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ThesisItem Open Access EXPLORATION OF SOME ECO-FRIENDLY TOOLS FOR THE MANAGEMENT OF BACTERIAL WILT OF TOMATO(2023) Bora, Vercity; Nath, Bharat ChandraTomato (Solanum lycopersicum L.) is one of the most important horticultural crops belonging to the family solanaceae. In tomato, bacterial wilt caused by Ralstonia solanacearum is one of the most dreadful diseases. This pathogenic bacterium causes wilt disease in more than 200 plant species by invading the xylem vasculature and causing death. Due to various environmental hazards caused by chemocentric management, we need to shift to eco-friendly cultivation. This present study is aimed at exploring some eco-friendly tools for the management of bacterial wilt of tomato. For the study, R. solanacearum was isolated and identified based on cultural, morphological, and molecular characterization as well as pathogenicity test in the susceptible tomato variety Pusa Ruby. In vitro efficacy of nine essential oils, four organic amendments and three organic formulations were tested against R. solanacearum by disc diffusion method to check the efficacy. Among the essential oils, the highest suppression of R. solanacearum was exhibited by T7 (thyme oil: 72.67%) in 0.14% concentrations followed by T2 (clove oil: 69.56%). T2 (oyster spent mushroom compost) had the highest percent inhibition of 64.67% at 35% concentration followed by T1 (karanj cake: 58.00%) in the case of organic amendments. Among the organic formulations, highest per cent inhibition was shown by T1 (panchagavya: 58.22%) followed by T2 (jivamrit: 50.22%) at 10% concentration. In in vivo pot culture assay, highest per cent bacterial wilt reduction was recorded in T3 (thyme oil: 13.33%) followed by T1 (clove oil: 20.00%). Whereas among the organic amendments and organic formulations, highest per cent bacterial wilt reduction was recorded in T2 (oyster spent mushroom compost: 22.22%); T3 (Karanj cake: 22.22%). Among the essential oils, highest yield was observed in in T3 (Thyme oil: 208 g/plant) followed by T1 (Clove oil: 186 g/plant). Whereas among the organic amendments and organic fomulations, highest yield was observed in T2 (Oyster spent mushroom compost: 198 g/plant) followed by T3 (Karanj cake: 173.67 g/plant). Among the essential oils, at 48 hours post application, the plants which were treated with Thyme oil (T3: 145.07 n mol cinnamic acid/min/g tissue, 0.780 u unit/g fresh tissue, 0.895 u unit/g fresh tissue) showed high enzyme concentration (PAL, PPO and POD) followed by Clove oil (T1: 134.78 n mol cinnamic acid/min/g tissue, 0.721 u unit/g fresh tissue, 0.769 u unit/g fresh tissue). Whereas among the organic amendments and organic formulations, in case of PAL, at 48 hours post application, the plants which were treated with Karanj cake (T3:142.01 n mol cinnamic acid/min/g tissue) showed high enzyme concentration followed by Oyster spent mushroom compost (T2: 126.94 n mol cinnamic acid/min/g tissue). In case of PPO, at 48 hours post application, the plants which were treated with Panchagavya (T5: 0.592 u unit/g fresh tissue) showed high enzyme concentration followed by Jivamrit (T1: 0.576 u unit/g fresh tissue). In case of POD, at 48 hours post application, the plants which were treated with Oyster spent mushroom compost (T2: 0.667 u unit/g fresh tissue) showed high enzyme concentration followed by Panchagavya (T5: 0.660 u unit/g fresh tissue). Further in case of application of essential oil, there was no significant changes in the nutrient status of soil. But application of organic amendments and organic formulations, significantly increased nitrogen, phosphorus and potassium content in the soil. In case of organic amendments and organic formulations, Oyster spent mushroom compost (T2: 359 kg/ha) significantly increased nitrogen content in soil followed by Rice straw biochar (T4: 299 kg/ha). In the case of phosphorus, the highest increase in phosphorus content was shown by soil treated with Panchagavya (T5: 11.13 kg/ha) followed by Oyster spent mushroom compost (T2: 10.48 kg/ha). In the case of potassium, the soil treated with Jivamrit (T1: 198.44 kg/ha) had the highest potassium content followed by Karanj cake (T3: 198.28 kg/ha).ThesisItem Open Access GREEN