PG Thesis
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Item Mitigating water stress in summer rice using beneficial root endophytic fungus Piriformospora indica(Department of Agronomy, College of Agriculture, Vellayani, 2021) Koya Madhuri, Mani; Ameena, MThe study entitled ‘Mitigating water stress in summer rice using beneficial root endophytic fungus Piriformospora indica’ was undertaken at College of Agriculture, Vellayani during 2019 - 2021. The objective of the study was to assess the performance of P. indica colonized rice under different levels of moisture stress during summer. The field experiment was laid out in randomized block design with 2 x 3 x 2 treatments, replicated thrice in the low land paddy fields during February to May 2021, using variety Prathyasa. The treatments included colonizing with P. indica [p1- P. indica colonized rice and p2- non-colonized rice(control)], three irrigation intervals[i1- 30 mm CPE (cumulative pan evaporation), i2- 35 mm CPE and i3- 40mm CPE] and two irrigation depths(d1- to a depth of 1.5 cm and d2- to a depth of 3 cm). P. indica colonized/ non-colonized rice seedlings raised in trays were transplanted at 14 days after sowing at 15 cm x 10 cm and uniformly irrigated till 10 days after transplanting (DAT). The crop was raised as per the KAU package of practices recommendation for short duration rice (KAU, 2016). The results of the study revealed that colonization and irrigation to 3 cm depth improved the growth and growth attributes viz., plant height, tiller number m-2 , leaf area index and dry matter production of summer rice. Colonization with P.indica significantly influenced the number of tillers m-2 with 10.64, 16 and 15.69 per cent increase in tiller production at 30, 45 and 60 DAT respectively, compared to non-colonized plants. Colonized plants irrigated at 30 mm CPE to a depth of 3 cm evinced the maximum leaf area index (4.54) at 60 DAT and dry matter production (4559.26 kg ha-1 ) at harvest. Yield attributes and yield of rice were significantly affected by P. indica colonization, irrigation interval and depth of irrigation. Superior number of productive tillers m-2 (222.84), filled grains per panicle (81.11) and the lowest sterility percentage (13.37) were recorded with colonization. Colonized plants irrigated at 30 mm CPE to a depth of 3 cm produced significantly superior productive tillers m-2 (275.00), filled grains per panicle (111.33) and the lowest sterility percentage (8.80). Among second order interactions, p1i1d2 produced significantly superior grain yield (2698.56 kg ha-1 ) and straw yield (2848.13kg ha-1 ). P. indica colonization, irrigation interval and depth of irrigation had significant effect on root parameters of rice at all stages of observation. P. indica colonized plants showed significantly superior rooting depth at all stages. Colonized rice plants irrigated at 35 mm CPE 157 to a depth of 3 cm revealed superior rooting depth viz., 19.4, 29.86 and 30.00 cm and average root length of 23.36, 34.87 and 36.20 cm at 30, 60 DAT and harvest respectively. Significantly superior root volume and root dry weight at 30, 45, 60 DAT and harvest respectively were recorded in colonized plants irrigated at 30 mm CPE to a depth of 3 cm. Among the physiological parameters studied, proline content declined in the order of decreasing CPE, 40 mm >35 mm > 30 mm. P. indica colonized plants irrigated at 40 mm CPE to a depth of 1.5 cm produced significantly greater proline (115.33 and 106.00 μmole g-1 at panicle initiation and flowering respectively). Colonized rice plants at 30 mm CPE to a depth of 3 cm observed the maximum relative leaf water content, cell membrane stability and chlorophyll stability index at panicle initiation and flowering respectively. P x I x D remained significant with the highest water use efficiency (WUE) of 3.47 kg ha-1mm-1 for P. indica colonized plants irrigated at 30 mm CPE to a depth of 3 cm. P. indica, irrigation interval and depth of irrigation could significantly influence the available nitrogen, phosphorus and potassium status of soil after experiment. Colonized plants irrigated at 40 mm CPE to a depth of 1.5 cm resulted in significantly superior available phosphorus (179.93 kg ha-1 ). Considering the economics, P. indica colonized plants irrigated at 30 mm CPE to a depth of 3 cm brought about the highest gross income (₹ 88951 ha-1 ), net income (₹ 30351 ha-1 ) and B: C ratio (1.51). Based on the above findings, it could be inferred that rice plants colonized with P. indica significantly enhanced the growth and yield attributes, root biomass, nutrient uptake and WUE, irrespective of interval and depth of irrigation.Yield and WUE of P. indica colonized plants subjected to severe stress, were observed to be equivalent to those of non-colonized plants under moderate stress. Colonization resulted in saving of 30 mm water or 3 irrigations and could help rice to combat drought stress by enhanced root biomass, nutrient uptake and water use efficiency during summer.Item Growth promotion in chilli on inoculation with pseudomonas fluorescens and