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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 Biochemical, histopathological and molecular characterization of sesamum phyllody disease in Assam(2021) Gogoi, Shankar Hemanta; Nath, P. DebThe field of phytoplasma diseases witnessed a new height of systematic study and research works throughout the world. An effort was made for biochemical, histopathological and molecular characterization of the sesamum phyllody disease. Sixteen (16) different alternate hosts were identified by molecular technique and out of that 9 were characterized. Three different groups of phytoplasma viz., aster yellows (16SrI), clover proliferation (16SrVI) and stolbur phytoplasma (16Sr XII) were identified to be associated with the phytoplasma alternate host samples. By using iPhyClassifier tool Brinjal phytoplasma isolate was grouped into the subgroup level 16SrVI-D. Exitinus indicus was detected for phytoplasma presence; characterization was done and it was found that it may play a new role for sesamum phyllody phytoplasma transmission. Ten (10) sesamum cultivars were grown in the field and pot conditions to observe the disease reactions and the cultivars were found moderately resistant (MR) to moderately susceptible (MS). The sesamum phyllody disease was successfully transmitted from infected to healthy sesamum plants by graft transmission (80%). Membrane-bound, phytoplasma-like bodies were detected in Transmission electron microscopy. Total chlorophyll content was reduced by 41.02 per cent in severely infected plants, while in mildly infected plant it was reduced by 28.20 per cent. Ratio between chlorophyll “a” and chlorophyll “b” progressively reduced as a result of infection. The ratio was 1.02 in healthy plants, while it was 1.01 and 0.96 in case of mild infection and severe infection, respectively. Phyllody disease considerably increased the dry matter content in the infected plant. Increase in dry matter content was 12.41 per cent and 19.85 per cent in mildly infected and severely infected plants, respectively. However, no considerable difference in moisture content was observed in both mildly and severely infected plants compared to the healthy ones. Phyllody disease decreased the total nitrogen as well as protein content. The reduction in protein content was 8.50 per cent in mildly infected leaves and 13.29 per cent in severely infected leaves. Phenol content was increased as disease advanced from milder to severe symptoms stage from 2.24 mg/g to 2.68 mg/g, respectively, as compared to healthy leaves i.e., 1.85 mg/g. Molecular characterization of Sesamum phyllody phytoplasma was done from all the agro-climatic zones of Assam and all the phytoplasma isolates were grouped into 16SrI-B. Restriction Fragment Length Analysis (RFLP) was done with three restriction enzymes viz., BamHI, EcoRI and RsaI. Sequence analysis, iPhyClassifier and the comparison between virtual and actual RFLP pattern revealed that there is no genetic difference among the Sesamum phyllody phytoplasma isolates of Assam.ThesisItem Open Access SYNTHESIS OF NANOPARTICLE FROM BIORESOURCES FOR MANAGEMENT OF BLAST DISEASES OF RICE(2021) Kaman, Pranjal Kumar; Bhattacharyya, AshokDevelopment of reliable and eco-friendly process for synthesis of metallic nanoparticle is an important steps in the field of nanotechnology. An effort was made for biosynthesis of gold nanoparticles from bioresources like microbes Aspergillus niger, Metarhizium anisopliae, Lecanicillium lecannii, Purpeurocillium lilacinus and botanicals like Ocimum gratissimum, Acorus calamus, Aloe barbadensis and Azadirachta indica. Chloroauric acid was added as precursor for the synthesis of gold nanoparticles. Study on in vitro efficacy of biosynthesized gold nanoparticle from bioresources was tested at hundred percent concentration against Magnaporthe grisea and effective source was found to be Metarhizium anisopliae and Ocimum gratissimum. Further efficacy of biosynthesized gold nanoparticle from Metarhizium anisopliae and Ocimum gratissimum. was tested against Magnaporthe grisea at three different concentrations (50, 100 and 150ppm) comparison was made with Tryclozole @ 600 ppm. The result showed that the gold nanoparticles at 150 ppm significantly inhibit the mycelia growth of the pathogens as compared to the Tryclozole @ 600 ppm. The effective biosynthesized gold nanoparticles was characterized by UV-Vis spectrophotometer, Dynamic Light Scattering (DLS), Fourier transform infrared spectrometer (FTIR), Zeta Sizer and Transmission Electron Microscope (TEM). Formation of gold nanoparticles were confirmed by UV-VIS spectroscopy study with absorption peaks at 