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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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ThesisItem Open Access FUNCTIONAL ANALYSIS OF NUTRACEUTICAL PROPERTIES FOR DIFFERENT TYPES OF RICE(AAU, Jorhat, 2021) Gogoi, Smrita; Dutta Deka, SharmilaTraditional rice genotypes are endowed naturally with a wide range of nutraceutical properties and thus constitutes to be a potential functional food for nutritional security. The present investigation was undertaken with the objectives to study the diversity of different rice genotypes for yield and yield attributes with varying nutritional components especially iron and zinc. The differential expression of the genes for anthocyanin biosynthesis in relation to iron and zinc content in rice grain and genome wide association study to identify significant marker trait associations for yield and grain quality in rice germplasm collection was also done in the present study. A group of 204 rice genotypes comprising of traditional rice including ahu, Sali, bao, aromatic and glutinous genotypes along with a few high yielding released varieties and high zinc breeding lines developed in IRRI, Philippines were evaluated during Sali 2019-20 in augmented block design and observations were taken for quantitative and qualitative traits as per DUS guideline including important phytochemicals using standard procedure. Out of these, Disang and Dimrou, were recorded as earliest flowering and maturing genotypes, whereas Gopinath and Horu Jahinga possess more number of productive tiller per plant. Joha (Meghalaya) was recorded for high spikelet fertility, whereas Horu Jahinga, Jengoni, and Kajoli chokuwa were recorded high seed yield per plant. To authenticate the common perception of high nutritional value of traditional pigmented rice genotypes, phytochemical analysis were done for 30 genotypes which were selected based on high Fe, Zn content and aleurone colour. Pigmented rice genotypes; Tulashi bora, Ikhojoy, Aus joria and Jengoni were recorded high phytochemical content along with higher Fe and Zn. Jengoni was also recorded high grain yield per plant along with biological yield per plant. Hence, Jengoni along with Tulashi bora, Ikhojoy and Aus joria are identified as promising genotypes for future nutritional breeding combining with good yield. A high significant correlation was also observed between total phenolics and antioxidant activity with total anthocyanin activity. For expression analysis, 5 genotypes were selected including one check i.e. Bahadur, on the basis of high Fe and Zn content and aleurone colour. Seven gene specific primers were designed to study the expression profile in selected genotypes by double delta CT method. The results indicated that there is no direct relationship between anthocyanin and micronutrient content and thus warrants possibility of involvement of different genes other than the tested ones. Genotyping by 6 sequencing using SNP marker was done for the present set of 204 diverse rice germplasm by outsourcing and marker and trait associations for yield and grain quality in rice germplasm collection for 20 traits was investigated. Out of the 20 traits and 75,309 SNPs analyzed, 30 SNPs showed significant associations with plant height, stem length, spikelet fertility and 1000-grain weight and Zn content. Among the 30 SNPs only 18 SNPs were encoded and co-located with major candidate genes. Moreover, for spikelet fertility and 1000-grain weight, four novel QTLs were detected, which were mapped on chromosome 5 and 7 at 12336034bp and 9597295bp position, respectively for spikelet fertility and on chromosome 7 and 12 at position 13808132bp and 6012015bp for 1000-grain weight. Further characterization and validation of the novel QTLs may lead to the identification of new candidate genes for these traits.ThesisItem Open Access Genetics of Brinjal (Solanum melongena L) for Adaptation in Summer Season(AAU, Jorhat, 2022) Imsong, Bendangla; Sarma, AkashiThe present investigation was carried out using twenty three genotypes of brinjal collected from Horticultural Research Station, Kahikuchi, Department of Horticulture, AAU, Jorhat, Tezpur and Mizoram. The experiment was conducted at Horticulture Research Farm, Assam Agricultural University, Jorhat. In the first growing season, the twenty three genotypes were assessed and based