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ThesisItem Open Access STUDY ON INTEGRATED MANAGEMENT OF THE VIRAL DISEASE COMPLEX IN BHUT JOLOKIA (Capsicum chinense Jacq.)(2021) Khaidem, Princy; Kalita, Manoj KumarBhut (Capsicum chinense Jacq.) is one of the important spice crops which is mainly cultivated in the Northeastern region of India. Owing to its traditional importance, pharmaceutical applications, and high commercial value, Bhut Jolokiais getting importance but the production of the crop has been hindering attributable particularly due the infection of a number of viruses. With the growing need for proper management approaches for managing the viruses infecting the crop, a number of management strategies have been studied in the present investigations to manage the viral diseases in Bhut Jolokia. Hot water treatment was given to CMV-infected Bhut Jolokia seeds under different temperature regimes and periods. Thermotherapy was observed to be highly significant in reducing the virus infectivity. Bhut jolokia seeds treated at 50°C for 120 minutes was observed to be the best treatment with minimum disease incidence (26.08%), followed by 55°C for 60 minutes and 55°C for 120 minutes. It was recorded that the virus infectivity gradually reduced at higher temperature with longer exposure period, but, the germination rate was declined. The effect of SAR activating chemicals viz., Salicylic acid (SA), a key signalling molecule triggering plant resistance, and Benzothiadiazole (BTH), an analogue of SA were tested on CMV-infected Bhut Jolokiaseeds to see their effect in the disease incidence. Foliar application of Salicylic acid and Benzothiadiazole at three different concentrations @200, 300 and 400 ppm each was tested where BTH @ 400ppm and SA @ 300 and 400ppm were recorded to be the best among all the treatments displaying less severe symptoms with 55.56 per cent disease reduction over control. Field study was conducted to evaluate the integrated effect of management practices like nursery net cover of seedlings, Benzothiadiazole @ 300 ppm with Biometa @ 5% and neem oil @ 5ml/L; Salicylic acid @ 300 ppm with Biometa @ 5% and neem oil @ 5ml/L; Biometa @ 5% and neem oil @ 5ml/L; Biometa @ 5% and Nuvan @ 1ml/L and sticky traps in different treatment combinations in the management of the viral disease infecting Bhut Jolokia. The plants were observed to be naturally infected by CMV and PVY, ChLCV forming a viral disease complex. DAS-ELISA, RT-PCR, and PCR were used for molecular detection of the viruses. The infected plants exhibited a wide range of symptoms such as severe mosaic, filiform, curling, and crinkling of leaves with a reduction in size, stunted plant growth with bushy appearance, fewer flowers, and deformed fruits were exhibited at later stages of plant growth. Incidence of the viral disease complex of CMV, PVY, and ChLCV ranged from 20.80 to 47.23 percent different treatments. The treatment combination T1 with Net cover of seedlings + Sticky trap +Benzothiadiazole @ 300 ppm at 2-3 leaf stage at 3 days interval for 3 times + Bio-Meta @ 5% at 60, 90 and 120 DAT+ Foliar spray with neem oil @5ml/L at 10 days interval from 30 DAG for 5 times was found to be the most effective treatment by delaying the number of days to the first appearance of symptoms with the lowest disease incidence of 20.80 per cent, maximum yield of 3.22 kg/4.5 m2, and highest benefit-cost ratio of 8.56:1.ThesisItem Open Access Organic management of Pest and Diseases in Potato(2021) Patowary, Debarshi; Saikia, M. K.In the present investigation, efforts have been made to evaluate the comparative efficacy of two different forms of copper fungicides viz., copper oxychloride and copper hydroxide against late blight of potato incited by Phytophthora infestans (Mont.) de Bary under the different spray schedule (10 numbers of sprays at 4 days interval and 8 numbers of sprays at 5 days interval) with a view to select the most effective one for management of the disease. Field experiment performed revealed that both the