SYNTHESIS OF ZINC OXIDE NANOPARTICLES AGAINST BACTERIAL WILT OF TOMATO CAUSED BY “Ralstonia solanacearum”(2023) Swaroop, V. Shiva Sai; Pranjal Kr KamanRalstonia solanacearum, a major bacterial pathogen, is known to cause bacterial wilt disease in over 200 plant species (50 families) throughout the world, but is particularly devastating in the Solanaceae family. A recent survey was conducted by 458 bacterial pathologists worldwide to vote on the top ten most important pathogenic bacteria in terms of their scientific and economic importance and amongst them, R. solanacearum obtained second place in the list .The current methods of control include host crop rotation, biological soil disinfestations, and cultural practices. But these measures provide limited ability to prevent its spread .Nanotechnology is a research hot spot in modern science.this technology is capable of providing miscelaneous ways to exploit some beneficial properties of metal oxide nano particles like Anti bacterial property against pathogens and there ability to induce Nano particle Triggered systemic resistance (NTR) in plants against biotic stress by triggering the expression of defence genes in the plant cell .The aim of this work was to evaluate these two properties of nano particles. ZnO NPs were Synthesized from various Biological sources like Curcuma longa, Jatropa curcass, Pipper nigrum, Trichoderma viride, Trichoderma harzianum, Bacillus subtilis against Ralstonia solanacearum. Among which ZnO NPs from curcuma longa have shown best anti bacterial activity and the average size of curcuma longa ZnONPs was found to be 18 .5 nm and curcuma longa ZnONPs have shown 78% inhibition and 100 % inhibition at 90 and 120 ppm respectively in in vitro. Seed priming was done with both the concentrations to check the expression of PR1, PR5 and PAL genes.Final Analysis showed the Up regulated expression of all the genes under biotic stress. The Nano particle treated plants @ 90 ppm and 120 ppm have shown 22% and 30 % disease reduction respectively compared to control which showed 80% disease incidence when challenged with pathogen. These results indicate that ZnO NPs induces Systemic resistance in Tomato plants against wilt pathogen.ThesisItem Open Access Bacillus spp. AS A POTENTIAL BIOAGENT AGAINST MAJOR POSTHARVEST PATHOGENS OF KHASI MANDARIN, Citrus reticulata, Blanco(2023) Taye, Trishna; Bora, PopyKhasi Mandarin Citrus reticulata Blanco, which belongs to the Rutaceae family holds a significant importance as a horticultural crop and it occupied second most important fruit crops after banana. The present study aims to the identification of major postharvest pathogens of Khasi Mandarin (Citrus reticulata, Blanco) and evaluation of promising Bacillus spp. against major postharvest pathogens and assessment of bioagent-induced qualitative changes in citrus fruits. The isolated pathogen was identified as Penicillium sp. and Aspergillus sp. based on their cultural and morphological characteristics. Four Bacillus spp. were screened with both the pathogen and results showed that all the biocontrol agents were significantly inhibit the mycelial growth of the pathogens. B. subtilis LB22 were showed highest per cent mycelial growth inhibition of Penicillium sp. and Aspergillus sp. with 74.60% and 86.20%, respectively. SEM (Scanning Electron Microscopy) analysis of B. subtilis and pathogens interaction shows disintegration in fungal morphology. GC-MS analysis of B. subtilis LB22 found the presence of nine different antimicrobial compounds such as 2, 4-di-tert-butylphenol, n-hexadecanoic acid, 1H-Indene, 1-hexadecyl-2, 3-dihydro, etc. B subtilis cell suspension and cell free culture filtrate could significantly control the disease occurrence in Khasi Mandarin fruits with a 100% biocontrol efficiency, as compared with control and B. subtilis cell suspension, cell free culture filtrate with co-inoculation of pathogens. Peel and pulp were observed under SEM micrograph where colonization of Bacillus subtilis cells can be seen in the treated peel when compared with the untreated sample. The microphotograph of the pulp shows there is no bacterial colonization both in treated and untreated samples. The fruits treated with B. subtilis cell suspension show TSS of 11.90ºB and Titratable