Browsing by Author "Saha, D."

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    Begomovirus causing leaf curl disease in tomato (Lycopersicon esculentum L.) in sub-Himalayan West Bengal, India
    (University of North Bengal, 2013-03) Saha, B.; Saha, D.; Saha, A.
    Tomato (Lycopersicon esculentum L.) is an extensively cultivated vegetable crop in India. In the year 2009, a survey was conducted to find leaf curls of tomato in different locations of sub-Himalayan West Bengal, India. During the survey a severe leaf curl disease was observed. The characteristic disease symptoms (puckered leaves) and presence of whitefly (Bemisia tabaci) population indicated the possibility of begomovirus infection. Total DNA was extracted from the infected samples and PCR was carried out using begomovirus specific primers. An amplicon of expected size ( ̴1280 bp) was found when PALIc1960 and PARIv722 were used as primers in agarose gel electrophoresis. The PCR Amplicons of two samples (collected from two different places of present study area) were cloned and sequenced (GenBank accession nos. HM856626 and HM856627). The sequence data analysis of partial coat protein gene (AV1), full replication enhancer protein gene (AC3) and partial transcription activator protein gene (AC2) of 831 nt revealed highest 98% similarities with several isolates of Tobacco curly shoot virus (TBCSV) at both nucleotide and amino acid levels. The phylogenetic analysis also showed close relationship of the present isolates with different variants of TbCSV. Based on highest sequence similarities and closest relationships with TbCSV the viruses (present in infected tomato plants) were considered as Begomovirus. Transmission of the virus in tomato could not be done by sap transmission procedure. In experimental insect transmission tests, test plants showed symptoms very much like the natural symptoms. Artificial transmission was confirmed by comparing the PCR Amplicons raised from the experimentally infected plants.
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    Immunotechniques: Concept and application in plant pathology
    (University of North Bengal, 2007-03) Saha, A.; Dasgupta, S.; Saha, D.
    Proper management of plant diseases requires accurate disease diagnosis and precise identification of the phytopathogens involved. Traditional and conventional methods of disease diagnosis and pathogen detection have several demerits. It takes a lot of time to diagnose a disease and to identify a pathogen accurately by traditional approaches. Moreover, results are not always conclusive because similar symptoms can be caused by different pathogens or physiological conditions and sometimes it is very difficult to distinguish closely related organisms on the basis of their morphological characters only. Thus the traditional methods normally applied for pathogen identification and disease diagnosis are less sensitive and less reliable. The need for rapid and accurate identification and diagnostic methods to identify the organisms that cause plant diseases are essential for the formulation of effective disease control strategies.
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    Influence of culture media and environmental factors on mycelial growth, sporulation and spore germination behaviour of Curvularia eragrostidis (P. Hennings) Mayer
    (University of North Bengal, 2008-03) Saha, A.; Dasgupta, S.; Mandal, P.; Saha, D.
    Curvularia eragrostidis is a foliar fungal pathogen of young tea plants. It causes leaf spot disease of tea. Mycelial growth, sporulation and spore germination behaviour of the pathogen were studied. Six different media were tested for mycelial growth. Among these, potato carrot agar (PCA) was found best for the mycelial growth and sporulation. Maximum mycelial growth was attained after 15 days of incubation. Mycelial growth was also studied in different temperatures and pH. Optimum temperature of growth was 25 °C and best growth was obtained at pH 6.0. Glucose and peptone were best carbon and nitrogen sources respectively for growth and sporulation of the fungus. The optimum conditions of spore germination were found to be at pH 7.25 and at incubation temperature of 25 °C. Keywords: Sporulation; Curvularia eragrostidis; Mycelial growth, fungus
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    Isolation and identification of a virulent Ralstonia solanacearum by fliC gene amplification and induction of chitinase by 2-amino butyric acid for control of bacterial wilt in tomato plants
    (University of North Bengal, 2013-03) Saha, A.; Mandal, H.; Saha, D.
    Ralstonia solanacearum is a devastating, soil borne bacterial pathogen of tomato. The pathogen is nonmotile in planta but highly motile in culture. On the basis of physiological and biochemical characteristics 26 isolates have been purified and identified as Ralstonia solanacearum. The flic gene is responsible for the movement of bacteria. Ralstonia specific fliC gene amplification is the indication of virulence of the pathogen. In the present study one R. solanacearum isolate has been identified by PCR amplification of the fliC gene using fliC gene specific primer. Following isolation and identification of the virulent isolate, fresh tomato plants were induced by application of 2- amino butyric acid (ABA). The defense enzyme, chitinase was estimated in treated plants. Treated inoculated plants did not show any visible symptoms of wilt even after 14 days of inoculation. Significantly it was observed that chitinase was increased in the 2-ABA-treated plants and also in the treated-inoculated plants. The increased chitinase activity in the treated plants showed that 2-ABA has the resistance inducing capacity in tomato plants against Ralstonia solanacearum.
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    Prevalence of begomoviruses associated with tomato leaf curl disease in the sub-Himalayan plains of West Bengal
    (University of North Bengal, 2016-03) Karmakar, A.; Chakraborty, P.; Sarkar, T.; Das, S.; Saha, A.; Saha, D.; Saha, A.
    Tomato is a solanaceous crop and one of the most economically important vegetables in the world. India ranks second in total production of tomato in the world. It has been referred to as a “functional food”, a food that goes beyond providing just basic nutrient. To LCD is one of the major constraints to tomato production in India. To study the disease incidence of tomato, a survey was made in the tomato crop growing fields of Darjeeling, Jalpaiguri, Coochbehar and Uttar Dinajpur districts of sub-Himalayan West Bengal during December 2015 to February 2016 and several infected and healthy leaf samples were collected based on the morphological symptoms like-vein cleaning, leaf curling, leaf deformations and stunted growth of plants. Disease incidence ranged from 70% to 86.66% of the collected samples from different districts. All the samples collected from the present study area were tested by PCR with DengA and DengB primer and expected amplicon of ̴ 530bp was found. Two randomly selected PCR positive samples were sequence and analyzed (Acc. Nos KX108859 and KX108860). The SLG-1 isolate (Acc. No. KX108859) showed 95 % nt identity with ToLCKV (Acc. No. KP178730) and the ISL-1 isolate (Acc. No. KX108860) showed 96% nt identity with ToLCNDV (Acc. No. KC513822). The threat of begomoviral spread to the north-eastern part of India has been taken into consideration.