piriformosporaa(Department of Agricultural Microbiology, College of Agriculture,Vellayani, 2019) Nandana, M S; Anith, K NThe study entitled “Growth promotion in chilli (Capsicum annuum L.) on inoculation with Pseudomonas fluorescens and Piriformospora indica” was undertaken during 2017-2019, in the Department of Agricultural Microbiology, College of Agriculture, Vellayani, Thiruvananthapuram, with the objective to assess the compatibility of the root endophytic fungus Piriformospora indica and two Pseudomonas fluorescens strains, and to evaluate their effect on growth promotion in chilli variety Vellayani Athulya. The Pseudomonad strains used were Pseudomonas fluorescens PN026 and Pseudomonas fluorescens AMB8. Experiments comprised both in vitro and in vivo studies. For in vitro study a dual culture plate assay was done in potato dextrose agar (PDA) and coconut water agar (CWA) with the fungal and bacterial endophytes to evaluate the direct antagonism. Both Pseudomonas fluorescens PN026 and Pseudomonas fluorescens AMB8 showed antagonism to the root endophyte Piriformospora indica in PDA whereas in CWA, Pseudomonas fluorescens PN026 did not show any antagonistic effect and Pseudomonas fluorescens AMB8 showed a reduced antagonism to Piriformospora indica compaired to that in PDA. Indirect antagonism was evaluated through agar well diffusion method and paper disc diffusion method using culture filtrate of the bacterial strains and the culture filtrate from both the bacterial strains showed antagonism against Piriformospora indica in which the maximum zone of inhibition was observed in culture filtrate of Pseudomonas fluorescens AMB8. A Co-culture experiment involving P.indica and Pseudomonas strains using a single fermentation system was attempted in two different media; potato dextrose broth (PDB) and autoclaved coconut water (ACW). The flasks were incubated under agitation for 48 h and the population of the bacteria was determined at 24 h intervals by dilution plating in Kings B agar medium and it was observed that, when 10 day old cultures of the fungus in ACW and PDB were inoculated with the bacteria, ACW supported the growth of the bacteria similarly to fungus free ACW and KB medium. Co-cultivation in PDB led to a decline in bacterial population and the autoclaved coconut water can be suggested as a better medium for coculturing of P. indica and Pseudomonas fluorescens strains. A pot culture experiment was undertaken to study the effect of the different treatments on growth promotion of chilli. The experiment was laid out in CRD with six treatments and three replications and observation was taken in 15 days. The treatments comprised fungal and bacterial endophytes along with combinations of both fungal and bacterial endophytes and an uninoculated control. Different parameters like plant height, number of leaves, number of branches, number of fruits/plant, fresh fruit yield, fresh shoot weight, dry shoot weight, fresh root weight, dry root weight, days to flowering, days to fruit set and percentage root colonisation by Piriformospora indica were evaluated. Maximum plant height was recorded in the treatment with mixed inoculation of Piriformospora indica and Pseudomonas fluorescens PN026 without any significance in statistical data. A significantly increasing trend was observed in number of leaves with mixed inoculation of Piriformospora indica and Pseudomonas fluorescens PN026 from 45th day after transplanting and it was statistically on par with the treatment consisting of Piriformospora indica alone. Number of branches were found to be higher with mixed inoculation of Pirifomospora indica and Pseudomonas fluorescens PN026. There was no significant difference in the fresh weight and dry weight of shoot, whereas the fresh and dry weight of root (21.13 g and 8.26g respectively) were significantly higher in the plants treated with P. indica along with Pseudomonas fluorescens PN026. Number of fruits per plant (10.25/plant) and fresh fruit yield per plant (37.95g/plant) were recorded significantly higher with mixed inoculation of Piriformospora indica and Pseudomonas fluorescens PN026. The in vivo study disclosed that plants treated with Piriformospora indica along with Pseudomonas fluorescens PN026 were found to perform better than all other treatments. The mixed inoculation of Pseudomonas fluorescens AMB8 and P. indica had no additional advantage in plant growth in chilli. Piriformospora indica was able to successfully colonize in the plant roots applied with the bacterial endophyte. The present study revealed that plant growth promoting rhizobacteria, Pseudomonas fluorescens PN026 can be used along with Piriformospora indica, the root endophyte, for enhancing plant growth in chilli.Item Management of bacterial wilt disease of tomato by the root endophytic fungus piriformospora indica, rhizobacteria and bacterial endophytes(Department of Agricultural Microbiology, College of Agriculture, Vellayani,Thiruvananthapuram, 2018) Athira, S; Anith, K NThe study entitled “Management of bacterial wilt disease of tomato by the root endophytic