550 nm. FTIR study showed that synthesized gold nanoparticle has all the required functional groups like OH, N-H, C-H and COO-. Study on surface properties of nanoparticles by using zetasizer resulted that gold nanoparticle from Metarhizium anisopliae was found to be negative and were stable in nature with zeta potential value of -20.7 mV. DLS analysis showed that the average size of the biosynthesized gold nanoparticles is 32.54 nm with polydispersity index of 0.560. TEM study showed that shape of the biosynthesized nanoparticle is from triangular to quasihedral and the size range from 9-54nm. Again, a pot experiment was conducted for studying its effect on morphophysiology as well as soil physico chemical and biological properties by different methods of application like seedling dip treatment, foliar spray and soil application. A positive effect was found on the morphology, soil physico chemical and biological properties when rice seedling was treated as seedling dip treatmen + foliar spray + Soil application @ 150ppm.ThesisItem Open Access Role of beneficial bacteria on yield of Calocybe indica and Pleurotus species and management of contaminants in mushroom beds(2022) Gogoi, Monuj; Sarmah, D. K.Milky (Calocybe indica) and oyster mushroom (Pleurotus spp.) is the mostimportant cultivated mushroom in India and a very less works has been conducted to identified the role of bacteria on growth and yield of mushrooms. Therefore, the aim of present study was to investigate the effective bacterial spp. isolated from cultivated mushroom substrates and their role in mycelial growth, influence of primordia formation, pinhead and yield of mushrooms. Six bacterial cultures were isolated from the growth substrates of Pleurotus spp. and casing soil of Calocybe indica. Out of six bacterial isolates, 3 isolates were observed positive effect on growth and development of mushroom species. The other isolates were inhibiting the mycelial growth of Pleurotus florida, Pleurotus djamor and Calocybe indica. In in vitro experiment was observed that addition of effective single and combine bacterial isolates with pure culture of C. indica, P. florida and P. djamor enhanced the pinhead formation in Petriplate conditions as compared to control. In vitro cultivation of Pleuortus spp., single and combined application of MB1, MB2 and MB5 could enhanached the formation of pinhead, primordia and fruting body as well as increasing the yield of P. florida and P. djamor. In in vivo experiments, combined application of MB1, MB2 and MB5 (T7) isolates were found to be the best treatment to enhances the spawn run, early initiation of pinhead, formation of fruiting body and yield of C. indica and P. florida. In case of P. djamor experiments, the maximum growth and yield parameters were observed in spraying of MB1 @ 30 ml/bed (T1) followed by spraying of MB1, MB2 and MB5 @ 30 ml/bed (T7) to promote the growth and yield parameters of P. djamor over control. The bacterial isolates viz., MB1, MB2 and MB5 were recorded more or less inhibition against the mycelial growth of Trichoderma spp. in in vitro conditions. The maximum mycelial growth inhibition percent (55.44%) was observed in MB2 isolates over control. The highest natural incidence of green mould contamination was observed in all the mushroom species viz., C. indica, P. florida and P. djamor beds in control treatment (without inoculation of bacterial isolates) in in vivo conditions. Based on cultural, morphological, biochemical and molecular analysis, the bacterial isolates viz., MB1, MB2 and MB5 were identified as Pseudomonas flourescens (96.79% homology with KM206793.1), Bacillus cereus (98.01% homology with MG594014.1) and Alcaligenes faecalis (98.26% homology with KY608969.1) respectively. In another experiment, all the effective bacterial isolates were able to produce growth promoting 6 substances like siderophore and IAA.Nutrient contents viz., crude protein, crude fat, crude fiber, ash and carbohydrate of C. indica and P. florida were enhanced by combined addition of effective bacterial isolates to the cultivated substrates over uninoculated control. In the present investigation it was also observed that the combined inoculation of effective bacterial isolates viz., MB1, MB2 and MB5 increased the mineral contents (calcium, sodium, magnesium and potassium) of C. indica and P. florida. In case of P. djamor, mineral contents were maximum in T1 (spraying of MB1 @ 30 ml/bed) followed by T7 (spraying of MB1 + MB2 + MB5 @ 30 ml/bed) as compared to control (T8). The results of present experiments concluded that artificial addition of growth promoting bacterium in growing medium play a crucial role in the early