acidity of 0.85% as compared to the control after 15 days of storage which was non-significant. An Organoleptic test was carried out for untreated and treated samples concerning colour, flavour, texture, taste and overall acceptability.ThesisItem Open Access FIELD EVALUATION OF NEW GENERATION FUNGICIDES AGAINST LATE BLIGHT OF POTATO(2023) Borah, Swapnil; Saikia, Mitul KumarPotato (Solanum tuberosum L.) is the most commonly cultivated tuber crop and fourth most important food crop in the world, after wheat, rice and maize. Among the various factors limiting the yield of the crop, Late blight of potato caused by oomycetous fungus Phytophthora infestans (Mont.) de Bary, is of major concern all over the world causing yield loss to a range of 20-75 %. For more than a decade, management of late blight has become increasingly demanding because of its aggressive appearance and emergence of resistance in new strains of the pathogen against fungicide. In the present investigation, efforts have been made to evaluate the efficacy of kresoxim methyl, azoxystrobin, propamocarb and dimethomorph against late blight of potato under different spray schedule and to evaluate the phytotoxic effects of these new generation fungicides on potato crop, if any under different spray schedule. Results of the present investigation revealed that, all the spray schedule of fungicides were significantly effective in suppressing late blight over untreated control. Among the different treatment combinations, one prophylactic spray with chlorothalonil @ 0.25 % followed by two sprays of propamocarb @ 0.2 % and one spray of chlorothalonil @ 0.25 % in alternate application at 10 days interval proved to be the best treatment combination economically resulting in a yield of 14.73 t/ha. This treatment not only recorded the highest benefit-cost ratio of 2.74:1 but also provided significantly better control of foliar late blight (84.29 %) and tuber infection (0.59 %) in field condition. However, highest disease reduction (98.20 %) was achieved by application of one prophylactic spray with chlorothalonil @ 0.25 % followed by three sprays of dimethomorph @ 0.2 % and two sprays of chlorothalonil @ 0.25 % in alternate application at 10 days interval. This treatment also recorded the minimum disease incidence (29.33 %) and disease intensity (1.78 %) under field condition. The experiment on evaluating the phytotoxic effect of kresoxim methyl, azoxystrobin, propamocarb and dimethomorph at rates two or even three times higher than the normal recommended dose of the fungicide indicated that these four fungicides had not shown any phytotoxicity on potato crop in terms of necrosis, chlorosis and leaf epinasty.ThesisItem Open Access Effect of Trichoderma spp. in response to application of nanoparticles for management of Rhizoctonia disease of Black Gram(2023) Sau, Suprakash; Kaman, Pranjal KrAn experiment was conducted to test the compatibility of nanoparticles with three different Trichoderma spp. namely Trichoderma viridae, Trichoderma harzianum, Trichoderma pseudokoningii at five different concentrations 200 ppm,400 ppm,600 ppm,800 ppm and 1000 ppm. Results revealed that out of three Trichoderma spp, T.harzianum was found to be compatible with ZnO NPs @ 200ppm where we observed maximum mycelail growth inhibition of 10.25% . Web blight caused by Rhizoctonia sp. was isolated from infected black gram plant which was collected from Instructional Cum Research Farm , AAU, Jorhat. Cultural, morphological and molecular identification revealed that the isolated was found to be Rhizoctonia solani. In vitro efficacy of , T. harzianum compatible with ZnO NPs showed mycelia growth inhibition of 73.91%.However highest inhibition percentage of 88.47% was observed in chemical treatment hexzconazole @0.1% In vivo assessment was made to find out the effect of T. harzianum supplemented with ZnO NPs @ 200ppm on disease incidence, severity, plant growth parameters, yield and yield attributing characters. Disease incidence was found to be in the range of (76.37 to 90.25 per cent) and disease severity was observed in the range of 87.53 to 95.12 .Highest plant growth parameters was like shoot length (35.79 Cm), root length (20.90Cm), fresh shoot weight(44.78g), fresh root weight (1.78g) , dry weight