fungus Piriformospora indica, rhizobacteria and bacterial endophytes” was conducted during 2016-2018 at Department of Agricultural Microbiology, College of Agriculture, Vellayani with the objective of assessing the potential of root endophytic fungus Piriformospora indica, plant growth-promoting rhizobacteria and bacterial endophytes in suppressing bacterial wilt incidence in tomato. The bacterial wilt pathogen, Ralstonia solanacearum was isolated from infected tomato plants on Semi selective medium from South Africa (SMSA). Koch’s postulates were proved by artificial inoculation of tomato seedlings. A functional relationship between population and optical density of the broth culture was worked out and was used for determining the inoculum density for challenge inoculation in the biocontrol experiment. In vitro antagonistic interaction between the bioagents and the pathogen was worked out both by direct and indirect assays. In all direct assays which involved cross streak plating, agar plug diffusion technique, disc diffusion and spot on lawn method, it was found that Bacillus amyloliquefaciens VLY24, Bacillus velezensis PCSE10 and Streptomyces leeuwenhoekii KBT004 exhibited antagonism against Ralstonia solanacearum. Indirect antagonism was checked by agar well diffusion and disc diffusion methods using culture filtrate. Out of the eight bacterial bioagents tested, only two i.e., Bacillus velezensis PCSE10 and Bacillus amyloliquefaciensVLY24 had inhibitory effect on the pathogen. Dual culture plate assay on PDA has shown that three bacterial bioagents, Rhizobium radiobacter PCRE10, Bacillus megaterium NAT001 and Streptomyces leeuwenhoekii KBT004 were compatible with Piriformospora indica. However, when the compatible bacteria were co-cultured in a single fermentor system along with Piriformospora indica it was observed that Bacillus megaterium NAT001 failed to grow along with the fungal endophyte. Suppression of bacterial wilt incidence by the individual and combined application of bacterial bioagents and fungal endophytes were tested with the wilt susceptible tomato variety Naveen (Indo-American hybrid seeds Pvt. Ltd, Bengaluru) and the moderately tolerant KAU variety Vellayani Vijay. Bioagents were applied during the nursery production of seedlings and the 21 days old seedlings were transplanted to pots filled with unsterile garden soil. Challenge inoculation with the pathogen was done five days after transplanting by drenching the pots with 10 ml each of the bacterial suspension (107cfu/ml). The disease incidence was scored at weekly intervals for 21 days. When the bioagents were tested individually for the suppression of bacterial wilt incidence in the hybrid variety Naveen, maximum disease suppression was observed in plants treated with Rhizobium radiobacter PCRE10 (15 percent) after 21 days. The disease suppressive ability of Bacillus velezensis PCSE10 (25 percent) was also significantly superior to all other treatments. Selection of bacterial bioagents for combined application with Piriformospora indica was done based on compatibility with the fungal endophyte and inhibitory action against Ralstonia solanacearum. Combined application of the fungal endophyte and Bacillus amyloliquefaciens VLY24 suppressed the wilt incidence to the highest extent (40 percent). When bacterial wilt suppression in Vellayani Vijay was tested by the individual application of bacterial bioagents, maximum disease suppression was recorded in plants treated with Streptomyces leeuwenhoekii KBT004 (30 percent), when observed 21 days after challenge inoculation. The combination of Piriformospora indica with Rhizobium radiobacter PCRE10 (50 percent) and Bacillus velezensis PCSE10 (50 percent) showed significantly lower disease incidence compared to the rest of the treatments. In the plant growth promotion experiment done with the variety Vellayani Vijay in the nursery stage, maximum plant height was observed in plants treated with Rhizobium radiobacter PCRE10 (14.49cm). However, those plants treated with Bacillus pumilus VLY17 had the highest number of leaves per plant (4.58). Combined inoculation of Piriformospora indica and Bacillus amyloliquefaciens VLY24 resulted in improved shoot fresh weight (2.08 g per plant) which was on a par with the plants treated with Bacillus velezensis PCSE10 (1.95 g plant-1). However, shoot weight on dry weight basis was the maximum for plants treated with Bacillus velezensis PCSE10 (122.55 mg plant-1) which was at par with those treated with combination of Piriformospora indica and Bacillus amyloliquefaciens VLY24 (104.78 mg plant-1). The present study revealed that biological management of bacterial wilt in tomato could be a feasible strategy under controlled conditions. The same has to be validated under field conditions before making any recommendations.Item Evaluation of systemic acquired resistance and induced systemic resistance on the suppression of foliar blight disease of amaranthus (Amaranthus tricolor L.)(Department of Plant Biotechnology, College of Agriculture, Vellayani, 2017) Athira Babu, B M; Anith, K N