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Assam Agricultural University, Jorhat

Assam Agricultural University is the first institution of its kind in the whole of North-Eastern Region of India. The main goal of this institution is to produce globally competitive human resources in farm sectorand to carry out research in both conventional and frontier areas for production optimization as well as to disseminate the generated technologies as public good for benefitting the food growers/produces and traders involved in the sector while emphasizing on sustainability, equity and overall food security at household level. Genesis of AAU - The embryo of the agricultural research in the state of Assam was formed as early as 1897 with the establishment of the Upper Shillong Experimental Farm (now in Meghalaya) just after about a decade of creation of the agricultural department in 1882. However, the seeds of agricultural research in today’s Assam were sown in the dawn of the twentieth century with the establishment of two Rice Experimental Stations, one at Karimganj in Barak valley in 1913 and the other at Titabor in Brahmaputra valley in 1923. Subsequent to these research stations, a number of research stations were established to conduct research on important crops, more specifically, jute, pulses, oilseeds etc. The Assam Agricultural University was established on April 1, 1969 under The Assam Agricultural University Act, 1968’ with the mandate of imparting farm education, conduct research in agriculture and allied sciences and to effectively disseminate technologies so generated. Before establishment of the University, there were altogether 17 research schemes/projects in the state under the Department of Agriculture. By July 1973, all the research projects and 10 experimental farms were transferred by the Government of Assam to the AAU which already inherited the College of Agriculture and its farm at Barbheta, Jorhat and College of Veterinary Sciences at Khanapara, Guwahati. Subsequently, College of Community Science at Jorhat (1969), College of Fisheries at Raha (1988), Biswanath College of Agriculture at Biswanath Chariali (1988) and Lakhimpur College of Veterinary Science at Joyhing, North Lakhimpur (1988) were established. Presently, the University has three more colleges under its jurisdiction, viz., Sarat Chandra Singha College of Agriculture, Chapar, College of Horticulture, Nalbari & College of Sericulture, Titabar. Similarly, few more regional research stations at Shillongani, Diphu, Gossaigaon, Lakhimpur; and commodity research stations at Kahikuchi, Buralikson, Tinsukia, Kharua, Burnihat and Mandira were added to generate location and crop specific agricultural production packages.

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  • ThesisItemOpen Access
    EFFECT OF COLOUR ON ATTENTION AND MEMORY OF YOUNG CHILDREN
    (AAU, Jorhat, 2015-07) Dutta, Ankita; Baruah, Juri
    Most of the child psychologists pay greater attention to the pre-school age because it is the time when children undergo the greatest development. Learning in this period is critical to their subsequent development throughout their lives. Coloured presentation of information is considered by many studies as an important and stimulating cue for learning in children. Colour has the potential to increase the chances of environmental stimuli to be encoded, stored and retrieved successfully. With this background the present study entitled, “Effect of colour on attention and memory of young children” was undertaken in Jorhat district during 2014-2016 with the objectives: 1. To analyze the frequently used colours in existing instructional materials of young children. 2. Preparation of instructional materials using different colours. 3. To identify the colours which facilitate attention and memory of young children. 4. To develop guidelines for using colours in instructional materials of children. A total of 30 children aged 4 to 5 years, with average intelligence level and without any chronic illness, signs of inattention and impulsivity were selected for the study. The sample was selected from 180 respondents from six preschools of Jorhat district. Data was collected from the respondents using a questionnaire and a tool with subtests Prose Memory and Test Card to assess the health status of the respondents and identify the colours which facilitate attention and memory of young children respectively. Culture Fair Intelligence Test was also used to screen out the children with average intelligence. The books of four preschools were analyzed to find out the frequently used colours in existing instructional materials of young children. Upon completion of data collection, the results indicated that the most frequently used colour in the existing preschool books is yellow, followed by red, green, blue, light blue, natural, black brown, purple, pink, orange and lastly grey. The results of the responses to colours in the Prose Memory sub-test reveal that natural colour may facilitate most attention and memory in young children, followed by red, green, blue, light blue, yellow and black. Test Card results also reveal that natural colour may facilitate most attention and memory in young children, but followed by red, green, yellow, blue, light blue and black. Females responded more to colours of red and yellow than male respondents. And males responded more to green, blue, light blue and natural colours than females. There was no gender difference in response to black colour. On the basis of the findings of the study, few guidelines were recommended in the area of use of colour in instructional material for children.
