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2020 - 20223
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Subject: Nematology × Start date: 2019 × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    EXPLORATION AND EVALUATION OF BIOPROTECTIVE RHIZOSPHERIC MICROORGANISMS AGAINST MELOIDOGYNE GRAMINICOLA
    (2022) Jena, Rupak; Choudhury, B. N.
    Eighteen bacterial strains and eleven fungal strains were isolated from rhizosphere of different crops like rice, okra, ash gourd, chili, beans, cucumber from diverse conditions and soil types in and around Jorhat. The biochemical characterization of the isolated bacterial strains disclosed that six bacterial isolates tested negative for KOH test while twelve tested positive. All the bacterial strains exhibited positivity for gelatin hydrolysis and catalase test. Seven bacteria showed positive while eleven showed negative reaction to citrate test. Morphological findings stated that six bacterial strains were gram positive while twelve stained negatively, fifteen bacteria were rod shaped, two were coccus and one diplococcus in shape and all the bacterial isolates exhibited motility. The study of in vitro efficacy of the twenty nine bacterial and fungal isolates tested against second stage juveniles of M. graminicola revealed that all the bacterial and fungal isolates potentially impacted the test organism and caused significant mortality over sterile water treatment. The promising bacterial and fungal isolates were identified as BSH8, BTS4, BTS5, BJA15, FJB 11 and FSH5. The best result on mortality was exhibited by BSH8 with 80.79% mortality over J2 of M. graminicola. The effective and promising bio agents were identified using the 16 S rRNA sequencing and the organisms were Bacillis subtils (BSH8), Bacillus velezensis (BTS4), Alcaligenes faecalis (BTS5), Rhizobium pusense (BJA15), Talaromyces allahabadensis (FSH5) and Trichoderma asperellum (FJB11). In the pot experiment seventeen treatments were formulated using five potential isolates (3 bacteria, 2 fungi) either alone or in various compatible combinations. All the treatments showed significant results over the untreated control. The isolates improved the overall plant biomass and reduced the nematode reproduction and final population over control. The combined application of B. subtilis as seedling root dip + B. velezensis as soil treatment + T. asperellum as soil treatment @ 1x108 cfu/ml exhibited the maximum impact on plant morphological parameters viz., root length, shoot length, fresh and dry weight of root and shoot and inhibited the nematode population by decreasing the number of galls, egg masses and eggs/egg masses. The next best treatment was seedling root dip with B. subtilis+ soil treatment with T. asperellum and seedling root dip with B. velezensis + soil treatment with T. asperellum @ 1x108 cfu/ml.
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    ThesisItemOpen Access
    Biomanagement of disease complex of Meloidogyne incognita and Fusarium oxysporum f.sp ciceri on chickpea (Cicer arientinum., Butler 1918)
    (2021) Roy, Pallabi; Borah, A.
    In the present study on the interaction of Meloidogyne incognita and Fusarium oxysporum f.sp ciceri on chickpea, the result indicated that dual inoculation treatments significantly decreased plant growth parameters over the treatment with M. incognita @1000 J2/kg soil and F. oxysporum @ 2% (w/w). The treatment with M. incognita @1000 J2/kg soil + F. oxysporum @ 2% (w/w) after 15 days of inoculation was statistically superior in decreasing the plant growth parameters of chickpea. However, number of galls, eggmasses, final nematode population was found maximum in single inoculation treatment than dual inoculation treatments. The highest number of galls, eggmasses, final nematode population were observed in the treatment with M. incognita @1000 J2/kg soil. The maximum disease incidence was recorded in the treatment with M. incognita @1000 J2/kg soil and F. oxysporum @ 2% (w/w) after 15 days of inoculation. Studies on the management of disease complex of Meloidogyne incognita and Fusarium oxysporum on chickpea with microbial consortia, vermicompost and Glomus fasiculatum alone or in combination under microplot condition showed that all the treatments differed significantly over untreated control in respect of increaseing plant growth parameters and yield of chickpea. The seed treatment with microbial consortia @ 5ml/l + soil application of vermicompost enriched microbial consortia @ 2t/ha + seed treatment with microbial consortia @ 5ml/l + soil application of Glomus fasciculatum spores/m2 was found to be most effective in increasing plant growth parameters, yield, N,P, and K content in soil. All the treatment significantly decreased the number of galls, eggmasses, nematode population and fungal population in soil and percent disease incidence. In the pilot field trial, conducted at farmers field with the best treatment combination found under microplot trial for the management of disease complex of Meloidogyne incognita and Fusarium oxysporum on chickpea showed that the seed treatment with microbial consortia @ 5ml/l + soil application of vermicompost enriched microbial consortia @ 2t/ha + seed treatment with microbial consortia @ 5ml/l + soil application of Glomus fasciculatum spores/m2 effective in increasing plant growth characters, yield and reducing in number of galls, final nematode population in soil and percent disease incidence over untreated control.
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    ThesisItemOpen Access
    ISOLATION, CHARACTERIZATION AND EVALUATION OF ENDOPHYTIC BACTERIA AGAINST ROOT-KNOT NEMATODES
    (AAU, Jorhat, 2020-09) Basumatary, Binita; Das, Debanand
    Fifteen endophytic bacteria were isolated from leaves and stems of Solanum lycopersicum and S pimpinellifolium. Morphological characterization of these endophytes revealed that 6 bacteria were gram positive and 9 bacteria were gram negative, 10 bacteria were rod shaped, 3 were coccus shaped and 2 were diplococcus in shape. All 15 bacteria were motile in nature. Biochemical characterization of the isolated endophytes revealed that 9 bacteria showed positive reaction to KOH test while, 6 were negative to KOH test, 11 bacteria showed positive reaction to Citrate and 4 were negative to citrate test. All the 15 bacteria were positive for Gelatine hydrolysis and Catalase test. Six endophytic bacteria showed positive reaction and 9 showed negative reactions for Starch hydrolysis test. Four potential isolates were structurally analysed by using scanning electron microscope and revealed that the length and breadth of BETLI, BETL2, BETL4 and BETS2 were 701.70nm × 348.30nm, 954.l0 nm x 303.10 nm, 984.10nm × 332.90nm and 1422.00nm × 742.00 nm, respectively. Five endophytic bacteria showing potentiality against root-knot nematode were identified by using 16S rRNA, and they were Microbacterium arborescens (BETLI), Bacillus marisflavi (BETL2), Bacillus altitudinis (BETL4), Exigobacterium indicum (BETS2) and Bacillus marisflavi (BETL6). Study on in vitro efficacy of bacterial endophytes against second stage juvenile of root-knot nematode (J2) revealed that all the isolates had the potentiality to significantly increase the mortality of nematodes however, the isolate BETL2 showed the best result on mortality rate (81.47%) of 2 stage juvenile (J2) of Meloidogyne incognita, followed by isolates BETL4 (81.43%) and BETLI (79.07%) Dose-response models were used to determine the concentration of bacterial culture filtrates required to kill 50 per cent juveniles of M. incognita. Four potential bacterial endophytes were tested with different methods of applications (seed treatment, seedling root dip treatment, soil application and their combinations) in pot condition against root-knot nematodes in tomato. All the tested endophytic bacteria significantly increased the plant growth parameters of tomato and reduced the nematode multiplication than untreated control. However, maximum increase in plant growth parameters and decrease in number of galls, egg mass and nematode population in soil was observed in combined application of seed treatment + root dip treatment + soil treatment of Bacillus marisflavi (BETL2) @ 1x 10 cfu/ml of crop.