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Subject: Nematology × Author: Jena, Rupak × 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.