  • ThesisItemOpen Access
    FARM LEVEL PRODUCTION TECHNOLOGIES, POST HARVEST LOSSES AND MARKETING EFFICIENCY OF MAJOR VEGETABLES: A STUDY IN THE DARRANG DISTRICT OF ASSAM
    (AAU, Jorhat, 2015-07) Dutta, Sumi; Barman, R. N.
    Vegetables are important supplements to the human diet. India ranks 2nd after China in the world with total production of 162.19 million tones. In Assam area under vegetable is about 2.73 lakh hectares with annual production of 49.79 lakh MT.Vegetables are highly perishable food products in nature and in the process of supply from the farm level to the market level. The seasonal gluts and lack of infrastructure and marketing facilities in the developing countries have significant effect on the extent of post harvest losses of vegetables. In Assam not much information is available regarding the farm level adoption of production technologies and quantum of post harvest loss of vegetables at various stages of marketing and its impact on marketing efficiency. The present study was conducted in the Darrang district of Assam and was designed to collect information regarding the level of production technologies, assessment of productivity, technology gaps of some major vegetables, physical and value loss at farm level and at various stages of marketing and to examine the impact of post harvest loss on farmer’s net price, marketing costs, margins and efficiency of major vegetables. The study was based on both primary and secondary data. Bechimari and Kharupetia two major vegetable growing areas were identified.Both tabular and functional analysis was done in analyzing data. Cost concepts used in farm management studies were applied to calculate costs in the present study and results indicated that cost of production increased with increase in size of the farm and regardingknowledge on different parameters of vegetable production it was observed that almost all farmers (99.33%) had the knowledge about the ploughing and application of organic manures (99.00%).The extent of adoption gaps for selected vegetables is estimated and 7 technology components were found. More than 30 percent of technology adoption gaps were observed in terms of technology components T4, T5 and T6 i.e. Manuring and fertilization, Number of irrigations applied & Intercultural and weed control.As vegetables are perishable in nature so during the process of distribution and marketing substantial losses are incurred. The post harvest loss was estimated first at farm level and then at market level and in case of market level it can be clearly observed that the physical loss was highest in itinerant level followed by wholesaler and retailer level. 4 major marketing channels of vegetables were identified namely Channel I:Producer–Consumer,Channel II:Producer–Retailer–Consumer,ChannelIII:Producer–Wholesaler–Retailer-Consumer,ChannelIV:Producer–Itineranttraders–Wholesaler-Retailer-Consumer. Marketing efficiency was estimated in different marketing channels and it was found that Channel II was the most efficient channel and Channel IV was the least efficient channel.ButChannel IV was considered as the most effective one because farmers sold majority of their marketed surplus through Channel IV.
  • ThesisItemOpen Access
    MOLECULR DIVERSITY AMONG Salmonella ISOLATES FROM MAN AND ANIMALS WITH SPECIAL REFERENCE TO NON-HOST SPECIFIC SEROVARS
    (Assam Agricultural University, Khanapara, Guwahati, 2015-07) GOGOI, PURNIMA; Borah, Probodh
    Salmonellae are important food-borne pathogens responsible for diseases in animals and man. It is an important zoonotic pathogen and a leading cause of many outbreaks and infections around the globe. It is a major cause of human gastroenteritis worldwide. The present study was undertaken with a view to isolate Salmonella from various sources including animals, birds and human, to study their virulence gene profiles based on an multiplex PCR assay developed for the purpose and to compare three molecular typing methods, viz. rep-PCR, PFGE and plasmid profiling for their efficacy to discriminate and subtype Salmonella isolates belonging to different serovars. Out of a total of 332 samples from various sources examined, 10 (3.01%) were found to be positive for Salmonella. The isolates belonged to three different serovars, Salmonella Enteritidis being the most predominant (40%), isolated from cattle, pig and Human. The other serovars recovered were Weltevreden (30%) and Newport (10%), while the remaining isolates were untypable (20%). A multiplex PCR assay was developed for rapid detection of nine important virulence genes of Salmonella, viz. sipA, sipB, sipC, stn, sefC, spvA, spvB, spvC and sopB. Isolates belonging to different serovars showed variable results in respect of possession of different virulence genes. The virulence genes sipA, sipB, sipC, stn and sopB were detected in all (100%) the Salmonella isolates under the present study, while the sefC gene was present in only 34 (45.94%) of the 74 isolates. The rest three virulence genes spvA, spvB, and spvC were found to be present in 24 (32.43%) isolates. Most of the isolates (17) carrying all the nine genes under the study were recovered from poultry. On application and analysis of three molecular typing methods, viz. rep-PCR, PFGE, plasmid profiling, it was found that PFGE could clearly differentiate among the strains belonging to different serovars and rep-PCR could differentiate between strains belonging to different serovars as well as between strains within the same serovar, while plasmid profiling had comparatively lower discriminatory power. On the basis of the findings of the present study, it could be suggested that a combination of PFGE and rep-PCR would prove to be more useful and appropriate for molecular typing of Salmonella isolates during epidemiological investigations.