fungicides could control late blight to a varying extent. Among the fungicides, copper hydroxide proved to be the best in reducing late blight severity. The fungicide could provide highest protection (73.74%) to moderately late blight resistant variety (Kufri Himalini) and 47.23% protection to the susceptible variety (Kufri Jyoti) when applied 10 numbers spray of copper hydroxide @0.2% at 4 days interval. This treatment gave maximum tuber yield 15.73 and 10.26 t/ha in K. Himalini and K. Jyoti respectively. Although maximum net return Rs. 54,200 with a corresponding incremental benefit-cost ratio of 2.25 was recorded in this treatment (10 numbers spray with copper hydroxide @0.2% at 4 days interval) but at the same rate of application the highest B:C ratio (2.41) obtained in the treatment of copper oxy-chloride with a net return of Rs. 43,500. An another study on comparative efficacy of four microbial bioformulations viz., Biometa, Biosona, Biollium and Biogreen against Red ant (Dorylus orientalis Westwood) on potato was evaluated during 2018-2019 and 2019-2020. The formulation, Biosona (combined tuber treatment @6g/kg tuber and soil application with enriched compost @ 2 t/ha) gave highest tuber yield of 11.23 t/ha with a minimum nfestation rate of 15.71% tuber damage and maximum protection (47.02%) against red ant and also gave a satisfactory profit of Rs. 19,700 with a B:C ratio of 1.48. The third investigation was carried out during 2018-2019 and 2019-2020 to evaluate the comparative efficacy of four microbial bio-formulations viz., Biometa, Biosona, Biolium and Biogreen against Aphid (Myzus persicae and Aphis gossypii) on potato. Biolium (Verticilium lecani) @0.5% spray gave highest tuber yield of 10.27 t/ha with a highest protection 33-66 % against aphid. This treatment gave a satisfactory profit of Rs. 10,400 with a B:C ratio of 1.44.ThesisItem Open Access MICROBE BASED MANAGEMENT OF CITRUS CANKER DISEASE vis a vis PREVAILING WEED FLORA(AAU, Jorhat, 2021) Bokotial, Pinkumoni; Nath, Bharat Ch.Citrus canker disease as well the weed flora of citrus grove decrease the quality and quantity of the citrus fruit. An eco-friendly approach for management of Citrus canker disease vis a vis prevailing weed flora was attempted using bioactive microorganisms, Pseudomonas fluorescens and weed pathogens. In the assessment of weed composition, two weeds, Alternanthera philoxeroides and Commelina benghalensis were found to have highest population density of 83% and 25% in the field condition with visible disease symptoms. From the cultural and morphological study of these two isolates, they showed their similarity with Nimbya alternantherae and Colletotrichum siamense. The molecular characterization of these microorganisms was made to determine their distinctiveness from their close relatives through sequencing of ITS region of ribosomal DNA.Interactive action of these two weed pathogen with P. fluorescens resulted in the partial compatibility of P. fluorescens with Nimbya alternantherae and incompatibility reaction in all other possible treatment combinations in vitro. The antagonistic potential of these compatible microbes was tested in vitro singly or in combination and per cent inhibition of target pathogen, Xanthomonas citri pv. citri were recorded and analyzed. Highest inhibition (30.00 %) of X. citri pv. citri was recorded against P. fluorescens and N. alternantherae followed by P. fluorescens (18.52%) in vitro. In the field study, highest citrus canker disease reduction (21.85%) was recorded in the treatment of P. fluorescens followed by treatment comprising of P. fluorescens and N. alternantherae (14.61%). In case of management of Alternantherae philoxeroides weed in field condition, highest percent disease increase (77.49% in manual analysis and 69.98% in AI analysis) was recorded against treatment of N. alternantherae followed by treatment comprising of P. fluorescens and N. alternantherae (41.63% in manual analysis and 45.95% in AI analysis). Correlation studies revealed positive linear relationship