colonization of substrates, initiation of fruting body, yield enhancement and management of green mould contamination of mushrooms.ThesisItem Open Access Development of mapping population and use of SSR markers for breeding disease resistance against Tomato leaf curl virus (ToLCV)(2021) Oladokun, John Oladeji; Nath, P. D.Tomato leaf curl disease (ToLCD) caused by the tomato leaf curl virus (ToLCV) has been a serious threat to tomato crops for decades and breeding genotypes resistant to ToLCD is a sustainable management option. An open field screening was conducted in an augmented design between 2018 and 2019 which was aimed at identifying resistance in 39 tomato genotypes, and developing mapping populations for genetic and inheritance trait analysis in the population. Symptoms associated with ToLCV were recorded, importantly leaf curls incidence alone accounted for 53% (in single infection). The highly resistant genotypes are EC164563, 171, EC520078-B, EC165690, IIHR 2904, H24, S. pimpinellifolium, IIHR 2871, IIHR 2862, EC157568, EC521067-B, and IIHR 2867 with incidence ranging between 8.3-18.2% ± 12.3. The S. pimpinellifolium was selected for further studies. There was a significant relationship between whitefly population × minimum temperature (r = -0.973, P=0.05), whitefly population × relative humidity (r = -0.996, P=0.05) and whitefly population × average disease incidence (r =0.996, P=0.05). Out of 60 symptomatic and asymptomatic bulked leaf samples tested by PCR with six different primers targeting different components of the genome, only 32 (53.3%) were confirmed to be ToLCV infected. The nucleotides of sequence Jorhat isolates of the DNA-β satellite component of ToLCV (accession number: MZ2962423, MZ2962424, MZ2962425) similarity identity falls between 99.4 to 99.5 % with ToLCBDB (accession number AJ542489) and a closed cluster with two ToLCBDB isolates (AJ542489 – tomato, MN985116 – country bean) in the phylogenetic tree. One hundred and twenty (120) SSR markers were screened for parental polymorphism check between Pusa Ruby (susceptible) and S. pimpinellifolium AAU2019 (resistant), only 11/120 were polymorphic while 109 /120 were monomorphic. In the cross of Pusa Ruby × S. pimpinellifolium AAU2019 and other generations F2 (self-pollinated F1), and B1F1 or BCs, developed and screened for ToLCV infection in the field, disease incidence was lowest in S. pimpinellifolium AAU2019 (7.3 %) followed by F2 (33.3%) but higher in Pusa Ruby (91.3%) when genetic control in S. pimpinellifolium AAU2019 was studied. Using a co-dominant marker (SSR 63), the inheritance and genetic analysis study of resistance to ToLCV in an interspecific cross (Pusa Ruby × S. pimpinellifolium AAU2019) in different mapping populations by SSR63 molecular marker revealed a monogenic recessive (best-fit ratios 3:1, 1:1) nature of ToLCV resistance. Progenies of F2, and B1F1 or BCs generations tested for ToLCV DNA varied in terms of the intensity on resolve in gel electrophoresis using the same DNA concentration and compared to Pusa Ruby with higher intensity and not in S. pimpinellifolium AAU2019. However, the type of resistance derived and inherited from S. pimpinellifolium AAU2019 is assumed to be controlled by a single gene in a recessive state and it is neither fixed nor dominant. This is based on the genotypic segregating pattern, responses of the generations developed to ToLCV infection. Hence, this study provides the potential of S. pimpinellifolium AAU2019 as an alternative breeding source for developing resistant cultivars against ToLCV.ThesisItem Open Access Elimination of the Potato Viruses from the Local Landraces through in Vitro Culture(2022) Phookan, Jutimala; Kalita, Manoj KumarThe present investigation on local landraces of potatoes from Assam was conducted to eliminate the viral infections. For this the local landraces were collected from different districts of Assam viz., Jorhat, Biswanath, Sonitpur, Barpeta, Dibrugarh and Kokrajhar. Different symptoms like puckering of leaves, cupping of leaves, leaf rolling, purple colouration on leaves, calico pattern, mosaic symptoms, crinkling of leaves, etc. were observed. It was observed that the landrace from Barpeta had the highest disease incidence of 62.22 per cent and the lowest incidence of 10.00 per cent was observed in Badami aloo collected from Kokrajhar. PCR analysis of the symptomatic samples showed the presence of different viruses like PVY, PLRV, PVM, PVX, PVS and AMV. The potato tubers were also subjected to PCR analysis and only PLRV was detected with the highest incidence in Barpeta landrace (75.00 %). The growth and yield attributing characters of the landraces collected were