  • ThesisItemOpen Access
    EVALUATION OF EFFICACY OF WHOLE OUTER MEMBRANE PROTEIN OF Salmonella Typhimurium ADJUVANTED WITH CALCIUM PHOSPHATE NANOPARTICLES AS VACCINE CANDIDATE AGAINST SALMONELLOSIS IN CHICKEN
    (Assam Agricultural University, Khanapara, Guwahati, 2015-06) DEKA, SURAKSHA SUBEDI; Sarma, Satya
    Salmonella sp can infect a broad array of animals, causing diseases ranging from gastroenteritis to life threatening systemic infections. Substantial economic loss is manifested through mortality and poor growth of infected birds. Salmonella enterica serovar Typhimurium is the most frequently isolated serovar causing global food-borne outbreaks and chicken alone accounts for 10.4% of the total isolates. The control of salmonellosis can be accomplished either by vaccination or medication. Antibiotic resistance and issue of antibiotic residue is a major hurdle in medication. Thus control through immunization is the most efficient and economic method. The present study was conducted to study the efficacy of whole outer membrane protein adjuvanted with calcium phosphate nanoparticles (CAP-OMP) as vaccine candidate against salmonellosis in chicken. The study was carried out in Kamrupa birds which are dual purpose breed. The OMP was extracted from Salmonella Typhimurium (MTCC - 98) strain and confirmed by SDS-PAGE. CAP-OMP vaccine was then synthesized by method that is based on co-precipitation of calcium phosphate and OMP. The amount of protein entrapped in the complex was determined and the formulation was used to immunise the chicks on 14th day of life followed by booster dose after two weeks. The humoral immune response of the target vaccine was compared with aluminium hydroxide adjuvanted OMP and unadjuvanted OMP by indirect ELISA. Blood was collected from all the birds at 0 before vaccination and days 7, 14, 21, 28, 35 45 and 60 after booster vaccination. Some of the birds from each group were challenged on 60th day with either S. Typhimurium or with S. Gallinarum. The humoral response of the unchallenged birds was studied from 60th to 90th day. The CAP-OMP vaccine was able to elicit significantly higher antibody titres compared to other two groups up to 60th day post booster vaccination. However antibody titre level fell thereafter in all the groups. Mortality was not observed in any of the challenged birds but some clinical symptoms were exhibited by the control group. The challenged birds were slaughtered after one week and total CFU of either S. Typhimurium or S. Gallinarum per gram of liver was determined. It was observed that none of the vaccines gave total protection against challenge organisms but the Salmonella isolates recovered from the birds immunized with target vaccine was significantly lower than that of control group. The other two formulations viz; aluminium hydroxide –OMP vaccine and unadjuvanted OMP vaccine also decreased the bacterial count in liver tissue. Some important serum biochemical parameters were also studied from the vaccinated birds and it was found that the total protein and globulin content was significantly higher in CAP-OMP vaccinated group than the control groups. Creatine kinase level was significantly higher during first 21 days post booster vaccination birds given Aluminium hydroxide -OMP indicating some tissue damage at the site of injection caused by Aluminium hydroxide. Other parameters like alkaline phosphatase and creatinine showed non-significant fluctuations throughout the experiment. From this study, it can be concluded that CAP-OMP (S.Typhimurium) vaccine can be an effective vaccine candidate against salmonellosis.
