Browsing by Author "Rajagopalan, B"

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Field evaluation of fungicides against Diplodia dry rot of guava fruits
(Kerala Agricultural University, 1972) Rajagopalan, B; Wilson, K I
Fungicidal control of fruit rot of chilli caused by colletotrichum capsici (Syd.) Butl. & Bisby
(Kerala Agricultural University, 1992) Sulochana, K K; Rajagopalan, B; Wilson, K I
Inhibitory effects of certain plant extracts on the incidence of cowpea mosaic
(Department of Plant Pathology, College of Agriculture, Vellayani, 1990) Mallika Devi, S; Rajagopalan, B
The inhibitory effect of certain plant extracts on the incidence of cowpea mosaic was studied. Preliminary screening of non-host plants for antiviral property against cowpea mosaic virus revealed that extracts of sixteen plants viz. Adenocalyma allicea, Azadirachta indica, Boerhaavia diffusa, Bougainvillea spectabilis, Calotropis gigantean, Clerodendron inflortunatum, Curcuma longa, Eupatorium odoratum, Ferrula indica, Mirabilis jalapa, Moringa Olifera, Phyllanthus niruri, Polyalthia longifolia, solanum indicum, Thespesia populnea and Vitex negundo inhibited the production of local lesions on the leaves of Chenopodium amaranticolor indicating that these extracts possessed antiviral property. The extracts of A. Indica, B. diffusa, B. spectabilis, C. gigantean, C. infortunatum, C. longa, M. jalapa, P. niruri, S. indicum, and V. negundo caused 100 per cent inhibition of the production of local lesions on C. amaranticolor even at five per cent concentration. The inhibitory effect of the plant extracts was found to be less pronounced when tested on the primary leaves of cowpea seedlings. Pre - inoculation application of plant extracts was found to be more effective than post-inoculation application in checking the incidence of cowpea mosaic. In insect transmission studies with Aphis craccivora cent per cent inhibition of disease incidence was obtained with the extracts of A. indicum, C. infortunatum, P. niruri and V. negundo. Studies on the effect of plant extracts on the acquisition and transmission of cowpea mosaic virus by A. craccivora revealed that the extract of P. niruri caused 100 per cent reduction over control. Maximum inhibition of disease development was obtained in plants inoculated with cowpea mosaic virus upto two days after the application of extracts of A. indica, P. niruri, V. negundo and C. infortunatum. Extracts of V. negundo and A. indica caused considerable reduction in the survival of A. craccivora on cowpea. The present studies indicated that, the extract of C. infortunatum had some systemic effect against cowpea mosaic virus. Repeated application of plant extracts on cowpea plants revealed that V. negundo had the maximum inhibitory effect on symptom development, in both sap and insect transmission trials. Height and weight of plants, number and weight of pods and root nodules of cowpea plants treated with plant extracts were found to be more than that of the control.
Investigations on mosaic disease of bitter gourd
(Department of Plant Pathology, College of Agriculture, Vellayani, 1994) Purushothaman, S M; Rajagopalan, B
Bitter gourd mosaic virus disease commonly occurring in Kerala was investigated. The symptoms appeared as typical mosaic mottling with dark green and light green patches. Diseased plants were severely stunted and produced only a few flowers and fruits. Transmission studies showed that the virus could be transmitted through mechanical means, grafting and by aphid vectors. The virus was found to be transmitted by the aphids aphis gossypii Glov., Aphis malvae Koch., Myzus persicae Sclz. And aphis craccivora Koch. Among the four species of aphids, A. gossypii and A. malvae were found to be the most efficient vectors. Investigations on the physical properties of the virus revealed that the virus had a thermal inactivation point between 50 and 600C, dilution end point between 1:1000 and 1:10000, longevity in vitro between 12 and 24 h at room temperature (28 - 300C) and 48 and 72 h at 100c. The minimum acquisition feeding and inoculation feeding period of the vector A. malvae were found to be 30s and I min respectively. But the percentage of transmission was maximum when an acquisition feeding period of 30 min and inoculation feeding period of 2 h were given. Influence of starvation before acquisition and inoculation feeding period proved that pre – acquisition starvation for 2 h produced maximum infection but post- acquisition starvation decreased the per cent infection. The vector could retain the virus for I h only. A single aphid could transmit the virus to healthy test plants, but maximum percentage of transmission was obtained with 10 aphids. Host range studies showed that the virus was restricted to the members of the family Araceae, Chenopodiaceae, Cucurbitaceae, Musaceae, Polygonaceae and Solanaceae. Datura metal acted as a symptomless carrier of bitter gourd mosaic virus. Serological studies showed that bitter gourd mosaic virus is related to cucumber mosaic virus, pumpkin mosaic virus and snake gourd mosaic virus. Varietal screening showed that all the varieties and collections were susceptible to biter gourd mosaic virus infection, but the variety Arka Harit and the collections 87 green long 1 C 68234, 61 white medium 1C 45358 and 177 green medium 1C 68324 were least susceptible. Studies on estimation of loss revealed that early infection of bitter gourd plants by the virus significantly reduced the number of leaves, leaf area, intermodal length, thickness of vines, length of vines, number of branches, number of flowers, number of fruits and other fruit characters viz., length of fruits, girth of fruits, weight of fruits and total yield of fruits.