also recorded. Plant height was observed to be highest in the landrace of Dibrugarh with 43.36 cm. The highest number of branches was observed in Dibrugarh landrace. The weight of tubers per plant was observed to be highest in case of Dibrugarh landrace (383.48 g). In the in vitro studies, three types of explants (nodal segment, tuber eyes and apical meristem) with two types of media (MS and PM media) were used to conduct the experiment. Among the various hormonal combinations used for shooting, the best hormonal combination observed was 2 mg/ l GA3 + 4mg/ l NAA + 2 mg/ l BAP irrespective of the explant and media used in case of the parameters viz., time required for shooting, number of shoots developed and length of shoots. Similarly in case of rooting the best hormonal combination observed was 1.5 mg/ l IAA + 1.5 mg/ l GA3 + 1.5 mg/ l KIN irrespective of the explant and media used in case of the parameters viz., time required for rooting, number of roots developed and length of roots. The potato plantlets survived highest (86.67 %) when grown from tuber eyes whereas the disease incidence of PLRV was lowest (20.00 %) in case of plantlets grown from apical meristem. Further SAR chemicals were applied exogenously in the potato plants grown in field condition and it was observed that BTH applied at 1.5 mM had the highest reduction of incidence over control (87.03 %). The results of application of SAR chemicals were also supported by the biochemical analysis of DAB assay and PPO assay. On application of thermotherapy, no disease incidence was observed at 40 ⁰C for 2 hours 30 minutes where germination was 50 per cent.ThesisItem Open Access Molecular epidemiology of viral disease complex of Capsicum chinense Jacq. in North Eastern Region of India(2022) Khaba, Chingakham Inao; Nath, P. D.Viral disease complex of Capsicum chinense Jacq. were the major constraint facing by king chilli growers in North Eastern Region (NER) of India in recent decades. A total of 94 samples were collected from Assam (36), Arunachal Pradesh (12), Nagaland (10), Meghalaya (8) and Manipur (28). Both DNA & RNA were isolated and detected CMV, PVY, ChiLCV & GBNV. Peculiar symptoms of shoestring, vein banding, leaf puckering, leaf curl and leaf necrosis were observed. Moreover, unknown mix viral infection symptom like yellowing, stunted growth were also observed. Severe symptoms as well as highest vectors population were observed in Assam and lowest in Meghalaya. After PCR base detection, CMV has the highest per cent infection in NER of India (47.88%) followed by PVY (8.58%), ChiLCV (8.34%) and GBNV (4.55%). CMV was detected from all the five states of north east India. The highest disease incidence of CMV was observed in Manipur (53.57%) and lowest in Meghalaya (37.50%). PVY was detected from Assam and Manipur with an incidence of 26.31 and 16.66% respectively. ChiLCV and GBNV were detected from Assam only with an incidence of 26.31 and 16.66% respectively. With respect to altitude, CMV was more prevalent at the mid-altitude (200-800 m a.s.l.) with 54% and followed by low altitude (<200 m a.s.l.) with 48%. The lowest CMV prevalent was at the high altitude (>800 m a.s.l.) with 47%. Whitefly prevalence depending on altitude; at low altitudes (0–200 m), 35% of the plants sampled were colonized by more than five whiteflies and 38% of the plants no whiteflies were detected. Although 49% of the plants sampled at mid-altitude (200–800 m) were not colonized, 33% were colonized by one to five whiteflies, and the remaining 17% by more than five. At high altitudes (>800 m a.s.l), no whiteflies were detected on 92% of the plants. Those mix viral infection of king chilli leaves was done Next Generation Sequencing (NGS) in Illumina platform. A data of 3.75 GB was generated in which 66.2% of chilli genome were mapped. The unmapped read data was 1.4 GB. After Denovo assembly, 51.9 Mb was generated and subjected to BLAST in NCBI. A total of 27 different isolates of king chilly viruses were revealed and 6 viruses were novel in NER of India viz., Pepper cryptic virus, Pepper vein yellows virus, Tomato ringspot virus, Capsicum frutescens endornavirus, Alphaendorna virus and Pepper leafroll virus . The highest occurrence virus was pepper vein yellow virus (10/27) and followed by Pepper cryptic virus (6/27), Capsicum frutescens endornavirus (4/27) and Chilli veinal mottle virus (3/27) respectively. The single occurrence viruses were Tomato ringspot virusT , Potato virus Y, , Pepper leafroll virus and Alphaendorna virus . All the NGS viruses were ranged 87-100 % homology to NCBI database.ThesisItem Open Access Evaluation of aromatic rice genotypes against blast and its biointensive