  • ThesisItemOpen Access
    PREVALENCE, PATHOLOGY AND MOLECULAR STUDIES OF PESTE DES PETITS RUMINANTS IN GOATS OF ASSAM
    (Assam Agricultural University, Khanapara, Guwahati, 2015-07) ISLAM, MUZAHARUL; Pathak, D. C.
    Peste des petits ruminants is an acute, febrile, emerging and economically important viral disease of goats having high morbidity and mortality rate. In the present investigation, 456 serum samples collected from affected and apparently healthy goats from different places of Assam were screened for seroprevalence of PPR in goats by HI test and c ELISA test. Out of 456 serum samples screened, PPR viral antibody could be detected in 269 samples by HI test (145 serum samples from affected goats and 124 from apparently healthy goats) and 209 samples by c ELISA test (136 from affected goats and 73 from apparently healthy goats). 60 serum samples (9 from affected goats and 51 from apparently healthy goats) showed positive in HI test but were found negative by c ELISA test. In comparative study it was revealed that HI test was more sensitive than c ELISA. The haematological study of 26 affected goats showed significant increase in total erythrocyte count, haemoglobin, packed cell volume and significant decrease in total leucocytes count. Lymphopenia was constant finding in differential leucocytes count. Biochemical study revealed significant decrease in serum protein and significant increase in serum potassium level, with nonsignificant increase of serum sodium level. All the 10 necropsied carcasses showed emaciation and dehydration with soiled hindquarters and sunken eye balls. Ulcerative lesions on gum, lips, dental pad and tongue, enteritis and linear haemorrhages on the crests of the folds of large intestine were invariably observed. The liver was enlarged with engorged gall bladder. Spleen and lymph nodes were enlarged. The lungs showed congestion and consolidation of anterior and cardiac lobes with emphysema in diaphragmatic lobes. On cut section, lung showed large quantities of white frothy exudate particularly in the bronchi. The histopathological study showed degeneration, necrosis, ulceration and sloughing off lining epithelium in lips, tongue, small intestine and large intestine. Below the ulcerated areas severe infiltration of mononuclear and polymorphonuclear cells were observed. Some cells of stratum granulosum showed presence of intracytoplasmic eosinophilic inclusion bodies. Hepatocytes showed coagulative necrosis with cytoplasmic and nuclear degeneration. The lungs showed broncho-interstitial pneumonia and presence of intracytoplasmic eosinophilic inclusion bodies. Renal tubular degeneration with coagulative necrosis and atrophy of glomeruli were observed. Edema in both the cortical and medullary areas with severe depletion lymphocytes was observed in the lymph node. Syncytial giant cells were also found in the lymph nodes. Spleen showed depletion of lymphoid population. Some lymphoid follicles were completely destroyed, leaving cystic cavities. In RT-PCR, out of 79 post mortem samples, 58 showed amplification of PPR viral nucleic acid at 463 bp for N gene using N gene specific primers.
  • ThesisItemOpen Access
    MOLECULAR CHARACTERIZATION OF FEW PLANT GROWTH PROMOTING MICROBES, THEIR COMPATIBILITY ANALYSIS AND UTILITY IN BIOINTENSIVE MANAGEMENT OF BACTERIAL WILT OF TOMATO
    (AAU, Jorhat, 2015) Nath, Bharat Chandra; Bora, L. C.
