonia solani kuhn. infecting rice cowpea abd amaranth
(Department of Plant Pathology, College of Agriculture, Vellayani, 2020) Haritha Kumar, J; Susha S Thara