on the performance of genotypes and initial plant data, eight lines and three testers were selected and crossed in line x tester mating design to obtain twenty four cross combinations. The parental lines, their cross combinations and a check variety was sown in the second season.The analyses of variance revealed significant variation at genotypic level among the twenty three genotypes for all the sixteen characters except one i.e, fruit length. Between the replication, it was observed that there was significant variation in respect of leaf blade length. The characters, plant spread, fruit circumference, number of fruits per plant, fruit weight, fruit volume and fruit yield per plant had high estimates of both GCV and PCV. High heritability coupled with high genetic advance was observed for the traits, plant spread, fruit circumference, number of fruits per plant, fruit weight, fruit volume and fruit yield per plant. The fruit yield per plant had a significant positive genotypic and phenotypic correlation with plant height, plant spread, number of primary branches per plant, leaf blade length, fruit pedicel length, fruit circumference, number of fruits per plant and fruit weight. There were characters which manifested to be negatively correlated with yield indicating which were days to first flowering, days to 50% flowering, days to first fruiting and days to 50% fruiting. The highest positive direct effect was of days to first flowering (6.064). The genotypic residual effect was observed to be 0.122. The twenty three genotypes were grouped into 5 clusters with cluster I having the maximum number with twelve genotypes. Cluster IV that the highest intra cluster and the inter cluster D2 value was observed to be maximum between cluster III and cluster IV. The highest contribution per cent was manifested for days to 50% flowering. The qualitative characters studied in total were fourteen. From the analysis of variance for line x tester mating design, it was found that the parents, crosses and parents vs crosses exhibited highly significant difference. The analysis of 58 variance of combining ability showed significant difference for the lines, tester and line x tester interaction. Except for the character, plant height, all the other characters exhibited significant difference for line x tester interaction. The estimates of SCA variance were higher than GCA variance which resulted in ratio of σ2GCA to σ2SCA less than one. The proportional contribution of line x tester interaction to total variance was more than the lines and testers. The proportional contribution of lines to total variance was more than testers and line x tester interaction in respect of fruit length and total phenol. Amongst parents, the line Longai Purple Long was observed to be the highest yielder, desirable lowest content of solasodine and exhibited earliness in days to first flowering, days to 50% flowering, days to first fruiting and days to 50% fruiting whereas the tester, KB4 manifested desirable mean for eleven characters which were leaf blade length, days to first flowering, days to 50% flowering, days to first fruiting, days to 50% fruiting, fruit length, fruit weight, fruit volume, fruit yield per plant, phenol content and crude protein. The cross Green Streaked x Balijana showed desirable mean for six traits among all the crosses which were leaf blade width, days to first flowering, days to 50% flowering, days to first fruiting, days to 50% fruiting and solasodine content. The highest yielder was M2 x KB4 among all the twenty four crosses. In regard to good general combining ability of the parents, the line Longai Long was observed to exhibit both positive and negative effects in desired direction for eleven traits. The lines found to be good general combiners for yield were Longai Purple Oblong and Barpeta and for earliness besides Long Long. The cross, HRS4 x Balijana was found to have the maximum number of positive and negative sca effects in favourable trend. The hybrid M2 x KB4 manifested highest average heterosis for fruit yield per plant followed by Longai Long x KB4 and HRS4 x Balijana. The cross M2 x KB4 produced the highest yield.ThesisItem Open 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.ThesisItem Open Access GENETICS OF DROUGHT TOLERANCE IN RICE (Oryza sativa L.)