    Biointensive management of bacterial wilt of tomato (Lycopersicon esculentum Mill) caused by Ralstonia solanacearum was attempted using various bioactive (Plant Growth Promoting) microorganisms viz., Trichoderma viride, Pseudomonas fluorescens, Bacillus subtilis and Azotobacter chroococcum. The molecular characterization of these microorganisms was made to determine their distinctiveness from their close relatives through sequencing of ITS region of ribosomal DNA in case of fungal microorganisms and 16S region of ribosomal DNA in case of bacterial microorganisms. Interactive action among the four bioactive microorganisms showed compatibility in all the treatment combinations in vitro. The antagonistic potential of these bioactive microorganisms was tested in vitro singly or in consortia and per cent inhibition of target pathogen were recorded and analyzed. The highest inhibition (57.70%) against R. solanacearum was recorded against consortia of T. viride+ P. fluorescens + B. subtilis + A. chroococcum followed by T. viride + P. fluorescens + B. subtilis (39.77%) and P. fluorescens + B. subtilis + A. chroococcum (35.65%). Talc based bioformulations were prepared using the best three bioactive microorganisms and their consortia for management of bacterial wilt in pot grown tomato plants during 2013-14 and 2014-15 crop seasons. Applications of the consortial formulations were made as seed treatment, root treatment and soil application. Significantly highest reduction of bacterial wilt incidence (95.09 %) and highest yield (1.692 kg/plant) of tomato was recorded in treatment comprising of T. viride+ P. fluorescens + B. subtilis + A. chroococcum. Correlation studies revealed negative correlation (-0.993) between bacterial wilt incidence and yield of tomato. Screening of 47 tomato genotypes was done under field condition during 2012-13 and 2013-14 crop seasons to assess their degree of tolerance against bacterial wilt pathogen R. solanacearum. Highly resistance reaction (HR) was recorded in Konbilahi (L. pimpinellifolium) followed by resistance reaction (R) in Sel-35, sel-19 and Sel-9. Highest yield was recorded in 2012/TOLCVRES-3 (278.16 q/ha) followed by H-24 (276.85 q/ha) and 2012/TOLCVRES-4 (272.04 q/ha).
  • ThesisItemOpen Access
    Pest complex of French bean and Management of the major pests through Development and Validation of certain IPM modules
    (AAU, Jorhat, 2015-07) SHARMAH, DIGANTA; Rahman, S.
    The present investigation was carried out in the ICR farm, AAU, Jorhat-13 as well as in the Acarology laboratory, Department of Entomology, Assam Agricultural University, Jorhat during 2013-14 and 2014-15 to record pest complex of french bean with their incidence; management of the major pests through development and validation of certain IPM modules and to evaluate certain plant extract against aphid and two spotted spider mite (TSSM). Eight insect pests viz. cutworm, Agrotis ipsilon; aphid, Aphis craccivora; thrips, Scirtothrips dorsalis; pod borer, Helicoverpa armigera; white fly, Bemesia tabaci; leaf beetle, Menolepta signata; leaf miner, Liriomyza sativae; red ant, Dorylus orientalis and a mite pest i.e. two spotted spider mite, Tetranychus urticae were recorded. The incidence of aphid and cut worm was found to be maximum during the 51st Standard meteorological week (SMW) with 1.33 numbers per twig per plant and 1.0 number per plant, respectively. Highest population of TSSM and thrips were recorded during 52nd SMW i.e.1.23 and 0.97 number per leaf, respectively. The incidence of pod borer and whitefly was found to be maximum during the 51st SMW with 1.12 per plant and 52nd SMW with 1.23 numbers per leaf, respectively. The incidence of leaf beetle, leaf miner and red ant was found to be minor. Meteorological parameters had a significant impact on population build up of various French bean crop pests. Cutworm population had a positive and significant