of shoot (4.30g) and dry weight of root (0.66g) was observed when soil and foliar application of T. harzianum supplemented with ZnO NPs @ 200ppm was done as compared to control. Highest yield and yield attributing characters like number of branches per plant (15.67), number of pods per plant (25.77), pod length (7.18 cm), yield per plant (9.59q/ha ) , and weight of 100 seed (4.38g) observed when soil and foliar application of T. harzianum supplemented with ZnO NPs @ 200ppm was done as compared to control. From present study, it can be concluded that the severity of web blight of black gram can significantly reduced along with increase in yield by the use of bioagent T. harzianum supplemented with ZnO NPs @ 200ppm by soil and foliar application @ 5gm/plant and 5ml/litr.ThesisItem Open Access EPIDEMIOLOGY AND INTEGRATED MANAGEMENT OF CUCUMBER MOSAIC VIRUS DISEASE OF PUMPKIN(2023) Shobnur, Shahin; Kalita, Manoj KumarPumpkin (Cucurbita moschata Duch.) belongs to the family Cucurbitaceae, is one of the important vegetable crops grown in India and abroad. Production of pumpkin is limited by a number of biotic and abiotic factors, among which cucumber mosaic virus disease caused by Cucumber Mosaic Virus (CMV) has become a major threat in its cultivation. Considering the importance of the disease, experiment was carried out to study the epidemiology and integrated management of cucumber mosaic virus disease of pumpkin in Assam in the experimental field of Department of Plant Pathology, BNCA, AAU during 2022-23 with 2 objectives, viz., (i) To study the effect of dates of sowing on incidence of cucumber mosaic virus disease of pumpkin and its aphid vector. (ii) Integrated Management of cucumber mosaic virus disease of pumpkin. In the six dates of sowing, highest (100%) disease incidence was observed in the crop sown on 18.10.22 (D4), 02.11.22 (D5) and 17.11.22 (D6) and lowest disease incidence (50.00) was recorded in the first date of sowing 3.09.22 (D1). Correlation studies revealed a positive significant relationbetween the disease incidence and aphid vector population in all the six dates of sowing and also with bright sunshine hour and diurnal variation on crop sown on 3.09.22 (D1) and 18.09.22 (D2). Disease incidence had significant negative correlation with maximum temperature, minimum temperature, day temperature and night temperature on the crop sown on 3.09.22(D1),18.09.22(D2),3.10.22(D3) and 18.10.22(D4). The aphid population had negative significant correlation with maximum temperature, day temperature and night temperature during the first four dates of sowing D1, D2, D3 and D4, whereas minimum temperature had a negative significant correlation with aphid population during the first three dates of sowing D1(3.09.22), D2(18.09.22) andD3(3.10.22). The disease incidence could be predicted up to 93-97 per cent accurately with aphid population only in different dates of sowing. Sowing time of pumpkin also affected the yield parameters of the crop. highest fruit yield was obtained in D2(18.09.22). Out of eighteen pumpkin cultivars evaluated against cucumber mosaic virus disease, six were moderately susceptible, eleven were susceptible and one cultivar was observed to be highly resistant against the disease. Among the eleven treatments evaluated for management of the disease, treatment T10 consisting of two rows of maize as barrier crop + seed treatment with HCl (2%, 10min) + foliar spray of Imidacloprid 17.8 SL @2.0ml/10L at 30 DAS + spray with bioagent (Beauveria bassiana) @ 1% at 45 DAS + spray with neem oil (3ml/l) at 60 DAS has resulted in least disease incidence (16.67%) and fruit yield of 83.89q/ha. Treatment T10 also resulted in highest benefit: cost ratio of 2.53.ThesisItem Open Access Induced resistance against the viral disease complex of King Chilli using biotic and synthetic agents(2023) Baruah, Preetam; Nath, PhuleswarKing Chilli is one of the important traditional spice crops with high export value, grown in North Eastern region of India. Studies revealed that viral diseases in this crop are widespread, with prevalence of viral infections as complex viral symptoms. The study on different biotic and synthetic agents for the management of viral complex in open cultivated King Chilli was carried out in experimental