(2019-11) Devi, Laishram Monalisha; Sarma, DebojitThe 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).ThesisItem Open Access MOLECULAR MARKER BASED HETEROTIC GROUPING OF ASSAM RICE (Oryza sativa L.)(AAU, Jorhat, 2020-01) Kumar, Praveen; Sarma, DebojitIn the present investigation, a group of 55 upland rice genotypes along with 5 maintainer lines of wild abortive cytoplasmic male sterility (WA CMS) were characterized using 83 SSR markers. Eleven parents from diverse clusters of SSR based diversity analysis were selected for crossing in a diallel fashion following Model 1 Method II of Griffing (1956). The resultant hybrids were evaluated in RBD under two N-fertilizer doses (40 and 60 kg ha-1) for 19 different traits. Fifty-three polymorphic markers detected a total of 133 alleles across the 60 rice genotypes with an average of 2.5 alleles per polymorphic marker. Polymorphic information content (PIC) values ranged from 0.032 (RM318) to 0.655 (RM293). The marker RM293 having the highest PIC value of 0.655 was adjudged the most appropriate marker to discriminate among the rice genotypes. The genetic divergence study grouped the 60 rice genotypes into 3 major clusters using Unweighted Neighbour-Joining (UNJ) method. Analysis of variance for the parents and their hybrids revealed significant differences for all the traits. The mean squares due to treatment were significant for all the traits. Treatment*Environment mean squares were also highly significant for all the traits except for seedling establishment. Grain yield recorded positive and significant correlations with culm height, productive tillers, biological yield and harvest index, indicating that selection based on these traits would ultimately improve seed yield. The GCA and SCA variances were highly significant for all the traits, suggesting the involvement of both additive as well as non-additive gene action in their inheritance. The SCA variance was higher than the GCA variance for all the traits, suggesting the predominance of non-additive gene action, which was also supported by the low magnitude of σ2gca/σ2sca ratios. Suryamukhi, Lal Aus, Mayamoti, IR 58025B, IR 68888B, IR 68897B, IR 79156B and Lachit were good general combiners for grain yield per plant. The crosses namely IR68888B*Luit, Lal Aus*IR80555B, Suryamukhi*Lachit, Mayamoti*IR79156B, Mayamoti*Lachit, IR58025B*IR6888B, IR58025B*IR68897B, IR58025B*IR79156B, IR58025B*IR80555B, IR68897B*Lachit, Lal Aus*IR68888B, Lal Aus*IR68897B, Lal Aus*IR79156B, Lal Aus*Lachit, Lal Aus*Luit, Bor Mekohi Dhan*Mayamoti, Bor Mekohi Dhan *IR58025B, Suryamukhi* Bor Mekohi Dhan, Suryamukhi *IR58025B and Suryamukhi*IR79156B revealed significant desirable SCA effects for grain yield per plant along with other important traits. The crosses viz., IR68888B*Lal Aus, IR68888B*Lachit, IR79197B* Bor Mekohi Dhan, IR79156B*Lal Aus, IR79156B*Lachit, IR80555B*Bor Mekohi Dhan, Suryamukhi*Mayamoti, IR68888B*IR79156B, Lal Aus*Lachit and Bor Mekohi Dhan*Luit were common in both SCA- and SSR diversity based heterotic groups. The genetic distance estimates did not correlate with the SCA effects and heterosis for grain yield. The yield-SCA effects showed positive and significant correlation with grain yield, mid-parent, better-parent and standard-parent heterosis. Thus, prediction of hybrid performance based on SCA-based clustering of the genotypes would enable identification of superior crosses before field testing. The best hybrids viz., Mayamoti*Lachit (G2*G3), IR80555B*Lal Aus (G1*G2) and Luit*IR68888B (G1*G3) belonged to inter-heterotic groups. These heterotic crosses could be exploited in a rice hybrid breeding programme to obtain high-yielding hybrids. The results of the present study, however, provided no concrete evidence to support the effectiveness of random SSR markers for separation of rice genotypes into heterotic groups.ThesisItem Open Access CHARACTERIZATION OF DEEPWATER RICE OF ASSAM FOR AGRO-MORPHOLOGICAL AND BIOCHEMICAL TRAITS(AAU, Jorhat, 2020-08) Das, Yater; Sharma, K. K.Deep water rice is one of the world’s most fascinating as well as challenging climate resilient crop which has elongation, kneeing and nodal tillering ability. They are rich in vital micronutrient like Fe and Zn content, have anti-oxidant property but low yielder about 1.0 to 1.5 tonnes per ha which is mainly due to its plant types, stresses encountered during growth period, low genetic potential and lack of effective breeding techniques. Hence, a study on the