correlation with morning relative humidity. Aphid had a positive significant correlation with maximum temperature and BSSH but negative with relative humidity. TSSM population had a positively significant correlation with relative humidity and negatively with maximum temperature. Pod borer population showed a negative significant correlation with maximum temperature and positive correlation with relative humidity. Whitefly population showed a negative significant correlation with maximum temperature and positive correlation with relative humidity. Thrips had a negative significant correlation with rain fall. Significantly lesser per cent incidence of Aphid (0.60%) was seen in Module-I than Module-III (2.58%) and Module-II (6.0%). But highest percentage of aphid incidence (13.40%) was registered in Module-IV. The mean population of thrips varied from 1.0 to 10.0 per cent among the modules. Module-I was found to be superior by recording significantly less incidence of thrips (1.04%) than Module-III (2.6%) and Module -II (4.0%). Considerably higher per cent incidence of thrips was observed in Module-IV (10.0%). The per cent population of mite was least (1.0%) in Module-I compared to Module-III (3.0%) and Module -II (7.6%). However, maximum incidence of mites was recorded in Module -IV (9.0%). Whitefly incidence was recorded to be minimum (1.2% in Module -I compared to Module -III (2.80%) and Module -II (4.0%). While highest percent incidence of whitefly was registered in Module -IV (10.8%). The mean per cent population of pod borer varied from 0.40 to 8.40% among the different modules. Module-I was found to be superior by recording significantly less incidence of pod borer (0.40%) and was significantly differed from Module -III (3.2%) and Module-II (5.8%). The highest healthy green bean yield ha-1 was achieved in Module I (13.99t ha-1) followed by Module-III (13.91t ha-1), Module II (13.56t ha-1) and Module-IV (9.88t ha-1). The effectiveness of IPM Modules in respect to B:C ratio were obtained to be 2.06, 1.95 and 1.97 from Module –I, II and III respectively. Efficacy of seven plant extract viz. Polygonum hydropiper, Murraya koenigii, Jatropha curcas, Piper longum, Ocimum sanctum, Phlogacanthus thyrsiflorus and Pongamia pinnata were evaluated against aphid (A. craccivora) and TSSM (Tetranychus urticae) under both laboratory and field condition and all were found to be effective in reducing pests population as compared to control. LC50 were calculated for the different plant extracts and found that Piper longum (3.39% & 3.41%), Jatropha curcas (4.17% & 4.37%), Polygonum hydropiper (4.37% & 4.57%), Phlogacanthus thyrsiflorus (5.13% & 5.23%), Murraya koenigii (5.25% & 5.35%), Pongamia pinnata (5.25% & 5.37%) and Ocimum sanctum (5.62% & 5.66%) against the aphid and TSSM, respectively after 48 hrs. of exposure period. The highest per cent mortality of both aphid and TSSM were obtained in Piper longum (3%) 75.46% & 66.85% after 96 hrs. of exposure period followed by Jatropha curcas (4%) with 65.89 % & 58.89%, Polygonum hydropiper (4%) with 63.89% & 57.31%, Phlogacanthus thyrsiflorus (5%) with 60.19% & 51.02%, Murraya koenigii (5%) with 55.56% & 48.61%, Pongamia pinnata (5%) with 52.31% & 46.11% and Ocimum sanctum (6%) with 48.61% & 36.57%, respectively under laboratory condition. Under field condition highest per cent reduction of both aphid and TSSM were obtained in Piper longum (3%) with 84.38% & 63.41% after 7 days of treatment followed by Jatropha curcas (4%) with 73.53% & 52.50%, Polygonum hydropiper (4%) with 72.73% & 50%, Phlogacanthus thyrsiflorus (5%) with 60.0% & 44.74%, Murraya koenigii (5%) with 56.25% & 43.59%, Pongamia pinnata (5%) with 45.0% & 40% and Ocimum sanctum (6%) resulted 39.39% & 37.84%, respectively.
  • ThesisItemOpen Access
    STUDY OF DIFFERENTIAL GENE EXPRESSION IN RICE UNDER DROUGHT STRESS
    (AAU, Jorhat, 2015-07) Deka, Diganta; Modi, M. K.
