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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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2018 - 20194
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Subject: Plant Breeding × End date: 2019 × Start date: 2016 × Type: Thesis × Thesis Type: Ph.D ×
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Now showing 1 - 4 of 4
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    ThesisItemOpen Access
    GENETIC ENHANCEMENT IN TOMATO (Solanum lycopercicum L.) FOR RESISTANCE TO BACTERIAL WILT AND QUALITY THROUGH INTRA AND INTER-SPECIFIC HYBRIDIZATION
    (2019-07) Das, S. Yasmin; Borkakaty, R. P.
    Tomato is the most important solanaceous vegetable crop. To estimate its production under the challenges of bacterial wilt disease, it is important to identify potential genotypes with resistance to bacterial wilt disease of tomato. To achieve this goal an investigation on ‘Genetic enhancement in tomato for resistance to bacterial wilt and quality through intra and inter-specific hybridization’ had been taken up to study the performance of few genotypes, their heterosis and combining ability and nature of gene action. The experiment was carried out at the experimental field of Horticultural Research Station, Assam Agricultural University, Kahikuchi, Guwahati during rabi seasons of 2015-16, 2016-17 and 2017-18. Evaluation of six parents, fifteen F1, fifteen F2, three BC1 and three BC2 generations of tomato revealed existence of sufficient variability and interaction effects in the genotypes. Combining ability analysis in Diallel mating design without reciprocals involving six diverse tomato cultivars/lines, viz., Singimari Local, Megha, Solan Lalima, Arka Abha, Arka Alok and Kon bilahi and their 15 cross combinations in bacterial wilt sick plots revealed importance of both additive and dominance effects. Two parents, Singimari Local and Kon Bilahi were identified as good general combiner. Ten cross combinations out of total fifteen combinations exhibited high estimates of specific combining ability for different desirable traits. Among them the crosses which merit special consideration were Singimari Local x Solan Lalima for yield per plant(g), harvest duration and bacterial wilt survival (% ); Singimari Local x Kon Bilahi for number of fruits per plant(g) and bacterial wilt survival (%) ; Solan Lalima x Kon Bilahi for number of fruits per plant, harvest duration, pH of pulp and bacterial wilt survival (%); Arka Abha x Arka Alok for harvest duration ,pH of pulp, fruit weight(g), number of primary branches per plant and yield per plant (g); Megha x Kon Bilahi for days to first picking, days to maturity, pericarp thickness(mm), TSS (° Brix) and bacterial wilt survival (%) could effectively be used to exploit heterosis in bringing about desired genetic improvement. Besides, the crosses showing desirable SCA for yield per plant (g) and bacterial wilt survival (%) but without significant heterosis were Arka Alok x Kon Bilahi, Megha x Arka Alok, Singimari Local x Arka Abha and Arka Abha x Kon Bilahi. These crosses could be ideal for further selection to bring them into homozygous genetically improved lines. Generation mean analysis was carried out in three crosses viz. Singimari Local x Megha, Singimari Local x Kon Bilahi and Megha x Kon Bilahi involving six generations (P1, P2, F1, F2, BC1 and BC2). The individual scaling tests were used to test the adequacy of additive dominance model. The gene effects were estimated using three parameter model (Joint Scaling Test) suggested by Cavalli (1952) and six parameter model suggested by Haymen (1958). The analysis of variance among different generations of different crosses revealed significant variation for all the eighteen characters indicating considerable variability in the material studied. All the characters except productive flower retention (%) in cross Singimari Local x Megha recorded significance for at least one of the four individual scaling tests in all the 3 crosses. With respect to interaction effects, all the characters except productive flower retention (%) in cross Singimari Local x Megha, exhibited significant interaction effect for one or more epistatic interactions i.e.[i], [j] or [l] in all the three crosses studied. It is evident that for all the morpho-physiological and yield attributing traits, fruit quality traits and bacterial wilt survival(%) additive, dominance and interaction effects were present indicating the complex inheritance of the traits under study. Further enhancement of the genotypes identified in this study will pave the way for the development of high yielding tomato variety with resistance to bacterial wilt disease.
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    ThesisItemOpen Access
    GENETICS OF DROUGHT TOLERANCE IN RICE (Oryza sativa L.)
