1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)
Permanent URI for this communityhttp://localhost:4000/handle/123456789/1
Browse
4 results
Search Results
Item Interaction between root-knot nematode and fungal pathogens in black pepper, Piper nigrum L.(Department of Nematology, College of Agriculture, Vellayani, 2024-04-09) Amruth Hari; Nisha, M SThe study entitled " Interaction between root-knot nematode and fungal pathogens in black pepper, Piper nigrum L." was conducted at the Department of Nematology, College of Agriculture, Vellayani, Thiruvananthapuram during 2021- 2023. The objectives were documentation of nematodes and fungal pathogens in the rhizosphere of black pepper, the interaction between root-knot nematode and fungal pathogens, histopathological and biochemical changes due to nematode-fungal disease complex in black pepper. A survey was conducted in the major black pepper growing areas of Kannur (AEU-15), Idukki (AEU-16) and Wayanad (AEU-21) districts to document the nematode fauna and fungal pathogens associated with black pepper. The plant parasitic nematodes identified were Meloidogyne incognita (Kofoid and White) Chitwood, Rotylenchulus reniformis Linford and Oliveira, Radopholus similis (Cobb), Helicotylenchus dihystera (Cobb) Sher and Macroposthonia sp. The highest population of M. incognita and R. reniformis was recorded in Padiyoor and Malapattam areas in Kannur district with prominence value (PV) of 14.99 and 12.29 respectively. In Idukki and Wayanad districts highest population of M. incognita was recorded in Marayoor and Panamaram with PV of 14.76 and 15.48 respectively. Fungal pathogens viz. Fusarium solani, F. oxysporum, Phytophthora sp. Rhizoctonia sp. and Pythium sp. were also isolated from soil and plant samples. Occurrence of F. solani and high population of M. incognita was recorded in Padiyoor and Irikkur areas in Kannur, Marayoor and Mattukatta areas of Idukki and Panamaram and Pulpally regions of Wayanad. Severe galling and yellowing were observed in plants infested with nematode and fungi. A pot culture study was conducted to investigate the interaction between M. incognita and F. solani, since F solani was observed to be the major fungal pathogen associated with nematode infested plants in surveyed locations. The interactive effect of nematode and fungus in plant growth parameters, nematode multiplication, and disease incidence in black pepper were observed. The experiment was laid out in a completely randomized design and the treatments were M. incognita alone, F. solani alone, simultaneous inoculation of M. incognita and F. solani, M. incognita + F. solani two weeks after nematode inoculation, F. solani + M. incognita two weeks after fungus inoculation, and uninoculated control. M. incognita was inoculated @one J2 g soil-1. F. solani was mass multiplied in sand maize medium and mixed with soil (0.5% w/w). After 45 days of inoculation, 55.00 to 70.21 per cent reduction in in plant growth parameters over uninoculated control was observed in plants inoculated with M. incognita fourteen days prior to fungus inoculation. Number of galls, females, egg 119 masses and nematode population were found significantly higher in plants inoculated with nematode alone followed by M. incognita + F. solani fourteen days after nematode inoculation. Reproduction factor of nematode was higher (4.12) in the treatment where, M. incognita was inoculated alone and in all other treatments it ranged from 2.72 to 3.39. Plants inoculated with M. incognita fourteen days prior to F.solani exhibited highest disease incidence (100 per cent) and early symptom development (24 days). The results point out that the nematode infestation can predispose plants to fungal infection and thereby can increase the disease severity in field conditions. After 45 days of inoculation, histopathological and biochemical changes due to M. incognita and F. solani was analysed. Largest (909.2 µm2) and highest number (5) number of giant cells in vascular bundles was observed in plants inoculated with M. incognita alone followed by M. incognita inoculated two weeks prior to fungus inoculation. Fungal mycelium plugging in xylem vessels were observed in all the treatments in which the M. incognita and F. solani were inoculated sequentially and simultaneously. The plugging in xylem vessels were comparatively less in the treatment where F. solani was given alone, showing that presence of nematode increases the activity of fungus. Regarding biochemical changes, the highest amount of phenol was observed in leaves (0.49 mg g tissue -1) and roots (1.75 mg g tissue-1) of plants inoculated with M. incognita + F. solani fourteen days after nematode inoculation. Defence enzymes viz., peroxidase (PO) (8.93 fresh weight), phenyl alanine ammonia lyase (PAL) (16.31 µg of cinnamic acid fresh weight) and polyphenol oxidase (PPO) (6.98 fresh weight) in leaves also increased in plants inoculated with M. incognita + F. solani fourteen days after nematode inoculation. Similar trend was observed in root samples also. Higher activity of phenol and defense related enzymes can be attributed to the defense induced in plants due to the increased infection by nematode and fungus. The protein content was found higher in leaves (3.22 µg of BSA g-1 fresh weight) and roots (3.46 µg of BSA g-1 fresh weight) of the uninoculated plants compared to plants inoculated with nematode and fungus. The decrease in protein content on inoculated plants can be due to the increased use of amino acids by galls or giant cells thereby reducing their availability for protein synthesis. Investigations of the present study highlighted that plant parasitic nematodes viz. M. incognita, R. reniformis, R. similis, H. dihystera and Macroposthonia sp and fungal pathogens viz. F.solani, F. oxysporum Phytophthora sp., Pythium sp. and Rhizoctonia sp. were found associated with black pepper grown in Kannur, Idukki and Wyanad districts of Kerala. Prior inoculation of M. incognita