    Rice is a dietary staple for a large part of the world’s human population which is grown under varying water regimes ranging from flooded to rainfed upland condition. The predominantly rice-growing areas in Asia are often threatened by severe abiotic stresses, the most common being drought which affects the yield potential of rice across all agro-climatic regions of the globe. Interestingly, some of the rice varieties of Northeast India are found to be drought tolerant e.g. Banglami. Comparative biochemical and physiological analyses of the variety with a high-yielding variety Luit confirmed this. Keeping all these points in view, high throughput RNA-Seq of the variety Banglami in presence and absence of drought was performed as an attempt to study the differential gene expression in Banglami. The RNA isolated by Trizol reagent (Invitrogen) was used for preparation of paired-end libraries using Illumina TruSeq RNA Library Preparation Kit. Libraries were sequenced using 2 X 150 PE chemistry on NextSeq. The reads were aligned against the indica reference assembly (ASM465v1). The expression analysis of the genes revealed 25,272 and 24,408 numbers of expressed genes in well watered control and drought stressed sample, respectively. Further analysis revealed 391 numbers of genes showing differential expression among which 86 were up-regulated and 305 were down-regulated. Among the differential expressed genes a number of genes were found to be very important for development of drought stress tolerant behaviour. Further, downstream analysis like Gene Ontology enrichment analysis, KEGG pathway analysis and QTL mapping were also performed which revealed important informations regarding the differentially expressed genes under drought stress condition in particular and the whole transcriptome of the Banglami variety of rice in general. The present study identified altered gene expression in rice induced by drought stress and provided a comprehensive map of drought responsive genes and pathways. Thus the results of the present investigation can serve as valuable genetic resource for gene expression, genomics and functional genomics studies in general and drought stress research in rice in particular.
  • ThesisItemOpen Access
    BIOLOGY AND MOLECULAR CHARACTERIZATION OF ROOT-KNOT NEMATODES OF ASSAM
    (AAU, Jorhat, 2015-08) Kshetrimayum, Sumita; Das, Debanand
    Investigations were carried out to find the molecular characterization of root-knot nematode of Assam, morphological and morphometric variations among the populations of root-knot nematode (s) of Assam and effect of temperature on the biology (embryogenesis, penetration and multiplication) of root-knot nematode, Meloidogyne incognita. PCR analysis using specific primer, MiF-MiR for M. incognita showed that all the populations of root-knot nematode collected from nine districts (Jorhat, Golaghat, Sibsagar, Lakhimpur, Dhubri, Nagaon, Dibrugarh, Kokrajhar and Kamrup) of Assam produced a PCR product of 399bp for all the root-knot nematode isolates. A representative of four different isolates from four districts viz., Jorhat, Lakhimpur, Nagaon and Kamrup were partially sequenced. Sequenced similarity of Mi isolates from four districts showed 89 per cent to 99 per cent homology. Results of molecular characterization using RAPD primers revealed that populations of root-knot nematode of nine districts of Assam formed three clusters with a bifurcation at 0.47 similarities. The first cluster had five isolates viz., Jorhat, Sibsagar, Kokrajhar, Kamrup and Dhubri. The second cluster comprised of three isolates viz., Golaghat, Lakhimpur and Dibrugarh, while Nagaon was found to be totally different from other isolates. Study on the morphological variations among the populations of Meloidogyne incognita from nine districts of Assam exhibited variations only in the tail shape, while other morphological characters showed similarities among the populations. Tail shape of second stage juveniles of M. incognita collected from Golaghat, Kokrajhar, Nagaon and Sibsagar district was similar in shape. Likewise, tail shape of second stage juvenile of Dibrugarh, Jorhat and Lakhimpur population showed similarity but, Dhubri and Kamrup population showed variation from other populations. No variation on perineal pattern was observed in size and shape of perineal pattern of M. incognita collected from nine districts of Assam. Studies on morphometric variations (body length, stylet length, lip height, lip width, MB, a, b, b´, c and c´) among the populations of M. incognita from nine districts of Assam showed no distinct variations in the major characters, except in MB value. MB value of Kamrup population was higher (61.79) than other populations. Present investigation on effect of temperature on the biology (embryogenesis, penetration and multiplication) of root-knot nematode, Meloidogyne incognita revealed that M. incognita completed embryogenesis within 4.468 days at 28°C, which was found to be the favorable temperature for embryogenesis than 31°C (5.168 days) and ambient temperature (7.645 days). Penetration was not affected by temperature but, migration and post-penetration inside the root tissue were influenced by temperature. At 27±1°C, M. incognita second stage juvenile took 5 days to reach stele region followed by 31±1°C and 23±1°C (7 days) while, at 21±1°C, it took 10 days. Multiplication of M. incognita was greatly affected by temperature. Maximum number of galls per root system (119.6), number of egg masses per root system (275.2), number of eggs per egg mass (343.6), final nematode population (1335.2) and reproduction factor of nematodes (2.67) was observed at 27±1°C followed by 31±1°C, 23±1°C and 21±1°C.