morphological, biochemical and biotechnological traits was done to characterize, to understand the extent of diversity and for identification of valuable traits and promising genotypes required for deepwater rice improvement. The experiment was conducted under direct seeded and transplanted conditions during 2017-18 and 25 selected genotypes from both the environment were transplanted during 2018-19. Morphological characterization consisted of 46 qualitative and 16 quantitative traits which consists of 13 monomorphic, 14 dimorphic, 11 trimorphic and 24 polymorphic traits indicating their potential for varietal characterization and distinctiveness. Kneeing ability was observed in 90 genotypes and elongation ability ranged from 3.15 cm to 132.75 cm. Maximum genotypes exhibited procumbent nature, presence of secondary branching, well exerted panicle, phenol reaction of lemma, white stigma colour, short grain length, medium amylose content and chalkiness, high gelatinization temperature, long stem length, medium test weight, red kernel colour, broad grain width and medium grain shape. Though maximum genotypes have semi-erect culm attitude but are lodging susceptible at maturity. The quantitative traits revealed significant difference under both the conditions and for 25 selected genotypes. The mean for the biochemical traits viz., protein content (7.99 %), starch content (71.38 %), amylose content (21.27 %), amylopectin (78.73%), Fe content (16.79 mg kg-1) and Zn content (23.19 mg kg-1) showed rich nutritional status of DWR which may serve as donor for future quality breeding programs. High magnitude of both GCV and PCV was recorded for elongation ability, leaf breadth and EBT per hill under direct seeded condition whereas culm diameter, EBT per hill and KL:KB showed under transplanted condition. High heritability coupled with high estimate of genetic advance as percent of mean was recorded for EBT per hill, leaf length, leaf breadth, GL:GB, kernel breadth, KL:KB, culm diameter and for yield per plant under both direct seeded and transplanted condition. Protein, iron and zinc content also showed high heritability coupled with high estimate of genetic advance as percent of mean. Study of correlation coefficients revealed that yield per plant is positively correlated with EBT per hill, leaf length, leaf breadth, panicle length, grains per panicle, 100-grain weight, culm diameter, kernel breadth, protein content, number of filled grain per panicle and harvest index which indicated the importance of these traits in DWR improvement, moreover, zinc content showed positive correlation with iron content. EBT per hill, leaf length, leaf breadth, grains per panicle, 100-grain weight, kernel length, culm diameter and protein content had positive direct effect and significant positive correlation with yield per plant, indicating the true relationship among these traits. D2 analysis grouped 115 germplasms into 14, 5 and 19 clusters under direct seeded, transplanted and for physico- chemical traits respectively. The maximum inter-cluster distance was observed between cluster XI and XIII, cluster II and VI, and cluster XVI and XVIII while highest intra-cluster distance in cluster VIII, Cluster III and cluster XIII under direct seeded, transplanted and for physico- chemical traits respectively. Under both the conditions, days to 50 per cent flowering, 100-grain weight and grain breadth were found the contributor of genetic divergence which prove their importance in DWR breeding programme while Zn and Fe content contributed highest towards genetic divergence for physico- chemical traits. Three markers Sub1BC2, RM 316 and RM 8300 were found to be highly scorable and informative among the thirteen markers used for screening of DWR for submergence tolerance. Three genotypes viz., Badam Bao, Betu Bao-1 and Happy Bao showed the similar banding pattern as to Ranjit–Sub1 on compiling the result of these three markers which showed that these lines are may be the haplotypes of Sub1 QTL which must be validated by sequencing of Sub1 QTL.ThesisItem Open 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.ThesisItem Open Access MORPHOLOGICAL, BIOCHEMICAL AND MOLECULAR CHARACTERIZATION OF BHUT JOLOKIA (Capsicum chinense Jacq.) OF NORTH EAST INDIA(AAU, Jorhat, 2018-01) Goswami Phukan, Rumjhum; Borgohain, RupamThe 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.ThesisItem Open Access GENETIC STUDIES ON HEAT TOLERANT TOMATO (Lycopersicon esculentum Mill.) AND THEIR ANDROGENIC RESPONSE TO ANTHER CULTURE(AAU, Jorhat, 2014) Das, Reecha T.; Talukdar, PranabThe present investigation comprising of parental, F1, F2 and backcross generations of four tomato crosses viz. H7997 x CLN1621E, H7997 x BL337, H7997 x Nagcarlan and H7997 x CLN2366A was conducted at Assam Agricultural University, Jorhat with three objectives- 1) to study the pattern of inheritance and gene effects for yield, yield attributing and physiological characters related to heat tolerance. 