farm, Department of Horticulture, AAU. The treatment combinations were POP + Biopesticide (Biogreen) @ 50g/L + Biofertilizer (Azotobacter) @ 80g/L, POP + Jivamrit @ 5%, POP + Salicylic acid @ 0.5mM, POP + Vitex negundo (Posotiya plant) @ 5%, POP + King chilli fruit extract 1ppm, POP and untreated control. Treatments were applied following proper application methods and viral disease incidence was recorded at 0th, 15th, 30th, 45th, 60th, 75th, 90th, 105th and 120th days after transplanting in the main field based on symptomatology and molecular detection of healthy plants. The mean value of disease percentage indicated that, expression of symptoms was heavier at 120th days after transplanting in all the treatments. The results of this investigation when subjected to descriptive statistical analysis viz. ANOVA, PCA-Biplot, AUDPC, Correlation indicated that most effective treatment was POP + Salicylic acid @ 0.5mM which caused significant reduction in percentage of viral infection (16.67%) followed by POP + Biopesticide (Biogreen) @ 50g/L + Biofertilizer (Azotobacter) @ 80g/L (19.44%). Although none of the treatments were completely effective in management of mixed virus infection, but all the treatments were effective in comparison to un-treated control. Amongst the growth parameters the maximum plant height at 120th days after transplanting was 94.08 cm recorded in treatment with POP + Salicylic acid @ 0.5mM and the highest yield of King Chilli was recorded to be 88.4 q/ha at 120th days after transplanting in the plot where POP + Salicylic acid @0.5mM was applied. Further, the virus infected leaf samples of King Chilli based on visual symptoms were collected from experimental plot, Dept of Horticulture, AAU. CMV, ChiVMV, TSWV and ChiLCV were successfully detected in the infected leaf samples of King Chilli by Reverse Transcription PCR (RT-PCR) and PCR using coat protein (CP) gene specific primers with a product length of 290 bp, 1026 bp, 302 bp and 218 bp respectively. The phylogenetic analysis was drawn between the isolated sequences in which viruses share common homology with other isolates of India as well as around the world.ThesisItem Open Access Management of Post Harvest Diseases of Banana with Essential Oils(2023) Barua, Prateeti; Bora, BudhaBanana (Musa spp.) is a tropical and subtropical crop. Banana has originated in South East Asia. It belongs to the family Musaceae. Fruits are a good source of potassium (358 mg/100g), carbohydrate, and vitamin B. India is the world’s largest producer of bananas. It accounts for 13% of the total area and 33% production of fruits. Upto 30-40% losses occur due to post harvest diseases. These post-harvest diseases are anthracnose, crown rot, and finger tip rot of banana. These post-harvest diseases are commonly managed by chemical fungicides whose long term application may result in resistance, residue, environmental and health hazards. Natural plant products (i.e., essential oils) as an eco- friendly alternative are gaining popularity and drawing the attention of researchers globally owing to their biodegradable, economical, and eco-friendly. In the present investigation in vitro and in vivo evaluation of essential oils against the major disease was carried out. Mature green fruits were collected from three markets in Biswanath Chariali and kept in lab condition for symptom development. Two major post-harvest diseases viz., anthracnose and crown rot were observed. The causal organism of anthracnose disease was confirmed to be Colletotrichum musae and causal organism of crown rot was confirmed to be Fusarium spp. and Verticillium spp. based on morphological, cultural, colony characteristics and by following standard reference books. Out of which anthracnose was found to be most damaging. Six essential oils viz., clove, cinnamon, neem, sesame, basil, and peppermint oils were evaluated against C. musae in vitro and in vivo at 0.1%, 0.5%, 1.0%, and 1.5%. Clove and cinnamon oil treated culture plates were found most efficient in inhibiting mycelial growth (100.00%). Followed by basil oil (86.00%) and peppermint oil (76.85%). The best concentration of respective essential oils was used for in vivo treatment. Lowest disease incidence (33.33%) and disease severity (29.98%) were recorded in