between manually and AI analysed data.ThesisItem Open Access IDENTIFICATION, CHARACTERIZATION AND MANAGEMENT OF PUMPKIN MOSAIC DISEASE(AAU, Jorhat, 2021) Gogoi, Kulumanali; Mishra, RanimaThe present investigation was conducted for identification, characterization and management of pumpkin mosaic disease in Assam. A roving survey was conducted during 2019-2021 in Jorhat, Golaghat, Karbi Anglong, Biswanath Chariali and Charaideo to determine the disease incidence through symptomatology, vector population count and detection of the viruses associated with mosaic disease of pumpkin through serodiagnostic (DAS-ELISA) and molecular assay (PCR and RT-PCR). Symptomatology revealed various degrees of mosaic, mottling, vein clearing, vein banding, chlorosis, leaf distortion, small, crinkled, deformed leaves and malformed fruits with mosaic and chlorotic spots resulting in reduced yield and production. Serological detection through DAS-ELISA confirmed the association of Cucumber mosaic virus (CMV) in CMV suspected pumpkin samples. The DAS-ELISA assay revealed disease incidence of 52.38 per cent in Golaghat district and 35.71 per cent in Jorhat district. Two different types of aphid vectors viz., Aphis gossypii and Myzus persicae were observed in all the surveyed locations. Total genomic RNA extracted from symptomatic and asymptomatic pumpkin plants were subjected to RT-PCR assays using CMV, zucchini yellow mosaic virus (ZYMV) and watermelon mosaic virus (WMV) specific primers and Deng universal primer for detection of begomovirus viz., pumpkin yellow vein mosaic virus (PYVMV). RT-PCR assay revealed the presence of CMV in the samples which yielded the desired amplicon size of 593 bp. No amplification was obtained from the samples for ZYMV and WMV. PCR product of CMV infected sample from Jorhat district viz., CMV-CP Jorhat isolate was sequenced and compared with the known CMV isolates worldwide using nucleotide BLAST programme at National Centre for Bio Informatics (NCBI) and Mega X software. The sequence similarity of CMV-CP Jorhat isolate ranged from 93.11 per cent to 99.16 per cent with worldwide CMV isolates. A field experiment was conducted for management of pumpkin mosaic disease through integrated approach. It was evident from the field experiment that there was low disease incidence with low vector population as well as high yield in the treatments of hot water seed treatment at 50⁰C for 10 minutes and spraying of neem formulation @3ml/lit at 15, 30, 45 and 60 days after transplanting (T1) followed by hot water seed treatment at 50⁰C for 10 minutes and spraying of Imidacloprid @2ml/lit at 15, 30, 45 and 60 days after transplanting (T6) than the other treatments with the highest yield (80.00 q/ha) recorded for the treatment T1 with highest per cent reduction of disease over control (53.22 per cent).ThesisItem Open Access IDENTIFICATION AND CHARACTERIZATION OF BACTERIAL PATHOGENS IN MEDICINAL, AROMATIC AND SPICE PLANTS OF ASSAM(AAU, Jorhat, 2022) GOGOI, MOUSUMI; Borah, P KAccumulated knowledge of medicinal, aromatic and spice plants from ancient times helps to improve human health and life from generation to generation. There is tremendous scope for the extensive development of these important plants. But different diseases cause considerable loss of these plants that result in substantial economic loss to farmers. Although bacterial diseases cause severe loss to different medicinal, aromatic and spice plants in different states of our country, not much work had been done on bacterial diseases of these crops in Assam including other Northeastern states. Therefore, the present study was made to isolate, characterize and identify some of the bacterial pathogens associated with diseases of medicinal, aromatic and spice plants in Assam. Disease samples from medicinal, aromatic and spice plants viz., Chilli (Capsicum annum), Ginger (Zingiber officinale), Coriander (Coriandrum sativum), Betelvine (Piper betle), Pennywort (Centella asiatica), Giloy (Tinospora cordifolia) and Cardamom (Elettaria cardamomum) were