management under rainfed condition(AAU, Jorhat, 2021) KUMAR, BADANA MANOJ; Das, B. C.Rice blast caused by Pyricularia oryzae, has gained the status of major disease of rice, and it infects almost all the rice growing areas throughout the world. And it is predicted as a major disease in India and in the recent times, the disease has been observed to show an increasing trend in rice fields of Assam, and it causes yield losses varies from 1 to 100%. In the present study evaluation of aromatic rice varieties for resistance and susceptibility against blast was done and studied the effect of management strategies under field condition in Assam. Among the thirty varieties tested with artificial inoculation, none of the varieties shows highly resistance (ie., completely free from the disease) and highly susceptibility whereas, fourteen varieties showed resistant reaction, while five varieties showed moderately resistant, eight varieties showed moderately susceptibility and three varieties shows susceptibility reaction. Addition to that total genomic DNA was extracted from the blast culture were subjected to PCR assay using ITS 1 and ITS 4 primers. BLAST analysis of the samples showed the similarity percentage of 99-98% with the other isolates. Phylogenetic analysis was done with the help of Mega X software, it was found that the samples were closely related with Pyricularia oryzae Meghalaya isolate JX469384. Biochemical analysis was evaluated in both healthy and infected leaves of resistant and susceptible aromatic rice genotypes. The resistant entries possess a higher amount of phenols and lower amount of total proteins and total soluble sugars as compared to the susceptible one. After the infection the phenols content was increased in infected leaf as compared to the healthy one in all the entries whereas the total proteins and total soluble sugars were decreased in infected leaf as compared to the healthy one in all the entries. Among the different date of sowing, highest incidence of blast disease (30.35% and 32.81%) were recorded in crop showed on 13th July of 2019 and 2020 respectively. Whereas lowest incidence of blast disease (6.72% and 7.14%) were recorded in crop showed on 15th June of 2019 and 2020 respectively. Correlation studies on the influence of weather parameters on blast disease development revealed that maximum and minimum temperature, evening relative humidity, rainfall and rainy day were negatively correlated with disease development whereas, relative humidity morning and bright sun shine hours shows positive correlation with the disease development. Multiple regression analysis indicates that, by using max temperature, relative humidity evening and bright sun shine hours could predict the blast disease incidence up to 98% in future in that area. In vitro ABSTRACT evaluation of Botanical viz., Mustard oil cake (MOC) and compost materials viz., Farm yard Manure (FYM) and Vermi compost (VC) against blast revealed that MOC at 0.2% concentration showed highest inhibition of pathogen over control ie., 46.27% after 7th day followed by MOC at 0.1% shows 39.02% and VC at 0.2% concentration shows 36.67 % inhibition over control respectively. Among the three different bio agents ie., Trichoderma harzianum, T. viride and T. koningii, all of them showed significantly inhibition of the pathogen in vitro but higher percentage inhibition over control showed by T. harzianum, ie., 97.41%. In vivo condition, Seed treatment with Trichoderma harzianum amended with MOC (20%) + cow urine (5%) shows less percent disease incidence ie., 4.30% and 5.73% after 15 and 30 days after sowing in the nursery respectively. Whereas, in field condition, Trichoderma harzianum amended Extract of MOC at 20% concentration showed less percent disease incidence ie., 5.64 %, 9.85 % and 24.31 % and less percent disease severity ie., 3.74%, 7.96% and 9.67% after 45, 60, 75 days after showing respectively. Followed by Trichoderma harzianum amended Extract of MOC at 10% and Trichoderma harzianum amended Extract of VC at 20% concentration respectively.ThesisItem Open Access Diversity of bacteriophages infecting R alstonia solanacearum and their application as b io control agents(AAU, Jorhat, 2021-12) Barua, Parinda; Nath, P. D.Bacterial wilt caused by Ralstonia solanacearum is one of the most destructive plant diseases of the world that is very difficult to manage. Sustainable management of R. solanacearum using bacteriophages is one of the most promising yet unexplored areas of biological control in India. In the present study, 50 R. solanacearum isolates were collected from various bacterial wilt infected fields in 5 districts of Upper Brahmaputra Valley