clove oil treated fruits. After in vivo treatment, the clove and cinnamon oil treated fruit increased the shelf life of bananas by 3 days over control followed by basil (1.0%) and peppermint oil (1.0%) treated fruits with 2 days increment of shelf life over control. Physiological weight loss of fruits treated with cinnamon oil recorded the lowest (9.52%) physiological weight loss followed by clove oil (9.92%), respectively. The physicochemical qualities of bananas viz. colour, total soluble solids, titratable acids, peel: pulp ratio, dry matter, pulp: peel ratio, reducing sugar, and total sugar were greatly influenced by the application of essential oils. The fruits treated with clove and cinnamon oil retained better colour in comparison to the control which was closely followed by basil and peppermint oil treated fruits. The effect of essential oils on the results of TSS, TA, TA: TA ratio, and dry matter were found to be statistically non-significant. highest pulp: peel (2.57) ratio was observed in clove oil (0.1 %) treated fruits. The highest reducing sugar (8.03 %) and total sugar (8.34 %) were observed in cinnamon oil (0.1 %) treated fruits respectively. Essential oils can be used for managing post-harvest disease management in bananas. Further research can be developed to study the effects of essential oils on biotic phytopathogens and on improved delivery system of essential oils to manage post-harvest diseases.ThesisItem Open Access STUDY ON INCIDENCE AND MANAGEMENT OF ANTHRACNOSE DISEASE OF BOTTLE GOURD(2023) DEY, JYOTISHMOI; Mazumder, NirmalBottle gourd [Lagenaria siceraria (Mol.) Standl.] is one of the important cucurbitaceous vegetable crops which belong to the family Cucurbitaceae. It is a popular crop, cultivated almost in all the Indian states with a total production of 2.86 MT covering an area of 1.58 M ha. Assam recorded a total production of about 55.16 MT (NHB, 2021-22). It is nutritionally rich, having a cooling effect with diuretic and cardio-tonic properties, also useful in the prevention of constipation. Like other crops, bottle gourd is sensitive to various biotic (different types of pathogens like fungus, bacteria and viruses) and abiotic stresses that limit their production. Among commonly occurring diseases, the prevalent of anthracnose is common with the highest disease index in Assam. Anthracnose may cause about 90 per cent yield loss of marketable fruits. In the present investigation, survey on disease incidence and symptomatological study was carried out. Based on cultural, morphological (Scanning Electron Microscope, SEM) and molecular studies the causal pathogen was identified as Colletotrichum lagenarium. In vitro efficacy of different botanicals, biocontrol agents and chemicals against C. lagenarium was done. Among the three botanicals (viz., Polyalthia longifolia, Allium sativum and Azadirachta indica) (@10%) against C. lagenarium, using the Poisoned Food Technique revealed A. sativum was effective with the highest mycelial growth inhibition (100%). Similarly, among the three biocontrol agents viz., Trichoderma viride, T. harzianum and Pseudomonas fluorescens against C. lagenarium using dual culture technique, the combination of T. viride and P. fluorescens recorded highest(82.22%) mycelial growth inhibition. Efficacy of five fungicides viz., Propiconazole (0.1%), Thiophanate methyl (0.1%), Carbendazim (0.1%), Copper oxychloride (0.1%) and Mancozeb (0.25%), alone and in combination against C. lagenarium revealed that Thiophanate methyl (0.1%) could restrict the mycelial growth completely (100%). The best treatments obtained under in vitro condition were further evaluated under in vivo conditions in farmer’s field. Under in vivo condition, Thiophanate methyl (0.1%) significantly recorded the lowest PDI (12.67%) with highest PDR (84.42%). The treatment combination [Biogreen-L (@5ml/l) + A. sativum (10%) + Thiophanate Methyl (0.1%)] was found to be second best with 17.33 and 78.68 per cent PDI and PDR respectively. Although the foliar application of fungicide was observed to be effective in reducing the disease, its application alone should preferably be avoided because chemical control measures are not only uneconomical but also potentially hazardous for ecological and environmental health.