enhanced nematode multiplication and 120 disease incidence as evidenced by increased number of giant cells, distortion of vascular bundles and plugging of fungal mycelia in xylem vessels.Item Identification of major fungal pathogens of dragon fruit and management of its major disease(Department of Plant Pathology, College of Agriculture, Vellayani, 2023-12-29) Kovvuri Janakadatta Reddy; Dhanya, M KThe research study entitled "Identification of fungal pathogens of dragon fruit and management of its major disease" was carried out at the Department of Plant Pathology, College of Agriculture, Vellayani, from 2021 to 2023 to identify and characterize the prevailing fungal pathogens of dragon fruit plants grown in Southern Kerala and develop an integrated management strategy against its major diseases. Two dragon fruit cultivating regions, AEU 09 (south-central laterite) and AEU 12 (southern and central foothill) in Kerala, were surveyed to identify the major fungal pathogens and associated symptoms on dragon fruit plants. Stem canker, characterized by yellow spots that further progressed into orange-brown lesions with yellow haloes, was observed in plantations of Palode and Vembayam regions of Thiruvananthapuram district. In the Vellavoor block of Kottayam district (AEU 12), a widespread outbreak of a wilt disease caused by Rigidoporus spp. was recorded. In Palode region (AEU 09), Fusarium infection was prevalent, where soft rot symptom was observed near the soil line and brownish-red lesions on the stems/cladodes. Neoscytalidium spp, Fusarium spp, and Rigidoporus spp were isolated from the infected samples collected from various locations. Three isolates of Neoscytalidium spp (I1, I3, I5) were obtained from Palode, Vembayam, and Pala regions respectively. Among them, the isolate (I1) was found to be more virulent, and hence selected for further studies. The pathogenicity of these isolates was confirmed by artificial inoculation on healthy dragon fruit cladodes and fruits, and Koch's postulates were established. The morphological and cultural characteristics of each isolate was examined on potato dextrose agar (PDA) medium. Neoscytalidium isolates (I1, I3, I5) exhibited greyish colonies with dark grey to black pigmentation. The average growth rate of these isolates was about 1.06 cm per day. Their hyphae were characterized by brown colour, branching pattern, and septation. Conidia of various shapes and colours were formed in chains (arthroconidia). The Isolate I2 had white aerial mycelium with concentric rings and sickle-shaped conidia. The Isolate I4 produced dense cottony white mycelia with an average growth rate of 0.87 cm per day. Molecular characterization with ITS primers indicated that isolates I1, I3, and I5 had 97.21 Per cent similarity with Neoscytalidium spp reported from Malaysia, and China respectively. The isolates I2 and I4 showed 95.29 Per cent and 100 Per cent similarity with Fusarium spp and Rigidoporus spp reported from India and Malaysia respectively. DNA of isolate I2 on amplification in PCR with ITS and TEF primers revealed 100 per cent similarity to F. fujikuori Potential of biocontrol agents, including Bacillus amyloliquefacians, Pseudomonas fluorescens, Trichoderma asperellum (KAU isolate), and T. harzianum (IISR isolate), were tested against the above pathogens. T. harzianum significantly inhibited the hyphal growth of Rigidoporus sp. whereas T. asperellum showed 75.62 Per cent inhibition against Fusarium spp and 66.85 Per cent inhibition against Neoscytalidium spp. In vitro studies with fungicides revealed that even lower concentrations of the Bordeaux mixture (0.25%) completely inhibited the growth of Neoscytalidium spp. Among systemic fungicides, Difenoconazole (0.2%) showed 100 Per cent inhibition, whereas carbendazim + mancozeb (0.05%) was identified as the best combination fungicide against the pathogen. Against Fusarium spp and Rigidoporus spp, given lower concentrations of fungicides i.e., BM (0.25%), Difenoconazole (0.025%), and Trifloxystrobin + Tebuconazole (0.013%) gave 100 Per cent inhibition. Among the chemicals, all concentrations of potassium phosphonate, calcium chloride, and sodium carbonate showed 100 Per cent inhibition of Rigidoporus spp. All doses of calcium chloride showed cent percent inhibition for Fusarium spp, while recommended and double doses of calcium chloride and potassium phosphonate were found effective against Neoscytalidium spp. Compatibility of promising fungicides and chemicals with potent bioagents was carried out based on the results of an in vitro study. Calcium chloride and potassium phosphonate showed maximum compatibility with B. amyloliquefacians and T. asperellum respectively. A pot culture study was conducted to find out the effective treatments against stem canker disease of dragon fruit which is identified as the most prevalent and devastating disease during the study period. Prophylactic application of T. asperellum enriched FYM @100 g plant -1 as well as combined application of calcium chloride (0.7 g/l) and B. amyloliquefacians (600 ml/1.5 ×10 8 CFU) significantly reduced disease severity under in vivo condition. Thus, the present study identified successful management strategies for the fungal pathogens of dragon fruit through proper employment of bioagents, chemicals, fungicides and their combinations. These findings contributed valuable insights for the development of an economical and environment-friendly strategy against the dragon fruit diseases prevailing in southern Kerala.Item Management of fungal diseases of capsicum (capsicum annuum L.) under protected cultivation(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2017) Deepa Pawar; Sainamole Kurian, PItem Characterisation of phytopathogenic fungi in nursery seedlings of Tectona grandis L.F, Swietenia macrophylla King and Cassia fistula L. In Central Kerala(Department of Forest Management and Utilisation, College of Forestry, Vellanikkara, 2017) Kiran Mohan; Gopakumar, S