    (2019-11) Devi, Laishram Monalisha; Sarma, Debojit
    The present investigation was carried out at Instructional-Cum-Research Farm of Assam Agricultural University, Jorhat with the objectives - (i) To assess genetic diversity for drought tolerance in rice and (ii) To study the combining ability and gene action. We evaluated 46 rice genotypes in water sufficient non-stress and water-deficit stress conditions during Ahu season of 2018 in PVC pipes. Evaluation of the 6-parent diallel crosses was carried out during Ahu 2019 in plastic tubs. The phenotypic evaluation revealed significant variation for all the characters. Leaf rolling (LR) and drought recovery (DR) had a significant correlation with root traits only, positive with root length and negative with root dry matter and root-shoot ratio. Based on the lowest average LR plus DR score of unity, Basantabahar, Haru Bengunigootia, Lewly, Basmoti Red, Banglami, Ikhojoi, Dimrou, Lachit, Disang and Inglongkiri possessed tolerance to drought stress (7-8% soil moisture content) both at vegetative stage up to 3 weeks and reproductive stage up to 1 week. Root-shoot ratio, root dry weight, proline content, root length, productive tillers, grain yield, grains per panicle and biomass yield registered a high magnitude of PCV and GCV estimates. High heritability coupled with high genetic advance for 1000-grain weights, proline content, grains per panicle, root dry weight, days to first panicle emergence, days to 50% flowering, root-shoot ratio, biomass yield per plant, root length, grain yield per plant, productive tillers per plant, harvest index and shoot length implicating the role of additive gene action and scope of simple selection for these traits. D2 statistics grouped the genotypes into 14 clusters with the highest inter-cluster distance between cluster V-XIII and V-XII. Thousand-grain weights contributed the maximum (74.69%) to the genetic divergence among the genotypes followed by grains per panicle (9.76), proline content (3.29%), root dry weight (3.09%) and grain yield per plant (2.71%). At the molecular level, we detected a total of 86 alleles by using 34 pairs of SSR primers with an average of 2.53 per marker. The Jaccard’s coefficient of similarity ranged from 0.200 to 0.944, with an average of 0.360, suggesting diverse nature of the genotypes. The diallel analysis revealed the significance of both GCA and SCA variances for all the characters in both non-stress and stress environments, indicating the importance of additive and non-additive gene action in their expression. SCA variance was higher than GCA variance for most of the characters except pollen sterility in both the conditions and harvest index in non-stress condition alone. Simple selection would confer rapid improvement of pollen sterility in both the conditions. Among the parents, the good general combiners were IR 64, IR 36, Tamdao and Inglongkiri for early flowering and early maturity; Banglami and Sahbhagi Dhan for low pollen sterility; IR 64, IR 36 and Sahbhagi Dhan for reduced plant height; Banglami and Sahbhagi Dhan for high productive tillers per plant; Sahbhagi Dhan and Banglami for longer panicle with heavier grain weights; Banglami, Inglongkiri and Tamdao for harvest index in both the conditions; Sahbhagi Dhan, Inglongkiri and Banglami for grains per panicle; IR 64, Sahbhagi Dhan and Banglami for biological yield in stress condition. The cross combinations namely, Sahbhagi Dhan/Inglongkiri and Banglami/IR 64 in non-stress condition and Sahbhagi Dhan/Banglami, Sahbhagi Dhan/IR 64, Banglami/Tamdao, IR 36/IR 64, Inglongkiri/Tamdao in stress condition exhibited significant positive yield-SCA effects along with desirable GCA of parents and SCA for other characters. Hayman’s genetic analysis indicated partial to complete adequacy of the additive-dominance model for all the characters in both the conditions. The component of dominance variance was predominant for almost all the characters with mostly overdominance expression of genes demanding a more prudent breeding exercise for genetic manipulation of these traits such as heterosis breeding. The narrow-sense heritability estimates were moderate to high for pollen sterility, plant height, panicle length and harvest index in both the conditions. Partial dominance for pollen sterility in both the conditions suggested its worth for fairly dependable selection. The study also indicated a similar genetic interpretation of the characters with the approaches of Griffing (1956) and Hayman (1954a, 1954b).
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    ThesisItemOpen Access
    Genetics of adaptive traits in rice (Oryza sativa L.) under aerobic condition
    (AAU, Jorhat, 2018) Ojah, Hrishikesh; Talukdar, P.
    An investigation on genetic improvement of rice had been taken up to study the performance of few genotypes, their heterosis and combining ability, character association and nature of gene action under aerobic condition. The experiment was carried out at the experimental field of Sarat Chandra Sinha College of Agriculture, Assam Agricultural University, Dhubri during 2015 and 2016 spanning over four seasons. Evaluation of fifteen rice genotypes comprising ten traditional cultivars and five high yielding varieties both in aerobic and irrigated lowland situations revealed sufficient variability and interaction of the genotypes with the environment. Combining ability analysis in Line x Tester design involving 10 lines of traditional upland genotypes and 5 testers of HYV, revealed importance of both additive and dominance effects. Three lines (Banglami, Nagina 22 and Tamdao) and three testers (Luit, IR 36 and Gopinath) were identified as good general combiner, while six crosses were identified with specific combining ability (SCA) effect for higher number of characters. Days to anthesis, days to maturity, plant height and height growth rate were found to have significant SCA and heterobeltiosis in favourable direction in higher number of crosses. Four crosses viz. Aus Jaria/ IR 36, Kasalath/IR 36, Dimrow/KMJ-13A-6-1-2 and Tamdao/IR36 recorded heterobeltiosis for maximum number of characters (4 each). Significant correlation was observed among mean, heterobeltiosis and SCA for most of the characters. Genetic parameters estimated