Purification and immunodetection of banana bract mosaic virus
(Department of Plant Pathology, College of Agriculture, Vellayani, 2004) Dhanya, M K; Rajagopalan, B
The study entitled “Purification and immunodetection of banana bract mosaic virus” was conducted in College of Agriculture, Vellayani, Thiruvananthapuram during 2000-2003. Survey conducted in Thiruvananthapuram district revealed that banana bract mosaic virus (BBrMV) is widely prevalent in different taluks of the district. Zero to 100 per cent variation was observed for disease incidence and per cent disease index was significantly different between taluks. The disease was found to increase with progress of time. Studies on varietal reaction revealed that none of the commonly cultivated varieties were resistant to BBrMV. Symptomatological studies showed that the characteristics symptoms of banana bract mosaic disease were longitudinal irregular reddish streaks on pseudostem, chlorosis of leaves, necrotic streaks on petiole and bract, travellers’ palm appearance, severe reduction in bunch size and formation of malformed fingers. Mechanical transmission of BBrMV through different means, graft transmission and soil transmission were unsuccessful. The aphid Pentalonia nigronervosa Coq. was identified as efficient vector of BBrMV (40 per cent transmission) with pre-acquisition fasting of one hour and acquisition threshold of 30 minutes. Carbohydrate content was less in BBrMV infected plants compared to healthy at all stages of analysis except at bract stage. The phenol content was more in infected banana plants at six months after planting and flag leaf stage whereas it was higher in healthy plants at three months after planting and at bract stage. Content of OD-phenol, protein, activity of peroxidase, polyphenol oxidase and phenylalanine ammonialyase were found to be more in banana bract mosaic virus infected plants. Electrophoretic analysis of BBrMV infected samples through SDS-PAGE revealed the presence of three extra bands (of virus) with molecular weight of 31, 32 and 39 kDa. Electrophoretic analysis of isozymes through native gel revealed the production of peroxidase isozyme in infected plants and the over expression of polyphenol oxidase isozyme in plants infected with BBrMV. Bioassay of endogenous growth regulators showed that the content of auxin, cytokinin and gibberlic acid was less in BBrMV infected fruits compared to healthy. The virus, BBrMV was purified from infected young leaf and the antiserum was developed in New Zealand white rabbit by giving intramuscular injection of partially purified virus. Titre of antiserum was tested using DAC-ELISA and it was determined as 1 : 1024. Electron microscopic studies of infected plant sample revealed that the virus particles were long flexuous rods with an average size of 725 x 12 nm. Detection of BBrMV infected plant parts was done using various immunological techniques like chloroplast agglutination, microprecipitin, Ouchterlony’s agar gel double diffusion test, DAC-ELISA and dot immuno binding assay and all were found to be efficient for the detection of BBrMV. Germplasm collection at Banana Research Station, Kannara were screened for banana bract mosaic disease resistance and found that varieties with ‘A’ genome were found to be more susceptible to the disease compared to those with ‘B’ genome. Screening of varieties at Instructional Farm, Vellayani showed that all of the commonly cultivated varieties were susceptible to BBrMV. For the production of virus free planting material meristem culture technique was attempted using meristems of BBrMV infected suckers. Virus free nature of the developed plants was confirmed through DAC-ELISA and it was found that about 100 per cent plants developed through meristem culture were free of BBrMV. Based on the survey and screening of germplasm collection, it was concluded that strict phytosanitation and use of virus free planting materials, preferably meristem cultured plants will help to manage the disease to a great extent.
Transmission, physical properties and host range of brinjal mosaic virus
(Department of Plant Pathology, College of Agriculture, Vellayani, 1996) Surendran, M; Rajagopalan, B
Transmission, properties and hostrance of snake gourd mosaic virus
(Department of Plant Pathology, College of Agriculture, Vellayani, 1989) Raghunadhan, D; Rajagopalan, B
Snake gourd mosaic virus disease commonly occurring in Kerala was investigated. The symptoms appeared as typical mosaic mottling with dark green and light green patches. The leaves were much reduced in size, variously crinkled and deformed. Diseased plants were severely stunted and produced only a few flowers and fruits. Transmission studies showed that the virus could be transmitted through mechanical means, grafting and by aphid vectors. The virus was found to be transmitted by the aphids, Aphis gossypii Glov., Aphis malvae Koch. and Aphis craccivora Koch. Among the three species of aphids, A. gossypii was found to be the most efficient vector. Investigations on the physical properties of the virus revealed that the virus had a thermal inactivation point between 70-750C, Dilution end point between 1:10000-1:50000, longevity in vitro between 96-120 h at room temperature (28-300C), and between 144-168 h at 100C. The minimum acquisition feeding and inoculation feeding period were found to be 30 s and 1 min respectively. But the percentage of transmission was maximum when an acquisition feeding of 20 min and inoculation feeding of 1 h were given. Influence of starvation before acquisition and inoculation feeding proved that pre-acquisition starvation for 1 h produced maximum infection but post-acquisition starvation decreased the per cent infection. The vector was found to retain the virus for 1 ½ h. A single aphid could transmit the virus to healthy test plants, but maximum percentage of transmission was obtained with 10 aphids. Host range studies showed that the virus was restricted to the members of the family chenopodiaceae, compositae, cucurbitaceae and solanaceae. Serological studies showed that snake gourd mosaic virus is related to cucumber mosaic virus and pumpkin mosaic virus. Varietal screening trial with seven varieties of snake gourd revealed that all the varieties were susceptible to snake gourd mosaic virus infection. Studies on estimation of loss revealed that early infection reduced significantly the length of vine, number of leaves, number of flowers, number of fruits and yield, whereas late infection did not produce significant effect, on both the varieties tested. There was significant reduction on leaf area and internodal length on plants inoculated at all stages of growth.
Variability in f4 generation of irradiated interspecific hybrids in okra (Abelmoschus esculentus (L.J Moench)
(Kerala Agricultural University, 2000) Anu Mary C Philip; Manju, P; Rajagopalan, B
Variability in f4 generation of irradiated interspecific hybrids in okra (Abelmoschus esculentus (L.J moench)
(Kerala Agricultural University, 2000) Anu Mary C Philip; Manju, P; Rajagopalan, B