collected from Golaghat, Jorhat, Karbi Anglong and Nagaon district of Assam. On the basis of cultural, morphological and biochemical studies the seven bacterial isolates were identified as genus Xanthomonas (in Chilli, Coriander, Betelvine and Giloy), Pantoea (in Pennywort), Bacillus (in Ginger) and Pseudomonas (in Cardamom). Further molecular characterization and phylogenetic analysis were done to identify the different bacterial isolates i.e., isolate MGH1 GOLAGHAT as Xanthomonas axonopodis pv. vesicatoria (bacterial leaf spot of chilli), isolate MGH2 GOLAGHAT as Bacillus pumilus (rhizome rot of ginger), isolate MGH3 JORHAT as Xanthomonas campestris pv. coriandri (bacterial leaf spot of coriander), isolate MGH4 GOLAGHAT as Xanthomonas axonopodis (bacterial leaf spot of betelvine), isolate MGH5 JORHAT as Pantoea ananatis (bacterial leaf spot of pennywort), isolate MGH6 JORHAT as Xanthomonas campestris (bacterial leaf spot of giloy) and isolate MGH7 JORHAT as Pseudomonas oryzihabitans (bacterial blight of cardamom).ThesisItem Open Access EVALUATION OF CITRUS CULTIVARS/GERMPLASMS OF ASSAM AGAINST CITRUS CANKER DISEASE(AAU, Jorhat, 2021) Kaushik, Snata; Nath, Bharat Ch.Evaluation of different citrus cultivars/germplasms against citrus canker disease in artificially inoculated conditions and their assessment for defense-related secondary metabolites, viz., total phenol, flavonoid, alkaloid content was attempted in the present study. For artificial inoculation, bacterial pathogen associated with diseased citrus canker leaf was isolated, purified, and further confirmed as Xanthomonas citri pv. citri by conducting morphological, cultural, gram staining, specific biochemical tests, and molecular characterization. Altogether thirty cultivars/ germplasms were tested for their degree of resistance against citrus canker (X citri pv. citri). All these cultivars/ germplasms showed significant differences in terms of percent disease severity and disease reaction. Out of thirty, eight cultivars/germplasms namely Jora tenga (14.67%), Bonjora (15.58%), Holong tenga (15.75%), Patijora (17.75%), Birajora (18.50%), Cleopatra mandarin (20.00%), Latipes (17.34%) and Ada jamir (20.18%) exhibited resistance response (R). Moderate degree of susceptibility (MS) was observed in fourteen cultivars/germplasms viz., Trifoliate orange (25.63%), Troyer citrange (26.87%), Rubidoux (30.37%), NRCC6 (36.58%), Bhutan orange (31.06%), Galgal (38.42%), Sopai (39.70%), Rangpur lime (43.30%), Soh bitara (30.27%) Sohmyndong (46.57%), Pummelo-1(31.34%), Pummelo-2 (28.38%), Pummelo-3(38.48%), Pummelo- 7(43.31%). Seven cultivars/germplasms namely Nainty jambhiri (52.56%), Australian orange (56.32%), Rough lemon (57.54%), Volkameriana (60.34%), White pummelo (61.64%), Acid lime (62.48%) and Grape fruit (70.63%) were categorized as susceptible types (S) while Assam lemon showed the highest degree of susceptibility (HS) against citrus cankerwith 78.14% disease severity. Further study on secondary metabolites revealed that total phenol, flavonoid, alkaloid content in citrus leaves differed greatly based on the cultivars/germplasms. The highest total phenol content (TPC) was found in one of the resistant germplasm Latipes (21.26 mg/g dry weight), while the lowest was recorded in susceptible cultivar Grapefruit (7.85 mg/g dry weight). Another resistant germplasm Jora tenga (6.47 mg/g dry weight) had the highest flavonoid content and the lowest was found in susceptible germplasm White pummelo (1.89 mg/g dry weight). Similarly, the highest alkaloid percentage was found in resistant germplasm Adajamir (10.52%) and the lowest was recorded in susceptible germplasm Volkameriana (2.30%). From the correlation analysis, three negative correlation coefficient was obtained viz.,P(rxy)= -0.861 for total phenol content, F(rxy)= -0.836 for flavonoid content and A(rxy)= -0.802 for alkaloid content.ThesisItem Open Access CULTURAL, MORPHOLOGICAL AND MOLECULAR VARIABILITY AMONG ISOLATES OF Rhizoctonia solani CAUSING WEB BLIGHT OF GREEN GRAM (Vigna radiata (L.) WILCZEK)(AAU, Jorhat, 2021) Mohana, Pradeep R K; Sharma, SupriyaWeb blight of green gram is one of the major constraints which incur huge losses and hold back the production of green gram in Assam. A comprehensive study was made during 2020-21 on the variability of Rhizoctonia solani isolates based on morpho- cultural characteristics and molecular variation. Web blight infected plants were collected from different geographical locations was designated as SH-1, SH-2, AAU-1, TT-1, and MJ- 1 and identified based on a typical character with right angle branching near the distal septum of the young vegetative hyphae. A high virulence pattern for all the isolates was recorded based on pre-emergence seedling rot and complete leaf blighting appearance within 48 hours of inoculation in susceptible cultivar (SGC-16). All the five isolates showed variation in morpho-cultural characteristics such as colony growth diameter, colony texture, concentric rings on radial growth, colony color, growth pattern, hyphal width, distribution pattern of sclerotia, sclerotial initiation, maturation, color, aggregation, exudate droplets on sclerotial surface, position of sclerotia and sclerotia on lid, sclerotial diameter, number and weight in different growth media Potato Dextrose Agar (PDA), Rose Bengal Agar (RBA), Richard’s Agar (RA), Czapeck’s Dox Agar (CDA) and Sabouraud Dextrose Agar (SDA) where most of the isolates were categorized into three and four groups based on hyphal width and sclerotial initiation respectively. The size, number, and weight of sclerotia were highly variable across different isolates concerning media. They are arranged in the central, central- peripheral, sub-central, sub-central peripheral, peripheral and scattered manner on the petri- dish with respect to media. Among different media, Sabouraud Dextrose Agar medium (85.85%) is the best growth media to study morpho-cultural variability with quantitative variables like sclerotial maturation and initiation which directly correlated with virulence of our R. solani isolates based on principal component analysis. There is no evidence of molecular variability among our isolates from different geographical locations of Assam.ThesisItem Open Access MOLECULAR SCREENING OF CITRUS GERMPLASM FOR SIMULTANEOUS DETECTION OF Candidatus Liberibacter species ASSOCIATED WITH CITRUS GREENING DISEASE(AAU, Jorhat, 2020-08) Paul, Amitha; Nath, P.D.An effort was made to screen the Citrus germplasm maintained at the Citrus Research station (CRS), Tinsukia, Assam to identify the prevalence of Ca. Liberibacter species associated with citrus greening disease (CGD) and to understand the differential reaction of various varieties to CGD. Overall, 32 germplasm were screened comprising 16 species, 1 hybrid and 1 unidentified cultivar. The severity of CGD based on symptomatology showed that; major parts of the germplasm were infected with CGD. The conventional PCR assay with two pairs of primers of these varieties showed that, only three (3) varieties namely; Khasi Papeda, Trifoliate Orange and Citrange are free from CGD infection. The presence of Citrus Psyllid insects in symptomatic trees, further amplification of its DNA with the specific primer confirmed the probability of vector mediated the spread of CGD in the field. Further differentiations of Asian and African strains by PCR and RFLP assays confirmed the absence of African strains. Similarly, comparative quantification of infected (10 samples) and suspected healthy (3 varieties) were done by Real time PCR to differentiate the known Ca. Liberibacter species in a singleplex reaction. The assay confirmed that the suspected healthy accessions were resistant and the others were infected with only Ca. Liberibacter asiaticus. The sequence similarity and evolutionary divergence analysis of the CGD isolates under current study showed sequence similarity with the „Ca. L. asiaticus‟ isolates (Asian-common isolates) from Southeast Asia, rather than the other diverse atypical Indian isolates present in the rest part of the country.