2) to study the genotype environment interaction of the generations of the crosses and 3) to study the androgenic ability of tomato lines and their hybrids. The experiment was conducted in three different environments during the offseason and one in the rabi season. Significant variation was revealed among the crosses and generations for almost all the yield and yield attributing and physiological characters. The pooled analysis of variance indicated profound influence of the environments on the expression of all the characters except for days from flowering to fruit setting. High estimates of genotypic coefficient of variation (GCV) was observed for fruit yield per plant and relative stress injury in most of the environments. High heritability with high genetic advance was observed for number of fruiting clusters per plant, fruit yield per plant, relative stress injury, pollen viability percentage and chlorophyll stability index in two or more environments. Out of the four crosses, high fruit yield per plant was recorded for three crosses viz. H7997 x CLN1621E, H7997 x Nagcarlan and H7997 x CLN2366A all were at par. Pooled analysis of variance for stability revealed significance of linear genotype - environment interaction for all the characters except for days from flowering to fruit setting and number of fruiting clusters per plant. Non linear genotype-environment interaction found to be significant for all the characters except for days from flowering to fruit setting, flower shed percent, chlorophyll stability index and relative stress injury. In the present investigation, the F1 of crosses H7997 x CLN1621E, H7997 x Nagcarlan and H7997 x CLN2366A and F2 of cross H7997 x CLN2366A and B2 of cross H7997 x BL 337 average stability for fruit yield per plant. Correlation studies between stability parameters of yield with yield attributing and physiological characters and also amongst them revealed that stability of and number of fruits per plant among the yield attributing characters and membrane stability percentage and chlorophyll stability index among the physiological characters together with plasticity of rest of the characters was mainly responsible for yield stability in heat tolerant tomato. F1 of cross H7997 x CLN1621E exhibited consistently significant mid parent heterosis over environments for most of the characters including fruit yield per plant. This was followed by crosses H7997 x Nagcarlan and H7997 x CLN2366A. Inheritance studies indicated failure of additive-dominance model for all yield and yield attributing and physiological characters In general, additive effect was found to be predominant in most of the yield attributing and physiological characters in almost all the crosses in two to three environments. Response of the components of generation mean to environmental fluctuations revealed that additive gene effect was consistent for number of primary branches per plant, days from flowering to fruit setting, number of fruiting clusters per plant and number of fruits per plant. Among physiological characters additive effects were found to be consistent for senescence index, lipid peroxidation and relative stress injury. Both additive and non additive gene effect was found to be consistent for fruit yield per plant. Duplicate epistasis was observed for most of the characters under study including fruit yield per plant. However, complementary epistasis was observed for days to fruit maturity, number of fruiting clusters per plant and fruit yield per plant in one to two crosses in individual environments. Androgenic studies revealed that H7997 x CLN 2366A and H7997 x Nagcarlan were the most responsive genotypes with high callus induction percentage and callus diameter. Thus there is also scope for development of doubled haploids in these two crosses.