Zone (UBVZ) of Assam namely Golaghat, Jorhat and Sivsagar, Dibrugarh and Tinsukia from several crops like bhut jolokia, chilli, capsicum, tomato, brinjal, wild brinjal, potato and ginger. This was followed by isolation of seven lytic phages of R. solanacearum from soil from bhut jolokia fields of Jorhat, Assam. After six rounds of purification of the phages, the plaque morphology, phage titre and the multiplicity of infection (MOI) was determined where it was observed that phage RSP1 had the biggest plaque size (3.28 ± 0.40 nm) and phage RSP4 had the highest titre (1.2E+09 PFU/ml). The adsorption time, latent period, rise period as well as the burst size of the isolated phages was also determined. Physiochemical characterization of the phages revealed that the phages were stable from 4℃-50 ℃, a pH range of 4-9 and except RSP1; all other phages were stable 1% and 5% chloroform. Morphological classification using TEM revealed that all the phages had an icosahedral head with a very short non- contractile tail indicating that they may belong to either Podoviridae and/or Autographiviridae family of order Caudovirales. From the lysis dynamics curves of the individual phages, 3 phage cocktails were formed and cocktail-3 having all the seven phages gave the best results. Study on host range of the phages stated that all the phages were multi strain specific in nature and phage RSP4 had the highest host range. In vitro suppression of R. solanacearum in soil using phage cocktail-3 revealed that the cocktail was effective in managing R. solanacearum population in soil when used as a prophylactic manner. Finally, from the study on long term viability of phages at different storage temperatures it can be recommended that these seven phages could be stored in glycerol stocks at -45 ℃ or -20 ℃ and in SM buffer in +4 ℃ without losing viability for a year. Keywords: Bacteriophage, Ralstonia solanacearum, bacterial wilt, phage therapy.ThesisItem Open Access BIOPROSPECTING ACTINOBACTERIA OF ASSAM FOR SOME RICE DISEASE MANAGEMENT AND GROWTH PROMOTION(2020-01) Gogoi, Nripen Kumar; Bora, L.C.Actinobacteria, an important group of Gram positive bacteria are potent producers of wide variety of secondary metabolites with diverse biological activities including biocontrol and plant growth promotion abilities. The members of the genus Streptomyces are especially prolific as they alone constitute 50% of the total soil actinobacteria and 18% of all biologically active secondary metabolites(nearly 7600 out of 43,000) known so far. The present investigation was undertaken to explore potent actinobacterial strains to contain two major rice diseases viz. sheath blight (ShB) and bacterial leaf blight (BLB). Total seventy five isolates of actinobacteria were isolated and their morphological, biochemical and molecular characterization were carried out. Among twelve antagonistic actinobacterial isolates observed in vitro, isolate ‘Act 116’ and ‘Act 119’recorded the maximum inhibition of ShB pathogen Rhizoctonia solani and BLB pathogen Xanthomonas oryzae pv. oryzae by 66.7% and 26.3%, respectively. Scanning electron microscopy of these two isolates showed rectiflexible and retinaculiaperti type of polysporous spore chains. Molecular identification of ‘Act116’ and ‘Act 119’ done through 16S rRNA gene sequencing revealed the strains as Streptomyces corchorusii and S. sasae, respectively. The partial gene sequences of the two isolates were submitted to NCBI GenBank (GenBank No.KY393359.1 & GenBank No. MH988751.1). The pot culture and field experiments showed significant reduction of per cent disease index (PDI) of ShB and BLB of rice (cv. Mahsuri) in strain ‘Act 116’ and ‘Act 119’ treated plants. The application of actinobacteria ‘Act 116’ and ‘Act 119’ as seed treatment, root dip and foliar spray could reduce PDI of ShB and BLB to 24.6% and 30.8%, respectively over control (70.4 and 66.7 PDI, respectively). These combinations were also resulted in significant plant growth promotion. In field experiments, the microbial population increased in treated plots compared to control. Significant uptake of nitrogen, phosphorous and potash were observed in actinobacteria treated plots compared to control. The crude bioactive compounds extracted were analyzed through LCMS and revealed the possible presence of antibiotic compounds like Difloxacin, Dicloxacillin, Nystatin, Tetracycline and Doxycyline. Hence, it can be inferred from the present study that actinobacterial strains ‘Act 116’ and ‘Act 119’ have significant biocontrol potential against the two major rice diseases ShB and BLB, respectively and can be efficient candidates for management of other plant diseases also.