in Line x Tester experiment revealed that number of productive tillers, plant height and proline content were highly amenable for improvement, whereas, high genetic variability existed for proline content, root shoot ratio, number of productive tillers and grain yield. Significant correlation with grain yield existed for 3 characters (number of productive tillers, spikelet fertility and chlorophyll content) apart from sufficient inter correlation among various adaptive characters. Path coefficient analysis revealed the highest positive direct effect of root weight (1.65) on grain yield, followed by spikelet fertility (1.43) and plant height (0.92). Harvest index (1.25) through spikelet fertility exerted the highest indirect effect, followed by panicle harvest index (1.07) through spikelet fertility. Generation mean analysis was carried out in three selected crosses viz. Banglami/Luit, Koimurali/Luit and Guni/Gopinath, involving six generations (P¬1, P2, F1, F2, BC1 and BC2). The individual scaling tests were used to test the adequacy of additive dominance model. The gene effects were estimated using three parameter model (joint scaling test) suggested by Cavalli (1952) and six parameter model suggested by Haymen (1958). The analysis of variance among different generations of different crosses revealed significant variation for most of the characters indicating considerable variability in the material studied. All the characters except height growth rate in cross II, recorded significance for at least one of the four individual scaling tests in all the 3 crosses. Estimation of different gene effects and their interactions revealed significant positive additive effect for plant height and height growth rate in all the three crosses. Preponderance of dominance effect in the expression of height growth rate, spikelet fertility, grain yield, harvest index, root weight and root shoot ratio was evident from the significant positive dominance (h) effect in all the three crosses. With respect to interaction effects, all the characters except height growth rate in cross II, exhibited significant interaction effect for one or more epistatic interactions i.e.[i], [j] or [l] in all the three crosses studied. It is evident that for all the yield and other adaptive traits, additive, dominance and interaction effects were present indicating the complex inheritance of the traits under aerobic condition. On the basis of estimation of various parameters under 3 different sets of experiment over 4 seasons, plant height, shoot weight, number of productive tillers, spikelet fertility, proline content, days to antheis and days to maturity were identified as important adaptive traits to be considered for further improvement of aerobic rice.
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    ThesisItemOpen Access
    MORPHOLOGICAL, BIOCHEMICAL AND MOLECULAR CHARACTERIZATION OF BHUT JOLOKIA (Capsicum chinense Jacq.) OF NORTH EAST INDIA
    (AAU, Jorhat, 2018-01) Goswami Phukan, Rumjhum; Borgohain, Rupam
    The Northeast region of India including Assam is considered as original home of the world’s hottest chilli, Bhut Jolokia (Capsicum chinense). In recent years several varietal types of Bhut Jolokia exhibiting considerable variation in plant, fruit and pungency traits has been observed in the farmers’ field. Therefore, an attempt was made to characterise a few accessions of Bhut Jolokia at morphological, biochemical and DNA level to elucidate the extent and nature of genetic variation. Expression profile of few pungency related genes in Bhut Jolokia was also attempted to detect their possible allelic variation in the Bhut Jolokia accessions. A set of 20 Bhut Jolokia (C. chinense) accessions, three Capsicum annum accessions (Krishna Jolokia, bell pepper and Cherry type) and one C. frutescens accession (Mem Jolokia) were analysed using 35 morphological and biochemical characters. Analysis of variance (ANOVA) for quantitative characters revealed considerable genetic variation among the genotypes. Variability and path analysis identified fruits/ plant, fresh fruit weight and photosynthetic rate as important parameters for improvement. Principal component analysis (PCA) isolated eight principal components each comprising of several characters and accounting for 78.36% of the total variability among the accessions. Several seedling, fruit and physiological characters contributed towards total variability of the population. The PCA plots failed to distinguish Bhut Jolokia accessions into distinct clusters despite sufficient diversity among them. Sixteen characters were identified based on their contribution to PCA, as minimum morphological descriptors for preliminary characterization of Bhut Jolokia genotypes. Population structure analysis separated the accessions into Bhut Jolokia and non Bhut Jolokia populations. Majority of the genotypes had > 80% membership coefficients for each specific group. Only Acc-21 (Cherry type) showed genomic admixture indicating gene flow between Bhut Jolokia and non Bhut Jolokia populations. The genetic diversity studies conducted with the use of 51 SSR markers and 40 gene specific markers exhibited a low inbreeding coefficient (FIS=0.147), thereby indicating high heterozygosity among the genotypes. The overall FST value of 0.432 indicated large genetic differentiation between the populations. AMOVA performed between all lines grouped according to structure indicated 43% variation between populations, 20% variation among individuals within populations and 37% variation was due to variation within individuals. Gene expression analysis of 6 genes of the capsaicinoid biosynthetic pathway exhibited that the Capsaicinoid pathway genes studied showed significantly higher expression in Bhut Jolokia (C. chinense) genotypes while very low expression levels were observed in Bell pepper genotype (low-pungent). Amongst these candidate genes, AMT, Pun1, PAL from Phenylpropanoid pathway and BCAT, KAS and ACL from Fatty acid biosynthetic pathway were found to be up-regulated in pungent genotypes especially in the breaker stage (25-35 DAF) of the fruit development. The variations in the pungency level were found to be associated with changes in the expression level of the genes of the biosynthetic pathway.